Research On Dynamic Characteristics Of Cylindrical Shells With Bolted Joints

Cylindrical shells are widely used in aerospace,naval,civil engineering,and many other engineering fields due to its simple structure,good performance and light weight.In practical engineering applications,cylindrical shells are usually processed into segments and then assembled together by connecting structures.Bolted joints are widely used in the assembly structure of cylindrical shells because they have many advantages such as simple structure,easy processing,easy disassembly,high bearing capacity,and good reliability.Bolted joints change the continuity of the assembly structure,and there are many complicated nonlinear phenomena such as friction between the connection interfaces,nonlinear connection stiffness and so on,so it will affect the dynamic characteristics of the cylindrical shell with bolted joints.Therefore,it is necessary to carry out modeling and dynamic characteristics research of cylindrical shells with bolted joints.This paper takes cylindrical shells with bolted joints as research object,then conducts research on the nonlinear modeling,parameters identification of bolted joints,and the analysis of vibration characteristics of cylindrical shells with bolted joints.The main research contents of the paper are as follows:(1)A 3D macro-slip model is used to simulate the hysteresis nonlinear behavior between the connection interfaces,and a piecewise linear model is used to simulate the constraining force of bolts along the normal direction of the connection interface.Hysteresis curves and tension-compression curves of bolted joints are obtained through quasi-static experiments.The model parameters are identified through optimization and piecewise linear fitting of the experimental results.Based on the experimental results,the effects of the preload of the bolts and the shear load amplitude on the equivalent stiffness and energy dissipation of the bolt joints are analyzed.(2)The established nonlinear model of the bolted joints is applied to a cylindrical shell.Based on the Sanders thin shell theory,the nonlinear dynamic model of the cylindrical shell with bolted joints is established by the semi-analytical method.Then,the effects of the preload of the bolts,excitation amplitude,coefficient of friction and number of bolts on the dynamic response and interface states are analyzed(3)Considering the spatial distribution of contact pressure on the contact interface,a new critical slip force density function is introduced,and an improved Iwan micro-slip model is established.Then the micro-slip model is introduced into the model of the bolted joints,and a new nonlinear model of the bolted joints that is more in line with the actual contact characteristics is established.The parameters in the micro-slip model are adjusted by the previously proposed parameter identification method,and the improved Iwan model,Iwan model,and macro-slip hysteresis model are compared by hysteresis curves.Then,the improved Iwan model,Iwan model and the macro-slip hysteresis model are compared through hysteresis curves.(4)The simplified nonlinear model of bolted joints based on the improved Iwan model is applied to the flange-cylindrical shell model,and the semi-analytical method is used to establish the dynamic model of the cylindrical shell with bolted flange joints.In order to model and analyze the connection structure more accurately,the additional kinetic and potential energy caused by the flange and the moment of the bolt to the cylindrical shell caused by the eccentricity are considered in this section.Then the effects of the preload of the bolted joints and excitation amplitude on the vibration response are investigated.