CRACK STABILITY AND T-CURVES DUE TO MACROSCOPIC RESIDUAL COMPRESSIVE STRESS PROFILES

Stabilization of the fracture process and resistance to strength degradation have been observed for materials with increasing T-curves. In this study, the possibility of using residual compressive stresses to induce crack stabilization is examined theoretically. Nonmonotonic forms for the residual compressive stress profiles are assumed. The stress intensity factors for linear through-the-thickness cracks subjected to these profiles are derived. The stress intensity factors are then used to construct the T-curves for the stress profiles considered. It is demonstrated that the presence of these T-curves leads to crack stability under the action of applied tensile stresses, and to strength insensitivity to the initial flaw size. The effects of additional localized stress fields (similar to those produced by indentation) on crack growth in these materials are also considered. In this case, the strength is found to be relatively insensitive to the magnitude of the localized loading. It is therefore concluded that residual stresses can be used to improve mechanical reliability in ways which are usually associated with microstructural toughening mechanisms.