Experimental Investigation and Constitutive Description of Railway Wheel/Rail Steels under Medium-Strain-Rate Tensile Loading

The uniaxial tensile mechanical properties of D1 wheel steel and U71MnG rail steel were investigated experimentally at a wide range of strain rates from 0.0001 to 100 s⁻¹. Influence of the strain rate on stress–strain response, ductility, fracture morphology and energy absorption was analyzed and discussed, respectively. Both D1 wheel steel and U71MnG rail steel are demonstrated to be strain rate sensitive, and D1 wheel steel specimens generally exhibit a larger elongation and a better ductility than U71MnG rail steel specimens at each strain rate. The fracture mechanism of D1 wheel steel is a ductile fracture at lower strain rates and quasi-ductile fracture at higher strain rates, while U71MnG rail steel tends to a quasi-ductile fracture at lower strain rates and a brittle fracture at higher strain rates. The specific energy absorption values of D1 wheel steel and U71MnG rail steel increase with the increase in true strain and elevated strain rate. Finally, the Johnson–Cook model is adopted to predict the stress–strain response of wheel/rail steels studied, and a better agreement is found.