Dual Language Ut Materi Rev 00 Plus Cover

NDT TRAINING PROGRAM

ULTRASONIC METHOD (DUAL LANGUAGE)

ASNT Continuing Education In Nondestructive Testing

The American Society for Nondestructive Testing

UT Lecture Guide Page 1 of 111

Table of Content Page

Lesson 1 Basic Application of Ultrasonic .....................................................................

2

Lesson 2 Ultrasonic Principle..........................................................................................

5

Lesson 3 Ultrasonic Equipment......................................................................................

11

Lesson 4 Mode of Ultrasonic Wave travel ...................................................................

19

Lesson 5 Couplant and Ultrasonic Sound Energy ......................................................

27

Lesson 6 Attenuation, Acoustic Impendance and Resonance ..............................

34

Lesson 7 Displaying Ultrasonic Indication....................................................................

40

Lesson 8 Ultrasonic Transduser and Standard Reference Blocks.............................

48

Lesson 9 Immersion Inspection......................................................................................

58

Lesson 10 Ultrasonic Contact testing .............................................................................

65

Lesson 11 Application of Contact Testing ....................................................................

75

Lesson 12 Nonrelevant Ultrasonic Indications ..............................................................

83

Lesson 13 Type of Discontinuities that can be detected by Ultrasonic ...................

89

Lesson 14 Indentification and Comparison of Diskontinuities ....................................

96

Attachment.........................................................................................................................

97

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LESSON 1 BASIC APPLICATIONS OF ULTRASONIC’S

DASAR PENERAPAN ULTRASONIC

Ultrasonic is a versatile inspection technique; it is used to test a variety of both metallic and nonmetallic products such as welds, forgings, castings, sheet, tubing, plastics and ceramics. Ultrasonic has an advantage of detecting subsurface discontinuities with access to only one side of the specimen.

Ultrasonic adalah suatu teknik pemeriksaan serbaguna; yang digunakan untuk uji berbagai macam produk baik metalik maupun produk nonmetallic seperti lasan, tempaan, tuangan, sheet, tubing, plastik dan keramik. Ultrasonik mempunyai suatu keuntungan mendeteksi cacat-cacat dibawah permukaan dengan akses hanya pada satu sisi spesimen.

The objective of ultrasonic testing is to ensure Tujuan pengujian ultrasonik adalah untuk memastikan reliabilitas produk dengan cara: product reliability by means of: 1. Obtaining information related to 1. Mendapatkan Informasi yang berhubungan discontinuities. dengan cacat. 2. Disclosing the nature of the discontinuity 2. Memperlihatkan sifat alami cacat tanpa without impairing the usefulness of the part. merusak kegunaan dari bagian benda. 3. Separating acceptable and unacceptable 3. Memisahkan material yang dapat diterima dan materials in accordance with predetermined tidak dapat diterima menurut standard yang standards. telah ditentukan. Training and Certification It is important that the technician and supervisor be qualified in the ultrasonic method before the technique is used and test results evaluated. The American Society for nondestructive testing recommends the use of their document “Recommended practice no. SNT-TC-1A”

Pelatihan dan Sertifikasi Adalah penting bahwa teknisi dan penyelia berkwalifikasi didalam metoda ultrasonik sebelum teknik digunakan dan hasil uji deievaluasi.

To comply with this document the employer must establish a “Written practice” which describes in detail how the technician will be trained, examined and certified.

ASNT (American Society for nondestructive testing) merekomendasikan penggunaan dokumen mereka " Recommended practice no. SNT-TC-1A" Dokumen ini menyediakan Pedoman yang diperlukan perusahaan untuk mengkualifikasi dan mensertifikasi yang baik kepada teknisi NDT didalam semua metode. Untuk memenuhi dokumen ini perusahaan harus menetapkan suatu "Pedoman (kebiasaan) tertulis" yang menguraikan secara detil bagaimana teknisi akan dilatih, diuji dan disertifikasi.

The student is advised to study the current edition of SNT-TC-1A to determine the recommended initial number of hours of classroom instruction and months of experience necessary to be certified as an ultrasonic testing technician.

Siswa disarankan mempelajari SNT-TC-1A edisi terbaru untuk menentukan jumlah jam pertama dalam mengikuti pelajaran di kelas, dan jumlah bulan pengalaman yang direkomendasikan dan diperlukan untuk disertifikasi sebagai teknisi uji ultrasonik.

Certification of NDT personnel is the responsibility of the employer and is usually at three levels. LEVEL I Performs specific calibrations, specific tests, and specific evaluation according to written instructions. LEVEL II Set up and calibrate equipment and interpret and evaluate results with respect to codes, standards and specification. Must be able

Sertifikasi personil NDT adalah tanggung jawab perusahaan dan umumnya ada tiga tingkatan.

This document provides the employer with the necessary guide lines to properly qualify and certify the NDT Technician in all methods.

Rev. 00

LEVEL I : melaksanakan kalibrasi khusus, pengujian khusus dan evaluasi khusus menurut instruksi tertulis. LEVEL II : set up dan kalibrasi alat, interpretasi dan evaluasi hasil pengujian mengacu pada codes, standards dan spesifikasi. Harus Prepared by Arif-010308

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to prepare written instructions and report test results. LEVEL III Responsible for establishing techniques, interpreting codes, and designating the test method and technique to be used. Must have a practical background in the technology and be familiar with other commonly used methods of NDT.

mampumenyiapkan instruksi-instruksi tertulis dan laporan hasil pengujian. LEVEL III : bertanggung jawab dalam menetapkan teknik, interpretasi codes dan mendesain teknik dan metode pengujian yang digunakan. Harus memiliki latar belakang praktek di bidang teknik dan memahami metode NDT yang lain yang umum digunakan.

The SNT-TC-1A document recommends that Dokumen SNT-TC-1A merekomendasi bahwa Level I and Level II NDT technicians be teknisi NDT Level I dan Level II diuji dalam lingkup sebagai berikut : examined in the following areas: A. Ujian umum A. General examination B. Ujian spesifik B. Specific examination C. Ujian praktek C. Practical examination ASNT provides a service to the industry by providing Level III examinations in the basic and method areas. Because of the individual requirements of the many industries using NDT, the specific examination is still the responsibility of the employer. The following flow chart indicates the paths that can be taken to be certified according to the SNT-TC1A document.

Rev. 00

ASNT menyediakan suatu layanan ke dunia industry dengan menyediakan ujian Level III dalam lingkup dasar (basic) dan metode. Karena banyaknya persyaratan yang berbeda di dunia industry yang menggunakan NDT, ujian spesifik masih menjadi tanggung jawab perusahaan. Flow Chart berikut menunjukkan jalur karier (path) yang dapat diambil untuk disertifikasi menurut dokumen SNT-TC-1A.

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UT LESSON 1 QUIZ F

1. The selection of one test method over another is usually the decision of the Level I technician performing the test.

F

2. ASNT provides a service for examining Level I, 11 and Ill personnel In the General and Specific areas.

T

3. The responsibility of Issuing a certificate to the NDT technician Is always retained by the employer In compliance wlth the SNT-TC-1A document.

F

4. If the SNT-TC-1A document Is to be used as a recommended guideline, the "Written Practice" must be submitted to ASNT for approval.

T

5. If the SNT-TC-1A guidelines are followed, the Level Ill technician should have a knowledge of other commonly used methods of NDT even though certification is needed only In the ultrasonic area.

T

6. A Level I technician performing an ultrasonic test is permitted* to accept or reject the part provided that written instructions or procedures are given to him by a Level II or Level Ill. *(in accordance with SNT-TC-1A)

T

7. To comply with the guidelines of SNT-TC-1A, all three levels of technicians must take a "General", "Practical" and "Specific" test if examinations are used to determine certification.

T

8. The June 1980 Edition of SNT-TC-1A permits the employer to waive an examinatlon for Level Ill personnel provided that documentation is on file showing the technician's qualifications.

T

9. It is essential that every employer that uses the SNT-TC-1A document establish a "Written Practice."

T

10. If an employer does not have a Level Ill in his company, the services of an outside agency may be retained to perform these functions.

T

11. An advantage of ultrasonics is that it reveals internal discontinuities with access to only one side of the part being Inspected.

T

12. Ultrasonic inspection techniques can be used without impairing the future usefulness of the material.

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Lesson 2 ULTRASONIC PRINCIPLES

Prinsip – prinsip ultrasonic

In ultrasonic testing we use something called Dalam ultrasonic testing kita menggunakan “Ultrasonic Vibrations”. We must know two sesuatu yang disebut “ultrasonic fibration” . Kita harus mengenal dua fakta tentang fibrasi: facts about a vibration: 1. Vibrasi adalah gerakan mondar – mandir 1. A vibration is a back and forth movement. 2. Vibrasi adalah energi dalam bentuk 2. A vibration is energy in motion. gerakan A depression of a surface from its normal Depresi suatu permukaan dari posisi normalnya disebut “Pemindahan / Penggesaran” position is called a displacement.

Vibrations pass through a solid material as a Vibrasi melewati suatu materil yang padat succession of particle displacements. This can sebagai perpindahan / pergesaran partikel. be visualized as shown below: Kejadian ini dapat diperlihatkan sebagai berikut:

The structure of a material is actually many Struktur material kenyataannya terdiri dari partikel - partikel kecil yang banyak atau terdiri dari small particles or groups of atoms. kelompok – kelompok atom. These particles have normal or rest positions, Partikel – partikel ini mempunyai posisi normal and can be displaced from these positions by (istirahat). Dan dapat dipindahkan dari posisinya some force. When the force is removed, the oleh suatu gaya bilamana gaya dihilangkan, particles will tend to return to their original partikel akan cenderung kembali ke posisi semula (normal). positions. Energy is transmitted through a solid material Energi yang merambat melalui material padat by a series of small material displacements dengan seri suatu perpindahan material kecil dalam material tersebut. within the material. The transmission of ultrasonic vibrations through Perambatan vibrasi ultrasonic melalui suatu a material is related to the elastic properties of material berhubungan dengan sifat- sifat elastisitas material. the material. If you tap a metal surface, the surface moves Jika suatu permukaan metal diketuk /dipukul, permukaan bergerak kedalam dan menyebabkan inward, causing a displacement. perpindahan.

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Since the metal is elastic the surface will tend to move back to its original (rest) position. The surface will also move through the original position and move to a distance in the opposite direction. This complete sequence of movements is defined as a cycle.

Selagi material bersifat elastis, permukaan akan cenderung kembali ke posisi semula (normal). Permukaan juga akan bergerak melalui posisi normal dan bergerak ke suatu jarak maksimum dan dalam arah yang berlawanan. Urutan – urutan lengkap perpindahan didefinisikan sebagai suatu siklus.

The time required for something to move through one complete cycle is called the period. Example: if the swinging ball above moves over path ABCDE in one second, then the period of the cycle is one second. The number of cycles in a given period of time is called the frequency. Example: if the ball swings through three complete cycles in one second, then the frequency is 3 CPS (Cycles Per Second). If you strike a drum, it has a frequency that is low, approximately 50 CPS.

Waktu yang dibutuhkan untuk bergerak melewati suatu siklus disebut periode.

The top note on the piano has a higher frequency, approximately 4100 CPS. The unit of frequency used to denote one cycle per second is hertz (abbreviated Hz). One cycle per second (CPS) is equal to one hertz (Hz); 2 CPS = 2 Hz, etc. Sound travels in metal as well as in air. Sound is a vibration and has a range of frequencies. Man can only hear vibrations (sound) up to about 20,000 Hz. However, sound from an ultrasonic testing unit is about 5,000,000 Hz (5 Megahertz). Vibrations above the human hearing range are called ultrasonic vibrations. The two terms, sound and vibrations, as we will use them will mean the same thing. The best way to define sound is to say that it is a vibration that transmits energy by a series of small material displacements. Rev. 00

Contoh : Bilamana bola yang berayun melewati jalur ABCDE dalam satu detik, kemudian periode siklus dalam satu detik. Jumlah siklus dalam satu periode tertentu disebut “frekwensi” Contoh: Bilamana bola berayun melewati tiga siklus dalam satu detik, dan frekwensinya adalah 3 siklus per detik (CPS = cycles per second) Jika suatu drum dipukul, ia akan memiliki suatu frekwensi yang cukup rendah, kira-kira sekitar 50 CPS. Note tertinggi dari piano memiliki dari piano memiliki frekwensi yang tinggi kira – kira sekitar 4100 CPS. Satuan frekwensi dipakai untuk menunjukkan satu CPS adalah Hertz, (disingkat HZ) 1 CPS = 1 Hz 2 CPS = 2 Hz Suara bergerak dalam metal dan juga dalam udara suara adalah vibrasi dan memiliki suatu rentangan frekwensi. Manusia hanya dapat mendengar vibrasi (suara) sampai dengan 20.000 Hz (20 KHz) Bagaimanapun juga, suara dari peralatan ultrasonic kira – kira 5.000.000 HZ (5 MHZ) Vibrasi diatas kemampuan pendengaran manusia disebut vibrasi ultrasonic. Ada dua terminologi, yaitu suara dan vibrasi, selanjutnya dalam pelajaran ini akan dipergunakan dalam arti yang sama. Suara didefinisikan sebagai suatu vibrasi yang meneruskan energi oleh satu seri pergeseran material yang kecil. Prepared by Arif-010308

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Ultrasonic testing is the process of applying ultrasonic sound to a specimen and determining its soundness, thickness, or some physical property. The energy is originated in something called a “Transducer” which causes material displacement within the specimen. A transducer is a device that converts energy from one form to another. Example: Electrical energy to mechanical, or mechanical to electrical. A speaker in a radio converts electrical energy to a back and forth mechanical movement. View “A” below illustrates the “Piezoelectric effect”. Electrical energy is applied through two wires connected to a crystal, causing the crystal to vibrate. The terms crystal and transducer are used interchangeably in this lesson.

Ultrasonic testing adalah suatu proses pengaplikasian suara ultrasonic terhadap benda uji dan menentukan kemulusan, ketebalan, atau sifat – sifat fisik. Energi yang asalnya dari suatu alat yang disebut “transducer” yang menyebabkan pergesaran material dalam benda uji. Transducer suatu alat yang mengkonversikan energi dari satu bentu ke bentuk lainnya. Contoh: energi listrik ke energi mekanis. Atau sebaliknya. Speaker (pengeras suara) mengkonversikan energi listrik menjadi pergerakan mekanis yang mondar – mandir.

Electrical energy causes a piezoelectric crystal to expand and contract, forming mechanical vibrations. A piezoelectric transducer can also convert mechanical energy to electrical energy. Therefore, a transducer can both send and receive energy.

Energi listrik menyebabkan kristal berekspansi dan mengkerut memebentuk /menghasilkan vibrasi mekanis. Transducer piezoelectric juga dapat mengkonversikan energi mekanis menjadi energ listrik. Makanya transducer dapat mengirim dan menerima energi.

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Gambar “A” dibawah ini menggambarkan “piezoelectric effect”. Energi listrik diaplikasikan melewati dua kawat yang dihubungkan ke kristal, yang menyebabkan kristal bervibrasi. Terminology kristal dan transducer digunakan silih berganti dalam pelajaran ini

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Energy transmitted by a transducer can be either pulsed or continuous. Pulsed ultrasound is defined as short groups of transmitted vibrations before and after which the transducer can act as a receiver.

Energi diteruskan oleh transducer dapat berupa pulsa (pulse) atau kontinyu (continuous). Pulsed ultrasound didefinisikan sebagai kelompok pendek dari vibrasi yang diteruskan sebelumnya oleh transducer dan setelahnya, dapat berfungsi sebagai receiver . Steel, water and oil will transmit ultrasound Steel, air, dan minyak akan menimbulkan ultrasound sangat baik sekali, tetapi kehadiran very well, but air presents a problem. udara akan menimbulkan masalah.

Air is a poor transmitter of ultrasound because Udara adalah media penerus ultrasound yang the particle density is so low that it is difficult to jelek karena kerapatan partikel cukup rendah yang akan menyulitkan meneruskan energi suara transmit sound energy from particle to particle. dari partikel ke partikel. That is why we put oil or grease between the Karena alasan itu diantara transducer dan benda uji diberi minyak atau gemuk. transducer and the specimen. The particle density of a material helps Kerapatan partikel material membantu dalam determine the velocity of sound. The velocity menentukan velocity (cepat lambat) suara. of sound will change as it moves from one Velocity suara akan berubah apabila bergerak medium to another as shown below. The dari suatu media ke media lainnya. Seperti terlihat pada gambar di bawah ini. Elasitas elasticity of the material is also a factor. material juga menjadi suatu faktor.

Visualize that the balls shown above represent Pada gambar, diperlihatkan bahwa bola atau bandul mewakili struktur atau bagian dalam dari the internal structure of air, water, and steel. udara, air dan besi. The impulse moving through the row of balls can Impulse bergerak melewati deretan bandul dapat dibandingkan terhadap pulsa suara ultrasonic. be compared to a pulse of ultrasonic sound. A practical example of the velocity of sound in Contoh praktis dari velocity suara pada material yang berbeda diperlihatkan different materials is shown below.

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Pada contoh diatas akan memakan waktu cukup lama buat suara melewati/melalui air daripada melewati besi (steel). Velocity suara pada steel kira – kira empat kali lebih besar daripada dalam air. A wavelength is considered to be the distance Panjang gelombang didasarkan pada jarak diantara dua urutan perpindahan. between two successive displacements. It will take longer for the sound to travel through the water than through the steel. The sound velocity in steel is approximately four times grater than in water.

The wavelength can also be defined as the Panjang gelombang dapat juga didefinisikan distance a wave travels during one complete sebagai jarak.suatu gelombang merambat selama satu siklus. cycle.

The symbol λ is used to represent a wavelength and is called “Lambda”. The illustration below shows a transducer vibrating at a fixed frequency (f) and transmitting sound waves into the specimen.

Simbol panjang gelombang (λ) disebut “lambda”

These sound waves move at a fixed velocity (v) through the specimen. The wavelength can be changed if the frequency of the transducer vibration changes.

Gelombang suara ini bergerak pda velocity yang tetap (V) melalui benda uji. Panjang gelombang dapat berubah bilamana frekwensi, dari vibrasi transducer berubah.

λ=

v f

Wavelength =

Example: you can shorten the wavelength by increasing the frequency. Wavelength is a ratio of a fixed value (Velocity) divided by a variable (Frequency). In practical situations, the smallest discontinuity you can find with ultrasonic testing is about ½ lambda (wavelength). Therefore, to detect smaller defects, you will need transducers that produce higher frequencies. Example: what would be the smallest discontinuity that you could find in a steel specimen with a velocity of 6 Rev. 00

Gambar di bawah ini memperlihatkan suatu transducer bervibrasi pada frekwensi yang tetap (f) dan meneruskan gelombang suara kedalam benda uji

velocity frequency

Contoh: Panjang gelombang dapat diperpendek dengan menaikkan frekwensi. Panjang gelombang adalah perbandingan dari velocity (nilainya tetap) dibagi dengan frekwensi (nilainya bervariabel) Pada situasi prakits, discontinuity terkecil yang dapat terdeteksi oleh ultrasonic sekitar ½ lambda (panjang gelombang) Oleh karena itu untuk mendeteksi defect yang lebih kecil diperlukan transducer yang menghasilkan frekwensi lebih tinggi. Contoh: berapa ukuran discontinuity terkecil yang dapat dideteksi pada benda uji steel dengan velocity 6 km/sec menggunakan transducer Prepared by Arif-010308

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km/sec using a transducer with a frekwensi 3 MHz frequency of 3 megahertz (MHz).

λ=

6 x105 cm / sec = 2 milli meters 3Mhz

If the smallest defect detectable is ½ Bilamana defect terkecil yang dapat dideteksi lambdas, then the answer is 1 adalah ½ λ maka jawabannya adalah 1 mm atau 0,040 inch millimeter or 0,040 inches.

UT LESSON 2 QUIZ F

1. Relative to ultrasonic testing, air is considered a good conductor and for this reason ultrasound will carry long distances In air.

T

2. Particle density of a material has a direct relationship to the velocity of sound in that material.

F

3. The symbol used to represent a wavelength is called "Shepda."

T

4. With everything else equal, the wavelength in water would be shorter than a wavelength in steel.

T

5. To understand our definition of ultrasonics, a steel ball Is considered to be more elastic than a lead ball.

F

6. Man can hear sounds up to approximately 5,000,000 Hz.

T

7. Vibrations pass through a solid material as a series of particle displacements.

F

8. The velocity of sound is slower in steel than In water.

T

9. The number of cycles in a given perlod of time is called the frequency.

T

10. For the purposes of this lesson, ½ the wavelength is considered to be the smallest discontinuity that can be detected with ultrasonics.

3 mm

11. If the longitudinal velocity in aluminum is 6.5 x 105 cm/sec and you are using a 2.5 MHz probe, what is the smallest dlscontinuity you can detect? (3 pts)

Piezoelectric

12. The ability of a transducer to convert mechanical energy to electrical and electrical energy to mechanical is due to the effect.

Wavelength

13. The distance that an ultrasonic pulse travels while a particle makes one complete cycle Is called___________.

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Lesson 3 ULTRASONIC EQUIPMENT

Peralatan Ultrasonic

The ultrasonic pulse echo instrument generates high voltage electrical pulses of short duration. These pulses are applied to the transducer which converts them into mechanical vibrations that are applied to the material being inspected. A large percentage of the sound is reflected from the front surface of the test part back to the transducer. The remainder is reflected by the back surface or discontinuities. The sound reflected back to the transducer is converted back to electrical pulses, which are amplified and displayed on the cathode ray tube (CRT) as vertical pulses. The a-scan display indicates the depth and the amplitude of the sound reflections from a discontinuity. The amplitude is a relative measure of the amount of reflected energy. There are two basic ultrasonic test systems:

Instrument pulsa gema elektronik membangkitkan pulsa listrik voltase tinggi dari durasi yang pendek. Pulsa ini diaplikasikan terhadap transducer yang mengkonversikan menjadi vibrasi mekanis yang diaplikasikan terhadap material yang sedang diperiksa. Presentasi suara yang cukup besar dipantulkan dari permukaan benda uji ke tranduser. Sisanya dipantulkan oleh permukaan bagian belakang benda uji atau diskontinuiti. Suara yang dipantulkan ke tranduser dikonversikan kembali menjadi pulsa listrik yang dikuatkan dan ditampilkan pada CRT (Cathode Ray Tube) sebagai pulsa vertical. Tampilan A-scan menunjukkan kedalaman dan amplitude pantulan suara dari diskontinuiti.

