Crack propagation analysis of welded thin-walled joints using boundary element method

Tube-to-plate nodal joints under cyclic bending are widely used in the road transport and agricultural industry. The square hollow sections (SHS) used in these constructions are thin-walled and cold formed, and they have thic knesses of less than 4 mm. Some fatigue failures have been observed. The we ld undercut may affect the fatigue life of welded tubular joints especially for thin-walled sections. The undercut dimensions were measured using the silicon imprint technique. Modelling of thin-walled cruciform joints, as a simplification of welded tubular joints, is described in this paper to dete rmine the effect of weld undercut on fatigue propagation life. The Boundary Element Analysis System Software (BEASY) is used. The results of the effec t of weld toe undercut from this analysis are compared with results from pr evious research to determine the comparative reduction in fatigue life betw een thin-walled joints (T = 3 mm) and those made of thicker sections (T = 2 0 mm). The loss in fatigue strength of the thin-walled joints is found to b e relatively more than that for thicker walled joints. A 3D model of a tube to plate T-joint is also modelled using the boundary element software, BEA SY. The nodal joint consists of a square hollow section, 50 x 50 x 3 SHS, f illet welded to a 10-mm thick plate, and subjected to cyclic bending stress . Fatigue analyses are carried out and the results are compared with the on ly available S-N design curve.