Memory Shape Alloy

MEMORY SHAPE ALLOY

Definisi Shape Memory Alloy (SMA)

Shape Memory Alloys (SMAs) merupakan kelompok paduan logam yang dapat menemukan kembali dengan baik regangan permanennya bila dipanaskan pada suhu tertentu.

Sejarah SMA • • • • • •

Ditemukan tahun 1932, Oleh Chang dan Read. Tahun 1938, kuningan (CuZn). Tahun 1951, Emas kadmium (AuCd). Tidak ada aktivitas sampai 1962. Buehler and co-workers menemukan NickelTitanium (NiTi).

Apa material shape memory ?

Prinsip dasar • SMA mempunyai dua fase stabil – fase suhu tinggi ( austenite) dan fase suhu rendah (martensite). • Martensite dapat muncul dalam dua bentuk yaitu twinned dan detwinned. • Fase transisi yang muncul antara dua fase di atas ( melalui pemanasan/pendinginan) merupakan dasar untuk menjelaskan sifat unik SMA.

Shape Memory Alloys? •Shape Memory Alloys (SMAs) merupakan paduan logam yang mengalami transisi fase padat –padat dan dapat menunjukkan kembali regangannya. •contoh: Nitinol

Austenite • High temperature phase •Cubic Crystal Structure

Martensite •Low temperature phase •Monoclinic Crystal Structure

Twinned Martensite

Detwinned Martensite

Induksi termal pada fase transisi SMA

Martensite (twinned)

Martensite (twinned)

TEMPERATURE

Mf

Ms

As

Af

As

Af

TEMPERATURE

Mf

Ms

Austenite

Austenite

Characteristic temperatures: Mf=Martensitic Finish Ms=Martensitic Start As=Austenitic Start Af=Austenitic Finish

Efek Shape Memory : Stress Free Shape Recovery

STRESS

Detwinned Martensite (stressed - deformed)

STRESS

Detwinned Martensite (stressed - deformed)

Mf

Ms

As

Twinned Martensite (unstressed) TEMPERATURE

Af

Mf Detwinned Martensite (unstressed - deformed)

Ms

As

TEMPERATURE

Af Austenite (undeformed)

Efek shape memory (SME)?

Efek Shape Memory s Detwinning

e Cooling

Heating/Recovery

T

STRESS

Shape Memory Effect: Shape Recovery Under Stress

Detwinned Martensite (stressed)

Mf

Ms

Austenite

As

Af

TEMPERATURE

The Pseudoelastic Effect

STRESS

Detwinned Martensite (stressed)

Mf

Ms

As

TEMPERATURE

Af Austenite

Aplikasi • Nanomuscles • Alat-alat bedah – – – –

Tissue Spreader Stents (angioplasty) Coronary Probe Brain Spatula

• Endoscopy: miniature zoom device, bending actuator • Force sensor • Smart skin (wing turbulence reduction)

SMAs in Bio-medical Devices (a)

(b)

Aplikasi... Otot logam yang lentur dengan suhu rendah Penguapan dan kondensasi platina murni pada gas atmosfir tipis akan terkonversi menjadi partikel lebih kecil 5 nanometer. • Partikel-partikel ini dimampatkan dalam tubuh nanoporous. Padatan yang diperoleh selanjutnya dicelupkan ke cairan konduktif (electrolyte) dan mengisi rongga. Melalui elektrolit ini , asam atau basa yang bermuatan listrik dapat dibawa oleh nanopartikel ke padatan.

Aplikasi ... • Tegangan listrik menyebabkan muatan elektrolit berubah. Muatan listrik akan menginduksi permukaan nanopartikel. • Perubahan muatan ini membuat perubahan konduksi elektron atom .

http://www.fzk.de/stellent/groups/public/documents

Discussion of Application • An advantage to this new shape memory alloy is its’ efficiency. No other alloy or polymer can compare to its’ strength and efficiency to weight ratio. • Nanomuscles weigh just one gram but can lift 140 grams, and are preferred to electric motors as they are far cheaper to produce.

SHAPE MEMORY ALLOY–NITINOL •

•

•

What is it? One type of shape memory alloy is Nitinol, which is short for Nickel Titanium Naval Ordnance Laboratory and which acknowledges the site of its discovery in 1965 Where does it get its name? Nitinol is an alloy of about 56 % Nickel and 44 % Titanium. (Hence the name: Ni–Ti–Naval Ordinance Laboratory) What does it do? Nitinol “remembers” its original shape and springs back up to temperatures up to 500 degrees C. Can be strained 8 to 10 times more than spring steel without permanent deformation. Won’t kink. Coils easily.

HOW DOES NITINOL WORK? • • • •

Nitinol is made of Nickel and Titanium Most solids have one crystal structure, but Nitinol has two The crystal structure is different at cold and hot temperatures At cold temps it is soft and easy to bend but at hot temps it is stiff and springy.

WHY IS NITINOL SO VERSATILE? It has similar properties to human hair and human tendons and is being used in a wide range of applications.

Did You Know? THAT YOU CAN NOW HAVE… Nitinol’s amazing properties allows surgeons to perform life saving operations Ninol is used to: •Seal holes in the heart •Patch up faulty blood vessels •Attach tendons to bones. AMPLATZER® Septal Occluder for heart defect repair utilizes the shape memory of Nitinol

Research scientists, innovators and artists are always finding new creative uses for Nitinol. • Knee replacements • Spectacle frames • Medical stents • Repair broken bones • Replace damaged discs. • What else?

Applications Of Nitinol THE ICEMOBILE A Nitinol heat engine, called the Icemobile has a loop of Nitinol which you immerse in warm water, to make it spin (which then cuts up ice cubes).