Rev. 00

Amplitudo adalah suatu ukuran relative dari sejumlah energi yang dipantulkan. Terdapat dua sistem ultrasonic test, yaitu:

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Pulse-echo is the most widely used ultrasonic system. Short evenly timed pulses of ultrasonic waves are transmitted into the material being tested. These pulses reflect from discontinuities in their path or from any boundary that they strike. The received reflections are then displayed on a cathode ray tube (CRT). The same transducer can be used to transmit and receive. Through transmission requires the use of two transducers, one for sending and the other for receiving. Either short pulses or continuous waves are transmitted into the material. The quality of the material being tested is measured in terms of energy lost by a sound beam as it travels through the material. There are two test methods normally used in ultrasonic testing. “Contact testing” where the transducer is coupled to the material through a thin layer of couplant. “Immersion testing” both the material and the transducer are immersed in a tank of couplant (usually water). To determine the location of discontinuities within a test part, the CRT horizontal display is divided into convenient increments such as centimeters, inches, etc.

Pulse echo paling banyak dipakai dalam ultrasonic testing. Pulsa yang waktunya sama dan pendek (short evenly timed pulse) dari gelombang ultrasonic diteruskan kedalam material yang sedang diperiksa). Pulsa ini dipantulkan oleh discontinuity selama dalam lintasannya atau dari setiap bidang yang ditabrak. Pantulan yang diterima kemudian ditampilkan pada CRT. Transduser yang sama dipergunakan sebagai penerus dan penerima gelombang ultrasonic. Through transmission memerlukan dua tranduser, satu untuk mengirim dan satu lagi untuk menerima. Baik short pulse ataupun continuous wave diteruskan kedalam material. Kwalitas dari material yang sedang diperiksa diukur dalam terminology kehilangan energi oleh pancaran suara (sound beam), sewaktu melintasi material. Terdapat dua metode pengujian yang umumnya digunakan dalam ultrasonic testing. “Contact Testing” (kontak langsung) transduser dirangkai dengan benda uji melalui suatu lapisan couplant yang tipis. “Immersion Testing” (rendam) baik material maupun transduser direndam dalam tangki couplant (biasanya terdiri dari air) Untuk menentukan lokasi diskontinuiti dalam benda uji, tampilan horizontal CRT dibagi kedalam satuan centimeters, inches

At a given sensitivity (gains) setting, the Pada sensitifiti tertentu (gain), amplitude dari pip amplitude of the pip is determined by the ditentukan oleh kekuatan sinyal yang Rev. 00

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strength of the signal generated by the reflected sound wave. Thus, the CRT displays two types of information: 1. Distance (time) of the discontinuity from the transducer. 2. Relative magnitude of the reflected energy. Focus and astigmatism controls adjust the sharpness of the displayed signals. Sensitivity or gain controls determine the amount of amplification the signals from the discontinuity received. Increasing the sensitivity (gain) increases the amplitude of the pips on the CRT screen. Two controls, the “Sweep length” and “Sweep delay” regulate how much of the test part is displayed at one time on the CRT, and what portion of the part is displayed.

dibangkitkan oleh gelombang suara yang dipantulkan. Jadi, CRT menampilkan dua tipe informasi: 1. jarak (waktu) diskontinuiti dari transduser.

The sweep delay control allows one to move the viewing screen along the depth of the test part. In immersion testing, the sweep delay can be used to remove the initial pulse from the CRT.

Control sweep delay mengizinkan sesuatu bergerak pada layer sepanjang kedalaman benda uji. Pada immersion testing, sweep delay dapat dipergunakan untuk menghasilkan initial pulse (pulsa awal) dari CRT.

2. besaran energi yang dipantulkan relative Kontrol “Focus dan Astigmatism” mengatur ketajaman sinyal yang ditampilkan. Control “sensitivity dan Gain” menentukan jumlah amplifikasi sinyal dari diskontinuiti yang diterima. Menaikkan sensitifiti (gain), berarti menaikkan amplitude dari pipe pada layer CRT.

Terdapat dua control “Sweep Length” dan “Sweep Delay”, mengatur berapa banyak benda uji ditampilkan pada waktu yang bersamaan pada CRT, dan berapa bagian dari benda uji yang ditampilkan. The sweep length (material control) Sweep length (control material) memperlebar atau expands or compresses the display on the mempersempit tampilan pada CRT seperti pada gambar di bawah ini: CRT as shown below:

“Pulse repetition rate” control regulates how Control “Pulse repetition rate” mengatur berapa often the pulse is applied. Pulse rates vary sering pulsa diaplikasikan. Rata – rata pulsa from 50 to 1200 pulses per second or more. bervariasi dari 50 sampai dengan 1200 pulsa setiap detik atau lebih. Rev. 00

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When the sweep is long, the pulse rate must be lower to allow enough time for the sweep to be displayed before another pulse is transmitted. In some instruments the pulse rate is adjusted automatically. Increasing the pulse length increases the amount of sound energy applied to the test part, but decreases the resolving power of the equipment. The “Pulse energy” must be increased to obtain deep penetration or to penetrate coarse grained materials. The “Reject Control” or “Suppression Control” is used to eliminate or reduce “grass” or every low amplitude pips along the base of the sweep line. This control may affect the vertical linearity of the presentation. A “Flaw alarm” or “Gating circuit” is used to establish zones along the sweep line within which pips of predetermined amplitude will activate either an alarm or a recording system.

Bilamana “Sweep” cukup panjang, rata – rata pulsa harus lebih rendah untuk mengizinkan waktu yang cukup untuk sweep ditampilkan sebelum pulsa lainnya diteruskan. Pada beberapa instrument, rata – rata pulsa diatur secara otomatis. Menaikkan panjang pulsa, menaikkan jumlah energi suara yang diaplikasikan terhadap benda uji. Akan tetapi menurunkan daya pemisah peralatan. Energi pulsa harus ditingkatkan untuk mendapatkan penetrasi yang dalam atau penetrasi material yang mempunyai butiran kasar. Control “reject” atau ‘suppression” digunakan untuk menghilangkan atau menurunkan “grass” atau pip amplitude yang sangat rendah sepanjang sweep line, control ini akan mempengaruhi tampilan “vertical linearity”. “Flaw Alarm” atau “gating circuit” digunakan untuk membentuk zona sepanjang sweep line dimana pip yang amplitudonya telah ditentukan akan mengaktifkan baik alarm maupun system pencatatan.

“Control jarak / amplitude” dalam ultrasonic testing amplitude pip dari suatu diskontinuiti dengan ukuran tertentu turun bilamana kedalamannya bertambah (lebih dalam). Untuk mengkompensasi atenuasi ini, control elektronik telah dilengkapi pada kebanyakan peralatan ultrasonic. Some of the common names for this control Beberapa nama – nama yang umum untuk control ini adalah: are: DAC: distance amplitude correction DAC – Distance Amplitude Correction TCG: time corrected gain TCG – Time Correction Gain STC: sensitivity time control STC – Sensitivity Time Control This control is very useful when used in Control ini sangat berguna bilamana digunakan conjunction with the flaw alarm and with berhubungan dengan flaw alarm dan system pelaporan. recording systems.

“Distance / amplitude control” in ultrasonic testing the amplitude of the pip from a discontinuity of a given size decreases as the depth increases. To compensate for this “attenuation,” an electronic control has been added to many ultrasonic units.

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UT LESSON 3 WORKSHEET #1 A. As shown below, many ultrasonic units have 50 divisions along the base line of the CRT screen. By using the simple formula below, we can make the distance across the screen represent any distance we wish from about .5 inches to over 100 inches. The formula used to find the value of each division on the screen below is:

Increment / Division =

Range x 2 100

EXAMPLE: If you wanted the entire screen to represent lo", we would find that by using the formula that, each division on the base line represents 0.2".

Inc / Div =

10 x 2 20 = = 0.2" 100 100

B. After you have selected a suitable screen range it is then possible to use the sweep controls and match the pulses on the CRT to a known thickness calibration block. This will be discussed in later lessons. C. Many Ultrasonic units have 100 divisions across the base line instead of 50. In this case simply divide the range by 100 to find the increment per division. D. On the next page fill in the CRT screens as instructed.

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UT LESSON 3 WORKSHEET #1

On the CRT screens below, draw in the left edge of the first back reflection and at least one multiple of the back echo as it would appear using a normal beam transducer on a properly calibrated unit.

A

B

SCREEN RANGE - 1" PART THICKNESS – 0.49”

C

SCREEN RANGE - 25" PART THICKNESS – 4 3/16"

D

SCREEN RANGE - 20" PART THICKNESS – 6 7/8"

E

SCREEN RANGE - 1" PART THICKNESS – 3/16"

F

SCREEN RANGE – 2.5" PART THICKNESS – 0.68"

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SCREEN RANGE - 50" PART THICKNESS – 10 3/8"

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UT LESSON 3 QUIZ F

1.

With "Through Transmission", an increase in amplitude indicates the presence of a possible discontinuity.

F

2.

The "Pulse Echo" system uses a continuous wave and a separate transducer receives the echo.

T

3.

Both contact testing and immersion testing require the use of a coupling medium.

T

4.

Typically, the "gain" control will determine the amount of amplification for a suspected discontinuity indication.

F

5.

Sweep length and sweep delay are two names for the same control.

F

6.

The sweep length control is often used to sweep the initial pulse off the CRT in immersion testing.

D

7.

In the A-scan presentation used in contact testing, the height of the vertical deflection (pip) on the CRT represents: a. velocity b. elapsed time c. distance d. signal amplitude

F

8.

The "distance amplitude correction" control has the ability to automatically increase the screen range when a thicker part is inspected.

30 div 9.

On the CRT "A" below, draw in the pulse if a normal beam transducer were used to show a 9” deep continuity using a 15" screen range. How many divisions from the left?

1.65”

10. On the CRT “B” below, what is the distance to the pulse if a 2.5” screen range were being used for the inspection? (3 Pts)

A

B

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Lesson 4 MODES OF ULTRASONIC WAVE TRAVEL Velocity can be defined as the distance a wave will propagate through a medium in a given unit of time, usually a second. The wave speed remains constant through a given medium.

Modes of ultrasonic travel Velocity dapat didefinisikan sebagai jarak suatu gelombang akan merambat melalui suatu media dalam suatu satuan waktu, biasanya detik. Kecepatan gelombang tetap konstan melalui suatu media.

Listed below is a table of impedance, velocity and density values. This information will be useful later in this lesson for performing basic ultrasonic calculations.

Dibawah ini adalah table impedansi, velocity dan density. Informasi ini akan berguna pada akhir pelajaran ini untuk perhitungan dasar – dasar ultrasonic.

Material Air Water Aluminium Steel

ACOUSTIC SOUND Impedance Velocity (gram/cm2-sec) (cm/sec) 0.000033 x 106 0.33 x 105 6 0.149 x 10 1.49 x 105 6 1.72 x 10 6.35 x 105 4.56 x 106 5.85 x 105

Density (gram/cm3) 0.001 1.00 2.71 7.8

Gelombang ultrasonic dipantulkan bilamana menabrak suatu media yang berbeda impedansi akustiknya. Permukaan yang mengakibatkan pantulan ini disebut “Interface”. Interface adalah batas umum antara dua material atau fase, seperti aluminium dengan steel atau air dengan steel. Pancaran energi mencapai suatu interface dihubungkan sebagai suatu gelombang sudut datang. The angle at which the wave strikes the Dimana gelombang menabrak interface disebut interface is known as the “Angle of sebagai “Sudut datang” seperti diperlihatkan dibawah ini. incidence” as shown below.

Ultrasonic waves are reflected when they encounter a medium of a different acoustical impedance. The “surface” at which this reflection occurs is called an “interface”. An interface is the common boundary between two materials or phases, such as aluminum – to – steel or water – to – steel. A beam of energy approaching an interface is referred to as an “Incident wave”.

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The incident wave is said to have normal incidence when its direction of propagation is perpendicular to an interface. As shown below the angle of incidence is zero.

Gelombang datang disebut memiliki normal incidence bilamana arah perambatannya tegak lurus terhadap interface. Seperti terlihat dibawah ini, bahwa sudut dating sama dengan nol.

Some of the wave energy striking an interface Sebagian energi gelombang menabrak interface will be transmitted through the interface, and akan diteruskan melewati interface, dan some will be reflected at the angle of incidence. sebagainnya akan dipantulkan pada sudut datang. pantulan tergantung kepada The amount of reflection depends on the Jumlah acoustic impedance ratio between the two perbangdingan impedansi akustik diantara dua media involved. This reflectance factor will be media yang terlibat. Factor refleksi akan dibicarakan secara detail pada pelajaran discussed in detail in the next lesson. berikutnya. The angle of reflection at an interface or Sudut pantul pada suatu interface atau bidang boundary always equals the angle of selalu sama dengan sudut datang. Sudut “A” = sudut “B”. incidence. Angle “A” = Angle “B”.

Ultrasonic vibrations travel in many modes, and the most common are: 1. Longitudinal (Compression) 2. Shear (Transverse) 3. Surface (Rayleigh) 4. Plate (Lamb) Each wave mode has a specific function in ultrasonic inspection and it is important that each be understood completely. Rev. 00

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Longitudinal (compressional) wave have Gelombang longitudinal (compression) particle vibrations in a back and forth motion in mempunyai vibrasi partikel dalam suatu gerakan mondar – mondir dan searah dengan perambatan the direction of wave propagation. gelombang. Consider that all materials are made up of Pertimbangan bahwa semua material tersebut atoms lined up in straight lines to form a dari atom – atom yang tersusun pada garis lurus lattice structure. When striking the side of membentuk “lattice structure”, bilamana the lattice, a chain reaction of particle menabrak sisi lattice, reaksi rantai dari gerakan movement is started causing the partikel menghasilkan gelombang longitudinal. longitudinal wave.

Shear (Transverse) waves have particle vibrations perpendicular to the direction of wave motion. Shear waves will not travel through liquids or gasses. In some materials, the velocity of a shear wave is about ½ that of longitudinal waves. Therefore, the wavelength is shorter (about ½), permitting smaller discontinuities to be located.

Gelombang shear (transversal) mempunyai vibrasi partikel tegak lurus terhadap arah gerakan gelombang. Gelombang transversal tidak akan bergerak melewati cairan atau gas. Pada sebagian material, velocity gelombang transversal kira – kira ½ dari gelombang longitudinal. Makanya panjang gelombang lebih pendek (kira- kira ½) dan discontinuity yang akan terdeteksi lebih kecil

Mode conversion takes place when a sound beam hits an interface between two different media at an angle other than 90 degrees. Mode conversion in the case presented below produces two reflected beams: One beam consists of longitudinal waves. The other beam consists of shear waves.

Mode conversion terjadi bilamana pancaran suara menambrak suatu interpret diantara dua media yang sudutnya tidak pada 900 Mode conversion yang ditampilkan di bawah ini menghasilkan dua pantulan pancaran. Satu pancaran terdiri dari gelombang longitudinal dan pancaran lainnya adalah gelombang transversal.

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The ultrasonic angle beam transducer uses the Transducer pancaran sudut ultrasonic following example. The “Refracted” shear waves menggunakan contoh berikut ini. Gelombang are useful in many inspection techniques. transversal yang dibiaskan berguna dalam teknik inspeksi The “Angle of refraction” is the angle “Sudut bias” adalah sudut yang terjadi diantara formed between a refracted beam as it pancaran bias sewaktu memasuki medium yang enters the second medium and a line drawn kedua denan suatu garis tegak lurus terhadap interface. perpendicular to the interface.

Snell’s law can be used to determine angular “Hukum Snellius” dapat digunakan untuk relationships between media for both menentukan hubungan sudut diantara media baik longitudinal and shear waves. untuk gelombang longitudinal dan gelombang transversal.

sin φ1 V1 = sin φ 2 V2 The following example calculates the angle of refraction Φ2 for a longitudinal wave passing through water to steel interface. 10 degrees = Angle of incidence (Φ1 ) 1, 49 Km/sec = Longitudinal Velocity in Water (V1) 5, 85 Km/sec = Longitudinal Velocity in Steel (V2)

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Ø1 V1 Ø2 V2

= = = =

angle of incidence velocity in first medium angle of refraction velocity in second medium

Berikut ini adalah contoh menghitung sudut bias untuk suatu gelombang longitudinal yang melewati interface antara air dan steel Sudut datang = 100 Velocity air = 1,49 km/sec. Longitudinal steel = 5,85 km/sec

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sin φ1 V1 = sin φ 2 V2 sin φ 2 =

V2 (sin φ1 ) V1

1.012 1.49 sin φ 2 = 0.6791

sin φ 2 =

φ 2 = 42 0 46 ' As the angle of incidence increases, the angle of refraction increases. When the refraction angle of a longitudinal wave reaches 90 degrees, the wave emerges from the second medium and travels parallel to the interface or surface. This is called its first or lower “Critical Angle” above approximately 28 degrees with a plastic-to-steel interface, only shear waves are generated in the part.

Bilamana sudut datang naik maka sudut bias akan naik. Bilamana sudut bias dari gelombang longitudinal mendekati 900 gelombang muncul dari medium kedua dan bergerak sejajar terhadap interface atau permukaan. Kejadian ini disebut sudut krits pertama lebih rendah kira- kira diatas 280 dengan interface diantara lastik dan steel, hanya gelombang transversal yang diteruskan kedalam benda uji.

If the angle of incidence is increased past first critical angle, only a shear wave is generated in the part. When the angle of refraction for the shear wave is 90 degrees, then we have reached the upper or second critical angle which produces surface waves. As shown below, there is then total reflection for both longitudinal and shear waves. With a plastic-to-steel interface, this happens at approximately 58 degrees.

Jika sudut datang dinaikkan melewati sudut kritis pertama, hanya gelombang transversal yang dibangkitkan dalam benda uji. Bilamana sudut bias gelombang transversal 900, maka sudut kritis kedua telah tercapai atau lebih, dimana menghasilkan gelombang permukaan. Seperti diperlihatkan pada contoh di bawah ini, adalah total pantulan untuk gelombang longitudinal dan gelombang transversal. Dengan suatu interface antara plastic dan steel kejadian ini terjadi pada 580.

When the incident beam is at its second Bilamana pancaran datang adalah pada sudut critical angle, a third type of wave is kritis kedua, akan terjadi tipe gelombang ketiga developed, called a Rayleigh of surface wave. yang disebut gelombang permukaan atau Rev. 00

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rayleigh. As shown below, the wave travels with an Seperti terlihat pada gambar di bawah ini, elliptical particle motion. gelombang bergerak dengan gerakan partikel yang membentuk eliptikal. Surface waves are useful in detecting Gelombang permukaan berguna dalam surface cracks, but only penetrate about one mendeteksi crack permukaan tetapi penetrasinya kira – kira 1 λ. wavelength.

As shown below, surface waves have the ability to follow the surface contour as long as the contour does not sharply change. However, the surface wave can be almost completely absorbed by excess couplant or by touching your finger to the surface of the part ahead of the transducer.

Pada gambar di bawah ini gelombang permukaan memiliki kemampuan mengikuti keliling permukaan selagi kelilingnya tidak ada permukaan yang tajam, gelombang permukaan hampir dapat diserap secara sempurna, oleh pengaruh couplant atau sentuhan jari pada permukaan benda uji dihadapan transducer.

Plate waves or lamb waves have the ability to propagate through thin plates in a variety of wave modes depending on plate thickness, transducer frequency and incident angle. Plate waves are generated by using longitudinal waves which develop either symmetrical or asymmetrical wave as shown below.

Gelombang pelat atau lamp memiliki kemampuan merambat melalui pelat tipis dalam variasi mode gelombang tergantung pada ketebalan pelat, frekwensi transducer dan sudut datang. Gelombang pelat dibangkitkan dengan menggunakan gelombang longitudinal yang menghasilkan baik gelombang symmetrical atau assymetrical seperti terlihat pada gambar di bawah ini. pelat menempati kesuluruhan Plate waves occupy the entire thickness of Gelombang the part. Without “saturating” the part, the ketebalan benda uji. Tanpa menjenuhkannya, gelombang tidak akan terjadi. wave cannot exist.

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To generate plate waves, you adjust the incident angle to the point that maximum reflections are observed on the CRT screen from a known reflector. It is not possible to generate shear or surface waves on materials thinner than one-half wavelength. Therefore, plate waves are useful as shown below.

Untuk merambatkan gelombang pelat, atur sudut dating ke titik dimana pantulan maksimum diamati pada layar CRTdari suatu reflector. Adalah tidak mungkin merambatkan gelombang permukaan atau transversal pada material yang lebih tipis daripada ½ λ. Oleh karena itu gelombang pelat berguna seperti pada contoh di bawah ini.

UT LESSON 4 WORKSHEET # 1

A. Using Snell's Law, calculate the following refraction problems, using the information in the sketch below. 660

1.

Find the refracted longitudinal wave If the incident angle Ф, is 25 degrees. (SHOW WORK) (2 pts)

570

2.

Find the refracted shear wave angle i f the incident angle is 45 degrees. (SHOW WORK) (2 pts)

530

3.

If you wanted a shear wave to travel into the steel at 70 degrees, what would the incident angle through the lucite be? (SHOW WORK) (2 pts)

470

4.

If Ф1 = 180, is it possible to have a refracted longitudinal wave? If yes, what is it? (SHOW WORK) (2 pts) If no, why not?

N0

5.

If Ф1 = 360, is it possible to have a refracted longitudinal wave? If yes. what is it? (SHOW WORK) If no. why not?

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UT LESSON 4 QUIZ T

1.

An "ultrasonic beam" travels through a medium as waves of sound energy.

F

2.

Normal incidence is when the incident beam is parallel to the interface.

