VIRGINIA POLYTECHNIC INST AND STATE UNIV BLACKSBURG DEPT OF MATERIALS ENGINEE RING
A study was conducted of the role of crack formation in the non-linear stress-strain behavior of a fine-grained polycrystalline aluminum oxide at high temperature under conditions of displacement-rate-controlled mechanical loading. The observed deformation behavior could be divided into three regimes. At the lowest values of deformation rate the load levelled off to a constant value without crack formation, consistent with deformation by diffusional creep. Over a range of intermediate values of deformation considerable non-linear deformation took place, manifested by a decrease in stress with increasing strain as the result of strain-softening due to the formation and growth of cracks. At the highest rates of displacement, specimen fracture occurred by the formation of a single crack without significant non-linear deformation and without the formation of additional cracks. These results are discussed in terms of the general mechanisms and kinetics of the deformation of non-ductile solids. Keywords Crack propagation Cracking Ceramics Aluminum Crystal lattices Composite materials.