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Purpose The purpose of this paper is to solve the problem of joint bearings that cannot work in high temperature because of their high frictional coefficients.Design/methodology/approach Two methods of inlaying graphites and liquid spraying of MoS2 are designed. The arrangement of graphites is shown and its frictional coefficients (COFs) are discussed. MoS2 coating is deposited by liquid spraying. The ingredients of liquid spraying of MoS2 are illustrated. Stresses, structure deformations and fatigue life are analyzed by finite element analysis.Findings Results show that both two designed methods can decrease COFs effectively. All stresses are in the limit of the maximum permissible stresses. The new designed bearings can be safety worked in sealed and high temperature environment which are proved by fatigue analyses.Practical implications Two new designs can help joint bearings work in nuclear plants because of their low COFs and litter wear. The new designs can improve bearings life.Originality/value Two methods of decreasing COFs of joint bearings are designed in this paper. The technologies are illustrated. The proper scopes of applications of two designed methods are discussed. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this paper is to solve the problem of joint bearings that cannot work in high temperature because of their high frictional coefficients.Design/methodology/approach Two methods of inlaying graphites and liquid spraying of MoS2 are designed. The arrangement of graphites is shown and its frictional coefficients (COFs) are discussed. MoS2 coating is deposited by liquid spraying. The ingredients of liquid spraying of MoS2 are illustrated. Stresses, structure deformations and fatigue life are analyzed by finite element analysis.Findings Results show that both two designed methods can decrease COFs effectively. All stresses are in the limit of the maximum permissible stresses. The new designed bearings can be safety worked in sealed and high temperature environment which are proved by fatigue analyses.Practical implications Two new designs can help joint bearings work in nuclear plants because of their low COFs and litter wear. The new designs can improve bearings life.Originality/value Two methods of decreasing COFs of joint bearings are designed in this paper. The technologies are illustrated. The proper scopes of applications of two designed methods are discussed. [ABSTRACT FROM AUTHOR]

Purpose This paper aims to study the inertia squeeze film characteristics between ferrofluid-lubricated circular stepped disks. Owing to the development of modern machine systems, the application of ferrofluids has received great attention. Because the circular disks are a special situation of circular stepped squeeze films, a further study of fluid inertia force effects on the ferrofluid-lubricated circular stepped squeezing mechanism is motivated.Design/methodology/approach On the basis of the ferrohydrodynamic flow model of Shliomis incorporating the momentum integral method, the effects of fluid inertia forces in ferrofluid-lubricated circular stepped squeeze films in the presence of external magnetic fields are investigated in this study. Analytical solutions of squeeze film performances are derived.Findings The fluid inertia force effects provide an increased load capacity and a longer squeeze film time for the ferrofluid-lubricated circular stepped squeeze film, especially for a larger value of the inertia parameter, the Langevin parameter and the volume concentration and a smaller value of the radius ratio and the step height ratio.Originality/value For engineering applications, numerical tables for squeeze film loads of circular stepped disks are also provided in this paper. [ABSTRACT FROM AUTHOR]

Purpose In the present scenario of high-speed machines, the use of non-circular hole-entry bearing configuration, i.e. two-lobe, multi-lobe, lemon bore, etc., has becomes unavoidable, as the journal bearings with non-circular configurations provide better stability at high operating speed and heavy dynamic loading. Further, this research aims to show that the presence of micro particles in the lubricants greatly affects performance of the bearings, as their presence leads to non-Newtonian behaviors of the lubricant. Therefore, to consider the effect of these micro particles, the lubricant is modeled as a micropolar lubricant. The present work analyzes the effect of these micropolar lubricants on the performance of hole-entry circular and non-circular (two-lobe) hybrid journal bearings compensated with constant flow valve restrictor and compares with that of Newtonian lubricants.Design/methodology/approach The modified Reynolds equation governing the laminar flow of iso-viscous, incompressible micropolar lubricant in the clearance space of a journal bearing system has been solved using finite element method and appropriate boundary conditions. Further, a comparative analysis between circular and non-circular (two-lobe) hybrid journal bearing compensated with constant flow valve restrictor operating with Newtonian and micropolar lubricant has been presented.Findings The numerically simulated results reveal that the non-circular bearing configuration provides better performance vis-à-vis the circular bearing configuration. Further, the increase in the micropolar effect of the lubricant enhances the performance of circular and the non-circular bearing configurations compared with the Newtonian lubricant. Also, in the case of the non-circular bearing configuration with an offset factor (δ = 1.5), the bearing performance improved compared with (δ = 1.25).Originality/value Many research studies have been done in the area of non-circular hybrid journal bearing with Newtonian lubricants with different types of restrictors, but the non-circular hole-entry constant flow valve-compensated hybrid journal bearing operating with the micropolar lubricant has not been analyzed. Therefore, in the present work, an effort has been made to fill this research gap. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Purpose This paper aims to give the guidance for the design of the bearing.Design/methodology/approach The finite element method, the multi-body dynamics method, the finite difference method and the tribology are combined to analyze the lubrication.Findings The performance parameters of crankshaft-bearing system such as the misalignment, the oil filling ratio and the oil groove are also investigated. Misalignment causes the pressure to incline on one side and the pressure increases obviously. Filling ratio has great relationship with pressure distribution; the factors influencing the filling ratio are also analyzed. Different oil groove models are investigated, as it can provide the theory for oil groove design, and three factors above are always combined to influence the lubrication characteristics.Originality/value The optimization of bearing system is conducted by orthogonal test and neural network, unlike the linear optimization theory. Neural network uses the nonlinear theory to optimize crankshaft-bearing system. [ABSTRACT FROM AUTHOR]

