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Report discusses application of cepstral analysis to diagnosis of wear in ball-bearing cages in rotating machinery. Ball-cage vibrations and changes in vibrations symptomatic of wear is detected earlier in test than by more conventional methods based on strain-gauge measurements. Particularly useful in diagnoses of gearboxes and rolling-element bearing.
Strain-gauge signals at harmonics of ball-bearing-cage frequencies signify wear. Brief report describes experiments in continuing effort to interpret vibrations of machinery in terms of wear in ball bearing.
Parched Elasto Hydrodynamic Lubricant (PEHL) film thickness in a large instrument ball bearing is measured by electrical capacitance across its ball set. Correlation is shown between changes in film thickness and changes in Basic Speed Ratio (BSR) measured at the same time. BSR is confirmed as a sensitive, non-intrusive measure of transients in film thickness in a real bearing.
Combination of basic and advanced techniques yields new capability for inspection. In new technique, surface first inspected with fluorescent penetrant dye to reveal flaws. Ruby ball of known diameter placed near flaw having to be measured. Flaw and ball observed through magnifying video system that can "freeze" image.
Self-lubricating bearing system withstands highly corrosive environment of wastewater-recycling unit. New bearings contain cobalt-based-alloy balls and races, graphite/polyimide polymer ball cages, and single integral polytetrafluoroethylene seals on wet sides. Materials and design prevent corrosion by acids and provide lubrication.
Ball lenses used to collimate and focus pump light from array of diode lasers onto input face of solid-state laser. Experiments show ball lenses perform as well as, or better than, multiple-element lenses supplied heretofore as parts of commercial arrays of diode lasers. Offers advantages of relative simplicity and ease of fabrication, lower cost, lower weight, and less sensitivity to misalignment.
A parametric experimental investigation of an 85 millimeter bore angular contact ball bearing running in RP-1 fuel was performed at speeds of 10000 to 24000 RPM. Thrust loads were varied from 4450 to 17800 Newtons (1000 to 4000 lbs.). Radial loads were varied from 1335 to 13350 Newtons (300 to 3000 lbs.). RP-1 lubrication for the bearing was provided through a stationary jet ring located adjacent to the test bearing outer ring. Increases in both the thrust and radial loads resulted in increased bearing temperature, while increases in shaft speed resulted in much more dramatic increases in bearing temperature. These trends are typical for ball bearings operating under these types of conditions. Results are given for outer ring temperatures of the test bearing at the various test conditions employed. In addition, the heat energy removed from the bearing by the RP-1 was determined by measuring the increase in temperature as the RP-1 passed through the bearing. Results showed that the amount of heat energy removed by the RP-1 increased with both shaft speed and RP-1 flow rate to the bearing.
Flame-balls are stationary spherical premixed flames observed in certain near-limit mixtures. It is believed that radiative heat losses are an important stabilizing influence. Numerical solutions of flame balls are constructed for hydrogen-air mixtures using an accurate description of the chemical kinetics, diffusive transport, and radiation losses. A lean limit equivalence ratio of 0.0866 is predicted and a rich limit of 2,828. For any equivalence ratio between the two limits there are two solutions. One is characterized by a small flame, incomplete reactant consumption, and negligible radiation losses. The other by a large flame, complete consumption of one of the reactants, and significant radiation losses. The maximum temperature varies between 1200 and 900 K as the two solution branches are traversed. Much of our discussion is a reprise and modification of previously published analytical results, for these provide physical insight into the nature of the solutions, and suggest that a portion of the large flame branch near the lean limit is stable and so corresponds to observable flames.
A parametric experimental investigation of an 85 millimeter bore angular contact ball bearing running in RP-1 fuel was performed at speeds of 10,000 to 24,000 rpm. Thrust loads were varied from 4450 to 17,800 Newtons (1000 to 4000 lbs.). Radial loads were varied from 1335 to 13,350 Newtons (300 to 3000 lbs.). RP-1 lubrication for the bearing was provided through a stationary jet ring located adjacent to the test bearing outer ring. Increases in both the thrust and radial loads resulted in increased bearing temperature, while increases in shaft speed resulted in much more dramatic increases in bearing temperature. These trends are typical for ball bearings operating under these types of conditions. Results are given for outer ring temperatures of the test bearing at the various test conditions employed. In addition, the heat energy removed from the bearing by the RP-1 was determined by measuring the increase in temperature as the RP-1 passed through the bearing. Results showed that the amount of heat energy removed by the RP-1 increased with both shaft speed and RP-1 flow rate to the bearing.
The rolling-contact fatigue spin rig was used to test bails of a bearing steel at maximum Hertz stresses of 600,000 to 750,000 psi. The effect of fiber orientation was observed with the ball track restricted to passing directly over the poles, coincident with the equator, or randomly around the ball. The polar areas were found to be weaker in fatigue than the nonpolar areas. This resulted in a much greater portion of the failures occurring in the polar areas than would be expected from a homogeneous material. The early failures are discussed.
Ball bearing carrying transient axial loads at beginning and end of operation of turbopump modified to reduce wear during normal steady operation, according to proposal. Bearing forced into normal contact by flow of pumped fluid during high-speed operation. Modification intended to reduce influence of fluid in making balls spin and to apply enough axial load to ensure normal rolling contact with races. Three main features of design: narrow-gap clearance (labyrinth) seal between shaft and inner race, narrow-gap clearance seal between inner and outer races, and extension of inner race to enlarge its upstream-facing area.
