Cylindrical Roller Research Articles

Effect of compound pit textures on the friction and wear of thrust cylindrical roller bearings under starved lubrication

PurposeThis study aims to investigate the effect of compound pit textures on the tribological properties of thrust cylindrical roller bearings (TCRBs) using several parameters, such as compound type, pit diameter, pit depth and pit area density.Design/methodology/approachThe surface texture parameters of the shaft washer (WS) raceway include pit diameter (D; 100, 300 and 500 µm), pit depth (H; 10 and 20 µm) and pit area density (S; 10%, 13% and 18%). Pits were produced on the WS of the TCRBs using laser marking equipment. The friction and wear performances of compound pit-textured TCRBs under starved lubrication conditions are studied using a friction and wear test rig. The influence mechanisms of the compound pit texture on the friction and wear properties of TCRBs are discussed through real tests and discussions.FindingsCompared with nontextured bearings, the average coefficient of friction (ACOFs) and wear loss of TCRBs with single/compound pit textures are reduced when rotating under starved lubrication. D has the greatest effect on the COFs curve. When D = 300 µm, H = 10 µm and S = 10%, the ACOF and wear loss are the lowest, that is, 0.0207 and 3.38 mg, respectively. Under the same lubrication conditions, compared with the nontextured bearing group, the COF and wear loss are reduced by 41.4 and 59.6%, respectively.Originality/valueThis study provides a useful reference for the raceways of textured TCRBs.

Study of the Plastic Behavior of Rough Bearing Surfaces Using a Half-Space Contact Model and the Fatigue Life Estimation According to the Fatemi–Socie Model

A multiscale approach for the fatigue life estimation of rolling bearings is presented in this paper and applied to inner rings of cylindrical roller bearings of the type NU208. The forces acting in the rolling contact are determined from system-oriented modeling at the macro level. The microscale contact simulations are carried out in a half-space contact model. The stresses on the inner ring are determined and used in the local fatigue approach, according to Fatemi–Socie, for fatigue life estimation. Four surface variants were investigated, one ideally smooth surface and three real (rough) surfaces. The three rough surface variants used different finishing processes: fine ground, hard turned, and rough ground were produced. A load case with a maximum pressure of 2.4 GPa in the roller-inner ring contact was investigated. In addition to the fatigue life estimation, the plasticity behavior (surface topography, resulting contact pressure, and residual stress) of the three manufactured surfaces stood in the focus of the work. As the comparison between experimental and simulated results confirms, good predictions can be made with the simulation model.

Influence of Tribolayer on Rolling Bearing Fatigue Performed on an FE8 Test Rig—A Follow-up

The tribological contact between raceways and rolling elements is essential for rolling bearing performance and lifetime. The geometrical description of these contacts is well known and can be used in several mechanical simulation tools. The material description, especially of the near-surface volume after interaction with lubricants, is not as simple. In particular, the Schaeffler FE8-25 test with cylindrical roller thrust bearings exhibits different failure modes depending on the lubricant chemistry. The main failure mechanisms of this test are sub-surface fatigue damage due to WECs (White Etching Cracks) and/or surface-induced fatigue damage (SIF). The harsh test conditions with mixed friction at high speeds and multiple slip conditions over the raceway width additionally provides different tribological conditions on a small area. This leads finally to the formation of certain tribological layers on the raceway because of the interaction of the surface with the lubricant chemistry under local frictional energies, which are worth investigating. The characterization of the layers was performed by the two less time-consuming, spatially resolved analysis methods of µXRF and ATR FTIR microscopy adapted by Schaeffler. This paper shows the results of this research and offers new approaches to optimizing rolling bearing testing and predicting the risk of early failures.

