Modelling of microparticle hypervelocity oblique impacts on thick targets

For hypervelocity impacts the effects of impact angle obliquity on final crater morphology have been studied using the hydrocode AUTODYN-3D. The target material and velocity ranges have been chosen so that they correspond with typical space debris impacts on orbital spacecraft situations, such as NASA's LDEF and ESA's Eureca. The hydrocode calculations were first validated against oblique impact experiments for 1 mm aluminum spheres on aluminum at 6.5 km/s and for the normal impact of 1 mu m iron spheres on copper at 16 km/s. The main study was for 1 mu m aluminum and iron spheres impacting aluminum at velocities of 6.5, 10 and 16 km/s and impact angles from 0 degrees to 85 degrees. Results are presented which show the calculated relationships between the impact angle, and the main crater length, width and depth. A study of projectile size effects has also been performed by carrying out calculations for several different projectile sizes ranging from 1 mm to 1 mu m. The calculations used strain-rate dependent material models and the results suggest either that departure from exact size scaling cannot be explained by strain rate effects, or that the Johnson-Cook model used is not appropriate for the higher strain rates experienced in the case of smaller size projectiles. The calculations demonstrate that Lagrangian techniques, when coupled with an erosion algorithm, can be used for hypervelocity impact calculations, however care must be taken to use an appropriate erosion criterion.