Internal variable modeling of the high strain-rate behavior of metals with applications to multiphase steels

A phenomenological constitutive model with a single internal parameter is proposed to characterize the behavior of metals for a large range of strain-rate. The flow stress is defined as the sum of an internal stress, representing long range interactions, with an effective stress which is thermally activated. The internal stress is a function of a single internal parameter which allows us to describe strain-hardening effects. This model is used to reproduce the behavior of four multiphase cold rolled steels which are new high performance materials for the automotive industry. The model predictions show a very good agreement with experimental results for a wide range of strain-rate 8 × 10−3 s−1 ≤ ε˙ ≤ 103 s−1. In addition, strain-rate history effects are well accounted for.