Bearing Temperature Rise Research Articles

Analysis on Influence of Oil Film Thickness on Temperature Field of Heavy Hydrostatic Bearing in Variable Viscosity Condition

According to the problem of the influence of oil film thickness on temperature rise for heavy hydrostatic thrust bearing during operation， build viscosity-temperature equation of lubricating oil film and mathematics model of oil film temperature rise of heavy hydrostatic bearing with multiple oil pads, simulate the temperature field of hydrostatic bearing with sector cavity under various oil film thickness using FVM(finite volume method), and reveal the influence law of oil film thickness of temperature rise for hydrostatic bearing. The results show that temperature distribution of hydrostatic bearing is much the same under various oil film thicknesses, but the influence of oil film thickness of temperature rise for hydrostatic bearing is greater. The results of numerical calculations actually response flow state inside hydrostatic bearing ，offer theoretical foundation for the design of hydrostatic bearing in engineering practice, and have important significance in improving operation stability of NC machine.

Investigation of the High Speed Rolling Bearing Temperature Rise With Oil-Air Lubrication

The oil-air lubrication system has been widely used for rolling ball bearing. However, as the rotation speed increases, the temperature rise will increase dramatically, resulting in shortening the service life of the ball bearing. The existing literature has offered valuable fundamental data about the oil-air lubrication of rolling bearing; however, there are still some problems that concerned the oil-air lubrication, which are not addressed. In this study, an experiment setup to investigate the oil-air lubrication for the high speed ball bearing has been developed, and performance tests of hybrid ceramic and steel ball bearings under the extensive operating conditions including oil-air supply pipe length, bearing preload, lube interval, oil type, oil viscosity, nozzle design, and rotation speed have been conducted. The test results show that the bearing has the lowest temperature rise with the pipe length of 1.5 m. For the steel ball bearing, the proper preload decreases with increasing of the rotating speed, and the temperature rise of the hybrid ceramic ball bearing is not sensitive to the axial preload. There exists a proper amount of lubricant for the bearing at each rotational speed; and a larger amount of lubricant is required for the bearing as the rotating speed increases. The tested bearings under different speeds have almost the same lowest temperature rise under the lubricant with the viscosity of 100 cSt; a higher or lower viscosity will increase the bearing temperature rises. The nozzle design is an important factor to affect the temperature rise of the ball bearing, and the suitable geometric parameter of the nozzle is closely related to the cage landing method of the bearing. The temperature rise of tested bearings increases with the increase in the rotation speed; and the hybrid ceramic ball bearing always has a lower temperature rise than that of the steel ball bearing at the same operating conditions.

Study on Thermal Properties of Hybrid Journal Bearing for Super High Speed Grinding Machine

As the high speed bearings, hybrid journal bearings are usually used in high and super high speed grinding machine spindle system. Since the bearing operates under high speed conditions, the excessive temperature rise of bearing is a key factor to lower the accuracy of the spindle system and limit the bearings working speed, so restrict the bearing applications. In this paper, the model of hybrid journal bearing is established to analyze the heat mechanism. In addition, the temperature field distribution for the certain hybrid journal bearing at high speed is studied by ANSYS considering the heat transfer characters between fluid and solid. The experiment of temperature for hybrid journal bearing system in super high speed grinding machine is also performed. The thermal properties and the measure for controlling temperature rise of such bearings are analyzed.

Analysis of Thermal Properties of Super-High Speed Hybrid Journal Bearing Based on ANSYS

Hybrid journal bearings are used in the high and super high speed cases mainly, such as the super-high speed spindle system. Since the bearing operates under high speed conditions, the excessive temperature rise of the bearing is a major reason to lower the accuracy of the main shaft system and limit the bearings working speed higher, as a result, restrict the bearing applications. In this paper, the thermal properties and the heat mechanism of such bearings are analyzed. The mathematical model of hybrid journal bearing is established to analyze the mechanism of generating heat. In addition, the temperature field distribution for the certain hybrid journal bearing at speed of 10000 rpm is studied by means of software ANSYS considering the heat transfer characters between fluid and solid. An improved measure about temperature rise of hybrid journal bearing is presented.

