【作者】 刘明；

【导师】 雷斌隆；

【作者基本信息】 西南交通大学 ， 材料加工工程， 2008， 硕士

【摘要】 如今,压力管道被广泛应用在石油化工、冶金、电力和医药等行业,同时也向大型化、多样化、复杂化发展。但是如何处理带有缺陷的压力管道,是目前工程界所关注的问题。压力钢管是一种大型压力管道,它是水电工程中输水建筑物的重要组成部分,它承受着较大的内水压力以及自身的重量和水重。压力钢管在生产和安装过程中,容易产生焊接缺陷。这些缺陷一般可以通过补焊等措施进行修复,但是较小的缺陷往往被忽略,而没有引起重视。在这些缺陷处,接头承载截面的几何尺寸发生了突变,产生了较强的应力集中,大大降低了接头的承载能力,对结构的静载强度、疲劳强度、脆性断裂以及抗应力腐蚀开裂都有重大的影响。因此,有必要对含焊接缺陷的压力钢管进行力学分析和安全评定。咬边和错边都是压力钢管生产和安装过程中常见的焊接缺陷,它们不能用常规的方法进行应力分析。因此,本论文根据某水电站实例,建立咬边和错边的三维有限元模型,并通过有限元分析软件ANSYS9.0,对在不同深度、不同锐度和不同位置条件下的咬边和错边进行了应力计算和分析,并讨论了不同条件下的咬边和错边对焊接接头应力集中的影响。本文还按照“压力容器缺陷评定规范”CVDA-84和“在用含缺陷压力容器安全评定”标准的规定,对纵缝不同深度咬边缺陷进行了安全评定,并给出了最大允许咬边深度,为咬边缺陷的返修和处理提供了可靠的力学依据,有极大的工程意义。更多还原

【Abstract】 Now, pressure piping is extensively used in petrochemical、metallurgy、electric power、medicine and so on. It is also developing with large-scale、diversification、and complication. But how to deal with the pressure pipings with defects is an important question in project area.Penstock is a kind of large pressure piping and is an important constitute of the building of power plant with water-transportation. It takes on bigger inner hydraulic pressure, the weight of itself and the watery weight. During the manufacture and fixing of penstock, it is easily to get welding defects and can be repaired by repair welding, but some shallow defects are usually neglected and don’t bring the recognition. Where the defects are, the size of received section could be changed. It results in bigger stress concentration, mostly reduces the bearing power of the welded joint and has an important impact on the static strength, the fatigue strength, the brittle fracture and the resistance to stress erode cracking. So it is necessary to finish the mechanics analysis and safety assessment of the penstocks with welding defects.Undercut and unfitness are common welding defects in the producing and fixing of penstocks. They are hard to be analyzed by using general methods. In this paper, based on the fact of hydroelectric power station, three-dimensional finite element models of undercut and unfitness are built. And the finite element software ANSYS 9.0 would be used to have a stress account and analysis on the undercut and unfitness with different depth, sharpness, and place. Secondly the affection of the defects in different conditions at the welded joint with stress concentration is discussed.By using CVDA-84 and "Safety assessment for in-service pressure vessels containing defects", this paper makes safety assessment about the penstocks with longitudinal undercut of different depth and works out the largest depth of undercut allowed. It has large significance for engineering.更多还原