基于应变的管道环焊缝失效评估图评价方法改进

Improvement of strain-based failure assessment diagram for pipeline girth weld

当管道名义应力超过材料屈服强度时,基于应变的失效评估图是评价管道内裂纹缺陷的重要手段,焊缝强度匹配是影响管道环焊缝断裂行为的重要参数,而传统的基于应变失效评估图方法未考虑焊缝强度匹配的影响。基于此,采用数值模拟方法建立了管道环焊缝外表面局部环向裂纹驱动力有限元模型,并基于BS 7910-2019《金属结构裂纹验收评定方法指南》的参考应变计算方法,探索了裂纹深度、裂纹长度、焊缝强度匹配系数、管材屈服强度对基于应变失效评估图评价管道环焊缝裂纹缺陷精度的影响,提出了将焊缝强度匹配纳入基于应变的失效评估图的改进方法与计算模型。改进后的基于应变失效评估图方法大大提高了其适用范围与评价精度,可为工程中开展管道环焊缝的适用性评估提供参考。(图14,表1,参24)

Strain-based failure assessment diagram(SBFAD) is an important method to assess the crack defects in pipeline when the nominal stress of pipeline exceeds the yield strength of the material. Weld strength matching is an important parameter afecting the fracture behavior of pipeline girth weld, while the traditional SBFAD method does not consider the influence of weld strength matching. In view of this, the finite element model of local circumferential crack driving force on the outer surface of pipeline girth weld was established by numerical simulation method. The efect of crack depth, crack length, weld strength matching coefficient and pipe yield strength on the assessment accuracy of SBFAD for the crack defect of pipeline girth weld was verified based on the reference strain calculation method proposed by Guide to methods for assessing the acceptability of flaws in metallic structures(BS 7910-2019). Then, the improved method and calculation model of reference strain were proposed, with the weld strength matching accurately incorporated into SBFAD. Generally, the improved SBFAD method significantly improves the application scope and assessment accuracy of theassessment method, and could provide reference for the applicability assessment of pipeline girth weld in engineering.(14 Figures, 1 Table, 24 References)