Journal Bearing Test Research Articles

Expansion of the Metrological Visualization Capability by the Implementation of Acoustic Emission Analysis

The acquisition and evaluation of acoustic emissions (AE) in tribology have proven to be a meaningful tool for condition monitoring and offer possibilities to deepen the understanding of tribological processes. The authors used this technology with the aim of expanding existing test methodologies towards increased visualization capability of tribological processes and investigated the correlation between tribological processes and acoustic emissions on a Ring-on-Disc and a close-to-component journal bearing test setting. The results of this study include the description of friction as well as wear processes and prove the usability of several AE evaluation parameters whereby a close correlation between AE and tribological processes can be shown. Consequently, it was possible to expand the visualization and evaluation capabilities of the test settings offering additional insights by making use of AE.

Tribological Analysis of a Hydrodynamic Journal Bearing under the Influence of Synthetic and Biolubricants

ABSTRACTThis study investigated the tribological characteristics of journal bearings exclusively for automotive applications under the influence of a synthetic lubricant (SAE20W40) and chemically modified rapeseed oil (CMRO) as a biolubricant, dispersed with TiO2, WS2, and CuO nanoparticles used as antiwear additive. The effects of synthetic and nanobased biolubricants on the tribological behavior of the hydrodynamic journal bearing were examined using a journal bearing test rig by measuring the coefficient of friction, oil film thickness, and wear under a load of 10 kN and a speed of 3,000 rpm. The test results show that CuO nanoadditives that are added to the biolubricant exhibit outstanding wear and friction reduction behavior, better than that with synthetic lubricants as well as other nanobased biolubricants. The inclusion of CuO nanoparticles in the biolubricant decreased the coefficient of friction by 27% and wear by about 47% compared to a synthetic lubricant. Additionally, investigations were performed using atomic force microscopy (AFM) and scanning electron microscopy (SEM) to study the surface morphology and surface roughness behavior of the tested bearing surfaces.

Control on wear of journal bearing operating in mixed lubrication regime using grooving arrangements

Purpose The journal bearings subjected to heavy load and slow speed operate in mixed lubrication regime causing contact between the interacting surfaces and resulting in wear. Complexity of wear behavior and lack of unifying theory/model make wear-control very challenging. Design/methodology/approach In the present research work, theoretical and experimental investigations have been conducted to explore the effect of grooving arrangements on the wear behavior of journal bearing operating in mixed lubrication regime. The theoretical model of Hirani (2005) that uses mass conserving cavitation algorithm has been used to determine the bearing eccentricity for different groove arrangements (with varying groove location and extent) for identifying a groove arrangement that minimizes the wear. The wear tests on the grooved bearings were conducted after suitable running-in of the new bearings on a fully automated journal bearing test set-up. A load and speed combination required to operate the bearing in mixed lubrication was used. The performance of different arrangement of bearing was evaluated by measuring their weight loss after the test. Findings Wear was significantly reduced with the use of proper groove arrangement for a bearing operating in mixed lubrication regime. Originality/value The improvement in bearing performance by providing grooves has been the subject matter of several studies in the past, but these studies were confined to the hydrodynamic operative regime of the bearing. In the present work, seven different combinations of axial and radial groove arrangement were tried, which has not been reported in any other work.

Edge loading and running-in wear in dynamically loaded journal bearings

This paper focuses on the beginning phase of hydrodynamic journal bearing life time when the first adaption of the contacting surfaces occurs. Generally, this effect is known as running-in.Experimental data from a journal bearing test rig using a low viscosity 0W20 multi-grade automotive lubricant provide the solid basis for the simulative study of the running-in process. From these measurements and a subsequent determination of the surface roughness, parameters for the mixed lubrication contact model are derived. This analysis combined with the experimentally identified lubricant properties under high pressure and high shear rate enables the evaluation of an iterative simulation approach. In this iterative approach the bearing surface geometry is adapted stepwise until a steady state of operation is achieved.Results show worn regions at the edge of the highly loaded bearing shell. This wear is caused by metal–metal contact due to the elastic bending of the shaft. The calculated wear depth at the edge and the expansion of the worn area in axial and circumferential direction matches the measured profile. This agreement indicates that the simple iterative approach using the Greenwood and Tripp contact model and Archard׳s wear equation is suitable to predict the worn surface geometry after the running-in process is completed.Furthermore, the simulation shows that the maximum asperity contact pressure in mixed lubrication decreases with the stepwise adaption of the surface geometry, until only an insignificant metal–metal contact remains. With this adapted surface geometry, the influence of shaft speed, temperature and surface roughness is also discussed.

