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Sample records for a-412-801 ball bearings

  1. Introduction to ball bearings

    NASA Technical Reports Server (NTRS)

    Hamrock, B. J.; Dowson, D.

    1981-01-01

    The purpose of a ball bearing is to provide a relative positioning and rotational freedom while transmitting a load between two structures, usually a shaft and a housing. For high rotational speeds (e.g., in gyroscope ball bearings) the purpose can be expanded to include rotational freedom with practically no wear in the bearing. This condition can be achieved by separating the bearing parts with a coherent film of fluid known as an elastohydrodynamic film. This film can be maintained not only when the bearing carries the load on a shaft, but also when the bearing is preloaded to position the shaft to within micro- or nano-inch accuracy and stability. Background information on ball bearings is provided, different types of ball bearings and their geometry and kinematics are defined, bearing materials, manufacturing processes, and separators are discussed. It is assumed, for the purposes of analysis, that the bearing carries no load.

  2. Ball Bearing Mechanics

    NASA Technical Reports Server (NTRS)

    Hamrock, B. J.; Dowson, D.

    1981-01-01

    Load-deflection relationships for different types of elliptical contacts such as those found in a ball bearing are developed. Simplified expressions that allow quick calculations of deformation to be made simply from a knowledge of the applied load, the material properties, and the geometry of the contacting elements are presented. Ball bearings subjected to radial, thrust and combined ball loads are analyzed. A design criterion for fatigue life of ball bearings is developed. The section of a satisfactory lubricant, as well as describing systems that provide a constant flow of lubricant to the contact, is considered.

  3. Inserts Automatically Lubricate Ball Bearings

    NASA Technical Reports Server (NTRS)

    Hager, J. A.

    1983-01-01

    Inserts on ball-separator ring of ball bearings provide continuous film of lubricant on ball surfaces. Inserts are machined or molded. Small inserts in ball pockets provide steady supply of lubricant. Technique is utilized on equipment for which maintenance is often poor and lubrication interval is uncertain, such as household appliances, automobiles, and marine engines.

  4. History of ball bearings

    NASA Technical Reports Server (NTRS)

    Dowson, D.; Hamrock, B. J.

    1981-01-01

    The familiar precision rolling-element bearings of the twentieth century are products of exacting technology and sophisticated science. Their very effectiveness and basic simplicity of form may discourage further interest in their history and development. Yet the full story covers a large portion of recorded history and surprising evidence of an early recognition of the advantages of rolling motion over sliding action and progress toward the development of rolling-element bearings. The development of rolling-element bearings is followed from the earliest civilizations to the end of the eighteenth century. The influence of general technological developments, particularly those concerned with the movement of large building blocks, road transportation, instruments, water-raising equipment, and windmills are discussed, together with the emergence of studies of the nature of rolling friction and the impact of economic factors. By 1800 the essential features of ball and rolling-element bearings had emerged and it only remained for precision manufacture and mass production to confirm the value of these fascinating machine elements.

  5. High-Performance Ball Bearing

    NASA Technical Reports Server (NTRS)

    Bursey, Roger W., Jr.; Haluck, David A.; Olinger, John B.; Owen, Samuel S.; Poole, William E.

    1995-01-01

    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.

  6. Polyurethane retainers for ball bearings

    NASA Technical Reports Server (NTRS)

    Christy, R. I.

    1973-01-01

    Evaluation of a new ball bearing retainer material is reported. A special composite polyurethane foam ball retainer has been developed that has virtually zero wear, is chemically inert to hydrocarbon lubricants, and stores up to 60 times as much lubricant per unit volume as the most commonly used retainer material, cotton phenolic. This new retainer concept shows promise of years of ball bearing operation without reoiling, based on life testing in high vacuum.

  7. The correct "ball bearings" data.

    PubMed

    Caroni, C

    2002-12-01

    The famous data on fatigue failure times of ball bearings have been quoted incorrectly from Lieblein and Zelen's original paper. The correct data include censored values, as well as non-fatigue failures that must be handled appropriately. They could be described by a mixture of Weibull distributions, corresponding to different modes of failure.

  8. Silicon Nitride Balls For Cryogenic Bearings

    NASA Technical Reports Server (NTRS)

    Butner, Myles F.; Ng, Lillian W.

    1990-01-01

    Resistance to wear greater than that of 440C steel. Experiments show lives of ball bearings immersed in liquid nitrogen or liquid oxygen increased significantly when 440C steel balls (running on 440C steel races) replaced by balls of silicon nitride. Developed for use at high temperatures, where lubrication poor or nonexistent. Best wear life of any bearing tested to date and ball material spalls without fracturing. Plans for future tests call for use of liquid oxygen as working fluid.

  9. Ceramic Rail-Race Ball Bearings

    NASA Technical Reports Server (NTRS)

    Balzer, Mark A.; Mungas, Greg S.; Peters, Gregory H.

    2010-01-01

    Non-lubricated ball bearings featuring rail races have been proposed for use in mechanisms that are required to function in the presence of mineral dust particles in very low-pressure, dry environments with extended life. Like a conventional ball bearing, the proposed bearing would include an inner and an outer ring separated by balls in rolling contact with the races. However, unlike a conventional ball bearing, the balls would not roll in semi-circular or gothic arch race grooves in the rings: instead, the races would be shaped to form two or more rails (see figure). During operation, the motion of the balls would push dust particles into the spaces between the rails where the particles could not generate rolling resistance for the balls

  10. Eddy-Current Inspection of Ball Bearings

    NASA Technical Reports Server (NTRS)

    Bankston, B.

    1985-01-01

    Custom eddy-current probe locates surface anomalies. Low friction air cushion within cone allows ball to roll easily. Eddy current probe reliably detects surface and near-surface cracks, voids, and material anomalies in bearing balls or other spherical objects. Defects in ball surface detected by probe displayed on CRT and recorded on strip-chart recorder.

  11. Ball Bearing Analysis with the ORBIS Tool

    NASA Technical Reports Server (NTRS)

    Halpin, Jacob D.

    2016-01-01

    Ball bearing design is critical to the success of aerospace mechanisms. Key bearing performance parameters, such as load capability, stiffness, torque, and life all depend on accurate determination of the internal load distribution. Hence, a good analytical bearing tool that provides both comprehensive capabilities and reliable results becomes a significant asset to the engineer. This paper introduces the ORBIS bearing tool. A discussion of key modeling assumptions and a technical overview is provided. Numerous validation studies and case studies using the ORBIS tool are presented. All results suggest the ORBIS code closely correlates to predictions on bearing internal load distributions, stiffness, deflection and stresses.

  12. Bending stresses in spherically hollow ball bearing and fatigue experiments

    NASA Technical Reports Server (NTRS)

    Nypan, L. J.; Coe, H. H.; Parker, R. J.

    1975-01-01

    Spherically hollow balls of 21.7, 50.0, and 56.5 percent mass reduction were operated in ball bearings and in a five-ball fatigue tester with differing outcomes. Available theoretical and experimental treatments of stresses in spherically hollow balls are reviewed and compared. Bending stresses are estimated for these spherically hollow balls to better understand the differences in ball bearing and fatigue test experience.

  13. Bending stresses in spherically hollow ball bearing and fatigue experiments

    NASA Technical Reports Server (NTRS)

    Nypan, L. J.; Coe, H. H.; Parker, R. J.

    1975-01-01

    Spherically hollow balls of 21.7, 50.0 and 56.5 per cent mass reduction have been operated in ball bearings and in a 5-ball fatigue tester with differing outcomes. Available theoretical and experimental treatments of stresses in spherically hollow balls are reviewed and compared. Bending stresses are estimated for these spherically hollow balls to better understand the differences in ball bearing and fatigue test experience.

  14. Low-Wear Ball-Bearing Separator

    NASA Technical Reports Server (NTRS)

    Hawkinson, Elden L.

    1991-01-01

    Proposed ball-bearing separator for use in cryogenic pump stronger and more resistant to wear. Consists of molded plastic-and-metal composite ring imbued with solid lubricant and containing embedded metal ring. Obtains combination of strength and lubricity. Before molding and machining, ring includes tooling portion for handling and indexing. Molded composite blend of PTFE and fluorinated ethylene/propylene (FEP) filled with brass and bronze powder and molybdenum disulfide powder.

  15. Reexamination of Ball-Race Conformity Effects on Ball Bearing Life

    NASA Technical Reports Server (NTRS)

    Zaretsky, Erwin V.; Poplawski, Joseph V.; Root, Lawrence E.

    2007-01-01

    The analysis in this report considers the life of the ball set as well as the respective lives of the races to reassess the effect of ball-race conformity on ball bearing life. The related changes in ball bearing life are incorporated in life factors that can be used to modify the bearing predicted life using the Lundberg-Palmgren equations and the ANSI/ABMA and ISO Standards. Two simple algebraic relationships were established to calculate life factors LF(sub c) to determine the effect of inner- and outer-race conformity combinations on bearing L(sub 10) life for deepgroove and angular-contact ball bearings, respectively. Depending on the bearing type and series as well as conformity combinations, the calculated life for deep-groove ball bearings can be over 40 percent less than that calculated by the Lundberg-Palmgren equations. For angular-contact ball bearings, the life can vary between +16 and -39 percent from that calculated by the Lundberg-Palmgren equations. Comparing the two ball bearing types, the life factors LF(sub c) for the deep-groove bearings can be as much as 40 percent lower than that for angular-contact ball bearings.