Purpose The current trend of modern industry is to use machineries which rotate at high speed along with the capability of carrying heavy rotor loads. This paper aims at static thermal analysis of two different profiles of non-circular journal bearings – a true elliptical bearing and orthogonal bearing.Design/methodology/approach The Reynolds equation has been solved through finite difference method to compute the oil film pressure. Parabolic temperature profile approximation technique has been used to solve the energy equation and thus used for computation of various bearing performance characteristics such as thermo-hydrodynamic oil film pressure, temperature, load capacity, Sommerfeld number and power loss characteristics across the bearing. The effect of ellipticity ratio on the bearing performance characteristics has also been obtained for both the elliptical and vertical offset bearing using three different commercially available grades of oil (Hydrol 32, 68 and 100).Findings It has been observed that the thermo-hydrodynamic pressure and temperature rise of the oil film is less in orthogonal bearing as compared to the true elliptical bearing for same operating conditions. The effect of ellipticity ratio of non-circularity on bearing performance parameters have been observed to be less in case of elliptical bearing as compared to orthogonal bearing. It has been concluded that though the rise in oil film temperature is high for true elliptical bearing, but still it should be preferred over orthogonal profile under study, as it has comparably good load-carrying capacity.Originality/value The performance parametric analysis will help the designers to select such kind of non-circular journal bearing for various applications. [ABSTRACT FROM AUTHOR]

Purpose Water lubrication is significant for its environmental friendliness. Composite journal bearing is liable to deform for the huge pressure of water film. This paper aims to study the influence of elastic deformation on how lubrication functions in water-lubricated journal bearings and to provide references for designing composite journal bearings.Design/methodology/approach The combination of computational fluid dynamics and fluid-structure interaction is adopted in this paper to study the lubrication performance of water-lubricated compliant journal bearings. The influences of elasticity modulus and Poisson’s ratio on load-carrying capacity and elastic deformation are studied for different rotational speeds. Predictions in this work are compared with the published experimental results, and the present work agrees well with the experimental results.Findings A reference whether elastic deformation should be considered for composite journal bearings is proposed under different working conditions. Besides, a reference to determine water-lubricated plain journal bearings dimensions under different loads and rotational speeds is developed with the effect of both elastic deformation and cavitation being accounted.Originality/value The present research provides references as to whether elastic deformation should be considered in operation and to determine compliant journal bearings’ dimensions in the design process. [ABSTRACT FROM AUTHOR]

Purpose – The purpose of this paper is to achieve attractive fabric composites with excellent tribological performance and investigate the wear mechanisms of these fabric composites sliding against bearing steel pins under dry sliding process. Design/methodology/approach – Five different weave density composites were prepared, and the tribological behaviors of these composites were studied at different testing conditions. Scanning electron microscopy, laser microscopy (three-dimensional profile measurements) and energy-dispersive X-ray spectrometry were used to analyze the worn surface morphology, wear volume and elemental content of the transfer films, respectively. Findings – The composite weave density serves an important influence on tribological behavior. Generally, the wear rate of each composite increased with increasing weave density, and the friction coefficient of each composite decreased with increasing weave density. Originality/value – Nanoparticle-filled hybrid polytetrafluoroethylene/Kevlar fabric composites with proper weave density have exhibited superior tribological properties in dry sliding conditions. The results that obtained in this paper may offer a reference for others who intend to achieve attractive fabric composites with excellent tribological performance. [ABSTRACT FROM AUTHOR]

Purpose – The purpose of this study is to investigate the effects of partial texture location and dimple depth on load carrying capacity (LCC), friction coefficient and circumferential flow of journal bearing. Design/methodology/approach – Based on the Navier-Stokes equation, the methodology used computational fluid dynamics (CFD). A phase change boundary condition was applied on fluid domain, and the negative pressure at divergent region of oil film was considered. Findings – It has been found that texture located at lubricant inlet area can improve the performance of the bearing, and the effect of shallow dimples is superior to the deep ones. However, the bearing performance will be reduced due to the texture located at the maximum pressure area. When texture is located at the lubricant outlet area, there will be two different situations: the part of the texture located within the oil film divergent area can improve the LCC, while the part that is beyond the divergent region will make the LCC decrease. Originality/value – The lower-half oil film model was established only in this study to analyze the hydrodynamic lubrication performance of partial textured journal bearing, and the lower-half oil film was divided into three parts. A new cavitation algorithm was introduced to deal with the negative pressure. The formula for calculating the friction of liquid film is refined, including the consideration of vapor phase. The simulation results show that the location of partial texture have a great influence on the bearing performance. [ABSTRACT FROM AUTHOR]

