Comparison of the Effects of Strain Rate in Three Different Environments on the Results of Tension Testing of Superelastic Nickel-Titanium (Nitinol)

Mechanical testing provides important materials properties data during the physical evaluation of superelastic NiTi specimens. Typically, ASTM F2516-06 Standard Test Method for Tension Testing of Nickel-Titanium Superelastic Materials is employed and lists specific test rates to be utilized. In order to allow for heat dissipation that occurs during the austentite to martensite transformation portion of the test, slow test rates are required within this method to ensure that test results are not affected. This study will compare three different test rates (1X, 2X, and 3X of the ASTM test method rate) for two different diameter NiTi wire materials at two different temperatures (ambient and 37C). Additionally, the tests will be replicated in a water bath at 37C. The data will be examined to determine if the heat effect is a valid phenomenon and if test speeds could be increased within a particular test environment without influencing the materials properties and subsequent results.