Constitutive model of 42CrMo steel under a wide range of strain rates based on crystal plasticity theory

To study the mechanical properties and the stress-strain relationship of 42CrMo steel, we subjected it to quasi-static compression and tension testing and dynamic compression testing. The results show that a strain-rate effect is evident under both quasi-static and dynamic loading. There is competition between the strain hardening and thermal softening caused by adiabatic temperature rise. The material's behavior is symmetric under tensile and compressive loading. Thermal activation theory is used to explain the deformation mechanism. Different activation conditions and the high strain-rate sensitivity of the Peierls stress are the main causes of the different mechanical properties observed in response to the quasi-static and dynamic loadings. A modified model based on the crystal plasticity theory is proposed. The macroscopic strain rate was considered in the evolution of the shear rate, and temperature rise was considered in the hardening rules. The model was confirmed to describe the quasi-static and dynamic mechanical behavior of the 42CrMo steel very well, especially the effects of strain hardening and thermal softening.