输气管道裂纹动态扩展的数值模拟
Numerical Simulation of Crack Propagation in Gas Transmission Pipeline
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摘要: 作为输气管道止裂控制的重要依据, 必须要求其裂纹驱动力小于管道材料的断裂韧性, 在这种情况下进行裂纹动态扩展的数值模拟就显得非常重要。建立了输气管道裂纹动态扩展的有限元模型, 用弹塑性、大位移四边形的壳体单元离散管道。裂纹尖端后面的气体压力简化为指数衰减模式。裂纹的开裂采用节点力释放方法来模拟, 即根据裂纹扩展速度, 依次解除裂纹尖端的节点连接。裂纹驱动力用能量释放率G和裂纹尖端张开角CTOA两个断裂力学参量表示。分析了裂纹驱动力随内压的变化规律。提出的计算模型可为输气管道的止裂设计提供分析工具。Abstract: As an important criterion of arrest control of gas pipeline, drive force of a crack must be smaller than the fracture toughness of pipe material. In this case numerical simulation of dynamic propagation of a crack is vital. A finite element model about crack propagation is established. The pipe is discreted with elastic-plastic, large deformation and quadrilateral element. Gas pressure in tip of crack is simplified as an exponent decay model. Crack growth is simulated by node force release method, in which node constrain is set free in turn according crack propagation speed. Crack drive force is expressed by such fracture parameters as energy release rate and crack tip opening angle (CTOA). An illustrative example is given. Variation of crack drive force with pressure in pipe is analyzed. The model presented can be as an analytical tool for arrest design of gas pipeline.