Creep rupture assessment is a significant issue in the field of high-temperature structural integrity. In this paper, the creep rupture assessment of 3D pressure pipelines with volumetric defects subjected to cyclic thermo-mechanical loadings is done using a direct numerical approach within the framework of stress compensation method (SCM). For calculation of creep rupture limit, an extended shakedown analysis scheme with yield strength correction is essentially performed, where the revised yield strength is determined as the minimum of the plastic yield strength and the creep rupture strength of material corresponding to a specified elevated temperature and rupture time. This direct numerical approach performs the creep rupture assessment by using the given creep rupture data of material rather than simulating the degenerative process of material based on creep damage constitutive equations under a specified loading history. The numerical approach is incorporated into commercial finite element software of Abaqus. Parametric studies on geometric dimensions of part-through slot affecting the creep rupture limit of 3D pressure pipelines with volumetric defects are conducted. Numerical results shown in this study indicate that the direct numerical approach accurately identifies the creep rupture limit boundary of the pressure pipeline, verified by the elastic-plastic cycle-by-cycle analysis. Failure mechanisms, such as local creep rupture, global creep rupture and global plastic rupture are detected under different loading combinations. These results give the helpful information for in-service integrity assessment of defective pressure pipelines at elevated temperature, and demonstrate the applicability and application prospect of the direct numerical approach in solving questions relevant to design or life assessment of other engineering structures.

蠕变断裂评估是高温结构完整性领域中的重要问题。在本文中，在应力补偿方法（SCM）框架内使用直接数值方法对具有周期性热机械载荷的具有体积缺陷的3D压力管道进行了蠕变断裂评估。为了计算蠕变断裂极限，基本上执行了具有屈服强度校正的扩展减振分析方案，其中将修正的屈服强度确定为与指定的高温和断裂相对应的材料的塑性屈服强度和蠕变断裂强度的最小值。时间。这种直接数值方法通过使用给定的材料蠕变断裂数据来执行蠕变断裂评估，而不是在指定的载荷历史下基于蠕变损伤本构方程来模拟材料的退化过程。数值方法被结合到Abaqus的商业有限元软件中。进行了部分贯通槽的几何尺寸的参数研究，该几何尺寸影响具有体积缺陷的3D压力管道的蠕变破裂极限。这项研究显示的数值结果表明，直接数值方法可以准确地识别压力管道的蠕变断裂极限边界，并通过逐周期的弹塑性分析进行了验证。失效机制，例如局部蠕变破裂，在不同的荷载组合下会检测到整体蠕变断裂和整体塑性断裂。这些结果为高温下有缺陷的压力管道在役完整性评估提供了有益的信息，并证明了直接数值方法在解决与其他工程结构的设计或寿命评估有关的问题中的适用性和应用前景。