  16. The determination of particulate contamination in miniature ball bearings

    SciTech Connect

    Harding, W.B.

    1992-12-01

    A method is described for determining the particulate contamination in miniature ball bearings in which the bearing is flushed with a solvent that is then filtered. The particles that are collected on the filter are examined by optical microscopy.

  17. Hardening treatment of friction surfaces of ball journal bearings

    NASA Astrophysics Data System (ADS)

    Gorlenko, A. O.; Davidov, S. V.

    2016-04-01

    The article presents the technology of finishing plasma hardening by the application of the multi-layer nanocoating Si-O-C-N system to harden the friction surfaces of the ball journal bearings. The authors of the paper have studied the applied wear-resistant anti-friction coating tribological characteristics, which determine the increase in wear resistance of the ball journal bearings.

  18. Ball motion and sliding friction in an arched outer race ball bearing

    NASA Technical Reports Server (NTRS)

    Hamrock, B. J.

    1973-01-01

    The motion of the ball and sliding friction in an arched outer race ball bearing under thrust loads is determined. Fatigue life evaluations were made. The analysis is applied to a 150 millimeter bore ball bearing. The results indicated that for high speed-light load applications the arched bearing has significant improvement in fatigue life over that of a conventional bearing. An arching of 0.254 mm (0.01 in.) was found to be an optimal. For an arched bearing it was also found that a considerable amount of spinning occurs at the outer race contacts.

  19. Ball motion and sliding friction in an arched outer-race ball bearing

    NASA Technical Reports Server (NTRS)

    Hamrock, B. J.

    1974-01-01

    The motion of the ball and sliding friction in an arched outer-race ball bearing under thrust load is analyzed. Fatigue life evaluations were made. The analysis is applied to a 150-millimeter-bore ball bearing. The results indicated that for high-speed light-load applications the arched bearing has significant improvement in fatigue life over that of a conventional bearing. An arching of 0.254 mm (0.01 in.) was found to be optimal. Also, for an arched bearing a considerable amount of spinning occurs at the outer-race contacts.

  20. Resonant frequency method for bearing ball inspection

    DOEpatents

    Khuri-Yakub, B. T.; Hsieh, Chung-Kao

    1993-01-01

    The present invention provides for an inspection system and method for detecting defects in test objects which includes means for generating expansion inducing energy focused upon the test object at a first location, such expansion being allowed to contract, thereby causing pressure wave within and on the surface of the test object. Such expansion inducing energy may be provided by, for example, a laser beam or ultrasonic energy. At a second location, the amplitudes and phases of the acoustic waves are detected and the resonant frequencies' quality factors are calculated and compared to predetermined quality factor data, such comparison providing information of whether the test object contains a defect. The inspection system and method also includes means for mounting the bearing ball for inspection.

  1. DESIGN NOTE: Optical inspection of ball bearing defects

    NASA Astrophysics Data System (ADS)

    Ng, T. W.

    2007-09-01

    Ball bearings with defects can cause catastrophic machine element failure. The technique of detection using visual features provides a rapid means of inspection, although it reveals only surface defects. Nevertheless, the specular nature of the bearing surface makes it difficult to design illumination that produces high quality images for analysis using this method. In this work, a technique that uses ring light for illumination is demonstrated to be able to clearly reveal surface defects such as spalling and waviness in ball bearings.

  2. Large bearing operation without retainer. [high speed ball bearings for space application

    NASA Technical Reports Server (NTRS)

    Kingsbury, E.

    1978-01-01

    The design and testing of large high-speed ball bearings for space application is described. A well-defined lubrication system to provide oil to both race contacts in zero g allows stable operation without ball retainer.

  3. Relation between Hertz Stress-Life Exponent, Ball-Race Conformity, and Ball Bearing Life

    NASA Technical Reports Server (NTRS)

    Zaretsky, Erwin V.; Poplawski, Joseph V.; Root, Lawrence E.

    2006-01-01

    ANSI/ABMA and ISO standards based on Lundberg-Palmgren bearing life theory are normalized for ball bearings having inner- and outer-race conformities of 52 percent (0.52) and made from pre-1940 bearing steel. The Lundberg-Palmgren theory incorporates an inverse 9th power relation between Hertz stress and fatigue life for ball bearings. The effect of race conformity on ball set life independent of race life is not incorporated into the Lundberg-Palmgren theory. In addition, post-1960 vacuum-processed bearing steel exhibits a 12th power relation between Hertz stress and life. The work reported extends the previous work of Zaretsky, Poplawski, and Root to calculate changes in bearing life, that includes the life of the ball set, caused by race conformity, Hertz stress-life exponent, ball bearing type and bearing series. The bearing fatigue life in actual application will usually be equal to or greater than that calculated using the ANSI/ABMA and ISO standards that incorporate the Lundberg-Palmgren theory. The relative fatigue life of an individual race is more sensitive to changes in race conformity for Hertz stress-life exponent n of 12 than where n = 9. However, when the effects are combined to predict actual bearing life for a specified set of conditions and bearing geometry, the predicted life of the bearing will be greater for a value of n = 12 than n = 9.

  4. Relation Between Hertz Stress-Life Exponent, Ball-Race Conformity, and Ball Bearing Life

    NASA Technical Reports Server (NTRS)

    Zaretsky, Erwin V.; Poplawski, Joseph V.; Root, Lawrence E.

    2008-01-01

    ANSI/ABMA and ISO standards based on Lundberg-Palmgren bearing life theory are normalized for ball bearings having inner- and outerrace conformities of 52 percent (0.52) and made from pre-1940 bearing steel. The Lundberg-Palmgren theory incorporates an inverse 9th power relation between Hertz stress and fatigue life for ball bearings. The effect of race conformity on ball set life independent of race life is not incorporated into the Lundberg-Palmgren theory. In addition, post-1960 vacuum-processed bearing steel exhibits a 12th power relation between Hertz stress and life. The work reported extends the previous work of Zaretsky, Poplawski, and Root to calculate changes in bearing life--that includes the life of the ball set--caused by race conformity, Hertz stress-life exponent, ball bearing type and bearing series. The bearing fatigue life in actual application will usually be equal to or greater than that calculated using the ANSI/ABMA and ISO standards that incorporate the Lundberg-Palmgren theory. The relative fatigue life of an individual race is more sensitive to changes in race conformity for Hertz stress-life exponent n of 12 than where n = 9. However, when the effects are combined to predict actual bearing life for a specified set of conditions and bearing geometry, the predicted life of the bearing will be greater for a value of n = 12 than n = 9.

  5. Ball bearing lubrication: The elastohydrodynamics of elliptical contacts

    NASA Technical Reports Server (NTRS)

    Hamrock, B. J.; Dowson, D.

    1981-01-01

    The history of ball bearings is examined, taking into account rollers and the wheel in the early civilizations, the development of early forms of rolling-element bearings in the classical civilizations, the Middle Ages, the Industrial Revolution, the emergence of the precision ball bearing, scientific studies of contact mechanics and rolling friction, and the past fifty years. An introduction to ball bearings is presented, and aspects of ball bearing mechanics are explored. Basic characteristics of lubrication are considered along with lubrication equations, the lubrication of rigid ellipsoidal solids, and elastohydrodynamic lubrication theory. Attention is given to the theoretical results for fully flooded elliptical hydrodynamic contacts, the theoretical results for starved elliptical contacts, experimental investigations, the elastohydrodynamics of elliptical contacts for materials of low elastic modulus, the film thickness for different regimes of fluid-film lubrication, and applications.

  6. Experimental ball bearing dynamics study. [by high speed photography

    NASA Technical Reports Server (NTRS)

    Signer, H. R.

    1973-01-01

    A photographic method was employed to record the kinematic performance of rolling elements in turbo machinery ball bearings. The 110 mm split inner ring test bearings had nominal contact angles of 26 deg and 34 deg. High speed films were taken at inner ring speeds of 4,000, 8,000 and 12,000 rpm and at thrust loads of 4,448 N and 22,240 N (1,000 and 5,000 lbs). The films were measured and this data reduced to obtain separator speed, ball speed and ball spin axis orientation.

  7. Effect of Hoop Stress on Ball Bearing Life Prediction

    NASA Technical Reports Server (NTRS)

    Zaretsky, Erwin V.; August, Richard; Coe, Harold H.

    1995-01-01

    A finite-element analysis (FEA) of a generic, dimensionally normalized inner race of an angular-contact ball bearing was performed under varying conditions of speed and the press (or interference) fit of the inner-race bore on a journal. The FEA results at the ball-race contact were used to derive an equation from which was obtained the radius of an equivalent cylindrical bearing race with the same or similar hoop stress. The radius of the equivalent cylinder was used to obtain a generalized closed-form approximation of the hoop stresses at the ball-inner-race contact in an angular-contact ball bearing. A life analysis was performed on both a 45- and a 120-mm-bore, angular-contact ball bearing. The predicted lives with and without hoop stress were compared with experimental endurance results obtained at 12000 and 25000 rpm with the 120-mm-bore ball bearing. A life factor equation based on hoop stress is presented.

