ABSTRACT
In 1958, Kachanov (1958) introduced the concept of effective stress in damaged materials. This pioneering work started the subject that is now known as continuum damage mechanics. Research in this area has steadily grown and reached a stage that warrants its use in today’s engineering applications. Continuum damage mechanics is now widely used in different areas including brittle failure (Krajcinovic, 1983, 1985; Krajcinovic and Foneska, 1981; Lubarda et at., 1994; Ju and Lee, 1991; Lee and Ju, 1991; Ju and Chen, 1994a,b), ductile failure (Lemaitre, 1985, 1986; Chaboche, 1979, 1981, 1988a,b; Chow and Wang, 1987), composite materials (Allen et al., 1987; Boyd et al., 1983; Voyiadjis and Kattan, 1993, Voyiadjis and Park, 1995a, b) and fatigue (Chow and Wei, 1991 ). In this theory, a continuous damage variable is defined and used to represent degradation of the material which reflects various types of damage at the micro-scale level like nucleation and growth of voids, cavities, micro-cracks, and other microscopic defects.