F

3.

The refraction of an incident beam at an interface is equal to its angle of reflection.

T

4.

Particle vibration in a longitudinal wave is in the direction of wave propagation.

F

5.

Shear wave velocity is approximately twice the velocity of longitudinal waves.

T

6.

Mode conversion occurs when a sound beam strikes an interface between two medla of different velocities at an angle.

T

7.

The bending of an incident beam as it passes through an interface is called refraction.

T

8.

Longitudinal waves will propagate through both solids and liquids.

T

9.

Both plate waves and surface waves can follow the part contour.

sin φ1 V1 = sin φ2 V2

Shear velocity in steel Long.velocity in steel Long.velocity in water Long.velocity in lucite

= 3.23 x 105 cm/sec = 5.85 x 105 cm/sec = 1.49 x 105 cm/sec = 2.73 x 105 cm/sec

USING THE ABOVE INFORMATION, SOLVE THE FOLLOWING PROBLEMS. INDICATE THE APPROXIMATE ANGLES ON THE SKETCH AND LABEL EACH. 470

10. If you wanted a shear wave to travel into steel at 60 degrees, what would be the incident angle on the lucite wedge? (SHOW WORK) (3 pts)

550

11. What would be the refracted longitudinal wave if the angle of incidence through a water to steel interface is 12 degrees? (SHOW WORK) (3 pts)

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Lesson 5 COUPLANTS AND ULTRASONIC SOUND ENERGY. The primary purpose of a couplant is to provide a suitable sound path between the transducer and the test surface. A couplant must effectively wet or totally contact both surfaces of the transducer and test part. 1. The couplant must exclude all air from between the surfaces as air is a very poor conductor of sound. 2. The couplant fills in and smooths out irregularities on the surface of the test part. 3. The couplant aids in the movement of the transducer over the surface in contact testing. 4. A practical couplant must be easy to apply and easy to remove. It must also be harmless to the part surface.

Couplant dan energi suara ultrasonic

Oil or water mixed with glycerine (2 parts water and part glycerine) is commonly used couplants. Even wallpaper paste has advantages as a couplant. Heavier couplants, such as grease or heavy oil can be used on rough or vertical surfaces. Specially formulated liquid and paste couplants are also available from ultrasonic equipment manufacturers. In circumstances where the use of liquids or paste is undesirable, thin rubber or rubber-like materials may be used. In all cases the couplant should be as thin as possible. If the couplant is excessive, it may act as a wedge and alter the direction of the sound beam. The surface of a test specimen can greatly affect ultrasonic wave propagation. Rough surfaces can cause undesirable effects such as reduction of discontinuity and back surface amplitudes due to distortion of wave directivity.

Minyak atau campuran air dengan glycerine (2:1) umum digunakan sebagai couplant. Bahkan lem kertas dapat digunakan pada permukaan yang kasar atau vertical. Couplant yang lebih kental seperti gemuk atau minyak kental dapat digunakan pada permukaan yang kasar atau vertikal. Couplant cair dan pasta yang diformulasi spesial dari pembuat alat ultrasonic bisa dipakai.

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Tujuan utama dari couplant adalah untuk memberikan lintasan suara yang tepat diantara transducer dan pemrukaan benda uji. Couplant harus secara efektif membasahi atau secara total menghubungkan kedua permukaan transducer dan benda uji. 1. Couplant harus mengeluarkan semua udara dari permukaan udara adalah penghantar sura yang paling buruk 2. Couplant meratakan / memuluskan permukaan yang tidak mulus. 3. Couplant membantu pergerakan transducer diatas permukaan pada kontak langsung 4. Secara praktis, couplant harus mudah diaplikasikan dan mudah untuk dibersihkan, tidak boleh merusak permukaan benda uji.

Dalam suatu situasi dimana penggunaan cairan atau pasta tidak diinginkan, karet tipis atau karet tiruan dapat digunakan. Couplant harus diaplikasikan setipis mungkin, jika tidak akan bertindak sebagai pasak dan merubah arah pancaran suara. Permukaan benda uji dapat mempengaruhi perambatan gelombang ultrasonic. Permukaan yang kasar dapat menyebabkan efek yang tidak diinginkan seperti penurunan amplitudo discontinuity dan back wall dikarenakan distorsi dari pengarahan gelombang. Prepared by Arif-010308

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A good back surface reflection indicates a good response from the material being tested. It is reflected back to its source similar to light striking a mirror. If the surfaces are not parallel, the reflected energy will be directed away from the transducer similar to light falling on a mirror at an angle.

Pantulan backwall yang baik menunjukkan respon yang baik dari material yang sedang diperiksa. Hal ini dipantulkan kembali ke sumbernya, sama dengan cahaya menabrak cermin. Jika permukaan tidak sejajar, energi yang dipantulkan akan diarahkan menjauhi transducer, sama dengan cahaya menabrak cermin pada suatu sudut.

The physical shape or contour of a part must be considered when attempting to discern whether a discontinuity indication is real or false.

Bentuk fisika atau sekeliling benda uji harus dipertimbangkan bilamana mencoba untuk melhat apakah suatu indikasi discontinuity itu benar atau palsu.

In testing long specimens, reflection of a Pada pemeriksaan benda uji yang panjang, spreading beam can produce false pantulan dari pancaran yang menyebar dapat menghasilkan indikasi palsu pada CRT seperti indications on the CRT as show below. terlihat di bawah ini. Rev. 00

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A shear wave may be generated which is reflected at a steep angle to the opposite side, where mode conversion takes place. Mode conversion will be discussed in a later lesson. However, this type of false signal will appear on the right side of the first back echo.

Gelombang transversal dapat dirambatkan yang dipantulkan pada suatu sudut yang terjal terhadap sisi lawan, dimana mode conversion terjadi. Mode conversion akan didiskusikan pada pelajaran berikutnya. Bagaimanapun juga, tipe sinyal palsu ini akan muncul pada sisi kanan dari sinyal back echo pertama.

Grain structure has a great influence on the acoustical properties of a material. A steel forging generally has a fine grain structure and has a low damping effect on the sound beam. However, a casting generally has a coarser grain structure which is more difficult to get sound through.

Struktur butiran mempunyai pengaruh yang besar pada sifat – sifat akustik material. Steel forging umumnya mempunyai struktur butiran halus dan mempunyai efek peredaman yang rendah pada pancaran suara. Bagaimanapun juga, casting pada umunya mempunyai struktur butiran lebih kasar yang lebih sukar buat suara lewat.

When a discontinuity is not normal (at 90 degrees) to the incident wave, the reflected wave will be at an angle. As shown below, the result is a reduction in the amplitude of the discontinuity indication displayed on the CRT.

Bilamana suatu discontinuity tidak normal (pada 900) terhadap gelombang datang, gelombang yang dipantulkan berada pada suatu sudut. Seperti pada gambar di bawah ini, hasil dari penurunan amplitude indikasi discontinuity ditampilkan pada CRT.

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At position, “A” above, there is a sharp discontinuity indication and little back surface indication. At position “C” the discontinuity is at a minimum, or may not be seen at all. Two basic techniques are used in locating and evaluating angular flaws. 1. Contact testing utilizes an “angle beam” transducer with a plastic wedge to change the direction of wave propagation. 2. Immersion testing uses water as a couplant, tilting the transducer to achieve the necessary directionality.

Pada posisi “A” diatas, ada suatu indikasi discontinuity yang tajam dan indikasi permukaan sisi belakang cukup kecil. Pada posisi C discontinuity pada posisi maksimum, atau tidak terlihat sama sekali. Dua teknik dasar yang digunakan dalam mencari dan mengevaluasi cacat. 1. Kontak langsung menggunakan transducer “pancaran sudut” dengan plastic wedge untuk merubah arah perambatan gelombang. 2. terendam menggunakan air sebagai couplant, memiringkan transducer untuk mendapatkan arah yang tepat.

The shape or surface condition of a discontinuity influences the indication on the CRT. A discontinuity having a rough surface will tend to scatter the reflection as compared to a smooth flaw. Nonmetallic inclusions are typically rough and would scatter the sound more than a crack-like discontinuity. Air is a poor medium for transferring ultrasonic vibrations into liquids or solids. Therefore, a couplant must be used to transfer energy from the transducer to the test material.

Kondisi permukaan atau bentuk discontinuity mempengaruhi indiksi pada CRT.

Most of the ultrasonic energy is concentrated along the center line of the beam. The secondary or side lobes form at the transducer face and radiate away from the principle direction of sound travel. These secondary lobes represent areas of high and low intensities at the edge of the beam. Because of the secondary lobes, the useful width of a transducer beam is less than the

Sebagian besar energi ultrasonic terkonsentrasi sepanjang garis pusat (center line) dari pancaran. Lobe sisi atau lobe kedua mewakili area intensitas tinggi dan rendah pada sisi pancaran.

Diskontinuiti yang berpermukaan kasar akan cenderung menyebabkan pantulan dibandingkan cacat yang mulus. Inklusi nonmetalik adalah cacat yang kasar dan akan menyebabkan suara lebih dari diskontinuiti yang berbentuk retak. Udara adalah media yang buruk untuk meneruskan vibrasi ultrasonic ke dalam cairan atau padat. Oleh karena itu, couplant harus digunakan untuk untuk meneruskan energi dari tranduser ke benda uji. Water is a commonly used couplant as Air umum digunakan sebagai couplant seperti terlihat pada gambar di bawah ini. shown below:

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Lobe kedua menunjukkan area intensitas tinggi dan tendah pada tepi pancaran. Karena lobe kedua, lebar pancaran transduser yang berguna kurang dari lebar fisik transduser. Prepared by Arif-010308

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transducer’s physical width. Transducer diameter has a definite influence on the sound beam transmitted through a medium. For a given frequency, a smaller transducer has a greater beam spread angle than a larger diameter transducer as shown below:

Diameter transduser mempunyai pengaruh yang nyata pada pancaran suara yang diteruskan melewati media. Pada frekwensi tertentu, transduser yang lebih kecil memiliki sudut penyebaran pancaran yang lebih besar daripada transduser yang berdiameter lebih besar seperti pada gambar dibawah ini.

Merubah frekwensi vibrasi tranduser juga akan merubah penyebaran pancaran. Penyebaran berbanding terbalik secara proporsional dengan frekwensi. Oleh karena itu, transduser dengan frekwensi tinggi mempunyai diameter pancaran suara yang lebih konstan daripada transduser frekwensi rendah. Beam divergence can be reduced by Penyebaran pancaran dapat diturunkan dengan increasing the transducer frequency or by menaikkan frekwensi transduser atau dengan menggunakan transduser diameter lebih besar. using a larger diameter transducer. The amount of beam spread is determined by Jumlah penyebaran pancaran ditentukan oleh persamaan sebagai berikut: the following equation: Changing the transducer’s vibrating frequency will also change the beam spread. Divergence is inversely proportional to frequency. Therefore, a high frequency transducer has a more constant diameter sound beam than a low frequency transducer.

sin φ = 1,22

λ D

Where λ = Wavelength D = Diameter Ø = Half – Angle of beam spread to half – power points. The beam spread of a ½ inch diameter, 1 MHz transducer is shown to be 34 degrees. Remember that wavelength (λ) is determined by dividing the velocity by the frequency. To change inches to centimeters, multiply by 2,54.

Rev. 00

Penyebaran pancaran dari 0.5 in diameter, 1 Mhz transduser ditunjukkan menjadi 340. Ingat bahwa panjang gelombang (λ) ditentukan dengan membagi velocity terhadap frekwensi.

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UT LESSON 5 WORKSHEET #1 A. Understanding "Beam Spread" will help point out the importance of selecting the proper frequency and size transducer. The length of the ultrasonic wave and the diameter of the transducer are often critical in the determination of flaw size and location. B. Using the information given below, determine the "Beam Spread" for the conditions listed. (a) Velocity in steel = 0.585 x 105 cm/sec (b) Velocity in aluminum = 0.625 x 105 cm/sec (c) One Inch = 2.54 centimeters (d) Wavelength (λ ) = (e) sin φ = 1.22

velocity frequency

λ D

8”

1.

What would be the beam spread using a 1" dlameter, 2.25 MHz transducer on an aluminum test part? (SHOW WORK) (3 pts)

17.5”

2.

What would be the beam spread using a 1" diameter, one MHz transducer on an aluminium test part? (SHOW WORK) (3 pts)

14”

3.

What would be the beam spread using a one half inch diameter, 2.25 MHz transducer on a steel test part? (SHOW WORK) (3 pts)

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UT LESSON 5 QUIZ T

1.

Higher frequency transducers have less beam spread than low frequency transducers.

F

2.

Lower frequency transducers are usually used to find the smaller defects.

F

3.

The longer the wavelength (λ), the greater the beam spread and better ability to locale small discontinuities.

F

4.

When comparing two transducers of the same frequency, the larger transducer will have the greatest beam spread.

T

5.

A rough surface on the test specimen may cause a loss in amplitude on the CRT screen.

F

6.

If the front and back surfaces of a test part are not parallel, there will be a greatly reduced signal amplitude from any discontinuity in the part.

T

7.

Long or thin specimens may cause false indications due to mode conversion of the longitudinal beam.

T

8.

A smooth discontinuity (crack) will reflect more energy than a discontinulty will a rough surface (inclusion).

T

9.

Both contact and immersion testing techniques can be used for performing an "angle beam" examination of a part.

F

10. The couplant used in ultrasonic inspection should be as thick as possible to properly direct the sound beam.

T

11. Where a liquid or paste couplant cannot be used, a rubber sheet may sometimes be used by placing it between the transducer and test part.

3”

12. What would be the "Beam Spread" if the following conditions existed? a. 1 " Diameter, 5 MHz transducer. b. Velocity in steel = 0.585 x 100 cm/sec

Rev. 00

λ

c.

sin φ = 1.22

d.

Wavelength (λ ) =

e. f.

one inch = 2.54 centimeters (3 pts – SHOW WORK)

D

velocity frequency

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Lesson 6 ATTENUATION, ACOUSTIC IMPEDANCE, AND RESONANCE As shown below, a beam of sound energy will spread out (diverge) as it moves through the specimen, and the intensity (energy) decreases with distance away from the transducer and away from the center of the beam.

ATENUASI, AKUSTIK IMPEDANSI, RESONANSI. Seperti terlihat di bawah ini, pancaran energi suara akan disebarkan sewaktu bergerak melalui benda uji, dan intensitas (energi) menurun dengan semakin jauhnya dari transduser dan jauh dari pusat pancaran.

Untuk suatu ukuran transduser: For a given size transducer: High frequency transducers produce narrower Transduser frekwensi tinggi menghasilkan pancaran suara yang lebih sempit daripada sound beams than low frequency transducers. transduser frekwensi rendah. For the purpose of illustration, ultrasonic sound Sebagai gambaran, suara ultrasonic dapat dilihat can be viewed as a narrow cone-shaped beam sebagai pancaran yang berbentuk corong yang sempit yang dibagi kedalam dua zona. which is divided into two zones. The intensity in the near zone varies irregularly Intensitas pada near zone bervariasi secara tidak due to sound wave interaction close to the teratur terhadap interaksi gelombang suara dekat transducer. This prevents reliable detection of transduser. Hal ini mencegah pendeteksian diskontinuiti dekat ke permukaan. discontinuities close to the surface. In the far zone, the intensity (energy) Pada far zone, intensitas (energi) menurun decreases steadily due to both attenuation and dengan tetap terhadap atenuasi dan penyebaran pancaran. beam spread.

The intensity at point “Y” above is less than at Intensitas pada titik “Y” kurang dari pada titik “X”. point “X”. Attenuation is the term used to atenuasi adalah suatu terminology yang digunakan untuk menguraikan kondisi kehilangan describe this condition of energy loss. energi. Attenuation means the process of lessening Atenuasi berarti proses pengurangan jumlah. the amount. The primary reasons for attenuation are Alasan utama terjadinya atenuasi adalah absorption and scattering of the ultrasonic penyerapan dan penyebaran energi ultrasonic. energy. Attenuation is different in different materials, Atenuasi berbeda untuk material yang berbeda, depending on the absorption and scattering of tergantung pada penyebaran dan penyebaran suara. Fenomena lainnya yang the sound energy. Another phenomenon which energi pertains to the interrelationship of the sound and menyinggung hubungan suara dan sifat – sifat material adalah “akustik impedansi”. material properties is “Acoustic impedance.” This term should not be confused with Terminology ini tidak harus membingungkan dengan “atenuasi”. “Attenuation.” Rev. 00

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“Acoustical Impedance” (Z) is defined as the product of the density (ρ) and sound velocity (V) within a given material. Impedance = Density x velocity, or Z= ρ V Impedance values for typical materials are shown below: Material Air Water Aluminium Steel

“akustik impedansi” (Z) didefinisikan hasil perkalian antara density (ρ) dan velocity suara (V) dalam suatu material tertentu Impedance = Density x velocity, atau Z= ρ V Nilai impedansi untuk tipe material terlihat pada table dibawah ini

Impedance (gram/cm2-sec) 0.000033 x 106 0.149 x 106 1.72 x 106 4.56 x 106

Velocity (cm/sec) 0.33 x 105 1.49 x 105 6.35 x 105 5.85 x 105

Attenuation is defined as the loss of energy (acoustic) per unit of distance. For ultrasonic wave propagation, the attenuation constant α is given by:

Density (gram/cm3) 0.001 1.00 2.71 7.8

Atenuasi didefinisikan sebagai kehilangan energi (akustik) per satuan jarak. Untuk perambatan gelombang ultrasonic, konstanta atenuasi sebagai berikut:

I2 = e − 2α I1 Where: α = attenuation constant

I2 I1

= ratio of intensities at two points a unit distance apart

I 1 > I2 If acoustic energy is transmitted into two pieces of perfectly bonded identical steel, we find the sound has the same velocity through both, with an impedance ratio of 1 to 1.

Energi akustik diteruskan kedalam dua media yang menempel secara sempurna, suara akan mempunyai velocity yang sama pada kedua media tersebut dengan perbandingan 1 : 1

An impedance ratio of anything less or greater Perbandingan impedansi dari setiap media kurang atau lebih besar dari 1 : 1 adalah tidak than 1 to 1 is less than ideal. ideal. As shown below a large portion of the sound Seperti terlihat dibawah ini, suatu porsi yang beam from water to steel interface will reflect besar dari pancaran suara dari air ke steel back towards the transducer and never enter interface akan memantulkan kembali kearah transduser dan tidak oernah masuk ke dalam the part. benda uji.

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To determine how much of the energy is Untuk menentukan berapa banyak energi yang reflected you can use the following formula: dipantulkan dapat menggunakan rumus berikut:

⎛ Z − Z2 REFLECTION FACTOR ( R) = ⎜⎜ 1 ⎝ Z1 + Z 2

⎞ ⎟⎟ ⎠

2

Z = Acoustical Impedance In the illustration above, how much of the sound Dengan menggunakan rumus diatas, berapa energy is reflected from the water to steel banyak energi suara dipantulkan dari air ke steel interface? interface.

⎛ 4.56 − 0.149 ⎞ ⎛ 4.411 ⎞ R=⎜ ⎟ =⎜ ⎟ = 88 percent reflected ⎝ 4.56 + 0.149 ⎠ ⎝ 4.709 ⎠ 2

2

Resonance can be defined as the characteristic of a vibrating body to resonate or vibrate is sympathy with a vibration source. As shown below, a resonant condition will exist any time a continuous longitudinal wave is introduced into a specimen and reflected “in phase” with the incoming wave.

Resonansi dapat didefinisikan sebagai karakter dari badan yang bergetar dalam simpati dengan suatu sumber vibrasi. Seperti terlihat dibawah ini, kondisi resonan akan terjadi setiap waktu setiap gelombang kontinyu diteruskan ke dalam benda uji dan dipantulkan dalam fase dengan gelombang datang.

Resonance will occur only when the thickness of a specimen is equal to a half-wavelength or an exact multiple of half –wave length. Shown below is a “Fundamental Frequency” and multiples called “Harmonics”.

Resonansi akan terjadi bilamana ketebalan benda uji sama dengan ½ λ atau kelipatan dari ½ λ. Seperti terlihat dibawah ini bahwa “frekwensi fundamental” dan kelipoatan disebut “harmonis”.

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Ultrasonic units using the principle of resonance were commonly used for thickness measurement and bond or lamination inspection. However, pulse-echo units have been refined to perform most of these functions and resonant instruments are rarely used.

Peralatan ultrasonic menggunakan prinsip resonansi yang umum digunakan untuk mengukur ketebalan dan lapisan atau pemeriksaan laminasi. Bagaimanapun juga, peralatan pulsa echo telah disaring untuk melakukan fungsi yang paling umum dan peralatan resonan jarang dipergunakan. Resonansi terjadi bilamana ketebalan material sama dengan ½ λ atau kelipatannya. Panjang gelombang dapat diubah oleh variasi frekwensi. Frekwensi resonan fundamental adalah frekwensi terendah dimana benda uji akan bergetar.

Resonance occurs when the material thickness is equal to a half-wavelength or exact multiples. The wavelength can be changed by varying the frequency. The fundamental resonant frequency is the lowest frequency at which a specimen will resonate. Harmonics are exact multiples of the Harmonic adalah kelipatan dari minimum frekwensi resonan fundamental. Frekwensi fundamental (minimum) resonant frequency. The fundamental resonant frequency can be resonan fundamental dapat ditemukan dengan: found by:

F=

V 2T

F = fundamental resonant frequency V = velocity of longitudinal wave T = thickness of material

As shown above in “A”, the frequency has been adjusted until a standing wave “resonance” has been established. If the transducer is moved to position “B”, the material will stop resonating until the frequency (wavelength) is adjusted to again establish resonance as shown. Rev. 00

Seperti pada posis “A” diatas, frekwensi telah diatur sampai standing wave “resonansi” terbentuk. Jika transduser digeser ke posisi “B”, material akan berhenti bergetar sampai frekwensi (panjang gelombang) diatur untuk membentuk kembali resonansi seperti diatas. Prepared by Arif-010308

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UT LESSON 6 WORKSHEET #1 A. Using the information given below, solve the problems relating to "reflection factors." B The chart below Iists the common impedance values. Impedance Velocity Density Material 2 (gram/cm -sec) (cm/sec) (gram/cm3) Air 0.000033 x 106 0.33 x 105 0.001 6 Water 0.149 x 10 1.49 x 105 1.00 Aluminium 1.72 x 106 6.35 x 105 2.71 6 Steel 4.56 x 10 5.85 x 105 7.8

⎛ Z − Z2 C. reflection factor = ⎜⎜ 1 ⎝ Z1 + Z 2

⎞ ⎟⎟ ⎠

2

Z = acoustic impedance 71%

1. What percentage of the original sound energy will be reflected back to the probe at the water to aluminium interface? (SHOW WORK) (3 pts)

6%

2. What percentage of the original sound energy will finally enter the water on its way back to the transducer from the back surface of the aluminium part? (SHOW WORK) (3 pts) Only consider the reflection factors, do not consider the normal attenuation that would occur in the material itself.

