基于应变的应变硬化指数演化行为研究

To accurately describe the stress and strain relationship of dual-phase (DP) high-strength steel sheet during deformation, the evolution behavior of strain hardening exponent of three kinds of dual-phase high-strength steel sheets was investigated experimentally and predicted by theoretical models. The true stress-true strain curves of three kinds of materials were obtained using unidirectional tensile testing machine and self-developed DIC strain measurement system. The variation history of strain hardening exponent was obtained based on the classical Hollomon flow stress model. It is found that the strain hardening exponents of three kinds of materials chang nonlinearly with the true strain. To better predict the evolution behavior of strain hardening exponent, the nonlinear mathematical model that can describe the change of its value was proposed. Combined with the classical Hollomon flow stress model, the modified Hollomon-n flow stress model based on the change of n value was proposed. Finally, the validity of the proposed model was verified by the true stress-true strain curves of three kinds of materials.