Non-Newtonian and running-in wear effects in journal bearings operating under mixed lubrication

For the study of mixed lubrication in dynamically loaded journal bearings, this paper employs a combined experimental and simulative approach. Extensive measurements on a journal bearing test rig with a low-viscosity 0W20 multi-grade lubricant with a strong Non-Newtonian behaviour provide the basis for the investigation of the lubrication conditions in journal bearings. In this paper, temperature effects and the influence of running-in (breaking-in) wear are investigated. To this task, a high dynamic load is applied to the journal bearing under test. To vary the lubrication conditions, only the journal speed is changed. To investigate the lubrication conditions a detailed and validated simulation approach is utilized that takes into account both the piezoviscous effect and the non-Newtonian behaviour of the investigated lubricant as well is able to describe metal–metal contact. With this combined approach the run-in process of the journal bearing under test can be investigated as well as the role of temperature settling effects.

Effects of the Ultra-Dispersed Nano-Diamond Additive on the Grease Boundary Lubrication Performance in the Reciprocating Journal Bearing Test

This study analyzes the tribological performance of the test results of the journal bearing wear tester designed for the simulation of the toggle pin motion in the plastics injection molding machine. Grease with or without the addition of ultra-dispersed nanodiamond (UDD) particles were all tested in the durability tests. It showed that the grease with UDD additive could effectively extend the life of grease more than twice as long as the grease life without UDD additive in the reciprocating heavy-load and low-speed journal bearing tests.

Experimental Investigation of twin Groove Hydrodynamic Journal bearing with different Hydraulic Oils (15W40, 20W40, Refined Oil)

This paper presents an experimental study of pressure distribution on hydrodynamic journal bearing with twin groove (5mm) using SAE 15W40, 20W40 and refined oil. In this study the pressure behavior of different lubricant with twin groove hydrodynamic journal bearing has been investigated. Twin Groove Hydrodynamic Journal bearing test rig (TGHJBTR) is used to test the 70 mm diameter and 100 mm long bearing (l/d = 1) made of Brass. Test bearing is loaded mechanically. The space between the shaft and the bearing is filled with oil. Pressure distribution circumferentially investigation has been carried out applying one unloading and three loading conditions, with operating at journal rotational speed of 1120 rpm. The pressure distributions are validated with the experimental results of Desai and Patel [1].The agreement observed between present work and experimental published data is acceptable. The analysis shows that present data deviates 10 - 15% from available publication.

On the Correlation Between Mechanical Degradation of Lubricating Grease and Entropy

Irreversible thermodynamic theory is employed to study the mechanical degradation of lubricating grease undergoing shearing action. A correlation between the mechanical degradation of grease and entropy generation is established, and the results are verified experimentally using a rheometer, a journal bearing test rig, and a modified grease worker machine. It is shown that the degradation rate is linearly related to the entropy generation and that it can be used for estimation of the mechanically degraded grease life.

Effect of cylindricity on the tribological performance of heavily loaded slow-speed journal bearing

Theoretical and experimental studies have been conducted to analyze the effect of cylindricity on performance of a heavily loaded slow-speed journal bearing. The design of experiments has been employed to quantify the effect of bearing clearance and cylindricity on the wear. Since the initial experimental results did not establish any definitive trend, the effect of running-in was considered and the sliding distance required for reaching steady wear was estimated by conducting tests on lubricity tester employing conformal block and disc configuration. Further experiments incorporating the running-in were then conducted on journal bearing test rig. The wear coefficient was determined using the steady wear data obtained experimentally on the lubricity tester. A mathematical model was formulated to estimate wear of the bearing incorporating the actual cylindricity. The theoretical and experimental results corresponded well indicating a strong dependence of wear on the bearing cylindricity at the contact zone.

Impact of high pressure and shear thinning on journal bearing friction

For the study of mixed lubrication in journal bearings, this paper employs a combined experimental and simulative approach. Extensive measurements on a journal bearing test rig with a low viscosity 0W20 multi-grade lubricant provide a solid basis which is complemented by experimental lubricant data that is measured under high pressure and high shear rates. In this paper, this data is used to investigate the impact of the piezoviscous effect and the non-Newtonian lubricant properties on the friction power losses in journal bearings over a wide range of dynamic loads and shaft speeds.In particular, this work seeks to predict the friction power losses for journal bearings under both moderate (50MPa peak load) and high dynamic loads (100MPa peak load) using the recently presented accurate numerical method (Allmaier et al., 2011 [1], Allmaier et al., 2013 [2]). From the direct comparison to the experimental data a key finding is that the simulation conforms very closely to the measured data. To be more exact, the agreement lies within the measurement uncertainty.Following this result, the influence of the often neglected piezoviscous effect and the non-Newtonian lubricant rheology is investigated. We conclude that both the piezoviscous effect and the non-Newtonian behaviour are essential to describe the lubrication with multi-grade lubricants in journal bearings. Only the consideration of both properties describes the experimental data very accurately over the entire range of operating conditions studied.