  8. Effect of grease type on abnormal vibration of ball bearing

    NASA Astrophysics Data System (ADS)

    Itagaki, Takayoshi; Ohta, Hiroyuki; Igarashib, Teruo

    2003-12-01

    The abnormal vibration of ball bearings lubricated with grease was studied. The test bearings were lubricated with three types of grease: Li soap/silicone oil grease, Na soap/mineral oil grease and Li soap/mineral oil grease. In the experiments, the axial-loaded ball bearings were operated at a constant rotational speed, and the vibration and the outer ring temperatures of the test bearings were measured. In addition, the shear stress and shear rate of the greases were measured by a rheometer. The experimental results showed that the abnormal vibration occurs on the test bearings lubricated with all three types of grease. Based on the experimental results, the generating mechanisms of the abnormal vibrations were discussed. From the discussions, it seems reasonable to conclude: (1) Li soap/silicone oil grease and Na soap/mineral oil grease both have a negative damping moment characteristic. The abnormal vibrations of the ball bearings lubricated with these greases are generated by the negative damping moment. (2) The abnormal vibration of the ball bearings lubricated with Li soap/mineral oil grease is generated by the decreasing positive damping moment of the grease due to the rising temperature.

  9. Wear-resistant ball bearings for space applications

    NASA Technical Reports Server (NTRS)

    Boving, H.; Hintermann, H. E.; Hanni, W.; Bondivenne, E.; Boeto, M.; Conde, E.

    1977-01-01

    Ball bearings consisting of steel parts of which the rings are coated with hard, wear resistant, chemical vapor deposited TiC are described. Experiments conducted in ultrahigh vacuum, using cages of various materials with self-lubricating properties, show that such bearings are suitable for space applications. The results of laboratory tests on the ESA Meteosat Radiometer Focalizing mechanism, which contains six coated bearings, are summarized.

  10. Determination of ball bearing dynamic stiffness

    NASA Technical Reports Server (NTRS)

    Beatty, R. F.; Rowan, B. F.

    1982-01-01

    The dynamic radial stiffness characteristics of rolling element bearings are currently determined by analytical methods that have not been experimentally verified. These bearing data are vital to rotating machinery design integrity because accurate critical speeds and rotor stability predictions are highly dependent on the bearing stiffness. A tester was designed capable of controlling the bearing axial preload, speed, and rotor unbalance. The rotor and support structures were constructed to permit critical speeds that are predominantly determined by a 57 mm test bearing. A curve of calculated critical speed versus stiffness was used to determine the actual bearing stiffness from the empirical data. The results of extensive testing are used to verify analytical predictions, increase confidence in existing bearing computer programs, and to serve as a data base for efforts to correct these programs.

  11. Fatigue life of high-speed ball bearings with silicon nitride balls

    NASA Technical Reports Server (NTRS)

    Parker, R. J.; Zaretsky, E. V.

    1974-01-01

    Hot-pressed silicon nitride was evaluated as a rolling-element bearing material. The five-ball fatigue tester was used to test 12.7-mm- diameter silicon nitride balls at maximum Hertz stresses ranging from 4.27 x 10 to the 9th power n/sq m to 6.21 x 10 to the 9th power n/sq m at a race temperature of 328K. The fatigue life of NC-132 hot-pressed silicon nitride was found to be equal to typical bearing steels and much greater than other ceramic or cermet materials at the same stress levels. A digital computer program was used to predict the fatigue life of 120-mm- bore angular-contact ball bearings containing either steel or silicon nitride balls. The analysis indicates that there is no improvement in the lives of bearings of the same geometry operating at DN values from 2 to 4 million where silicon nitride balls are used in place of steel balls.

  12. Ball Bearings Equipped for In Situ Lubrication on Demand

    NASA Technical Reports Server (NTRS)

    Marchetti, Mario; Jones, William R., Jr.; Pepper, Stephen V.; Jansen, Mark; Predmore, Roamer

    2005-01-01

    In situ systems that provide fresh lubricants to ball/race contacts on demand have been developed to prolong the operational lives of ball bearings. These systems were originally intended to be incorporated into ball bearings in mechanisms that are required to operate in outer space for years, in conditions in which lubricants tend to deteriorate and/or evaporate. These systems may also be useful for similarly prolonging bearing lifetimes on Earth. Reservoirs have been among the means used previously to resupply lubricants. Lubricant- resupply reservoirs are bulky and add complexity to bearing assemblies. In addition, such a reservoir cannot be turned on or off as needed: it supplies lubricant continuously, often leading to an excess of lubricant in the bearing. A lubricator of the present type includes a porous ring cartridge attached to the inner or the outer ring of a ball bearing (see Figure 1). Oil is stored in the porous cartridge and is released by heating the cartridge: Because the thermal expansion of the oil exceeds that of the cartridge, heating causes the ejection of some oil. A metal film can be deposited on a face of the cartridge to serve as an electrical-resistance heater. The heater can be activated in response to a measured increase in torque that signals depletion of oil from the bearing/race contacts. Because the oil has low surface tension and readily wets the bearing-ring material, it spreads over the bearing ring and eventually reaches the ball/race contacts. The Marangoni effect (a surface-tension gradient associated with a temperature gradient) is utilized to enhance the desired transfer of lubricant to the ball/race contacts during heating. For a test, a ball bearing designed for use at low speed was assembled without lubricant and equipped with a porous-ring lubricator, the resistance heater of which consumed a power of less than 1 W when triggered on by a torque-measuring device. In the test, a load of 20 lb (.89 N) was applied and the

  13. Hybrid hydrostatic/ball bearings in high-speed turbomachinery

    NASA Technical Reports Server (NTRS)

    Nielson, C. E.

    1983-01-01

    A high speed, high pressure liquid hydrogen turbopump was designed, fabricated, and tested under a previous contract. This design was then modified to incorporate hybrid hydrostatic/ball bearings on both the pump end and turbine end to replace the original conventional ball bearing packages. The design, analysis, turbopump modification, assembly, and testing of the turbopump with hybrid bearings is presented here. Initial design considerations and rotordynamic performance analysis was made to define expected turbopump operating characteristics and are reported. The results of testing the turbopump to speeds of 9215 rad/s (88,000 rpm) using a wide range of hydrostatic bearing supply pressures are presented. The hydrostatic bearing test data and the rotordynamic behavior of the turbopump was closely analyzed and are included in the report. The testing of hybrid hydrostatic/ball bearings on a turbopump to the high speed requirements has indicated the configuration concept is feasible. The program has presented a great deal of information on the technology requirements of integrating the hybrid bearing into high speed turbopump designs for improved bearing life.

  14. Ball bearing versus magnetic bearing reaction and momentum wheels as momentum actuators

    NASA Technical Reports Server (NTRS)

    Auer, W.

    1980-01-01

    Different bearing technologies of momentum actuators for the attitude control of satellites are compared and a guideline for the selection of the suitable momentum actuators or momentum actuator configurations to meet given mission goals with high reliability and low cost is developed. The comparison between ball bearing and magnetic bearing momentum actuators shows that given mission requirements can be economically met by employing the ball bearing technology without decreasing reliability and lifetime. However, for some special mission requirements, such as 'zero friction at zero speed,' fine pointing (met by vernier gimballing), and/or active damping, magnetic bearings may be advantageous. This makes it evident that magnetic bearing technology will not replace ball bearing technology for momentum actuators, but will supplement it for some special mission requirements.

  15. Experimental evaluation of 150-millimeter bore ball bearing to 3 million DN using either solid or drilled balls

    NASA Technical Reports Server (NTRS)

    Scibbe, H. W.; Munson, H. E.

    1973-01-01

    Seven 150-mm bore ball bearings were run under 8900 Newton (2000 lb) thrust load at speeds from 6670 to 20,000 rpm (1 to 3 million DN). Four of the bearings had conventional solid balls and three bearing had drilled (cylindrically hollow) balls with 50 percent mass reduction. The bearings were under-race cooled and slot-lubricated with Type 2 ester oil at flow rates from 4.35 to 5.80 liters per minute (1.15 to 1.57 gal min). Friction torque and temperatures were measured on all bearings. No significant difference in torque was noted, between the solid and drilled ball bearings. One bearing of each type was rerun at 17,800 Newtons (4000 lb) thrust load. The solid ball bearings performed satisfactorily at 3 million DN. However, at about 2 million DN the drilled ball bearing experienced a broken ball and cracks appeared in two other balls as the result of flexure fatigue. Metallurgical examination of the cracked balls indicated a brittle structure in the bore of the drilled balls.

  16. Extended Life Testing of Duplex Ball Bearings

    NASA Technical Reports Server (NTRS)

    Mobley, Jeffrey; Robertson, Michael; Hodges, Charles

    2016-01-01

    Sierra Nevada Corporation’s Space Systems performed bearing life testing for the Scan Mirror Motor/Encoder Assembly (SMMA), part of the Scan Mirror Assembly on-board the Aerosol Polarimetry Sensor (APS) on the NASA Glory Spacecraft. The baseline bearing life test duration extended beyond the launch date for the Glory Spacecraft; a risk that the program was willing to undertake with the understanding that if any anomalies or failures occurred before the required life was achieved, then the mission objectives or operating profile could be modified on orbit to take those results into account. Even though the Glory Spacecraft failed to reach orbit during its launch in March of 2011, the bearing life testing was continued through a mutual understanding of value between Sierra Nevada Corporation and our customer; with a revised goal of testing to failure rather than completing a required number of life cycles. Life testing thus far has not only exceeded the original mission required life, but has also exceeded the published test data for Cumulative Degradation Factor (CDF) from NASA/CR-2009-215681. Many lessons were learned along the way regarding long life testing. The bearing life test has been temporarily suspended due to test support equipment issues.

