Load Carrying Capacity Of Bearing Research Articles

Case Depth and Static Capacity of Surface Induction-Hardened Rings

Abstract Large-size slewing bearings are usually surface hardened by means of induction heating. The load-carrying capacity of the bearing is dependent on, among others, the depth of the hardened layer, i.e., case depth (CD). It is of crucial importance for bearing manufacturers to ensure that sufficient CD is produced to meet the required bearing capacity for the applications. Compared to through-hardened bearings, the calculation method for the load-carrying capacity of surface-hardened bearings, especially the induction-hardened bearings, is not well established. This paper reports on a new calculation method for the static capacity of induction-hardened rings. The method is based on consideration of both the plastic indentation on the raceway and the damage tolerance in the subsurface region. The models for evaluating plastic indentation and subsurface damage have been validated with the standing contact fatigue testing.

Experimental studies of pressure distributions in finite slider bearing with single continuous surface profiles on the pads

There are indications in the literature that surface profiling/texturing can have significant and positive influence on the load carrying capacity of hydrodynamic pad thrust bearings. Moreover, due to cost and resource conservation considerations, lubricating oils are being used for much longer period of service than in the past. This causes lubricant to be subjected to higher levels of contamination in spite of good filtrations. In turn, hydrodynamic bearings generally operate in the presence of tiny contaminant particulate. Thus, performance study of hydrodynamic thrust bearing with pads’ surface profiling and contaminated oil are vital. Presently, one finds dearth of experimental research in this area. Therefore, the objective of this paper is to compare the experimental results of pressure distributions in slider bearing with various single continuous surface profiles of pads (cycloidal, catenoidal, polynomial, and plane) using clean and contaminated lubricating oils. Pressure results presented in this paper can provide a platform for validation of theoretical models based on contamination in lubricating oil.

3041 静圧気体スラスト軸受の負圧を利用した物体の非接触な懸垂支持と搬送(S81-1 トライボロジーの基礎と応用(1),S81 トライボロジーの基礎と応用)

The complicated phenomena such as pressure depressions, shock waves and the negative pressure, are detected in the air flow with a large bearing clearance or high supply pressure in an externally pressurized gas-lubricated circular thrust bearing. The pressure depression, which decreases the bearing load carrying capacity, is an undesirable phenomenon occurring in this gas bearing. The static characteristics of bearing for the non-contacting suspension support and conveyance of the object utilizing the negative pressure of this gas bearing is investigated numerically, and is also discussed in this paper.

Improved Load Carrying Capacity of Crosshead Bearings (Measurement of Oil Film Thickness using LIF Method)

The crosshead bearing in large two-stroke diesel engines operates under severe lubrication conditions, because hydrodynamic action is limited by low amplitude, low velocity oscillation under high unidirectional load. The recent trend towards more compact engines with increased output raises the bearing specific load, thereby causing the lubrication severity to increase significantly. Thus it is very important to improve the load carrying capacity of the crosshead bearing. In the present study, experiments using a dynamically loaded bearing test apparatus were carried out to clarify how the oil film characteristics could be improved. The oil film thickness was accurately measured using a laser induced fluorescence (LIF) method. The major results are : (1) A decrease in the clearance ratio is generally effective in enhancing squeeze action on the entirety of the bearing pads. When the clearance ratio becomes too low, however, the ability to form an adequate wedge film is degraded, thereby causing the oil film thickness to decrease ; (2) Even when the bearing has a very low clearance ratio, because incorporating the taper geometry on both sides of the oil-groove promotes wedge action, a significant improvement in the oil film characteristics can be expected ; and (3) The minimum oil film thickness becomes a maximum when using the taper geometry with a subtended length of 5 degrees and a taper angle of 0.1 degree.