Investigation of variable optimum preload for a machine tool spindle

Angular contact ball bearings have been widely used in machine tool spindles, and the bearing preload plays an important role on the performance of the spindle. With the development of high speed machining, especially for high speed milling, heavy cutting at a low speed and light cutting at a high speed are often performed on a single machine tool spindle, thus, high stiffness at low speed and low temperature rise at high speed are required. The traditional constant pressure preload method cannot meet the technical requirement of this kind of spindle any more. The variable preload technology is systematically investigated in this paper. At high speed range, FEM method is used to analyze the temperature distribution of the spindle, and the variable spindle preload is determined according to the constraint of temperature rise of bearings. At low speed range, the spindle preload is resolved by the fatigue life of bearings. The dynamic stiffness of the variable preload spindle is analyzed utilizing the Transfer Matrix Method (TMM) and a nonlinear bearing model that includes the centrifugal force and gyroscopic effects. An experimental set-up for the variable preload spindle is developed using hydraulic pressure that can automatically adjust the bearing preload. The proposed method to determine variable preload is verified experimentally by measuring the dynamic stiffness of the spindle and the temperature rise of the test bearing. The results show that the variable preload spindle gives outstanding behavior that the temperature rise at high speed is lower than that of the constant pressure preload spindle, and the dynamic stiffness at low speed range is significantly increased.

タンカーのカーゴオイルポンプ及びバラストポンプの取扱い

The handling liquid for tankers varies widely from low viscosity to high viscosity liquid. Recently, even VLCC starts handling high viscosity liquid. Since the heating device is not equipped to the cargo tank of VLCC, it is quite important to examine whether it is possible to discharge at the unloading port even though the viscosity at loading port was not high by heating. And cargo oil pump and ballast pump require a lot of valve manipulation during unloading and de-ballasting and there is a case of water hammer due to wrong manipulation and pump becomes inoperative. As a recent trend, it is occurring on ballast pump. There is a case of abnormal temperature rise of pump bearing occurs depending on the unloading condition. This is introducing cautions for these matters.

A strategy of investigation on the thermal behaviour of motorised spindles under high-speed machining

Motorised spindles used for high-speed machining are notorious for their sudden catastrophic failures at high speeds mainly due to bearing thermal problems. Loss of machining accuracy is another major problem due to thermal deformation of the spindle, which transmits motion to the cutting tool or to the workpiece. In this paper, a mathematical model to estimate the frictional losses in high-speed angular contact ball bearings and a heat dissipation model are developed. The steady state temperature distribution and thermal deformation of spindle are determined by finite element analysis considering both bearing and motor heat generation. The simulated temperature results are compared with experimental values reported elsewhere in the literature for validation. The influence of external cooling on the thermal behaviour of spindle bearings and spindle nose deformation is then investigated. An empirical equation is developed to accurately predict the bearing temperature rise.

Numerical analysis of lubrication in a journal bearing by a thermoelastohydrodynamic lubrication (TEHL) model

AbstractIn recent years, in high power, compact, and light weight automotive engines, the bearing load has been increasing and the housing stiffness has been decreasing. The engine bearing performance is significantly influenced by both an elastic deformation and an increase in temperature. Under these harsh operating conditions, an extreme temperature rise of the bearing is expected to occur in the thin oil-film region when the oil-film thickness is not kept thick enough within the bearing. Consequently, the high-temperature rise sometimes causes the bearing to have a seizure. Thus, it is necessary to predict accurately the bearing performance in a design stage. A thermoelastohydrodynamic lubrication (TEHL) analysis could theoretically predict the bearing performance under these harsh conditions with high reliability. In order to clarify the validity of the theoretical TEHL model, a rig test was conducted under dynamic load conditions. The test conditions simulated the connecting rod bearings in real aut...

