Development of Nonlinear Numerical Fracture Mechanics Based on Energy Release Rate

由于能量释放率具有明确的物理意义，因此本文选择能量释放率作为理解裂纹扩展问题的基本概念。在计算G值时，充分利用了考虑有限应变塑性的非线性有限元方法。此外，还发展了专门用于裂纹扩展分析的引入界面单元的有限元方法。将所提出的方法应用于下面列出的各种问题，并证明了其潜在的实用性。界面单元模拟裂纹扩展过程中新表面的形成。这样的界面单元沿裂纹扩展路径排列，以便分析裂纹的扩展，耗散的能量等于表面能量。(1)开发了轴对称弹性大变形问题的G值计算程序，三维有限应变弹塑性问题的G值计算程序，界面单元静态和动态裂纹扩展的程序(二维和三维有限应变弹塑性问题)，静态和动态裂纹扩展的界面单元程序，热裂纹的温度相关界面单元程序(2)研究了伴随屈曲的衬底上薄膜的脱粘问题。材料应变硬化特性对板间分层韧性的影响中心缺口钢板韧性裂纹稳定扩展惯性力对夏比冲击试验的影响外加应力对弹性板热裂纹动态扩展速度的影响试件几何形状和焊接条件对焊接热裂纹的影响

In the present research, the energy release rate is selected as a basic concept to understand the crack propagation problem since it has clear physical meaning. To compute the G-value, full advantage of nonlinear FEM, which considers finite strain plasticity, is taken. Also, FEM introducing an interface element is developed specially for the crack propagation analysis. The proposed method is applied to various problems listed below and its potential usefulness is demonstrated.The interface element models the formation of new surfaces during the crack propagation. Such interface elements are arranged along the crack propagation path so that the analysis of the crack propagating with dissipating the energy equal to the surface energy.(1) Developed programsProgram to compute G-value for axisymmetric elastic large deformation problem.Program to compute G-value for 3-dimensional finite-strain-elastic-plastic problemPrograms for static and dynamic crack propagation using interface element (2-dimensional and 3-dimensional finite-strain-elastic-plastic problems)Programs for static and dynamic crack propagation using interface elementProgram for hot cracking using temperature dependent interface element(2) Investigated problemsDebonding of thin film on substrate accompanying buckling.Effect of Strain Hardening Properties of Material on ToughnessAnalysis of Delamination between bonded platesSteady Ductile Crack Propagation in Center Notched Steel PlateInfluence of inertia force on Charpy Impact TestInfluence of Applied Stress on Speed of Dynamically Propagating Crack in Elastic PlateInfluence of Specimen Geometry and Welding Conditions of Hot Cracking in Weld