A high-speed, reliable ball bearing has been designed for at least fifteen years of operation in space effectors, MWA's, and RWA's. Advanced bearing concepts have been used in this design, such as: no ball retainer, which eliminates all retainer-related problems; an external lubricazing system that will supply the lubricant at a specified flow rate; and a cartridge assembly that will allow the instrument user to purchase a ready to use bearing assembly, with lubricator. Currently, two assemblies are on life test at 12,000 RPM and have accumulated over 20,000 hours each, with consistent low-torque losses. This paper will describe each of the salient features.
The potential capabilities and limitations of single ball lenses for coupling laser diode radiation to single-mode optical fibers have been analyzed; parameters important to optical communications were specifically considered. These parameters included coupling efficiency, effective numerical apertures, lens radius, lens refractive index, wavelength, magnification in imaging the laser diode on the fiber, and defocus to counterbalance spherical aberration of the lens. Limiting numerical apertures in object and image space were determined under the constraint that the lens perform to the Rayleigh criterion of 0.25-wavelength (Strehl ratio = 0.80). The spherical aberration-defocus balance to provide an optical path difference of 0.25 wavelength units was shown to define a constant coupling efficiency (i.e., 0.56). The relative numerical aperture capabilities of the ball lens were determined for a set of wavelengths and associated fiber-core diameters of particular interest for single-mode fiber-optic communication. The results support general continuing efforts in the optical fiber communications industry to improve coupling links within such systems with emphasis on manufacturing simplicity, system packaging flexibility, relaxation of assembly alignment tolerances, cost reduction of opto-electronic components and long term reliability and stability.
High-performance bearing features strong, lightweight, self-lubricating cage with self-lubricating liners in ball apertures. Designed to operate at high speed (tens of thousands of revolutions per minute) in cryogenic environment like liquid-oxygen or liquid-hydrogen turbopump. Includes inner race, outer race, and cage keeping bearing balls equally spaced.
Rolling-element bearing forces vary nonlinearly with bearing deflection. Thus an accurate rotordynamic transient analysis requires bearing forces to be determined at each step of the transient solution. Analyses have been carried out to show the effect of accurate bearing transient forces (accounting for non-linear speed and load dependent bearing stiffness) as compared to conventional use of average rolling-element bearing stiffness. Bearing forces were calculated by COBRA-AHS (Computer Optimized Ball and Roller Bearing Analysis - Advanced High Speed) and supplied to the rotordynamics code ARDS (Analysis of Rotor Dynamic Systems) for accurate simulation of rotor transient behavior. COBRA-AHS is a fast-running 5 degree-of-freedom computer code able to calculate high speed rolling-element bearing load-displacement data for radial and angular contact ball bearings and also for cylindrical and tapered roller beatings. Results show that use of nonlinear bearing characteristics is essential for accurate prediction of rotordynamic behavior.
The Structure of Flame Balls at Low Lewis-Number (SOFBALL) experiment explored the behavior of a newly discovered flame phenomena called "flame balls." These spherical, stable, stationary flame structures, observed only in microgravity, provide a unique opportunity to study the interactions of the two most important processes necessary for combustion (chemical reaction and heat and mass transport) in the simplest possible configuration. The previously unobtainable experimental data provided a comparison with models of flame stability and flame propagation limits that are crucial both in assessing fire safety and in designing efficient, clean-burning combustion engines.
The effect of internal clearance on radially loaded deepgroove ball and cylindrical roller bearing load distribution and fatigue life was determined for four clearance groups defined in the bearing standards. The analysis was extended to negative clearance (interference) conditions to produce a curve of life factor versus internal clearance. Rolling-element loads can be optimized and bearing life maximized for a small negative operating clearance. Life declines gradually with positive clearance and rapidly with increasing negative clearance. Relationships were found between bearing life and internal clearance as a function of ball or roller diameter, adjusted for load. Results are presented as life factors for radially loaded bearings independent of bearing size or applied load. In addition, a modified Stribeck Equation is presented that relates the maximum rolling-element load to internal bearing clearance.
Rolling element bearings utilized in precision rotating machines require proper alignment, preload, and interference fits to ensure overall optimum performance. Hence, careful attention must be given to bearing installation and disassembly procedures to ensure the above conditions are met. Usually, machines are designed in such a way that bearings can be pressed into housings or onto shafts through the races without loading the rolling elements. However, in some instances, either due to limited size or access, a bearing must be installed or removed in such a way that the load path travels through the rolling elements. This can cause high contact stresses between the rolling elements and the races and introduces the potential for Brinell denting of the races. This paper is a companion to the Part I paper by the authors that discusses material selection and the general design philosophy for the bearing. Here, a more in-depth treatment is given to the design of a dent-resistant bearing utilizing a superelastic alloy, 60NiTi, for the races. A common bearing analysis tool based on rigid body dynamics is used in combination with finite element simulations to design the superelastic bearing. The primary design constraints are prevention of denting and avoiding the balls riding over the edge of the race groove during a blind disassembly process where the load passes through the rolling elements. Through an iterative process, the resulting bearing geometry is tailored to improve axial static load capability compared to a deep-groove ball bearing of the same size. The results suggest that careful selection of materials and bearing geometry can enable blind disassembly without damage to the raceways, which is necessary in the current application (a compressor in the International Space Station Environmental Control and Life Support System), and results in potential design flexibility for other applications, especially small machines with miniature bearings.