Experimental Investigation on Hydrodynamic Journal Bearing using SAE 10W30 Multi Grade Oil

This paper presents an experimental study of pressure distribution on hydrodynamic journal bearing with SAE 10W30 multi grade oil. Hydrodynamic Journal bearing test rig (HJBTR) is used to test the 40 mm diameter and 40 mm long bearing (l/d = 1) made of Bronze. Test bearing is located between two antifriction bearings and loaded mechanically. The space between the shaft and the bearing is filled with SAE 10W30. A constant load of 800 N is applied at various journal rotational speeds of 1000, 1500, 2000 rpm. Various parameters like frictional torque, oil temperature and pressure at 10 different sensors along circumferential direction were recorded from Hydrodynamic Journal Bearing Test Rig (HJBTR). These results were used for experimental calculations and theoretical verification using Raimondi and Boyd charts for practical design. The experimental plot of pressure ratio vs sommerfeld number indicates that the working conditions are in the stable hydrodynamic regime. Also experimental results were following the same trend as MCKEE‟s investigation curve.

Effect of shaft roughness and pressure on friction of polymer bearings in water

In this study, the frictional behavior of selected commercially available unfilled polymers, namely, polyether ether ketone, polytetrafluoroethylene, polyethylene terephthalate, and ultra-high molecular weight polyethylene against an Inconel shaft was investigated using a journal bearing test configuration in water-lubricated sliding contact. Dynamic friction curves were obtained for various shaft roughness values and polymer combinations. The results showed a significant influence of shaft surface roughness on running-in and steady state friction in water-lubricated conditions. Contact angle measurements revealed a significant increase in wettability of Inconel counterfaces. The X-ray photoelectron spectroscopy (XPS) analysis of the surfaces suggests formation of a reaction layer on worn Inconel surfaces when sliding against the polymers. The influences of counter surface roughness and load on frictional response of polymers were studied through intermittent tests by obtaining dynamic and breakaway friction maps for different polymer materials, shaft roughness values, and pressure combinations. In general, a trend of decreasing friction was obtained with increasing contact pressure; however, the materials’ frictional responses to variations in counter surface roughness were different. These results indicate that although a reduced counter surface roughness may be beneficial for dynamic friction of polymers in all lubrication regimes, it can adversely affect the materials’ breakaway friction response.

Extending performance limits of turbine oils

New turbine oils providing both extremely high viscosity index (VI) and improved boundary/mixed lubrication performance are investigated. Comparisons are made in both laboratory scale testing using typical journal bearing sliding surfaces (steel and white metal) and full scale testing using a hydrodynamic journal bearing test machine. The results from these studies demonstrate the effectiveness of new, high VI, turbine oils for reducing friction at machine startup and improving performance during full film operation.

The Effects of Oil Supply Pressure at Different Groove Position on Frictional Force and Torque in Journal Bearing Lubrication

An axial groove is a common supply method for distributing lubricant within a journal bearing. Lubricant is generally fed at a specific supply pressure to ensure that the journal and the bearing surface are separated. Shearing action between lubricant and bearing parts creates friction which contributes to power loss in the bearing. In this study, experimental work was conducted to determine the effect of oil supply pressure at different oil groove positions on torque and frictional force in hydrodynamic journal bearing. The journal bearing test rig with a journal diameter of 100mm and a length-to-diameter ratio of ½ was used. The oil supply pressure was set at 0.2, 0.5 and 0.7MPa. The groove was positioned at 7 different locations of -450, -300, -150, 00, +150, +300 and +450. Measurements of frictional force, torque and friction coefficient were obtained for speed values of 500 and 800rpm at 10 and 15kN radial loads. It was found that oil supply pressure and groove positions had affected the frictional force and torque in journal bearing.

