Model-based Rotor Crack Fault Diagnosis Method

The rotor is the core component of the aeroengine.The shaft is easy to crack during operation,which can easily cause the aeroengine rotor to vibrate too much.If the crack failure is not found in time,the rotor in the unhealthy state will affect the engine performance and may lead to serious accidents,so the crack rotor monitoring and fault identification of the engine safe and reliable operation of great significance.Accurately establishing the mathematical model of crack rotor and understanding the dynamic characteristics of the crack rotor are the preconditions and foundations of fault diagnosis.In this paper,the mathematical model of cracked rotor is established.The model-based method is used to diagnose rotor crack faults.The actual cracked rotor is studied experimentally.The dynamic characteristics of cracked rotor are analyzed.The crack rotor modeling method and crack identification The accuracy of the method.Firstly,based on the mechanics of materials and fracture mechanics,the six-degree-of-freedom Timoshenko element model was used to derive the flexibility and stiffness matrixes of different types of cracks(straight crack,oblique crack and semi-parabolic crack).The Crack Closure Line(CCL)method was used to describe the respiratory effects of cracked cells.The mathematical model of the respiratory crack rotor system was established and the variation of element stiffness under different parameters of different types of cracks was analyzed.The newmark_? integral method and stress intensity factor are used to solve the dynamic response of the respiratory crack rotor system.Secondly,the dynamic response of cracked rotor system is studied.The effect of different crack depths,different crack angles and different unbalanced sizes and phases on the system vibration response is analyzed at a constant rotational speed.It is found that the cracked rotor produces obvious harmonic response components at subcritical rotational speed.Sub-harmonic resonance occurs when the critical speed is around 1/2 and 1/3,and the large unbalanced force has an inhibitory effect on the nonlinear characteristics of the crack.Later,a model-based fault identification method was used to identify rotor cracks and unbalance faults.The method expresses the fault parameter information as the harmonic equivalent force,and the unbalance and crack faults are identified by Huber-M estimation.The influence of noise on fault identification accuracy is studied,and the robustness of Huber-M estimation method is analyzed.Finally,the rotor test bed is established to obtain the vibration response of the rotor system rotating disk.The vibration characteristics of the actual cracked rotor system are analyzed and compared with the simulation data to verify the accuracy of the mathematical model of the crack rotor.The fault identification method is used to identify the actual measured data.The results show that the method can identify the fault information of the rotor system more accurately.