Thin-walled welded shipbuilding components are often the places of the initial cracks in exploitation. Therefore, it is recommended to determine the critical size of crack which causes plastic collapse of component. In this paper R6 procedure has been used to find critical depth of crack assuming that the crack is through whole section of component. Six various crack depths were analysed. Crack has been assumed perpendicular to the vector of principal stress σ1 at the location of its maximum. The stress which lead to yielding of remained ligament and corresponding stress intensity factor value were calculated by using of software based on finite element method. Fracture toughness for the material of the component has been estimated from the Charpy toughness. Finally, all six pairs of the loading path points (Kr, Lr) were lying in the safe area within FAD diagram, so the fifth order polynomial should be constructed in order to find critical point of intersection with the material curve in FAD diagram. Obtained results shown excellent fracture behaviour of the welded component, due to the fact that very deep cracks still will not cause the plastic collapse. However, this could be rapidly changed if the component is subjected to the fatigue. |