TWI Industrial Member Report Summary 551/1996
H G Pisarski and M R Goldthorpe
In fusion welded joints there is, inevitably, a difference in the strength between the parent material and weld metal. However, when conducting structural integrity assessments of flaws located in the weld metal, the difference in strength is usually ignored; the welded component is assumed to be homogeneous with respect to tensile properties. For example in BS PD 6493:1991 yield strength mismatch is not addressed except in the treatment of residual stresses. Provided that the stresses are low, ignoring strength mismatch is unlikely to be of consequence. However, at higher stresses this may not be the case. Means of allowing for yield strength mismatch between the weld metal and parent material when conducting flaw assessments is being explored by TWI and EWI. This report describes the results of experiments and numerical analyses to understand the behaviour of semi-elliptical surface cracks in welds when loaded in tension. The effect of weld metal strength undermatching as well as overmatching the strength of the parent material is investigated. The implications of ignoring strength mismatch when conducting flaw assessments is explored.
- To compare the results from 3-D finite element analyses with experiments to see how well mismatch could be modelled
- To assess the implications of ignoring mismatch when conducting flaw assessments