Deformation of shape memory alloys for shock energy absorption applications

• Main Author: Ang, Eng Ann
• Other Authors: Liu Yong
• Format: Final Year Project
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering::Materials::Material testing and characterization
• Online Access: http://hdl.handle.net/10356/53570
• Institution: Nanyang Technological University

In recent years, greater emphasis has been placed on the ability of structures and other applications to absorb large impact loads. Thin-wall tubes are the preferred form of materials for energy absorption testing purposes. While tubes made of conventional materials such as Steel and Aluminium alloy have proved to be relatively good energy absorbers due to their ductility, they only absorb energy through plastic deformation and hence cannot be used repeatedly. Shape Memory Alloys (SMA) is well known for its ability to recover completely from large deformations through phase transformation by heating or removal of stress. Hence, this study serves to explore the feasibility of SMA as an energy absorbing material. As the superelastic characteristic of SMA does not require heat for recovery, the energy absorption of SMA, specifically Nickel-Titanium alloy (Nitinol) of this characteristic was studied. The transformation temperatures of the Nitinol tube was first characterised using DSC equipment and the results obtained confirmed the tube to be superelastic as it is found to be fully Austenitic at room temperature. The tube was then subjected to Quasi-Static axial compression, lateral compression and axial tensile tests to characterise its behavior in tension and compression and to obtain the load-displacement curve from the compression test data. The compression test result showed that superelastic Nitinol can fully recover from up to 8% strain. The load-displacement curve was also analysed to calculate the amount of energy absorbed.