scholarly journals The Dynamic Analysis of Two-Rotor Three-Bearing System

2015 ◽  
Vol 2015 ◽  
pp. 1-15
Author(s):  
Jianfei Yao ◽  
Jinji Gao ◽  
Ya Zhang ◽  
Weimin Wang
Keyword(s):  
Dynamic Behavior ◽  
Critical Speed ◽  
Amplitude Spectrum ◽  
Element Model ◽  
Nonlinear Phenomena ◽  
Motion Patterns ◽  
Unbalance Response ◽  
Mass Eccentricity ◽  
Coupling Stiffness ◽  
Bearing System

A finite element model considering the shear effect and gyroscopic effect is developed to study the linear and nonlinear dynamic behavior of two-rotor three-bearing system named N+1 configuration with rub-impact in this paper. The influence of rotational speed, eccentric condition, and the stiffness of coupling on the dynamic behavior of N+1 configuration and the propagation of motion are discussed in detail. The linear rotordynamic analysis included an evaluation of rotor critical speed and unbalance response. The results show that the critical speed and unbalance response of rotors are sensitive to coupling stiffness in N+1 configuration. In the nonlinear analysis, bifurcation diagram, shaft-center trajectory, amplitude spectrum, and Poincaré map are used to analyze the dynamic behavior of the system. The results of the research transpire that these parameters have the great effects on the dynamic behavior of the system. The response of the system with rub-impact shows abundant nonlinear phenomena. The system will exhibit synchronous periodic motion, multiperiodic motion, quasiperiodic motion, and chaotic motion patterns under rotor-stator rub interaction conditions. The dynamic response is more complicated for flexible coupling and two mass eccentricities than that of system with rigid coupling and one mass eccentricity.

Multilevel Optimization of the Geared Rotor-Bearing System for Multi-Objectives With Critical Speed Constraints

2004 ◽  
Author(s):  
T. N. Shiau ◽  
J. R. Chang ◽  
W. B. Lu
Keyword(s):  
Critical Speed ◽  
Transmission Error ◽  
Mesh Stiffness ◽  
Error Response ◽  
Critical Speeds ◽  
Gear Mesh ◽  
Unbalance Response ◽  
Multilevel Algorithm ◽  
Gear Mesh Stiffness ◽  
Bearing System

This paper presents the multi-objective optimization of a geared rotor-bearing system with the critical speeds constraints by using an efficient multilevel algorithm. The weight of each rotor shaft, the unbalance response, and the response due to the transmission error are minimized simultaneously under the critical speed constraints. The design variables are the inner radii of the shaft, the stiffness of bearings, and the gear mesh stiffness. The finite element method (FEM) is employed to analyze the dynamic characteristics and the method of feasible direction (MFD) is applied in the optimization of the single objective stage. Based on the sensitivity analysis that gear mesh stiffness has almost no influences on the critical speeds of the uncoupled modes of two shafts, an efficient multilevel algorithm composed of system and subsystem levels is developed. In the cycle of iteration, the minimization of the shaft weight is performed in the subsystem level with the critical speed constraints of only uncoupled modes of two shafts and the unbalance response and the transmission error response are reduced in the system level with the critical speed constraints of only coupled modes. It is indicated from the numerical results that the shaft weight, the unbalance response, and the transmission error response via the multilevel technique (ML) are all reduced much more than those via the weighting method (WM) and the goal programming method (GPM).

scholarly journals Nonlinear Dynamic Behavior of Double-Disk Isotropic Rotor System with Axial Rub-Impact

2011 ◽  
Vol 2-3 ◽  
pp. 678-682
Author(s):  
Y. Zhang ◽  
W.M. Wang ◽  
J.F. Yao
Keyword(s):  
Dynamic Behavior ◽  
Nonlinear Dynamic ◽  
High Speed ◽  
Element Model ◽  
Rotor System ◽  
Self Healing ◽  
Rotor Bearing ◽  
Nonlinear Dynamic Behavior ◽  
Operation Stability ◽  
Bearing System

In the case of considering the shear effect and gyroscopic effect, a finite element model is developed to study the nonlinear dynamic behavior of a double-disk isotropic rotor- bearing system with axial rub-impact in this paper. The influences of rotational speed and initial phase difference on the operation stability of the rotor-bearing system are discussed. It transpires that the response of the rotor system with axial rub- impact is mainly synchronous periodic motion. The vibration signals of axial rub-impact include such as the synchronous signal and the multiple frequencies, in which the synchronous signal is dominating signal. There is no weakening wave phenomenon in time wave plot. All the results are in reasonable good agreement with those observed in engineering. The results of this paper could provide certain reference for fault diagnosis and self-healing of large high-speed rotating machinery system, thus ensuring the safe operation of the system.

