The Method For The Optimization Of The First-Order Vibrational Frequency Of Structure With Bolt Connections

With the requirements of the observing resolution ant the optical capacity of the photoelectric theodolite continuously improved,the dimension of whole structure becomes bigger and bigger.Therefore the study of the vibration characteristics on the improvement of the structure reliability and the accuracy of measurement is very important.In order to avoid the resonance vibration of the structure,the dynamic characteristics of the structure should be optimized to systematically.Because the nonlinear dynamic effects caused by the connective unit,the bolt connection structure makes it complicated to analyze the dynamic properties of the structure and control the vibration characteristics of structure with bolt connection.The linear model has limited capability,and it is necessary to study the effects of nonlinearity vibration.The research of the structural dynamics problems with the bolt connection,are usually based on the linearization method.The bolt connection is simplified as the combination form with the linear spring and damping unit,and the parameters of the linear elements is given by the model updating,analysis or experimental identification.However,under the cycle of the forced vibration environment,the relative slippage in tangential and the impact of the collision in the normal vector may occur.Therefore,the nonlinear connection unit must be adopted.At the same time,in order to simplify the vibration characteristic of structure with bolt connection,suppressing the nonlinear resonance response caused by the bolted is necessary.The thesis mainly aims at decreasing the resonance effect of the bolt connection and improving the fundamental frequency vibration of the structure.According to the source of nonlinear resonance,the thin elastic layer at the contact surface is proposed to weaken the nonlinear resonance effect,which is caused by the changes of the bolted contact states.The numerical simulation and experimental results show this ap-proach can significantly weaken the nonlinear resonance of the bolted structure.On the basis of the result,the distribution of adhesive layer is optimized to suppress more effectively the harmonic response.Based on weakening the nonlinear harmonic response to optimize the fundamental frequency vibration,the cantilever and the flange as examples are used to optimize their fundamental frequency and their fundamental frequency vibration are realized to improve.The innovation of this paper is to suppress effectively the nonlinear resonant response on the premise of limited thickness and area of the adhesive layer,through adding the elastic layer to the contact surface of the bolt connection and optimizing the distribution of adhesive layer.