Elasto-plasto overall response in single and mixed mode crack configurations

Stress--strain fields and strain energy density distribution in single and mixed mode crack configuration are discussed. To avoid stress singularity in the neighborhood of the crack tip, a proper physical--mathematical model has been devised, where plasticization effects are taken into account. Following the Dugdale model, a "continuous fictitious crack extension" is realized. In this way the original nonlinear boundary--value problem is reduced to a linear one that is of elastic-perfectly plastic type. The governing equations are derived within the mathematical framework of "free boundary problems", and the solution is evaluated by a numerical procedure based on the incremental loading method and the Williams' stress function. Experimental investigations, by using the optical method of caustics have been carried out, evaluating the SED distributions and the fracture angles for several crack configurations. Graphs. 21 ref.--AA