27%

3. A clad material is to be tested for bond defects. One material has a thickness of 0.3 inches and an acoustic impedance of 5.0 x 106 gram/cm2 - second and the other material is 4.0 inches thick and has an acoustic impedance of 4.5 x 106 gram/cm2 - second. If the bond is perfect and acceptable, what percentage of sound would you expect to be reflected from the interface? (SHOW WORK) (3 pts)

thick

4. Would you inspect the bonded material through the thick side or through the thin side? Why? (2 pts)

5. On the CRT screen below, using a 5 inch screen range, sketch the approximate location and amplitude of the pips from an acceptable bond condition. (2 pts)

'As a general rule, "R" should be less than 20% for adequate bond inspection.

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UT LESSON 6 QUIZ T

1. The gradual loss of energy as a sound beam travels through a material is called attenuation.

F

2. Wherever possible, the UT inspection should be done in the "near zone" before the sound can spread out and attenuate.

T

3. "Acoustic Impedance" refers to resistance of sound propagation through a part.

F

4. Compared to steel, air has a very high acoustic impedance value.

F

5. The original ultrasonic velocity remains the same regardless of the media it is passing through.

T

6. A sound beam with a given energy will travel farther in aluminium than in steel before it is attenuated by the same amount.

T

7. A fine grained material will usually cause less attenuation than a coarse grained material.

F

8. The terms "intensity" and "Impedance" mean the same thing.

T

9. In immersion testing, it is typical that less than 1% of the original sound energy is returned to the transducer.

88%

10. Using the information given below, what would be the Reflection Factor at the interface shown between the water (Z1) and steel (Z2)? (SHOW WORK) (3 pts)

⎛ Z − Z2 reflection factor ( R ) = ⎜⎜ 1 ⎝ Z1 + Z 2

⎞ ⎟⎟ ⎠

2

Z = acoustic impedance

Material Air Water Aluminium Steel

Rev. 00

Impedance (gram/cm2-sec) 0.000033 x 106 0.149 x 106 1.72 x 106 4.56 x 106

Velocity (cm/sec) 0.33 x 105 1.49 x 105 6.35 x 105 5.85 x 105

Density (gram/cm3) 0.001 1.00 2.71 7.8

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Lesson 7 DISPLAYING ULTRASONIC INDICATIONS There are three basic types of visual displays which are commonly used to evaluate the soundness or quality of a material being tested; A-Scan, B-Scan, And C-Scan. A-Scan is a “time versus amplitude” display which reveals a discontinuity using a “Pip” on a cathode-ray tube (CRT).

Tampilan indikasi ultrasonic Terdapat tiga tipe dasar tampilan visual yang umum digunakan untuk mengevaluasi kemulusan atau kwalitas dari material yang sedang diperiksa: A-scan, B-scan, C-scan. A-scan adalah tampilan “amplitude” vs waktu yang memunculkan diskontinuiti menggunakan “pip” pada CRT.

The A-Scan presentation, as has been discussed, is read from left to right. The height of a pip can be compared to the height of a pip from a known reference reflector to give an indication of relative discontinuity size.

Tampilan A-scan, sebagaimana telah didiskusikan, dibaca dari kiri ke kanan. Tinggi pip dapat dibandingkan terhadap tinggi pip dari suatu reference reflector untuk memberikan indikasi dari ukuran diskontinuiti (relative)

B-Scan presentation, as shown below. Typically Tampilan B-scan, seperti pada gambar dibawah uses an oscillo scope screen to display a cross- ini menggunakan layer oscilloscope untuk menampilkan pandanagn melintang dari material sectional view of the material being tested. yang sedang diperiksa. The image is retained on the CRT long enough Bayangan ditahan pada CRT cukup lama untuk to evaluate the sample and to photograph the mengevaluasi sample dan untuk memotret layer untuk permanent record. screen for a permanent record.

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C-Scan is a”plan view” presentation similar to an X-ray picture. As shown below, the C-Scan shows the shape and location of the discontinuity, but does not show the depth.

C-scan adalah tampilan tampak atas dengan gambar sinar-X. Seperti pada gambar dibawah ini, C-scan memperlihatkan bentuk dan lokasi diskontinuiti, tetapi tidak memperlihatkan kedalamannya.

High speed ultrasonic scanning generally utilizes the C-Scan presentation. As shown below, some recorders use a chemically treated paper. The paper movement is synchronized with the movement of the transducer across the test surface.

Pada umumnya ultrasonic scanning yang sangat tinggi menggunakan tampilan C-scan. Seperti pada gambar dibawah ini, sebagian recorder menggunakan “chemically treated paper”. Gerakan kertas disinkronkan denga gerakan tranduser melintasi permukaan benda uji.

The advantage of the C-Scan is its speed and Kelebihan Rev. 00

C-scan

adalah

kecepatan

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dan

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ability to produce a permanent record.

kemampuan untuk menghasilkan permanent record. However, the scan shows only length and Bagaimanpun juga, C-scan hanya width, but not depth. memperlihatkan panjang dan lebar tetapi tidak kedalamannya.

A typical bridge/manipulator is shown for a Bidge/manipulator yang khas pada gambar ini umumnya digunakan untuk ultrasonic immersion basic ultrasonic immersion test. test. When a C-Scan is to be made, electric motors Bilamana peralatan C-scan dibuat, motor listrik are utilized to activate the traveling digunakan untuk menggerakkan mekanisme mechanisms and the up and down movement jalan dan gerakan naik – turun search tube. of the search tube.

A typical A-Scan presentation is shown below using contact testing with an angle beam transducer. The procedure used to calibrate the UT unit is similar to normal beam testing and requires a calibration block with a known size reflection surface at a known metal travel.

Rev. 00

Tampilan A-scan yang khas yang diperlihatkan dibawah ini menggunakan pengujian kontak dengan tranduser pancaran sudut. Procedure yang digunakan untuk mengkalibrasi peralatan UT sama dengan pengujian pancaran normal dan memerlukan blok kalibrasi yang memiliki ukuran reflector yang diketahui pada jarak tempuh yang diketahui. Prepared by Arif-010308

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A calibration block (IIW test block further discussed in lesson8) is shown below with a known distance of 4 inches to the curved surface. Using the sweep and delay controls, the pips are adjusted to show multiples of 4 inches on the CRT.

Blok kalibrasi (IIW) dengan jarak 4 inch terhadap permukaan lengkung. Gunakan control sweep dan delay, pip diatur sampai memunculkan kelipatan 4 inch pada CRT.

If the miniature angle beam calibration block Jika blok kalibrasi pancaran sudut miniature shown below were used to calibrate the above digunakan untuk mengkalibrasi tampilan CRT CRT screen, where would the pips appear? diatas, dimanakah pip akan muncul.

Depending on the direction of the angle beam probe, the pips would either appear at one, four, and seven inches or two, five, and eight inches. The Angle Beam Technique is often used for Weld Inspection as shown below.

Rev. 00

Tergantung pada arah probe pancaran sudut, pip akan muncul pada skala 1,4 dan 7 atau pada skala 2, 5 dan 8 inch. Teknik pancaran sudut sering digunakan untuk pemeriksaan lasan.

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Typically, the weld should be Inspected In The Umumnya lasan akan diperiksa pada leg 1 dan 2 1st Or 2nd Leg When. Ever possible as shown (bilamana mungkin). below.

To assist in Evaluating The Results of angle Untuk membantu evaluasi hasil pemeriksaan beam inspection, A Direct Reading Ultrasonic pancaran sudut, UT kalkulator umumnya Calculator is commonly used. digunakan

The Horizontal Scale across the top of the card represents the number of Inches Between The Transducer And The Center Of The Weld. The Vertical Scale represents Specimen Thickness and the arc shows the angle of The Sound Beam. The following is an Example of a typical angle beam inspection Using The Ultrasonic Calculator. A Double vee weld with an opening of 30 degrees in A 2” steel plate using a 60 degree shear wave in the specimen.

Rev. 00

Skala horizontal menunjukkan tranduser dan titik tengah lasan.

jarak

antara

Skala vertikal menunjukkan ketebalan specimen dan garis busur menunjukkan sudut dari pancaran suara. Berikut contoh penggunaan UT kalkulator pada pemeriksaan pancaran sudut. Lasan double vee dengan sudut kampuh 300, tebal plate 2”, menggunakan shear wave 600.

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The following procedure should be used in Setting Up The Calculator : 1. Draw a line representing the sound path from the upper left corner through the 60 degree mark on the arc, extending to the 2” point representing the plate thickness; calibrate the horizontal sweep of the CRT to represent beam travel distance in the material being tested. 2. To show the full skip distance of the sound beam, you then double the 3 7/16” and mark that point at approximately 6 7/8” (point “b” above) 3. Next. Draw the 30 degree vee weld on the plastic slide or transparent paper that slides back and forth over the calculator. 4. As Shown above, a discontinuity is displayed on the CRT screen at 5.5”. The operator then measures the distance between the center of the transducer (exit point) and the center of the weldment (4 5/8”) and slides the transparent paper to the same distance. 5. The position of the discontinuity is indicated and can be evaluated.

Rev. 00

Berikut prosedur untuk mengatur UT kalkulator: 1. gambar garis yang menunjukkan sound path dari sudut kiri atas ke titik 600 pada busur, diperpanjang sampai titik 2” yang menunjukkan ketebalan plate; kalibrasi horizontal sweep pada CRT untuk menunjukkan jarak perjalanan pancaran di dalam material yang diuji. 2. untuk menunjukkan full skip distance dari pancaran suara, panjangkan 3 7/16” dan tandai titik yang mendekati 3 7/8” (titik “b” diatas) 3. gambar kampuh v dengan sudut 300 di kertas transparan. 4. sepeti terlihat diatas, diskontinuiti ditampilkan di layar CRT pada 5.5”. Operator kemudian mengukur jarak antara transduser (exit point) dan titik tengah lasan (4 5/8”) dan kertas transparant pada jarak yang sama. 5. posisi diskontinuiti dapat diindikasikan dan dapat dievaluasi.

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LESSON 7 QUIZ F

1.

On a typical B-Scan, the horizontal sweep represents time and the vertical deflection represents amplitude.

T

2.

The B-Scan can display how deep the discontinuity is below the surface of the specimen.

F

3.

The typical A-Scan is the display commonly used for recording a permanent record with the immersion inspection technique.

T

4.

The vertical pip on an A-Scan can be used to compare the relative size of a discontinulty.

T

5.

The C-Scan display will indicate length and width of a discontinuity, but it cannot show depth.

F

6.

To obtain an A-Scan display with ultrasonic immersion testing, it is necessary to automate the bridge/manipulator with electric motors.

T

7.

The "Ultrasonic Calculator" can be used in weld inspection to indicate the location of a discontinuity in the weldment.

F

8.

Whenever possible, the weld should be inspected in the "2nd Skip Distance."

T

9.

The calibration of a UT instrument for sound path distance can be performed using the curved surface of the "IIW Block."

T

10. To accurately utilize the "Ultrasonic Calculator" it is necessary to accurately measure the distance from center line of the weld to the exilt point of the transducer. 11. Using an 8" screen range on the CRT below, indicate where the "pips" should appear if the instrument is to be properly calibrated for sound path distance in the block shown. (SHOW WORK) (3 pts)

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Lesson 8 ULTRASONIC TRANSDUCERS AND STANDARD REFERENCE BLOCKS. The Ultrasonic Transducers is the Heart Of The UT Test System.

Blok referensi standard dan transducer ultrasonic

The Cristal Material in ultrasonic transducers is made Piezoelectric Materials Such as Quartz, Lithium sulfate and polarized Germanics. 1. Quartz was the first material used. It has very stable frequency characteristics. However, Quartz is a poor generator of acoustic energy and has generally been replaced by more efficient materials. 2. Lithium Sulfate is a very effacement receiver of acoustic energy, but is fragile, soluble in water and limited to use at temperatures below 165ºF. 3. Polarized Ceramics Procedure the most efficient generators of acoustic energy but they do have a tendency to wear. Common polarized ceramics include barium titan ate, lead metaniobate, and lead zirconate/titanate. The Capability Of A Transducers is described by three terms : 1. Sensitivity – The Ability to defect small discontinuities. 2. Resolution – The ability to separate the sound reflections from two discontinuities close together in depth or time. 3. Efficiency – Energy conversion effectiveness. Sensitivity of transducers is rated by its ability to defect a certain size flat-bottom hole, at a specified depth, in a standard reference block.

Material kristal pada transducer ultrasonic terbuat dari material piezoelectric seperti Quartz, Lithium Sulfate, dan polarized ceramics. 1. Quartz adalah material yang paling pertama digunakan. Quartz memiliki karakteristik frekwensi yang stabil. Bagaimanapun juga quartz adalah penggerak energi akustik yang buruk dan umumnya telah digantikan 2. Lithium sulfate adalah penerima energi akustik yang sangat efisien, tetapi mudah pecah, dan larut dalam air dan terbatas pada temperature di bawah 73,90 C (1650F) 3. Polarized ceramics menghasilkan penggerak energi akustik yang sangat efisien tetapi mempunyai kecenderungan cepat aus. Polarized ceramics yang umum adalah barium titanate, lead metanobiate, dan lead zirconate titanate Kemampuan transducer diuraikan dengan 3 teminologi sebagai berikut : 1. Sensitifiti : kemampuan untuk mendeteksi discontinuity yang kecil 2. Resolusi : kemampuan untuk memisahkan pantulan suara dari dua discontinuity yang berkedekatan pada kedalaman yang sama. 3. Efisiensi : efektifitas konversi energi

The Smaller The detectable hole, The Greater The Sensitivity. Transducers Sensitivity Is Measured By The Amplitude Of Its Response from an artificial discontinuity in a standard reference block. The Reference block is necessary, because even Transducers of the same size, frequency Rev. 00

Sensitifiti dari transducer dirata – ratakan oleh kemampuannya untuk mendeteksi ukuran tertentu flat Bottom Hole, pada kedalaman tertentu, pada blok referensi standard. Makin kecil lubang yang dapat dideteksi, makin tinggi sensitifiti Sensitifiti transducer diukur oleh amplitude responnya dari discontinuity buatan pada blok referensi standard. Blok referensi sangat dibutuhkan, karena transducer dengan ukuran, frekwensi material Prepared by Arif-010308

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and material Do Not Always Procedure The yang sama tidak selalu menghasilkan sinyal Same Amplitude Signal form a given reflector. amplitude yang sama dari reflector yang sama.

Resolution is the ability to separate (Distinguish Between) The sun reflections from a discontinuity Close To A Boundary or Two Discontinuities Close Together In Depth Or Time.

Resolusi adalah kemampuan memisahkan pantulan suara dari diskontinuiti yang dekat dengan permukaan atau dua diskontinuiti yang berdekatan pada kedalaman yang sama.

Transducer Materials are usually in two ways :

Material transducer biasanya dipotong dalam dua cara : 1. Crystals cut perpendicular to the X-Axis 1. potongan kristal yang tegak lurus Procedure Longitudinal Waves. terhadap sumbu – X, menghasilkan gelombang longitudinal 2. potongan kristal yang tegak lurus 2. Crystals cut perpendicular to the Y-Axis terhadap sumbu – Y, menghasilkan Procedure Shear Waves. gelombang transversal As Shown below, Most Crystals used for UT Umumnya kristal yang dipergunakan dalam UT adalah potongan yang tegak lurus terhadap are cut perpendicular to the X-Axis. sumbu – X.

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Size is a contributing factor in performance of Ukuran adalah factor konstribusi dalam prestasi transducer transducers. 1. The Larger diameter the transducer, the less 1. makin besar diameter transducer makin kecil pancaran suara yang akan menyebar ( untuk the sound beam will spread for a given frekwensi yang sama) frequency. 2. However, The Small, High Frequency 2. Bagaimanapun juga transducer dengan frekwensi yang tinggi dan berdiameter kecil Transducers are better able to detect very lebih baik untuk mendeteksi diskontinuiti yang Small Discontinuities. sangat kecil 3. The Larger the transducers, The More 3. Makin besar transducer, makin banyak energi suara yang diteruskan kedalam benda uji. Sound Energy it transmits into the test part. Transducer dengan frekwensi rendah dan Large low frequency transducers are often berdiameter lebih besar digunakan untuk used to get More Information. penetrasi yang lebih dalam. 4. Large Single crystal transducers are 4. Transducer dengan kristal tunggal yang lebih besar umumnya terbatas untuk frekwensi lebih generally limited To the Lower rendah. Kristal frekwensi tinggi sensitif Frequencies. High frequency crystals are terhadap kerusakan karena sangat tipis. susceptible to damage because they are very thin. The Frequency of transducers is an important Frekwensi tranducer adalah factor penting dalam aplikasi factor in its application. 1. The Higher The Frequency of a transducer, 1. Makin tinggi frekwensi transducer makin kecil pancaran suara yang akan disebarkan dan the less the sound beam will spread and the makin besar resolusi dan sensitifiti. Greater the Sensitivity Resolution. Bilamana pancaran suara menyebar, makin When the Sound Is Spread as shown sedikit suara yang dipantulkan dari below, Less Sound Is Likely to be Reflected diskontinuiti yang kecil from a small discontinuity. 2. The Lower The Frequency, The Deeper the 2. Makin rendah frekwensi, makin dalam penetrasi suara dan semakin kecil sound Penetration And The Less Scatter. penyebaran. Penyebaran pancaran yang lebih The greater beam spread aids in detecting besar membantu dalam pendeteksian reflector reflectors which are not perpendicular to the yang tidak tegak lurus terhadap sumbu axis of the sound beam. pancaran suara. 3. Crystal Thickness is also Related To 3. Ketebalan kristal juga berhubungan dengan frekwensi transducer. Makin tinggi transducer, Transducers Frequency the Higher the makin tipis kristal. Pada umumnya UT Frequency of the transducer, the Thinner dilaksanakan pada frekwensi dari 0,2 MHz – the Crystal will be. 25 MHz dan potongan kristal untuk Most ultrasonic testing is done between 0.2 penggunaan diatas 10 MHz terlalu tipis dan MHz and 25 MHz and Crystals cut for uses mudah pecah dengan penujian kontak. above 1- MHz are too thin and fragile for contact testing. Oleh karena itu, transducer dengan frekwensi Therefore, Transducers with operating operasi diatas 10 MHz digunakan terutama frequencies above 10 MHz are used sekali pada immersion testing. primarily for immersion testing. Transducers for Contact Testing and Transducer untuk pengujian kontak, dan Immersion Testing are essentially the Same immersion pada umumnya sama tetapi biasanya tidak dapat saling tukar. but usually are Not Interchangeable. transducer pengujian kontak Most Contact Testing Transducers Have Umumnya Wear Plates in front of the piezoelectric element mempunyai pelat penahan aus di depan elemen to protect it. The Exception To This IS Quartz piezoelectric untuk melindunginya. Pengecualian terhadap ini adalah transducer quartz. Transducers. As shown below, Contact Transducers Can be Transducer kontak dapat berupa pancaran lurus atau sudut. either “Straight Beam” or “Angle Beam.”

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Straight Beam Transducers usually have a Lucite, ceramic, or quartz Wear Plate in front of the crystal. Angle beam transducers have the wear plate wedge-shaped to produce the desired refracted angle. As Shown above, The Lucite Wedge Protects the face Crystal and Determines the Angle Of Incidence of the sound beam of the test part. As Has been discussed, when Sound Waves are directed into the test part an angle, they are Divided Into Longitudinally and Shear Waves By Refraction. Most Angle Beam Testing Is Done With Shear Waves.

Transducer pancaran lurus biasanya mempunyai Lucite keramik atau pelat tahan aus Quartz pada bagian depan kristal. Transducer pancaran sudut mempunyai pelat wedge tahan aus untuk menghasilkan biasan susut yang diinginkan. Lucite Wedge melindungi muka kristal dan menentukan sudut datang pancaran suara pada permukaan benda uji. Bilamana gelombang suara diarahkan kedalam benda uji pada suatu sudut, akan terbagi menjadi gelombang longitudinal dan transversal karena pembiasan. Pada umumnya pengujian pancaran sudut dillakukan dengan gelombang transversal.

Probe pancaran sudut juga dapat digunakan untuk menggerakkan gelombang permukaan. Sebagaimana telah didiskusikan, gelombang permukaan dibangkitkan bilamana sudut datang dari pancaran suara mencapai titik kritis kedua, atau melewatinya. Pada umumnya kontak kontak transducer pancaran sudut diidentifikasi oleh pembiasan gelombang transversal yang dihasilkan (700, 600, DST), pada material khusus umumnya steel dan aluminium. Spherically group and cylindrically group Lensa akustik yang terbentuk sperikal dan acoustical lenses are commonly added to silindris yang paling umum diterapkan pada tipe immersion type transducers. They are used to: transducer immersion digunakan untuk tujuan sebagai berikut: 1. Improve sensitivity and resolution 1. Memperbaiki sensitivity dan resolusi The angle beam probe can also be used to generate surface waves. As we have discussed, surface waves are generated when then incident angle of the sound beam reaches the second or upper critical angle. Most angle beam contact transducers are identified by the refracted shear wave produced (70º, 60 º, etc), in a specific material, usually steel and aluminum.

