Spall Resistance of Alumina.

摘要

The spall strength of alumina bars was determined using a bar impact apparatus. The fracture morphology in the region of maximum tensile stress caused by the transient wave was investigated using a scanning electron microscope. No microcracking was detected away from the spall plane and the fracture toughness of the unspalled bar remained unchanged with increasing velocity. The ultimate goal of this research project is to study the residual strength of monolithic ceramics and ceramic/ceramic composites. The results of such a study can be used to design engineered ceramic composites with higher impact resistance. In order to achieve this goal, an impact test, which is a variation of the plate impact test, was developed. The plate impact test produces a one-dimensional compressive square stress pulse, which neglects the effects of lateral inertia caused by Poisson's effect, propagating from the impact face at the speed of sound. The impactor is made of the same material and its length is half of the specimen length. A stress pulse, with a length equal to the specimen length, is thus produced. Keywords: Fracture mechanics; Ceramics; Alumina. (kt)