Dynamic Fracture Strength of 90% Tungsten Alloys

Dynamic fracture strength of tungsten alloys generated with a round bar Charpy specimen impacted at velocity ranging from 25 to 160 m/s has been reported to increase with loading rate. For as sintered alloys, the Charpy energy reached 1150 J/cm2 at 145 m/s, which is about 4 times the conventional Charpy energy obtained at 5 m/s. The analysis of the main failure process does not provide an explanation of this high level of failure energy.Additional post-mortem analyses have been conducted revealing a failure process involving multiple tensile cracks at the higher impact velocity. Consequent numerical simulations reproducing this failure process with the hydrocode AUTODYN have provided insights on the increase of the Charpy energy with impact velocity. The simulations were conducted with a modified Johnson-Cook model reproducing the observed strain rate dependence in the thermally and viscous regime, and with erosion strain criteria to trigger the failure process.