Assessment of uncertainties in life prediction of fatigue crack initiation in rails – influence of residual stresses from manufacturing

Paper in proceeding, 2007

The risk for initiation of fatigue cracks in the web in the weld zone of a rail is studied. The interaction between the welding residual stress field and the stress field caused by service loads is simulated in a nonlinear finite element (FE) analysis where the welding residual stress distribution (shape) and magnitude, the service load magnitude, and the material parameters used in the fatigue life estimation are varied. The initiation of fatigue cracks is assessed using the shear-stress-based multiaxial fatigue criterion proposed by Dang Van. In addition, the accuracy in the fatigue life assessment is evaluated by statistical uncertainty analysis where the variances according to the Gauss approximation formula are studied. It is seen that the welding residual stress enhances the risk for fatigue crack initiation in the rail web, and that the uncertainty in load level dominates the uncertainty in the fatigue assessment.