氮化硅陶瓷滚子轴承的抗断油能力试验

为了对比分析钢制滚子轴承和混合陶瓷滚子轴承的抗断油能力,分别对8Cr4Mo4V钢和氮化硅2种圆柱滚子轴承进行了断油试验。结果表明:在相同工况下,混合陶瓷滚子轴承外圈温升和主机电流均小于全钢轴承,其抗断油能力远优于全钢轴承。     

氮化硅陶瓷滚子轴承的高速性能试验

为了对比分析普通钢制滚子轴承和混合陶瓷滚子轴承的高速性能,对套圈材料为8Cr4Mo4V、保持架材料为铝青铜、滚子材料分别为8Cr4Mo4V钢和氮化硅的2种轴承进行了试验。结果表明:在相同工况下,混合陶瓷滚子轴承不仅高速性能远优于全钢轴承,且功率消耗明显低于全钢轴承。     

混合型氮化硅陶瓷轴承的新进展

1　氮化硅陶瓷球的加工[1]这里介绍一种新的研磨方法—磁悬浮研磨法(Ｍａｇｎｅｔｉｃｆｌｏａｔｐｏｌｉｓｈｉｎｇ ,简称ＭＦＰ) ,氮化硅毛坯球置于磁流体 (通常是胶态Ｆｅ3 Ｏ4 )、磨料及水混合物中 ,在磁场作用下 ,磁性粒子向强磁场方向运动 ,对磨料产生反向浮力 ,给处于上研磨板 (如丙烯醇系有机板材 )与无磁钢下研磨板之间的氮化硅陶瓷球以压力 ,这个压力较小 ,约为 1Ｎ 球 ,而且是弹性的 ,无磁钢研磨板转动时 (转速 1 0 0 0～ 1 0 0 0 0ｒ ｍｉｎ) ,氮化硅球在磁悬浮流体中被磨料研磨。由于采用高速研磨 ,研磨过程中施加于球的压力小…     

航空发动机主轴轴承断油性能试验

在专用轴承试验机上,按试验大纲给定的试验条件,对８Ｄ１０３２９２０ＮＱ１ 轴承进行断油性能试验。结果表明,该轴承有较强的抗断油能力。介绍了该试验的主要设备、试验条件和方法,并获得了大量有价值的试验数据。附图２幅,表６ 个。     

水润滑陶瓷轴承的试验研究

使用Ｓｉａｌｏｎ，ＺｒＯ２和Ａｌ２Ｏ３陶瓷材料，进行了水润滑条件下的滚动轴承和滑动轴承的试验研究，比较和分析了各种陶瓷材料的疲劳和磨损特性，滚动轴承中Ｓｉａｌｏｎ球的寿命最长，Ａｌ２Ｏ３球的寿命最短，滑动轴承试验中Ｓｉａｌｏｎ的摩擦系数最小，而ＺｒＯ２的磨损较大，借助扫描电子显微镜和Ｘ射线能谱分析讨论了陶瓷的疲劳和磨损机理。     

国外氮化硅陶瓷轴承的发展概况

随着现代工业的迅速发展,迫切需要大量的在高速、高温和腐蚀介质环境下工作的轴承。目前用轴承钢制造的在特殊工况下工作的轴承,其最高使用温度只有550℃,在高速运行和腐蚀介质下的使用寿命极短,远远不能满足现代高新技术及其工业发展的需要。而陶瓷材料具有作为轴承的理想特性,     

高速陶瓷滚子轴承可靠性分析

本文提出了高速陶瓷滚子轴承可靠性分析的基本思路，论证了Ｌｕｎｄｂｅｒｇ—ｐａｌｍｇｒｅｎ疲劳理论在陶瓷滚子轴承疲劳分析中的正确性．结合疲劳破坏及磨损失效两方面因素，提出了评价陶瓷滚子轴承可靠性的数学模型。由模型进行实例计算，说明陶瓷滚子轴承较钢滚子轴承有较高可靠性。     

基于油雾润滑的高速电主轴断油性能试验研究

对基于油雾润滑的高速电主轴进行断油性能试验,利用B&K声学/振动分析系统、红外热像仪等仪器对断油过程中高速电主轴系统的振动特性、主轴轴承内部的润滑、电主轴表面的温度场等状态参数进行监测,并与正常油雾润滑时高速电主轴的状态参数进行比较,分析研究了断油状态对高速电主轴工作性能的影响.试验结果表明:高速电主轴正常工作时主轴轴承所需要的润滑油量很少;短时间断油对电主轴系统的正常运行状态影响不大,主轴轴承内部的润滑、电主轴系统的振动特性和电主轴的热状态等性能参数能够维持在基本正常的水平.     

