SHAPE MEMORY ALLOYS.pptx

Brief presentation on Shape memory alloy

1. SHAPE MEMORY ALLOYS Aditya Abhinav 119MM0934 Metallurgical And materials engineering

2. Outline Introduction of shape memory alloys History of shape memory alloys Working Principle Types of shape memory alloys Characteristics of SMA Applications of SMA Advantages/ Limitations of SMA Conclusion References

3. Introduction of SMA SMA is a type of smart Materials. SMA are materials that “remember” their original shape. If deformed they recover their original shape upon heating. They can take large stresses without undergoing permanent deformation. They can be formed into various shape like bars ,wires, plates and rings thus serving various functions.

4. History of SMA 1938:Arne Olande observed shape and recovery ability of Au-Cd alloy. 1938:Greninger and Mooradian observed the formation and Mooradian observed the formation and disappearance of martensitic phase by varying the temperature of a Cu-Zn alloy. 1962-63:William J Buehler and Fredric Wang observed the shape effect of Nickle and Titanium alloy at the United States Navel Ordnance Laboratory.

5. How do they work We all know the most common phase changes: SMAs shape changes based on a solid sate phase transformation. The transition from one form of crystalline structure to another creates the mechanism by which the shape change occurs in SMAs. This change involves transition from a monoclinic crystal form (martensite) to an ordered cubic crystal form(austenite). Austenite High temperature phase Cubic Crystal Structure Martensite Low temperature phase Monoclinic Crystal Structure

6. How do they work

7. Types of SMA Current shape memory alloys are: NiTi, or nitinol.  This is the most developed SMA, with excellent mechanical properties. It is pretty much the only commercially viable SMA. Cu-Al-Ni,   Fe-Mn-Si, and Cu-Zn-Al systems.  These have poorer mechanical properties and are still in development, although they may one day offer advantages over NiTi such as higher transformation temperatures Ni-Mn-Ga.  A magnetic shape memory alloy, which is affected by magnetic fields rather than temperature. Magnetic shape memory alloys are also in the developmental stage.

8. Characteristics of SMA It exhibits two main characteristics : 1) Shape Memory Effect :It is based on martensitic phase transformation taking place without diffusion. Two types of shape memory behavior: -One way shape memory -Two way shape memory 2) Pseudo-elasticity : Pseudo–elasticity occurs in shape memory alloys when it is completely in austenite phase it occurs due to stress induced phase transformation without a change in temperature.

9. Applications of SMA Used for Pseudoelasticity Glasses frames Orthodontics Metal plates to help bone grow together Vibration dampening for jets or other engines Structure stabilization (like for earthquakes) Used for SME Temperature-sensitive safety devices Stents Actuators(especially prosthetic hands or airplane flaps) Motors (not really, but it is theoretically possible)

10. Advantages and Limitation Advantages : High power/weight ratio comparatively High strain recovery High strength Noiseless and silent Operation Limitations : Poor fatigue properties Lower transformation temperature Relatively expensive to manufacture and machine compared to other materials.

11. Conclusion Shape memory alloys are awesome! They have a temperature induced transformation martensite–>austenite, which gives the shape memory effect (SME) as well as a stress-induced transformation austenite–>martensite, which give the pseudoelastic effect. The many uses and application of shape memory alloys ensure a bright future for these metals. Advances in the field of SMAs for use in many different fields of study seem very promising. References What Are Shape Memory Alloys? (Metallurgy, How They Work, and Applications) – Materials Science & Engineering (msestudent.com) Shape-memory alloy – Wikipedia Ti -Ni Shape-Memory Alloy - Stanford Materials

12. Thanks