Published: Jan 2011
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Starting from James Rice's classical work on cyclic plastic stresses and deformations in the plastic zone of a Mode III loaded crack, it will be shown that the crack tip opening displacement of a Mode I crack in a work hardening material can be written in analytical form. This result was then used to formulate the blunting line for J-integral testing and to estimate the fatigue crack propagation rate of a number of materials. In a similar manner—based on the strain distribution within the plastic zone of a work hardening material—the initiation of crack extension under static loading was estimated. The stress distribution ahead of a crack and the Ritchie, Knott. and Rice model were applied to the ductile-to-brittle transition of ferritic steels as well as the transition temperature shift due to neutron irradiation. Inspired by Fong Shih's contribution to the Electric Power Research Institute Handbook, a simple but straightforward method for expressing the 85 crack opening displacement as a crack driving force for fully plastic conditions was developed, finally ending up in a comprehensive assessment method for cracked components. The application to mismatched welded joints was demonstrated to be possible if the yield load for mismatch is available; this latter task was performed using both slip line theory and finite element (FE) analyses. Application examples of these models will be shown, and it will be seen that estimates using these models are in reasonable agreement with experimental results and FE analyses. Several elements of these models have made their way to international codes and standards.
fatigue crack propagation, crack tip blunting, structural assessment, ductile-to-brittle transition, crack opening displacement, ductile tearing
Consultant, Technische Universität Hamburg-Harburg; Ruhr-Universität Bochum, Vögelsen (Lüneburg),