温度及压力对滑动轴承气蚀磨损影响的实验研究

采用超声振动原理建立了滑动轴承模拟气蚀实验装置 ,研究了温度及压力变化对滑动轴承气蚀磨损的影响。发现温度及压力的升高都会使滑动轴承的气蚀磨损增加。并对这一现象从理论上进行了分析     

油气两相流工况下汽车发动机轴承气蚀磨损的模拟试验研究

采用超声振动原理建立了一台汽车发动机滑动轴承模拟气蚀试验装置。试验研究了空气混入滑动轴承后对其气蚀磨损的影响。通过大量试验研究结果的分析比较 ,发现空气的混入会使滑动轴承的气蚀磨损降低 ,且含气率越高这种影响作用越明显。并依据这一新发现对传统的空气蚀理论进行了重新分析与解释     

滑动轴承中气蚀磨损现象研究现状评述

介绍了滑动轴承产生气蚀磨损现象的过程及传统上的通常解释方法，通过对国际上近20年来滑动轴承气蚀现象研究情况的分析总结，归纳了各种关于滑动轴承气蚀发生的机理研究、针对气蚀现象所产生的各种算法、针对空气蚀及蒸气蚀所进行的各种实验研究，介绍了主要的研究成果，指出存在的问题，并探讨了进一步开展研究的方向。     

STUDY ON THE INFLUENCES OF BUBBLY OIL ON THE CAVITATION EROSION IN JOURNAL BEARINGS OF ENGINES

0 INTRODUCTIONWhen water, minera1 oil or any other kind offluid flow over a element surface, such as propeller,pump, valve, pipe, bearing, gears, injector, etc, becauseof a change of flow rate or a change of localgeometrical figuration, the local pressure will decreaserapid1y. If the local pressure becomes lower than thesaturation pre8sure of this kind of fluid, the dissolvedgases will come out of solution as bubbles. Besides, ifthe local pressure is below the vaPOr pressure of thisfluid,…     

Application of acoustic emission technique for the detection of defects in rolling element bearings

The usefulness of acoustic emission (AE) measurements for the detection of defects in roller bearings has been investigated in the present study. Defects were simulated in the roller and inner race of the bearings by the spark erosion method. AE of bearings without defect and with defects of different sizes has been measured. For small defect sizes, ringdown counts of AE signal has been found to be a very good parameter for the detection of defects both in the inner race and roller of the bearings tested. However, the counts stopped increasing after a certain defect size. Distributions of events by ringdown counts and peak amplitudes are also found to be good indicators of bearing defect detection. With a defect on a bearing element, the distributions of events tend to be over a wider range of peak amplitudes and counts.     

表面粗糙度对高速滚子轴承保持架运动性能的影响

在高速和轻载工况条件下，打滑擦伤往往成为圆柱滚子轴承的主要失效形式，而表面粗糙度对轴承打滑损伤有很大的影响。本文采用部分弹性流体动力润滑理论，分析了在表面粗糙度影响下，轴承润滑膜厚比以及轴承表面加工纹理与轴承保持架滑差率的关系，从而揭示表面粗糙度效应对高速滚子轴承运动性能的影响     

滚动轴承打滑蹭伤试验研究

基于高速滚动轴承试验机对滚动轴承打滑蹭伤展开试验研究,获得不同工况参数下滚动轴承打滑蹭伤的临界转速;研究滚动轴承在打滑蹭伤临界转速下不同运行时间对滚动轴承磨损程度的影响,以及滚动轴承打滑蹭伤后,继续以更高转速运行对滚动轴承磨损程度的影响。结果表明:滚动轴承发生打滑蹭伤瞬间伴随着摩擦扭矩、温度及振动加速度的同步突增,且其在润滑不充分及轻载工况下出现打滑蹭伤时的临界转速更低;滚动轴承在打滑蹭伤临界转速下运转时间越长,磨损越严重,这可能是由于打滑蹭伤破坏滚动轴承表面光洁度,使摩擦因数增大从而导致磨损速度加快;滚动轴承打滑蹭伤后,继续以更高转速运转时易出现二次淬火烧伤,大大降低轴承使用寿命。     

