平均化屈服准则及其在管道失效解析中的应用

Homogenization yield criterion and its application to pipeline failure analysis

摘要:

为得到准确可靠的管道爆破压力预测式,建立一个新的屈服准则进行管道塑性失效分析.为此,通过对变角度边心距求积分中值,建立一个随主应力分量线性变化的屈服准则,称为平均化屈服准则.该准则在π平面上的轨迹位于Mises圆内部,几何形状为一个等边非等角的十二边形.经与金属屈服的实验数据对比表明,该准则的Lode参数改写式为相互连接的分段直线,与实验数据吻合较好.在此基础上,利用该准则分析了管道受力时的应力、应变场,通过考虑材料的应变硬化效应,求出了管道爆破压力的解析解,并讨论了影响管道爆破压力的主要参数.通过与基于Tresca准则、Mises准则和TSS准则得到的管道爆破压力以及实验数据的对比表明:爆破压力预测值依赖于不同的屈服准则,并且基于本文准则的结果对实验值具有更高的逼近程度.此外,研究还发现管道几何尺寸和应变硬化指数是决定管道爆破压力的关键因素,管壁较厚或直径较小的管道可以承受更大的压力.本文结果对于设计和评估油气管道具有重要的意义.

Abstract:

To obtain an accurate and reliable prediction formula of burst pressure for pipelines, a new yield criterion was proposed to analyze the plastic failure of pipelines. By calculating the integral mean value of the apothem with variable angle, a yield criterion in the form of principal stress components was established, which is called homogenization yield criterion. The locus of the criterion on the π-plane is located in the interior of the Mises circle, and the geometric shape is a dodecagon with equal sides and unequal angles. By comparing with the experimental data of metal yielding, it showed that the rewritten formula by the Lode parameters for this criterion was a connected piecewise line, which was in good agreement with the experimental data. Based on this criterion, the stress and strain fields of a pipeline were analyzed, and an analytical solution of burst pressure for the pipeline was obtained in consideration of the strain-hardening effect of the material. Then, the main parameters that influence the burst pressure were discussed. The experimental data was compared with the burst pressure obtained based on the Tresca, Mises, and TSS yield criteria. Results showed that the prediction results of burst pressure were dependent on different yield criteria, and the results based on the proposed criterion had higher approximation to the experimental data. In addition, it was found that the geometry size of the pipeline and the strain-hardening exponent were the main factors that determine the burst pressure, and the pipeline with thicker wall or smaller diameter could bear more pressure. The results of this paper are significant to the design and evaluation of oil and gas pipelines.