Memory Alloys

Topics: Shape memory alloy, Shape memory polymer, Martensite Pages: 13 (3829 words) Published: February 23, 2011
Shape Memory Alloys and Its Applications

Ng Jia Minh (U076833J) -


Shape memory alloys make use of the transformation that takes place in the martensitic structure of Ni-Ti and copper based alloys with the change of temperature. It has the ability to “remember” its original structure which makes it so much different than any other alloys. Another important application of this shape memory alloy is that it can also generate a great amount of force and do work if constrained. The use of shape memory alloys in industrial applications has been increasing over the years. However, in this current term paper for the module ME4254, our group has been given a chance to study in much greater detail about the alloy and suggest a creative idea on how we can benefit ourselves in our daily life with this alloy. An innovation that was come up by our group is integrating the alloy into window shades to reduce the heat signature of buildings without any consumption of electrical energy.

Table of Contents
1. Introduction
2. Scope of project
3. Shape Memory Materials
4. Nitinol: Properties and Structures
5.1. Properties
5.2. Stress-Strain Characteristics at Various Temperatures 5.3. Structure
5. Applications
6.4. Orthodontic Archwires
6.5. High Pressure Seal
6.6. Micro-Electro-Mechanical-Systems (MEMS)
6. Innovation
7. Conclusion

1. Introduction

Over many centuries, men have aspired with their knowledge to design and build structures and mechanisms that come as welcome solutions to technological barriers.

It can be currently observed that most inventions and design concepts of many inventors and researchers worldwide show a thrust towards a goal that is to be much desired – a day where their inventions can become highly manoeuvrable, to such an extent that their inventions are able to overcome gradual or sudden unforeseen changes in their operating environment with little or no human involvement.

This development is already being pursued in the control aspect of engineering, which encompasses artificial intelligence, sensors and high degrees of programming for high end machines. One example can be found in Stanford University, where they have been successful in developing an autonomous robotic vehicle that can drive through desert terrain without human intervention (Standford University, 2005).

That said, we observe that the development of new materials in this mentioned thrust towards self control is still in the stage of infancy, as compared to the control aspect. However, in the current century, where technological barriers are being broken at a break-neck speed, the field of such materials, or more commonly known as ‘Smart Materials’ is emerging rapidly and have begun to have found usage in various applications, which we will introduce and discuss in the later pages. The more common smart materials currently found in the industry are piezoelectric ceramics and shape memory alloys.

2. Scope of Project

Shape memory alloys are a relatively new concept compared to that of piezoelectric materials, which have been discussed as early as the 1880s by Pierre and Marie Currie. However, as a ceramic material it possesses high compressive strength and stiffness and hence it is a less effective material when subjected to tensile loading. Ceramics are also sensitive to cracks and defects.

This is not the case for shape memory alloys, which can sustain a larger tensile load. We believe that the use of such alloys will become increasingly popular when the technical difficulties are overcome and the cost of such alloys decrease with mass usage.

Therefore, the purpose of this project is to introduce shape memory materials with a review of its current developments and delve into the mechanical properties that give its abilities. We also hope to present to the reader the memory alloy Nitinol and...
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