【作者】 张波；

【导师】 陈冰冰； 陈忠友；

【作者基本信息】 浙江工业大学 ， 动力工程（专业学位）， 2018， 硕士

【摘要】 金属透镜垫密封有效接触面积小,可以获得较高的接触应力,容易实现高压密封,因此被广泛的使用在高压管道连接中。然而在使用过程中除了承受介质内压和螺栓载荷作用外,还经常有来自管路系统中由热变形产生的外弯矩载荷的作用,造成螺栓管道法兰连接结构的泄露失效。本文在考虑内压和螺栓预紧载荷的基础上,研究了外弯矩作用下的螺栓法兰连接结构力学行为,建立了外弯矩作用下金属透镜垫理论分析的简化方法,为研究外弯矩作用下透镜垫螺栓法兰连接结构的密封性能提供了参考。本文的主要工作和研究结果如下:对外弯矩通过两相邻螺栓对称面的透镜垫法兰连接结构进行了实验研究,利用压降法测量在不同预紧力下,随外弯矩变化共计14种工况下金属透镜垫法兰连接结构泄漏率变化情况。通过在各个螺栓光杆部分黏贴2个180°间隔的应变计的方法测量了螺栓在预紧、加压和外弯矩全过程应变变化情况;同时建立了与试验相对应的三维有限元模型,对各个工况下金属透镜垫法兰连接结构进行了数值模拟计算;最后通过理论推导建立了外弯矩作用下金属透镜垫理论分析的简化方法。对比分析实验、有限元模拟计算和理论推导下各个工况的螺栓载荷变化,结果基本吻合。由外弯矩作用下金属透镜垫法兰连接结构的密封性能实验可知,金属透镜垫周向上压痕呈现明显分布不均现象,在“受压”侧压痕宽度较宽,在“受拉”侧压痕宽度较窄;泄漏率L_R与外弯矩M的关系为非线性关系,呈现两段式变化趋势,当预紧力大小分别为230kN或240kN、内压为2.0MPa,对于DN50的金属透镜垫螺栓法兰连接结构,当M<3.5kN·m时,泄漏率随外弯矩的增大呈现出平稳上升的趋势,当外弯矩M>3.5kN·m时,泄露率增长的速率明显增大。考察了外弯矩对垫片接触应力分布的影响,结果表明:外弯矩作用前垫片接触应力在圆周方向均匀分布在金属透镜垫的一个狭长带上,随着外弯矩的增大,金属透镜垫垫片接触应力在圆周上呈现分布不均匀变化,而且这种分布不均的趋势随着外弯矩的增大越来越显著。透镜垫接触应力在接触宽度中心区域最大,沿两侧逐渐减小,直至为零,在密封接触区域垫片接触应力沿径向分布并不均匀,透镜垫外径方向接触应力分布区域大于内径方向接触应力分布区域。更多还原

【Abstract】 The metal lens pad seal has a small effective contact area,can obtain a high contact stress,and is easy to realize a high-pressure seal.Therefore,the metal lens pad is widely used in a high-pressure pipe connection.However,in use,not only the internal pressure of the medium and the load of the bolt are used,but also the external bending moment load generated by the thermal deformation in the pipeline system often causes the leakage failure of the bolted pipe flange connection structure.In this paper,based on the consideration of internal pressure and preload of bolts,the mechanical behavior of bolted flange joints under external bending moments is studied.A simplified method for the theoretical analysis of metal lens pads under external bending moments is established.The sealing performance of the lens flange bolt connection structure under the action of the moment provides a reference.The main work and research results of this paper are as follows:External bending moments are experimentally studied through the lens mat flange connection structure of two adjacent bolt symmetry planes.The pressure drop method is used to measure the total of 14 kinds of metal lens pad flanges under different preloads with the change of external bending moment.Connection structure leakage rate changes.The strain changes in the whole process of preloading,pressurizing and external bending moments of the bolts were measured by affixing two strain gauges at intervals of 180° to each bolt polished rod section.At the same time,a three-dimensional finite element model corresponding to the experiment was established.The numerical simulation calculation of the flange connection structure of the metal lens pad under various working conditions was performed.Finally,a simplified method for the theoretical analysis of the metal lens pad under the external bending moment was established through theoretical derivation.Comparative analysis of the experiment,finite element simulation and theoretical derivation under different conditions of the bolt load changes,the results are basically consistent.According to the experimental results of the sealing performance of the metal lens pad flange connection structure under the action of external bending moments,it can be seen that the circumferential indentation of the metal lens pad shows an obvious phenomenon of uneven distribution,and the width of the indentation at the “pressurized” side is wider and “pulled”.The lateral indentation width is narrow;the relationship between the leakage rate LR and the external bending moment M is nonlinear,showing a two-stage change trend,when the pre-tightening force is 230 kN or 240 kN,the internal pressure is 2.0MPa,and the metal for DN50 Lens gasket bolt flange connection structure,when M <3.5kN · m,the leakage rate with the increase of the external bending moment showing a steady increase in the trend,when the external bending moment M> 3.5kN · m,the leakage rate of growth rate Obviously increased.The influence of the external bending moment on the contact stress distribution of the gasket was investigated.The results showed that the contact stress of the gasket before the external bending moment was evenly distributed in the circumferential direction of a narrow strip of the metal lens pad,with the increase of the external bending moment,The contact stress of the metal lens pad gasket shows a non-uniform distribution on the circumference,and the tendency of this uneven distribution becomes more and more significant with the increase of the external bending moment.The contact stress of the lens pad is the largest in the central area of the contact width and gradually decreases along both sides until it reaches zero.The contact stress of the spacer in the sealing contact area is not uniformly distributed in the radial direction,and the contact stress distribution area in the outer diameter direction of the lens pad is larger than the inner diameter direction.Contact stress distribution area.更多还原