Developing a Novel Growth Method for Carbon-Infiltrated Carbon Nanotubes on Ti6Al4V

Carbon-infiltrated carbon nanotubes (CICNT) are cylindrical rolls of pure carbon atoms with a honeycomb molecular structure. They have specific applications in medical implants due to their biofilm resistance properties. CICNT can be grown on a variety of material substrates such as silicon, stainless steel, and pure titanium. Different substrates require different CICNT growth processes. This study developed a growth method for CICNT on Ti6Al4V, a titanium alloy commonly used as a medical implant material due to its strong mechanical properties and excellent biocompatibility. However, due to the presence of vanadium in the alloy, it is difficult to use it as a substrate for CICNT growth. To solve this problem, this study used an indirect growth method, which placed a barrier layer of alumina (Al2O3) between the Ti6Al4V and an iron growth catalyst layer. A control group was also created without an alumina barrier layer. This study additionally investigated the differences between two deposition methods: electron-beam physical vapor deposition (PVD) and atomic layer deposition (ALD). After CICNT growth, the samples showed that the deposition of the barrier layer allowed the growth of CICNT on Ti6Al4V. Using a scanning electron microscope (SEM), the results also showed that at the levels of alumina studied, the deposition method did not make a difference to CICNT coverage of the Ti6Al4V. These results illustrate the fact that Ti6Al4V can be used as a substrate for CICNT if a barrier layer is used.

Reduction of wind turbine gearbox damage risk due to electrical faults via component design optimization

Over the lifetime of a wind turbine (WT) it is likely that several electrical faults occur. Electrical faults may induce significant electromagnetic generator torque excitations. The torque excitations are transferred to the gearbox components and lead to dynamic load changes as well as changes in the speed of rotation. Dynamic load changes in combination with changing rotational speeds might lead to gearbox component damage. Gearbox component damage is the main driver for WT downtime due to the high time to repair the fault. Especially the components of the high-speed stage (HSS) are prone to failure. This paper presents a method for introducing gearbox component design optimizations in order to reduce the damage risk during electrical faults. Via profile shift the HSS safety against scuffing cannot be further increased compared to the reference. The HSS safety against micropitting can be increased via profile shift by max. 41% and the safety against tooth flank fracture on the HSS by max. 3% compared to the reference. Via profile modification the HSS safety against scuffing can be increased by max. 14%, the HSS safety against micropitting by max. 8% and the safety against tooth flank fracture on the HSS by max. 8% compared to the reference. Via roller profile optimization the smearing risk on the HSS cylindrical roller bearing can be reduced by max. 3% compared to the reference. Thus, on the basis of two exemplarily analyzed electrical faults, this paper shows that gearbox component design optimizations can significantly reduce the gearbox damage risk during electrical faults.

Mixed Lubrication Analysis of Tapered Roller Bearings and Crowning Profile Optimization Based on Numerical Running-In Method

Tapered roller bearings (TRBs) are widely used in heavy-load rotating machinery. One of the technical problems in TRBs is the existence of sharp spikes of the contact pressure in the vicinity of the two ends of the tapered rollers. To suppress the pressure spikes at the roller ends, a straight roller profile is crowned in cylindrical and tapered roller bearings. However, compared to cylindrical roller bearings, there are few studies on the profile modification of TRBs in the literature, and most of the publications on the EHD analysis of tapered rollers focused on a single roller, using traditional profiles such as logarithmic profiles, dub-off profiles and chamfer profiles. By using the numerical running-in method proposed and used in crowning profiles of cylindrical rollers by the authors, this paper provides the first ever asymmetric optimized profile solution for all TRBs rather than for just a single roller. The results show that the optimized profile has the best performance in smoothing contact pressure distribution in the axial direction compared with the conventional logarithmic profile and is a useful profile form with respect to the elimination of sharp pressure spikes. In addition, considering the effect of temperature and mixed lubrication, this paper analyzes the influences of different axial profiles under radial load (Fr), rotation speed (N) and standard deviation of roughness (Rq) conditions.

