外力作用下管道内表面缺陷处裂纹扩展研究

为提高油气管道安全风险评估的准确性,以含内表面缺陷管道为研究对象,利用ABAQUS软件线弹性及弹塑性分析不同尺寸缺陷对裂纹萌生特征的影响;采用扩展有限元法,建立管道3点弯曲模型与全尺寸静载物理试验,并非线性拟合裂纹扩展尺寸,研究内表面缺陷处裂纹扩展情况。研究结果表明:内表面缺陷中心处极易萌生裂纹,随着缺陷尺寸的增大,裂纹萌生所需外力在缺陷相对长度为0.08、相对深度为0.4时的增长趋势变化较大,且缺陷深度对裂纹萌生的影响更大;对比数值模拟与全尺寸物理试验,发现在小于70 mm位移载荷或147.25 kN外力下裂纹尺寸快速扩展,之后呈变缓的趋势;非线性拟合裂纹尺寸,得到较为准确的裂纹扩展尺寸的预测结果。

Research on crack propagation of pipeline inner surface defect under external force

In order to improve accuracy of pipeline safety risk assessment,taking pipeline with internal surface defects as research object,influence of different size defects on crack initiation law was analyzed by using ABAQUS software linear elastic and elastic-plastic,3-point bending model of pipeline and full-scale static load physical test were established by using extended finite element method,and nonlinear fitting of crack growth size was used to study crack propagation at the inner surface defects. The results show that crack initiation is very easy at the center of inner surface defect. As the size of the defect increases,the external force required for crack initiation changes greatly when the relative length of the defect is 0. 08 and the relative depth is 0. 4,and influence of defect depth on crack initiation is greater. Comparison between numerical simulation and full-scale physical test shows that crack size rapidly expands under displacement load of less than 70 mm or external force of 147. 25 kN,and then nonlinear fitting of crack size can obtain more accurate prediction results of crack growth size.