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2. Compensate for test part contours 3. Examine a given depth of the test part more carefully. As shown below, cylindrically ground lenses focus the sound energy to a line. Spherically ground lenses focus the sound energy to a point.

2. Kompensasi bagian keliling benda uji 3. Memeriksa pada kedalaman tertentu dengan lebih teliti. Seperti terlihat di bawah ini, lensa silindris memfokuskan energi suara pada suatu garis. Lensa sperikal memfokuskan energi suara pada suatu titik.

Lensa silindris digunakan dalam dua cara: Cylindrical lenses are used in two ways: 1. To increase the sensitivity and resolution 1. Meningkatkan sensitifiti dan resolusi peralatan of equipment. 2. For contour correction as shown below. 2. Untuk koreksi keliling seperti pada gambar di bawah ini. Lensa dapat dibuat khusus untuk The lens can be ground specially to direct mengarahkan energi suara secara normal the sound energy normal (perpendicular) to (tegak lurus) terhadap permukaan lengkung a curved surface at all points. pada semua titik.

Spherical lenses concentrate the sound energy Lensa spherical mengkonsentrasikan energi suara ke dalam pancaran yang berbentuk into a cone shaped beam. kerucut. 1. The focusing increases its intensity, but 1. Fokus berarti meningkatkan intensitas tetapi memperpendek jangkauannya. shortens its useful range. 2. While the cylindrical lens above has a 2. Sementara itu lensa silindris mempunyai lebar yang lebih besar, lensa spirikal greater width, the spherical lens has the mempunyai sensitifiti yang terbesar. greatest sensitivity. 3. The spherical lens is often used when 3. Lensa sperikal sering digunakan bilamana ingin memeriksa benda uji yang immersion testing parts having a rough Rev. 00

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surface. Focused transducers are described by their focal length. The short focal lengths are for examining, areas of the specimen close to the surface. Longer focal lengths are for increasingly deeper areas. Transducers come in many shapes, sizes and physical characteristics. Some common types include paint-brush, dual element, single element, angle beam, focused, mosaic, contact, and immersion. Single element transducers may be transmitters only, receivers only, or both transmitter and receiver. Double element transducers (as shown below) may be either single transducer mounted side by side or stacked. In a double element transducer, one is a transmitter and the other a receiver.

berpermukaan kasar dengan teknik immersion. Transducer focus digambarkan oleh panjang vokalnya (titik api) Panjang fokal yang pendek digunakan untuk memeriksa bagian benda uji yang dekat ke permukaan. Panjang fokal lebih panjang bertujuan untuk menaikkan kedalaman kemampuan pemeriksaan. Transducer terdapat dalam beberapa bentuk, ukuran dan karakteristik fisik. Sebagian tipe yang umum termasuk paint – brush, dual element, single element, angle beam focus, kontak dan immersion. Single elemen transducer dapat hanya sebagai penerus saja atau penerima saja, atau kedua – duanya. Double element transducer dapat berupa single transducer yang dipasang berpasangan atau bersisisihan atau segaris (stacked). Satu sebagai transmitter dan yang lainnya sebagai receiver.

Double element transducers have better near surface resolution because the receiver can receive discontinuity signals before the transmitter completes its transmission.

Double element transducer mempunyai “near surface resolution” yang lebih baik, karena “receiver” dapat menerima sinyal discontinuity sebelum “transmitter” secara sempurna meneruskan suara.

Standard Reference Blocks In ultrasonic testing, discontinuities are usually compared to a reference standard. The standard may be one of many reference blocks or sets of blocks specified for a given test. Reference blocks come in many different shapes and sizes and this lesson will discuss only a few of those commonly used. A typical block is shown below.

Blok Referensi Standard Dalam ultrasonic testing, discontinuity biasanya dibandingkan terhadap suatu standard referensi. Standard dapat satu atau lebih atau terdiri ari satu set blok khusus untuk tujuan khusus.

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Most Reference Blocks have the following in Blok referensi pada umumnya mempunyai kriteria sebagai berikut. common: 1. terbuat dari material pilihan 1. They are made from carefully selected material. 2. material harus memiliki atenuasi, ukuran 2. The material must have the proper butiran perlakuan panas yang tepat dan attenuation, grain size, heat treatment and terbebas dari discontinuity be free of discontinuities. 3. semua dimensi harus dikerjakan dengan 3. All dimensions must be precisely mesin secara teliti machined. 4. semua lubang harus berbentuk flat 4. All holes must be flat-bottomed and have a bottomed dan mempunyai diameter yang specific diameter to be an ideal reflector. rinci sehingga ideal menjadi reflector 5. Side drilled hole diameter must be carefully 5. diameter “side drilled hole” harus dikontrol controlled. secara teliti. Three commonly used sets of standard reference blocks are: 1. Are amplitude blocks. 2. Distance amplitude blocks. 3. ASTM basic set of area and distance amplitude blocks. Area amplitude blocks provide standards for discontinuities of different sizes, at the same depth. Distance amplitude blocks provide standards for discontinuities of the same size at different depths. The ASTM basic set of area/distance amplitude blocks consists of ten, two inch diameter blocks as shown below:

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Set blok referensi standard yang umum terdiri dari tiga yaitu: 1. Area amplitude 2. Distance amplitude 3. ASTM (area dan distance amplitude) Blok area amplitude dilengkapi standard untuk diskontinuiti dengan ukuran yang berbeda – beda pada kedalaman yang sama. Blok distance amplitude melengkapi standard untuk discontinuity dengan ukuran yang sama pada kedalaman yang berbeda – beda. ASTM (Area / amplitude block) terdiri dari 10 block diameter 2 in, seperti pada gambar di bawah ini.

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Another type of calibration blocks is the IIW Blocks (International Institute If Welding). It provides the following: Verification of known distance & angular relationships verifies transducer angle and beam exit point and checks transducer resolution.

Tipe blok kalibrasi lainnya adalah blok IIW (International Institute of Welding) senagai berikut: Verifikasi hubungan sudut dan jarak. Verifikasi sudut probe sudut dan titik emisi (exit point) dan pengecekan solusi transducer.

In contact angle beam testing, the beam exit point of the transducer must be known to accurately determine the location of the discontinuity. As shown below, the transducer is moved back and forth until the pip on the CRT reaches maximum amplitude. The focal point on the IIW block then corresponds with the beam exit point of the transducer.

Pada pemeriksaan dengan pasangan sudut kontak exit point dari transducer harus diketahui untuk dapat menentukan lokasi discontinuity secara akurat. Seperti terlihat pada gambar di bawah ini transducer digerakkan maju mundur sampai amplitudo PIP maksimum pada CRT. Focal point pada blok IIW menjadi koresponden beam exit point dari transduser.

Special Calibration Standards Special standards are often used for items such as weldments, castings, and piping. The standards are normally of the same material and product form to be tested. Reference reflectors such as notches or holes are artificially added to the standard. Verification of the transducer angle is accomplished as shown below: The plastic wedge of the angle beam

Standard Kalibrasi Khusus Standard khusus sering digunakan untuk lasan, casting dan piping. Standard umumnya terbuat dari material dan bentuk produk yang sama dengan benda yang akan diuji. Reflektor referensi seperti notch atau hole adalha cacat buatan yang terdapat pada standard. Verifikasi sudut transducer dilakukan sebagai berikut: Plastik wedge dari transducer pancaran sudut

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transducer is subject to wear in normal use. sering mengalami keausan dalam pemakaian. This wear can change the beam exit point and Keausan ini dapat merubah exit point dan sudut the angle of the sound beam. pancaran suara.

From the position shown above, the transducer is moved back and forth until the reflection from the 2 inch hole shows maximum amplitude on the CRT. The angle of sound beam can then be read from where the exit point on the transducer matches the degrees stamped on the side of the block. The transducer sound beam exit point should always be checked first. If the exit point marking is not correct, then the angle check will not be accurate. The far field resolving power of the test equipment can be estimated by placing a normal beam transducer on the IIW block as shown. Good resolution will be indicated if the instrument can satisfactorily separate the pips from all three reflectors.

Dari posisi yang terlihat diatas, transducer digerakkan maju mundur sampai pantuln lubang berdiameter 2 in mencapai amplitude maksimum pada CRT. Sudut pancaran suara kemudian dapat dibaca dari exit point transducer terhadap sudut yang tertera pada sisi blok.

The miniature angle beam block can also be used to calibrate the instrument for angle beam inspection. The miniature block is intended for field work and is not as comprehensive as the larger IIW block.

Blok pancaran sudut miniatur juga dapat digunakan untuk mengkalibrasi instrument untuk pemeriksaan dengan pancaran sudut. Blok miniatur bertujuan untuk pemakaian di lapangan dan tidak seteliti blok IIW yang lebih besar.

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Exit point pancaran suara transducer harus selalu diperiksa setiap akan bekerja. Maka marking exit point tidak benar, mengakibatkan pengecekan sudut tidak akan benar. Daya pemisah “far field” dari peralatan dapat diperkirakan dengan menempatkan transducer pancaran normal pada blok IIW seperti pada gambar. Solusi yang baik akan terlihat jika instrument dapat memisahkan PIP dari tiga reflector secara jelas

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LESSON 8 QUIZ

F

1.

The term "resolution" refers to the ability of a transducer to detect a very small discontinuity.

F

2.

Quartz is the only transducer material commonly used that is not a piezoelectric material.

T

3.

If the frequency of a transducer is raised, then the beam spread is reduced.

T

4.

The polarized ceramic transducer is considered to be a very good generator of ultrasonic energy.

F

5.

Quartz is a type of polarized ceramic transducer material.

T

6.

A transducer that can detect a discontinuity close to the surface is said to have a good resolving power.

F

7.

Larger transducers usually have a higher frequency because they are more fragile.

T

8.

The higher the frequency of a transducer, the smaller the sound cone (i.e. less beam spread).

F

9.

Immersion testing is always done with transducers that have a frequency between 2.5 and 5.0 MHz.

T

10. Angle beam testing is usually done with longitudinal waves.

T

11. Angle beam probes may be used to generate surface waves.

F

12. A spherical focusing lens will usually have the ability to provide better sensitivity as compared to a cylinderlcal lens.

F

13. Focused transducers are often used for shear wave inspection of welded plate due to the increased penetration.

T

14. A double or dual element transducer can only be used in the longitudinal wave mode.

T

15. With a double element transducer the sensitivity is increased because both elements are receiving and sending sound energy.

T

16. Acoustical lenses increase transducer sensitivity and resolution, but decrease their useful range.

T

17. A reference block should be made from the same basic material as the part being tested.

T

18. Blocks which provide a size reference end are used to check the system's linearity are known as area amplitude blocks.

T

19. The exit point of an angle beam transducer should always be determined before the angle of the transducer is checked.

F

20. Both the IIW block and miniature block wlll check the test system resolution.

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Lesson 9 Pemeriksaan Immersion (rendam) IMMERSION INSPECTION A typical immersion testing installation usually Instalasi pengujian immersion yang umum seperti pada gambar di bawah ini. includes the items shown below.

In contact testing, the angle imprinted on the Lucite wedge used in angle beam testing often indicates the angle of “Refraction” in a given material. However, in immersion testing, the angle shown by the angle indicator on the manipulator is the “Angle of incidence”. It is necessary to apply Snell’s law and calculate the angle of refraction in the test specimen.

Pada “kontak langsung” sudut yang tertera pada “Lucite Wedge” digunakan pada pengujian dengan pancaran sudut sering menunjukkan sudut “bias” pada material tertentu. Bagaimanapun juga, pada pemeriksaan immersion, sudut yang diperlihatkan oleh indicator sudut pada manipulator adalah sudut datang. Perlu aplikasi hokum Snellius dan menghitung sudut bias pada benda uji.

sin φ1 V1 = sin φ 2 V2 If the angle indicator showed the angle of refraction in the test specimen, It would be necessary to change the indicator each time a different material was inspected. Test frequencies-since the transducer does not come into contact with the test specimen in immersion testing, it is possible to use thinner crystals at higher ultrasonic frequencies. It is possible to use frequencies as high as 25 MHz and the range is usually from 2, 25 to 25 MHz The higher frequencies give the best resolution of small discontinuities. For an immersion testing application where a sharper than normal sound beam is required, a focused transducer should be used. The lens focuses the sound energy into a small, well-defined pattern as shown below. Rev. 00

Jika indikator sudut memperlihatkan sudut bias pada benda uji, indikator harus dirubah setap pemeriksaan material yang berbeda. Frekwensi pengujian selagi transducer tidak kontak dengan benda uji, memungkinkan menggunakan kristal yang lebih tipis pada frekwensi ultrasonic yang lebin tinggi. Memungkinkan menggunakan frekwensi setinggi 25 MHz dan rentangannya biasanya dari 2.25 MHZ sampai dengan 25 MHZ. Frekwensi yang lebih tinggi menghasilkan resolusi yang terbaik dari discontinuity kecil. Untuk aplikasi pengujian immersion dimana pancaran suara yang lebih tajam dibutuhkan, focused transducer harus digunakan. Lensa memfokuskan energi suara ke suatu diskontinuiti kecil. Prepared by Arif-010308

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The proper water path for a focused transducer can be determined as follows: Using a transducer with a focal length of 5 inches in water to focus the beam to a point 0,25 inches below the surface of a steel part, one would determine the water path distance by:

Water path untuk focused transducer dapat ditentukan sebagai: Focal length = 5 inch dalam air Titik fokus = 0.25 inch dibawah permukaan steel

A. Dividing the velocity of steel by the velocity of the water.

6.0 x10 5 cm / sec =4 1.5 x10 5 cm / sec B. Multiplying the desired focal depth by the answer. 4 x 0.25” = 1” C. Subtracting answer from known focal length in water. 5” – 1” = 4” D. Thus, the water path distance must be 4” to focus the beam at, 0.25” below the surface. A special application of immersion testing is Aplikasi khusus immersion the “Bubbler” or “ Squirter” as shown below. “bubbler” atau “squirter”.

testing

adalah

Both straight and angle beam techniques can Baik teknik pancaran sudut maupun lurus dapat be used with this process depending on the digunakan dengan proses ini dan tergantung bubbler design. kepada desain bubbler. Rev. 00

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An advantage of the bubbler is that no immersion tank is required. A technique similar to the bubbler is used in contact testing and utilizes an “Irrigated Search Unit”. The couplant (water) can be fed to the test surface through a series of holes in a plastic block. The following show a typical straight beam immersion operation with the CRT indication that would be received.

Kelebihan bubbler adalah tidak memerlukan tank.

The water path distance from the transducer to the front surface of the test part is generally set to be longer in time than the metal part time from the front to rear of the test specimen. If the transducer is too close to the front surface of the test part the second front reflection will appear on the CRT between the front and back surface reflections. This reflection may appear to be a discontinuity.

Jarak “water path” dari transducer ke permukaan benda uji umumnya diset lebih lama (dalam waktu) daripada waktu dalam benda uji

Teknik yang sama dengan bubbler digunakan pada kontak langsung dan menggunakan suatu “irrigated search unit”. Couplant (air) dapat diaplikasikan pada permukaan benda uji melalui suatu seri lubang dalam blok plastik. Di bawah ini adalah pengoperasian pancaran lurus immersion yang umum dengan indikasi CRT yang akan menerima respon sebagai berikut.

Jika transducer terlalu dekat ke permukaan benda uji, pantulan permukaan uji yang kedua akan muncul pada CRT diantara pantulan pada permukaan dan belakang benda uji. Pantulan ini dapat muncul sebagai diskontinuiti.

The velocity of sound in water is about ¼ that Velocity suara dalam air ¼ velocity atau steel. of aluminum or steel. One inch of water will Satu inch air akan memunculkan rentang waktu appear on the CRT in the same time span on the yang sama dengan 4 inch steel pada CRT. Rev. 00

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sweep as 4 inches of steel. Therefore, a rule of thumb is – use at least one inch of water path for each four inches of metal path, plus ¼ “. Angle beam testing with immersion techniques is illustrated below:

Oleh karena itu, sebagai petunjuk praktis, satu inch air (water path) sama dengan 4 inch metal tambah ¼ inch. Teknik immersion dengan pancaran sudut digambarkan di bawah ini:

Pengujian dengan pancaran sudut hanya indikasi permukaan yang kecil akan muncul (jika ada) karena sebagian suara dipantulkan dari permukaan benda uji jauh dari transducer. “Ingat” gelombang transversal tidak akan merambat dalam air. Dengan teknik immersion, C-Scan umumnya digunakan untuk menampilkan bentuk dan ukurannya diskontinuiti. Seperti terlihat pada gambar di bawah ini. When a defect is found on the C-Scan, it is Bilamana defect ditemukan pada C-scan, possible to go back and manually determine its memungkinkan untuk kembali dan kedalamannya di bawah permukaan ditentukan secara manual. depth below the surface. With angle beam testing, only a small surface indication, if any, will result because most of the sound is reflected from the part surface away from the transducer. Remember, that shear waves will not propagate in water. With immersion testing a C-Scan is commonly used to display the shape and relative size of a discontinuity as shown below.

Determining the position of a discontinuity in the specimen with immersion testing is shown below. If the sound beam is striking the surface at an angle, refraction of the sound has to be taken into consideration.

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Cara menentukan posisi diskontinuiti dalam spesimen dengan menggunakan pmeriksaan immersion seperti berikut: Bila pancaran suara menabrak permukaan pada suatu sudut, pantulan suara harus menjadi pertimbangan

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The point at which the sound beam strikes the surface can be determined by placing a straight edged piece of metal “Metal Spoon” on the surface (A 6” Steel ruler can be used). As soon as the leading edge of the metal spoon enters the sound beam an indication will appear on the CRT. The same check is then performed from the other 3 sides, and this locates the are in which the sound enters the specimen. Conventional methods of identifying the location of the discontinuity can be used, such a utilizing the ultrasonic calculator or similar techniques. Remember that plate waves can be produced in immersion testing but shear waves will not propagate in water. Although shear waves and plate waves will not propagate in liquids, both modes can be used. In immersion testing because the sonic energy is transmitted through the water as longitudinal waves. The longitudinal waves are mode converted to shear or plate wave is more converted back to longitudinal waves, which then propagate to the transducer through the liquid couplant. Immersion testing techniques are commonly used for the inspection of thin and thick wall tubing and pipe as shown below.

Titik dimana pancaran menabrak permukaan dapat ditentukan dengan menempatkan sudut metal “Metal Spoon” pada permukaan Ujung metal spoon yang masuk ke pancaran suara akan muncul di layar CRT. Pengecekan yang sama dilakukan pada 3 sisi lain, dimana pancaran masuk ke spesimen. Metode konvensional untuk mengindetifikasi lokasi diskontinuiti bisa digunakan, seperti UT kalkulator atau sejenisnya. Ingat plate waves bisa dihasilkan dengan pemeriksaan immersion tetapi shear waves tidak dapat terjadi didalam air. Walaupun shear waves dan plate waves tidak bisa terjadi di dalam cairan, kedua mode tersebut bisa digunakan. Karena dalam pemeriksaan immersion hanya energi suara dalam bentuk longitudinal yang bisa ditransmisikan. Longitudinal wave diubah ke shear wave atau plate wave dan diubah lagi dalam bentuk longitudinal wave, dengan couplant cairan. Teknik pengujian immersion umumnya digunakan untuk pemeriksaan tubing dan pipa yang tipis dan tebal.

Immersion techniques can also be used to Teknik immersion juga dapat digunakan untuk inspect butt welds shown below. memeriksa Butt Weld seperti terlihat pada gambar di bawah ini.

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UT LESSON 9 WORKSHEET #1 4”

1.

What would be the correct water path distance to focus a transducer 1/2" below the surface of the steel part? (SHOW WORK) (3 pts) GIVEN: Focal length of transducer in water = 6 inches Velocity of sound in water = 1.5 x 105 CM/SEC Veloclty of sound in steel = 6.0 x 105 CM/SEC

1

2.

For aluminuim and steel metals the basic rule in determining the water path distance is that it should be "equal to 1/4 the part thickness plus 1/4 inch." Wlth this rule in mind what water path distance would you select to inspect a part that is 6 inches thick?

3.

Indicate by letter which pips on the CRT below would actually be seen with the immersion test as shown. Do not consider amplitude.

A–D

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A

Surface # 1

D

Surface # 2

F

Surface # 3

H

Surface # 4

4.

The water path distance is indicated between which two pips above? (2 pts)

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UT LESSON 9 QUIZ

T

1.

A focused transducer has better resolving power than a conventional transducer.

T

2.

The front surface reflection may be used in immersion testing to determine if the sound beam is perpendicular to the test part.

F

3.

A "metal spoon" is used in immersion testing to determine the maximum initial pulse amplitude.

T

4.

Longitudinal waves can be used for immersion testing of cylindrically-shaped specimens.

T

5.

Shear waves can be used for immerslon testing of cylindrically-shaped specimens.

F

6.

lmmersion testing with shear waves produces a high amplitude front surface reflection that must be swept off the CRT.

T

7.

Immersion testing with surface waves is commonly used to detect surface cracks.

T

8.

The angle of the manipulator on the immersion tank indicates the "angle of incidence."

T

9.

The shorter the wavelength, the smaller the defect that can be found.

F

10. With immersion testing, mode conversion occurs when the sound leaves the transducer and enters the water.

F

11. The basic rule in determining the water path distance when inspecting steel or aluminium is that it should be equal to 4 times the part thickness plus 1/4 inch. 12. Indicate by letter, which pip on the CRT would actually be seen with the immersion test as shown below. Do not consider amplitude.

