5Prinsip 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.
6Shape Memory Alloys? Austenite Martensite 4/9/2017Shape Memory Alloys?Shape Memory Alloys (SMAs) merupakan paduan logam yang mengalami transisi fase padat –padat dan dapat menunjukkan kembali regangannya.contoh: NitinolAusteniteHigh temperature phaseCubic Crystal StructureMartensiteLow temperature phaseMonoclinic Crystal StructureThis is a representation of the transformation process. The amount of heat needed depends on the material’s transformation temperature. This can be room temperature or freezing.Twinned MartensiteDetwinned Martensite
7Induksi termal pada fase transisi SMA MfMsAsAfAusteniteMartensiteTEMPERATURE(twinned)Characteristic temperatures: Mf=Martensitic Finish Ms=Martensitic Start As=Austenitic Start Af=Austenitic Finish
15Aplikasi... 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.
16Aplikasi ...Tegangan listrik menyebabkan muatan elektrolit berubah. Muatan listrik akan menginduksi permukaan nanopartikel.Perubahan muatan ini membuat perubahan konduksi elektron atom .
18Discussion 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.
19SHAPE 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 1965Where 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.
20HOW DOES NITINOL WORK? Nitinol is made of Nickel and Titanium Most solids have one crystal structure, but Nitinol has twoThe crystal structure is different at cold and hot temperaturesAt cold temps it is soft and easy to bend but at hot temps it is stiff and springy.Nitinol is made up of two kinds of atoms: Nickel atoms and Titanium atoms.They are arranged in an organized pattern called a crystal structure.Most solids have a crystal structure, but Nitinol is special because it has two different crystal structures, also called solid phases.At colder temperatures, Nitinol’s atoms are in one arrangement, called martensite.At higher temperatures, Nitinol’s atoms are in a slightly different crystal structure, called austenite.When you heat Nitinol, you give the atoms energy to move from the martensite structure to the austenite structure, and as it cools back down, they move back.The atoms in the Nitinol move just a little bit, but this makes a huge difference in how the metal feels and behaves.At lower temperatures, Nitinol is soft and easy to bend.At hotter temperatures, it is stiff and springy.
21WHY IS NITINOL SO VERSATILE? It has similar properties to human hair and human tendons and is being used in a wide range of applications.Nitinol is sometimes referred to as the Shape shifter of the 21st century. The reason –it mimics human tendons and human hair which has made them useful in a lot of inventions, like wires for braces, staples that hold broken bones together, coffee pots that turn off when the water is hot enough, and trick spoons that bend when you try to stir your tea!, Medical components, Space components, Textiles, robotics, Water sprinklers, Pipe connectionsThis SMART property has made them useful in many inventionslike wires for braces, staples that hold broken bones together,coffee pots that turn off when the water is hot enoughtrick spoons that bend when you try to stir your tea
22Did You Know? THAT YOU CAN NOW HAVE… Nitinol’s amazing properties allows surgeons to perform life saving operationsNinol is used to:Seal holes in the heartPatch up faulty blood vesselsAttach tendons to bones.AMPLATZER® Septal Occluder for heart defect repair utilizes the shape memory of Nitinol
23Research scientists, innovators and artists are always finding new creative uses for Nitinol. Knee replacementsSpectacle framesMedical stentsRepair broken bonesReplace damaged discs.What else?
24Applications Of Nitinol THE ICEMOBILEA 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).Here are some applications where Nitinol has been used.PURPOSE: To illustrate shape-memory alloy.DESCRIPTION: A thin NITINOL wire loop is connected around two pulleys. The lower pulley is placed half way into the water at degrees celcius and an ice cube gently touched to the wire. If the wire is gently spun downward through the ice cube into the water bath, it will continue to spin, cutting the ice cube in two.Alternatively, a glob of crushed ice placed around the wire as it enters the box will cause the wire to circulate as described above, as shown in the photograph.SUGGESTIONS: Do not bend or stress wire or the memory may be changed. If ice forms on the wire, melt it by immersing the wire in the water.REFERENCES: (PIRA 4F30.60)EQUIPMENT: Icemobile ice cutter assembly, beaker of warm water, ice cubes, dial thermometer.SETUP TIME: 5 min.