Influences of Taper Geometry Modified Oil-Grooves on Load Carrying Capacity of Crosshead Bearings

The crosshead bearing in large two-stroke diesel engines operates under severe lubrication conditions, because the bearing oscillates within a small angle at a low speed and is always subject to a high downward load. The recent trend towards more compact engines with increased output raises the bearing specific load, thereby causing the lubrication severity to increase significantly. Thus it is very important to improve the load carrying capacity of the crosshead bearing. In the present study, experiments using a dynamically loaded bearing seizure test apparatus were carried out to clarify the influences of the clearance ratio and the oil-groove geometry on the load carrying capacity. The electrical resistance of the oil film was also measured to evaluate the extent of the oil film formation. The major results are: (1) A decrease in the clearance ratio is effective in enhancing squeeze action on the entirety of the bearing pads, thereby improving the load carrying capacity. When the clearance ratio becomes too low, however, the ability to form an adequate wedge film is degraded, causing the load carrying capacity to decrease; (2) A significant improvement in the load carrying capacity can be expected, because incorporating the taper geometry on both sides of the oil-groove promotes a thicker oil film; and (3) A taper geometry with a subtended length of 5 degrees and a taper angle of 0.1 degree produces the maximum load carrying capacity.

The analysis of the effects of surface texture on the capability of load carriage of journal bearings using neural network

PurposeThis paper investigates the load carrying capacity of the journal bearings with steel shafts with varying surface texture in varying revolutions using experimental and neural network (NN) approach.Design/methodology/approachIn this study, we used a shaft with smooth surface with the same material properties compare their load carrying capacities of the shafts with three different pitches and two different profiles. The experimental data, such as pressure and oil temperature, are employed as training and testing data for NN. Quick Prop algorithm is used to update the weight of the network during the training.FindingsThe designated NN has superior performance for modelling of the system. Therefore, the proposed neural predictor would be used as a predictor for possible experimental applications on modelling bearing system.Research limitations/implicationsMobil 0W‐40 lubricant was used and kept at temperature of 18°C. The surface of the shafts has been in two types: smooth, that is without and with profiles, that is trapezoidal and saw.Practical implicationsOwing to the parallel structure and fast learning of NN, this kind of algorithm will be utilized to model other types of bearing systems.Originality/valueInstead of traditional methods, NN has fast learning and parallel processing structure. Moreover, NN can be used to process multiple‐input/multiple‐output data unlike other empirical modelling tools which can map one dependent variable at a time. Therefore, this method is able to predict the load carrying capacity with steel shafts with varying surface texture in varying revolutions satisfactorily where common techniques have failed.

Surface roughness effects on thermo-hydrodynamic lubrication of journal bearings lubricated with bubbly oil

In this paper, the combined effect of surface roughness and bubbles content on the hydrodynamic performance of journal bearings is studied. In the analysis, it is assumed that the bearing and shaft surfaces are covered with homogeneous isotropic roughness, the air bubbles are evenly distributed through the lubricant and the bubble size is very small. The modified Reynolds equation governing the pressure generation in the bearing gap for compressible fluid is solved simultaneously with the energy equation. Temperature and pressure distributions, coefficient of friction, bearing load capacity and attitude angle as affected by surface roughness, bubble content and some bearing parameters are presented. Results showed that the bearing load carrying capacity is higher at higher values of average roughness and higher bubble content as a direct consequence of the higher pressure values attained, and the average roughness and the bubbles content had no significant effect on the attitude angle. Copyright © 2006 John Wiley & Sons, Ltd.

Influences of Taper Geometry Modified Oil-Grooves on Load Carrying Capacity of Crosshead Bearings

The crosshead bearing in large two-stroke diesel engines operates under severe lubrication conditions, because the bearing oscillates within a small angle at a low speed and is always subject to a high downward load. The recent trend towards more compact engines with increased output raises the bearing specific load, thereby causing the lubrication severity to increase significantly. Thus it is very important to improve the load carrying capacity of the crosshead bearing. In the present study, experiments using a dynamically loaded bearing seizure test apparatus were carried out to clarify the influences of the clearance ratio and the oil-groove geometry on the load carrying capacity. The electrical resistance of the oil film was also measured to evaluate the extent of the oil film formation. The major results are : (1) A decrease in the clearance ratio is effective in enhancing squeeze action on the entirety of the bearing pads, thereby improving the load carrying capacity. When the clearance ratio becomes too low, however, the ability to form an adequate wedge film is degraded, causing the load carrying capacity to decrease, (2) Because incorporating the taper geometry on both sides of the oil-groove promotes a thicker oil film, a significant improvement in the load carrying capacity can be expected ; and (3) The maximum load carrying capacity is achieved by the taper geometry of a subtended length of 5 degrees and a taper angle of 0.1 degree.