Analytical and Experimental Study of Dynamic Characteristics of Rod Fastened Rotor-Bearing System Under Preload Saturation

2013 ◽  
Author(s):  
Mingjian Lu ◽  
Haipeng Geng ◽  
Guohui Xu ◽  
Lie Yu ◽  
Weimin Wang
Keyword(s):  
Dynamic Characteristics ◽  
Critical Speed ◽  
Contact Stiffness ◽  
Element Model ◽  
Analysis And Design ◽  
Contact Effect ◽  
Rotor Bearing ◽  
Equivalent Bending Stiffness ◽  
Rod Fastening Rotor ◽  
Bearing System

This paper investigates the dynamic characteristics of a composite rotor fastened by rods. Contact stiffness and equivalent bending stiffness between discs with different rod preloads of the rotor are obtained respectively by using the elastic and elastic-plastic contact theory. The finite element model of rotor-bearing system is built with Timoshenko beam elements. Critical speeds are respectively calculated with and without the consideration of contact effect, including the changing bearing dynamic coefficients. A test rig of rod fastening rotor-bearing system has been constructed to verify the numerical model results. The results show that the critical speed increases with rod preload and it keeps almost constant when the rod preload reaches a certain value, called preload saturation. The experiments demonstrate that the rod fastening rotor under preload saturation has the similar dynamic characteristics as integral rotor, such as the critical speed and backward whirl with asymmetric support stiffnesses. This kind of rotors which are under preload saturation can be analyzed and designed as an integral one without considering the contact effect. The study gives referential recommendations for analysis and design of a class of composite rotors which contain discs and rods.

Prediction of the Dynamic Behavior of Systems Modelled With Periodic Coefficients: Application to Asymmetric Rotors

1993 ◽  
Author(s):  
Aline Sayettat-Beley ◽  
Phillippe Couderc ◽  
Guy Ferraris ◽  
Michel Lalanne
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Dynamic Behavior ◽  
Degrees Of Freedom ◽  
Floquet Theory ◽  
Element Model ◽  
Periodic Coefficients ◽  
Moments Of Inertia ◽  
Unbalance Response ◽  
Simple Models

Abstract This work is concerned with rotors having unequal area moments of inertia which necessarily lead to equations with periodic coefficients when the bearings are asymmetric. Following a study of the main phenomena and responses to classical forces on simple models, stability and unbalance response of a large finite element model are considered using a pseudo-modal technique and Floquet theory. Results obtained are satisfactory and show that the method is effective in accurately predicting the dynamic behavior of asymmetric rotors modelled with a significant number of degrees of freedom.

Unbalance Response of an Elastic Rotor in Damped Flexible Bearings at Supercritical Speeds

1971 ◽  
Vol 93 (2) ◽  
pp. 265-275 ◽  
Author(s):  
Neville F. Rieger
Keyword(s):  
Critical Speed ◽  
Mode Shapes ◽  
Rotor Speed ◽  
Flexible Rotor ◽  
Relative Stiffness ◽  
Unbalance Response ◽  
Fluid Film Bearings ◽  
Transmitted Force ◽  
Rotor Mass ◽  
Bearing System

The unbalance response of a uniform flexible rotor in fluid-film bearings has been analyzed for speeds up to 20 times the lowest rigid-bearing critical speed. Rotor mass and elasticity are distributed uniformly along the length of the rotor. A single radial speed-dependent force is used to represent the rotor unbalance. The rotor is assumed to operate in stable plain cylindrical bearings which are represented by direct and cross-coupled spring and damping forces. The influence of rotor speed, bearing operating eccentricity, relative stiffness of rotor and bearings, and unbalance location along rotor on the performance of the rotor-bearing system has been determined. Results are presented as charts of rotor maximum whirl amplitude and of bearing maximum whirl transmitted force for wide ranges of the foregoing parameters. Mode shapes at critical speeds are also included.

