Race Of Bearing Research Articles

Geometric stabilization of bearing races by centerless rolling

The geometric stabilization of bearing races by centerless rolling is studied experimentally, for the outer races of ball bearings.

下レース軌道面に微小穴を設けたPEEKスラスト軸受の水中転がり疲労試験によるき裂発生の観察

下レース軌道面に微小穴を設けたPEEKスラスト軸受の水中転がり疲労試験によるき裂発生の観察

Vibration signature analysis of distributed defects in ball bearing using wavelet decomposition technique

The analysis of vibration signals acquired from a ball bearing with an extended type of distributed defects is carried out using wavelet decomposition technique. The influence of artificially generated defect and its location on outer and inner race of the ball bearing is observed using vibration data acquired from bearing housing. The comparison of diagnostic information from fast Fourier transform and time frequency decomposition method is made for inner and outer race of ball bearing with single as well as multiple extended defects. To decompose vibration signal acquired from bearing, db04 wavelet technique was implemented. It is observed that impulses appear with a time period corresponding to characteristic defect frequencies. The results observed from wavelet decomposition technique and fast Fourier transform reveal that the characteristic defect frequency is quite consistent even with change in location of defect. The extended type of distributed defects in the ball bearings can also be effectively diagnosed with the help of wavelet decomposition technique and fast Fourier transform.

Optimization of High Speed Machine Tool Spindle to Minimize Thermal Distortion

Thermal errors contribute significantly to the dimensional error on machined components. Various machine design and operating factors are responsible for the thermal error. In the present work, experiments are performed to understand the effect of spindle rotational speed and the chiller unit setting on the temperature distribution in the spindle and consequently the thermal distortion of the Tool Center Point (TCP). A metrology fixture is fabricated and calibrated to measure TCP displacements as a precursor to experimentation. In addition, multiple temperature sensors are affixed at critical points within the spindle. It is seen that the temperature distribution across the outer race of front bearings is non-uniform (> 2.5°C) which in turn indicates that the heat extraction is not uniform across the spindle. Concurrently, significant tilt (yaw and pitch angles of the order of 50μ radian) is visible at speeds greater than 5000rpm. In the second part of the paper, a thermal compensation model is developed in a linear regression framework. To improve robustness of the model and reduce redundancy, only five out of eighteen temperature sensors (two near front bearing, one each near rear bearing and motor coil and an ambient temperature) are chosen through Principal Component Analysis (PCA) and k-means clustering. The predictions of the model agrees well with the measurements taken from a different set of experiments.

A new method for measuring the rotational accuracy of rolling element bearings

The rotational accuracy of a machine tool spindle has critical influence upon the geometric shape and surface roughness of finished workpiece. The rotational performance of the rolling element bearings is a main factor which affects the spindle accuracy, especially in the ultra-precision machining. In this paper, a new method is developed to measure the rotational accuracy of rolling element bearings of machine tool spindles. Variable and measurable axial preload is applied to seat the rolling elements in the bearing races, which is used to simulate the operating conditions. A high-precision (radial error is less than 300 nm) and high-stiffness (radial stiffness is 600 N/μm) hydrostatic reference spindle is adopted to rotate the inner race of the test bearing. To prevent the outer race from rotating, a 2-degrees of freedom flexure hinge mechanism (2-DOF FHM) is designed. Correction factors by using stiffness analysis are adopted to eliminate the influences of 2-DOF FHM in the radial direction. Two capacitive displacement sensors with nano-resolution (the highest resolution is 9 nm) are used to measure the radial error motion of the rolling element bearing, without separating the profile error as the traditional rotational accuracy metrology of the spindle. Finally, experimental measurements are performed at different spindle speeds (100-4000 rpm) and axial preloads (75-780 N). Synchronous and asynchronous error motion values are evaluated to demonstrate the feasibility and repeatability of the developed method and instrument.

