Investigation of the behaviour of cracks in a dissimilar weld

Using the finite-element method the behaviour of an axial and a circumferential crack in a dissimilar weld of the ferritic steel X20 CrMoV 12 1 and the austenitic X10 NiCrAlTi 32 20 has been investigated. Stresses due to internal pressure and stresses resulting from temperature cycling due to different thermal expansion coefficients have been calculated. The circumferential crack located within the austenite in the region of maximum longitudinal stress is loaded at its deepest point by a stress intensity factor of 473 N mm-3/2. The axial crack is loaded up to a stress intensity of 325 N mm-3/2 not at its deepest point, but within the X20 CrMoV 12 1. The resulting crack growth for both cracks has been estimated and compared with a component test with artificial defects in a dissimilar weld undergoing similar loadings. (orig.)