Development of parallelized analysis system of welding deformation for mega steel construction.

焊接是装配船舶、桥梁等钢结构的基本工艺之一。然而，不可能避免残余应力和变形。为了防止或减少这些问题，有必要对焊接残余应力和变形进行定量预测和有效控制。为了计算焊接变形，通常采用两种方法。一种是热弹塑性有限元法，另一种是利用固有变形的弹性有限元法。热弹塑性有限元法对焊接变形的精确计算是有效的，但计算时间较长。采用固有变形的弹性有限元法计算时间很短，但必须事先知道构成结构的所有焊接接头的固有变形。然而，这两种方法可以结合起来，以充分利用两者的优势。采用热弹塑性有限元法计算焊接接头的固有变形，并将其存储在数据库中，用于大型结构的弹性有限元计算。然而，这些焊接分析方法需要非常长的计算时间和内存，即使模型是一个简单的焊缝。因此，为了更快地计算和分析大型结构，我们开发了迭代子结构法（ISM）和理想的显式有限元法用于焊接模拟。在本研究中，应用ISM对焊接接头模型进行热弹塑性分析。利用ISM得到的塑性应变分布进行固有应变分析，采用理想显式有限元法对某大型船舶块体模型进行了分析。块模型尺寸为8.5 m x 8.5 m x 4.4 m，有300多条焊接线。模拟结果与实测畸变值吻合较好。此外，还研究了焊接方向对目标船块焊接变形的影响。

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.