シェルーソリッド混合解析を用いた船体構造部材に発生する表面き裂の三次元破壊力学解析に関する研究

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Applications to three-dimensional fracture mechanics analyses for surface cracks in welded joints of ship structure are presented. To evaluate mechanical behaviors of ship structures, shell finite elements are often used in finite element analyses (FEA). It is difficult to solve three-dimensional crack problems such as surface cracks using the shell elements because the plate thickness is assumed in the shell element formulation. A shell-solid mixed analysis is performed to evaluate stress intensity factors (SIFs) of three-dimensional surface cracks in ship structural members. The whole analysis region is modeled by triangle or quadrilateral shell elements, and the local region near the surface crack is modeled by tetrahedral solid elements. The shell model and the solid model are connected using RBE3 (Rigid Body Element 3) connection in MSC.Nastran. In addition, a semi-auto RBE3 connection technique is developed to enhance the shell-solid mixed analysis. VCCM (Virtual Crack Closure-integral Method) using tetrahedral finite elements are adopted to calculate the SIFs of the three-dimensional surface cracks. The SIFs calculation and the evaluation of the surface cracks in the welded joints of the ship structure are demonstrated.