Evaluation of the Crack Layer Theory Employing a Linear Damage Evolution Approach

The general applicability of the Crack Layer theory to characterize the resistance of materials to fatigue crack propagation has been hindered by the difficulties encountered in developing a unified unit of measuring the various damage species asso ciated with crack advance. Moreover, some materials do not display obvious damage that can easily be quantified from post-failure examination of the fractured specimens. To over come these problems, a modification of the Crack Layer theory has been developed. Fol lowing the Irwin plastic zone shape evolution, a linear relationship between the width of the active zone and the crack length is assumed. This assumption has been found to be justified in all of the materials that have so far been characterized using the Crack Layer model.