Purpose – This paper aims to use the crankshaft-bearing system of a four-cylinder internal combustion engine as the studying object, and develop a multi-objective optimization design of the crankshaft-bearing. In the current optimization design of engine crankshaft-bearing, only the crankshaft-bearing was considered as the studying object. However, the corresponding relations of major structure dimensions exist between the crankshaft and the crankshaft-bearing in internal combustion engine, and there are the interaction effects between the crankshaft and the crankshaft-bearing during the operation of internal combustion engine. Design/methodology/approach – The crankshaft mass and the total frictional power loss of crankshaft-bearing s are selected as the objective functions in the optimization design of crankshaft-bearing. The Particle Swarm Optimization algorithm based on the idea of decreasing strategy of inertia weight with the exponential type is used in the optimization calculation. Findings – The total frictional power loss of crankshaft-bearing and the crankshaft mass are decreased, respectively, by 26.2 and 5.3 per cent by the multi-objective optimization design of crankshaft-bearing, which are more reasonable than the ones of single-objective optimization design in which only the crankshaft-bearing is considered as the studying object. Originality/value – The crankshaft-bearing system of a four-cylinder internal combustion engine is taken as the studying object, and the multi-objective optimization design of crankshaft-bearing based on the crankshaft-bearing system is developed. The results of this paper are helpful to the design of the crankshaft-bearing for engine. There is universal significance to research the multi-objective optimization design of crankshaft-bearing based on the crankshaft-bearing system. The research method of the multi-objective optimization design of crankshaft-bearing based on the crankshaft-bearing system can be used to the optimization design of the bearing in the shaft-bearing system of ordinary machinery. [ABSTRACT FROM AUTHOR]

Purpose – The purpose of this paper was to construct lubrication model closer to the fact of thrust bearings and to calculate the bearings characteristics of lubrication for understanding how structures influence bearings performances and, importantly, what can be the most beneficial. Large-scale composite thrust bearings with Polytetrafluoroethylene (PTFE)-faced sector pad backed by steel base are used increasingly in equipment. But there are plenty of puzzled problems in design and application. Design/methodology/approach – The authors established a 3D thermal elastohydrodynamic lubrication (TEHL) model. Oil film was formulated by Reynolds equation for pressure, and by energy equation for temperature varying through oil film thickness. Meanwhile, pad temperature was formulated by solid heat transfer equation. Elastic and thermal deformations of pad surface were calculated. Viscosity and density of oil were valued separately under different pressure and temperature. Load balance was considered as well as overturning moment balance. Finite difference method was applied to discrete these equations. Findings – PTFE layer and steel base have either helpful or detrimental impact on contact strength and full film lubrication of thrust bearing depending on their relationship in thickness. Temperature lag between middle layer of steel base and pad surface depends on PTFE layer, but not on the steel base. PTFE layer thickness should be considered when alarming threshold value of the bearings temperature is chosen. Originality/value – Three-dimensional TEHL model of large-scale composite thrust bearings was established, which included more factors close to the actual. Conclusions were drawn. These proposals are helpful to design the bearings. [ABSTRACT FROM AUTHOR]

Purpose – The purpose of this paper is to investigate that if the lubrication system of a helicopter reducer is compromised, its gears and bearings will be at non-lubricating oil work state, which causes the reducer to be damaged in a very short time. Design/methodology/approach – Various 2 per cent additives were injected and mixed with aeronautical oil to produce 45-min oil/mist lubrication and oil/air lubrication experiments performed upon aeronautical steel tribo-pairs. Findings – The results show that the best anti-wear effect is produced by oil/air lubrication that contains 2 per cent T391. It consumes the least quantity of oil and produces the least wear width, the least rise in temperature and the best surface wear quality. Originality/value – The technology of oil/air lubrication that contains an extreme-pressure and anti-wear additive is a feasible way to improve the operational ability of a helicopter transmission system that is out of oil. [ABSTRACT FROM AUTHOR]

Purpose – The purpose of this paper is to find a new logarithmic profile model of cylindrical roller bearing, which is expected to avoid edge effect and allow a straight portion on the roller considering uniform pressure distribution and easier manufacturing. Design/methodology/approach – A new logarithmic cylindrical roller profile model using three parameters is proposed. Contact model between roller and rings and quasi-static model of roller bearing are given to obtain contact pressure distribution and solved by multi-grid and Newton–Raphson method. Optimization of modified reference rating life model of the roller bearing is proposed by using genetic algorithms. Findings – Under heavy load or tilting moment conditions, modified reference rating life of cylindrical roller bearing may increase greatly by optimization of three design parameters using the new logarithmic profile model. Originality/value – The results of the present paper could aid in the design of logarithmic profile of cylindrical roller bearing and increase fatigue life of cylindrical roller bearing. [ABSTRACT FROM AUTHOR]

Purpose – The purpose of this paper was to conceive a fast method to verify design and performance of elliptical pocket journal bearings. Design/methodology/approach – The computer-aided verification of pocket journal bearings is performed by means of a suitable finite element analysis method. Findings – The results of sample analyses indicate that the machining tolerances are very influential on elliptical pocket bearing performances, and they must be included among the input data. Originality/value – Although elliptical pocket bearings are widely used in turbomachineries, the influence of their design on performance has not been specifically investigated. A lot of works about tribological models are available, but few of them focus on their application to bearing design at the industrial level. [ABSTRACT FROM AUTHOR]