轴承用理想材料—氮化硅陶瓷

本文就氮化硅陶瓷用作轴承材料进行了评述，介绍了氮化硅的性能和制造方法、氮化硅滚动轴承的制造以及保证质量的措施等。     

An Experimental and Theoretical Study of Hybrid Bearing Micropitting Performance under Reduced Lubrication

Hybrid bearings—that is, bearings with ceramic rolling elements and steel rings—are often used in applications with reduced (i.e., boundary or mixed) lubrication conditions. The mechanisms by which hybrid bearings perform significantly better than full-steel ones in these cases are so far unclear, although a number of published works have shown experimental results in which appreciable performance benefits were obtained by the use of hybrid bearings under boundary or mixed lubrication. In this article, the reduced lubrication performance of hybrid rolling contacts, versus full-steel ones, is studied in detail by means of rolling bearing fatigue experiments and a theoretical micropitting model. It is found that the large improvement in surface fatigue resistance of hybrid contacts cannot be explained solely on the basis of the unavoidable differences in some of the roughness parameters existing between the full-steel and hybrid contacts. It is also necessary to take into account a considerable reduction in the effective boundary friction coefficient of the hybrid contact. In the numerical micropitting simulations it was found that the boundary friction coefficient of a hybrid contact must be about two times lower than that for the corresponding full-steel contact, in order to be able to predict the experimental observations reasonably well. A similar ratio of the boundary friction coefficients was obtained in a number of dedicated tests, thus confirming the results of the micropitting model. The mechanisms of the strong micropitting resistance of hybrid bearings under reduced lubrication conditions are discussed in detail, shedding new light on the operational tribology and performance capabilities of bearings with rolling elements made of silicon nitride ceramics.     

Effect of Silicon Nitride Balls and Rollers on Rolling Bearing Life

Three decades have passed since the introduction of silicon nitride rollers and balls into conventional rolling-element bearings. For a given applied load, the contact (Hertz) stress in a hybrid bearing will be higher than that of an all-steel rolling element bearing. The silicon nitride rolling-element life as well as the lives of the steel races were used to determine the resultant bearing life of both hybrid and all-steel bearings. Life factors were determined and reported for hybrid bearings. Under nominal operating speeds, the resultant calculated lives of the deep-groove, angular-contact, and cylindrical roller hybrid bearings with races made of post-1960 bearing steel increased by factors of 3.7, 3.2, and 5.5, respectively, from those calculated using the Lundberg-Palmgren equations. An all-steel bearing under the same load will have a longer life than the equivalent hybrid bearing under the same conditions. Under these conditions, hybrid bearings are predicted to have a lower fatigue life than all-steel bearings by 58% for deep-groove bearings, 41% for angular contact bearings, and 28% for cylindrical roller bearings.     

The Performance of a Hybrid Ceramic Ball Bearing Under High Speed Conditions with the Under-Race Lubrication Method

Large bore (150 mm) hybrid ceramic ball bearings and all-M50 steel bearings were tested with under-race lubrication to compare the heat generation and the temperature rise at speeds up to 2.25 million DN. Furthermore, oil shut-off tests were carried out with both bearings over 2.25 million DN.

The experimental results of the heat generation for both bearings were nearly the same at an axial load of 19.6 kN. at 34.3 kN, the heat generation of the hybrid bearing was lower than that of the M50 steel bearing at low speed. The heat generation of both bearings gradually approached each other with increasing speed and became nearly equal at a speed of 15,000 rpm. The survivability of the hybrid bearing in the oil shut-off test was superior to that of the M50 bearing. These experimental results were explained by the calculation results using a computer analysis software which simulates the kinematics and the performance of ball bearings.     

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.     

Silicon Nitride Boundary Lubrication: Lubrication Mechanism of Alcohols

This paper describes the lubrication mechanism of alcohols with silicon nitride under boundary lubrication conditions. Dynamic wear tests and static chemical reaction studies were conducted to study the chemical interaction between alcohols and silicon nitride. Direct evidence of chemical reactions occurring between alcohols and silicon nitride was collected. Gel-permeation-chromatography-graphite-furnace-atomic-absorption (GPC-GFAA) analysis detected the presence of high molecular weight (HMW), silicon-containing, metallo-organic compounds in the wearing contact. Secondary ion mass spectrometry (SIMS) analysis of the reaction products from wear tests revealed the formation of silicon alkoxides. These alkoxides subsequently reacted to form HMW products which had been independently verified as capable of lubricating silicon nitride surfaces. A two-ball collision test was used to verify the lubricating quality of the film generated from the wear test. A lubrication mechanism is proposed in which alcohols adsorb and react with the oxide/hydroxide layer of Si₃N₄ to produce a bonded surface silicon alkoxide. Subsequent tribochemical reactions prompted by the surface disruption from the wearing contact cause the formation of free silicon alkoxides. These species then proceed to form a variety of silicon-containing high molecular weight products that have demonstrable lubricating ability. This mechanistic understanding provides a framework of Si₃N₄ lubrication.     

