Study On Welding Stress And Deformation Behavior Of Complicated Aluminum Alloy Structure

The aluminum alloy welding structure has been widely applied in many fields, such as ship engineering, aerospace engineering and so on. Since its large thermal expansion coefficient and small elastic modulus, great welding residual stress and deformation are difficult to avoid in the engineering. Thus, it is important to investigate the welding deformation and residual stress of aluminum alloy welding structure, which would has significant theory meaning and engineering value. The welding residual stress and deformation of 5A06 aluminum alloy reinforced circle and cylinder structure were analyzed by the thermal-elastic-plastic finite element method and inherent strain method respectively in this paper.Based on the infrared thermal imaging results, the temperature distribution of fillet welds during MIG discontinuous welding was researched. There are preheating effect from the welded seam and reheating effect from the sequent weld in the discontinuous welding. According to the distribution of heat flux density in the MIG welding pool and the character of discontinuous welding thermal cycle, a combined heat source model was developed which combining the double Gaussian heat distribution of arc and the double ellipsoidal distribution of over thermal droplet.Subsequently the transient parameters of double ellipsoidal heat source were confirmed with optimization design method. It is found that the combined heat source model produce more accurate numerical simulation result during the discontinuous welding.The transient distribution of welding stress was analyzed by indirect coupling method on the basis of the temperature field in the discontinuous welding, and the welding process of 5A06 aluminum alloy reinforced circle structure was simulated numerically. The angle deformation of the reinforced structure is decided by the temperature gradient of the structure thickness and the weld transverse contraction. The welding sequence and the weld length also have great effects on the welding residual stress and deformation.Based upon the thermal-elastic-plastic analysis of the discontinuous welding, the welding residual stress and deformation of 5A06 aluminum alloy reinforced cylinder structure was researched by inherent strain method, which also considering the effects of welding technology and weldment's size on the multi-passes V-type butt weld. The cylinder structure represented wave propagation, great stay was appeared where without reinforce plate, and it predicted the possible buckling deformation. Compared to the experimental results of the welding depression load and strain, the inherent strain method has high efficiency and can ensure definite precision in the numerical simulation of the complex welding structure. In the final, in order to ensure the structure's machining accuracy, the whole structure was annealinged after the discontinuous welding. The effects of annealing temperature, holding time, and cooling rate on the stress elimination were analyzed by finite element method, which constituting the corresponding annealing criterion and improving the manufacturing procedure. The research result could direct the welding production of the reinforced welding structure.