Optimum design of hydrostatic journal bearings Part II. Minimum power

The optimization problem is formulated with a view to maximizing the load-carrying capacity of hydrostatic journal bearings. Equations governing the performance of multi-recess hydrostatic journal bearings are summarized. Practical design limits and operational constraints are also defined. The optimization process is based on the well known Rosenbrock method. Results illustrating the effect of area ratio, axial land width and circumferential land width on load capacity, flow rate and power ration are reported. In conclusion precision bearings with small clearances and low pressure ratios are recommended for applications involving low supply pressures, while bearings with large clearances and pressure ratios close to 0.5 are recommended for applications involving high supply pressures     

Optimum design of hydrostatic journal bearings Part I: Maximum load capacity

The optimization problem is formulated with a view to maximizing the load-carrying capacity of hydrostatic journal bearings. Equations governing the performance of multi-recess hydrostatic journal bearings are summarized. Practical design limits and operational constraints are also defined. The optimization process is based on the well known Rosenbrock method. Results illustrating the effect of area ratio, axial land width and circumferential land width on load capacity, flow rate and power ration are reported. In conclusion precision bearings with small clearances and low pressure ratios are recommended for applications involving low supply pressures, while bearings with large clearances and pressure ratios close to 0.5 are recommended for applications involving high supply pressures     

The dynamic behaviour of fluid bearings with grooved lands

In mechanical engineering, grooved mating lands are used for various reasons in a large number of bearing applications. This paper studies the effect of such grooves on the squeeze load characteristics, and hence on the damping capacity, of bearings. A comparison is given between the damping capacity of bearings with grooved lands and that of bearings with equivalent flat lands to give the same pressure flow characteristics. Different bearing configurations, representing thrust and journal applications, are analysed and discussed.     

Low friction rolling element bearings

In this paper some unusual designs of rolling element bearings are discussed, with a view to reducing the friction to a minimum by optimizing their shape. Such bearings may have use in certain applications where low friction is important, some applications envisaged being radar antennae and gyroscope gimbals.     

Fluid Flow Analysis for Friction Torque around Rolling Element in Ball Bearings

Ball bearings (e.g., deep-groove, angular-contact, and roller bearings) support loads in a rotor system and provide lubrication between the shaft and housing. The deep-groove ball bearings used in a turbopump do not differ significantly from angular-contact ball bearings or the bearings found in other applications. Deep-groove ball bearings consist of rolling elements, an inner raceway, an outer raceway, and a retainer to guide the rolling elements. In ball bearings, the resistive (churning or drag) forces and torques acting on the rolling elements and raceways are affected by the fluid flow rate and direction, as well as the rotational speed. These churning and drag forces and torques affect the internal dissipation or power losses into the bearing, which become very significant for high-speed applications. This study numerically investigated the characteristics of the flow conditions for deep-groove ball bearings, with a particular focus on the friction distribution on the rolling elements. A simple analytical model of the fluid flow inside a ball bearing was developed using a computational analysis, and the flow characteristics at high rotational speeds are presented.     

Measurement of small forces with superconducting magnetic bearings

Superconducting bearings promise superior performance in certain scientific and technological applications. One application is in an orbital equivalence principle experiment, where linear bearings of extreme smoothness and small friction are required     

Externally pressurized gas bearings: A review

The literature pertaining to externally pressurized hole admission gas bearings is briefly reviewed. The advantages, limitations and applications of such bearings under various design conditions are discussed.     

Elastic Orifices for Pressurized Gas Bearings

The merit of using an elastic orifice compensator in externally pressurized gas bearings is examined. The use of an elastic orifice in a test bearing demonstrates an increase in bearing stiffness over a conventional fixed orifice when compared at a common operating point. This attribute should be welcome wherever externally pressurized bearings are used. In addition, increased bearing stiffness may allow the use of these bearings in applications formerly restricted to pressurized liquid and rolling contact bearings. Information is included to allow construction of working models of these orifices and duplication of experimental results.     

Some aspects of rolling friction resistance in a complex tribological pair – the bicycle wheel bearing

Bicycles are an important means of transport — over 20 million are manufactured worldwide each year, and, because their source of motive energy is human, their energy conversion, as measured by their resistance to motion, is critical. The bearings used in bicycles are rolling bearings, but are normally of different materials and construction quality to the roller bearings used in other applications. The present paper is intended to provide an indication of the phenomena influencing the resistance to motion and loss of energy of these bearings, and is based on a rolling bearing test stand designed by the author. A mathematical model derived from experimental observation is presented, and the theoretical results compared with experimental results.     

