回転自由度を有する四面体要素の破壊力学パラメータ算出法（一般化四面体要素用の仮想き裂閉口積分法）

摘要

This paper presents a virtual crack closure-integral method (VCCM) for a generalized four-node tetrahedral finite element that has drilling nodal degrees of freedoms (DOFs). The generalized tetrahedral finite element has superior accuracy over the liner tetrahedral element. VCCM computes the energy release rate and the stress intensity factor at the crack front. VCCM computes the fracture mechanics parameters accurately only from the nodal reaction forces and displacements. Furthermore, in mixed mode problem, it is easy to split energy release rate into each mode of crack deformation. In this paper, a VCCM formulation for the generalized tetrahedral finite element is developed for the case of mode I crack deformation. The contributions of nodal drilling DOFs on the computation of energy release rate are described in detail. Similar discussions can be extended to mixed mode problems. Finally, some numerical examples are presented and discussions on the accuracy of proposed VCCM are given.%破壊力学はエネルギープラント，航空機や土木構造rn物などの構造健全性評価や強度設計に広く用いられてrnいる．有限要素法による破壊力学解析では，き裂のrn応力特異性を表現するために，その近傍で非常に細かrnい有限要素分割を行うことが必要である．き裂近傍とrnその他の部分において有限要素サイズが大きく異なるrnので，解析モデル生成に多大な労力を要する．さらに，rn疲労や応力腐食割れの問題では，き裂進展に伴い有限rn要素法解析モデルの更新を数十～数百回繰り返す必要rnがあり，解析者の労力，コンピュータによる計算時間rnともに膨大になる．