Destructive Testing and Nondestructive Evaluation of Alumina Structural Ceramics

Large-scale 3D modeling of projectile impact damage in brittle plates

“…This failure mode, known as "radial" cracking, is characterized by multiple planar cracks propagating simultaneously in radial directions from the impact region. Similar to the axisymmetric fracture modes, radial cracks have been observed in impact experiments on a variety of brittle materials (Evans and Wilshaw, 1977;Evans et al, 1978;Ball and McKenzie, 1994;Sherman and Brandon, 1997;Sherman, 1997Sherman, , 2000Sherman and Ben-Shushan, 1998;Normandia et al, 2004;Hsieh et al, 2004;Brennan et al, 2010). Fig.…”

“…Correspondingly, radial cracks have been observed to nucleate well below the impacted surface either in the specimen volume (Evans and Wilshaw, 1977) or on the opposing back surface of the plate. The plate back surface can be either a free boundary for unsupported plates (Ball and McKenzie, 1994;Sherman, 1997;Hsieh et al, 2004) or a material interface for a plate with a backing support (Sherman and Brandon, 1997;Sherman and Ben-Shushan, 1998;Sherman, 2000;Normandia et al, 2004;Brennan et al, 2010). Radial cracks greatly complicate the analysis of damage in impact scenarios because of their tendency to nucleate in subsurface regions and because they require a fully three-dimensional analysis for a problem that could otherwise be studied in two dimensional axisymmetric mode.…”

“…Ring cracks are characterized by their average radius which is measured from the central impact point. Both conical and ring cracks are ubiquitous features of brittle impact damage and have been observed in impact experiments on a variety of different brittle materials including glasses (Knight et al, 1977;Ball and McKenzie, 1994), nominally brittle polymers (Hsieh et al, 2004), and ceramics (Bowden and Field, 1964;Evans and Wilshaw, 1977;Evans et al, 1978;Maekawa et al, 1991;Sherman and Brandon, 1997;Sherman, 1997Sherman, , 2000Sherman and Ben-Shushan, 1998;Normandia, 2004;Iyer, 2007;Brennan et al, 2010;Deshpande et al, 2011).…”

Plastic deformation of polycrystalline alumina introduced by scaled-down drop-weight impacts

“…In doing so, we aim to expose a phenomenon after recent DW tests performed on fully-dense monolithic alumina ceramics generated a crater of marked depth and a residual damage zone far beyond anything produced by comparable quasi-static indentation tests. Despite similar DW setups and other "dynamic indentation" tests being performed by other workers [11][12][13], this response of the material remains undocumented. We believe that, once instrumented, such a method could be useful in helping us understand dynamic damage in different ceramics, as well as provide a viable method for screening armour, aerospace and dentistry ceramics for better performance in advanced ceramic research.…”