Effect of weld metal mis-matching on defect assessment procedures

The present paper presents the results of a comparative study on the application of CTOD- and J-design curves as well as the Engineering Treatment Model for mis-matched joints (ETM-MM) procedures to strength mis-matched welds. Inhomogeneous through thickness center cracked tensile (CCT) panels containing 20% undermatched (UM) or 25% overmatched (OM) welds have been tested and local, remote and gauge length strain measured. Defect assessment procedures, developed to predict the failure of engineering structures, use as an input the mechanical properties of either base or weld metal only and are rather sensitive to the mechanical properties and applied strain definitions. Therefore, the significance of the strain definition to be used in those procedures on their predictions of the crack driving force has been discussed. In contrast to the CTOD and J-design curves the recently developed ETM-MM for welded structures includes the mechanical properties of the weld and base metal. Its predictions of the CTOD (#delta#_5) have been compared with experimental results. The predictions of the CTOD and J-design curves are conservative only when the strain used is measured in the material with the lower yield strength (local strain for undermatching and remote strain for overmatching). However, very good crack driving force estimates were obtained by using the ETM-MM procedure for both over- and undermatched specimens. (orig.)Reprinted from: Proceedings of the 10. European conference on fracture (ECF-10): Structural integrity - experiments - models - applications. Schwalbe, K.H.; Berger, C. (eds.); published by EMAS Ltd. (1994) p. 1379-1395Available from TIB Hannover: RA 3251(94/E/71) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman