Study On Nonlinear Behavior Of A Contact-rubbing Jeffcott Rotor System

Rotating machinery is one of the most widely equipment in national foundation establishment and industry. With the increase of machinery operating speed and efficiency, the rub-impact fault of stator and rotor is common in rotating machinery, and it is one of the main reasons in mechanical failure. The rotor system with the rub failure is nonlinear vibration system of piecewise linear stiffness. Therefore, with the modern nonlinear theory and the rotor dynamics theory, the dynamic behavior of the small gap rotor system is investigated, it is very important significance for early diagnosis of rotor fault to analyze the dynamical gap rotor. The main contents of the paper are as follow:(1) The Jeffcott rotor dynamic model with rub-impact of rigid bracing is established, by means of some nonlinear dynamics, the nonlinear response of the rotor with various parameters is analyzed. Based of Matlab7.0, the fourth-order Runge-Kutta method for dynamical characteristics of a rotor system with rub-impact is used in numerical simulation. The efforts of bifurcation diagram are analyzed, through continuous change various parameters, for example, rotating speed, misalignment, stator and rotor gap, stator stiffness and damping coefficient. According to the various motion shapes of the rotor analyzed nonlinear response with the effort of rub is analyzed on the basic of time-history diagrams, axis orbit, phase diagram, Poincare maps and spectrum, etc.(2) Considering of the nonlinear oil film force of bearing and nonlinear rub-impact force, the dynamic model rotor-bearing-systems with rub-impact is established. According to numerical simulation, the nonlinear dynamic behaviors in running are investigated on the rotor system with rub-impact faults, and the influence of the rotate speed and the imbalance is analyzed on the bifurcation and the chaos of the rotor system, and some behaviors curves of different parameters on the nonlinear dynamic properties are gained, for example, time-history diagrams,axis orbit, phase diagram, Poincare maps, etc. And nonlinear chaos behaviors of the system are discovered.