振动条件下螺纹预紧力衰退机理和影响因素研究

Study on the Mechanism and Influencing Factors of Preload Decline for Bolted Joints under Vibration

预紧力的保持性直接影响螺纹连接件的紧固功能,当前国内外的研究成果表明,在周期性横向振动的作用下螺纹连接件的预紧力很容易出现衰退,其中塑性变形和内外螺纹间的旋转松动是导致预紧力衰退的两个主要原因。通过多种有限元模型仿真对比,进一步揭示了横向振动条件下的预紧力衰退机理,发现应力再分布是导致预紧力衰退的另外一个重要原因。在此基础上,系统分析了在不同横向力、螺纹面摩擦因数、端面摩擦因数和材料特性的条件下,应力再分布、塑性变形以及旋转松动所导致的预紧力衰退过程的规律,最终获得了包含预紧力非线性快速衰退、预紧力线性衰退、以及疲劳断裂三个阶段的典型预紧力衰退曲线,并通过横向振动试验验证了该曲线的正确性。

:Preload directly affects the fastening performance of bolted joints.Existing research results have shown that preload may decline readily when bolted joints are subjected to cyclic transversal vibration.Plastic deformation and rotation loosening have been thought of as the two main causes resulting in the preload decline.The mechanism of preload decline under transversal vibration is revealed further by several sets of finite element simulations.It is found that the stress redistribution is another important cause leading to the preload decline.Then,the effects of stress redistribution,plastic deformation and rotation loosening on the preload decline are investigated.Various conditions of transversal force,friction coefficients and material properties are used in the simulations.Finally,a typical preload decline curve containing three stages is obtained.At last,transversal vibration experiments were performed to verify the reliability of the typical preload decline curve.