Finite Element Analysis Of Welding Conditions On Crack Characteristics

Welding process will bring about complex three-dimensional residual stress and micro-defects inevitably in the weld and heat affected zone.As time goes on, the microscopic defects in the weldments will germinate and turn to be cracks, and even lead to sudden catastrophic accident. Welded structures are widely used in bridgework, aerospace, shipbuilding, automotive and nuclear power, and closely related to our life. Study of the method to inhibit crack propagation has certain theory significance and the practical application value.This paper discussed the effects of different welding conditions and welding residual stress field on J integral depending on the welding technology, heat transfer theory, fracture mechanics, computational mechanics and other multidisciplinary theories and using the finite element method as a tool. The main research work included:(1) Established birth and death elements welding models of the standard compact tension specimen with different welding conditions, and calculated temperature field; (2)Established coupled thermal-stress model, and calculated welding residual stress with different temperature field; (3)Established the three-dimensional finite element fracture mechanics model of standard compact tension specimen, calculated the stress field near the crack tip and the J integral under only work load and combined effects of the residual stress and work load; (4)Compared effects of different welding residual stress field on J-integral.In this paper, the relationship between the welding parameters and J-integral has been established eventually. It found that the welding conditions as welding direction, welding speed, welding position, weldment’s thickness and cooling time would lead to a redistribution of welding residual stress field, and have a favorable or unfavorable impacts on fracture properties.