  17. Design of a high-speed reliable ball bearing

    NASA Technical Reports Server (NTRS)

    Singer, Herbert B.; Gelotte, Erik

    1994-01-01

    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.

  18. Interference-Fit Life Factors for Ball Bearings

    NASA Technical Reports Server (NTRS)

    Oswald, Fred B.; Zaretsky, Erwin V.; Poplawski, Joseph V.

    2010-01-01

    The effect of hoop stresses on the rolling-element fatigue life of angular-contact and deep-groove ball bearings was determined for common inner-ring interference fits at the ABEC-5 tolerance level. The analysis was applied to over 1150 bearing configurations and load cases. Hoop stresses were superimposed on the Hertzian principal stresses created by the applied bearing load to calculate the inner-race maximum shearing stress. The resulting fatigue life of the bearing was recalculated through a series of equations. The reduction in the fatigue life is presented as life factors that are applied to the unfactored bearing life. The life factors found in this study ranged from 1.00 (no life reduction)--where there was no net interface pressure--to a worst case of 0.38 (a 62-percent life reduction). For a given interference fit, the reduction in life is different for angular-contact and deep-groove ball bearings. Interference fits also affect the maximum Hertz stress-life relation. Experimental data of Czyzewski, showing the effect of interference fit on rolling-element fatigue life, were reanalyzed to determine the shear stress-life exponent. The Czyzewski data shear stress-life exponent c equals 8.77, compared with the assumed value of 9. Results are presented as tables and charts of life factors for angular-contact and deep-groove ball bearings with light, normal, and heavy loads and interference fits ranging from extremely light to extremely heavy.

  19. The ball bearing as a rheological test device

    NASA Technical Reports Server (NTRS)

    Kingsbury, E.

    1984-01-01

    An angular-contact ball bearing provides an easily obtainable, precise mechanical system for rheological tests on thin films under high pressure. The test conditions are by definition similar to those found in practice. Accessible independent variables include size, pressure, bulk temperature, roughness, adsorbed surfactant, fluid type, fluid quantity, fluid supply rate, film thickness, entrainment velocity, transit time, and combined strain. Easily measured or inferred variables include slip, changes in film thickness with time (transients), strain rate, lubricant elastic modulus (thin film, high pressure), tractive force, lubricant chemical degradation rate, and lubricant degradation product. Methods for setting and obtaining these quantities in a bearing are discussed, together with experimental limitations on them.

  20. Performance of hybrid ball bearings in oil and jet fuel

    NASA Astrophysics Data System (ADS)

    Schrader, Stephen M.; Pfaffenberger, Eugene E.

    1992-07-01

    A 308-size hybrid ball bearing, with ceramic balls and steel rings, was tested using a diester oil and gas turbine fuel as lubricants at several speeds and loads. Heat generation data from this test work was then correlated with the heat generation model from a widely used computer code. The ability of this hybrid split inner ring bearing design to endure thrust reversals, which are expected in many turbine applications, was demonstrated. Finally, the bearing was successfully endurance tested in JP-10 fuel for 25 hours at 7560 N axial load and 36,000 rpm. This work has successfully demonstrated the technology necessary to use fuel-lubricated hybrid bearings in limited-life gas turbine engine applications such as missiles, drones, and other unmanned air vehicles (UAVs). In addition, it has provided guidance for use in designing such bearing systems. As a result, the benefits of removing the conventional oil lubricant system, i.e., design simplification and reduced maintenance, can be realized.

  1. Performance of hybrid ball bearings in oil and jet fuel

    SciTech Connect

    Schrader, S.M.; Pfaffenberger, E.E. )

    1992-07-01

    A 308-size hybrid ball bearing, with ceramic balls and steel rings, was tested using a diester oil and gas turbine fuel as lubricants at several speeds and loads. Heat generation data from this test work was then correlated with the heat generation model from a widely used computer code. The ability of this hybrid split inner ring bearing design to endure thrust reversals, which are expected in many turbine applications, was demonstrated. Finally, the bearing was successfully endurance tested in JP-10 fuel for 25 hours at 7560 N axial load and 36,000 rpm. This work has successfully demonstrated the technology necessary to use fuel-lubricated hybrid bearings in limited-life gas turbine engine applications such as missiles, drones, and other unmanned air vehicles (UAVs). In addition, it has provided guidance for use in designing such bearing systems. As a result, the benefits of removing the conventional oil lubricant system, i.e., design simplification and reduced maintenance, can be realized. 6 refs.

  2. 48 CFR 252.225-7016 - Restriction on acquisition of ball and roller bearings.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... of ball and roller bearings. 252.225-7016 Section 252.225-7016 Federal Acquisition Regulations System... and roller bearings. As prescribed in 225.7009-5, use the following clause: RESTRICTION ON ACQUISITION OF BALL AND ROLLER BEARINGS (JUN 2011) (a) Definitions. As used in this clause— (1) Bearing...

  3. 48 CFR 252.225-7016 - Restriction on acquisition of ball and roller bearings.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... of ball and roller bearings. 252.225-7016 Section 252.225-7016 Federal Acquisition Regulations System... and roller bearings. As prescribed in 225.7009-5, use the following clause: Restriction on Acquisition of Ball and Roller Bearings (JUN 2011) (a) Definitions. As used in this clause— (1) Bearing...

  4. 48 CFR 252.225-7016 - Restriction on acquisition of ball and roller bearings.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... of ball and roller bearings. 252.225-7016 Section 252.225-7016 Federal Acquisition Regulations System... and roller bearings. As prescribed in 225.7009-5, use the following clause: Restriction on Acquisition of Ball and Roller Bearings (JUN 2011) (a) Definitions. As used in this clause— (1) Bearing...

  5. 48 CFR 252.225-7016 - Restriction on acquisition of ball and roller bearings.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... of ball and roller bearings. 252.225-7016 Section 252.225-7016 Federal Acquisition Regulations System... and roller bearings. As prescribed in 225.7009-5, use the following clause: Restriction on Acquisition of Ball and Roller Bearings (JUN 2011) (a) Definitions. As used in this clause— (1) Bearing...

  6. 76 FR 10335 - Ball Bearings and Parts Thereof From Germany: Initiation of Antidumping Duty Changed...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-24

    ..., 75 FR 37759 (June 30, 2010). After analysis of the quantity and value of the sales of ball bearings... FR 20900 (May 15, 1989). On June 30, 2010, we initiated an administrative review of the order on ball... International Trade Administration Ball Bearings and Parts Thereof From Germany: Initiation of Antidumping...

  7. 48 CFR 252.225-7016 - Restriction on acquisition of ball and roller bearings.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... of ball and roller bearings. 252.225-7016 Section 252.225-7016 Federal Acquisition Regulations System... and roller bearings. As prescribed in 225.7009-5, use the following clause: Restriction on Acquisition of Ball and Roller Bearings (MAR 2006) (a) Definitions. As used in this clause' (1)...

  8. Wear-resistant ball bearings for space applications. [coated with titanium carbide

    NASA Technical Reports Server (NTRS)

    Boving, H.; Hintermann, H. E.; Haenni, W.; Bondivenne, E.; Boeto, M.; Conde, M.

    1977-01-01

    Ball bearings for hostile environments were developed. They consist of normal ball bearing steel parts of which the rings are coated with hard, wear-resistant, chemical vapor deposited (C.V.D) TiC. Experiments in ultrahigh vacuum, using cages of various materials with self-lubricating properties, have shown that such bearings are suitable for space applications.

  9. Unbalance Response Prediction for Rotors on Ball Bearings Using Speed and Load Dependent Nonlinear Bearing Stiffness

    NASA Technical Reports Server (NTRS)

    Fleming, David P.; Poplawski, J. V.

    2003-01-01

    Rolling-element bearing forces vary nonlinearly with bearing deflection. Thus an accurate rotordynamic analysis requires that bearing forces corresponding to the actual bearing deflection be utilized. For this work bearing forces were calculated by COBRA-AHS, a recently developed rolling-element bearing analysis code. Bearing stiffness was found to be a strong function of bearing deflection, with higher deflection producing markedly higher stiffness. Curves fitted to the bearing data for a range of speeds and loads were supplied to a flexible rotor unbalance response analysis. The rotordynamic analysis showed that vibration response varied nonlinearly with the amount of rotor imbalance. Moreover, the increase in stiffness as critical speeds were approached caused a large increase in rotor and bearing vibration amplitude over part of the speed range compared to the case of constant bearing stiffness. Regions of bistable operation were possible, in which the amplitude at a given speed was much larger during rotor acceleration than during deceleration. A moderate amount of damping will eliminate the bistable region, but this damping is not inherent in ball bearings.