动车组轴箱轴承基于实测载荷的寿命预测方法*

针对动车组轴箱轴承所受载荷的复杂随机性,在轴箱弹簧和转臂载荷测试技术基础上,对某型动车组动力转向架轴箱进行线路实测,获取典型线路段弹簧和转臂的载荷时间历程以及列车运行速度信息,以ISO 281：2007标准方法为基础,研究结合损伤的轴承寿命预测方法。同时也分析动车组轴箱轴承复杂的受载特性,给出将所测弹簧和转臂载荷近似转化为轴承的径向和轴向载荷的方法;计算轴箱轴承在实际运行的复杂载荷下不同可靠度的预测寿命,并与传统ISO标准方法计算结果进行对比,结果表明该预测方法相对保守,偏于安全;另外,计算低速进出库路段轴承疲劳寿命,其寿命比正常高速运行小很多,从损伤角度来看,动车组轴箱轴承低速进出库比正线高速运行的每公里损伤值更大;结合不同工况百分占比,给出轴承预测寿命,结果表明该寿命预测方法合理,可用于指导高铁轴箱轴承设计以及相关理论研究。     

Application of an envelope technique in the detection of ball bearing defects in a laboratory experiment

To judge the diagnostic capabilities of an envelope technique, based on enveloping the resonance frequency of a transducer,

1 Bearcon Signature™, Carl Schenck AG, Germany

artificially damaged ball bearings (SKF 6207) were run under oil lubrication at different radial loads and speeds in a laboratory experiment. Damage to the outer race, inner race and ball of different magnitudes was introduced by spark erosion and the response of the measurement system was analysed. The results showed that vibration spectrum components of outer race defects showed up in the envelope spectra of undamaged bearings, and that the detectability of defects was primarily limited by the speed of the bearing; on occasion the automatic scaling facility of the analyser was a limiting factor. Inner race and ball defects showed the well-known effects of load modulation in the defect contact zone, which can become dominant in the envelope spectra at high loads and speeds. This phenomenon could be confirmed by computer simulation. The detection of ball damage was hampered by the fact that overrolling of the defect in purely radially loaded bearings takes place incidentally. This drawback could be mitigated by applying a trigger technique to the envelope signal.     

Wear properties of DLC-coated steel rollers running with highly contaminated lubrication

The presence of hard contaminants in lubrication can lead to the premature failure of rolling bearings. To reduce the negative effect of such contaminants, hard carbon-based coatings (diamond-like carbon; DLC) can be applied to the surfaces of steel bearings. DLC coatings generate a low friction and a high sliding wear resistance to enhance the tribological properties and improve the durability of running components. This work explores the merits of DLC coatings for use in very demanding applications, such as in highly contaminated environments. The wear properties of DLC-coated bearing rollers were evaluated by comparing them with uncoated rollers. The degree of wear found on the coated rollers was serious, especially under relatively high contaminant concentrations. The three-body abrasive wear produced a relatively coarse scoring of the coating surface, which caused the corresponding disc to suffer more damage than the disc running against an uncoated roller under the same operating conditions. The results indicate that supposedly wear-protective coatings cause even more damage to running surfaces once they have been broken up by hard contaminants, and highlight the importance of keeping the bearing coating intact. In practise, it is important to eliminate contaminants from the lubricant of rolling bearings, in particular for bearings with a DLC anti-wear coating.     