Purpose – Water-lubricated rubber bearing is one of the most appropriate bearings for underwater use. The most popular design used widely today is the straight fluted rubber bearing. The special configuration leads to partial hydrodynamic lubrication and low load capacity. A new bearing bush structure with two cavities which is favorable for constructing continuous hydrodynamic lubrication was designed and studied. The paper aims to discuss these issues. Design/methodology/approach – A new bearing bush structure with two cavities which is favorable for constructing continuous hydrodynamic lubrication was designed. The apparatus for studying the tribological behaviors of the two types of water-lubricated rubber bearings has been devised and established in the paper. The experimental studies on the tribological properties of the rubber bearings have been conducted under different loads and velocities. The eccentricity ratio of the new structure rubber bearing with two cavities was measured in experiment and the load capacity was calculated by numerical simulation. Findings – The experimental results show that the friction coefficient decreases with increasing velocity; the friction coefficient increases sharply with the rising temperature, the friction coefficient increases at first and then decreases with increasing load for fluted rubber bearings. The numerical results were in good agreement with the experimental results. The numerical results show that complete hydrodynamic lubrication can be formed in the new designed rubber bearing with two cavities. The experimental and numerical results all indicate that there is an appropriate bearing clearance which the friction coefficient is minimum and the load capacity is maximum. Originality/value – A new bearing bush structure with two cavities which is beneficial to constructing continuous hydrodynamic lubrication film was designed. A new apparatus for studying the tribological behaviors of the two types of water-lubricated rubber bearings has been devised and established. Experimental and numerical study on the new structure rubber bearing were conducted in the paper. [ABSTRACT FROM AUTHOR]

Purpose – A hybrid bearing of advanced cryogenic rocket engine turbopump is designed. For cryogenic fluid propellants (such as liquid oxygen) as the lubrication of bearing, bearings operating close to liquid-vapor region (near the critical point or slightly sub-cooled) are likely to develop a two phase flow region. The paper aims to discuss these issues. Design/methodology/approach – In this paper, an all liquid, liquid-vapor mixture, and all vapor, i.e. a continuous vaporization bulk flow model of density and viscosity for mixture fluid, is presented, and the general Reynolds equation and energy equation with two phase flow as lubricants is solved. The static and dynamic performance of a 50-mm-radius hybrid bearing are obtained under 20,000 rpm speed and 10 MPa supply pressure. Findings – The results show that the variations of performance of bearing operating under cryogenic liquid oxygen are not bounded by the all liquid and all vapor cases in the liquid-vapor mixture range. There behaviours are attributed to the large change in the compressibility character of the flow. Research limitations/implications – For validating the correctness of analytical model, an experimental study on the liquid-vapor nitrogen mixture lubricated hybrid journal bearings is being carried out where low-viscosity nitrogen was selected as the lubricant for the sake of safety. Soon after, the authors will discuss the results and publish them in the new papers. Originality/value – An all liquid, liquid-vapor mixture, and all vapor, i.e. a continuous vaporization bulk flow model of density and viscosity for mixture fluid, is presented. The static and dynamic performance of hybrid bearings with two phase flow as lubricants are obtained. [ABSTRACT FROM AUTHOR]

Purpose – The purpose of this paper is to analyze journal thrust bearings geometries, used in household refrigerators, using a modified version of the Reynolds equation which includes the inertial terms. Design/methodology/approach – The Reynolds equation was solved through the finite volume method, thus providing the pressure field in the lubricant film and, consequently, the load and the power used by the bearing. Such parameters depend on bearing geometry, which was optimized through the method of Lagrange multipliers, to support a given load and use the lowest power possible. The optimized geometries included the Rayleigh pad with 4, 8 and 16 steps, and a milled geometry with 4 steps. Findings – For the Rayleigh pad, the number of steps was varied and a decrease in the power consumed with the increase in the number of steps was observed. The milled pad performance was better than that Rayleigh pad with 4 steps and comparable to the pad with 8 steps. Originality/value – The manufacture of pads, with a high number of steps, is complicated and, then, a milled pad with 4 steps was proposed in this paper. The use of milled pads is a technological innovation worthy of a more thorough investigation, considering its facility of manufacture when compared to the Rayleigh pad. [ABSTRACT FROM AUTHOR]

Purpose – The slot-entry hybrid journal bearings have been successfully used in various engineering applications because of their good performance over wide range of speed and load, besides their relative simplicity in manufacturing. Most of the research work pertaining to non-recessed journal bearing assumes standard symmetric and asymmetric configurations. However, many more configurations are possible by changing the position of slot which may improve the performance of the slot-entry journal bearing. In the present work study of static performance characteristics of slot-entry journal bearing of different configuration has been carried out. The paper aims to discuss these issues. Design/methodology/approach – FEM has been used to solve the Reynolds equation governing the flow of lubricant in the bearing clearance space along with the restrictor flow equation. The non-Newtonian lubricant has been assumed to follow the cubic shear stress law. The performance characteristics of slot-entry hybrid journal bearings are computed by developing a computer program. Findings – The simulated results of bearing characteristics parameters in terms of minimum fluid-film thickness and bearing flow have been presented for the wide range of various values of non-linearity factor and external load. It is found that there is an increase in the oil requirement for slot-entry hybrid journal bearing with the specified operating and geometric parameters, when the viscosity of the lubricant decreases due to the non-Newtonian behavior of the lubricant. The effect of the decrease in the viscosity of the lubricant due to non-Newtonian behavior of the lubricant diminishes the attitude angle. The computed performance characteristics are helpful for the bearing designer while choosing a particular configuration of bearing. Research limitations/implications – The performance characteristics have been computed by considering the non-Newtonian lubricants. The thermal effects have been ignored in the analysis so as to obviate the mathematical complexity. Originality/value – Get idea from already published manuscripts. [ABSTRACT FROM AUTHOR]

