Analysis And Experimental Research On Impedance And Vibration Isolation Characteristics Of Membrane Elastic Coupling

Elastic coupling is a common power transmission component in shafting transmission system.Because of its good damping effect on transmission system,it is widely used in shafting transmission of various mechanical devices.Taking a metal diaphragm coupling as the research object,this thesis analyzes its vibration transmission characteristics from two aspects of impedance characteristics and vibration isolation characteristics.The research results have certain significance for the design,manufacture and engineering application of the coupling.The main contents of this thesis are as follows:(1)The influence of bolt pre tightening force and exciting load on the static stiffness of coupling diaphragm group and the contact state of contact pair are studied and analyzed.The results show that,within 200% of the rated bolt preload,with the increase of bolt preload,the stiffness of the diaphragm group increases gradually,but the trend slows down,and there is an obvious inflection point in the curve;With the increase of the excitation load,the relative slip displacement between the contact pairs shows a trend of approximately unchanged first and then increased significantly,while the contact pressure between the contact pairs shows an obvious upward trend.When the excitation load is large enough,the contact between the diaphragm and the diaphragm will even occur.(2)Through the research and analysis of the vibration mode of the diaphragm group with prestress,it is found that with the increase of the bolt preload,the first several natural frequencies of the diaphragm group gradually increase,but the corresponding natural frequencies of the last several modes have little change.The main reason is that the bolt preload affects the stiffness of the diaphragm group,resulting in the deviation of the resonance peak and anti resonance peak.Based on the above research,the simplified model of the coupling is established according to the structural characteristics of the coupling,and the simplified model is modified by introducing the reduction factor.The stiffness,mass and other attribute parameters of the modified simplified model and the initial model are approximately equal.(3)Based on the four terminal parameter method and mechanical impedance theory,the impedance characteristics of the coupling are calculated and analyzed,and the input impedance and transfer impedance of the coupling are obtained;The finite element method is used to analyze the vibration isolation performance of the coupling.Based on this research,the influence of installation status on the vibration transmission characteristics of the coupling is analyzed by connecting three different length shaft segments at both ends of the coupling and applying three different boundary conditions on the shaft segment.It is found that the input impedance and axial vibration level drop increase gradually with the increase of the length of the connecting shaft in the frequency band of 10 ～ 2000 Hz.The results show that the input impedance increases by 12.4db and 16.2db respectively,and the vibration level drop increases by 8.3db and 18.4db respectively;By comparing the results of different boundary conditions,it is found that the influence of boundary conditions on impedance is small,and the influence on vibration level drop is large.(4)The test platform of coupling vibration transmission characteristics is built,and the impedance characteristics and vibration isolation characteristics of the coupling are measured.The test results are compared with the finite element calculation results,and it is found that the two results are more consistent,which verifies the accuracy and reliability of the calculation results.To sum up,this thesis analyzes the vibration transmission characteristics of membrane coupling,analyzes the influence of bolt preload on the static stiffness and vibration mode of membrane group,analyzes the influence of bolt preload and excitation load on the contact state,and analyzes the influence of coupling connection state on its vibration isolation characteristics and impedance characteristics,It provides a theoretical reference for the further improvement and optimization of the coupling.