Appearance of craters on track surface of rolling element bearings by spark erosion

A theoretical investigation has been carried out to determine the time span for the appearance of craters by spark erosion on the track surfaces of rolling-element bearings operating under the influence of shaft voltages. An analytical model has been developed using the continuum theory of Griffith to determine energy per unit area required for the development of craters on the track surfaces. Also, an expression is deduced for the net energy transmitted per unit area on the track surfaces by the leakage of stored charge energy resulting in the appearance of craters under the effect of shaft voltage and bearing capacitance depending on operational and dimensional parameters of a bearing in a given span of operation. By the formulation of capacitive stored energy in a bearing using high resitivity lubricant, along with the developed model and expressions using the ratio of cycles to accumulate and discharge of the accumulated charge energy at the various levels of bearing to shaft voltage, the time span/cycles for the appearance of craters of specified dimensions by spark erosion has been determined. Matching time span/cycles has been ascertained by the investigation of a case history of the diagnosis of bearings that failed by crater formation. The analysis can also be used for determination of shaft voltage if the time span/cycles for the formation of known size craters and bearing capacitance are established.     

Development of Seals for Rocket Engine Turbopumps

An investigation was conducted to determine the effect of frequency and amplitude of axial vibration and of bearing axial play in producing fretting damage in unlubricated ball bearings at constant temperature and humidity. A study was also made of the impact forces occurring within the bearings due to these vibrations. A simplified analog simulation model of the ball bearing and the vibration exciter system was also developed.

Frequency, amplitude, time, and a derived parameter GxI (the product of acceleration and impact frequency) had a very significant influence on fretting damage, indicated statistically at a confidence level of ninety-nine percent. Although axial play had little effect on fretting damage for the range of axial plays of the test bearings, it had significant effect on the acceleration levels obtained within the bearings. Fretting damage was measured with a bearing torque analyzer. The experimental test vibrations were accurately reproduced on the analog model.     

A study of electrical pitting of journal bearings with water‐contaminated lubricant

The investigations reported in this paper concern the effect of the use of a degraded lubricant on bearing life. A diagnosis of the premature failure of the hydrodynamic journal bearings of a synchronous condenser has been carried out. The surface of the failed bearings has been examined and the cause of the failure investigated. A theoretical analysis has also been undertaken to calculate the number of cycles that take place before failure occurs. The number of cycles thus established matched that of the cycles/duration of operation before the premature failure of the bearings. The process leading to the premature failure and the role of the degraded lubricant have been identified. Remedial measures have been successfully implemented to reuse the existing bearings. Measures have been suggested to avoid repeated failures. The theoretical analysis has the potential to ascertain the shaft voltage once the severity of the physical damage on the liner surface of the bearing and the duration of its operation have been established.     

Effect of operating parameters on the threshold voltages and impedance response of non-insulated rolling element bearings under the action of electrical currents

In the present work, the effects of operating parameters on the threshold voltages and impedance response of non-insulated rolling element bearings under the influence of varying levels of electrical currents have been studied. The voltage-current relationships in the bearings have been established.Investigations reveal that first and second threshold voltages appear under the influence of electrical currents in the bearings, depending on the lubricant resistivity, oil film thickness, bearing conditions and the operating parameters. The detected threshold voltages are primarily responsible for momentary flow of current and the further increase in current intensity with a slight change in potential drop across the bearings. The impedance of the bearings becomes negligible as the current intensity across the bearing increases. However, the impedance is more affected by the speed and film thickness than by the load on the bearings.This paper highlights the mechanism of the process of failure of the bearings, using lubricants with different characteristics. The investigations show that the experimentally evaluated threshold voltage coefficients of the bearings, using high resistivity lubricants, increase with speed and are independent of the loads on the bearings. This behaviour of the threshold coefficients of the bearings is used to predict the threshold voltages at different parameters of operation. However, bearings using low resistivity lubricants do not display the threshold voltage phenomenon.The investigation may also be used to determine the safe levels of potential drop across the bearing elements, to avoid damage of the bearings under different operating parameters and also to assess the film thickness by the measured impedance and current intensity response of the bearings.     

