An insight of the structure of stress fields for stationary crack in strength mismatch weld under plane strain mode-I loading—Part I: Pure bending specimen

In-service inspections of many nuclear power plants have revealed that cracks are most likely to occur in or the regions near the weld. Interfacial cracks under elastic as well as in elastic–plastic conditions have already been extensively discussed in literature. However, the problem of crack lying at the centre of weld is less understood. Though several detailed numerical studies have been performed to investigate the influence of weld strength mismatch on crack-tip stress fields till date, however, the detailed insight of the structure of stress fields under large scale plasticity is still lacking. The present article is intended to bridge that gap. In this work, detailed structure of the global plastic fields which occur in a deeply cracked (a/W>0.3) mismatch welded pure bending specimen, under fully plastic condition, is presented. Aspects related to the state of stress at the interface of two materials are discussed. It is shown that a family of five fields proposed in this work is adequate to cover all practical cases of weld mismatch. Proposed fields were confirmed by detailed full-field finite element analyses. Excellent agreement is observed between the proposed theoretical solutions and the numerical results.