Bridging between Heterogeneous Local Strain Distribution and Macroscopic Stress-strain Curves

Abstract

A modified continuum composite model was utilized to analyze the stress–strain behavior of as-quenched steels with a fully martensitic microstructure. The model was employed to express the stress–strain curves obtained by a simple tensile test and those obtained by forward and backward loading using a simple shear test machine. The study confirmed that the model can represent the stress–strain behavior under both forward and backward deformation. In addition, the evolution of local strain distributions during plastic deformation was investigated using a digital image correlation method. The strain distributions and their evolution during deformation were qualitatively represented using this model. The discrepancies between the model calculations and experiments are due to the limitations of the iso-work assumption and the impact of slip deformation on the macroscopic work-hardening behavior of martensitic steels. Highly strain-concentrated regions aligned along the longitudinal direction of the lath and block, known as in-lath-plane slips, may not play an important role in the work-hardening behavior of as-quenched martensitic steels. However, the other slips, namely the out-of-lath slip, may play a significant role in the work hardening of as-quenched martensitic steels.