Evaluation of slip line theory assumptions for integrity assessnment of defected welds loaded in tension

Abstract

To assess the safety and reliability of a structure under working conditions, integrity assessment is a major requirement. In case of welded structures, the presence of imperfections is an impediment for the fitness-for-service. The existence of local strength variations in the weld region and the softening or hardening of heat affected zones gives rise to complexities for the assessment of weld defects, which are not yet fully understood. This paper is concerned with the plasticity analysis defected welded connections loaded under uniaxial tension, using the concept of slip line field theory. In a joint research project between Ghent University and University of Maribor, an attempt is made to understand the development and trajectory of slip lines derived from deformation bands. This paper reports on the results of an experimental program, supported by finite element analysis. Single Edge notched Tension (SE(T)) specimens were extracted from butt-welded steel (S690 QL) plates. Deformation bands were derived using Digital Image Correlation (DIC) and characterized by devoted post-processing. The attained results are a basis for the development of an analytical crack driving force estimation scheme that considers weld heterogeneity. Such scheme is expected to assist in the improvement of standardized defect assessment procedures.