Deformation Prediction And Control Of Multi-intensive Weld Component Using Laser Welding

The base and skin of a key structural components needed to be connected. Thesolder joint strength and deformation should be both taken into account. The jointstrength of soldering connections was not enough, so the method of laser weldingwas attempted. The joint strength of laser welding could be easily guaranteed, butmultiple and intensive weld inevitably leaded to greater welding deformation. Thebasic laws affecting welding deformation was researched in this paper. A series ofmeasures has been taken to reduce the welding deformation and the optimizedparameters was used to predict the welding deformation of actual welding structure.Firstly, the welding process and mechanical testing of laser welding for flat lapjoints was carried out. The results indicated that good joints with suitablepenetration and width could be obtained under the optimized parameters.Meanwhile, the shear strength of joints also meet the performance requirements.Secondly, finite element model was carried out to simulate the temperaturefield, residual stress distribution and deformation of the aluminum plate specimenswith the software of Solidworks, Hypermesh and Marc. Simulated weld cross andmetallographic was compared. Also, simulated thermal cycle curve and measuredthermal cycle curve was compared. Both of the compared results could verify theaccuracy of the heat source model and boundary conditions. The results showed thatsmaller and wider compressive stress zone exist on both sides of the weld, whilebigger and narrow tensile stress zone exist in the weld center. Welding deformationconsist of transverse shrinkage, longitudinal shrinkage and angular distortion.Besides, the results showed that the less cooling time after welding not onlydecreased the simulation time, but also reduced the welding deformation effectively.Thirdly, the complete structure was simplified to reduce simulation time. Thefactors affecting welding deformation was researched on the simplified model. Theresults was shown as follows. The welding deformation was significantly reducedbecause of the decrease of sink depth and skin thickness. The welding deformationwas slightly reduced with the sequence of welding from both sides toward themiddle. Displacement constraints simulating fixture was imposed on the model toreduce welding deformation. The deformation was rebound after the removal ofdisplacement constraints, but it was still smaller than that of no displacementconstraints. The eventually residual deformation was drastically reduced because ofpost weld heat treatment. The residual deformation was reduced further throughincreasing the thickness of base metal. Finally, a complete model structure was established using the optimizedparameters. So the residual stress distribution and welding deformation could bepredicted. The results showed that low longitudinal and transverse residual stressesexist near the weld. The flatness in the back was about0.1millimeter. So it meetsthe requirements of post weld technology.