Determination of tribological properties at CuSn10 alloy journal bearings by experimental and means of artificial neural networks method

PurposeIt is important to know the friction coefficient and wear loss for determination of tribological conditions at journal bearings. Tribological events that influence wear and its variations affect experimental results. The purpose of this paper is to determine friction coefficient and wear loss at CuSn10 alloy radial bearings by a new approach. In experiments, effects of bearings have been examined at dry and lubricated conditions and at different loads and velocities.Design/methodology/approachIn this study, friction coefficient and wear losses of journal and bearing have been determined by a new approach with a radial journal bearing test rig and artificial neural networks (ANNs) method. The ANN typifies a learning technique that enables the hidden input‐output relationship to be mapped accurately. Bronze‐based materials have been used as bearing material. Effects of friction coefficient and wear losses have been examined at same load and velocity and at dry and lubricated conditions.FindingsThe results obtained in ANN application are close to friction test results for dry and lubricated conditions. Therefore, by using trained ANN values, the intermediate results that were not obtained in the tests can be calculated. Experimental studies will be increased and research with ANN will be continued.Originality/valueBy using trained ANN values, the intermediate results that were not obtained in the tests can be calculated. The training finished on 30 min whereas experimental study had continued day after day.

Predicting friction reliably and accurately in journal bearings – The importance of extensive oil-models

Within the framework of an attempt to predict friction in journal bearings reliably and accurately, the impact of neglecting the hydrodynamic pressure dependence of the lubricant in the oil-model employed in the simulation is investigated. To this task calculations are carried out with two different oil-models; namely, an extensive oil-model that includes the influence of the hydrodynamic pressure on the lubricant properties, as well as the still commonly used basic oil-model that neglects this dependence. To cover full film lubrication and mixed lubrication with significant metal–metal contact, two different lubricants (SAE40, SAE10) are studied.Calculations are conducted using a validated simulation model for dynamic loads with a maximum of up to 76MPa that exceed typical main bearing loads found in current automotive ICEs. The results for both oil-models are compared to measurements performed on a journal bearing test rig.We find that the results obtained with both oil-models agree closely with the experimental values only for full film lubrication, while solely the extensive oil-model is able to give also reliable results for the case of mixed lubrication.

Experimental Investigation of Oil Film Thickness for Hydrodynamic Journal Bearings

Journal bearings are widely applied in different rotating machineries. These bearings allow for transmission of large loads at mean speed of rotation. These bearings are susceptible to large amplitude lateral vibration due to self-exited instability which is known as oil whirl or synchronous whirl. This oil whirl depends on many parameters such as oil film thickness, viscosity of lubricant, load on bearing, inertia of fluid etc. out of which oil film thickness plays an important role in operation of Journal bearings. As oil film thickness decreases metal to metal contact occurs this further can damage the journal bearing. So during the operation minimum oil film thickness should be maintained which can avoid the metal to metal contact and further increases the life of bearing. This paper presents a theoretical calculation of oil film thickness and experimental verification of same on journal bearing test rig. Different journal speeds and loads are considered for the analysis.

An experimental investigation on frictional behavior of statically loaded micro-grooved journal bearing

Performances of plain and micro-grooved engine journal bearings were investigated in this study. Numerous experiments were performed under different static loads by using the purpose-built journal bearing test rig. Micro-grooves were made by cutting micro-channels both around and across the engine journal bearing surfaces. Stribeck curves for the micro-grooved and the plain journal bearings were then experimentally and theoretically generated while frictional torque versus angular velocity curves were also plotted. The results showed that the highest value of coefficient of friction as well as the frictional torque was obtained on the transversal micro-grooved journal bearings.

Tribological failure analysis of journal bearings used in sugar mills

In present paper the premature failure of journal bearings encountered in sugar mills has been analyzed. The causes of bearing failure are identified by simulating the operating conditions and conducting controlled experiments on a fully automated Journal Bearing Test Rig with provisions for varied combination (i.e. load, speed, and lubricating oil) of operating conditions. The results of performance behavior (i.e. coefficient of friction, change in surface roughness and weight loss) of the bearings as observed in these experiments have been reported. The theoretical and experimental results indicate the existence of boundary lubrication conditions in sugar mill journal bearings. To mitigate the problem of relatively high wear, lubricating oil with boundary additives have been tried and results are reported.

Predicting friction reliably and accurately in journal bearings—A systematic validation of simulation results with experimental measurements

It is the aim of this work to predict friction in journal bearings reliably and accurately under realistic dynamic working conditions. To this purpose elastohydrodynamic (EHD) calculations using an extensive oil-model and including an approach to the conformal roughnesses of the bearing surfaces are carried out for transient loads typical for current utility vehicles (40 MPa) as well as for considerably higher specific loads (70 MPa) and for different lubricants (SAE10, SAE20, SAE30 and SAE40) to account for a large span of working conditions ranging from full film lubrication to mixed lubrication with metal–metal contact. The results obtained from this simulation model are compared to measurements performed on a journal bearing test rig. We find that the results of the presented approach agree very closely with the experimental values. The presented approach allows consequently to investigate the effectiveness of changes in bearing geometry, bearing materials, bearing surface roughness, lubricant viscosity and engine operating conditions to reduce friction in journal bearings.