Strain path dependency in metal plasticity

Abstract

A change in strain path has a significant effect on the mechanical response of metals. Strain path change effects physically originate from a complex microstructure evolution. This paper deals with the contribution of cell structure evolution to the strain path change effect. The material with cells is modelled to behave like composite consisting of a periodic 2D array of two types of elements: the hard cell walls and the soft cell interiors. For the scalar internal variables figuring in the model, the cell size, the wall thickness and the dislocation density inside the walls, evolution equations are proposed to describe the cell development and the cell dissolution. The validation of the model is performed by comparing the results with experimental data on the deformation behaviour of copper which was subjected to a sequence of two uniaxial tensile tests performed in different directions. The model is concluded to be capable to describe the material behaviour for monotonic deformation and complex deformation with a strain path change up to 45° The model predicts the strain path change, its dependency on the amount of prestrain and on the amplitude of the strain change that are in good agreement with experimental data. The slip anisotropy should be taken into account to improve the model for an adequate prediction of the deformation behaviour after strong strain path changes.