Efficient Simulation of Welding Distortion in Large Structures and Its Reduction by Jig Constraints
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JMEPEG DOI: 10.1007/s11665-017-3000-4
Efficient Simulation of Welding Distortion in Large Structures and Its Reduction by Jig Constraints Ninshu Ma and Hui Huang (Submitted November 20, 2016; in revised form August 15, 2017) Two large construction machinery structures were welded separately with and without jig constraints. The welding distortion of the entire structure was measured by a 3D coordinate measuring system and simulated by elastic FEM using the inherent deformation method. To obtain an accurate inherent deformation, a thermal elastoplastic FE analysis of simple one-side fillet joints with and without jig constraints was performed. Efficient simulation of welding distortion in large structures was accomplished by applying inherent deformation in a localized region, and the effect of jig constraint on the reduction of welding distortion was clarified. The computation of inherent deformation, the weld zone definition and the conversion of inherent deformation into inherent strain were automated. Measured and computed welding distortions in large structures had a good correspondence with respect to both tendency and magnitude. Further investigation of jig configuration was performed for enhanced reduction of welding distortion. Alternative controlling techniques for common welded structures were also addressed. Keywords
efficient simulation, inherent deformation, jig constraints, large structures, welding distortion
1. Introduction Welding distortion is usually inevitable in welded structures, such as ships, bridges and construction machines, because of nonuniform shrinkage under thermal cycles. The distribution of welding distortion is hard to predict and control in complex structures with multiple stiffeners. The precision of geometrical dimensions cannot be guaranteed if excessive welding distortion occurs. There have been many fundamental studies on the reduction and prevention of welding distortion. From the viewpoint of minimizing heat input, welding distortion can be reduced by substituting the arc welding with laser or electronbeam welding (Ref 1). Currently, some of the large panel structures in shipbuilding are joined by arc-laser hybrid welding (Ref 2). The welding deformation can also be reduced by optimization of groove type and welding sequences (Ref 3). Despite these approaches, arc welding is still the main process for welding large structures. Therefore, external constraints or additional cooling techniques are usually employed to control the welding distortion in practical engineering. There are several difficulties in controlling the welding distortion in large structures associated with the welding process. First, the components to be joined have geometric errors; hence, a gap and misalignment exist (Ref 4). The effect of the gap on the welding distortion was examined by Deng and Murakawa (Ref 5). Second, the constraint is more complex in Ninshu Ma, Joining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan; and JSOL Corporation, 2-2-4 Tosaori, Ni
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