Analysis of welding-induced residual stresses with the ADINA system

The welding-induced residual stresses analysis procedure (WIRSAP), based on the ADINA system of nonlinear finite element software, is described and the results of several WIRSAP analyses are discussed. Several two-dimensional (2D) axisymmetric WIRSAP analyses have been performed for pipe girth welds and for several multi-pass girth-like welds attaching small nozzles to large, thick-walled pressure vessels. The analytical methodology follows closely the basic techniques outlined by Rybicki et al., enhanced by the use of several specialized modeling techniques available in the ADINA system. For example, the element birth option is used to simulate the addition of weld metal, and the mixed pressure/displacement element formulation is used, in conjunction with the temperature-dependent bi-linear plasticity material model. Some of the welds analyzed involve backing rings, which were subsequently `machined off' via use of the element death option. The auto-time-stepping algorithm and the matrix update iteration scheme are used in the structural solutions. WIRSAP involves, in general, a pass-by-pass analysis of the uncoupled thermal and structural problems, but some analyses have been performed with an `enveloping' technique for grouping several weld passes together to study the feasibility of modeling multi-pass welds on a layer-by-layer basis. The analyses discussed here are all 2D, but most are large problems (>5000 nodes and >5000 four-noded elements, with a large number of solution steps). As such, they pose significant challenges to both software and hardware resources. Pre- and post-processing operations are performed on a network of Silicon Graphics workstations, and ADINA and ADINA-T are executed on a 64 MW, eight-processor CRAY Y/MP. Nominally 50 solution steps are utilized for each weld pass, and weld joints involving as many as 31 individual weld passes have been analyzed on a pass-by-pass basis. Results from several of these WIRSAP analyses are discussed, and the potential use of WIRSAP in a hypothetic attachment weld design optimization study is illustrated.