The Rotor System With Slant Crack Nonlinear Output Frequency Response Function Characteristic Research

The paper makes a deep research on slant crack rotor fault diagnosis. Based on the deficiencies of the traditional spectrum characteristic analysis method on slant cracked rotor system fault diagnosis, a fault diagnosis method of slant cracked rotor based on nonlinear output frequency response function (NOFRF) is proposed. And the NOFRF characteristic of containing slant crack rotor system was simulated and experimental verification. Innovative achievements are obtained. This article contents are mainly as follows1. The topic and research significance of this subject is discussed, the methods of nonlinear system identification and the domestic and foreign research situation on the crack fault identification of rotor system are discussed, the research situation and achievements of nonlinear output frequency response function are stated, on the basis of, the main content and innovation of this paper is given.2. The stiffness matrix of a shaft with slant transverse crack under the common action of axial force, moment and torque was derived based on material mechanics, local flexibility and fracture mechanics theory and apply strain energy release rate method. The relationships between the stiffness and some parameters such as the crack inclination, the crack depth and the slenderness ratio are discussed in a static situation fully open crack. The opening and closing regularity of the crack and the shaft rigidity varying characteristics was simulated in a steady state rotating by apply the stress intensity factor is zero method, and the time-varying characteristics of inclination of 45°cracked shaft stiffness was detailed study.3. The full-type oblique crack rotor dynamics model was established, analyze and discuss the nonlinear output frequency response function of full-type oblique crack rotor system on different crack angle and crack location and crack depth, When fully open type inclined crack is on the rotating shaft, when the crack depth is shallow, as if using the traditional spectrum analysis method for fault diagnosis, will not be able to more accurately identify the crack fault, and each order NOFRF value of system was analysisd by the method of nonlinear output frequency response function can accurately identify system of crack fault, effectively overcome the disadvantages of traditional methods. When the crack Angle and crack depth at the same time, the G4(j4ωF) value is quite sensitive to changes in position of crack, and as the crack near the rotary table, G4(j4ωF) value is larger.4. The nonlinear output frequency response function characteristics of respiratory type inclined crack rotor system under different crack angle and crack depth and crack position. The each order NOFRF value of system with the increase of crack angle are increased, especially the G3(jωF) value increase amplitude is bigger, and the first order frequency response of the system of Y(jωF) is consists of two parts, the G1(jωF) and G3(jωF), and first order response of the system is mainly affected by Y(jωF).So you can through the changes of the G3(jωF) value to judge one times frequency of system response, so we can know that the one times frequency of system response is more sensitive to the change of crack angle, which can be identified by the changes in the crack angles double system response, the value also increase, but the extent of increase is not the same.5. The NOFRF characteristics of straight slant breath type cracked rotor system were compared. When the crack on the shaft is the breathing type slant crack and the crack depth unchanged, the NOFRF values of the rotor system with crack location near the rotary table. It can be seen that each order NOFRF value on the sensitive degree of different crack location, which can be through the change of order NOFRF value, to identify the system of crack failure problems.When the crack on the shaft is breathing type straight crack, when the depth of the crackisnot constant, the NOFRF values of the rotor system can basically with the crack location near the rotary table, and increase its value. And the value of the G2(j2ωF) and G4(j2ωF) is not as the location of the crack near the rotary table the greater, but increased after decreased first, the second order frequency response Y(j2ωF) is made up of the G2(j2ωF) and the G4(j2ωF), and the twice the frequency response of the rotor system was mainly affected by the Y(j2ωF).6. Finally, the content of this paper is summarized, and further research is prospected.