Fracture criterion for XFEM to predict burst pressure of dents with cracks in pipeline steels

XFEM 断裂判据预测管线钢裂纹凹痕爆破压力

• 批准号: 536002-2018
• 负责人: Adeeb, Samer
• 金额: $ 4.3万
• 依托单位: University of Alberta
• 依托单位国家: 加拿大
• 项目类别: Collaborative Research and Development Grants
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=699062
• 关键词: Fracture; criterion; XFEM; predict; burst

Cracks in pipelines constitute one of their major integrity threats as their existence can lead to loss of containment capability. When cracks exist, operators need to ensure that the associated burst pressure is high enough compared to the operating pressure of the pipeline. Currently, there are several analytical methods for predicting the burst pressure of cracked pipelines. Cracks, however, are often associated with other integrity threats such as corrosion or dents for which no agreed upon assessment method exists. In order to predict the behaviour of a pipeline in these situations operators either rely on experience making the integrity decisions inconsistent, or on numerical tools. Current numerical tools, however, are extremely time rendering their application impractical. The more recently developed eXtended Finite Element analysis Method (XFEM) provides a more robust approach in which crack propagation can be modelled efficiently. This research project aims at developing calibrated XFEM based fracture strain criteria for predicting crack propagation in pipelines. The developed criteria will take into consideration the constraints at the crack-tip specific to various loading conditions and applicable to different grades of pipeline steel. The criteria will provide significant numerical convenience with accuracy in predicting the brittle or ductile fracture related to the crack-tip constraints, independent of the specimen geometry, pre-cracking size, and loading conditions. The developed criterion will be validated and applied for the assessment of dent-crack flaws in thin walled pipelines. Different parameters of the dent-crack flaw, namely: crack length, crack depth, dent length, dent depth, crack location in the dent, and operating pressure during dent formation will be varied to understand their effect on the burst pressure. Comparison of predicted burst pressures for different scenarios will be done to identify critical flaw scenarios to develop a guide for dent-crack flaw assessment. This research will provide assessment criteria for dents associated with cracks, in addition to providing an accurate tool for evaluating the safe dig pressure for pipelines with crack like features.

管道裂缝是管道完整性的主要威胁之一，因为裂缝的存在会导致管道失去控制能力。当裂缝存在时，操作人员需要确保相关的破裂压力相对于管道的运行压力足够高。目前，有几种预测管道破裂压力的分析方法。然而，裂缝通常与其他完整性威胁有关，例如腐蚀或凹痕，而目前尚无统一的评估方法。在这种情况下，为了预测管道的行为，作业者要么依靠经验做出不一致的完整性决策，要么依靠数值工具。然而，目前的数值工具非常耗时，使得它们的应用不切实际。最近发展的扩展有限元分析方法（XFEM）提供了一种更稳健的方法，可以有效地模拟裂纹扩展。该研究项目旨在开发基于XFEM的断裂应变准则，用于预测管道中的裂纹扩展。所制定的准则将考虑裂纹尖端的约束，具体到各种加载条件下，适用于不同等级的管道钢。该准则将为预测与裂纹尖端约束相关的脆性或延性断裂提供重要的数值便利，而不受试样几何形状、预裂尺寸和加载条件的影响。将对该准则进行验证，并应用于薄壁管道凹陷裂纹缺陷的评价。改变凹痕-裂纹缺陷的不同参数，即裂纹长度、裂纹深度、凹痕长度、凹痕深度、裂纹在凹痕中的位置以及凹痕形成过程中的操作压力，以了解它们对破裂压力的影响。对不同情况下的预测破裂压力进行比较，以确定关键缺陷情况，为凹痕裂纹缺陷评估提供指导。该研究将为裂纹相关凹痕的评估提供标准，并为具有裂纹特征的管道的安全开挖压力评估提供准确的工具。