Nonlinear dynamic model and vibration response of faulty outer and inner race rolling element bearings

By considering the deep groove ball bearing as the research object, and using Hertzian contact theory and elastic mechanics and geometry, a nonlinear dynamic model is established herein for the study of vibration response of deep groove ball bearings having single defect on surfaces of inner and outer races. The outer race and inner race defect size parameters are introduced into this nonlinear dynamic model, and dynamic models of localized fault on outer race, inner race of rolling element bearing are simulated and analyzed by using Runge-Kutta method. Both simulated and experimental localized fault signals (acceleration signals) are subjected to the same diagnostic techniques; namely time domain waveform comparisons and envelope analysis. Then, the impact characteristic that reflects the fault severity in rolling element bearings is obtained from the time interval between two impact points. The simulating results are in accordance with experimental results, which proves the accuracy and practicality of the models used in engineering application. The characteristic defect frequencies and related harmonics are broadly investigated and presented herein. This proposed model provides theoretical basis for monitoring and fault diagnosis of rolling bears.

Nonlinear Dynamic Response of Cylindrical Roller Bearing–Rotor System with 9 Degree of Freedom Model Having a Combined Localized Defect at Inner–Outer Races of Bearing

ABSTRACTThis article presents a nonlinear dynamic model for a cylindrical roller bearing–rotor system with interaction forces between the inner race, outer race, and roller. Roller–race contacts are modeled predicting nonlinear stiffness (Hertz contact theory) and nonlinear damping for a rotor–cylindrical roller bearing system. Here a shaft–rotor bearing system is modeled with 9 degrees of freedom with one defect on the inner race and one defect on the outer race for a case of combined localized defects. In the mathematical formulation, contacts between rolling elements and inner and outer races are considered as nonlinear springs and nonlinear damping is taken into consideration. Contact force calculations with nonlinearity are solved using the Newton-Raphson method for n unknown nonlinear simultaneous equation. The Newmark-β implicit integration technique coupled with the Newton-Raphson method is used to solve the differential equations. The results are obtained in the form of a time domain plot, frequency domain plot, and phase plot/Poincare map. The validity of the proposed model is compared with experimental results. A bifurcation graph of speed versus peak amplitude predicts the behavior of the system.

A Computational Fluid Dynamics Simulation of Oil–Air Flow Between the Cage and Inner Race of an Aero-engine Bearing

In aero-engines, the shafts are supported on bearings that carry the radial and axial loads. A ball bearing is made up of an inner race, an outer race, and a cage, which contains the balls, these together comprise the bearing elements. The bearings require oil for lubrication and cooling. The design of the bearing studied in this work is such that the oil is fed to the bearing through holes/slots in the inner race. At each axial feed location, the oil is fed through a number of equispaced feedholes/slots but there are a different number of holes at each location. Once the oil has passed through the bearing, it sheds outward from both sides into compartments known as the bearing chambers. A number of studies have been carried out on the dynamics of bearings. Most of the analyses consider the contributions of fluid forces as small relative to the interaction of the bearing elements. One of the most sophisticated models for a cage–raceway analysis is based on the work of Ashmore et al. (2003, “Hydrodynamic Support and Dynamic Response for an Inner-Piloted Bearing Cage,” Proc. Inst. Mech. Eng. Part G, 217, pp. 19–28], where the cage–raceway is considered to be a short journal bearing divided into sectors by the oil feeds. It is further assumed that the oil exits from the holes and forms a continuous block of oil that exits outward on both sides of the cage–raceway. In the model, the Reynolds equation is used to estimate the oil dynamics. Of interest in this current work is the behavior of the oil and air within the space bounded by the cage and inner race. The aim is to determine whether oil feed to the bearing can be modeled as coming from a continuous slot or if the discrete entry points must be modeled. A volume of fluid (VOF) computational fluid dynamics (CFD) approach is applied. A sector of a ball bearing is modeled with a fine mesh, and the detailed simulations show the flow behavior for different oil splits to the three feed locations of the bearing, thus providing information useful to understanding oil shedding into the bearing chambers. This work shows that different flow behaviors are predicted by models where the oil inlets through a continuous slot are compared to discrete entry holes. The form and speed of oil shedding from the bearing are found to depend strongly on shaft speed with the shedding speed being slightly higher than the cage linear speed. The break-up pattern of oil on the cage inner surface suggests that smaller droplets will be shed at higher shaft speed.

