Constrained dents normally cause serious plastification on the pipe under internal pressure due to the restraint of the indenter. Therefore, in this work, the strain response of the API 5 L X80 (referred to as X80 in the remainder part) steel pipeline containing a constrained dent was investigated. Firstly, the formation process of the constrained dented pipeline was numerically simulated by establishing a 3D finite element (FE) model. The model was then verified against the test results of other researchers. The validated model was employed to investigate the equivalent plastic strain distributions of the constrained dent created during the pipe construction and pipe operation stages. Finally, an extensive parametric study was conducted to examine the effects of the internal pressure, dent depth, diameter-to-thickness ratio, indenter size and shape on the strain response of the constrained dented pipe in detail. The results show that the maximum equivalent strain of shallow dents locates at the pipe inner wall at the dent center. As the dent depth increases, the maximum strain position deviates from the dent center and moves outwards along the pipe circumferential direction. Compared with the constrained dent formed during the pipe construction period, the maximum equivalent strain of the in-service constrained dented pipelines is larger under the identical dent depth. The maximum strain increases significantly as increasing the dent depth and internal pressure. It is noted that the wall thickness has a greater influence on the equivalent plastic strain distributions of the constrained dented pipe than that of the pipe diameter. The equivalent plastic strain caused by a small indenter is more serious than the large one due to the high strain concentration. It is noteworthy that circumferential dent (dent length is less than dent width) can be considered as the most severe form of dent defects on the pipe in comparison to the axial dent (dent length is greater than dent width) and dome dent (dent length is approximately equal to dent width).

由于压头的限制，受限制的凹痕通常会在内压下导致管道严重塑化。因此，在这项工作中，研究了包含约束凹痕的 API 5 L X80（其余部分称为 X80）钢管的应变响应。首先，通过建立3D有限元（FE）模型，对约束凹陷管道的形成过程进行数值模拟。然后根据其他研究人员的测试结果验证该模型。验证模型用于研究管道施工和管道操作阶段产生的受约束凹痕的等效塑性应变分布。最后，进行了广泛的参数研究，以检查内部压力、凹痕深度、直径与厚度比的影响，压头尺寸和形状对受约束凹陷管的应变响应的详细信息。结果表明，浅凹痕的最大等效应变位于凹痕中心的管道内壁处。随着凹痕深度的增加，最大应变位置偏离凹痕中心并沿管周方向向外移动。与管道施工期形成的约束压痕相比，在相同压痕深度下，在役约束压痕管道的最大等效应变更大。随着凹痕深度和内部压力的增加，最大应变显着增加。值得注意的是，与管径相比，壁厚对约束凹陷管的等效塑性应变分布的影响更大。由于应变集中，小压头引起的等效塑性应变比大压头更严重。值得注意的是，与轴向凹痕（凹痕长度大于凹痕宽度）和圆顶凹痕（凹痕长度）相比，圆周凹痕（凹痕长度小于凹痕宽度）可以被认为是管道上凹痕缺陷的最严重形式大约等于凹痕宽度）。