Macroscopic versus local strain rates during tensile testing of pseudoelastic NiTi

During tensile testing of pseudoelastic NiTi, martensitic transformation bands propagate through the specimen. We compare stress–strain curves for different gauge lengths and cross-head displacement rates (CHDRs) to demonstrate that the CHDR is a physically meaningful measure that unambiguously characterizes the thermomechanical loading situation. This allows estimation of local strain rates, which are determined for the first time by considering the finite width of mesoscale phase interfaces. Local rates and macroscopic strain rates differ by at least one order of magnitude.