Studies On Stiffness And Dynamic Behavior Of Cracked Rotor

It is of great significance to study the failure mechanism of the rotor system, which is the key component of the rotating machinery, to ensure its long-term stability and operating reliability for the rapid development of the national economy and the stability of our daily life. It’s necessary to do the research about the dynamic characteristics of the cracked rotor system as rotor crack is one of the most common failures. Based on the neutral axis theory, a new stiffness model of the switching crack was proposed. Then, the cracked rotor system with rigid supports and oil film supports, and rotor system with coupling fault of crack and rub-impact with film supports were respectively studied in detail. Moreover, the influences from system parameters on the dynamic responses of the system were also analyzed. The main contributions of the paper are as follows:1、By applying the neutral axis theory and considering the influence of the open area of crack on the neutral axis position, the open-close regularity of the crack was presented. Based on the moment of inertia and product of inertia, the shaft stiffness coefficient with an open-close crack was investigated. The present stiffness model was compared with traditional stiffness models. The stiffness coefficients under different parametric conditions in the Cartesian coordinate system were discussed.2、The dynamic equations were established to study a cracked rotor with rigid supports, a cracked rotor with oil film supports, and a rotor with coupling fault of crack and rub-impact with oil film supports, respectively. The dynamic characteristics of the systems with single crack, crack coupled with oil film force, crack coupled with oil film force and rub-impact force were studied, respectively.3、By numerical integration methods, one can solve the equations and get the vibration responses. The periodic response, quasi-periodic response,and chaos of the system were analyzed with the help of the bifurcation diagrams, axis portraits, phase plane portraits, Poincare maps, amplitude spectrum and the crack’s open-close law diagrams of the rotor motion.