  10. Ball bearing vibrations amplitude modeling and test comparisons

    NASA Technical Reports Server (NTRS)

    Hightower, Richard A., III; Bailey, Dave

    1995-01-01

    Bearings generate disturbances that, when combined with structural gains of a momentum wheel, contribute to induced vibration in the wheel. The frequencies generated by a ball bearing are defined by the bearing's geometry and defects. The amplitudes at these frequencies are dependent upon the actual geometry variations from perfection; therefore, a geometrically perfect bearing will produce no amplitudes at the kinematic frequencies that the design generates. Because perfect geometry can only be approached, emitted vibrations do occur. The most significant vibration is at the spin frequency and can be balanced out in the build process. Other frequencies' amplitudes, however, cannot be balanced out. Momentum wheels are usually the single largest source of vibrations in a spacecraft and can contribute to pointing inaccuracies if emitted vibrations ring the structure or are in the high-gain bandwidth of a sensitive pointing control loop. It is therefore important to be able to provide an a priori knowledge of possible amplitudes that are singular in source or are a result of interacting defects that do not reveal themselves in normal frequency prediction equations. This paper will describe the computer model that provides for the incorporation of bearing geometry errors and then develops an estimation of actual amplitudes and frequencies. Test results were correlated with the model. A momentum wheel was producing an unacceptable 74 Hz amplitude. The model was used to simulate geometry errors and proved successful in identifying a cause that was verified when the parts were inspected.

  11. Comparison of Models for Ball Bearing Dynamic Capacity and Life

    NASA Technical Reports Server (NTRS)

    Gupta, Pradeep K.; Oswald, Fred B.; Zaretsky, Erwin V.

    2015-01-01

    Generalized formulations for dynamic capacity and life of ball bearings, based on the models introduced by Lundberg and Palmgren and Zaretsky, have been developed and implemented in the bearing dynamics computer code, ADORE. Unlike the original Lundberg-Palmgren dynamic capacity equation, where the elastic properties are part of the life constant, the generalized formulations permit variation of elastic properties of the interacting materials. The newly updated Lundberg-Palmgren model allows prediction of life as a function of elastic properties. For elastic properties similar to those of AISI 52100 bearing steel, both the original and updated Lundberg-Palmgren models provide identical results. A comparison between the Lundberg-Palmgren and the Zaretsky models shows that at relatively light loads the Zaretsky model predicts a much higher life than the Lundberg-Palmgren model. As the load increases, the Zaretsky model provides a much faster drop off in life. This is because the Zaretsky model is much more sensitive to load than the Lundberg-Palmgren model. The generalized implementation where all model parameters can be varied provides an effective tool for future model validation and enhancement in bearing life prediction capabilities.

  12. 48 CFR 225.7009 - Restriction on ball and roller bearings.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 48 Federal Acquisition Regulations System 3 2011-10-01 2011-10-01 false Restriction on ball and roller bearings. 225.7009 Section 225.7009 Federal Acquisition Regulations System DEFENSE ACQUISITION... roller bearings....

  13. 48 CFR 225.7009 - Restriction on ball and roller bearings.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 3 2010-10-01 2010-10-01 false Restriction on ball and roller bearings. 225.7009 Section 225.7009 Federal Acquisition Regulations System DEFENSE ACQUISITION... roller bearings....

  14. 48 CFR 225.7009 - Restriction on ball and roller bearings.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 48 Federal Acquisition Regulations System 3 2013-10-01 2013-10-01 false Restriction on ball and roller bearings. 225.7009 Section 225.7009 Federal Acquisition Regulations System DEFENSE ACQUISITION... roller bearings....

  15. 48 CFR 225.7009 - Restriction on ball and roller bearings.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 48 Federal Acquisition Regulations System 3 2014-10-01 2014-10-01 false Restriction on ball and roller bearings. 225.7009 Section 225.7009 Federal Acquisition Regulations System DEFENSE ACQUISITION... roller bearings....

  16. 48 CFR 225.7009 - Restriction on ball and roller bearings.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 48 Federal Acquisition Regulations System 3 2012-10-01 2012-10-01 false Restriction on ball and roller bearings. 225.7009 Section 225.7009 Federal Acquisition Regulations System DEFENSE ACQUISITION... roller bearings....

  17. Transient Vibration Prediction for Rotors on Ball Bearings Using Load-dependent Non-linear Bearing Stiffness

    NASA Technical Reports Server (NTRS)

    Fleming, David P.; Poplawski, J. V.

    2002-01-01

    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.

  18. A study on the noise characteristics of polymer ball bearings under various lubrication conditions

    NASA Astrophysics Data System (ADS)

    Dinç, S. K.; Temiz, V.; Kamburoǧlu, E.

    2013-12-01

    Polymer bearings are generally praised by the manufacturers for running silently. However such statements never go beyond qualitative assumptions. Therefore, studying polymer ball bearing noise would have been meaningful solely on the perspective of silent running machinery. On the other hand, the service life of a polymer ball bearing is unpredictable and there's no preventive maintenance practice that provides data regarding the condition of a polymer ball bearing. In this study, we assume that an investigation of their noise characteristics could also reveal clues concerning their performances. The main objective of this study is to determine the noise characteristics of polymer ball bearings lubricated with different lubricant greases of varying viscosity grades through experimental means. Sound pressure level measurements of SKF brand polymer bearings with polypropylene rings, polypropylene cage and glass balls were made with a 1/2 inch microphone in 1/3-octave bands, at frequencies up to 12.5 kHz, under various radial loads and rotational speeds. The bearings were mounted on a shaft driven by an AC motor with stepless speed control, adjustable between 0 - 1400 rpm. The ball bearings were running inside an acoustic chamber designed for the insulation of environmental noise and the noise of the motor at target frequencies. The resulting sound pressure level spectra were evaluated and the effects of the lubrication conditions on the noise of the ball bearing and possible diagnostic insight that could be gained through studying bearing noise characteristics were discussed.

  19. Comparison of predicted and experimental thermal performance of angular-contact ball bearings

    NASA Technical Reports Server (NTRS)

    Parker, R. J.

    1984-01-01

    Predicted bearing heat generation and bearing temperature were verified by experimental data for ball bearings over a range of sizes, shaft speeds, and lubricant flow rates. The computer program Shaberth requires, as input, a factor which describes the air-oil mixture in the bearing cavity for calculation of the ball drag contribution to bearing heat generation. An equation for this lubricant percent volume in the bearing cavity was derived and appears to be valid over the range of test conditions including bearing bore sizes from 35 to 167 mm and shaft speeds from 1.0 to 3.0 million DN.

  20. Critical flaw size in silicon nitride ball bearings

    NASA Astrophysics Data System (ADS)

    Levesque, George Arthur

    Aircraft engine and bearing manufacturers have been aggressively pursuing advanced materials technology systems solutions to meet main shaft-bearing needs of advanced military aircraft engines. Ceramic silicon nitride hybrid bearings are being developed for such high performance applications. Though silicon nitride exhibits many favorable properties such as high compressive strength, high hardness, a third of the density of steel, low coefficient of thermal expansion, and high corrosion and temperature resistance, they also have low fracture toughness and are susceptible to failure from fatigue spalls emanating from pre-existing surface flaws that can grow under rolling contact fatigue (RCF). Rolling elements and raceways are among the most demanding components in aircraft engines due to a combination of high cyclic contact stresses, long expected component lifetimes, corrosive environment, and the high consequence of fatigue failure. The cost of these rolling elements increases exponentially with the decrease in allowable flaw size for service applications. Hence the range of 3D non-planar surface flaw geometries subject to RCF is simulated to determine the critical flaw size (CFS) or the largest allowable flaw that does not grow under service conditions. This dissertation is a numerical and experimental investigation of surface flaws in ceramic balls subjected to RCF and has resulted in the following analyses: Crack Shape Determination: the nucleation of surface flaws from ball impact that occurs during the manufacturing process is simulated. By examining the subsurface Hertzian stresses between contacting spheres, their applicability to predicting and characterizing crack size and shape is established. It is demonstrated that a wide range of cone and partial cone cracks, observed in practice, can be generated using the proposed approaches. RCF Simulation: the procedure and concerns in modeling nonplanar 3D cracks subject to RCF using FEA for stress intensity

  1. 75 FR 30856 - Ball Bearings From Japan and the United Kingdom

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-02

    ... FR 68036 (Nov. 8, 2002). In accordance with sections 201.16(c) and 207.3 of the Commission's rules... COMMISSION [Investigation Nos. 731-TA-394-A & 399-A (Second Review) (Third Remand)] Ball Bearings From Japan... antidumping orders on ball bearings from Japan and the United Kingdom. For further information concerning...

  2. Carbon microspheres as ball bearings in aqueous-based lubrication.

    PubMed

    St Dennis, J E; Jin, Kejia; John, Vijay T; Pesika, Noshir S

    2011-07-01

    We present an exploratory study on a suspension of uniform carbon microspheres as a new class of aqueous-based lubricants. The surfactant-functionalized carbon microspheres (∼0.1 wt %) employ a rolling mechanism similar to ball bearings to provide low friction coefficients (μ ≈ 0.03) and minimize surface wear in shear experiments between various surfaces, even at high loads and high contact pressures. The size range, high monodispersity, and large yield stress of the C(μsphere), as well as the minimal environmental impact, are all desirable characteristics for the use of a C(μsphere)-SDS suspension as an alternative to oil-based lubricants in compatible devices and machinery.

  3. Development of high efficiency ball-bearing turbocharger

    SciTech Connect

    Miyashita, K.; Kurasawa, M.; Matsuoka, H.; Ikeya, N.