Special Features of the Carbonitriding of Parts of Instrument Bearings Designed for Extreme Service Conditions

A study is made of complexly alloyed steel 8Kh4V9F2-Sh, which is used for fabricating parts of engineering bearings operating under extreme conditions. Vacuum processes are shown to be preferable to gas carburizing for hardening the races of precision bearings. Vacuum carburizing is shown to be an effective technique for forming quality diffusion layers.

Vibration modelling of nonuniform surface waviness in a lubricated roller bearing

Surface waviness is one important source of vibrations in a roller bearing. When the surface waviness occurs on the surface of the inner or outer race of a roller bearing, a time-varying deflection excitation and a time-varying contact stiffness excitation can be generated due to the changes in the curvature radii of the race with surface waviness at the contact position between the roller and the race of the roller bearing. In this paper, a new dynamic model (TDCE model) considering both the time-varying deflection excitation, the time-varying contact stiffness excitation, and the lubricating oil film is proposed to investigate vibration responses of a lubricated roller bearing with a uniform and a nonuniform surface waviness on its races, which cannot be accurately modelled by the previous time-varying deflection excitation (PTDE) model in the literature. Effects of the number, the maximum amplitude, and the nonuniform distribution of the surface waviness on the contact stiffness between one roller and the race with surface waviness are investigated, as well as the vibration responses of a lubricated roller bearing. Numerical results from the proposed model are compared with those from the PTDE model in the literature, which shows that the proposed TDCE model can provide more accurate impulses generated by the surface waviness on the races of the roller bearing. Moreover, the results show that the proposed method can provide a new vibration modelling method for a lubricated roller bearing with the uniform and nonuniform surface waviness on its races.

A study on the effect of acceleration on slip velocity and lubrication performance in cylindrical roller bearings

Skidding may cause wear and incipient failure of rollers and races of cylindrical roller bearings when the roller is loaded. The previous skidding studies on bearings are mainly focused on steady state condition. However, bearings often operate under different accelerations. This paper proposes an analytical model to investigate skidding between the maximum loaded roller and the races taking account of contact force and friction force between the roller, the cage and the races, fluid pressure and centrifugal force of roller. This model consists of nonlinear first-order ordinary differential equations which can be solved using Euler method. The results of this model are compared to the results of Harris model (steady-state condition) to analyze the effect of acceleration on skidding. A mixed elastohydrodynamic lubrication model which is capable of handling practical case with 3D machined roughness is used to study the lubricating performance between the maximum loaded roller and the inner race during acceleration. The results indicate that acceleration has a great impact on hydrodynamic pressure, friction coefficient, and contact stress, however, the acceleration can hardly affect oil film thickness and contact area ratio.

A numerical investigation of effects of defect edge discontinuities on contact forces and vibrations for a defective roller bearing

Vibration characteristics of a roller bearing caused by a roller passing over the defect on the races are determined by the contact forces between the roller and races of the bearing. The vibration characteristics and contact forces are determined by the sizes and edge discontinuities of the defect. Therefore, it is very useful to investigate the relationships between defect edge discontinuities and the contact forces, and those between defect edge discontinuities and the vibrations for diagnosing the defects with different edge discontinuities in the roller bearings. A dynamic nonlinear finite element model for a roller bearing with a localized surface defect considering different edge discontinuities on its outer race is developed using an explicit dynamics finite element software package in this work. The effects of the defect edge discontinuities, radial load, and shaft speed on the contact force between the roller and outer race of the roller bearing are investigated, as well as the vibrations of the bearing. In-depth analyses of the contact forces between the roller and localized surface defect with different edge discontinuities are presented, which did not study in the previous literatures. The numerical results show that the number of the impacts between the roller and end edge of the defect caused by the re-stressing is more than that between the roller and beginning edge of the defect caused by the de-stressing, which is also affected by the defect edge discontinuities.

