| Budget Amount *help |
¥3,380,000 (Direct Cost: ¥2,600,000、Indirect Cost: ¥780,000)
Fiscal Year 2011: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000)
Fiscal Year 2010: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000)
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| Research Abstract |
Welding is one of the essential processes for assembling steel structures such as ships and bridges. However, it is impossible to avoid residual stress and distortion. To prevent or minimize these problems, quantitative prediction and effective control of welding residual stress and deformation are necessary.
To compute welding deformation, two methods are often used. One is the thermal elastic plastic finite element method(FEM) and the other is elastic FEM using inherent deformation. Thermal elastic plastic FEM is effective for accurate evaluation of welding deformation but requires large computational time. Elastic FEM using inherent deformation requires very short computational time, but the inherent deformations of all welding joints composing the structure must be known beforehand. However, these two methods can be combined to take advantage of both. The inherent deformations of welding joints are computed using thermal elastic plastic FEM and stored in a database, which is used to compute the welding deformations of large structures using elastic FEM.
Nevertheless, these methods for welding analysis can require very long computational time and memory, even if the model is a simple weld joint. Therefore, for faster calculations and analyzing large structures, we developed the iterative substructure method(ISM) and idealized explicit FEM for welding simulation. In this study, a thermal elastic plastic analysis using ISM is applied to a weld joint model. The plastic strain distribution obtained by ISM is used for inherent strain analysis using idealized explicit FEM to analyze a block model of a large ship. The block model is 8.5 m x 8.5 m x 4.4 m with more than 300 welding lines. The simulated results agree well with the measured distortion. In addition, the influence of the welding direction on the welding deformation of the targeted ship block is investigated.
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