Determination of Stress-Strain Relationships of a NiTi Shape Memory Alloy in Tension and Compression by Four-Point Bending Test

摘要

Nickel-titanium (NiTi) shape memory alloy is widely used in a variety of applications due to its novel shape memory effect. The mechanical behaviour of NiTi is complicated and depends on its phase and testing temperature. In addition, its response in uniaxial tension may be far away from that in uniaxial compression even at the same testing temperature. Therefore, it is necessary to obtain both the tensile and compressive stress-strain relationships of a NiTi shape memory alloy at different temperatures. Practically, this is a very tedious work. Instead of conducting two different tests (normally using two different sized samples) for its behaviours in tension and compression, one single four-point bending test with the strains measured at the top and bottom surfaces of the sample is a better alternative. This paper follows this approach to determine the stress-strain relationships of a NiTi shape memory alloy in uniaxial tension and uniaxial compression at some different temperatures.