A unified approach for pressure and temperature effects in dynamic failure criteria

In most of the existing dynamic failure criteria, effects of temperature and pressure are ignored. In a few recent contributions, attempts to include initial temperature effects have been proposed. However, the combination of both temperature and pressure effects is still lacking in all existing criteria. The aim of the present work is to model the effects of both pressure and temperature on dynamic failure. We propose a unified approach that can be implemented within several dynamic failure criteria to simulate spallation at different initial temperatures and in a wide range of pressure. This approach is based on the scaling of the threshold failure stress similar to the scaling of the flow stress used in pressure dependent plasticity. This scaling uses the shear modulus for which we propose a thermodynamically based evolution law as function of temperature and pressure. For strain controlled failure, the threshold strain is also modified to account for triaxiality. We summarize existing dynamic failure criteria and we present our proposed approach for temperature and pressure effects as it applies to each of these criteria. Results from this approach are discussed and compared with experimental observations. As an illustration, we selected one of these failure criteria and applied it to simulate spallation in planar impact test. Predicted results for this test are also discussed in comparison with experimental observations.