西气东输管道裂纹的韧性减速机理研究

ON THE TOUGHNESS-INDUCED CRACK DECELERATION MECHANISM OF GAS PIPELINES TRANSMITTING GAS FROM THE WEST TO THE EAST

将动态断裂力学的基本原理、基本方法和止裂判据与壳体动力学的有限元方法相结合,形成了求解输气管道裂纹扩展问题的数值分析方法。对于高韧性钢,塑性功卸载引起的热耗散不可忽略。为此根据瞬态裂纹扩展条件下的整体能量平衡方程,在有限元中构造了求解瞬时速度的迭代算法。其中以材料的热耗散比率为主要构成的动态断裂韧性由实验测得,在计算中作为裂纹扩展速度的函数代入,形成韧性减速机理。为了给出计算需要的参数,推导了双试件DWTT法测定热耗散比率的公式。

A numerical analysis method is developed to solve the problem of crack propagation in gas pipelines. It is based on the fundamental theories, methods and arrested criteria in dynamic fracture mechanics as well as finite element method (FEM) in shell dynamics. For high toughness pipelines, the decrease of heat dissipation caused by plastic work unloading cannot be neglected. By referring to the energy balance equation under the condition of nonuniform crack propagation, an iterative method is constructed to solve the instant speed in FEM. The dynamic fracture toughness comprised mainly of the heat dissipation rate is obtained through experiments, and is used as the given function of crack speed, to replace the original steady propagation mode and form the toughness-induced deceleration mechanism. To determine the parameters required in calculation, the two-specimen DWTT method is deducted to determine the heat dissipation rate formula.