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shape memory alloys
- 1. SHAPE MEMORY ALLOYS DONEBY RAMVIKAS GS
- 2. INTRODUCTION TO SMA Shape memory alloy is an alloy SMA is one of the type of smart materials Shape memory alloys are materials that “remember” their original shape . It gets deformed then recover their original shape Upon heating. ~They can take large stress without undergoing permanent deformation
- 3. HOW DO THEYWORK We all know the most common phase changes SMA’s shape changes based on a solid state phase transformation. The transition from one form of crystalline structure structure to another creates the mechanism by which the shape changes occur in SMA’s .This change involves transition from a monoclinic crystal from martensitic to an ordered cubic crystal from austenite.
- 4. HISTORY OF SHAPEMEMORY ALLOYS 1938:Arne olande observed shape and recovery ability of AU-Cd alloy 1938:greninger and Mooradium observed the formation and disappearance of martensitic phase by varying the temperature of a CU- ZN alloy 1962-63 william.j.Buchler and frederic Wang observed the shape memory effect in Nickel and Titanium alloy at the united states naval ordnance laboratory. Nitinol –Nickel Titanium naval ordnance laboratories. Where the two elements are present in roughly equal atomic percentages Eg-nitinol 55,Nitinol
- 5. TYPES OF SHAPEMEMORY ALLOYS CHARACTERISTICS OF SMA These two main families of alloys Based on copper(cu): cu-al-ni and cu-zn- al are used for narrow hysteresis and adapatability. Based on NICKEL(NI);NI-TI ternary(x) Now way days NI-TI-X are used than 90% of new SMA applications. Ni-ti alloys are more expensive to melt and produced than copper alloy but they are preferred for their corrosion resistance,bioompatibility,and higher electrical resisting heating in actuator application IT exhibits two main characteristics 1.SHAPE MEMORY EFFECT 2.SUPER ELASTICITY; SHAPE MEMORY EFFECT –It is based on martensite phase transformation taking place without diffusion . Martensite phase transformation that occurs as a result of stress and temperature change
- 6. SHAPE MEMORY EFFECTBEHAVIOUR ONE-WAY SHAPE MEMORY EFFECT TWO-WAY SHAPE MEMORY EFFECT Transformation to the desired shape occurs only upon heating i.e.., memory is with austenite phase The deformed shape is remembered during cooling , in addition to the original shape being remembered during heating i.e.., memory is both with austenite and martensitic phases
- 7. SUPER ELASTICITY SHAPEMEMORY (PSUEDOELSTICITY) It is an elastic (reversible) response to an applied stress. Occurs without temperature change. This property allows the SMA’S to bear large amounts of stress without undergoing permanent Deformation. Temperature of sma is maintained above transition temperature
- 8. PROPERTIES OF SHAPEMEMORY ALLOY The copper-based and ni-ti alloy are considered to be engineering materials. These composition can be manufactured to almost any shape and size The yield strength of shape-memory alloys is lower than of conventional steel ,but some composition have a higher yield strength than plastic and aluminum The yield stress for NI-TI can reach 500 mpa The maximum recoverable strain these materials can hold without permanent damage is up to 8% for some alloys This compares with a maximum strain 0.5% for conventional steels
- 9. ADVANTAGES OF SHAPEMEMORY ALLOY Very high power/weight ratio comparatively Accessible voltages can accomplish THERMO ELASTIC TRANSFORMATION Higher strain recovery Higher strength Compactness ,allowing for reduction in overall actuator size Noiseless and silent operation High corrosive resistance
- 10. APPLICATIONS OF SHAPEMEMORY ALLOY AIRCRAFT CIVIL STRUCTURES to reduce engine noise, some designers installs ,chevrons onto engines to mix flow of exhaust gases and reduce engine noise ROBOTICS Recently a prosthetic hand was introduced by loh and his teammates that can almost replicate the motions of a human hand Sma’s have a variety of applications in civil structure such as bridges and buildings one such application is INTELLIGENT REINFORVCED CONCRETE(IRC),which incorporates SMA wires embedded within the concrete. Another application is active turning of structural natural frequency using SMA’s wires to dampen vibrations
- 11. LIMITATIONS OF SHAPEMEMORY ALLOY Heat dissipation , need mechanism for cooling Less stiffness/high flexibility Relatively expensive to manufacture and machine compared to other materials such as steel and aluminum Most SMA’s have poor fatigue properties( a steel component may survive for more than one hundred time more cycles than a SMA element)
- 12. PIPING The firstconsumer commercial application was a shape-memory coupling for piping eg ; oil line for industrial purpose , water pipes Use of memory alloys for coupling tubing; a memory alloys for coupling is expanded so it fits over the tubing MEDICINE STENT- a reinforced grafts for vascular application to replace or repair damaged arteries
- 13. FUTURE SCOPE APPLICATIONOF SMA There are many possible application for sma Future application are envisioned to include engines in car and airplanes and electrical generators utilizing the mechanical energy resulting from shape transformers Nitinol with its shape memory property is also envisioned for use as car frames Other possible automotive applications using SMA include engine cooling , carburetor and engine lubrication controls ,and control of a radiator blind ” to reduce the flow of air through the radiator at start up when the engine is cold and hence to reduce fuel usage and exhaust emissions
- 14. CONCLUSION The manyuses and applications of shape memory alloy ensure a bright future for these metals Research is currently carried out at many places of robotics departments and material science department With the innovative ideas for application of sma’s and the number of products on the market using SMA’s continually growing , advances in the field of shape memory alloys for use in many different fields of study seen very promising