Strain-rate dependent tensile behavior of railway wheel/rail steels with equivalent fatigue damage: Experiment and constitutive modeling

Abstract

The actual and accurate dynamic constitutive relationship of railway wheel/rail steels is crucial to availably simulate the wheel-rail impact behavior in service, which has increasingly aroused great concern in the field of rail transport but the related studies have been rarely reported. In this study, the tensile mechanical behavior of D1 railway wheel and U71MnG rail steels was investigated at a wide range of strain rates, considering the practical impact loading and initial fatigue damage of the wheel-rail system. An equivalent fatigue damage test method was first established based on the finite element simulations and corresponding maintenance period, and then the dislocation density and void distribution of post-fatigue-tested specimens were detected with X-ray diffractometer (XRD) and X-ray computed tomography (XCT), respectively. The dynamic tensile tests on pre-fatigued wheel/rail steel specimens at the strain rate up to 2200 s−1 were subsequently conducted using a split Hopkinson tension bar (SHTB) apparatus. Finally, a modified Johnson-Cook (JC) model was developed to describe the plastic flow behavior of D1 railway wheel and U71MnG rail steels, where the variable strain rate hardening coefficient and initial equivalent fatigue damage were taken into account. Verifications for experimental data demonstrated the modified JC model can provide a good prediction for the rate-dependent tensile response of the wheel/rail steels with initial fatigue damage.