Research On Vibration Characteristics And Diagnosis Of Cracked Rotor Based On Energy Tracks

In rotating machinery,it is easy to occur the crack initiation and propagation of rotor due to the influence of high-speed operation,variable period and alternating load.How to solve the coupling between nonlinear terms and cracks and how to detect cracks in high-speed region become one of the main problems in rotor crack detection.Considering the nonlinear model and dynamic equation of a cracked rotor system,the energy expression of the cracked rotor is derived,and the concept of energy space and energy tracks are introduced.Based on the concept of vibration energy space and tracks,the effects of different crack parameters and non-linear parameters on vibration characteristics are compared.The main contents of this paper are as follows:Firstly,the model of a nonlinear rotor with a crack in horizontal position is established.The crack function models are compared and selected.The stiffness matrix and nonlinear expression of the cracked rotor are derived.On this basis,the dynamic equation of the nonlinear cracked rotor is derived.In addition,based on the expression of the nonlinear term?^（0）,it is proposed that the gravity factor will cause1/2 sub-harmonic resonance under symmetric nonlinear component.The harmonic balance method is used to solve the theoretical solution,and the correctness of the theoretical solution conjecture is verified by comparing the numerical simulation and the theoretical solution,which two results are in good agreement.Secondly,based on Lagrange equation,the vibration energy transfer function is derived and the concept of energy space is proposed.The difference between vibration variation characteristics in phase space and vibration energy characteristics in energy space are compared by numerical simulation.The variation characteristics of energy FFT under different crack parameters is deeply studied.It is found that the energy space can strengthen the super harmonic vibration components caused by cracks.The vibration energy tracks of the system with different crack parameters and nonlinear parameters are calculated.It is found that the vibration energy track distortion can show the influence of crack opening degree,relative position and different nonlinear terms on the vibration characteristics well.The rule of vibration energy track of the system change under different crack parameters is quantitatively analyzed,which laid the foundation for the quantitative analysis of crack detection.Finally,the experiment has been carried out and the energy FFT and vibration energy tracks of the cracked rotor were test on the constructed experimental device.The results show that the energy FFT and the energy track distortion of the cracked rotor can diagnose the crack fault of the rotor,which provides a new method for analyzing the vibration response and fault diagnosis of the cracked rotor system.