Study on the Nonlinear Dynamics of a Bearing-Rotor System Having Nonlinear Bearing Stiffness
|School||Xi'an University of Architecture and Technology|
|Course||Mechanical Design and Theory|
|Keywords||Nonlinear Dynamics Numerical Integration Methods Bifurcation Bearing-Rotor System Chaos|
Being as an important cadre, the ball bearing is widely used in every field of mechanical engineering. With the development of computer science and nonlinear dynamics, especially the quick tempo of revolver, the thought that ball bearing’s stiffness is linear excessively predigested problems in rotor dynamics, which frequently can not find enough exact answers. Dynamic behaviors of a rotor with high speed supported by ball bearings is greatly determined by the characteristics of the bearing, especially its nonlinear radial stiffness. For the sake of stability and security of a rotor, it is necessary to study the effects of a ball bearing’s nonlinear stiffness on system’s dynamic behaviors. The main object of this thesis is to study a horizontal rigid rotor supported by deep groove ball bearings, analyze the nonlinear dynamics of rotor system in case of different internal clearances, calculate the rotor system and simulate its complex nonlinear dynamic behaviors.The radial internal clearance of a deep groove ball bearing is taken as the main parameter, the effect of which on the dynamics response of the two kinds of rotor system (balanced or unbalanced) is studied. The results of a parametric study have resulted in the observation that the systems may undergo period doubling bifurcation, quasi-periodic and chaotic motions. In some typical parameter regions the bifurcation diagrams, the shaft centerline orbit, the phase portrait, the Poincaré maps are acquired by numerical integration methods.For the balanced rotor system, radial internal clearance is an important parameter for determining the dynamics response. It is seen that with increase in clearance the region of unstable and chaotic response becomes wider, meanwhile the peak value of displacement response becomes greater.For the unbalanced rotor system, the nonlinearity is both due to Hertzian contact and the radial internal clearance of bearing. The system is excited by the varying compliance frequency and the rotational frequency. The results have shown the appearance of instability in the dynamics response of the system as the speed of the bearing-rotor system is changed.Through analysis of calculating results, some important conclusions are obtained, which may be useful for engineering applications.