Dynamic modelling of a rotor-bearing-housing system including a localized fault

2017 ◽  
Vol 232 (3) ◽  
pp. 385-397 ◽  
Author(s):  
Jing Liu ◽  
Yajun Xu ◽  
Yimin Shao
Keyword(s):  
Dynamic Characteristics ◽  
Ball Bearing ◽  
Contact Stiffness ◽  
Great Influence ◽  
Fault Detection And Diagnosis ◽  
Time Dependent ◽  
Housing System ◽  
Stiffness Coefficient ◽  
Rotor Bearing ◽  
Vibration Responses

An in-depth understanding of the dynamic characteristics through rotor-bearing-housing systems is very valuable for fault detection and diagnosis applications of rotating machines such as high-speed spindle, roll mill, gearbox, engines, etc. A new vibration model of a rotor-bearing-housing system considering the rotor compliance, elastic interface between the housing and outer race, housing compliance, and time-dependent excitations introduced by a localized fault on the inner and outer races of an inherent ball bearing is proposed in this work. An analytical method for calculating the time-dependent excitations including the time-dependent displacement excitation and contact stiffness coefficient between the ball and fault edges is presented. Differences between vibration responses of a rotor-bearing-housing system from the proposed model and the previous model without the rotor compliance in the literature are discussed. The presented model is used to discuss the influences of all the rotor compliance, housing compliance, and fault sizes on the races of the inherent ball bearing on the vibration responses and vibration transmission characteristics through the rotor-bearing-housing system, which cannot be formulated by the current dynamic models in the listed references. An experimental study is introduced to validate the presented model. The results show that the rotor compliance and time-dependent contact stiffness coefficient caused by the fault have great influence on the dynamic characteristics through the rotor-bearing-housing system. It also seems that the developed method can provide a new vibration modelling method for the vibration analysis for a rotor-bearing-housing system with and without the faults.

scholarly journals Dynamic Characteristics and Experimental Research of a Two-Span Rotor-Bearing System with Rub-Impact Fault

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Rui Zhu ◽  
Guang-chao Wang ◽  
Qing-peng Han ◽  
An-lei Zhao ◽  
Jian-xing Ren ◽  
...  
Keyword(s):  
Dynamic Characteristics ◽  
Critical Speed ◽  
Great Influence ◽  
Experimental Platform ◽  
Rotating Machine ◽  
Rotor Bearing ◽  
Before And After ◽  
Analysis System ◽  
The Stability ◽  
Bearing System

Rotor rub-impact has a great influence on the stability and safety of a rotating machine. This study develops a dynamic model of a two-span rotor-bearing system with rubbing faults, and numerical simulation is carried out. Moreover, frictional screws are used to simulate a rubbing state by establishing a set of experimental devices that can simulate rotor-stator friction in the rotor system. Through the experimental platform and its analysis system, the rubbing experiment was conducted, and the vibration of the rotor-bearing system before and after the critical speed is observed. Rotors running under normal condition, local slight rubbing, and severe rubbing throughout the entire cycle are simulated. Dynamic trajectories, frequency spectrum diagrams, chart of axis track, and Poincare maps are used to analyze the features of the rotor-bearing system with rub-impact faults under various parameters. The vibration characteristics of rub impact are obtained. Results show that the dynamic characteristics of the rotor-bearing system are affected by the change in velocity and degree of impact friction. The findings are helpful in further understanding the dynamic characteristics of the rub-impact fault of the two-span rotor-bearing system and provide reference for fault diagnosis.

