The tensile test is a critical tool in the processing and certification of Nitinol. In particular, testing of fine wire with high UTS values such as Nitinol is quite difficult as the vicing of the wires may affect the UTS result due to notch effects in the grips. On the other side the extensometer may have an impact on the fine wires too, as it disturbs the straightened sample due to some eccentric loading. Some users try to overcome these problems by applying laser or video systems for the strain measurement, but this equipment is not very common in many QA departments. However, the issue of gripping the fine wire remains basically unsolved.

There are a variety of methods currently used commercially. This poster aims to display the differences between the Cross Head Stroke and Extensometer methods. 

Three straight superelastic binary nitinol alloy wires were tested.  The wires were strained to 6%, unloaded and then pulled to failure.  Tests were done at ambient temperature and above the A_f for each alloy.