Mechanics and mechanisms of fatigue damage and crack growth in advanced materials

The mechanisms of fatigue-crack propagation in ceramics and intermetallics are examined through a comparison of cyclic crack-growth behavior in ductile and brittle materials. Crack growth is considered to be a mutual competition between intrinsic mechanisms of crack advance ahead of the crack tip, which promote crack growth, and extrinsic mechanisms of crack-tip shielding behind the tip, which impede it. In this paper, we examine and model the widely di€ering nature of these mechanisms, with emphasis on behavior in ceramics at ambient and elevated temperatures, and compare their speci®c dependencies upon the alternating and maximum driving forces (e.g., DK and Kmax), thereby providing a useful distinction of the process of fatigue-crack propagation in these di€erent classes of materials. Published by Elsevier Science Ltd.