Prediction of the fatigue strength of welded joints based on the statistical size effect

With increasing length of welding seams the fatigue strength decreases. This effect is confirmed in fatigue tests on butt joints and cruciform joints. The influence of the length of the welding seam on the fatigue strength depends on the scatter of the parameters meters describing the geometry of the welding seam. The theory of the statistical size effect worked well in fitting and predicting the test results. The fatigue strength of welded joints is well predicted, if no other influences like e.g. residual stresses change the fatigue strength. Additionally a method for the calculation of crack propagation is proposed, which takes in account angular and linear misalignment as well as local changes of the geometry of the welding seam.