Development of the Z Specimen for Tensile-Tensile, Tensile-Compression, Compression-Compression Wire Testing

A new wire test specimen was developed as part of the Safe Technology consortium project to produce a nitinol algorithm for the fe-safe^™ fatigue postprocessor. The requirements for the design were permit tensile and compressive loading, accommodate data collection of strains from ±0.1 to 6% at high-frequency cycling. The requirements for the wire were inexpensive, stable, consistent, and commercially available. The requirements for the processing were incorporate deformation and multiple anneal cycles to simulate manufacturing methods associated with vascular stent production. The final design was 0.508 mm (0.020 in.) diameter wire formed in a two-stage process to produce a Z-shaped specimen. The final part met all requirements for testing. Subsequently, a second specimen, Z3, and a straight wire specimen were produced to supply additional data to the consortium.