Research On Dynamic Characteristics Of Single Coupled Clamp Of External Pipe System Of Aeroengine

As the transmission channel of various media and energy in the engine,the external pipe system of aeroengine is an important component of the engine.The clamp is an important connecting part of the pipe system.It also plays an important role in frequency adjustment and vibration reduction of the pipe system.At present,the study of the clamp mostly focuses on the influence of clamp layout on the characteristics of the pipe system,ignoring the study of the dynamic characteristics of the clamp itself.Because of metal rubber which is a kind of non-linear material with large damping and friction contact between the liner and the pipe,the clamp is non-linear.Its nonlinearity directly affects the dynamic response analysis of the pipe system.However,the clamp is often simplified to fixed restraint or linear spring restraint,ignoring the non-linearity of the clamp.Therefore,the paper studied the dynamic characteristics of the clamp,established the accurate linear model of the clamp and the equivalent dynamic model of the clamp considering the nonlinear influence,so as to further improve the analysis accuracy of the pipe system vibration response and the dynamic design of the pipe system.The specific research work of the paper is as follows:Firstly,the method of identifying the linear parameters of the clamp based on low-amplitude excitation modal test and the method of identifying the nonlinear parameters of the clamp based on constant voltage test were described.Laser modal test method,model validation theory,equivalent linearization theory and the method of converting constant voltage frequency response function to constant displacement and constant velocity frequency response function were introduced in detail.Secondly,the low-amplitude excitation modal test was carried out on the straight pipe system with the clamp under different tightening torques,and the finite element model of the pipe system was updated based on the test data to identify the linear stiffness parameters of the clamp under different tightening moments.Several clamps of the same specification were tested,and the linear stiffnesses of different clamps were compared,and the reasons for the difference of the stiffnesses of the clamps were further analyzed.Through the experimental and simulation study on the influence of clamp position on the dynamic characteristics of the straight pipe system with the clamp,it was verified that the linear stiffness characteristics of the clamp obtained in this paper were also applicable in all positions of the straight pipe.Based on this,the influence of clamp on the characteristics of complex pipe system could be simulated.Finally,through the fast sinusoidal sweep test of the clamp straight pipe system,it was confirmed that the straight pipe system had obvious nonlinearity in the first and second modes.The constant voltage test was carried out around the first mode of the straight pipe system.The constant voltage frequency response function was transformed into constant displacement and constant velocity frequency response function by spline interpolation,and the horizontal equivalent stiffness and damping function of the clamp were further obtained.Combined with the equivalent linearization theory,the horizontal nonlinear stiffness and damping parameters of the clamp were identified.Similarly,based on the constant voltage test of the second mode of the clamp straight pipe system,the vertical non-linear stiffness and damping parameters of the clamp were identified.The effectiveness of the proposed nonlinear equivalent dynamic model of the clamp was verified by the response prediction of the clamp straight pipe system modal test and constant displacement test.