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A

Surface # 1

F

Surface # 3

D

Surface # 2

G

Surface # 4

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Lesson 10 Pengujian Kontak Ultrasonic ULTRASONIC CONTACT TESTING transmisi langsung Through transmission testing usually uses the Pengujian menggunakan “PITCH CATCH” pitch-catch technique as shown below:

When using through transmission, the CRT indication decreases when more sound energy is intercepted by a discontinuity. Total reflection of sound energy at an internal reflector will result in no energy being receiver by the receiving transducer. Through transmission has certain advantages: 1. Better near surface detection – defects that are only a few thousandths of an inch below the surface can be detected effectively. 2. Capability of testing thicker test specimens (less attenuation). However, a through transmission technique cannot “See” the discontinuity. It only shows a loss of sound energy. If the transmitted pulse and received pulse are of the same relative height on the CRT, it can be assumed the specimen is sound a there is no significant attenuation in the material. In contact testing, it is possible to use sound beams that: 1. Are perpendicular to the test surface. 2. Propagate into the specimen at an angle. 3. Propagate along the surface of the specimen. 4. Propagate through the material from one side to the other. The determination of the proper equipment to use depends on several factors including:

1. Nature,

size, and orientation of discontinuities. 2. Surface condition and shape of the test specimen. 3. Internal structure (coarse grained or fine grained). Rev. 00

biasanya

Bilamana teknik transmisi digunakan, indikasi CRT menurun bila energi suara lebih banyak ditangkap oleh diskontinuity. Total pantulan energi suara dari reflektor akan mengakibatkan tidak ada energi yang akan diterima oleh receiver. Transmisi langsung mempunyai kelebihan: 1. Near surface detection yang lebih baik. Defect yang posisinya 1/1000 inch dibawah permukaan dapat dideteksi secara efektif. 2. mampu menguji material yang lebih tebal (atenuasi lebih kecil) Bagaimanapun juga teknik transmisi langsung tidak dapat melihat diskontinuiti. Teknik ini hanya memperlihatkan kehilangan energi suara Jika pulsa yang diteruskan sama dengan pulsa yang diterima (relative sama tinggi) pada CRT. Dapat diperkirakan bahwa benda uji tersebut mulus dan tidak atenuasi yang nyata dalam material. Pada kontak langsung memungkinkan menggunakan pancaran suara bilamana: 1. Tegak lurus terhadap benda uji 2. Merambt ke dalam benda uji pada suatu sudut. 3. merambat sepanjang permukaan benda uji 4. Merambat melalui material dari satu sisi ke sisi lainnya. Penentuan penggunaan peralatan yang tepat tergantung kepada beberapa factor sebagai berikut. 1. Orientasi, ukuran dan bentuk diskontinuiti 2. kondisi permukaan dan bentuk benda uji 3. Struktur material (coarse/fine grained) Prepared by Arif-010308

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It is usually desirable to test at the lowest frequency that will locate specified minimumsize discontinuities. Listed below are frequency ranges and test applications that are commonly used.

Frequency Range 200 Khz – 1 Hhz 400 Khz – 5 Mhz 200 Khz – 2.25 Mhz 1 – 5 Mhz 2.25 – 10 Mhz 1 – 10 Mhz 2.25 – 10 Mhz 1 – 2.25 Mhz 1 – 10 Mhz

Biasanya lebih disukai pengujian dengan frekwensi rendah yang mana akan mencari ukuran diskontinuti minimum. Tabel di bawah ini adalah rentangan frekwensi dan aplikasi pengujian yang biasanya digunakan.

Test Applications Casting: gray iron, nodular iron, and relatively coarse grained materials, suc as copper and stainless steels. Casting: steel, aluminium, brass, and other materials with refined grain size. Plastics and plastic-like materials, such as solid rocket propelllants and powder grains. Rolled products: metallic sheet, plate, bars, and billets. Drawn and extruded products: bars, tubes,and shapes. Forgings. Glass and ceramics. Welds. Maintenance inspection, especially fatique cracks.

A low test frequency is required to test a Pengujian dengan frekwensi lebih rendah untuk menguji material yang specimen that has a coarse grained internal diperlukan mempunyai struktur bagian dalam yang coarse structure, such as a casting. grained, seperti casting. A surface that is rough or pitted with Permukaan yang kasar atau pitting (korosi) juga corrosion will also require low frequencies to akan memerlukan frekwensi lebih rendah untuk memberikan sensitifiti yang lebih baik. give proper sensitivity. Sometimes it is possible to sand or grind the Kadang – kadang memungkinkan mengamplas surface of the specimen to obtain better atau menggerinda permukaan benda uji untuk mendapatkan kontak transduser yang lebih baik. transducer contact. A high test frequency is often used for fine Pengujian dengan frekwensi tinggi sering grained materials because the lower frequency digunakan pada material fine grained karena frekwensi lebih rendah tidak akan mendeteksi will not detect the desired discontinuity. diskontinuiti yang diinginkan. At higher frequencies, the wavelength is Pada frekwensi yang lebih tinggi, panjang gelombangnya pendek yang berhubungan dengan short in relation to the grain size. grain size. Considerations: Pertimbangan: 1. A higher frequency will provide the greatest 1. frekwensi lebih tinggi akan menghasilkan sensitivity for detecting small defects. sensitifiti tertinggi untuk pendeteksian defect kecil. 2. A lower frequency will give greater power to 2. frekwensi lebih rendah akan memberikan penetrate more deeply. kemampuan yang lebih dalam. 3. tranduser dengan diameter besar akan 3. A larger diameter transducer my be required diperlukan untuk material yang lebih tebal. when testing thicker materials. 4. pada setiap frekwensi, makin besar kristal, 4. At any frequency, the larger the crystal, the makin lurus pancaran. straighter the beam. 5. untuk tranduser dengan diameter tertentu 5. For a transducer of a given diameter, there penyebaran pancaran makin kecil pada is less beam spread at higher frequencies. frekwensi lebih tinggi. Jika ingin memeriksa bar yang panjang If you were inspecting a long bar through its (panjangnya 8 kaki), tranduser manakah yang length (8 FT), which of the following would you Rev. 00

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select? ½” – 5 MHz, or ½” – 2,25 MHz, or 1” – 2,25 MHz, or 1” – 5 MHz

akan dipilih? ½” – 5 Mhz, ½” – 2.25 Mhz, 1” – 2.25 Mhz, 1” – 5 Mhz.

The 1” – 2, 25 MHz would be the best choice. Before making an ultrasonic test, be sure the instrument is operating properly, check the instrument on a standard in accordance with the operating manual. Before conducting a test, you should have a clear idea, of the kind, orientation, and quantity of discontinuities you are trying to detect. If the rear surface of the specimen lies at an angle as shown below, what will be the effect on a normal A-Scan display?

Sebelum melakukan ultrasonic testing, yakinkan instrument beroperasi sebagaimana mestinya, cek instrument pada standard sesuai dengan “operating manual”. Sebelum melakukan pengujian, teknisi harus mempunyai gambaran dari jenis, orientasi, dan jumlah diskontinuiti yang akan dideteksi. Jika permukaan belakang benda uji tidak pararel/sejajar dengan permukaan, akan mempengaruhi tampilan pada A-scan.

Although a discontinuity may be detected, there will not be a back surface reflection in the situation above. Selection of the proper transducer is very important in obtaining a good ultrasonic test. As shown below, a transducer with a plastic wedge may be necessary to look into a specimen at an angle.

Sekalipun diskontinuiti dapat dideteksi, tidak akan ada pantulan back wall.

The pulse length used will affect the ability of the instrument to locate discontinuities near the surface as shown below.

Pulse length yang digunakan akan mempengaruhi kemampuan instrument untuk menemukan diskontinuiti dekat ke permukaan seperti pada gambar dibawah ini. Pulsa lebih lama dapat menghalangi receiver selama periode transmisi dan mengaburkan pantulan dari diskontinuiti. Transducer dapat terus bergetar di luar waktu

A longer pulse may block the receiver during the period of transmission and obscure reflections from the discontinuity. The transducer may continue vibrating Rev. 00

Pemilihan tranduser yang penting sekali dalam pengujian ultrasonic. Seperti pada gambar dibawah ini, tranduser dengan plastic wedge diperlukan untuk mendeteksi benda uji pada suatu sudut.

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beyond the time the discontinuity energy is received.

energi diskontinuiti diterima.

In angle beam contact testing, the transducer is placed behind a wedge, usually Lucite, so that the sound will be introduced into the part at an angle. As shown below, the angle of incidence of the sound beam at the surface is determined by the fixed angle of the wedge.

Pada pemeriksaan kontak pancaran sudut, transducer ditempatkan di belakang wedge, biasanya Lucite, sehingga suara akan diteruskan ke dalam benda uji pada suatu sudut. Seperti gambar di bawah ini, sudut datang dari pancaran suara pada permukaan ditentukan oleh sudut dari wedge.

As discussed previously, the sound beam angle in a test part is determined by the relationship of the velocity of sound in the test specimen and the velocity of sound in the wedge. This relationship is known as “Snell’s Law”. As shown below, when the angle of incidence increases, refraction of the longitudinal wave increases until there comes a point where total reflection of this wave occurs, and all that is left is a shear wave. This point is called the 1ST critical angle of incidence.

Sebagaimana telah dijelaskan sebelumnya, sudut pancaran suara pada benda uji ditentukan oleh hubungan antara velocity pada benda uji dan velocity pada wedge. Hubungan in dikenal dengan hukum Snellius (Snell’s Law) Seperti terlihat pada gambar di bawah ini, bilamana sudut datang naik, pembiasan gelombang longitudinal akan naik sampi mencapai suatu titik dimana gelombang ini akan dipantulkan secara sempurna, dan akhirnya tetinggal hanya gelombang transversal. Titik ini disebut “sudut datang kritis pertama”

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To produce a sound beam at a given angle, it is necessary to know only the following three factors to determine the proper wedge angle: 1. The angle desired in the test specimen. 2. The longitudinal velocity in the wedge. 3. The velocity in the test material (shear or longitudinal, depending on the sound beam desired).

Untuk menghasilkan pancaran suara pada suatu sudut perlu mengetahui tiga factor yang menentukan sudut wedge yang tepat: 1. Sudut yang diinginkan pada benda uji 2. Velocity longitudinal pada wedge 3. velocity pada benda uji (longitudinal atau transversal tergantung pada pancaran suara yang diinginkan)

In angle beam testing, the angle of refraction becomes less as the velocities of sound in the wedge and test specimen become more nearly equal. Only longitudinal waves will be produced in the wedge, but it is possible to have either longitudinal or shear waves in the test part.

Dalam pengujian pancaran sudut, sudut bias menjadi berkurang bilamana velocity dari suara pada wedge dan benda uji menjadi medndekati sama. Hanya gelombang longitudinal yang akan dihasilkan pada wedge tetapi hal ini berkemungkinan akan menghasilkan gelombang longitudinal atau gelombang transversal pada benda uji. Kedua metode ini dapat terjadi pada waktu yang bersamaan tergantung pada sudut wedge Chart berikut ini memperlihatkan amplitudo dan sudut secara relative untuk gelombang longitudinal dan gelombang transversal pada steel untuk suatu sudut wedge pada Lucite. Bilamana memilih suatu wedge disarankan untuk menghindari sudut yang menghasilkan gelombang longitudinal dn gelombang transversal pada waktu yang bersamaan dan pada intensitas yang sama. Kehadiran kedua gelombang tersebut akan mempersulit interpretasi layar CRT yang menampilkan pantulan kedua gelombang tersebut.

Both modes may be present at the same time depending on the angle of the wedge. The following charts show the relative angle and amplitude for both longitudinal and shear waves in steel for given wedge angles in Lucite. When choosing a wedge, it is desirable to avoid angles that produce both longitudinal and shear waves at the same time and at similar intensities. The presence of both waves makes it difficult to interpret the CRT screen which displays both reflections.

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example: 1. Assume that you have a Lucite wedge with an angle of 50 degrees, referring to the chart above, what angle shear waves will be produced in the test specimen? 2. What problem would be encountered using a 50 degree longitudinal wave? (#1 = about 65 degrees) (#2 = shear wave also exists).

Contoh: 1. asumsikan punya Lucite wedge dengan sudut 500, mengacu ke table diatas, berapa sudut shear wave yang akan dihasilkan pada specimen? 2. problem apa yang akan terjadi bila menggunakan 500 longitudinal wave? (#1 = 650) (#2 = shear wave juga ada)

In angle beam testing, when the wedge angle is increased to the point that the shear wave is equal to 90 degrees, we have what is known as the 2nd critical angle. However, sound energy still exists parallel to the interface and is known as “Surface waves” or “Rayleigh waves” as discussed previously.

Pada pemeriksaan pancaran sudut bilamana sudut wedge dinaikkan ke suatu titik yang menghasilkan gelombang transversal sama dengan 900. Titik ini disebut titik kritis kedua” Bagaimanapun juga, energi suara tetap parallel/sejajar terhadap interface dan dikenal sebagai” Gelombang permukaan “Rayleigh Wafe”

As shown on the chart on the previous page, a wedge angle of 63 degrees will produce

Seperti terlihat pada chart diatas, sudut wedge sebesar 630 akan menghasilkan gelombang

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surface waves of the greatest amplitude in steel. As shown below, the surface wave penetrates only one wave length below the surface and has the ability to follow the part contour. Any sharp angle on the surface will surface will cause a reflection.

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permukaan dari amplitudo terbesar pada steel. Seperti terlihat pada gambar dibawah ini, gelombang atau permukaan hanya menembus sedalam satu dibawah permukaan dan mempunyai kemampuan untuk mengikuti lengkungan benda uji. Setiap sudut yang tajam pada permukaan akan menyebabkan pantulan

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UT LESSON l0 \

WORKSHEET #1 A. Using the information given below, calculate the "Snell's Law" problems for each of the following.

SNELL ' S LAW :

sin φ1 V1 = sin φ 2 V2

Long.velocity in steel Shear velocity in steel Long.velocity in lucite Shear velocity in lucite

410

= 5.85 x 105 cm/sec = 3.23 x 105 cm/sec = 2.68 x 105 cm/sec = 1.26 x 105 cm/sec

1. Find the refracted shear wave if the incident angle is 33 degrees. (3 pts - SHOW

WORK)

460

2. If you wanted to produce a shear wave in steel at 60 degrees, what would be the

incident angle in lucite? (3 pts - SHOW WORK)

560

3. Above the 2nd Critical Angle, shear waves become surface waves. Determine the

angle of incidence when this starts to happen with interface of lucite to steel. (3 pts SHOW WORK)

360

4. Find the reflected longitudinal wave if the incident angle is 36 degrees. (3 pts SHOW

WORK)

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UT LESSON 10 WORKSHEET #2 A. Using Snell's Law, develop a chart for ALUMINUM that is similar to the one below that was designed for steel. B. Superimpose the lines of the aluminum longltudinai and shear waves over the exlstlng lines to show a comparison.

Longitudinal Velocity in Aluminium = 6.35 x 105 cm/sec Shear Veloclty In Alumlnum = 3.10 x 105 cm/sec Longitudinal Velocity in Lucite = 2.68 x 105 cm/sec C. From the newly formed lines on the graph, answer the following questions pertaining to the sound in the aluminium. (2 pts each) 370

1. With a transducer angle of 15 degrees, what is the longitudinal sound path in aluminium?

730

2. With a transducer wedge angle of 24 degrees, what is the longitudinal sound path in aluminium?

270

3. What transducer wedge angle would you use if you wanted a 30 degree shear wave angle in aluminium?

590

4. What transducer wedge angle would you use if you wanted a 80 degree shear wave angle in aluminium?

No

5. Would it be practical to use a wedge angle of 20 degrees to inspect aluminium? Why or why

not?

No

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6. Would it be practical to use a wedge angle of 60 degrees to inspect aluminium? Why or whynot?

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UT LESSON 10 QUIZ F

1.

Through transmission is often used because of its ability to indicate the depth of the discontinuity below the surface.

F

2.

Contact testing is often used in production line testing because it permits easy automatic scanning and recording.

T

3.

Contact testing can be used to generate both surface waves and longitudinal waves.

T

4.

At a point slightly above the second critical angle, a "Rayleigh" wave is produced.

T

5.

A low frequency is typically used to inspect a part that has a coarse grain structure.

F

6.

The first critical angle occurs when the shear wave is refracted at an angle parallel to the test part surface.

F

7.

When doing a typical angle beam test (e.g. 70 degrees), both longitudinal and shear waves exist in the part.

T

8.

Pulse-echo and through transmission techniques can both use the same type of transducer.

F

9.

A 1 megahertz transducer would probably result in a greater attenuation loss than a 5 megahertz transducer.

F

10. A major advantage of the through transmission technique is that no couplant is required.

T

11. To find small discontinuities, it is usually advisable to use as high a frequency transducer as possible.

T

12. A short pulse length will result in less penetrating power into the test part.

B

13. The critical angle for longitudinal waves is the point at which: a. the reflected angle is zero degrees. b. the refracted angle of the longitudinal wave mode is parallel to the surface. c. the longitudinal wave mode is totally reflected. d. both longitudinal and shear waves are transmitted into the specimen.

D

14. A large discontinuity found with the through transmission technique will cause the CRT 15. display to: a. increase in amplitude at a point equal to the depth of the defect. b. show a pip equal to the relative size of the discontinuity. c. show a decrease in reflected energy from the back surface of the part. d. show a decrease in energy at the receiving transducer.

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Lesson 11 APPLICATIONS OF CONTACT TESTING The lower ranges of frequencies are generally used to test castings since castings usually have a rather coarse grain structure. Many of the very coarse grained castings cannot be tested with ultrasonic’s. Most forgings are good objects for ultrasonic testing. Common discontinuities found in forgings are shown below.

Discontinuities in a forging are most likely to be detected if the inspection is made at. Right angles to the direction that the material was worked. Working will orient discontinuities in the same direction as the grain of the metal is oriented. Rolled sheet, and plate materials may be tested with either a straight beam or angle beam, depending on the specification requirements. Straight beam testing has the advantage of being able easily locate laminations. However, straight beam testing is time consuming and may not “See” discontinuities close to the surface, unless special techniques are used. The advantage of angle beam testing is that it is a very fast method of inspecting plate materials. Most types of discontinuities found in plate that are perpendicular to the scan surface will be found with angle beam testing. However, smooth laminations parallel to the surface will probably not be detected by angle beam testing.

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APLIKASI PENGUJIAN KONTAK Rentangan frekwensi yang lebih rendah umumnya digunakan untuk memeriksa casting selagi casting mempunyai struktur butiran kasar (coarse grain) Kebanyakan casting mempunyai butiran yang sangat kasar dan tidak dapat diperiksa dengan ultrasonic. Forging pada umumnya adalah baik diperiksa dengan ultrasonic. Diskontinuity yang umum ditemukan pada forging seperti pada gambar di bawah ini.

Diskontinuiti pada forging umumnya dapat dideteksi bilamana pemeriksaan dilakukan pada sudut yang tepat searah dengan pengerjaan material tersebut. Proses pengerjaan akan mengarahkan diskontinuiti dengan arah yang sama dengan orientasi butiran metal. Material pelat dengan sheet yang diroll dapat diperiksa dengan pancaran lurus atau pancaran sudut. Tergantung pada persyaratan spesifikasi. Pengujian pancaran lurus mempunyai kelebihan dalam pemeriksaan laminasi. Bagaimanapun juga pengujian pancaran lurus memakan waktu dan tidak dapat menemukan diskontinuity dekat ke permukaan kecuali dengan teknik khusus. Kelebihan pengujian pancaran sudut adalah sangat cepat untuk pengujian material pelat. Tipe diskontinuiti yang paling umum ditemukan pada pelat adalah diskontinuiti yag tegak lurus terhadap permukaan scanning. Bagaimanapun juga laminasi yang mulus dan parallel terhadap permukaan kemungkinan tidak akan terdeteksi oleh pengujian pancaran sudut.

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Before performing an angle beam test, the plate should be scanned with a straight beam transducer to find any gross defects or laminations. When an angle test is performed on plate, it is common to establish a “Reference” so that the amplitude of a discontinuity can be compared to a know size reflector. The following procedure explains one way this can be done: 1. Set up a “Reference notch” this is either 3% of the part thickness or 0,005” deep. 2. Place the transducer so that a signal from the notch is obtained on the first leg and adjust gain so that the signal is 100% screen height. 3. Move the transducer back so that a signal from the notch is obtained on the second leg and mark the signal height on the CRT with a grease pencil repeat this step at longer specific distances 4. When a discontinuity is found, move the transducer to one of the known distances and compare amplitude of discontinuity with notch. 5. The plate should then be scanned along each of the plate’s four edges. Discontinuities missed in one scan, should be picked up in another direction.

Sebelum melaksanakan pengujian dengan pancaran sudut pelat harus di scanning dengan transducer pancaran lurus untuk menemukan Gross defect atau laminasi Bilamana pengujian pelat dilakukan dengan pengujian sudut. Umumnya diperlukan suatu referensi sehingga amplitudo dari diskontinuity dibandingkan terhadap suatu reflektor. Berikut ini adalah adalah prosedur pemeriksaannya. 1. Buat “Reference Notch” yang kedalamannya 0,005 in atau 3% dari tebal. 2. Tempatkan transducer sehingga sinyal diperoleh dari Notch pada Leg 1 dan atur gain sampai sinyal mencapai 100% SH (screen height) 3. Geser transducer mundur sehingga sinyal dari Notch yang diperoleh berada pada Leg II dan tandai tinggi sinyal pada CRT dengan pensil warna ulangi langkah ini pada jarak yang lebih jauh. 4. Bilamana diskontinuity ditemukan, geser transducer ke suatu jarak yang telah diketahui dan bandingkan amplitudo diskontinuity dengan Notch. 5. Selanjutnya pelat harus di scanning sepanjang ke empat sisi pelat. Diskontinuiti yang tidak terdeteksi pada satu arah scan, harus dilakukan pada arah lainnya.

Contact testing of weldments can be accomplished by either straight beam or angle beam techniques, based on the type of defect to be detected. Straight beam testing requires that the surface of the weld be ground smooth as shown below. However, lacks of fusion, cracks, insufficient penetration are not easily detected with straight beam techniques.

Pengujian lasan dengan teknik kontak dapat dilakukan baik oleh teknik dan pancaran lurus ataupun teknik pancaran sudut, berdasarkan tipe defect yang akan dideteksi. Pengujian pancaran lurus mensyaratkan bahwa lasan digerinda mulus seperti pada gambar dibawah ini. Bagaimanapun juga, lack of fusion, crack, incomplete penetration tidak mudah dideteksi dengan teknik pancaran lurus.