Purpose – This paper aims to investigate the effect of plugging of holes on the static performance characteristics of a constant flow valve compensated hole-entry hybrid journal bearing system operating with Newtonian and non-Newtonian lubricants. The analysis considers the generalized Reynolds equation governing the flow of lubricant having variable viscosity in the clearance space and equation of flow of lubricant through constant flow valve restrictor. The non-Newtonian lubricant is assumed to follow the power law. The performance characteristics are computed for the two values of power law index (n=1.0 and 0.566). The computed results indicate that the blockage of holes during operation will not be the likely causes for the imminent failure of a well-designed non-recessed hole-entry hybrid journal bearing. Design/methodology/approach – Finite element method has been used to solve generalized Reynolds equation governing the flow of lubricant having variable viscosity in the clearance space and equation of flow of lubricant through constant flow valve restrictor. Findings – The computed results indicate that the blockage of holes during operation will not be the likely causes for the imminent failure of a well-designed non-recessed hole-entry hybrid journal bearing. The bearing configuration with plugged holes provides sufficient fluid film thickness and low power requirement as less lubricant is required to be pumped in the bearing. Originality/value – To the best of the author's knowledge, no study which considers the influence of plugging of holes on the static performance characteristics of a constant flow valve compensated hole-entry hybrid journal bearing system operating with Newtonian and non-Newtonian lubricant is yet available in the literature. [ABSTRACT FROM AUTHOR]

Purpose – Current lubrication analyses of misaligned journal bearings are generally performed under some given preconditions. The purpose of this paper is to calculate the lubrication characteristics of a journal bearing with journal misalignment caused by shaft deformation under load, considering the surface roughness, thermal effect and (thermal and elastic) deformation of bearing surface simultaneously. Design/methodology/approach – The lubrication of bearing was analyzed by average flow model based generalized Reynolds equation. The deformation of bearing surface under pressure or heat of oil film was calculated by compliance matrix method. The compliance matrix was established by finite element analysis. The temperature distributions of oil film and bearing were calculated by energy equation and heat conduction equation. Findings – When the thermal deformation of bearing and journal surface is considered, the radius clearance affects not only the value of the maximum oil film pressure and minimum oil film thickness, but also the distribution of oil film pressure and thickness of misaligned bearing. The effect of thermal deformation of bearing on the performance of misaligned bearing is larger than that of elastic deformation of bearing. Whether or not the surface roughness affects the performance of misaligned bearing and the affecting level depends greatly on the condition of deformation of bearing surface. Originality/value – The surface roughness, thermal effect and (thermal and elastic) deformation of bearing surface were considered simultaneously in the thermoelastohydrodynamic lubrication analysis of bearing with journal misalignment caused by shaft deformation under load. The results of this paper are helpful to the design of the bearing. [ABSTRACT FROM AUTHOR]

Purpose – The purpose of this paper is to examine the use of a new feature reduction technique with novelty detection on vibration and acoustic-emission sensors monitoring bearings mounted in the test benches of automotive manufacturers. Design/methodology/approach – Signals from standard accelerometers and acoustic-emission sensors were gathered from bearings operating under steady conditions on an accessory-drive test bench. The bearings under test were subject to a variety of faults including fretting. These signals were processed and reduced to standard feature vectors, the dimensionality of which was reduced using a new principal-component-like technique optimized for novelty detection. The reduced data were analyzed with a novelty detection technique called the Support Vector Data Descriptor. Findings – The classification results from these sensors, after being reduced with the proposed feature reduction technique, are substantially improved over those achievable with only standard novelty detection; nearly zero-percent classification error was achieved. Research limitations/implications – The feature reduction technique depends, in part, on the availability of the fault type in question – potentially violating the normal novelty detection assumption of limited abnormal data. This may require the manufacturer to gather real or simulated fault data prior to running tests. Practical implications – Incipient faults may be detectable at a much earlier stage in a manufacturer's component failure analysis. Test engineers may use this technique to reliably automate the fault detection process and enable improved root-cause analysis through the earlier identification of faults. Originality/value – The application of the feature reduction technique will provide manufacturers and researchers with a new means of improving fault detection in machinery components. [ABSTRACT FROM AUTHOR]

Purpose – The purpose of this paper is to show how controlled exposure of electromagnetic fields toward bearing steel vulnerates the microstructure. The ability of Barkhausen Noise signal processing is used for detecting phenomena such as dislocation and subgrain formation processes as the beginning of later failures. Design/methodology/approach – A Barkhausen noise signal measurement equipment is used for detecting subsurface distress of 100Cr6 as a function of the applied electromagnetic and mechanical stress. Barkhausen noise signal is mathematically processed by use of fractal dimension analysis. Findings – The paper cleary reveals significant impact of electromagnetic field in junction with mechanical loading. Electromagnetic impact depends on the magnitude of the field. Research limitations/implications – Research limitations are given by the fact that in real field applications, e.g. wind power plants, bearings are exposed by multiple influences and the methodology is not applicable to those conditions. Practical implications – The methodology can be applied to real field applications in condition monitoring systems. Up to now, no reasonable on-line measurement is in use determining sub surface fatigue phenomena. The paper hence, reveals the possibility to raise condition monitoring into a new perspective. Originality/value – The use of Barkhausen noise signal processing, as presented here, is original with respect to real field applications, such as wind power plants with a high demand in condition monitoring, especially off-shore plants. [ABSTRACT FROM AUTHOR]