Evolution of Mechanical Properties of an AA 6061 T6 Aluminum alloy Processed by Cold Working (CW)

Nano scale grain size reduction (UFG) is one of three suitable methods for improving the mechanical properties of 6000 series aluminum alloys, by structural precipitation, strain hardening or by cold work hardening. For the cold working, several techniques are now available such as (ECAP - PC), (CEEA), (THP), (MM), (ARB), (CW). Cold work by compression high pressing (CW-CHP) can be applied in several cycles depending on the hardening behavior of the material. The influence of the nonmetric size of the grains produced by the (CW-CHP) of a cylindrical rolling machine with four passes of Sever plastic deformation with reduction ratios of (3.5, 10,18.8 and 28%), on the mechanical behavior of the alloy 6061 T6, was analyzed by determining the ultimate tensile strength (Rm), yield strength (Rp0.2, the strain hardening capacity SHC (Rm-Rp0.2), the work hardening coefficient n', the modulus of 'work hardening K' . The increase in the rate of work hardening by the reduction of the sample sections and consequently the reduction of the grain size at the first and the second pass, improves the mechanical properties of the alloy to the maximum values, and then the presence of crack initiation participates to the moderate decrease of the mechanical properties.

Crowbar Loading-A New Test Technique to Characterize Interfacial Delamination

This paper presents a new test method called Crowbar Loading (CBL) to characterize interfaces between dissimilar materials. In this test, a cylindrical roller is sandwiched in the delaminating interfaces and acts as a fulcrum to facilitate crack propagation. Although the externally applied load is compressive on one side of the fulcrum, the fulcrum translates the applied external load into an opening-mode load at the crack tip. By varying the location of the roller, this work shows that a wide range of loads can be altered at the loading point. Numerical models were developed to determine the critical crack length from the experimentally measured compliance of the test sample and, thus to determine the critical strain energy release rate (Gc). The crack length, determined using compliance, is also validated through optical measurements. Copper-epoxy mold compound (Cu/EMC) bimaterial samples, commonly seen in microelectronic packages, were successfully characterized using the developed CBL test method. The results from the CBL test have been compared against the double-cantilever beam (DCB) test results.

Finite Amplitude Oscillatory Convection of Binary Mixture Kept in a Porous Medium

In the present study, the double-diffusive oscillatory convection of binary mixture, 3He–4He, in porous medium heated from below and cooled from above was investigated with stress-free boundary conditions. The Darcy model was employed in the governing system of perturbed equations. An attempt was made, for the first time, to solve these equations by using the nonlinear analysis-based truncated Fourier series. The influence of the Rayleigh number (R), the separation ratio (ψ) due to the Soret effect, the Lewis number (Le), and the porosity number (χ) on the field variables were investigated using the finite amplitudes. From the linear stability analysis, expressions for the parameters, namely, R and wavenumbers, were obtained, corresponding to the bifurcations such as pitchfork bifurcation, Hopf bifurcation, Takens–Bogdnanov bifurcation and co-dimension two bifurcation. The results reveal that the local Nusselt number (NL) increases with R. The total energy is enhanced for all increasing values of R. The deformation in the basic cylindrical rolls and the flow rate are enhanced with R. The trajectory of heat flow was studied using the heatlines concept. The influence of R on the flow topology is depicted graphically. It is observed that the intensity of heat transfer and the local entropy generation are increased as R increases.

Finite Element Analysis of Damage of Cylindrical Roller Bearing of Main Shaft of Shot Blasting Machine

The main shaft of shot blasting machine mainly uses cylindrical roller bearing as the supporting part. The influence of stress, strain and temperature on bearing damage was studied by thermal structural coupling analysis of the bearing through finite element simulation. The causes and main damage forms of bearing surface were verified by super depth of field observation and finite element analysis. It is found that there exists pyramidal strain in the contact area between inner and outer raceway and roller, and its distribution form is continuous point distribution. The stress concentration is mainly distributed in the contact area between the roller face and the retaining edge, and the roller temperature is more concentrated in the area near the end face. The maximum length and depth of spalling pit on racetrack surface were 572.2μm and 14.15μm respectively. The maximum width and depth of the scratches on the roller surface are 386.7μm and 10.7μm, and the damage degree of the roller surface is not uniform. The thermo-structural coupling analysis is used to simulate the running state of bearings, which is of guiding significance to analyze the failure forms of bearings and improve the service life of bearings.

