Back-Stress Effect on the Mechanical Strength of TWIP-IF Steels Layered Sheet

Although back-stress contributes to the mechanical properties of materials, the degree of strength enhancement from back-stress is not easy to estimate. In this research, back-stress hardening of twinning-induced plasticity (TWIP) + interstitial free (IF)-layered steel sheets were estimated by implementing a non-linear combined isotropic and kinematic hardening model. High back-stress evolution occurs due to plastic strain incompatibility between a TWIP-steel core and IF-steel sheath, and the strength of TWIP + IF layered steel sheath is greater than the strength estimated by the rule-of-mixtures. A non-linear combined isotropic and kinematic hardening model was used to estimate the strength enhancement from back-stress hardening, and the simulation results were correlated with the experimental results. This result shows that the back-stress evolution in heterogeneous materials contributes to their strength, and that the non-linear combined isotropic and kinematic hardening should be included to estimate the degree of back-stress hardening.