    1987-01-01

    Turbochargers have become very popular on passenger cars since the first mass-produced turbocharged passenger cars were put on market in Japan in 1979. Turbo lag is one of the most serious problem since the first mass-production started. Several new technologies such as a variable geometry turbocharger, ceramic turbocharger, etc. have been introduced to improve acceleration performance. A variable geometry turbocharger changes the area of gas flow passage and increases exhaust gas speed at low engine speed. A ceramic turbocharger reduces inertia moment of a turbine wheel and shaft. Turbocharger mechanical efficiency has equal importance as compressor efficiency and turbine efficiency. This paper describes the test results of ball bearing turbochargers.

  4. 76 FR 58768 - Ball Bearings and Parts Thereof From France, Germany, and Italy; Amended Final Results of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-22

    ... Reviews, 76 FR 52937 (August 24, 2011) (Final Results). The period of review is May 1, 2009, through April... International Trade Administration Ball Bearings and Parts Thereof From France, Germany, and Italy; Amended... ball bearings and parts thereof from France, Germany, and Italy. See Ball Bearings and Parts...

  5. Comparison of experimental and predicted performance of 150-millimeter-bore solid and drilled ball bearings to 3 million DN

    NASA Technical Reports Server (NTRS)

    Scibbe, H. W.; Munson, H. E.

    1974-01-01

    Seven 150-millimeter-bore ball bearings were run under 8900-newton (2000-lbf) thrust load at speeds from 6670 to 20,000 rpm (1 million to 3 million DN). Four of the bearings had conventional solid balls, and three bearings had drilled (cylindrically hollow) balls with 50-percent mass reduction. The bearings were under-race cooled and slot lubricated with a type 2 ester oil at flow rates from 4.35 x 0.001 to 5.94 x 0.001 cubic meter/min (1.15 to 1.57 gal/min). Friction torque and temperature were measured on all bearings. While there was considerable spread in the temperature data, the drilled ball bearings tended to run slightly cooler than the solid ball bearings at higher speeds. No significant difference in torque was noted, however, between the solid and drilled ball bearings. One bearing of each type was rerun at 17,800-newton (4000-lbf) thrust load. The solid ball bearings performed satisfactorily at 3 million DN. However, at about 2 million DN the drilled ball bearing experienced a broken ball, and cracks appeared in other balls as a result of flexure fatigue. Metallurgical examination of the cracked balls indicated a brittle structure in the bore of the drilled balls.

  6. Evaluation of outer race tilt and lubrication on ball wear and SSME bearing life reductions

    NASA Technical Reports Server (NTRS)

    Kannel, J. W.; Merriman, T. L.; Stockwell, R. D.; Dufrane, K. F.

    1983-01-01

    Several aspects of the SSME bearing operation were evaluated. The possibility of elastohydrodynamics (EHD) lubrication with a cryogenic fluid was analyzed. Films as thick as .61 microns were predicted with one theory which may be thick enough to provide hydrodynamic support. The film formation, however, is heavily dependent on good surface finish and a low bulk bearing temperature. Bearing dynamics to determine if the radial stiffness of a bearing which are dependent on bearing misalignment were analyzed. Four ball tests were conducted at several environmental conditions from an LN2 bath to 426 C in air. Surface coatings and ball materials are evaluated. Severe wear and high friction are measured for all ball materials except when the balls have surface lubricant coatings.

  7. Characterization of Lubricants on Ball Bearings by FT-IR Using an Integrating Sphere

    NASA Technical Reports Server (NTRS)

    Street, K. W.; Pepper, S. V.; Wright, A. A.; Grady, B.

    2007-01-01

    Fourier Transform-Infrared reflectance microspectroscopy has been used extensively for the examination of coatings on nonplanar surfaces such as ball bearings. While this technique offers considerable advantages, practical application has many drawbacks, some of which are easily overcome by the use of integrating sphere technology. This paper describes the use of an integrating sphere for the quantification of thin layers of lubricant on the surface of ball bearings and the parameters which require optimization in order to obtain reliable data. Several applications of the technique are discussed including determination of lubricant load on 12.7 mm steel ball bearings and the examination of degraded lubricant on post mortem specimens.

  8. 76 FR 327 - Ball Bearings and Parts Thereof From France: Partial Rescission of Antidumping Duty...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-04

    ..., 75 FR 37759 (June 30, 2010). Rescission of Review in Part In accordance with 19 CFR 351.213(d)(1... International Trade Administration Ball Bearings and Parts Thereof From France: Partial Rescission of... (the Department) initiated an administrative review of the antidumping duty order on ball...

  9. Measurement of separator contact forces in ball bearings using a derotation prism

    NASA Technical Reports Server (NTRS)

    Nypan, L. J.

    1978-01-01

    A derotation prism was used to produce a stationary image of balls deflecting a portion of the separator. Ball to cage contact forces in a 110 mm bearing at speeds to 12,000 rpm were found to be 25 N (five lb) maximum. Inner race land contact force was found to vary up to 20 N (four lb).

  10. Nonlinear dynamic model for skidding behavior of angular contact ball bearings

    NASA Astrophysics Data System (ADS)

    Han, Qinkai; Chu, Fulei

    2015-10-01

    A three-dimensional nonlinear dynamic model is proposed to predict the skidding behavior of angular contact ball bearings under combined load condition. The centrifugal and gyroscopic effects induced by ball rotation and revolution, Hertz contact between the ball and inner/outer races, discontinuous contact between the ball and cage and elastohydrodynamic lubrication are considered in the model. Through comparisons with the tested results of the reference, the dynamic model is verified. Based upon these, variations of ball slipping speed with time and space are discussed for the bearing under combined load condition. It is shown that radial load leads to the fluctuations in the slipping velocity of the ball contacting with inner/outer races, especially for the ball in load-decreasing regions. Adding the radial load would significantly increase the amplitude and range of slipping velocity, indicating that the skidding becomes more serious. As the ball still withstands contact load in the load-decreasing region, large slipping velocity would increase the temperature of both bearing and lubricant oil, intensify the wear and then might shorten the bearing service life. Therefore, the radial load should be considered carefully in the design and monitoring of rotating machinery.

  11. Analysis of Black Bearing Balls from a Space Shuttle Body Flap Actuator

    NASA Technical Reports Server (NTRS)

    Sovinski, Marjorie F.; Street, Kenneth W.

    2005-01-01

    A significantly deteriorated ball bearing mechanism from a body flap actuator on Space Shuttle OV-103 was disassembled and the balls submitted for analysis in conjunction with Return to Flight activities. The OV-103 balls, referred to as the "black balls", were subjected to X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) and Raman micro spectroscopy, surface profilometry, and optical and electron microscopy. The spectroscopic results in combination with microscopy analysis allowed a determination of the lubricant degradation pathway. The chemical attack mechanism does not adequately explain the unique visual appearance of the black balls. Numerous efforts have unsuccessfully focused on duplication of the phenomena causing this unique surface structure and appearance of the black balls. Further detail will be presented supporting these conclusions along with plausible explanations of the unique black appearance to the balls.

  12. Evaluation of load-life relation with ball bearings at 500 F

    NASA Technical Reports Server (NTRS)

    Parker, R. J.; Zaretsky, E. V.; Bamberger, E. N.

    1973-01-01

    A survey of the literature suggests that a stress-life exponent of approximately 12 is typical of vacuum-processed steels for ball bearings rather than the exponent of 9 which has been generally accepted by the bearing industry and bearing users. Tests run with vacuum-degassed AISI 52100 balls in the five-ball fatigue tester at four maximum Hertz stress levels in the range from 650,000 to 875,000 psi showed good agreement with the literature. However, tests run with consumable-electrode vacuum melted AISI M-50 steel angular-contact ball bearings at 500 F at three thrust loads did not show significant deviation from the accepted ninth power stress-life relation.

  13. Analysis of a spacecraft instrument ball bearing assembly lubricated by a perfluoroalkylether

    NASA Technical Reports Server (NTRS)

    Morales, W.; Jones, W. R., Jr.; Buckley, D. H.

    1986-01-01

    An analysis of a spacecraft instrument ball bearing assembly, subjected to a scanning life test, was performed to determine the possible case of rotational problems involving these units aboard several satellites. The analysis indicated an ineffective transfer of a fluorinated liquid lubricant from a phenolic retainer to the bearing balls. Part of the analysis led to a novel HPLC separation method employing a fluorinated mobile phase in conjunction with silica based size exclusion columns.

  14. Research on the Mechanical Properties of "Z" Type Double-Decker Ball Bearings.

    PubMed

    Yu, Chengtao; Xu, Longxiang; Yu, Xudong

    2014-01-01

    The mechanical model of a "Z" type double-decker ball bearing under the action of radial load is established in this paper on the basis of the Hertz contact theory. According to the security contact angle theory, the influences of inner and outer bearings' internal clearances on the bearing's static load carrying capacity, radial deformation, radial stiffness, and load distribution of balls are analyzed. This model is verified in both stationary and rotational loading experiments. Moreover, the simulation results show that the static load carrying capacity of Z type bearing is smaller than that of either inner bearing or outer bearing that is contributed to compose the Z type bearing. The static load carrying capacity of a Z type bearing reduces with the increase of the inner and outer bearings' internal clearance. These simulation results also indicate that the contact angle of the maximum loaded ball in the outer bearing easily exceeds its security contact angle compared with the inner bearing, which, as the main factor, may cause the Z type bearing to overload and to fail. In this sense, the investigated Z type bearings are unfit to apply to situations with heavy load, high speed, or high precision.