高速主轴轴承油气润滑的应用试验

高速主轴轴承油气润滑技术在国外一些工业化国家早已得到广泛应用。本文对高速主轴轴承油气润滑技术的应用进行了比较系统的试验研究，并与油雾润滑进行了对比应用试验。     

Fatigue Behavior of Hybrid Ceramic Ball Bearings in Liquid Nitrogen

Hybrid ceramic ball bearings, which are composed of silicon nitride (Si₃N₄) balls, ANSI 440C stainless steel rings and PTFE based composite retainers, are tested at high speed and heavy loading in cryogenic conditions. The rolling contact fatigue behavior of steel rings and ceramic balls in liquid nitrogen is analyzed. In addition, four-ball fatigue testing was done at room temperature with oil lubrication. The crush load of ball against ball in liquid nitrogen, which directly relates to the inner quality of the balls, is also evaluated. The results show that the spalling of silicon nitride balls, rather than micro pitting on the steel raceways, is the main cause for the failure of the hybrid ball bearings in liquid nitrogen. The fatigue mechanism of the ceramic balls is similar to that of ceramic balls at room temperature, but the characteristics of crack propagation are different because of differences between the cryogenic liquid medium and oil. Although most of the fatigue cracks originated from internal defects within the ceramic balls, the silicon nitride balls exhibit a high load capacity. When silicon nitride balls are loaded against steel balls, the steel balls are crushed while the silicon nitride balls do not exhibit plastic deformation. When ceramic balls with a 11.113 mm diameter are loaded against each other, crushing takes place at a nominal contact stress of 27～29 GPa.     

Correlating Computerized Rolling Bearing Analysis Techniques to the ISO Standards on Load Rating and Life

Computer-aided design of bearing systems is finding its way into many industrial sectors requiring high reliability and trouble-free performance from rotor/bearing systems. This trend will accelerate as more bearing analysis codes are ported to the personal computer and incorporate user-friendly interfaces. This paper describes and explains the theoretical basis for bearing load rating and life estimating as reflected in such programs. The calculation of individual bearing and system B-10 Fatigue Life and their correlation to the ISO International Standard 281 for dynamic load ratings and rating life is presented. Showing the continuity from the standard methods to the more fundamental computer analysis of bearing systems will allow for a smooth transition from one to the other.     

Lubrication Analysis of a Connecting-Rod Bearing in a High-Speed Engine. Part II: Lubrication Performance Evaluation for Non-Circular Bearings

In this article a numerical investigation of a connecting rod bearing operating at 6,500 rpm is performed. This is a companion to an earlier article that took into account the effects of the inertial force and the variable bolt tension force, which are considered to be the principal factors that affect the connecting rod bearing lubrication characteristics of an engine running at high speed. It was found that a thinner minimum oil film and a larger peak hydrodynamic pressure are predicted in a deformed connecting rod bearing than in a rigid connecting rod bearing. Multi-peaked hydrodynamic pressure was found to appear as well because of two or more converging-diverging film regions.     

Effect of Rolling Bearing Refurbishment and Restoration on Bearing Life and Reliability

For nearly four decades it has been a practice in commercial and military aircraft application that rolling-element bearings removed at maintenance or overhaul be reworked and returned to service. The work presented extends previously reported bearing life analysis to consider the depth (Z₄₅) to maximum shear stress (τ₄₅) on stressed volume removal and the effect of replacing the rolling elements with a new set. A simple algebraic relationship was established to determine the L₁₀ life of bearing races subject to bearing rework. Depending on the extent of rework and based on theoretical analysis, representative life factors for bearings subject to rework ranged from 0.87 to 0.99% of the lives of new bearings. Based on bearing endurance data, 92% of the bearing sets that would be subject to rework would result in L₁₀ lives equaling and/or exceeding that predicted for new bearings, with the remaining 8% having the potential to achieve the analytically predicted life of new bearings when one of the rings is replaced at rework. The potential savings from bearing rework varies from 53 to 82% that of new bearings depending on the cost, size, and complexity of the bearing.