Welding Distortion Minimization for an Aluminum Alloy Extruded Beam Structure Using a 2D Model

Abstract

Optimization of the weld sequence of a sub-assembly composed of thin walled aluminum alloy extruded beams is investigated and presented. The main factor considered is the quality of the assembly after welding, which is measured by the deformation behavior at pre-defined critical locations. The aluminum alloy extruded beam structure is simplified by a 2-D beam element model. Our methodology consists of applying pre-estimated angular shrinkages for each welding step thus eliminating use of a complex nonlinear transient analysis which would require consideration of thermo-mechanical interactions and plasticity. Two distortion modes (angular shrinkage and tilting shrinkage) are investigated and applied to model welding distortion. Different criteria for minimization of welding distortion have been investigated, such as overall deformation or weighted deformation with emphasis on some critical areas. A composite quality index is formulated, which is a weighted measure of critical deformation and the overall deformation. For simulating welding deformation and the role of sequences, some weld sequences were selected heuristically and they were simulated in ANSYS 5.2. Based on the quality index of these sequences, some were reproduced while mutating other portions of these sequences to find better sequences. Finally, deformation data for each node and weighted measures of deformation for considered sequences are presented, and final deformed shapes for different sequences, maximum principal stress, and bending moment across the beams are shown graphically.