  15. Effect of Internal Clearance on Load Distribution and Life of Radially Loaded Ball and Roller Bearings

    NASA Technical Reports Server (NTRS)

    Oswald, Fred B.; Zaretsky, Erwin V.; Poplawski, Joseph V.

    2012-01-01

    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.

  16. 75 FR 62763 - Ball Bearings and Parts Thereof From Germany: Amended Final Results of Antidumping Duty...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-13

    ... Reviews and Rescission of Reviews in Part, 73 FR 52823 (September 11, 2008). SKF USA Inc., SKF France S.A... International Trade Administration Ball Bearings and Parts Thereof From Germany: Amended Final Results of... bearings and parts thereof from Germany. See SKF USA Inc. v. United States, Slip Op. 10-76 (CIT 2010)....

  17. 76 FR 57019 - Ball Bearings and Parts Thereof From France, Germany and Italy: Final Results of Sunset Reviews...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-15

    ..., and Parts Thereof From France, 54 FR 20902 (May 15, 1989), Antidumping Duty Orders: Ball Bearings... Germany, 54 FR 20900 (May 15, 1989), and Antidumping Duty Orders: Ball Bearings and Cylindrical Roller Bearings, and Parts Thereof From Italy, 54 FR 20903 (May 15, 1989). On August 1, 2011, the...

  18. Stiffness matrix formulation for double row angular contact ball bearings: Analytical development and validation

    NASA Astrophysics Data System (ADS)

    Gunduz, Aydin; Singh, Rajendra

    2013-10-01

    Though double row angular contact ball bearings are widely used in industrial, automotive, and aircraft applications, the scientific literature on double row bearings is sparse. It is also shown that the stiffness matrices of two single row bearings may not be simply superposed to obtain the stiffness matrix of a double row bearing. To overcome the deficiency in the literature, a new, comprehensive, analytical approach is proposed based on the Hertzian theory for back-to-back, face-to-face, and tandem arrangements. The elements of the five-dimensional stiffness matrix for double row angular contact ball bearings are computed given either the mean bearing displacement or the mean load vector. The diagonal elements of the proposed stiffness matrix are verified with a commercial code for all arrangements under three loading scenarios. Some changes in stiffness coefficients are investigated by varying critical kinematic and geometric parameters to provide more insight. Finally, the calculated natural frequencies of a shaft-bearing experiment are successfully compared with measurements, thus validating the proposed stiffness formulation. For double row angular contact ball bearings, the moment stiffness and cross-coupling stiffness terms are significant, and the contact angle changes under loads. The proposed formulation is also valid for paired (duplex) bearings which behave as an integrated double row unit when the surrounding structural elements are sufficiently rigid.

  19. Arched-outer-race ball-bearing analysis considering centrifugal forces

    NASA Technical Reports Server (NTRS)

    Hamrock, B. J.; Anderson, W. J.

    1972-01-01

    A first-order thrust load analysis that considers centrifugal forces but which neglects gyroscopics, elastohydrodynamics, and thermal effects was performed. The analysis was applied to a 150-mm-bore angular-contact ball bearing. Fatigue life, contact loads, and contact angles are shown for conventional and arched bearings. The results indicate that an arched bearing is highly desirable for high-speed applications. In particular, at an applied load of 4448 n (1000 lb) and a DN value of 3 million (20,000 rpm) the arched bearing shows an improvement in life of 306 percent over that of a conventional bearing.

  20. Evaluation of drilled-ball bearings at DN values to three million. 2: Experimental skid study and endurance tests

    NASA Technical Reports Server (NTRS)

    Holmes, P. W.

    1972-01-01

    Both drilled-and solid-ball 120-mm-bore bearings were tested at speeds up to 24,000 rpm to determine skid characteristics. The thrust loads were varied from 5000 lb down to 370 lb. No gross skidding occurred, and the behavior of the two bearing types was generally similar; however, two drilled-ball bearing failures occurred during the skid tests. In the endurance tests, 25 cycles of start, run (for one hour), and stop were completed before a drilled-ball bearing failed. In all three cases, the ball had failed in flexure fatigue.

  1. Filtration effects on ball bearing life and condition in a contaminated lubricant

    NASA Technical Reports Server (NTRS)

    Loewenthal, S. H.; Moyer, D. W.

    1978-01-01

    Ball bearings were fatigue tested with a noncontaminated MIL-L-23699 lubricant and with a contaminated MIL-L-23699 lubricant under four levels of filtration. The test filters had absolute particle removal ratings of 3, 30, 49, and 105 microns. Aircraft turbine engine contaminants were injected into the filter's supply line at a constant rate of 125 milligrams per bearing hour. Bearing life and running track condition generally improved with finer filtration. The experimental lives of 3- and 30-micron filter bearings were statistically equivalent, approaching those obtained with the noncontaminated lubricant bearings. Compared to these bearings, the lives of the 49-micron bearings were statistically lower. The 105-micron bearings experienced gross wear. The degree of surface distress, weight loss, and probable failure mode were dependent on filtration level, with finer filtration being clearly beneficial.

  2. Filtration effects on ball bearing life and condition in a contaminated lubricant

    NASA Technical Reports Server (NTRS)

    Loewenthal, S. H.; Moyer, D. W.

    1978-01-01

    Ball bearings were fatigue tested with a noncontaminated lubricant and with a contaminated lubricant under four levels of filtration. The test filters had absolute particle removal ratings of 3, 30, 49, and 105 microns. Aircraft turbine engine contaminants were injected into the filter's supply line at a constant rate of 125 milligrams per bearing hour. Bearing life and running track condition generally improved with finer filtration. The experimental lives of 3 and 30 micron filter bearings were statistically equivalent, approaching those obtained with the noncontaminated lubricant bearings. Compared to these bearings, the lives of the 49 micron bearings were statistically lower. The 105 micron bearings experienced gross wear. The degree of surface distress, weight loss, and probable failure mode were dependent on filtration level, with finer filtration being clearly beneficial.

  3. Effect of Silicon Nitride Balls and Rollers on Rolling Bearing Life

    NASA Technical Reports Server (NTRS)

    Zaretsky, Erwin V.; Vlcek, Brian L.; Hendricks, Robert C.

    2005-01-01

    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 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 percent for deep-groove bearings, 41 percent for angular-contact bearings, and 28 percent for cylindrical roller bearings.

  4. The properties of thin-section, four-point-contact ball bearings in space

    NASA Technical Reports Server (NTRS)

    Rowntree, R. A.

    1985-01-01

    Thin section, four-point-contact ball bearings are increasinly employed in spacecraft mechanisms because of the potential advantages they offer. However, litte was previously known of their torque, thermal conductance and stiffness properties at conditions anticipated for their use in space. An investigation of these properties are described. It was found that frictional (Coulomb) torque, thermal conductance and stiffness all show marked dependence on the bearing preload, the housing design, the bearing external fit (i.e., free fit or interference) and on the thermal gradient across the races. Optimum bearing performance is achieved only if these properties are well understood. The necessary data to understand these properties are provided.

  5. 75 FR 41435 - Ball Bearings and Parts Thereof From Germany: Notice of Court Decision Not in Harmony With Final...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-16

    ... and Rescission of Reviews in Part, 73 FR 52823 (September 11, 2008). SKF USA Inc., SKF France S.A... International Trade Administration Ball Bearings and Parts Thereof From Germany: Notice of Court Decision Not in... the administrative review of the antidumping duty order on ball bearings and parts thereof...

  6. Comparison of tungsten carbide and stainless steel ball bearings for grinding single maize kernels in a reciprocating grinder

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Reciprocating grinders can grind single maize kernels by shaking the kernel in a vial with a ball bearing. This process results in a grind quality that is not satisfactory for many experiments. Tungesten carbide ball bearings are nearly twice as dense as steel, so we compared their grinding performa...

  7. 76 FR 60871 - Ball Bearings and Parts Thereof From France, Germany, and Italy; Termination of Five-Year Reviews

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-30

    ... deadline.'' (76 FR 57019). Accordingly, pursuant to section 751(c) of the Tariff Act of 1930 (19 U.S.C... COMMISSION Ball Bearings and Parts Thereof From France, Germany, and Italy; Termination of Five-Year Reviews... ball bearings and parts thereof from France, Germany, and Italy would be likely to lead to...

  8. Probabilistic Analysis of Space Shuttle Body Flap Actuator Ball Bearings

    NASA Technical Reports Server (NTRS)

    Oswald, Fred B.; Jett, Timothy R.; Predmore, Roamer E.; Zaretsky, Erwin V.

    2008-01-01

    A probabilistic analysis, using the 2-parameter Weibull-Johnson method, was performed on experimental life test data from space shuttle actuator bearings. Experiments were performed on a test rig under simulated conditions to determine the life and failure mechanism of the grease lubricated bearings that support the input shaft of the space shuttle body flap actuators. The failure mechanism was wear that can cause loss of bearing preload. These tests established life and reliability data for both shuttle flight and ground operation. Test data were used to estimate the failure rate and reliability as a function of the number of shuttle missions flown. The Weibull analysis of the test data for the four actuators on one shuttle, each with a 2-bearing shaft assembly, established a reliability level of 96.9 percent for a life of 12 missions. A probabilistic system analysis for four shuttles, each of which has four actuators, predicts a single bearing failure in one actuator of one shuttle after 22 missions (a total of 88 missions for a 4-shuttle fleet). This prediction is comparable with actual shuttle flight history in which a single actuator bearing was found to have failed by wear at 20 missions.