Angle beam testing of weldments is done as shown in view “B” above.

Pengujian lasan dengan pancaran sudut dilakukan seperti diperlihatkan pada gambar “B” diatas. Untuk menscan lasan, transduser digerakkan maju mundur seperti terlihat pada gambar dibawah ini. Pada ½ skip distance, pancaran menabrak bagian bawah pelat dan pada 1 skip distance, pancaran

To scan the welded seam, it is necessary to move the transducer forward and backward as shown below. At ½ skip distance, the beam strikes the bottom of the plate and at 1 skip distance, the Rev. 00

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beam will strike the top of the plate as shown.

akan menabrak bagian muka pelat seperti terlihat pada gambar

Skip distance is determined by the angle of the sound entering the weldment, which is determined by the Lucite wedge angle. Once the skip distance is known, a chalk mark can be made on the part to show where the transducer must be moved for complete coverage of the weld zone. Beam angle selection is determined by: 1. Code or procedure requirements. 2. Weld joint design. 3. Specimen configuration. The following table shows example of favorable beam angles for testing welds in materials of varying thickness. As sheet thickness increases, beam angle should be decreased.

Skip distance ditentukan oleh sudut suara yang masuk ke Lasan. Yang ditentukan oleh Lucite wedge. Sekali skip distance diperoleh, penandaan diperlukan untuk memudahkan penggerakan transducer untuk pemeriksaan lasan.

Sheet thickness (inches) 0.2 – 0.6 0.6 – 1.2 1.2 – 2.4 Over 2.4 0.2 – 0.8 0.8 – 1.6 Over 1.6

Weld bead ground on both sides Beam engle (degrees) 80 70 60 45 Weld bead not removed 80 70 60

Example: The surface distance to a point directly above the discontinuity can be calculated according to the formula: D = S x (sin Ф)

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Pemilihan pancaran sudut ditentukan oleh: 1. Code atau persyaratan dari prosedur 2. Desain samungan las 3. Konfigurasi benda uji Tabel berikut ini memperlihatkan contoh – contoh pancaran sudut yang favorit untuk pengujian lasan pada ketebalan yang bervariasi. Bilamana tebal naik, maka pancaran sudut akan turun.

D = S = Ф =

Skip distance (inches) 2.2 – 6.6 3.2 – 6.6 4.2 – 8.4 4.8 and up 2.2 – 8.8 4.4 – 8.8 5.6 and up

Contoh : Surface distance terhadap titik yang berada diatas diskontinuiti dapat dihitung berdasarkan rumus:

surface distance sound path distance refracted sound beam angle

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Example: With a properly calibrated 70 degree probe, what is the distance “D” from the exit point of the probe to the discontinuity? Distance “S” shows on the CRT at 4,6” (do not consider the sound travel in the Lucite wedge). S x Sin Φ = .939 multiplied by sound path of 4, 6” equals A surface distance “D” of 4,332 inches. It is usually necessary to know the “Skip Distance “of the sound beam in a part with any given angle transducer. Skip distance can be found by using the following formula: P = 2 x tan Ф x T

P Ф T

Example : What is the skip distance on A 3/8 inch plate with A 70 degree transducer? P P P P

= = = =

D = S x (sin Ф) D = 4.6 x 0.939 D = 4.332 inch Biasanya perlu diketahui “skip distance” pancaran suara pada benda uji dengan transducer tertentu Skip distance dapat dihitung dengan rumus berikut: = = =

skip distance angle of sound in part tebal pelat

Contoh: Berapa skip distance dari pelat dengan tebal 3/8 inch dengan menggunakan sudut 700

2 x (tan Ф) x T 2 x (2.75) x 0.375” 5.5 x 0.375” 2.06”

Calibration procedure for the IIW block using angle beam transducers. 1. A 5 MHz straight beam transducer can be used to calibrate the instrument for angle beam inspection as shown below in view “A”. 2. Change to the proper angle beam transducer as shown in view “B” below and adjust only sweep delay to the 4” mark. This procedure eliminates errors in calculations due to sound travel in the angle beam wedge because the travel time in the wedge is delayed off the CRT.

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Contoh: Dengan menggunakan probe sudut 70. Berapa jarak “D” dari exit point probe ke diskontinuiti. Jarak “S” pada CRT adalah 4,6 in

Prosedur kalibrasi pada blok IIW dengan menggunakan transducer pancaran sudut. 1. Transducer pancaran lurus dengan frekwensi 5 MHZ dapat digunakan untuk mengkalibrasi instrument untuk pemeriksaan pancaran sudut seperti terlihat pada gambar “A” 2. Ganti dengan transducer pancaran sudut yang tepat seperti pada gambar “B” dibawah ini dan diatur dengan sweep delay sehingga pip pada 4 in. Prosedur ini menghindari kesalahan dalam perhitungan disebabkan oleh perjalanan suara pada wedge pancaran sudut, karena waktu perjalanan dalam wedge dihilangkan pada CRT

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Another method of calibrating the UT instrument for angle beam inspection involves using multiple echoes from the curved surface of the IIW block. 1. As shown in view “B” above, place the transducer on the block and adjust the instrument to get a pip on the CRT at exactly 4 and 8 inches. 2. Many IIW blocks have a notch that will reflect the sound in multiples of 4 inches. 3. The instrument is the adjusted to such a sensitivity level that reflections from the ,060 inch hole can be recognized on the CRT. The illustration below indicates what will happen to a sound beam that strikes the surface at an angle other than perpendicular.

Metode lainnya dari kalibrasi instrument UT untuk pemeriksaan pancaran sudut dengan menggunakan gema berganda dari permukaan lengkung blok IIW. 1. Seperti terlihat pada “B” diatas, tempatkan transduser pada blok dan atur instrument untuk mendapatkan pip pada CRT tepat pada 4 inch dan 8 inch. 2. blok IIW mempunyai notch akan memantulkan suara kelipatan dari 4 inch. 3. instrument diatur ke tingkat sensitifiti tertentu yang dipantulkan dari 0.060 inch hole.

Sound propagates around the wall in zigzag pattern as either longitudinal or shear waves. Because of the interference by shear waves when longitudinal waves are used, most testing of tubular shapes is done with shear waves.

Suara merambat sekitar dinding dengan pola zigzag baik gelombang longitudinal maupun gelombang transversal. Karena dipengaruhi oleh gelombang transversal bilamana gelombang longitudinal yang digunakan, pada umumnya pengujian bentuk – bentuk tubular dilakukan dengan gelombang transversal. Bilamana menggunakan gelombang transversal, jika rasio tebal (d) terhadap diameter (D) melebihi 0.2 atau 20%, defect pada sisi permukaan dalam tidak dapat diperiksa dengan gelombang transversal sudut 450, 600, atau 700 karena suara tidak akan menyentuh dinding sebelah dalam,

When using shear waves, if the ratio of thickness (d) to diameter (D) is over ,2 or 20%, you cannot test for inside diameter defects with a normal 45º, 60º, or 70º shear wave because the sound will not touch the inner wall, as shown below. Rev. 00

Gambar dibawah ini menunjukkan apa yang akan terjadi terhadap pancaran suara yang menabrak permukaan pada suatu sudut yang tidak tegak lurus.

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seperti terlihat pada gambar dibawah ini.

As shown below, shear waves bounce off the outer and inner surfaces of the pipe wall as they travel around the circumference. The sound waves will travel around the pipe until completely at attenuated.

The pip on the CRT screen above represents 360 degrees of sound travel and is often called the revolution indication. However, for measurement purposes this pip is referred to as being 180 degrees even though the distance covered to the notch and back represents one complete revolution. Assume that a practical situation exists and that a shear wave is being transmitted into a pipe in a clockwise direction as shown above. If discontinuities exist at points “A” and “B”, signals caused by this should appear on the CRT screen at points 6, 2 and 7, 5. Special transducers have been open with curved wear plates designed for specific diameter pipes. Some of these probes are designed with two transducers in one case, one scanning clockwise and the other counterclockwise.

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Seperti terlihat dibawah ini, gelombang transversal dipantulkan oleh dinding luar dan dinding dalam pipa sewaktu merambat disekelilingnya. Gelombang suara akan merambat disekeliling pipa sampai suara hilang sama sekali.

Pip pada layar CRT diatas menunjukkan suara merambat 3600 dan sering disebut indikasi revolusi. Bagaimanapun juga, untuk tujuan pengukuran pip ini dianggap sebagai 1800 meskipun jarak yang dicakup sampai ke notch dan kembali menunjukkan satu revolusi lengkap. Asumsikan bahwa dalam situasi kritis dan gelombang transversal diteruskan ke pipa searah dengan jarum jam seperti pada gambar diatas. Jika diskontinuiti terdapat pada titik “A” dan “B”, sinyal yang disebabkan oleh kasus ini akan muncul pada layer CRT pada titik 6.2 dan 7.5 Transducer khusus telah dikembangkan dengan pelat lengkung yang didesain untuk pipa dengan diameter khusus. Sebagian probe telah didesain dengan dua transducer pada satu kotak, yang satu scanning searah jarum jam dan lainnya berlawanan dengan arah jarum jam.

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UT LESSON 11 WORKSHEET # 1 A. Solve the following "Skip Distance" and "Surface Distance" problems based on the lnformation given in this lesson.

1.

What is the surface distance from the exit point of a 600 transducer to the point directly above the discontinuity if the sound path on the CRT screen shows 4 ½ inches? (3 pts) MAKE A SKETCH AND SHOW WORK

D = S (sin Ф) D = 4.5 (0.8660) D = 3.897” 2.

What is the "P" skip distance using a 600 transducer on 1 ½ inch thick material? (3 pts) MAKE A SKETCH AND SHOW WORK

P = 2 x tan Ф x T P = 2 x 1.7321 x 1.5” P = 5.196” 3.

On the CRT screen below, indicate where discontinuities A, B and C would appear on a properly calibrated instrument with a full screen range of 3600 A = 30.5 divisions B = 25 divisions C = 19.4 divisions

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UT LESSON 11 QUIZ F

1.

Most forgings cannot be ultrasonically inspected because of their large grain structure.

T

2.

Before performing an angle beam test on plate materials, it is advisable to first inspect the plate with straight beam transducers.

T

3.

By scanning only from the four edges, a plate can be inspected 100% utilizing an angle beam transducer.

F

4.

"Skip Distance" is the distance at an angle from the top of the plate to the bottom.

T

5.

Contact testing a weldment with a straight beam transducer usually requires that the weld surface be smooth.

F

6.

As a general rule, as the thickness of a plate gets thicker, it is best to use a larger angle transducer.

F

7.

When scanning a weldment with an angle beam technique, the transducer must be moved back at least 2 skip distances for complete coverage of the weld zone.

T

8.

As a general rule, if the pipe thickness to diameter ratio exceed 20%, an accurate test cannot be performed as the sound will not travel to the inner wall.

T

9.

When using shear waves to inspect pipe, a notch at 1800 in a sample pipe can be used for instrument calibration.

T

10. Calibration of a UT instrument with an angle beam transducer requires at least two reflections from the curved surface of the IIW block. 11. On the CRT screen below indicate where the pips would appear if the instrument were calibrated to a full screen range of 10 inches. The notch cut into the IIW block shown is curved and is 1 Inch from the exit point of the transducer. (3 PtS)

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Lesson 12 NONRELEVANT ULTRASONIC INDICATIONS Nonrelevant indications can usually be identified as one of the following: 1. Electrical interference 2. Interference from the transducer (search unit). 3. Interference from the surface of the specimen. 4. Interference caused by mode conversion of the sound beam. 5. Interference caused by the shape of the specimen. 6. Interference caused by material structure.

Non Relevant Ultrasonic Indication Non relevant indication biasa dapat didentifikasikan sebagai salah satu berikut ini: 1. Pengaruh Listrik 2. Pengaruh transducer

Electrical interference can be caused by improper electrical connections, electrical noise or faulty equipment. Search unit interference is common and is often caused by the reflection of sound energy from the interface between the wedge and test specimen surface.

Pengaruh listrik dapat disebabkan oleh hubungan listrik yang tidak benar electrical noise atau kesalahan peralatan. Pengaruh transducer sangat umum sekali dan sering disebabkan oleh pantulan energi suara dari interface diantara wedge dan permukaan benda uji.

In immersion testing, air bubbles either on the transducer or specimen can cause reduced signal amplitude from the back surface and at times also from then front surface. SURFACE INTERFERENCE A small amount of surface wave energy is usually transmitted in all directions around a transducer as shown below. If the transducer is near the edge of a plate, a signal may appear on the CRT.

Pada pengujian immersion, gelembung udara baik pada transducer maupun pada benda uji dapat menurunkan amplitudo sinyal dari permukaan belakang benda uji dan pada waktu yang bersamaan juga amlitudo sinyal dari permukaan. Pengaruh permukaan Sejumlah kecil dari energi gelombang permukaan biasanya diteruskan ke segala arah disekitar transducer seperti pada gambar di bawah ini. Jika transducer dekat ke sisi pelat, sinyal akan muncul seperti pada CRT.

When inspecting with shear waves, it is possible to detect a surface discontinuity with the small amount of surface waves generated. (see below)

Bilamana pemeriksaan dengan gelombang transversal berkemungkinan akan mendeteksi diskontinuiti permukaan dengan sedikit jumlah gelombang permukaan dibangkitkan.

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3. Pengaruh dari permukaan benda uji 4. Pengaruh yang disebabkan oleh mode conversion dari pancaran suara 5. Pengaruh yang disebabkan oleh bentuk benda uji 6. Pengaruh yang disebabkan oleh material

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If the reflection is due to surface waves, the amplitude of the pip will drop on the CRT when your finger is between the transducer and the interface producing the signal. Surface wave indications may not be cause for rejection, but they should be evaluated. Interference can be caused as a result of mode conversion in the test specimen as shown below. However, all of these reflections can be ignored as they will appear on the CRT after the first back reflection.

Kita dapat menentukan jika pantulan tersebut dari gelombang permukaan dengan meletakkan jari – jari pada sepanjang permukaan di depan transducer. Jika pantulan disebabkan oleh gelombang permukaan, amplitudo dari PIP akan turun dari CRT bilamana jari – jari diantara transducer dan interface menghasilkan sinyal indikasi gelombang permukaan tidak boleh dijadikan dasar untuk penolakan (Rejection) tetapi harus dievaluasi. Pengaruh ini juga dapat disebabkan sebagai hasil konversi mode pada benda uji seperti pada gambar di bawah ini. Bagaimanapun juga, semua pantlan ini dapat diabaikan bila muncul pada CRT setelah pantulan permukaan bagian belakang yang pertama.

The shape of the specimen can cause false indications as shown below. The ultrasonic operator should always know the configuration of the part so that these false indications can be identified.

Bentuk benda uji dapat menyebabkan terjadinya indikasi palsu seperti terlihat di bawah ini. Teknisi ultrasonic harus selalu mengenal konfigurasi benda uji sehingga indikasi palsu ini dapat didentifikasikan.

To verify a possible false indication, the operator should try to locate the discontinuity from a different location on the specimen. A non relevant indication may occur when using a transducer with a large beam spread as shown below. This indication is easily identified as it is

Untuk me – verifikasikan adanya indikasi palsu, teknisi harus coba menemukan diskontinuiti dari lokasi yang berbeda pada benda uji. Non relevant indication dapat terjadi bila menggunakan transducer dengan penyebab pancaran yang besar, seperti di bawah ini. Indikasi ini mudah dididentifikasikan bila ia selalu

You can determine if the reflection is from a surface wave by running your finger along the surface in front of the transducer.

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always behind the first back reflection of the part and would probably be continuous along the surface of the part.

hadir di belakang pantulan permukaan bagian belakang yang pertama dari benda uji dan kemungkinan akan terus ada sepanjang permukaan benda uji.

IN the situation above, a plastic shoe machined to the diameter of the part usually reduces the excessive beam spread. A large grain size may also cause “Noise” or “Hash” on the CRT screen. Abnormally large grains may result in total loss of back reflection. A lower examination frequency may help alleviate this problem.

Pada situasi diatas, sepatu plastic yang sesuai dengan diameter benda uji biasanya menurunkan penyebaran pancaran yang berlebihan. Ukuran butiran yang besar juga dapat menyebabkan “noise” atau “hash” pada laya CRT. Butiran – butiran yang besar secara tidak normal dapat menghasilkan kehilangan pantulan permukaan bagian belakang secara total. Pemeriksaan dengan frekwensi lebih rendah dapat membantu mengatasi masalah ini.

During weld inspection, non relevant indications may result from reflections from the crown and root of the weld and possibly from the heat affected zone.

Selama pemeriksaan lasan, non relevant indication dapat dihasilkan dari pantulan dari capping dan akar (root) lasan kemungkinan dari heat affected zone (haz)

Any indication on the CRT screen that is unusually consistent can be suspected as being non relevant. As is shown above, the reflection from the root and crown of the weld may appear for the entire length of the weld. If the non relevant signal is coming from the crown of the weld, it can often be identified by placing your finger wet with couplant over the suspected area.

Setiap indikasi pada layer CRT yang tidak konsisten dapat dicurigai sebagai non relevant.

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Seperti terlihat pada gambar diatas. Pantulan dari akar dan cappin dari lasan dapat muncul sepanjang lasan. Jika sinyal non relevant datang dari capping sering dapat diidentifikasikan dengan menempatkan jari – jari yang dibasahi dengan couplant pada area yang dicurigai. Prepared by Arif-010308

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If the sound beam is striking the crown, it will be dampened by your finger. A surface examination, PT or MT, can be used to reduce the possibility of a surface crack causing the reflection. Non relevant indications can often be identified by plotting the discontinuity on a ultrasonic calculator similar to the one shown below.

Jika pancaran suara menabrak capping, akan diredam oleh jari – jari, pemeriksaan permukaan oleh seperti PT atau MT dapat digunakan untuk mengurangi kemungkinan pantulan crack permukaan. Indikasi tidak relevan bisa diidentifikasi dengan mem-plot diskontinuiti pada UT kalkulator seperti berikut:

The horizontal scale measures distance from the exit point of the transducer to the discontinuity. The vertical scale represents specimen thickness and the arc represents the refracted angle of the sound beam. Example: a single vee weld with an opening of 30 degrees in A 1” steel plate using A 70 degree transducer is shown below:

Skala horizontal mengukur jarak dari exit point transduser ke diskontinuiti.

1. Draw a line representing the sound path

1. gambar garis yang menunjukkan sound path dari sudut kiri atas ke titik sudut 700 pada garis lengkung, perpanjang sampai titik 1” yang menunjukkan tebal plate. 2. buat full skip distance dengan memperpanjang 2 3/4” (lihat titik “b”) 3. gambar lasan kampuh vee tunggal dengan sudut 300 pada kertas tranparan. 4. bila jarak sound path pada CRT menunjukkan 3”, dan jarak exit point ke titik tengah lasan 2 3/4”, lalu discontinuity ditunjukkan seperti diatas

from the upper left corner to the 70 degree mark on the arc, extending to the 1” point representing plate thickness. 2. Make a full skip by doubling the 2-3/4”. (See point “B”). 3. Draw the 30 degree single vee weld on plastic or transparent paper. 4. If the sound path distance on the CRT shows 3”, and the distance from the exit point to the center of the weld is 2-3/4”, then the discontinuity is as shown above.

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Skala vertical menunjukkan ketebalan specimen dan garis lengkung menunjukkan sudut bias pancaran suara. Contoh: lasan dengan kampuh vee tunggal, sudut 300, tebal plate 1”, transduser 700 seperti berikut:

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UT LESSON 12

WORKSHEET # 1 A. Using the ultrasonic calculator that has been reproduced below, answer the followlng questions. The weld being inspected is 1" thick single vee groove weld uslng a 70 degree transducer. You will need a ruler.

4 7/16”

1.

What is the sound path to the discontinuity in the 1 inch weldment shown above?

2nd

2.

Is the discontinuity in the 1st or 2nd leg?

4”

3.

What is the surface distance from the exit point of the transducer to the center of the weld zone?

-1/8”

4.

What is the distance from the centerline of the weldment (x-axis) to the discontinuity? (Indicate + or -)

3/8”

5.

What is the distance from the top surface of the weld to the discontinuity?

700

6.

What is the degree of the sound path as shown on the above calculator?

Yes

7.

Do discontinuities "A" and "B" represent the same defect? (Yes or No)

Above

8.

On the 1" weldment above, if the sound path were 63 degrees and the sound path distance was 4-118" to the diskontinuity, where would it appear in the weld zone? DRAW IN SOUND PATH AND DEFECT ON CALCULATOR ABOVE.

+1/4”

9.

What would be the distance from the x-axis for this second discontinuity? (lndicate + or –)

1/8”

10. What Is the distance from the second discontlnulty to the surface of the weld?

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UT LESSON 12 QUIZ

F

1.

Accurate ultrasonic inspection cannot take place until all nonrelevant indications are removed from the CRT screen.

F

2.

Nonrelevant indications caused by mode conversion in a long narrow specimen will usually occur between the initial pulse and the first back reflection of the parts back surface.

T

3.

Surface waves can be generated even in a 90 degree straight beam transducer.

T

4.

Surface waves can often be identified by placing your flnger on the surface of the plate in front of the transducer.

T

5.

The beam spread resulting in a cylindrical part can be minimized by using a concave plastlc shoe between the transducer and the part.

F

6.

Large grain size in a specimen will cause "noise" or "hash" on the CRT, but the reject control on the instrument will always remove this nonrelevent indication and permit an effective test.

T

7.

The heat affected zone in a weldment may cause a nonrelevant indication of the CRT screen.

T

8.

A nonrelevant indication from the crown of a weld can often be identlfled by placing your finger on the suspected area.

F

9.

A properly used ultrasonic calculator will give you the discontinuity depth below the surface, position in the weldment and exact size.

10. On the attached ultrasonic calculator, plot the location of the discontinuity based on the following information. (2 pts for accurate drawlng) 70 Degree transducer 314 inch thick weldment Discontinuity pip on CRT at 2-314 inch Single Vee Groove Weld (30 Degree) Centerline of weld to transducer exit point is 2-314"

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2nd

a. is the discontinuity in the 1st or 2nd leg?