Mathematical modeling on a novel manufacturing method for roller-gear cams using a whirl-machining process

The whirl-machining process is a precise, efficient, and promising machine process for manufacturing workpieces over the milling process. At the same time, the roller-gear cam has advantages over the other cam-follower system. However, the whirl-machining process has not been applied to manufacture the roller-gear cam. Therefore, this paper proposes a novel method for roller-gear cam manufacturing using a whirl-machining process. Mathematical modeling is described for generating the roller-gear cam, roller, and whirl-milling tool surface. A novel CNC machine and its coordinate system are proposed. Cutting simulations for obtaining the surface topologies and normal deviations are conducted. Globoidal cam with different cylindrical rollers, globoidal cam with a conical roller, and cylindrical cam with a conical roller are taken as case studies, and results are discussed. A virtual cutting simulation was conducted using VERICUT. Some machining examples are shown to verify the benefits of the proposed method in roller-gear cam manufacturing.

An improved method for film thickness measurement of cylindrical roller bearings based on a straight-beam probe

PurposeConsidering the industrial site environment and installation requirements, the straight-beam ultrasound probe with easy installation and good coupling agent adaptability is adopted to replace the traditional water immersion focusing probe for film thickness measurement in cylindrical roller bearings. The straight-beam probe has a large echo receiving range, which will result in measurement regions overlapping and bring about large measurement errors. In this paper, an improved measurement method for film thickness of cylindrical roller bearing with the straight-beam probe is developed.Design/methodology/approachAn improved method is proposed to enhance the spatial resolution of the straight-beam probe. By introducing a correction coefficient based on the percentage of the effective measurement area, the method improves the measuring accuracy successfully.FindingsThe experimental results demonstrate that the lubricant-film thickness can be measured to reasonable accuracy by this method and have a better agreement with the theoretical film thickness solutions.Originality/valueThis paper used analytical method and model that is helpful for the improvement of the spatial resolution, which has great influence on the measuring accuracy, is mainly determined by the echo reflection area size of the ultrasound transducer.

CFCNN: A novel convolutional fusion framework for collaborative fault identification of rotating machinery

Sensor techniques and emerging CNN models have greatly facilitated the development of collaborative fault diagnosis. Existing CNN models apply different fusion schemes to achieve reliable fault identification based on multisensor data. Few CNN models, however, take into account both the intrinsic correlations and the distribution gap between different signals, which may result in a limited exploration of multisource data. To address this issue, a novel convolutional fusion framework called a collaborative fusion convolutional neural network (CFCNN) is developed in this paper. More specifically, a multiscale shrinkage denoising module (MSDM) is developed first to extract multilevel modality-specific features from different mechanical signals. Then, drawing inspiration from the intermediate fusion scheme, a central fusion module (CFM) is introduced to explore the intrinsic correlations and integrate cross-modal features. Moreover, an online label smoothing training (OLST) strategy is applied to reduce overfitting and promote better classification performance of CFCNN. The developed CFCNN is expected to shed new light on collaborative fault diagnosis using the intermediate fusion scheme. The efficacy of the developed CFCNN is verified through the cylindrical rolling bearing dataset and the planetary gearbox dataset.