Whirl Speeds and Unbalance Response of Rotor-Bearing Systems Using Finite Dynamic Elements

1997 ◽  
Author(s):  
Bo-Suk Yang ◽  
Hyung-Sub Hwang ◽  
Sae-Kyoo Oh
Keyword(s):  
Finite Element ◽  
Shape Function ◽  
Element Model ◽  
Rotor Dynamics ◽  
Shape Functions ◽  
Unbalance Response ◽  
Rotor Bearing ◽  
Dynamics Problems ◽  
Dynamic Element ◽  
Bearing System

Abstract The conventional finite element model for rotor-bearing system are formed using shape functions which are based on static displacements, and can lead some errors in analysis of general rotor dynamics problems. A procedure is presented for dynamic modeling of rotor-bearing system which consist of finite dynamic shaft elements, rigid disk, and bearing element. A finite dynamic element model including the effects of rotary inertia, gyroscopic moments, axial force, and axial torque is developed using the frequency dependent shape function. The natural whirl speeds, stability, and unbalance response of rotor system are calculated on several cases and compared with the conventional finite elements.

Prediction of the Structural Dynamic Behavior of High Speed Turning Machine Spindles

2014 ◽  
Vol 555 ◽  
pp. 567-574
Author(s):  
Constantin Dogariu ◽  
Doru Bardac
Keyword(s):  
Finite Element ◽  
Dynamic Behavior ◽  
Dynamic Characteristics ◽  
High Speed ◽  
3D Model ◽  
Element Model ◽  
Structural Dynamic ◽  
Spindle Bearing ◽  
Machine Spindle ◽  
Bearing System

This paper presents a method to investigate the dynamic behavior of a turning high-speed spindle system. The machine tool main spindle unit is focused on direct driven spindle units for high-speed and high performance cutting. This paper analyzes the static behavior for a turning machine spindle and presents some activities to improve the CAD model for such complex systems. The proposed models take into account the spindle with the bearing detailed system. The analysis was performed during the design activity and was based on Finite Elements Method. Starting from the 3D model, using FEM done by means of ANSYS analysis, structural dynamic behavior was evaluated. The aim of this paper is to develop a finite element model of the machine spindle system and use this method for design optimization. The 3D model was designed using the Solidworks CAD software. In order to obtain accurate dynamic characteristics of the spindle-bearing system during the design stage, the finite element model is simulated using dedicated software, and a method in which springs and damping units imitate bearing support. The proposed method can predict the regular pattern in which bearing stiffness and bearing span affect natural frequency and harmonic response. The research demonstrates that this method predicts the dynamic characteristics of the spindle-bearing system therefore it can be a reference for dynamic optimization design of spindle-bearing systems in turn-milling centers. The static analysis was presented in another paper. The thermal analysis will be presented in a future paper.

Dynamic modeling and vibration response analysis of a synchronous motorized spindle with inclined eccentricity

2021 ◽  
pp. 107754632110233
Author(s):  
Wei Feng ◽  
Kun Zhang ◽  
Baoguo Liu ◽  
Weifang Sun ◽  
Sijie Cai
Keyword(s):  
Analytical Method ◽  
Vibration Response ◽  
Mass Force ◽  
Motorized Spindle ◽  
Dynamic Displacement ◽  
Unbalanced Mass ◽  
Unbalanced Magnetic Pull ◽  
Spindle Bearing ◽  
Mass Eccentricity ◽  
Bearing System

The air-gap eccentricity will produce unbalanced magnetic pull and cause vibrations and noises in a motor. In this study, the dynamic behavior of a synchronous motorized spindle with inclined eccentricity is investigated. A semi-analytical method is proposed to model the unbalanced magnetic pull and the electromagnetic torque of a rotor with inclined eccentricity, and the semi-analytical method is verified by the finite element method. The dynamic model of a spindle-bearing system is built by taking the centrifugal force and gyroscopic effects into account. Then, the vibration response of dynamic displacement eccentricity, inclined eccentricity including displacement eccentricity and angle eccentricity, rotating speed, and unbalanced mass eccentricity in both time domain and frequency domain are simulated and analyzed. The results show that the eccentricities can lead to fluctuations in amplitudes of the dynamic displacement response and the angle response. The frequency components of the dynamic responses are the combination of rotating frequency, VC frequency, and power frequency. It is indicated that the coupling interactions of bearing forces, unbalanced mass force, and unbalanced magnetic pull have an obvious effect on the spindle-bearing system.

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