Tensile and compression performance of superelastic NiTi tubing

Abstract

Stress–strain curves have been established in tension and compression at 19 and 37°C for a NiTi tube with an A _f temperature of -8.5°C. In tension, the first strain cycle exhibited the familiar flag shape but this gradually decayed on cycling into a sigmoidal curve with an accompanying build up of residual strain. Changes were rapid at first but slowed down to an approximately steady state condition after ∼40 cycles. In compression, sigmoidal stress–strain curves were observed from the beginning, but these also changed and residual strain built up on cycling. In order to account for the behaviour in the superelastic regime, attempts have been made to draw on interpretations that have been advanced for similar differences and changes on cycling in the shape memory regime.