The Mechanism Of Micro-vibration Transmission In Bolted Joints

Micro-vibration on spacecraft refers to a slight vibration with amplitude lower than 0.1g caused by normal operation of actuators and other functional assemblies.Micro-vibration will seriously affect attitude pointing accuracy and stability of the spacecraft during normal movement,such as to affect the normal performance of certain high-precision equipments.As an important connection method in spacecraft,bolted joint has an important influence on the micro-vibration transmission of the spacecraft.Therefore,the mechanism of microvibration transmission in bolted joint was studied.Firstly,the paper summarizes the theoretical model of contact surfaces,including Greenwood-Williamson model,Chang-Etsion-Bogy model and Krolikowski-Szczepek model.Secondly,this paper describes the micro-vibration test of bolted joint.Specimen's natural frequency and damping ratio were measured with sinusoidal sweep test method or FRF method.Specimens were divided into control and experimental groups.Thirdly,according to the contact surface topography parameters of the specimens,as well as the theoretical contacts models,the contact stiffness of the bolted surfaces can be obtained.Finally,we establish finite element models for the specimen by ABAQUS.In order to fully reflect the impact of the bolted surfaces on the overall structure,we add a thin layer between the contact surfaces of the two parts.We set material parameters of the thin layer according to the contact stiffness of the specimens,then the natural frequencies of the models are obtained by finite element calculations.The applicability of theoretical models are verified by comparison between natural frequencies obtained by simulation and by experiments.The results reveal that the gap between simulation and experimental results is more than 10%,which indicates that neither GW model theory nor the CEB model theory can precisely describe the transfer rules of bolted joints.