Analysis of kinking in elastoplastic materials with strain-softening behavior

Possibility and features of kinking in elastoplastic materials with strain-softening behavior are investigated. Kink band formation is viewed as a phase transformation problem, kink bands are modeled as locally-plastically deformed bands, discontinuity of stress and deformation gradient across interfaces between kink bands and un-kinked areas is considered, and continuity of traction and displacement across interfaces and the Maxwell relation are imposed. As an illustration, the kinking of a NiTi alloy strip under uniaxial tension is analyzed. An effective numerical method is used to solve the governing equations. The features of the solutions are described in detail. The predicted results are consistent with experimental measurements and can also be used to explain why kink bands spread along the length of specimens while the Maxwell stress keeps constant as observed in experiments.