Purpose – On the ground of the Hopf bifurcation theory derived by Hassard et al., the purpose of this paper is to investigate the weakly nonlinear dynamics of transverse rough-surface short journal bearings. Design/methodology/approach – By application of the stochastic model of rough surfaces, developed by Christensen and Tonder, the roughness effects of transverse surface patterns on the bifurcation behaviors close to the Hopf bifurcation point are investigated. Findings – It is found that the dynamic behavior of transverse rough-surface short journal bearings can display Hopf bifurcation phenomena. Comparing with the case of isotropic rough-surface bearing by Lin, under the same parameters, the effects of transverse surface roughness provide a reduced sub-critical Hopf bifurcation region as well as an increased super-critical Hopf bifurcation region. In addition, the effects of transverse surface roughness result in a lower stability-threshold critical speed for both the sub-critical bifurcation profile and the super-critical bifurcation profile. Originality/value – The present study, associated with the results of Hopf bifurcation regions and periodic orbits, can provide useful information for engineers when the transverse surface roughness effects and the bifurcation behavior are considered in a journal bearing system. [ABSTRACT FROM AUTHOR]

Purpose |!|#8211; Bearings in field applications with high dynamic loading, e.g. wind energy plants, suffer from sudden failure initiated by subsurface material transformation, known as white etching cracks in a typical scale of |!|#956;m, preferably around the maximum Hertzian stress zone. Despite many investigations in this field no precise knowledge about the root cause of those failures is available, due to the fact that failure under real service conditions of wind energy plants differs from what is known from test rig results in terms of contact loading, lubrication or dynamics. The purpose of this paper is to apply Barkhausen noise measurement to a full bearing test ring running under conditions of elastohydrodynamic lubrication (EHL) with high radial preload. Design/methodology/approach |!|#8211; Full bearing tests are carried out by use of DGBB (Deep Grove Ball Bearings) with 6206 specification, material set constant as 100Cr6, martensitic hardening, 10-12 percent maximum retained austenite and radial preload of 3500|!|#8201;MPa. Speed is set 9000|!|#8201;rpm, temperature is self setting at 80|!|#176;C by test conditions. For tests, synthetic hydrocarbon base oil (Poly-|!|#945;-Olefine) with a 1 percent amount of molydenum-dithiophosphate (organic chain given as 2-ethylhexyl) was used. Findings |!|#8211; Non-destructive fractal dimension analyses by use of Barkhausen noise measurements is of versatile value in terms of recording bearing manufacturing processes, but can also be part of non-destructive condition monitoring of bearings in field applications, where predictive reactive maintenance is crucial for availability of the plant. Research limitations/implications |!|#8211; Barkhausen noise signal recording may also be valuable for case studies related to microstructure changes of steel under operation conditions. Bearings are exposed in plenty of conditions to phenomena such as straying currents, subsequently straying magnetic fields. Hardly anything is known about how microstructure of bearing steel is susceptible to such conditions. This will be part of further studies. Originality/value |!|#8211; Results given in the paper show that sudden bearing failure, according to formation of subsurface material property changes might be driven by activities of dislocations. Since those activities start with sequences of stress field-induced formation of domains, later by formation of low-angle subgrains, and at least phase transformation, recording of the Barkhausen signal would lead to real predictive condition monitoring in applications where a highly dynamic loading of the contact, even with low nominal contact pressure leads to sudden failure induced by white etching. [ABSTRACT FROM AUTHOR]

Purpose |!|#8211; The purpose of this paper is to provide information on lubricant contamination by biodiesel using vibration and neural network. Design/methodology/approach |!|#8211; The possible contamination of lubricants is verified by analyzing the vibration and neural network of a bench test under determinated conditions. Findings |!|#8211; Results have shown that classical signal analysis methods could not reveal any correlation between the signal and the presence of contamination, or contamination grade. On other hand, the use of probabilistic neural network (PNN) was very successful in the identification and classification of contamination and its grade. Research limitations/implications |!|#8211; This study was done for some specific kinds of biodiesel. Other types of biodiesel could be analyzed. Practical implications |!|#8211; Contamination information is presented in the vibration signal, even if it is not evident by classical vibration analysis. In addition, the use of PNN gives a relatively simple and easy-to-use detection tool with good confidence. The training process is fast, and allows implementation of an adaptive training algorithm. Originality/value |!|#8211; This research could be extended to an internal combustion engine in order to verify a possible contamination by biodiesel. [ABSTRACT FROM AUTHOR]

Purpose – The purpose of this paper is to examine the development of aerodynamic thrust bearings and aerodynamic journal bearings applied to a small high speed cryogenic turboexpander in Indian conditions. Design/methodology/approach – As a part of indigenous programme in the process of development, some input parameter was taken from the available literature and then dimensions were optimized and computed while taking care to minimize fabrication constraints. Findings – A series of tests were conducted to confirm the findings. Detailed study of the effect of stability and vibration of bearings was taken up. The maximum rotational speed obtained was 200,000 rpm. Practical implications – The outcome may help the designers, researchers and manufacturers of these components. Originality/value – Although manufacturers design and develop the bearings of turboexpanders for their production, no academic literature has been available for this purpose until now. [ABSTRACT FROM AUTHOR]

