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 ductil e and brittle materials. Crack growth is considered to be a mutual competit ion between intrinsic mechanisms of crack advance ahead of the crack tip, w hich promote crack growth, and extrinsic mechanisms of crack-tip shielding behind the tip, which impede it. In this paper, we examine and model the wi dely differing nature of these mechanisms, with emphasis on behavior in cer amics at ambient and elevated temperatures, and compare their specific depe ndencies upon the alternating and maximum driving forces (e.g., Delta K and K-max), thereby providing a useful distinction of the process of fatigue-c rack propagation in these different classes of materials. Published by Else vier Science Ltd.