Subcritical Crack Growth

Abstract

Publisher Summary This chapter discusses subcritical crack growth, which is usually the result of a stress-enhanced reaction between the ceramic and ambient moisture. The effect of subcritical crack growth on the strength of ceramics can be understood by using the science of fracture mechanics, which provides methods for quantifying crack growth. Crack growth in ceramic materials is characterized using experimental techniques developed from fracture-mechanics considerations. Regardless of the technique used to characterize crack growth, the crack velocity can be expressed as a unique function of the stress intensity factor. Theories to explain subcritical crack growth in ceramic materials can be divided into three categories: diffusion theories, plastic-flow theories, and chemical-reaction theories. The development of a large body of crack growth data for ceramic materials permits detailed comparisons between the crack growth data and the data obtained by more conventional strength measurement techniques. Accepting the premise that subcritical crack growth is the main cause of strength loss in ceramic materials, the science of fracture mechanics can be used to develop practical methods for predicting failure.