A Modified Split Johnson-Cook Model of CL65 Wheel Steel for Prediction of Dynamic Compression-Shear Failure

The wheel-rail contact area experiences dynamic compression-shear damage caused by skidding, abrupt braking, or excessive traction, encompassing dynamic impact, nonlinear plastic deformation, and failure. This paper systematically investigated the plastic constitutive and failure models of CL65 steel and explored the dynamic compression-shear failure behavior by combining dynamic SHPB tests with the finite element model (FEM) of the hat-shaped specimens. Firstly, a modified split Johnson-Cook model (MSJC model) for CL65 was proposed based on the Split Hopkinson Pressure Bar (SHPB) test with the cylindrical specimens, achieving a coefficient of determination (R²) value of 94.48%. Secondly, the Johnson-Cook damage model for CL65 was determined through the quasi-static tensile tests on the notch specimens and a reverse identification framework constructed by ISIGHT. The correlation coefficients R of the reflected and transmitted waves between the SHPB test and the FEM of the hat-shaped specimen were 93.86% and 96.78%, respectively. Finally, it is found from the dynamic compression-shear failure behavior of CL65 that the applied force declined due to the emergence of defects (voids and cracks) and thermal softening. Localized severe plastic deformation and adiabatic heating within the shear band led to the formation of the adiabatic shear band (ASB). The ultrafine equiaxed grains and adiabatic temperature rise promoted the occurrence of dynamic recrystallization. The ASB exhibited the characteristics of white etching layers, with a microhardness of about 930.7 HV, consisting of austenite, ferrite, martensite, and cementite.