Dynamic mechanical response and a constitutive model of 42CrMo steel that incorporates the effects of high strain rates

Abstract

<p indent=0mm>To study the dynamic mechanical properties and constitutive relationship of 42CrMo steel, which is primarily used in high-speed train axles, a dynamic compression test and a metallographic observation were conducted. The material exhibited strong strain-rate dependence, and the adiabatic shear behavior under dynamic loadings was found to be the dominant cause of the different mechanical properties resulting from different strain rates. The thermal activation theory, which separately considers the thermal and athermal stresses to explain the deformation mechanism, was employed to obtain the descriptions of the strain-rate effects. Accordingly, a physically based constitutive model was proposed that incorporated the effects of the high strain rates. A criterion for adiabatic shear, which was coupled to the model, was proposed to determine the onset of instability. The model was confirmed to sufficiently describe the quasi-static and dynamic mechanical behavior of the 42CrMo steel, especially the effects of strain hardening and strain rates on the yield stress.