Study on Sludge Formation during the Oxidation Process of Turbine Oils

Against the backdrop of increased needs for longer operating life of turbine oils, there is a tendency to use amine-type antioxidants for steam turbine oils as well as gas turbine oils. Amine-type antioxidants are known to form sludge during the oxidation process, and the sludge formation from turbine oils involves the high risk for a power plant of bearing temperature rise caused by sludge deposition onto the bearing surface. But currently, there is no global specification to evaluate the sludge formation from turbine oils that have high rotating bomb oxidation test (RBOT) life. In this study, we examined 18 kinds of commercially produced turbine oils and two kinds of originally prepared oils with amine additives on sludge formation under 120°C dry turbine oil oxidation stability test (TOST) accelerated degradation test. Consequently, we found a criterion to check the quality of sludge resistance of turbine oils based on the relationship between the RBOT residual ratio and weight of filter residues(1μ m pore filter).

Predictions of Temperature Rise for Ball Bearings

The ball bearing is widely used on many moderate speed rotating systems due to its low starting friction and high load capacity. However, the heat generation caused by high-speed operation has been the limiting factor for increasing the speed limit of many high-speed ball bearing applications. The objective of this study was to predict the heat generation and temperature rise of ball bearings operating at moderate rotating speed. A series of experiments have been conducted to investigate the effects of oil-mist and oil-air lubrication on temperature rise of ceramic and steel ball bearings. From these experimental results, the previous theoretical model for temperature rise of ball bearings was modified for the moderate speed operation conditions. A computer code was developed accordingly to investigate the relationship between preload, ball bearing parameters, heat generation and temperature rise. The effect of temperature on lubricant viscosity was also taken into account. Results from the improved theoretical model compare well with the experimental data.

Investigation of the ball-bearing temperature rise under an oil-air lubrication system

Ball-bearings are widely used on many high-speed rotating systems. However, heat generation and dynamic loading caused by high-speed operation have been the limiting factors for increasing the speed limit of many high-speed ball-bearing applications. Therefore, providing proper lubrication and preload to reduce heat generation effectively is a major task for high-speed ball-bearings. Recently, oil-air lubrication has been used on high-speed ball-bearings because of precise oil quantity control and high cooling efficiency. However, the fluctuation in oil supply resulting from the periodic oil feeding is unfavourable. In this study, equipment for measuring the fluctuation in the oil supply was established. The operation parameters affecting the stability of the oil supply for an oil-air lubrication system were experimentally studied. A test rig for high-speed ball-bearings was also developed. Tests were conducted to study the effects of the preload, oil quantity, air flowrate and rotating speed on the bearing temperature rise. The operating conditions that provide a stable oil supply and low bearing temperature rise were established.

工作機械主軸用転がり軸受の予圧調整技術

Spindles used in machine tools, especially machining centers, must operate at high speeds with high stiffness and low temperature rise in order to achieve improvements in productivity and accuracy of the machine. Usually, preloaded angular contact ball bearings are used to satisfy the requirements of low temperature rise and high stiffness. However, there are opposing effects that can result from preloading. Increasing the preload on the bearings to obtain high stiffness causes high temperature rise, which is not suitable for high-speed operations. On the other hand, high preload is necessary to ensure high stiffness when heavy cutting load, low speed conditions are required. This paper introduces the effects of preload control technology by fixed position on temperature rise and stiffness. High-speed operating tests and cutting tests using spindles equipped with preload control units were conducted. The results confirmed that lower preload reduces bearing temperature rise and higher preload improves the cutting surface roughness. Considering these characteristics, an optimum preload control program is proposed to satisfy both low temperature rise and high stiffness.

超高速平面研削盤用砥石スピンドルの開発 超高速研削に関する研究 （第１報）

This paper describes the development of a high-frequency wheel spindle for an ultra-high speed surface grinding machine. This project aims to achieve a high efficiency grinding of steel with cBN wheels, in which a stock removal rate is over 300 mm3/(mm·s) at a wheel peripheral speed of 400m/s. At such a speed, the power loss caused by air and coolant friction is larger than grinding power. At first, a theoretical analysis of grinding forces was carried out to estimate the grinding power. From this analysis the wheel diameter of φ250mm and motor power of 22kW at 30000min-1 were decided. Also, an eigenvalue analysis by FEM was carried out to decide the diameter of the spindle shaft that avoids the resonance caused by a heavy wheel. In the spindle unit, a newly developed method called the lubrication was adopted to achieve dn value of 195 × 104. The retainer reduces the no-load power and the temperature rise of bearings. Furthermore, constant pre-load mechanism was adopted to achieve a high stiffness without burning out the bearings. Finally, the advantage of a small diameter wheel is confirmed experimentally by measurement of air friction loss, which conformed to calculated results using the logarithmic law.

Improving the Survivability of High Speed Ball Bearings under Oil Shut-off Conditions by Chemical Modification of the Surface

Oil shut-off tests were performed using 150 mm bore M50-steel ball bearings under high speed rotation conditions. This investigation demonstrated that bearings that had received chemical modification of the surface were able to delay the onset of bearing seizure after lubricant shut-off Comparing the chemically modified surface, to a conventional bearing surface, this paper describes the differences and changes in the bearing temperature rise and the cage rotation speed after oil shut-off In addition, this paper presents an analysis on the changes of rolling element motion during oil shut-off for bearings with and without surface modification.

Anti-friction bearing temperature rise for NEMA frame motors

Anti-friction bearing temperature rise for NEMA frame motors

The Performance of Ball Bearings With Silicon Nitride Ceramic Balls in High Speed Spindles for Machine Tools

Two types of angular contact ball bearings for machine tools having steel rings and silicon nitride balls were tested and the temperature rise was compared with that of conventional steel ball bearings with grease lubrication and oil-air lubrication as well. Experimental results indicated that the temperature rise of silicon nitride ball bearings was much lower than that of steel ball bearings at high speeds. Calculations made using a computer demonstrated that the reduction of gyroscopic moments and centrifugal forces acting on balls because of the low density of silicon nitride resulted in about 30 to 50 percent less frictional loss at high speeds even with low-cost lubrication such as grease or oil-air.

A study of the characteristic analysis of high-speed journal bearings. Optimum design of journal bearings.

This paper describes an optimum design of hydrodynamic journal bearings under laminar and turbulent operating conditions. Simplified closed-form design formulas are presented for the eccentricity ratio, friction force on the journal surface and whirl onset velocity as a function of the Sommerfeld number or eccentricity ratio. The radial clearance, slenderness ratio and viscosity of oil, which optimize both the oil flow rate and the oil film temperature rise in hydrodynamic journal bearings under a constant load, are determined numerically for a wide range of journal revolution speeds.

A study of the characteristic analysis of high speed journal bearings. Optimum design of journal bearings.

This paper describes an optimum design of hydrodynamic journal bearings under laminar and turbulent operating conditions. Simplified mathematical expressions are presented for the eccentricity ratio, friction force and whirl onset speed as a function of the Sommerfeld number or eccentricity ratio. The radial clearance, slenderness ratio and viscosity of lubricants which optimize both the oil flow rate and the oil film temperature rise in hydrodynamic journal bearings under the constant load are determined numerically for a wide range of journal speeds.

Predicting Oil Ring Self-Lubricated Sleeve Bearing Temperature Rise and its Effect on Shaft Criticals

Several steps are involved in predicting the temperature rise within the babbitt/oil film of sleeve bearings. Initially, the viscous friction loss developed in the oil film is determined. This loss depends on the speed, length, and diameter of the journal, oil viscosity, and diametral clearance. A heat balance study then compares heat loss generation and dissipation rates. The final consideration is the ability of the oil rings to deliver the necessary oil flow rate. An approach for predicting sleeve bearing temperature rise and the adequacy of oil ring lubrication is described. It is shown that some of the design variables affecting the bearing temperature rise also influence the bearing oil film stiffness. The value of this stiffness plays a vital role in determining the shaft critical speed.

Dry wear of al-graphite particle composites

Under lubricated conditions, Al-graphite particle composite is a good antiseizure bearing and antifriction material possessing properties which inhibit excessive temperature rise in bearings. The present study characterizes the dry wear properties of the composite. The dry wear characteristics of the Al-(2.7%–5.7% graphite particle) (50–200μm) composite were found to deteriorate with the addition of graphite, load and sliding distance. Both micro structural and microhardness studies of the worn subsurfaces and analysis of wear debris show that the reductions in strength and ductility of the composite due to graphite addition are the most likely causes of deterioration in the wear properties of the composite.