Preload relaxation characteristics in composite bolted joints based on vibration fatigue test

Abstract

在强迫弯曲振动试验的基础上,建立了基于模态参数(共振频率和阻尼比)表征螺栓连接结构动态性能的分析方法和试验测试手段;通过施加不同初始预紧力和激振频率,探究碳纤维/环氧复合材料螺栓连接预紧力松弛的时变行为及其影响因素。结果表明:在10h振动疲劳过程中,螺栓初始预紧力越小,激振频率越大,连接件预紧力松弛程度越大;振动疲劳损伤会导致连接结构刚度衰退、阻尼增加;复合材料螺栓连接松弛受到材料黏弹性以及界面摩擦的共同影响,其中约50%的松弛是由复合材料黏弹性效应引起的。 The time-dependent behavior and the affecting factors of preload relaxation in carbon/epoxy composite bolted joint have been studied, through a forced bending vibration test included various initial preloads and excitation frequencies. Analysis method and test method, based on modal parameters (resonance frequency and damping ratio), were utilized to characterize the dynamic property of bolted joints. It is observed that the loss degree of preload will increase with decreasing initial preload, and it will increase with the exciting frequency increasing, over a period of 10 h vibration fatigue process. Vibration fatigue damages would result in stiffness decay and damping increase in structural jointsMergeCell the relaxation in composite bolted joints can be attributed to the conjunct mechanisms between viscoelastic behavior of materials and interface friction of which about 50% of relaxation is due to viscoelastic effect of composites.