Luders band evolution in geometrically graded NiTi plates

This study investigated the process of the Luders band formation and propagation within geometrically graded plate samples of a pseudoelastic NiTi during the stress-induced martensitic transformation by means of digital image correlation full-field strain measurement. The geometrically graded plate samples had parabolic width profiles in concave and convex forms along the length. Such sample geometries created a situation of progressively increasing applied load and a continuous variation of the sample width during the process of the stress-induced transformation. The size (along the sample length direction) of the Luders band front transition zone was found to remain unchanged with variation of the sample width during the process, but the local strain rate across the transition zone was varied. The transition zone of the martensite Luders band during the forward transformation was wider than that of the austenite Luders band on the reverse transformation, and the local strain rate was lower than that of the latter.(c) 2022 Elsevier B.V. All rights reserved.

Automated summary

This study examines the formation and propagation process of Luders bands in parallel-graded NiTi samples during stress-induced martensitic transformation. Digital image correlation is used to measure the full-field strain. The samples with varying width profiles experience progressively increasing load and continuous variation of width during the transformation process. The size of the Luders band front transition zone remains constant, but the local strain rate varies. The transition zone of the forward transformation is wider and has a lower strain rate compared to the reverse transformation.