2011:19 Experimental evaluation of influence from residual stresses on crack initiation and ductile crack growth at high primary loads

Cracked components are usually subjected to loads causing both primary and secondary stresses, e.g. welding components. Engineering assessment approaches, such as the ASME XI code and the R6 procedure, are commonly used to conduct integrity assessment of such components. There has been an ongoing debate how to treat secondary stresses using engineering assessment methods. The nature of these assessment approaches is to give reasonably conservative assessments. These two approaches treat the issue of secondary stresses differently. The ASME XI code does not consider weld-induced residual stresses in some materials, for instance stainless steel welds. The R6-method on the other hand tends to give overly conservative assessment results.

The significance of the secondary stresses for cracks in ductile materials within nuclear applications has been studied earlier using an analytical approach by a SSM-financed study (SSM Research Report 2009:27). In that study a deterministic safety evaluation procedure was proposed in which the residual stresses were weighted down for sufficiently ductile materials. In the current study this safety evaluation procedure is investigated by performing experiments.