Dynamic Constitutive Behavior and Fracture of Lanthanum Metal Subjected to Impact Compression at Different Temperatures and Impact Tension

Based on compressive tests, static on 810 material test system (MTS) and dynamic on the first compressive loading in split Hopkinson pressure bar (SHPB) tests at different strain rates and temperatures for Lanthanum (La) cylinder specimens, this study determined Johnson-Cook (J-C) type compressive constitutive equation of La metal. The determined compressive constitutive equation of La metal was calibrated in numerically simulating the recorded large deformations of La cylinder specimens generated by the multi-compressive loadings in SHPB tests. Based on tensile tests, static on MTS and dynamic on the first tensile loading in optimized tensile split Hopkinson bar (TSHB) tests at different strain rates for La sheet specimens, this study determined the J-C type tensile constitutive equation of La metal. It was found that the La sheet specimens were fractured during the first tensile loading in TSHB tests. The numerical simulations of transmitted and reflected pulses of TSHB tests for La sheet specimens using strain rate dependent failure strain criterion were consistent with the experimental data. The relation between dynamic failure strength and strain rates was discussed. From scanning electron microscope investigation of fractured La specimens, it was found that damage evolution patterns at high loading rates tend to become regular.