Dynamic modeling of rotor-bearing-housing system with local defect on ball bearing using mass distribution and energy methods

2021 ◽  
pp. 146441932110037
Author(s):  
Yaofeng Liu ◽  
Changfeng Yan ◽  
Kai Wang ◽  
Xianghong Gao ◽  
Xin Zhang ◽  
...  
Keyword(s):  
Mass Distribution ◽  
Vibration Signal ◽  
Vibration Response ◽  
Outer Ring ◽  
Housing System ◽  
Local Defect ◽  
Distribution Method ◽  
Rotor Bearing ◽  
Vibration Responses ◽  
Rotor Mass

The rotor-bearing-housing system is widely used in rotating machines, which influences the performance of the whole machine. Considering the distribution of rotor mass, the rotor-bearing-housing system with local defect in the outer ring is modeled based on the energy method. In order to make the model agree well with the experimental results, a new rotor mass distribution method was introduced in the modeling process. The simulated vibration signal was obtained by solving the dynamic equations with the Runge-Kutta method. The vibration responses of rotor-bearing-housing system under different distributed disks at both drive end and fan end are simulated. In the simulation results, the outer ring fault signal at the drive end and the vibration signal at the fan end are compared with the experimental signals to discuss the influence of rotor mass distribution on the vibration response of the bearing at both ends of the system. The results show that the simulation signal generated by the dynamic model of the rotor-bearing-housing system with a more uniform rotor mass distribution is more consistent with the experimental signal. The vibration response of the faulty bearing at drive end is compared at different defect sizes, and the variation trend of the amplitude of their characteristic frequency is obtained. This method is helpful for structural optimization and fault diagnosis of the rotor-bearing-housing system.

Dynamic Characteristics of Linear Rolling Guide Joint Based on Contact Stiffness

2012 ◽  
Vol 490-495 ◽  
pp. 1342-1347 ◽  
Author(s):  
Jin Feng Li ◽  
Li Ping Wang ◽  
Li Wen Guan ◽  
Hui Feng Zhang
Keyword(s):  
Dynamic Characteristics ◽  
Natural Frequencies ◽  
Contact Stiffness ◽  
Great Influence ◽  
Mode Shapes ◽  
Relative Deformation ◽  
Equilibrium Equations ◽  
Normal Contact ◽  
Normal Contact Stiffness ◽  
Rolling Guide

The dynamic characteristics of linear rolling guide joint have great influence on the dynamic characteristics of machine tools. In this paper, the relative deformation of guide interface was analyzed based on Hertz theory and normal contact stiffness of guide joint was calculated first. Then, the vibration model of linear rolling guide joint was performed. The kinetic energy and potential energy of carriage-rail system was derived. Based on Lagrange’s approach, motion equilibrium equations of different vibration modes were derived. At last, vibration test was designed to get natural frequencies and mode shapes of the carriage. The natural frequencies agreed well with the values calculated by analytical approach. The research results provided a theoretical foundation for obtaining vibration characteristics parameters of linear rolling guide joint and a reliable way for analysis of the dynamic characteristics of similar machine joints

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.

Analysis of Dynamic Characteristics of Gas Turbine Rotor Considering Contact Effects and Pre-Tightening Force

2008 ◽  
Author(s):  
Qi Yuan ◽  
Rui Gao ◽  
Zhenping Feng ◽  
Jianlu Wang
Keyword(s):  
Gas Turbine ◽  
Dynamic Characteristics ◽  
Critical Speed ◽  
Contact Stiffness ◽  
Great Influence ◽  
Equivalent Stiffness ◽  
Tightening Force ◽  
Turbine Rotors ◽  
Tie Rods ◽  
Contact Effects