Prediction of defect size in rolling element bearings using acoustic emission signals with an artificial neural network

In the condition monitoring of rotating machinery, vibration analysis of rolling element bearings is a popular diagnostic tool even though the vibration signals caused by bearing defects are distorted by other faults and mechanical noise, particularly in a hostile environment. The acoustic emission (AE) method is a non-destructive testing (NDT) technique used in structural health monitoring and its application for bearing diagnosis is gaining momentum as an alternative diagnostic tool due to its inherent high signal-to-noise (SNR) ratio. In earlier studies, although the researchers focused on different types of seeded defects, with random shape and size, and measured their vibration amplitude, they could not ascertain the correlation between the defect size and its respective vibration amplitude. A bearing test-rig was designed and established to study the various size defects in rolling element bearings. The experimental investigation reported in this paper predicts the bearing damage severity with respect to the AE amplitude level, using the artificial neural network (ANN) technique. This experiment includes seeded defects of various sizes, ie gradual increase of defect width on the outer race of radially-loaded cylindrical roller bearings at different parameters, and the data acquired through an acoustic emission probe. Experimental data was imported to the ANN, in which a multilayer perception model was used with a back-propagation algorithm using the input parameters of load, r/min and AE amplitude level and defect size as the output. The predicted defect sizes are compared with the actual seeded defect sizes and the percentage error was minimal. In this paper, an attempt has been made to predict the defect size with the help of AE and ANN techniques.

Tool and Method for Testing the Resistance of the Snow Road Cover to Destruction

The paper presents the design of the tool for efficient determination of the hardness of the snow road coating. The tool increases vertical positioning of the rod with the tip through replacement of the rod slide friction of the ball element by roll friction of its outer bearing race in order to enhance the accuracy of determining the hardness of the snow-ice road covering. A special feature of the tool consists in possibility of creating different impact energy by the change of the lifting height of the rod with the tip (indenter) and the exchangeable load mass. This allows the study of the influence of the tip shape and the impact energy on the snow strength parameters in a wide range, extends the scope of application of the durometer and makes possible to determine the strength of snow-ice formations by indenters with various geometrical parameters depending on climatic conditions.

Signal feature extraction based on cascaded multi-stable stochastic resonance denoising and EMD method

On the basis of cascaded multi-stable stochastic resonance system (CMSRS) theoretical studies, for the empirical mode decomposition (EMD) in heavy noisy mixtures, a method of EMD based on CMSRS denoising is presented. First, CMSRS is employed as the pretreatment to remove noise by virtue of its good effect in denoising performance, and the energy gradually is shifted from high to low frequency, then the denoised signal is decomposed by EMD. In simulated experiment, EMD is used to decompose the original and CMSRS output signals respectively. The result from the comparison shows that this method, not only removes high-frequency noise efficiently, but also reduces the decomposition layers and lets them have more reality meanings. At last, a diagnosis on the fault of inner race of rolling bearing confirms that this method removes high-frequency noise step by step, improves low-frequency signal’s energy, and can effectively identify characteristic signals.

The theoretical modeling and experimental validation for distributed defect on inner race of ball bearing under radial load

This article presents the theoretical model to study the vibration characteristics of ball bearing. The vibration analysis is accounted for peripheral motions of rolling elements as well as inner and outer races using the Lagrangian approach. In this mathematical model, the contact between the balls and the bearing races is considered as nonlinear springs, whose stiffness is obtained using the Hertzian elastic contact deformation theory. The nonlinear equations of motions are solved by the Runge–Kutta method iteratively. The effects of extended defect on the inner race of the bearing at different speeds and defect sizes have been studied for predicting the vibration response of the bearing. The fast Fourier transformation shows that the vibration characteristic of the ball bearing changes when the ball interacts with the defect as a result of nonlinear load–deflection relation. The analysis implied that defect size and speed of ball bearing are the influencing parameters affecting the dynamic behavior of the ball bearing.

