TWI Industrial Member Report Summary 638/1998
S D Smith
All welded joints will contain welding residual stresses and some degree of tensile property variation across the joint. Recommendations for dealing with these aspects in structural integrity assessments are given in PD 6493: 1991. The efficacy of these recommendations is reviewed by reference to recent publications.
Flaws in welded joints experience loading from welding residual stress in addition to the applied stresses from external loads. The driving force applied to flaws in welds therefore depends on the interaction of the applied loads and the residual stresses. The driving force is also affected by the development of plasticity at the crack tip which may be influenced by the difference between the weld metal and base metal yield strength (known as weld metal mismatch or simply as mismatch). Residual and applied stress interaction, and weld metal mismatch will affect flaw assessments to PD 6493: 1991. The PD 6493: 1991 methods for including residual stresses and mismatch have been assessed in recent published research. This literature is reviewed.
The objective of this review is to present published literature on the effect of welding residual stresses and weld mismatch on flaw assessments and to comment on how this published work affects PD 6493: 1991.