The effect of approach direction on damage in MgO due to spherical particle impact

The damage produced by spherical particle impact against {1 0 0} surfaces of MgO has been investigated over a range of impact angles for a fixed particle velocity and over a range of particle velocities for a fixed impact angle. The mass of material removed by each impact was determined gravimetrically, and the crater and surrounding damage were studied by means of surface profilometry and scanning electron microscopy. A numerical computer model of the crater formation process was developed which was able to predict crater geometries in close agreement with those observed experimentally. This same model also provided estimates of the dynamic hardness, the contact time and the energy transmitted to the surface during the impact. The mean dynamic hardness was ~ 25% less than that measured in previous normal impact studies [1] on MgO of similar static hardness. The contact time and energy calculations give some insight into the reasons why the energy balance model, which successfully describes the velocity dependence of mass loss under normal impact conditions, breaks down for oblique impact.