Externally Pressurized Spherical Gas Bearings

Spherical gas-lubricated bearings are of considerable interest in applications requiring a pivoting or rotating support with three degrees of freedom, for instance hi attitude control simulators of space vehicles. An analytical and experimental study of externally pressurized spherical gas bearings with orifice regulation is presented along with the experimental findings, which are in good agreement with the predictions of the viscous flow theory.     

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.     

Theoretical analysis of two configurations of aerostatic flat pad bearings using pocketed orifice restrictors

Aerostatic flat pad bearings are finding increased applications in high-precision machine tools, high-performance measuring equipment and coordinate measuring machines. To date, much of the development of these bearings has been of an empirical nature since there are no detailed design procedures for assisting designers to optimize their designs^1,2. In the field of aerostatic journal bearing design, comprehensive procedures do exist. The object of this paper is to exploit the principles developed for the analysis of aerostatic journal bearings to the area of flat pad bearings, which are more widely used in industrial situations. In this paper, similar analysis tools are developed and are used to obtain design performance data for a number of flat pad bearing configurations. These data include load, flow and stiffness parameters, all of which are fundamental to design optimization.     

Levitation of passive magnetic bearings and systems

Passive magnetic bearings and their systems are studied with reference to their instability, which reduces their utilisation in technical applications, where the absence of friction and wear, that magnetism allows, would be very important. This study is based on the calculus of the forces acting on magnetic bearings and on their systems, and on the identification of areas of low instability.     

Bearing materials for small electric motors

Operation of small electrical machines with bearings under boundary lubrication conditions does not receive much attention in the literature. Yet there are some fifty million fhp (fractional horsepower) induction motors made every year. This article outlines the bearing types used in these motors and examines a new polymer lined bearing which seems attractive for many applications using sleeve or ball bearings     

Lower bainite bearings for adverse environments

The conventional heat treatment processes used in the manufacture of rolling bearings are normally specified to produce a martensitic structure in high carbon bearing steel. An alternative process in which lower bainite is produced offers a tougher steel which is particularly advantageous in conditions where lubrication is poor. The improved performance of lower bainite bearings in mine conveyor applications and where fire-resistant fluids are used as lubricants is discussed in this paper.     

圆锥滚子轴承外圈过盈配合量对装配高的影响

以33118圆锥滚子轴承为例,介绍了传统轴承过盈配合量与装配高变化量关系的数值计算方法,经与测量结果对比,误差较大(32％).分析其主要原因为计算中将壳体、外圈等效转化为规则圆环,与实际情况不符,故建立包含壳体、轴承实际结构的有限元模型,计算轴承过盈配合量与装配高变化量的关系,与测量结果误差为2.9％,可以满足工程应用...     

多孔质含油轴承的理论研究进展

概述了流体在多孔基体中的流动特性和多孔质含油轴承的理论计算模型。分析了多孔质含油轴承的润滑机理、多孔质材料的特性、3种动量方程模型。对应用于多孔质含油轴承的理论计算方程，指出了应用条件、数值求解方法。含油轴承在多种影响因素下的耦合计算对于工程应用有一定的指导意义。     

Plain bearing options for pumps

Pump applications demand a wide range of bearing designs. In this article, Guy Pethybridge (Product Manager) and Nigel New (Product Development) of Waukesha Bearings focus on hydrodynamic bearings, considering how factors such as operating temperature, load and lubricant influence the choice of bearing material. In particular, the characteristics and benefits of polymer bearings are highlighted.     

工业应用型永磁悬浮轴承关键技术

提出了一种新的工业应用型永磁悬浮轴承,对其工作机理进行了详细的分析,并论述了要解决永磁悬浮轴承工业应用的几个关键设计技术问题,即永磁悬浮轴承承载能力、刚度和安装维护等达到工业应用要求的设计技术问题、永磁悬浮轴承-转子系统动力学特性达到工业应用要求的设计技术问题,以及永磁悬浮轴承的标准化、系列化达到工业应用要求的设计技术问题。拟定了设计方案并对其进行了可行性分析,为永磁悬浮轴承像滚动轴承一样在工业上得到普遍应用奠定了理论基础。     

Self-lubricating polymer cages for space-proofed bearings: performance and roundness

For applications in space mechanisms, rolling element bearings with special polymer cages have been developed. The dependence of the properties of these bearings on deviations from roundness of their retainers is investigated and related to mechanical and thermal treatment of the cages before assembly of the bearing. An application to a production lot is shown and the observed effects are discussed. The results are then used to define a procedure that allows a control of the roundness.