Some new methods for predicting fatigue in welded joints

This paper is concerned with the prediction of high-cycle fatigue behaviour in welded joints. Recently, we have developed some new approaches for predicting the effects of notches and other stress concentrations which have been successfully applied to solid parts, using stress data obtained from FEA. In the present work we consider the extension of the same theories to cover welded joints. Two basic constants are needed to characterise fatigue in the weld — equivalent to the plain fatigue limit and crack-propagation threshold in conventional materials. These parameters were obtained experimentally and used to predict test results for two different joint geometries: a T-shaped fillet weld and a butt weld. Further predictions were made using data from the literature, showing the effect of reinforcement shape on butt welds and the fatigue strengths of non-load-carrying cruciform fillet welds. In all cases predictions fell within 20% of experimental values. The methods can be easily interfaced with conventional FE software; predictions can be achieved with relatively low mesh densities.