Correlations of Computed Simulations with Residual Hardness Mappings and Microstructural Observations of High Velocity and Hypervelocity Impact Craters in Copper

Abstract

An AUTODYN 2D (version 3.0), PC-compatible hydrocode utilizing Lagrangian and Eulerian processors (the latter including a fracture criterion) with a Johnson-Cook constitutive relationship has been applied to simulating experimentally developed impact craters in 1.3 cm thick OFHC copper targets for 1100 aluminium spheres (nominally 3.2 mm diameter) impacting at velocities ranging from 1.08 to 6.01 km/s. Good validation was achieved not only for crater dimensions but especially for the simulation of crater shapes and other features — including fractured or particulated crater rims, target spallation at 4.4 and 6.01 km/s and residual stress contours extending from the crater wall; which were related to residual, experimental hardness profiles and crater-related microstructures observed by optical and transmission electron microscopy. This comprehensive validation of 2D hydrocode simulations allowed extrapolations for impact craters well into the hypervelocity regime: 12 and 24 km/s, where dynamic recrystallization was demonstrated to contribute significantly to hypervelocity impact crater formation.