Numerical Analysis And Application Of Tig Welding Deformation In Large Thin-walled Structures

The large thin-walled structure is widely used in aviation products due to light weight and high strength.During the research and manufacturing,the welding procedure is usually carried on in the connection of parts,However,the welding deformation and residual stress of large thin-walled structure with low rigidity lead to the dimensional deviation,such as gap and unfitness,which has a serious impact on the geometrical accuracy of the tank.With the increase of the thin-walled structure size,the decrease of rigidity aggravates the influence of geometric nonlinearity on the warping deformation of the structure.Because of the thermo-mechanical coupling effect during welding process,the residual stress and deformation have the characteristics of highly non-Linear and gradient,which makes it difficult to calculate the deformation accurately and efficiently with analytical method.In this study,an effective and accurate method is proposed to predict the welding deformation with the consideration of the influence of material and geometrical nonlinearity.Based on the method,the numerical model is established to analyze the impact of structure shape and welding parameter on welding deformation and study the influence of structure size on the welding deformation of long-distance weld in thin-walled structures.The numerical calculation of welding deformation and geometrical evaluation on 3.35 m diameter rocket tank are carried on,which provides the theoretical basis and guidance for rocket tank manufacturing.The paper mainly includes the following several parts:(1)Precise prediction method for nonlinear welding deformation of large thin-walled structures.In this study,a three-dimensional applied stress method is proposed to establish an accurate numerical model on the prediction of welding deformation.The calculation is carried on by mapping the stress from local model to global model.With the consideration into the edge effect and the geometrical constraints by elastic zones on both sides,the weld is separated into several parts and the elastic zones are set into substructures.Based on the method and the deformation compatibility condition,the welding deformation is calculated,which provides a new and efficient way to predict the welding deformation of large walled structure accurately.(2)Influence of different parameters on TIG welding deformation of large thin-walled structures.According to the TIG welding procedure,the welding numerical model is established based on the three-dimensional applied stress method to study the effect of structure size on welding deformation of long weld.The impact of geometrical parameters and welding parameters on welding deformation are also investigated in this study.With the comparison between the welding deformation and the welding experiment.(3)Numerical calculation and geometrical evaluation on the welding deformation of assembled rocket tank.Three different types of numerical simulation models of weld structure are classified on the basis of the three-dimensional applied stress method according to the structure of rocket tank.The numerical calculation of welding deformation of all the parts and the whole tank is conducted.With the result,the analysis of welding deformation and residual stress is carried on,which provides the theoretical basis and guidance for rocket manufacturing.