Purpose – The elastic deformation of crankshaft bearing surface will be caused when acted by oil film pressure, which will affect the lubrication performance of crankshaft bearing. The model of the single bearing housing was usually used in the calculation of the elastic deformation of bearing surface. In actual internal combustion engine, the main bearing housing is combined together with engine block; deformation of the main bearing surface will be affected by deformation of the engine block. The purpose of this paper is to investigate the effect of deformation of the whole engine block on the hydrodynamic lubrication performance of main bearings. Design/methodology/approach – The loads of main bearings were calculated by the whole crankshaft beam-element finite element method. The lubrication of crankshaft bearings was analyzed by dynamic method. The elastic deformations of bearing surface under oil film pressure were calculated by compliance matrix method. The compliance matrix was established by finite element analysis. Findings – It may be not necessary to consider the effect of elastic deformation of bearing surface under film pressure in the lubrication analyses of main bearings for internal combustion engine when the very high calculating accuracy is not required. Originality/value – The elastohydrodynamic lubrications of crankshaft bearings considering the deformation of engine block were analyzed for the main bearings of an engine. Till now, whether or not the complicated model of the whole cylinder block should be considered to calculate the elastic deformation of main bearing surface in the lubrication analyses of crankshaft main bearings has not been done. [ABSTRACT FROM AUTHOR]

Purpose – This paper aims to describe the theoretical study concerning the effect of non-linear behavior of the lubricant on the performance of symmetric constant flow valve compensated hole-entry hybrid journal bearing. The bearing performance characteristics have been computed for various values of non-linearity factor, land width ratio, aspect ratio and external load. Design/methodology/approach – The analysis considers the generalized Reynolds equation governing the flow of lubricant having variable viscosity in the clearance space and equation of flow of lubricant through constant flow valve restrictor. The non-Newtonian lubricant is assumed to follow the cubic shear stress law. Findings – The study indicates that for generation of accurate bearing characteristics data, the inclusion of non-linear effects of lubricant in the analysis is essential. Originality/value – The performance characteristics in terms of minimum fluid-film thickness, fluid-film stiffness and damping coefficients, critical mass and threshold speed for a wide range of values of the non-linearity factor and external load are presented. The results presented are expected to be quite useful to bearing designers. [ABSTRACT FROM AUTHOR]

Purpose – This paper employs a hybrid numerical method combining the differential transformation method (DTM) and the finite difference method (FDM) to study the bifurcation and nonlinear behavior of a rigid rotor supported by a relative short gas lubricated journal bearing system with herringbone grooves. The analysis reveals a complex dynamic behavior comprising periodic, subharmonic and quasi-periodic responses of the rotor center. The dynamic behavior of the bearing system varies with changes in the rotor mass and bearing number. The current analytical results are found to be in good agreement with those of other numerical methods. This paper discusses these issues. Design/methodology/approach – In this paper, DT is used to deal Reynolds equation and is also one of the most widely used techniques for solving differential equations due to its rapid convergence rate and minimal calculation error. A further advantage of this method over the integral transformation approach is its ability to solve nonlinear differential equations. In solving the Reynolds equation for the current gas bearing system, DTM is used for taking transformation with respect to the time domain τ, and then the FDM is adopted to discretize with respect to the directions of coordinates. Findings – From the Poincaré maps of the rotor center as calculated by the DTM&FDM method with different values of the time step, it can be seen that the rotor center orbits are in agreement to approximately four decimal places for the different time steps. The numerical studies also compare the results obtained by the SOR&FDM and DTM&FDM methods for the orbits of the rotor center. It is observed that the results calculated by DTM&FDM are more accurately than SOR&FDM. Therefore, the DTM&FDM method suits this gas bearing system and provides better convergence than SOR&FDM method. Originality/value – This study utilizes a hybrid numerical scheme comprising the DTM and the FDM to analyze nonlinear dynamic behavior of a relative short gas lubricated journal bearing system with herringbone grooves. The system state trajectory, phase portraits, the Poincaré maps, the power spectra, and the bifurcation diagrams reveal the presence of a complex dynamic behavior comprising periodic, subharmonic and quasi-periodic responses of the rotor center. Therefore, the proposed method provides an effective means of gaining insights into the nonlinear dynamics of relative short gas lubricated journal bearing systems with herringbone grooves. [ABSTRACT FROM AUTHOR]

Purpose – The purpose of this paper is to study the influences of both the number and locations of entry holes on the static and dynamic characteristics of a rigid rotor supported by two double-rows, inherently compensated aerostatic bearings. Design/methodology/approach – The air is assumed to be perfect gas undergoing the adiabatic process and passing through entry holes into the bearing clearance. Air film in the clearance is governed by Reynolds equation including the coupled effects of wedge due to rotor rotation and squeezed film due to rotor oscillation. Findings – The method is used to analyze Reynolds equation, which is then solved by the finite difference method and numerical integration to yield static and dynamic characteristics of air film. The equation of motion of the rotor-bearing system is obtained by using the perturbation method and the eigensolution method is used to determine the stability threshold and critical whirl ratio. Originality/value – The paper considers the eccentricity, rotor speed, and restriction parameter in the analysis of the whirl instability of the rotor-aerostatic bearing system for the comparisons between various designs in the number and locations of entry holes of aerostatic bearings. [ABSTRACT FROM AUTHOR]

Purpose – The purpose of this paper is to investigate the static stiffness of hydrostatic bearings with three constant compensations in types of constant-flow pump, capillary and orifice, and both single-action and double-action variable restrictors with cylindrical-spool, tapered-spool, and membrane types by film gradient and recess pressure. Design/methodology/approach – This paper utilizes the equations of flow equilibrium to determine the variations of film thickness or displacement of loading table with respect to the varying of recess pressure. For a hydrostatic bearing whose recess pressures are controlled by compensations, the stiffness characteristics can be presented directly by these variations. Findings – The usage range of recess pressure and compensation parameters should be selected to correspond to a variation with smallest gradient. Originality/value – This paper proposes an extensive database as a critical requirement for the selection of types and parameters of the compensation as to yield the acceptable or optimized characteristics in design of hydrostatic bearings. [ABSTRACT FROM AUTHOR]

