This paper quantifies the effect of geometry (planar or cylindrical) and crack location (internal or edge cracks; weld center or interface cracks) on crack driving force for welded joints, via systematic elastic-creep and elastic-plastic finite element (FE) analyses for welded joints. For engineering estimates of crack driving forces for mismatched welded joints, the equivalent material approach is employed. It is found that the equivalent material concept works very well only for a planar geometry with an internal crack, such as the middle cracked tension specimen. For a planar geometry with an edge crack, it works reasonably well, but tends to provide conservative results for under-matching and for interface cracks. For a cylindrical geometry with an edge crack, the results are similar to those for a planar geometry with an edge crack, but caution should be exercised for over-matching, as non-conservative estimates are possible due to gross-section yielding. For a cylindrical geometry with an internal crack, excessively conservative estimates for under-matching are found, and thus an improved estimation method is desired.
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