7/16”

b. What is the distance from top surface of the weld to the discontinuity?

- 1/8”

c. What is the distance from the center line of the weldment (x-axis) to discontinuity? (indicate + or -)

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Lesson 13 This lesson will discuss types of discontinuities that can be evaluated with the ultrasonic method. Discontinuities can be divided into three general categories inherent, processing, and service. 1. Inherent discontinuities are usually formed when the metal is molten. Inherent wrought discontinuities relate to the melting and solidification of the original ingot before it is formed into slabs, blooms and billets. Inherent cast discontinuities relate to the melting, casting and solidification of a cast article. Usually caused by inherent variables such as inadequate feeding, gating, and excessive pouring temperature or entrapped gases.

2. Processing discontinuities are usually related to the various manufacturing processes such as machining, forming, extruding, rolling, welding, heat treating and plating. 3. Service discontinuities are related to the various service conditions such as stress, corrosion, fatigue, and erosion. During the manufacturing process, may discontinuities that were subsurface will be opened to the surface by machining, grinding, etc. Remember that discontinuities are not necessarily defects. Any indication that is found by the inspector is called a discontinuity until it can be identified and evaluated as to the effect it will have on the service of the part or to the requirements of the specification. Classification Of Discontinuities By Origin Inherent discontinuities relate to the original melting and solidification of the metal in the ingot or in a casting. Typical discontinuities found in the ingot are inclusions, blowholes, pipe and segregations.

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Bab ini akan membahas tipe – tipe diskontinuiti yang dapat dievaluasi dengan metoda ultrasonic Diskontinuiti dapat dibagi kedalam tiga kategori umum sebagai berikut umum sebagai berikut: 1. Inherent discontinuities biasanya terjadi waktu logam mencair Inherent wrought discontinuities berhubungan dengan pencairan dan pembekuan ingot (balok tuangan) sebelum dibentuk menjadi slab, bloom dan billet. Inherent cast discontinuities berhubungan dengan pencairan, tuangan, pembekuan benda tuangan. Biasanya disebabkan oleh variable inherent (bawaan) seperti: inadequate feeding (pengisian tidak sempurna), Gating, Excessive pouring temperature(temperature penuangan yang berlebihan, Entraped gas (gas yang terperangkap) 2. Processing discontinuities biasanya berhubungan dengan proses pengerjaan di pabrik seperti: machining, forming, extruding, rolling, welding, heat treating 3. Service discontinuities – dihubungkan dengan berbagai kondisi operasi seperti karatan, kelelahan, dan erosi. Bagaimanapun, selama proses pabrikasi, banyak cacat sub permukaan dapat dibuat terbuka ke permukaan oleh pengerjaan dengan mesin, penggerindaan, dan semacamnya. Ingat bahwa cacat tidak selalu defect, setiap cacat yang ditemukan oleh inspektur disebut cacat sampai dapat diidentifikasi dan dievaluasi efeknya yang akan mempengaruhi bagian/alat pada saat dipakai atau permintaan yang spesifik. Diskontinuiti inherent berhubungan dengan peleburan dan pembekuan metal dalam ingot atau tuangan. Jenis cacat yang ditemukan dalam ingot adalah iinklusi, blowholes, pipa, dan segregation

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1. Non-metallic inclusions such as slag, oxides, and sulphides are present in the original ingot. 2. Blowholes & porosity are formed by gas which is insoluble in the molten metal and is trapped when the metal solidifies. 3. Pipe is a discontinuity in the center of the ingot caused by internal shrinkage during solidification. 4. Segregations occur when the distribution of the various elements is not uniform throughout the ingot. This condition is called “banding” and is not usually significant. When an ingot is further processed into slabs, blooms, and billets it is possible for the above discontinuities to change size and shape. The discontinuities after rolling and forming are called laminations, stringers, or seams depending on the type of processing and the original type of discontinuity. The “Hot top” is usually cropped off to remove most of the discontinuities before the ingot is further processed. Typical inherent discontinuities found in castings are cold shuts, hot tears, shrinkage cavities, micro shrinkage, blowholes, and porosity. A cold shut is caused when molten metal is poured over solidified metal as shown below:

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1.

Inklusi nonmetallic seperti slag, oksida, dan sulfid hadir ada di dalam ingot

2.

Blowholes (porositas) dibentuk oleh gas yang tidak dapat larut cairan metal dan terperangkap ketika metal mengeras. Pipa adalah cacat di tengah ingot disebabkan oleh penyusutan internal selama pengerasan Segregasi terjadi ketika distribusi berbagai elemen tidak seragam pada ingot. Kondisi ini disebut "banding" dan umumnya tidaklah sifnificant.

3. 4.

Bilamana ingot diproses lebih lanjut menjadi slab, bloom dan billet dan berkemungkinan diskontinuiti tersebut diatas berubah ukuran dan bentuk. Diskontinuiti yang terjadi setelah proses rolling dan forming disebut laminasi, stringers atau seams tergantung pada tipe proses dan asal diskontinuiti. Hot top (bagian atas) ingot biasanya cropped off (dibuang) untuk menghilangkan diskontinuiti sebelum ingot diproses lebih lanjut. Tipe inherent discontinuities yang ditemukan pada casting adalah cold shuts, hot tears, shrinkage cavities, microshrinkage, blowholes dan porosity. Cold shut disebabkan sewaktu logam cair dituang pada logam yang sudah membeku.

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Hot tears (shrinkage cracks) occur when there is unequal shrinkage between light and heavy sections as shown below:

Hot tears (shrinkage cracks) terjadi sewaktu penyusutan yang tidak seragam diantara bagian tipis dan yang tebal

Shrinkage cavities are usually caused by lack of enough molten metal to fill the space created by shrinkage, similar to pipe in the ingot.

Shrinkage cavities biasanya disebabkan oleh tidak cukup logam cair untuk mengisi ruangan yang diakibatkan oleh shrinkage, sama seperti pipe pada ingot.

Micro

Microshrinkage biasanya terdiri dari lubang –

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shrinkage

is

usually

many

small

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subsurface holes that appear at the gate of the casting. Micro shrinkage can also occur when the molten metal must flow from a thin section into a thicker section of a casting. Blow holes are small holes at the surface of the casting caused by gas which comes from the mold itself, many molds are made of sand. When molten metal comes into contact with the mold, the water in the sand is released as steam. Porosity is caused by entrapped gas. Porosity is usually subsurface but can occur on the surface depending on the design of the mold. Processing discontinuities are those found of produced by the forming or fabrication operations including rolling, forging, welding, machining, grinding and heat treating. As a billet is flattened and spread out non metallic inclusions may cause a lamination. Pipe and porosity could also cause laminations in the same manner as shown below:

lubang halus yang banyak pada sub permukaan yang muncul pada gate (pintu masuk) tuangan. Microshrinkage juga dapat terjadi sewaktu logam cair harus mengalir dari bagian yang tipis ke bagian yang lebih tebal pada tuangan. Blowholes adalah lubang – lubang kecil pada permukaan casting disebabkan oleh gas yang datang dari mold (matras) itu sendiri, kebanyakan mold terbuat dari pasir. Bilamana logam cair berhubungan dengan mold, air pada pasir keluar sebagai steam (uap). Porosity disebabkan oleh gas yang terperangkap. Porosity biasanya sub permukaan tetapi dapat terjadi pada permukaan tergantung kepada desain mold. Processing discontinuities ditemukan atau dihasilkan oleh forming atau oleh operasifabrikasi termasuk rolling, forging, welding, machining, gerinda dan heat treating. Bilamana billet diratakan dan penyebaran nonmetalik inclusion dapat menyebabkan laminasi. Pipe porosity juga dapat menyebabkan laminasi seperti terlihat pada gambar dibawah ini.

As a billet is rolled into bar stock, nonmetallic inclusions are squeezed out into longer and thinner discontinuities called stringers.

Bilamana billet dirol menjadi bar stok, nonmetalik inclusion dimampatkan menjadi diskontinuiti yang lebih panjang dan lebih tipis yang disebut stringers.

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Welding discontinuities the following are types of “Processing discontinuities”.

Cacat pengelasan berikut adalah termasuk tipe diskontinuiti selama proses.

Grinding cracks are a processing type discontinuity caused by stresses which are built up from excess heat created between grinding wheel and metal. Grinding cracks will usually occur at right angles to the rotation of the grinding wheel.

Grinding crack adalah tipe discontinuity yang diakibatkan oleh sebab stress yang terjadi karena perlakuan panas yang berlebihan diantara batu gerinda dan logam. Grinding crack biasanya terjadi pada sudut 900 terhadap putaran batu gerinda.

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Heat treating cracks are often caused by the stresses built up during heating and cooling. Unequal cooling between light and heavy sections may cause heat treat cracks. Heat treat cracks have no specific direction and usually start at sharp corners which act as stress concentration points. Forging discontinuities occur when metal is hammered or pressed into shape, usually while the metal is very hot. A forged part gains strength due to the gain flow taking the shape of the die. The process is shown below: A forging lap is caused by folding of metal on the surface of the forging, usually when some of the forging metal is squeezed out between the two dies.

Heat treating crack sering terjadi karena stress yang terjadi sewaktu pemanasan dan pendinginan. Pendinginan yang tidak seragam diantara bagian yang tipis dan bagian yang tebal dapat menyebabkan heat treat crack. Heat treat crack tidak mempunyai arah yang specific dan biasanya mulai pada bagian sudut yang tajam yang bertindak sebagai titik konsentrasi tegangan (stress concentration point). Forging diskontinuiti terjadi sewaktu logam dipukul atau ditekan menjadi bentuk yang biasanya dilakukan sewaktu logam tersebut masih sangat panas. Bagian yang ditempa mendapatkan kekuatan karena butiran mengalir membentuk die (matras). Prosesnya seperti terlihat pada gambar dibawah ini. Forging lap disebabkan oleh terlipatnya logam pada permukaan forging, biasanya sewaktu logam tempa dimampatkan diantara dua die (matras).

A forging burst is a rupture caused by forging at improper temperatures. Bursts may be either internal or open to the surface as shown below.

Forging burst adalah patahan yang disebabkan oleh forging pada temperature yang tidak tepat. Burst dapat berupa internal atau terbuka di permukaan.

Service discontinuities are also important types to consider. Articles which may develop defects due to

Service discontinuities juga termasuk tipe yang penting untuk dipertimbangkan. Benda yang dapat memunculkan defect karena

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metal fatigue are considered extremely critical and demand close attention. Fatigue cracks are service type discontinuities that are usually open to the surface. They often start from stress concentration points. Fatigue cracks are possible only after the part is placed into service, but may be the result of porosity, inclusions or other discontinuities in a highly stressed metal part.

kelelahan logam dianggap sangat kritis dan perlu perhatian dengan seksama. Fatique crack adalah tipe diskontinuiti karena penggunaan yang biasanya membuka ke permukaan. Biasanya mulai dari titik konsentrasi tegangan. Fatique crack terjadi setelah bagian tersebut digunakan, tetapi dapat juga sebagai hasil porosity, inclusion atau diskontinuiti lainnya pada bagian logam yang mengalami stress sangat tinggi.

UT LESSON 13 QUIZ

T 1.

Inherent discontinuities are usually considered to be those formed when the metal is in a molten condition.

F 2.

Discontinuities involving fatigue are often considered critical and are referred to as a processing type discontinuity.

F 3.

Discontinuities and defects are terms that are considered to have the same meaning in ultrasonic testlng methods.

T 4.

Knowing the history and intended use of a part is usually considered important in selecting the test method and knowing the type of discontinuity to look for.

F 5.

Ultrasonic testing would always be a good choice in choosing a NDT method to locate microshrinkage In a casting.

T 6.

Porosity in a billet could cause a lamination i f the metal were formed into a flat plate.

T 7.

When a billet is rolled into bar stock, a nonmetallic inclusion could be formed into a longer and thinner discontinuity called a stringer.

T 8.

Stringers and laminations could be found In a finished product if non-metallic inclusions were present in the original ingot.

F 9.

Hot tears and shrinkage cracks are often the result of metal cooling too rapidly in the ingot stage.

T 10. Porosity is caused by gas which is trapped in the molten metal as it solidifies. T 11. Laps and bursts are examples of processlng type discontinuities. T 12. The ultrasonic testing method can be used for flnding slag inclusions in weldments. T 13. Grinding cracks are often caused by the stresses created by the excessive heating of the metal surface. F 14. Because cold metal occupies more space than hot metal, there is the danger of "hot tears" during the casting process. F 15. Lack of penetration and lack of fusion both refer to the same type of welding discontinuity. T 16. Lack of fusion between passes in a weldment can be detected with the ultrasonic testing method. Rev. 00

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Lesson 14 Identification and comparison of discontinuities that can be found with the ultrasonic testing method. The student is asked to study the photographs and descriptions of typical discontinuities as printed in the UT classroom training handbook (CT-6-4). Each of the specific discontinuities illustrated are divided into the three general categories: inherent, processing and service.

Identifikasi dan perbandingan cacat yang dapat ditemukan dengan metode ultrasonic testing. Siswa diminta untuk mempeljari foto dan uraian jenis cacat seperti dicetak dalam UT classroom training hand book ( CT-6-4) Setiap cacat spesifik yang digambarkan dibagi menjadi tiga kategori umum: inherent, process, dan service.

Burst Fillet crack Heat effected zone crack Tubing cracks Hydrogen flake Inclusions Lack of penetration Laminations Gas porosity it is also suggested that the student study the other examples give and make a comparison of the types of discontinuities that are difficult to detect with ultrasonic techniques.

Page 7-8 Page 7-12 Page 7-18 Page 7-26 Page 7-28 Page 7-34 Page 7-36 Page 7- 38 Page 7-46

Juga dianjurkan agar siswa belajar contoh lain dan membandingkan diskontinuiti yang sulit dideteksi oleh UT

LESSON 14 QUIZ

-

MATCHING Match the categories of discontinuities with the types of discontinulties listed. it is possible that a discontinuity can fail into more than one category; list all possibilities. A

1. laps

C

2. grinding cracks

B

3. cold shut

E

4. fatique

BD

5. porosity

AB

6. lamination

B

7. lamination

d. processing – welding

D

8. undercut

e. service

B

9. hot tears

ABD

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a. inherent – wrought b. inherent

– cast

c. processing – machining

10. inclusions

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Attachment

Metals

Longitudinal Velocity

Shear Velocity

Surface Velocity

cm/μs

in/μs

Aluminum

.632

.2488

.313

.1232

N/A

N/A

2.70

17.10

AL 1100-0 (2SO)

.635

.25

.310

.122

.290

.114

2.71

17.20

AL 2014 (14S)

.632

.2488

.307

.1209

N/A

N/A

2.80

17.80

AL 2024 T4 (24ST)

.637

.2508

.316

.1244

.295

.116

2.77

17.60

AL 2117 T4 (17ST)

.650

.2559

.312

.1228

N/A

N/A

2.80

18.20

Bearing Babbit

.230

.0906

N/A

N/A

N/A

N/A

1.10

23.20

Beryllium

1.29

.5079

.888

.3496

.787

.310

1.82

23.50

Bismuth

.218

.0858

.110

.0433

N/A

N/A

9.80

21.40

Brass

.428

.1685

.230

.0906

N/A

N/A

8.56

36.70

Brass, Half Hard

.383

.1508

.205

.0807

N/A

N/A

8.10

31.02

Brass, Naval

.443

.1744

.212

.0835

.195

.0770

8.42

37.3

Bronze, Phospho

.353

.139

.223

.0878

.201

.0790

8.86

31.28

Cadmium

.278

.1094

.150

.0591

N/A

N/A

8.64

24.02

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cm/μs in/μs cm/μs

Acoustic Density Impedance g/cm23 g/cm secx105

in/μs

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Cesium (28.5⎬ C)

.0967

.0381

N/A

N/A

N/A

N/A

1.88

1.82

Columbium

.492

.1937

.210

.0827

N/A

N/A

8.57

42.16

Constantan

.524

.2063

.104

.0409

N/A

N/A

8.88

46.53

Copper

.466

.1835

.0890

.035

.193

.0760

8.93

41.61

Gallium

.274

.1079

N/A

N/A

N/A

N/A

5.95

16.3

Germanium

.541

.213

N/A

N/A

N/A

N/A

5.47

29.59

Gold

.324

.1276

.120

.0472

N/A

N/A

19.32

62.6

Hafnium

.384

.1512

N/A

N/A

N/A

N/A

N/A

N/A

Inconel

.572

.2252

N/A

N/A

.279

.110

8.25

47.19

Indium (156⎬ C)

.222

.0874

N/A

N/A

N/A

N/A

7.30

16.21

Iron

.590

.2323

.323

.1272

.279

.110

7.70

45.43

Iron, Cast

.480

.189

.240

.0945

N/A

N/A

7.80

37.44

Lead

.216

.085

.070

.0276 .0630

.0248

11.4

24.62

Lead, 5% Antinomy

.217

.0854

.081

.0319 .0740

.0291

1.9

23.65

Magnesium

.631

.2484

N/A

N/A

1.74

10.98

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N/A

N/A

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Magnesium (AM-35)

.579

.228

.310

.122

.287

.113

1.74

10.07

Magnesium (FS-1)

.547

.2154

.303

.1193

N/A

N/A

1.69

9.24

Magnesium (J-1)

.567

.2232

.301

.1185

N/A

N/A

1.70

9.64

Magnesium (M)

.576

.2268

.309

.1217

N/A

N/A

1.75

10.08

Magnesium (O-1)

.580

.2283

.304

.1197

N/A

N/A

1.82

10.56

Magnesium (ZK-60A-TS)

.571

.2248

.305

.1201

N/A

N/A

1.83

10.45

Manganese

.466

.1835

.235

.0925

N/A

N/A

7.39

34.44

Molybdenum

.629

.2476

.335

.1319

.311

.122

10.2

64.16

Monel

.602

.237

.272

.1071

.196

.0772

8.83

53.16

Nickel

.563

.2217

.296

.1165

.264

.104

8.88

49.99

Platinum

.396

.1559

.167

N/A

N/A

N/A

21.4

84.74

Plutonium

.179

.0705

N/A

N/A

N/A

N/A

N/A

28.2

Plutonium (1% Gallium)

.182

.0717

N/A

N/A

N/A

N/A

N/A

28.6

Potassium (100⎬ C)

.182

.0717

N/A

N/A

N/A

N/A

.83

1.51

Radium

.0822

.0324

.111

.0437

.103

.0404

5.0

4.11

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Rubidium

.126

.0496

N/A

N/A

N/A

N/A

1.53

1.93

Silver

.360

.1417

.159

.0626

N/A

N/A

1.5

37.8

Silver, Nickel

.462

.1819

.232

.0913

.169

.0665

8.75

40.43

Silver, German

.476

.1874

N/A

N/A

N/A

N/A

8.70

41.41

Steel, 302 Cres

.566

.2228

.312

.1228

.312

.123

8.03

45.45

Steel, 347 Cres

.574

.226

.309

.1217

N/A

N/A

7.91

45.4

Steel, 410 Cres

.739

.2909

.299

.1177

.216

.0850

7.67

56.68

Steel, 1020

.589

.2319

.324

.1276

N/A

N/A

7.71

45.41

Steel, 1095

.590

.2323

.319

.1256

N/A

N/A

7.80

46.02

Steel, 4150, Rc14

.586

.2307

.279

.1098

N/A

N/A

7.84

45.94

Steel, 4150, Rc18

.589

.2319

.318

.1252

N/A

N/A

7.82

46.06

Steel, 4150, Rc43

.587

.2311

.320

.126

N/A

N/A

7.81

45.84

Steel, 4150, Rc64

.582

.2291

.277

.1091

N/A

N/A

7.80

45.4

Steel, 4340

.585

.2303

.128

.0504

N/A

N/A

7.80

45.63

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Tantalum

.410

.1614

.114

.0449

N/A

N/A

16.6

68.06

Thallium (302⎬ C)

.162

.0638

N/A

N/A

N/A

N/A

11.9

19.28

Thorium

.240

.0945

.156

.0614

N/A

N/A

11.3

27.12

Tin

.332

.1307

.167

.0657

N/A

N/A

7.29

24.2

Titanium

.607

.239

.331

.1303

N/A

N/A

4.50

27.32

Titanium Carbide

.827

.3256

.516

.2031

N/A

N/A

5.15

42.59

Tungsten

.518

.2039

.287

.113

.265

.104

19.25

99.72

Uranium

.338

.1331

.196

.0772

N/A

N/A

18.9

63.88

Uranium Dioxide

.518

.2039

N/A

N/A

N/A

N/A

6.03

31.24

Vanadium

.600

.2362

.278

.1094

N/A

N/A

6.03

36.18

Zinc

.417

.1642

.0949 .0374

N/A

N/A

7.10

29.61

Zircaloy

.472

.1858

.093

.0366

N/A

N/A

9.03

42.6

Zirconium

.465

.1831

.0886 .0349

N/A

N/A

6.48

30.1

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LONGITUDINAL CRACK

TRANSVERSE CRACKS

THROAT CRACK INCOMPLETE FUSION of FLARE-BEVEL GROOVE WELDS

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INCOMPLETE FUSION BETWEEN WELD AND BASE METAL

SURFACE SLAG INCLUSION UNIFORMLY SCATTERED SURFACE POROSITY

LINEAR SURFACE POROSITY WITH CONNECTING CRACK

ISOLATED SURFACE POROSITY

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ELONGATED SURFACE POROSITY

FILLET WELD PIPING POROSITY

UNDERCUT ADJACENT TO FILLET WELD

UNDERFILL

FILLET WELD CONVEXITY

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CRACK FORMED AT WELD SPATTER ON BASE METAL SURFACE

WELD SPATTER ON BASE METAL WELD CONFIGURATION WHICH MAY CAUSE LAMELLAR TEARING

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WELD METAL CRACKING DUE TO PRESENCE OF LAMINATION

OVERLAP IN FILLET AND GROOVE WELDS

UNDERFILL IN GROOVE WELDS

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UNDERBEAD CRACK TOE CRACKS

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THROAT CRACKS IN FILLET WELDS

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