Dynamic Response and Failure Behavior of U71Mn Using a Hat-Shaped Specimen

The split Hopkinson pressure bar and universal testing machine are used to study the dynamic response and failure behavior of U71Mn using a hat-shaped specimen under the compression-shear stress state. The shear stress–strain curves are presented at the shear strain rates ranging from 0.001 to 19,200 s−1 and temperatures ranging from 25 to 600 °C. It is observed that the effects of strain rate hardening, strain hardening, and thermal softening are closely related to the changes of the shear stress–strain curves. The coupling effects are very significant in the process of deformation failure. The fracture morphology and longitudinal section microstructures of U71Mn are investigated by scanning electron microscope. According to the results, the shear strain rates and temperatures greatly influence the failure mechanisms of the material. Furthermore, the increase in temperature promotes the occurrence of dynamic recrystallization and reduces the tendency of the pearlite flowing toward the center of the shear zone. Based on the quasi-static tensile tests and finite element analysis, the Johnson–Cook damage model parameters are fitted and applied to the finite element analysis of the hat-shaped specimen.