【作者】 邓彩艳；

【导师】 张玉凤；

【作者基本信息】 天津大学 ， 材料加工工程， 2006， 博士

【摘要】 压力容器及管道是我国国民经济的大动脉,是现代工业生产中必不可少的设备,其安全与否与人民生命财产息息相关。目前我国在役压力容器和管道的安全评定方法都是建立在断裂评定基础之上,而对于压力容器和管道等承压构件来说,经常出现结构在断裂之前先发生稳定泄漏的现象。本文主要针对焊接压力管道进行了系统、全面的“先漏后断”安全评定。应用英国BS7448试验标准,建立了管线用钢API 5L X56焊缝和HAZ的J-R阻力曲线和δ-R阻力曲线,并采用国内标准GB2038-91和国际标准BS7448对试验结果进行了分析对比。结果表明:国内标准GB2038-91对钝化线和排除线的规定存在一些不合理之处,具有很大的局限性,是造成JIC测试困难的主要原因。建议参考国外标准,根据实际情况进行修改。应用国内2005年开始实施的“在用含缺陷压力容器安全评定”标准和EPRI的研究成果,对形状参量的应用范围进行外推研究裂纹扩展的稳定性;并依据SINTAP和BS7910标准中高级评定方法,对环向内表面裂纹的延性撕裂稳定性和塑性失稳稳定性进行分析,从而判断管道的失效模式。根据SINTAP标准考虑鼓胀因子等因素,推导出线弹性裂纹张开面积计算公式,并与其他线弹性计算方法进行对比。考虑到裂纹尖端附近的塑性变形对裂纹张开面积会产生一定的影响,分析了建立在弹塑性断裂力学基础上的一些解析方法如Irwin模型、Dugdale模型。利用流体有限元分析,计算实际管道焊缝处穿透裂纹的泄漏量。计算过程中分别讨论了实际流道表面粗糙度引起的流道摩擦损失、焊缝的余高、裂纹路径变化、变流道截面等因素对临界流量的影响。针对管道结构,研究了表面裂纹在循环载荷作用下的疲劳扩展过程,得到不同初始形状的表面裂纹在拉伸、弯曲载荷作用下扩展、穿透和形状演化的基本规律;并给出了表面裂纹穿透瞬间尺寸的确定方法以及得到穿透裂纹临界尺寸保守值的计算方法。更多还原

【Abstract】 Pressure vessel and piping, as artery of nation economy, are indispensable in modern industry. And their safeties closely relates to the lives and wealth of people. Nowadays, safety assessment methods for in-service pressure vessel and piping in China are all based on fracture model. However, steady fluid leak often occurs before break of the pressured structures such as pressure vessel and piping. The dissertation aims to make the leak-before-break safety assessment systemically and comprehensively.In the dissertation, J-Resistance andδ- Resistance curves of welded metal and HAZ are established according to British Standard, BS7448. And the comparison between the two standards, National standard GB2038-91 and BS 7448, is discussed. The result indicates that there are some unreasonable aspects and limitation in the guideline of blunt line and exclude lines of GB2038-91, which leads to it difficult to measure JIC parameter. So it is suggested that GB2038-91 is amend by reference to international standard and practical experience.Some geometry parameters are extrapolated for crack stability analysis in LBB by applying the standard of‘Safety Assessment of in-service Pressure Vessel with flows’implemented in 2005 and production of Electric Power Research Institute, EPRI. Based on the advanced levels of SINTAP and BS7910, tearing instability stress and plastic collapse stress are analyzed for circumferential through-wall crack of pipe to estimate the failure mode of pipe.Line elastic COA formula, which considers an amplification factor due to bulging, is deduced according to SINTAP. And its output is also compared with other known methods. Considering the effects that the plasticity at crack tip is to increase the opening of the crack and then the opening areas are greater than those in liner elastic case, available analytic methods such as Irwin and Dugdale models are investigated in the dissertation.Flow leakage rate through crack in welded pipe is computed by modern fluid finite element analysis technique. The effects of some factors, such as friction loss, crack path loss, excess weld metal and variable cross-section on leakage rate are taken into consideration during the computation.更多还原