The Assessment Method For Pedestal Looseness Of Rotor Systems Via Nonlinearity Measure

As a key component in a rotating machine,the rotor-bearing system plays an irreplaceable role in the areas of industry.With the development of science and technology,rotating machinery has higher demands for the accuracy and reliability.Pedestal looseness is one of the most common factors with the greatest impact on precision and reliability.In this paper,the pedestal looseness of rotor-bearing systems is studied,and the influence of the gap of loosening to the system response is analyzed.Due to changes in loosening clearance have the obviously effect on the nonlinear dynamic behavior of the rotor-bearing systems,the assessment method for Pedestal looseness via nonlinearity measure is proposed,and the effectiveness of this method is demonstrated by experiments.The main research work is given as follows:(1)The dynamics of rotor-sliding bearing system are studied.Based on the modeling of nonlinear oil film force,the dynamic model of the rotor-sliding bearing system is established.The Runge-Kutta method is used to integrate the dynamic model,and nonlinear dynamic characteristics of the rotor-sliding bearing system are analyzed.At the same time,according to the kinetic analysis,the basic knowledge of rotor system dynamics,the basic concepts of chaos and fractal and the main research methods of nonlinear equations are briefly introduced.(2)In this paper,the assessment method for pedestal looseness of bearing-rotor systems is developed based on nonlinearity measure.Firstly,the fundamental theory of nonlinearity measure is introduced.And the dynamic model of the rotor-sliding bearing system with single support loose fault is established,the nonlinear response of the system with the loosening gap is analyzed by means of the axis trajectory diagram and the time domain response graph.And the influence of the rotor mass on the loosening gap is analyzed.The models of rotor-bearing system with and without support loosening are established,and linear approximate dynamic model is obtained by using Taylor expansions for nonlinear terms.To quantity the dynamical differences between the nonlinear model with linear model,the results of nonlinearity measure of nonlinear rotor-bearing system are obtained and the evaluation for the state of supporting loosening can be achieved.(3)In order to meet the actual working conditions of rotating machinery,the dynamic model of rotor-sliding bearing system with loose-rubbing coupling fault is established.Undering different rotor mass,the dynamic behavior response of the system is analyzed.by changing the degree of loose clearance of the support,It is found that the motion law of the rotor system is: periodic motion-quasi-periodic motion-chaotic motion.And the assessment method is used to evaluate the rotor system under the coupling fault,and the influence of the loosening size on the system is reflected.(4)Built a single support loose fault,rub-impact-support loose coupling fault rotor system simulation test-bed.The method of state evaluation based on the nonlinear measurement of the system is validated.The results show that the method can effectively evaluate the state of the loose rotor system.Finally,on the basis of the method validation,the state corresponding to the rubbing is judged by the comparative analysis,which provides the theoretical basis for the fault identification.