Heat Treatment and Thermo-Mechanical Treatment to Modify Carbide Banding in AISI 440C Steel: A Case Study

In the present case study, simple heat treatment and thermo-mechanical treatment (TMT) are suggested to salvage AISI 440C steel bars with carbide banding. Optical microscopy, scanning electron microscopy, and hardness measurement were employed to characterize the steel before and after treatments. The experimental results indicate that carbide refinement and uniform distribution of carbides can be achieved by TMT. The hardness of the steel after TMT was higher than 58 HRC in hardened (H1050), cryo-treated (C-80), and tempered (T180) conditions. This TMT cycle was implemented to produce one batch of rings free of carbide banding for outer race of ball bearings.

An Integrated Tribological and Vibration Signal Behaviour of TiN and AlCrN based PVD Coatings for Roller Bearings

Objective: The goal of current work is to check the suitability of Titanium Nitride (TiN) and Aluminium Chromium Nitride (AlCrN) coatings for the outer race of roller bearings. Methods: Physical Vapour Deposition (PVD) method of coating is employed since it provides less coating thickness. Tribological behaviour is studied for wear rate and co-efficient of friction using PIN-ON-DISC machine. Statistical method of Vibration analysis is performed by extracting values such as kurtosis, skewness, crest factor and RMS from time domain signals captured. Findings: It is revealed in the results that wear rate for TiN coated bearing is 0.03mm3 /min which is less than that of AlCrN coated bearing and uncoated bearing. Findings of the vibration study showed that kurtosis value is 7.6 for worn out AlCrN coated bearing compared to 4.4 for worn out TiN coated bearing. This clearly shows that TiN offers better wear resistance which supports the results of wear analysis. It is observed in SEM images of morphological studies that more wear tracks and ploughing marks occurred in uncoated and AlCrN coated bearing surfaces compared to TiN coated bearing. Application/Improvements: Current work provides a good integrated approach for tribological and vibration signal behavior of TiN and AlCrN based PVD coatings thus improving correlation between the two methods and it can be prolonged for prognosis. Keywords: Kurtosis, Physical Vapor Deposition, Tribology, Time Domain Signal, Wear Rate

Experimental Investigation for Distributed Defects in Ball Bearing Using Vibration Signature Analysis

Bearing play a pivotal role in rotating machinery. Failure analysis of the bearing is mostly studied by creation of artificial defect on various elements of the bearing and analysis is made with vibration signature tool for monitoring its condition. As localized bearing fault grows, becoming a distributed one, generate random signal with non-stationary components. In present paper effect of surface roughness on the vibration response of outer race of the ball bearing is analysed. Vibration spectrum produced by the single roughness defect under pure radial load at various locations on outer race of bearing is studied. Effect of roughness size, speed and load on the vibration response has been investigated. Results are presented in time and frequency domain. The experimental results are compared with ball pass frequency of outer race. Frequency response obtained from the experimental results is found identical with the theoretical ball pass frequency of outer race.

Study on Excitation Forces Generated by Defective Races of Rolling Bearing

The vibrations generated by defective rolling elements bearing play vital role in dynamics of rotating machines. In this paper different approach for simulation and numerical analysis of defective bearing races presented by researchers have been compared and extended for multiple defects. This work has been attempted to demonstrate the way of modelling and simulation of local and distributed defect on inner and outer race of deep groove ball bearing. The bearing defect has been modelled as impulse train force or impact force to cause an additional deflection or excitation of rolling elements. The simulated results have been analysed in time and frequency domain. The characteristics defect frequency and its harmonics and amplitude of vibration response of defective bearing is broadly investigated through simulated results.