The analysis of the effects of surface roughness of shafts on journal bearings using recurrent hybrid neural network

This paper presents an investigation for analysing the load carrying capacity of journal bearing in a variety of conditions using a proposed neural network (NN). The NN structure is very suitable for this kind of system. The network is capable of predicting the pressures of the experimental system. The network has parallel structure and fast learning capacity. It can be outlined from the results for both approaches, NN could be used to model journal bearing systems in real time applications.

クロスヘツド軸受の負荷能力に及ぼす油溝形状の影響(エンジンのトライボロジー・潤滑油,エンジンのトライボロジー・潤滑油)

The crosshead bearing in large two-stroke diesel engines operates under severe lubrication conditions, because the bearing oscillates within a small angle at a low speed and is always subject to a high downward load. The recent trend towards more compact engines with increased output raises the bearing specific load, thereby causing the lubrication severity to increase significantly. Thus it is very important to improve the load carrying capacity of the crosshead bearing. In the present study, experiments using a dynamically loaded bearing seizure test apparatus were carried out to clarify the influences of the clearance ratio and the oil-groove geometry on the load carrying capacity. The electrical resistance of the oil film was also measured to evaluate the extent of the oil film formation. The major results are: (1) A decrease in the clearance ratio is effective in enhancing squeeze action on the entirety of the bearing pads, thereby improving the load carrying capacity. When the clearance ratio becomes too low, however, the ability to form an adequate wedge film is degraded, causing the load carrying capacity to decrease; (2) A significant improvement in the load carrying capacity can be expected, because incorporating the taper geometry on both sides of the oil-groove promotes a thicker oil film; and (3) A taper geometry with a subtended length of 5 degrees and a taper angle of 0.1 degree produces the maximum load carrying capacity.

Loads carrying capacity map for the surface texture design of SiC thrust bearing sliding in water

Water lubricated silicon carbide is expected to be widely used for sliding bearings and mechanical seals in hydraulic systems since it is environmentally friendly and saves energy. The purpose of this study is to find the optimum surface texture to improve the load carrying capacity of SiC bearings working in water. Micro-pits, evenly distributed in a square array, were selected as the texture pattern, and formed on one of the contact surfaces by reactive ion etching. Experiments, which simulate the working condition of thrust bearings, were carried out to evaluate the effects of the micro-pits on the critical load of the transition of the lubrication mode from hydrodynamic to mixed. The results are summarized in the form of a load carrying capacity map. It was found that an optimum geometric and distributive range of micro-pits exists, where the load carrying capacity can be increased at least twice over that of an untextured surface.

The contributions of microrotation of lubricant molecules in a thin film journal bearing

Characteristics of a journal bearing were computed for thin film lubrication accounting for microrotation of the lubricant molecules using both the half-Sommerfeld and Reynolds boundary conditions. Although the Reynolds boundary conditions produced higher pressure and loads, the effects of microrotation studied by both schemes showed similar trends. Primary characteristics that effect the contributions of microrotation to the load carrying capacity of the journal bearing were identified. These characteristics were varied and their effects on the load capacity of the journal bearing are shown.

黒鉛分散した過共晶Ａｌ‐２３％Ｓｉ‐６％Ｃｕ‐１％Ｍｇ合金複合材の摺動特性

Al–23%Si–6%Cu–1%Mg cast alloy composites containing dispersed graphite were prepared by means of die cast method to develop the wear resistance of bearings in boundary lubrication. An influence of graphite content and graphite particle size on the wear characteristics of the aluminum cast composites were investigated by the radial thrust test and the radial journal bearing test. As the results, the strength of composites decreased with increase in graphite contents, and consequently, the load carrying capacity of bearing showed lower value. The good wear resistance of bearings were obtained at the graphite contents of 6 to 8 vol% in composites. Furthermore the graphite particle size had more effect on improvement of the load carrying capacity of bearing. Higher the load carrying capacities of bearings were obtained at the conditions of composites containing 10 vol% dispersed graphite with particle sizes 0.85~0.42 mm and 0.42~0.25 mm for the radial thrust rubbing test.

Analysis of Bubbly Lubrication in Journal Bearings.

