NUMERICAL SIMULATIONS OF FRAGMENTATION ONSET VELOCITY OF PROJECTILE IMPACT ON THIN BUMPER

The conventional spacecraft meteoroids and orbital debris shielding system is the Whipple shield. In general there is a threshold velocity that is just sufficient to shatter the projectile for each system consisting of a projectile and bumper. This velocity is known as the fragmentation onset velocity. To determine the fragmentation onset velocity experimentally, a number of experiments have been conducted with different projectile/bumper configuration. The numerical simulations of fragmentation onset velocity of different material projectile hypervelocity impacts on bumpers with different combination of impact velocities and bumper-thicker-to-projectile-diameter ratios (t/D) have been performed using the SPH technique of AUTODYN. The spherical projectile materials are aluminum, steel and copper. All bumper material is aluminum alloy 6061-T6. The simulation velocities were in the range of 1 km/s~7 km/s. The ratios of t/D were varied from 0.01 to 0.8. The material model contains Mie-Gruneisen (shock) equation of state, Steinberg-Guinan strength model, principal tensile stress failure model and Grady fragmentation failure model. The simulation results are given and compared with the experimental results. The simulation results are consistent very well with the experimental results. The effects of t/D and material shock impedance etc. on fragmentation onset velocity have been given in Figures and equations.