Prediction And Control Of Aluminum Thin-Wall Column Welding Deformation

The structure of thin-walled aluminum alloy cylinder is the representative of components widely used in aircraft, military weapons, etc., and as a carrier, cylinder itself has a variety of weld, including the longitudinal weld, circumferential weld, flange weld. The welding deformation makes a direct impact on the quality of follow-up processing and service life of the product. Therefore, prediction and control of the welding deformation seems particularly important. Traditional practices such as orthogonal experiment,which determine the appropriate welding technology and welding fixture through lots of experiments to achieve the purpose of controlling welding deformation, is costly.This paper studies on prediction and control of welding deformation of thin-walled aluminum alloy cylinder structure in depth, while it is an important part of General Armament Department Eleventh Five-Year Department pre-research project "a new type of aluminum alloy structure spacecraft robot welding technology", which is a joint commitment to Intelligentized Robotic Welding Technology Laboratory of Shanghai Jiaotong University Welding Engineering Institute and Shanghai Spaceflight Precision Machinery Research Institute.This article analyzes heat source form and heat load method of longitudinal weld, circumferential weld, and flange weld on thin-walled cylinder from the perspective of finite element method. In the simulation process, starting welding with seconds of staying, smooth welding, arc out, natural cooling after welding is achieved. A general method of designing fixture with finite element method is proposed, which is firstly replacing actual fixture by displacement constraints to carry out the simulation calculation in the draft design stage; sencondly determining the best fixture program and major components of fixture according to drafts; thirdly completing fixture's three-dimensional modeling and mapping with software Pro/E and Auto CAD;forthly establishing thermal plastic finite element model to simulate welding deformation under the upper fixture. If the prediction result is passed, the fixture design is completed, or not, modifying the fixture program till it's ok.In the process of simulating, discreting units, connecting gap shell elements, simplificteing model simplification etc., is skillfully solved. The best staring welding spot is found through choosing different starting spots to carry out simulation and welding path is also analyzed.Finally, self-build measurement system with robots, laser displacement sensor, collector and positioner is used for roundness measurement. Calculation errors are analyzed in order to prove that the finite element method, conducting fixture design and process optimization to predicte and control welding deformation, is feasible.