The effect of air bubbles evenly distributed in lubricating oil on the bearing performances is analyzed theoretically. The Reynolds equation for the bubbly lubricant in a steady-state and isothermal condition is solved with an iterative numerical method. Surface tension and the radius of bubble are taken into account in the analysis. It is assumed that bubbles move along streamlines and do not split apart or coalesce. The density and the viscosity of air-oil mixture are treated as functions of oil film pressure and the volume fraction of air. Numerical results show that the load carrying capacity of a journal bearing increases as bubbles in the supplied lubricant become smaller or the surface tension is getting larger. The load carrying capacity increases as the volume fraction increases up to a critical volume fraction that gives maximum load carrying capacity. Beyond the critical volume fraction, it decreases as the volume fraction increases.

Effect of a Shrink Fitter on Load-Carrying Capasity of a Ceramic Bearing at Elevated Temperature.

When the ceramic bearing is used under the high temperature environment, the problem occurs. An interference changes because the coefficient of thermal expansion is greatly different between the steel and the ceramic. It is thought that this causes the adverse effect for a load carrying capacity of the ceramic bearing. In this paper, we have applied the shrink fitter to an assembly of the ceramic bearing to prevent the change in the interference. The outer races were broken at the load of 4410N when the shrink fitter was not used. With the shrink fitter the load carrying capacity was 8330N. Moreover, the stresses acting in the outer race of the ceramic bearing, due to the space between the outer race and the bearing, were analyzed by FEM.

The Hydromagnetic Flow between Two Rotating Eccentric Cylinders

An investigation of the steady two dimensional hydromagnetic viscous flow between two rotating eccentric cylinders in the presence of a radial magnetic field is attempted. The effects of the magnetic field on the flow has been investigated for various parameters including the eccentric parameter, the modified Reynolds number and the square of the Hartmann number. The stream function and the pressure distribution are calculated. The results presented graphically reveal that the effect of magnetic field enhances the load carrying capacity of the journal bearing.

Lubrication Characteristics of an Externally Pressurized Crosshead-Pin Bearing.

Because the crosshead-pin bearing for large size two-stroke diesel engines oscillates within a small angle at a low speed and is always subject to a high downward-load, the hydrodynamic oil film is very thin. It is important to improve the load carrying capacity of the crosshead-pin bearing in the context of raising engine power in recent years. In the present study, calculations were carried out to clarify the lubrication characteristics of the crosshead-pin bearing to which an externally pressurized lubrication system was applied. Because the externally pressurized crosshead-pin bearing forms a very thick oil film at the bottom dead center, an improved hydrodynamic squeeze action is produced, thereby greatly increasing the minimum oil film thickness. Increasing the hydrostatic lift as well as extending the oil pocket pitch angle are effective means to improve the squeeze action, and thereby to increase the minimum oil film thickness.

An Analysis of Powder Lubricated Slider Bearings

Abstract A theory for predicting the behavior of powder lubricated slider bearings based on the collisional characteristics of the grain particles and their interactions at the boundaries is presented. General boundary conditions that account for the effects of powder slippage are applied to the slider bearing configuration. Theoretical predictions are presented with comparison to published experimental measurements. An extensive parametric study is also conducted to illustrate the behavior of the flow and the response of the bearing's load-carrying capacity and friction factor to changes in various powder material and boundary parameters.

A High Performance Journal Bearing With Controlled Elastic Deflection

A thermo-elasto-hydrodynamic analysis of an undercut journal bearing is presented whereby elastic deflection is introduced in a certain area of the bearing surface. The hydrodynamic pressure is computed from the generalized Reynolds equation, which takes into account thermal effects on viscosity. This is accomplished by solving the full energy equation for temperature. The elastic deflection is obtained from the elasticity equation. This study is then complemented with an elasto-hydrodynamic analysis of the full bearing. The controlled elastic deflection increases the bearing load carrying capacity and reduces friction.

A Transition-Turbulent Lubrication Theory Using Mixing Length Concept

This paper applies the recently introduced Reynolds stress expression (Tieu and Kosasih, 1992) in the transition-turbulent lubrication analysis. The Reynolds stress is modeled using the mixing length expression which is able to account for the effect of local shear stress gradient, and it can be extended to apply in the transition regime. This theory is then used to determine three-dimensional velocity distributions between parallel plates. From the results, a set of coefficients covering transition-turbulent regime used in conjunction with the modified Reynolds equation is presented. It is shown that the resulting coefficients agree well with results of Elrod and Ng (1967) in the fully turbulent regime while differences are shown in the transition regime. Pressure distributions and load carrying capacity of superlaminar journal bearing are compared with available experimental data.