Abstract:

Aiming at the problem of seal failure of the metal O-ring with internal holes of a pressure vessel flange under high pressure conditions, which was caused by excessive deformation of the O-ring due to unreasonable design of the flange structure, a three-dimensional cyclic nonlinear elastoplastic model was established to analyze the effects of flange side wall gap and compression ratio on the circumferential distribution of contact stress and O-ring deformation. The leakage rate of O-ring under different flange side wall gap and compression ratio was tested, the deformation characteristics of O-ring were analyzed, and the deformation failure mechanism of O-ring under high pressure and big side wall gap was discussed. The research results showed that the established finite element model can accurately simulate the mechanical behavior and deformation of O-ring, and the calculated curve had a good agreement with the experimental curve. The contact stress of O-ring was more sensitive to the flange side wall gap, reducing the flange side wall gap and increasing the compression ratio can improve the reliability of O-ring seal. O-ring was prone to necking deformation under high pressure conditions, resulting in circumferential discontinuity of contact stress and leakage. Controlling the preload clearance of O-ring and playing the restraint effect of flange side wall can improve this kind of deformation. The research results can provide a reference for the flange structure design of high pressure metal O-ring sealing with internal holes.

Key words: flange, metal O-ring with internal holes, high pressure, side wall gap, compression ratio, deformation failure

摘要：

针对某压力容器法兰内开孔金属O形环在高压工况下，因法兰结构设计不合理导致O形环过度变形而引起的密封失效问题，建立了三维周期非线性弹塑性模型，分析了法兰侧壁间隙和压缩率对O形环接触应力周向分布和环体变形的影响。试验测试了工作压力下的O形环在不同法兰侧壁间隙和压缩率时的泄漏率，分析了O形环的变形特征，探讨了O形环在高压大侧壁间隙下的变形失效原因。结果表明：建立的有限元模型能准确地模拟O形环的力学行为和变形，计算曲线与试验曲线吻合程度良好；O形环的接触应力对法兰侧壁间隙更敏感，减小法兰侧壁间隙和增加压缩率都能提高O形环密封的可靠性；O形环在高压工况下容易产生颈缩变形，造成接触应力在周向不连续导致泄漏，控制O形环的预紧间隙并发挥法兰侧壁的约束作用能够改善此类变形。研究结果可为高压内开孔金属O形环密封的法兰结构设计提供参考。

关键词: 法兰, 内开孔金属O形环, 高压, 侧壁间隙, 压缩率, 变形失效