Fatigue assessment of welded joints using critical distance and other methods

This paper describes an investigation into four different methods for predicting high-cycle fatigue behaviour in welded joints. Two of these methods (the crack modelling method and the notch stress intensity factor) are based on modifications of linear elastic fracture mechanics. The other two are methods to which we give the general name critical distance methods (CDM). The direct CDM approach uses stress values at critical distances from the weld, taken from finite element analysis. Another method (the stress averaging approach) achieves the same effect using a fictitious radius concept. When tested against a large body of experimental data from the literature, all four methods were found to give reasonable predictions of endurance limits for a range of weld types in both aluminium alloys and steels. The explicit use of CDM with FEA was found to give the best combination of high accuracy and ease of use. The methods were also applied to a specific case - fatigue in a T-shaped joint containing a drilled hole - which allowed us to study a typical industrial design problem involving competition between two different features.