Study On The Fracture Performance And Engineering Treatment Of Welded Joints Containing Mixed Cracks

It is very difficult to assess the integrity of welded joints because it is a complexity structure with mechanical heterogeneity and geometrical uncontinuity. In this paper, at first, the fracture behaviors of welded joints containing the mixed mode â… +â…¡ crack is investigated, and then a new engineering treatment method to assess the integrity of welded structure containing defects is developed.By using elasto-plastic finite element method, the crack-tip field of welded joint, which containing the mixed mode â… +â…¡ crack, are analyzed. Based upon, the fracture parameter COD and its mixity angles of mismatched welded joints are calculated under the different loading level and angle. However, the influences factors of the loading angles and the mis-matched strength of welded joints are analyzed in detail also. The simulation results show that, the crack tip stress-strain field is asymmetrical, the upper shape of crack-tip is sharpened, and the lower shape of crack-tip is blunted obviously. For the more, the fracture parameter COD changes with the loading angle and strength matching parameters of welded joints. The effect of loading angle on the domination of mode I or II of the mixed mode â… +â…¡ crack is evident, and in the same time, the effect of strength matching is less than that of load angles. And the values of mixity angles depend on the loading angles and strength matching parameters respectively. As a result, the above factors must be considered during the calculation of the fracture parameter COD of welded joints containing the mixed mode â… +â…¡ cracks.In the end, based upon the engineering appliance, the fracture driving forces of the mismatched welded joints containing the mixed mode I + II crack are investigated, and the engineering treatment formulation of fracture parameter COD and its mixity angles are obtained by the curves simulation methods also. It can be seen that the engineering estimation solution is in good according to the results of finite element analysis.