High strain rate indentation-induced deformation in alumina ceramics measured by Cr fluorescence mapping

Alumina materials with a range of grain sizes and purities were subjected to small-scale dynamic impact by sharpened tungsten carbide projectiles at sub-ballistic velocities. The resistance of the materials to fracture was recorded by visual examination of the cracking on the impacted surface and the damage in the subsurface region. The residual stress and plastic deformation induced in each material were examined using Cr³⁺ fluorescence mapping. A modified Hertzian indentation model of the stress state in the material with the addition of a blister field representing the stress induced by the presence of the subsurface plastic zone was found accurately describe the observed cracks beneath the surface of the material, as well as the radial cracks on the surface.