考虑非线性的法兰接头三维有限元分析

3D Finite element analysis of bolted flange jointconsidering gasket nonlinearity

法兰接头三维有限元模型包括法兰环、垫片、螺栓、连接壳体和焊缝，考虑了垫片材料受压时应力应变的非线性关系。模型为参数化模型，可以方便地更改各参数的数值，以便研究法兰接头的几何尺寸、材料性质和载荷大小对法兰接头强度与紧密性的影响。研究中考虑了两个加载过程：螺栓拧紧过程和施加内压过程。研究可以同时分析在螺栓拧紧过程和加压过程中法兰接头的整体性以及在加压过程中的法兰接头的密封性能。研究中，法兰环的弯曲、螺栓的弯曲和拉伸及垫片压应力的不均匀分布都可以模拟；结构尺寸、材料特性、螺栓拧紧程度和法兰接头的内压载荷对法兰接头的影响都可进行系统地分析。

A three dimensional finite element model of bolted flange joint has been built, which includes flange rings, gasket, bolts and connecting shell. The nonlinearity in compression stressstrain relationship of the gasket is considered in this study. The length of the connecting shell is taken to be long enough so that the shell boundary would not affect the results. The model is a parametrization model so that the geometry, material properties and loads can be easily changed to study their effects on the joint behavior. Two load steps are considered: the first load step is to simulate the bolt pretightening and the second to simulate the pressurizing. Because the analysis is nonlinear in nature, subloadsteps are used in each load step to ensure convergent results. In this study, two kinds of behavior of the bolted joint are of interest. One is the integrity of the joint during bolt pretightening and pressurizing stages; and the other is the sealing ability or leakage conditions of the joint during press urizing stage. In this study, the bending of the flange, the extension and bending of the bolts, and the nonuniform distribution of the gasket compression can all be simulated. The effects of joint geometry, material properties, bolt pretightening extent and internal pressure load on the joint behaviors are studied systematically. The study could give us better understanding on the mechanism of the bolted joint and a basis for optimization design of the bolted joint.