Modern gas turbine rotors are usually designed as combined rotors in which disks are tied together by one central tie rod or several tie rods distributed along the circumference. This structure has the advantages in cooling design, light weight and processing assembly, however it brings some problems and challenges in predicting the dynamic characteristics of rotor. No matter how many tie rods are used to fasten the disks, the rotor is not an integral or continuous structure any more. The contact effects between contact faces and the pre-tightening forces of tie rods have great influence on the rotor’s dynamic behaviors. Traditional methods to calculate the critical speed in rotor dynamics such as Transfer Matrix Method and 2-D Finite Element Method (FEM), based on the integral and continuous rotor, fail to consider factors of the contact effects and the pre-tightening forces of tie rods. Although the 3-D FEM can exactly calculate the critical speed, it is still time and resource consuming to establish and calculate such complex three-dimensional structures, even on the most advanced computers at present. In this paper, the traditional 2-D FEM is improved by considering the contact effects and pre-tightening forces of tie rods. Contact faces in the rotor are dealt as elements with equivalent stiffness but without mass, thus the rotor-bearing system of gas turbine are composed of contact elements, elastic elements, rigid disk elements and bearing elements. According to the improved 2-D FEM, a program is developed to calculate the critical speed and unbalance response of gas turbine rotors. The equivalent stiffness, serving as an important input parameter in the program and elements in the stiffness matrix of the system, is mainly determined by the contact stiffness between contact faces and the pre-tightening force. To find out relationships between them, GW (Greenwood and Williamson) statistical model is used and the equivalent stiffness of complex contact faces is obtained. According to the results, certain curves showing the relationship between equivalent stiffness of contact surface and pre-tightening force are obtained. By these curves and the program, we can easily calculate the dynamic characteristics of gas turbine rotors with satisfying accuracy and less time. To validate this method, the critical speed of a real rotor of a certain gas turbine was calculated with the program and curves, and the results agree well with the measured data.

Dynamic characteristics of a drill in the drilling process

2003 ◽  
Vol 217 (2) ◽  
pp. 161-167 ◽  
Author(s):  
B W Huang
Keyword(s):  
Dynamic Characteristics ◽  
High Speed ◽  
Thrust Force ◽  
Time Dependent ◽  
Drilling Process ◽  
Improve Quality ◽  
Vibration Model ◽  
High Speed Drilling ◽  
Spinning Speed ◽  
Twisted Beam

The dynamic characteristics of high-speed drilling were investigated in this study. To improve quality and produce a higher production rate, the dynamic characteristics of the drilling process need to be studied. A pre-twisted beam is used to simulate the drill. The moving Winkler-type elastic foundation is used to approximate the drilling process. A time-dependent vibration model for drilling is presented. The spinning speed, pre-twisted angle and thrust force effects of the drill are considered. The numerical analysis indicates that the natural frequency is suddenly reduced as the drill moves into a workpiece.

scholarly journals Research on dynamic characteristics of plate under pedestrian excitation based on Newmark-β

2018 ◽  
Vol 37 (4) ◽  
pp. 682-699
Author(s):  
Xinfang Ge ◽  
Weirong Wang ◽  
Wei Yuan
Keyword(s):  
Rectangular Plate ◽  
Dynamic Characteristics ◽  
Vibration Isolation ◽  
Great Influence ◽  
Interaction Model ◽  
Vertical Direction ◽  
Structural Vibration ◽  
Normal Walking ◽  
Plate Structure ◽  
Pedestrian Excitation

Development of micro and ultra-precision machining, precision instruments and equipment, precision assembly and testing has put forward more and more high requirements to vibration isolation on environmental elements, especially the pedestrian excitation generated by workers' normal walking. Therefore, it is very important to study the pedestrian excitation's influence on vibration characteristics of precision instruments and equipment. In this study, dynamic model including mathematical model of pedestrian excitation, interaction model between pedestrian and rectangular plate structure, the human–plate coupled dynamic equation in vertical direction of pedestrian–plate structure was established. And then we use the Newmark-β method to solve the time-domain step-by-step integration of the first four order modes' dynamic equations and study the influence of the linear notion trajectory along the central axis direction on the dynamic characteristics of the rectangular plate. By simulation, we discussed plate structure response under different conditions, including plate structure displacement and acceleration response under the single person excitation with different velocities, under normal walking velocity with different number of pedestrians and under this case of different distance between two pedestrians. The results show that the structural vibration induced by pedestrian excitation has great influence on dynamic characteristics of plate.

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