Purpose – Hole-entry hybrid journal bearings are widely used in many applications owing to their favourable characteristics. Ever increasing technological developments demand much improved performance from these class of bearings operating under the most stringent, exact and precise conditions. Therefore, it becomes imperative that the hole-entry journal bearings be designed on the basis of more accurately predicted bearing characteristics data. The purpose of this paper is to describe a theoretical study to demonstrate the combined influence of the effect of pocket size at the outlet of supply holes and the journal misalignment on the performance of an orifice compensated hole-entry hybrid journal bearing system. Design/methodology/approach – Finite element method is used to solve the Reynolds equation governing the flow of an incompressible lubricant in the clearance space between the journal and bearing together with equation of flow through an orifice. The journal misalignment has been accounted for by defining a pair of misalignment parameters sigma and delta. The effect of pocket size at the outlet of supply holes has been accounted by defining a non-dimensional parameter which is function of diameter of pocket and journal diameter. Findings – The results presented in this paper indicate that the effect of journal misalignment is, in general, to cause a reduction in bearing dynamic characteristics parameters whereas the effect of pocket size is to slightly compensate this loss. Performance of a two lobe four recessed journal bearing, a proper selection of bearing offset factor along with type of restrictor (capillary or orifice) is essential. Originality/value – This paper presents valuable data relating to hole-entry hybrid journal bearings useful for bearing designers. [ABSTRACT FROM AUTHOR]

In this paper, computer-aided design optimization approach for hydrostatic bearings is presented. The optimization problem is formulated in multicriteria strategy. The power loss and the temperature rise of oil are considered as performance measures for optimal hydrostatic bearing design. Optimization results indicate the effectiveness of the proposed combined approach which has advantages over the single criteria optimization. Sample results are presented to verify the proposed approach. [ABSTRACT FROM AUTHOR]

Describes the fabrication of MEMS micro bearings and the benefits that they provide. Uses the LIGA process with UV light and SU-8 photoresist to create the structures. A fluid passing through the cavity is used to lift up and levitate the rotor within the confines of the cavity. [ABSTRACT FROM AUTHOR]

Investigates rotation effects on hybrid plain journal bearings with various feeding mechanisms, i.e. orifice, capillary and porous feedings. Employs the numerical method of the finite difference to solve Reynolds equations. Shows that higher speed of rotation induces greater hydrodynamic load capacity, especially with an eccentricity ratio ε > 0.85. The porous and orifice feedings also result in higher load capacity than orifice and capillary feedings when the rotation speeds increase. Also analyses the multi-array of hole-entry of orifice and capillary feedings and the results show that the bearings with more arrays of feedings produce higher load capacity at low speed. However, the bearings with fewer arrays of feedings produce higher load capacity at high speeds. In other words, the transition from the hydrostatic to hydrodynamic load capacity of the bearing is significant to hybrid plain journal bearings. [ABSTRACT FROM AUTHOR]

Presents theoretical results regarding the computational estimation of the critical rotational speed in smooth or of negligible roughness and waviness hydrodynamically lubricated journal bearings. Results were provided using a developed calculational simulation code adapted to modelling of hydrodynamic lubrication regime encountered in the operation of various conventional or unconventional configuration finite journal bearings (j-b). It is concluded that empirical formulae of general character used to determine j-b rotational speed critical domain may either considerably underestimate or overestimate operational magnitudes. This fact leads to the necessity of use of high values for rotational speed safety factors in order to assure liquid lubrication and to avoid j-b contacts during operation. Relevant diagrams resulting from the present investigation show a direct estimation of critical j-b operational magnitudes. [ABSTRACT FROM AUTHOR]

Rolling element bearing failures in paper mill machines are considered in relation to their critical role in the machine function. The use of expensive, sophisticated and highly automated equipment and machines and the intention to achieve higher quality products, longer machine life, higher machinery effectiveness and safer operating processes were the main driving force motivating efforts to improve the maintenance concept during the last 50 years. In this paper, a conceptual model that integrates the available condition information, the deterministic models used in condition monitoring based upon mechanical theory and the probabilistic models used in the area of operational research is developed and its applicability is discussed. This model covers fault detection of a mechanical component such as a rolling element bearing, prediction of its vibration level in the near future, assessment of the probability of failure of a component over a finite period of time of interest. [ABSTRACT FROM AUTHOR]

Efforts have been made to study the optimum film profile for a longitudinally rough slider bearing. The roughness of the bearing surface is modelled by stochastic random variable with non-zero mean, variance and skewness. The governing differential equation for lubricant pressure is the Reynolds equation which is stochastically averaged with respect to the random roughness parameter. The method of infinitesimal is used to determine the optimum lubricant film profile. Results for the step location, step height ratio and the bearing performance characteristics, such as load carrying capacity of the bearing, centre of pressure, frictional force and coefficient of friction for different values of α, σ and ε, are numerically computed and tabulated. It is observed that the parameters α, σ and ε characterizing the surface roughness of the bearing affect the bearing performance characteristics significantly. [ABSTRACT FROM AUTHOR]