Electrical resistivity and conductivity of greases: An initial study

Investigations of railway wagons fitted with rolling‐element bearings have shown damage to the bearings from the passage of electric current. This also occurs in railway wagons without an electric energy consumption of their own, because of residual currents from electric locomotives. This phenomenon gives rise to technical, financial, and even safety problems. This paper reviews research in the field of rolling‐element bearings exposed to electric currents. The paper also reports on an ongoing study undertaken to understand the mechanism of current flow and the role of lubricants in the associated damage, and to identify the possibilities of minimising bearing damage. The obvious solution to this problem is to use optimised greases, i.e., with high electrical conductivity and good lubricating ability. In the preliminary work reported here a number of greases for railway use were tested to determine their electrical conductivity in static and dynamic situations. These tests were performed using specially designed apparatus, and significant initial information about the electrical properties of greases has been obtained in this research, for example, that there is a correlation between the electrical conductance under static and dynamic conditions. All the greases tested showed comparatively high resistivity values, which could be one explanation for the bearing damage observed.     

Current Status of Hybrid Bearing Damage Detection

Advances in material development and processing have led to the introduction of ceramic hybrid bearings for many applications. The introduction of silicon nitride hybrid bearings into the high-pressure oxidizer turbopump on the space shuttle main engine led NASA to solve a highly persistent and troublesome bearing problem. Hybrid bearings consist of ceramic balls and steel races. The majority of hybrid bearings utilize Si₃N₄ balls. The aerospace industry is currently studying the use of hybrid bearings and, naturally, the failure modes of these bearings become an issue in light of the limited data available.

In today's turbine engines and helicopter transmissions, the health of the bearings is detected by the properties of the debris found in the lubrication line when damage begins to occur. Current oil debris sensor technology relies on the magnetic properties of the debris to detect damage. Because the ceramic rolling elements of hybrid bearings have no metallic properties, a new sensing system must be developed to indicate the system health if ceramic components are to be safely implemented in aerospace applications. The ceramic oil debris sensor must be capable of detecting ceramic and metallic component damage with sufficient reliability and forewarning to prevent a catastrophic failure.

The objective of this research is to provide a background summary on what is currently known about hybrid bearing failure modes and to report preliminary results on the detection of silicon nitride debris in oil using a commercial particle counter.     

Resistance to wear and cavitation erosion of bearing alloys

Sliding wear and vibratory cavitation erosion tests in paraffin oil were carried out on bearing alloys, i.e. tin-based and lead-based white metals, Cu-Pb alloy and leaded bronze. In lubricated wear under mild conditions the surface is worn smooth and a slight difference exists between the wear resistances of the four alloys. In cavitation erosion an eroded surface which is much rougher than the worn surface is formed. Cavitation erosion is affected strongly by the composition and crystal structure of the alloy and thus the erosion resistances of the four alloys differ greatly, the ranking of resistance being lead-based white metal < Cu-Pb alloy < tin-based white metal < leaded bronze. The surface damage, which is caused by the joint action of cavitation erosion and wear, was also investigated by rubbing the eroded surfaces which had been exposed to cavitation erosion for various times. This damage becomes larger with increasing cavitation damage. The resistance to this damage differs much more in the four alloys tested and tends to correlate with the results of the erosion tests rather than those of the wear tests. Therefore, it is clear that the cavitation erosion resistance should be considered in the selection of bearing materials.     

Analysis of skid damage to cylindrical roller bearing of mainshaft of aeroengine

Journal of Mechanical Science and Technology - Skid damage to mainshaft bearings on aeroengines severely reduces aircraft reliability. In this study, a batch of cylindrical roller bearings...     

粉碎机械用推力角接触球轴承的设计改进

随着科技的发展,对粉碎机械的寿命提出更高的要求。作为粉碎机械重要零件之一的推力角接触球轴承的寿命问题,也逐渐得到重视。对该系列轴承的常见损坏原因作出了分析,并提出了解决办法。     

Diagnostics of rolling-element bearing condition by means of vibration monitoring under operating conditions

Many investigations have been made of the correlation of diagnostic parameters with stress and damage in rolling-element bearings. It was found that parameters normalised to zero conditions are more suitable for diagnostic purposes than time-dependent absolute values. A new superior diagnostic parameter can be simply determined.