Compressive Strength and Damage Mechanisms in Ceramic Materials. I. Temperature-Strain Rate Dependence of Compressive Strength and Damage Mechanism in Aluminum Oxide. II. Threshold Microfracture during Elastic-Plastic Indentation

摘要

The results of compression tests of Al2O3 performed over a wide range in temperature and strain rate are interpreted in terms of dominant damage mechanisms. It is shown that compressive failure in Al2O3 is caused by one of three different mechanisms, each based on tensile (Mode I) growth of predominantly axial microcracks, and each characteristic of a specific temperature-strain rate regime. The concepts developed should be applicable to other strong ceramics. In addition, indentation experiments were carried out for a variety of ceramics. It is found that the threshold for microfracture during elastic-plastic indentation corresponds to radial, rather than subsurface median, crack formation. This is contrary to the fundamental assumption of existing models for threshold crack nucleation by sharp indenters or particles; the results indicate the need to modify the stress field calculations used in these models. (Author)