Influence of weld material properties on fracture mechanics parameters in welds analysed by FEM calculations

Abstract

Results of elastic-plastic FEM calculations on various plane strain models of a CT-100 specimen with the fusion line of welds of different weld material properties in the ligament, and of single material with properties of the weld components (i.e. base and weld material and the heat affected zone) are compared and discussed in the light of fracture mechanics considerations. Regarding the cleavage fracture regime, considerably higher crack opening stresses are obtained in the welded specimen with the high strength weld material than in that with low strength weld material, as soon as small-scale yielding occurs. This means that in the cleavage fracture regime reduction of yield strength of the weld material will decrease the temperature at which cleavage fracture will still occur. Conservative evaluation of the crack opening stresses of the welded joint can be achieved by using the welding simulated material properties. The J- integral can be calculated from the load versus load-line displacement curve, for the models with a weld also. The crack opening profiles for both welds are asymmetric to the ligament. Larger displacements occur on the weld material side than on the side of the heat affected zone. The relationship between crack tip opening displacement and load-line displacement is independent of whether a single-material model or a model with a weld is considered. A linear dependence of the crack tip opening displacement on the J- integral also exists for the models with a weld. General yield occurs on the base-material side for the weld with high strength weld material, and symmetrically to the ligament for that with low strength weld material.