In Search of Smooth Motion

When smoothness is a major requirement of linear motion, IKO can offer a specific range of high-performance products. Arrangements including ball bearings and cylindrical rollers enable this product group to handle a wide range of operating conditions, including high rigidity and precise, repeatable motion

Investigation of Roller Bearing Cage Pocket Lubrication and Friction

Abstract A test rig was designed and developed to assess the lubrication and friction of a single cylindrical roller and a conformal cage pocket. The roller was lubricated via oil bath in a sealed housing. Inner and outer bearing raceway pieces were fixed above and below the roller to mimic the internal geometry of an actual bearing. The cage pocket was made from transparent acrylic to look inside the cage and observe oil flow during operation. A six-axis load cell was used to measure the torque generated by the entire test rig with and without the cage pocket and used to isolate the friction of the cage pocket. Experiments were conducted to investigate the effects of roller–pocket clearance, roller–raceway clearance, and roller oil submersion level at rest. Results suggest that roller bearing cage pocket friction increases with decreasing pocket clearance, increasing oil availability, and increasing operating speed. The oil was observed to coalesce into stable striations inside the cage pocket for many operating conditions. Striation width was observed to decrease with increasing speed, increasing pocket clearance, and decreasing oil availability. The striations were summarized by oil volume fraction inside the cage pocket, which decreased with increasing speed, decreasing pocket clearance, and decreasing oil availability. The current results provide new information about oil behavior inside roller bearing cage pockets during operation, and an approach is presented to estimate roller bearing cage pocket friction.

Analysis of motion and vibration characteristics of elastic composite cylindrical roller bearing

To investigate the motion characteristics and vibration characteristics of elastic composite cylindrical roller bearings (ECCRBs), a simulation model of the ECCRB is established in ABAQUS software. The influences of filling degrees and working conditions on motion characteristics of the ECCRB are compared, and the modal characteristics and harmonic response of the ECCRB are analyzed. Calculation results show that when the filling degree increases from 0% to 60%, there is a nonlinear relationship between the filling degree and the slip rate of cage, the natural frequency of each order decreases, and the vibration displacement of ECCRB increases under the excitation load; increasing the rotation speed and decreasing the radial load reasonably is beneficial to the motion stability of the ECCRB. At the same time, with the increase of the excitation load, the vibration displacement of the ECCRB increases. The analysis results can present some theoretical basis for the structural optimization of the ECCRB.

Micro-geometry deviation to reduce the cage slip of high-speed cylindrical roller bearings

Micro-geometry deviation to reduce the cage slip of high-speed cylindrical roller bearings

A combined experimental and analytical method to determine the EHL friction force distribution between rollers and outer raceway in a cylindrical roller bearing

Friction force is a crucial factor causing power loss and fatigue spalling of rolling element bearings. A combined experimental and analytical method is proposed to quantitatively determine the elastohydrodynamic lubrication (EHL) friction force distribution between rollers and outer raceway in a cylindrical roller bearing (CRB). An experimental system with the instrumented bearing and housing was developed for measuring radial load distribution and friction torque of bearings. A simplified model of friction force expressed by dimensionless speed, load, and material parameters was given. An inequality constrained optimization problem was established and solved by using an experimental data-driven learning algorithm for determining the uncertain parameters in the model. The effect of speed, load, and lubricant property on friction force and friction coefficient was discussed.

Method for determining the forces acting on a axle box designed for the installation of an adapter bearing

The installation of adapter bearings (cassette type) provides new opportunities to achieve longer maintenance intervals and to improve performance and safety. In the developed methodologies for calculating the forces acting on a axle box unit in European and state standards, dependencies are defined for axle boxes with short cylindrical rollers and conical or cassette type bearings where the transmission of the vertical load between the axle box and the bearings is on a cylindrical surface. In the contact area of a segment, in addition to the standard static, dynamic, centrifugal and inertial forces of the axle box, additional forces also act. Overloading occurs when the axle box has become detached from the bearing by lifting off of it. Under these conditions, the transmission of forces between the axle box and the bearing takes place not through the normal tight contact along a segment of 120º, but through the edge of the axle box shell. In this publication, a method is proposed for determining the forces in an axle box designed for the installation of an adapter bearing.

Handling Complex Loads

Bearings using cylindrical rolling elements, such as IKO's range of standard needle roller bearings, ensure smooth rotation around the load axis, when loaded properly. These bearings are widely used in the rotating parts of industrial robots, machine tools, medical equipment, etc. which require compactness, high rigidity, and high rotational accuracy