  9. Probabilistic Analysis of Space Shuttle Body Flap Actuator Ball Bearings

    NASA Technical Reports Server (NTRS)

    Oswald, Fred B.; Jett, Timothy R.; Predmore, Roamer E.; Zaretsky, Erin V.

    2007-01-01

    A probabilistic analysis, using the 2-parameter Weibull-Johnson method, was performed on experimental life test data from space shuttle actuator bearings. Experiments were performed on a test rig under simulated conditions to determine the life and failure mechanism of the grease lubricated bearings that support the input shaft of the space shuttle body flap actuators. The failure mechanism was wear that can cause loss of bearing preload. These tests established life and reliability data for both shuttle flight and ground operation. Test data were used to estimate the failure rate and reliability as a function of the number of shuttle missions flown. The Weibull analysis of the test data for a 2-bearing shaft assembly in each body flap actuator established a reliability level of 99.6 percent for a life of 12 missions. A probabilistic system analysis for four shuttles, each of which has four actuators, predicts a single bearing failure in one actuator of one shuttle after 22 missions (a total of 88 missions for a 4-shuttle fleet). This prediction is comparable with actual shuttle flight history in which a single actuator bearing was found to have failed by wear at 20 missions.

  10. The in-vacuo torque performance of dry-lubricated ball bearings at cryogenic temperatures

    NASA Technical Reports Server (NTRS)

    Gould, S. G.; Roberts, E. W.

    1989-01-01

    The performance of dry-lubricated, angular contact ball bearings in vacuum at a temperature of 20 degrees K has been investigated, and is compared with the in-vacuo performance at room temperatures. Bearings were lubricated using dry-lubricant techniques which have been previously established for space applications involving operations at or near room temperature. Comparative tests were undertaken using three lubricants: molybdenum disulphide, lead, and PTFE. Results obtained using the three lubricants are presented.

  11. Analysis of an arched outer-race ball bearing considering centrifugal forces

    NASA Technical Reports Server (NTRS)

    Hamrock, B. J.; Anderson, W. J.

    1972-01-01

    A Newton-Raphson method of iteration was used in evaluating the radial and axial projection of the distance between the ball center and the outer raceway groove curvature center (V and W). Fatigue life evaluations were made. The similar analysis of a conventional bearing can be directly obtained from the arched bearing analysis by simply letting the amount of arching be zero (g = 0) and not considering equations related to the unloaded half of the outer race. The analysis was applied to a 150-mm angular contact ball bearing. Results for life, contact loads, and angles are shown for a conventional bearing (g = 0) and two arched bearings (g = 0.127 mm (0.005 in.), and 0.254 mm (0.010 in.)). The results indicate that an arched bearing is highly desirable for high speed applications. In particular, for a DN value of 3 million (20,000 rpm) and an applied axial load of 4448 N (1000 lb), an arched bearing shows an improvement in life of 306 percent over that of a conventional bearing. At 4.2 million DN (28,000 rpm), the corresponding improvement is 340 percent. It was also found for low speeds, the arched bearing does not offer the advantages that it does for high speed applications.

  12. A Study on the Effects of Ball Defects on the Fatigue Life in Hybrid Bearings

    NASA Technical Reports Server (NTRS)

    Tang, Ching-Yao; Foerster, Chad E.; O'Brien, Michael J.; Hardy, Brian S.; Goyal, Vinay K.; Nelson, Benjamin A.; Robinson, Ernest Y.; Ward, Peter C.; Hilton, Michael R.

    2014-01-01

    Hybrid ball bearings using silicon nitride ceramic balls with steel rings are increasingly being used in space mechanism applications due to their high wear resistance and long rolling contact fatigue life. However, qualitative and quantitative reports of the effects of ball defects that cause early fatigue failure are rare. We report on our approach to study these effects. Our strategy includes characterization of defects encountered in use, generation of similar defects in a laboratory setting, execution of full-scale bearing tests to obtain lifetimes, post-test characterization, and related finite-element modeling to understand the stress concentration of these defects. We have confirmed that at least one type of defect of appropriate size can significantly reduce fatigue life. Our method can be used to evaluate other defects as they occur or are encountered.

  13. 77 FR 33159 - Ball Bearings and Parts Thereof From France, Germany, and Italy: Preliminary Results of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-05

    ... Department published the antidumping duty orders on ball bearings and parts thereof from France (54 FR 20902), Germany (54 FR 20900), and Italy (54 FR 20903) in the ] Federal Register. On June 28, 2011, in accordance... Request for Revocation in Part, 76 FR 37781 (June 28, 2011).\\1\\ \\1\\ On July 16, 2011, we revoked...

  14. 77 FR 53844 - Ball Bearings and Parts Thereof From France and Italy: Rescission of Antidumping Duty...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-04

    ... Duty Administrative Reviews and Request for Revocations in Part, 77 FR 40565 (July 10, 2012... International Trade Administration Ball Bearings and Parts Thereof From France and Italy: Rescission of... parts thereof from France and Italy. The period of review is May 1, 2011, through September 14, 2011....

  15. 76 FR 798 - Ball Bearings From Japan and the United Kingdom

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-06

    ... and the United Kingdom, Inv. Nos. 731-TA-394-A & 399-A (Second Review) (Third Remand), USITC Pub. 4194... COMMISSION [Investigation Nos. 731-TA-394-A & 399-A (Second Review) (Fourth Remand)] Ball Bearings From Japan... 201, subparts A through E (19 CFR part 201), and part 207, subpart A (19 CFR part 207)....

  16. Two Magnets and a Ball Bearing: A Simple Demonstration of the Methods of Images.

    ERIC Educational Resources Information Center

    Poon, W. C. K.

    2003-01-01

    Investigates the behavior of a bar magnet with a steel ball bearing on one pole as it approaches another bar magnet. Maps the problem onto electrostatics and explains observations based on the behavior of point charges near an isolated, uncharged sphere. Offers a simple demonstration of the method of images in electrostatics. (Author/NB)

  17. An evaluation of grease ball bearing lubricants in vacuum

    NASA Technical Reports Server (NTRS)

    Demorest, K. E.; Mcmurtrey, E. L.

    1976-01-01

    Because many future spacecraft will require mechanisms to operate for long periods of time in environments which are inimical to most bearing lubricants, a series of tests has been started to evaluate 25 grease type lubricants in R-4 size bearings in vacuum at ambient temperature for a 1 year period. Four repetitions of each test are made to provide statistical samples. These tests will be used to select from two to five lubricants for 5 year tests in the same environment. At the present time fifteen test sets have been completed and five sets are being tested. The best results to date have been obtained with perfluoropolyether greases.

  18. A Method for Evaluating Dynamical Friction in Linear Ball Bearings

    PubMed Central

    Fujii, Yusaku; Maru, Koichi; Jin, Tao; Yupapin, Preecha P.; Mitatha, Somsak

    2010-01-01

    A method is proposed for evaluating the dynamical friction of linear bearings, whose motion is not perfectly linear due to some play in its internal mechanism. In this method, the moving part of a linear bearing is made to move freely, and the force acting on the moving part is measured as the inertial force given by the product of its mass and the acceleration of its centre of gravity. To evaluate the acceleration of its centre of gravity, the acceleration of two different points on it is measured using a dual-axis optical interferometer. PMID:22163457

  19. Performance of 75 millimeter-bore arched outer-race ball bearings

    NASA Technical Reports Server (NTRS)

    Coe, H. H.; Hamrock, B. J.

    1976-01-01

    An investigation was performed to determine the operating characteristics of 75-mm bore, arched outer-race bearings, and to compare the data with those for a similar, but conventional, deep groove ball bearing. Further, results of an analytical study, made using a computer program developed previously, were compared with the experimental data. Bearings were tested up to 28,000 rpm shaft speed with a load of 2200 N (500 lb). The amount of arching was 0.13, 0.25, and 0.51 mm (.005, .010, and .020 in.). All bearings operated satisfactorily. The outer-race temperatures and the torques, however, were consistently higher for the arched bearings than for the conventional bearing.

  20. How to apply life adjustment factors for ball and roller bearings.

    NASA Technical Reports Server (NTRS)

    Crecelius, W. J., Jr.; Harris, T. A.; Moyer, C. A.; Parker, R. J.; Zaretsky, E. V.; Sherlock, J. J.

    1972-01-01

    Practical problems applicable to the selection, design, and lubrication of rolling-element bearings are presented and discussed. The solutions to these problems are based upon the new ASME Engineering Design Guide - Life Adjustment Factors for Ball and Roller Bearings. Design and selection criteria are based upon materials and processing factors such as melting practice, metalworking, and heat treatment. Environmental factors considered include bearing misalignment and speed. Selection of a lubricant is based upon elastohydrodynamic lubrication principles in addition to lubricant type and chemistry.

  1. Comparison of rotational speeds and torque properties between air-bearing and ball-bearing air-turbine handpieces.

    PubMed

    Taira, M; Wakasa, K; Yamaki, M; Matsui, A

    1989-06-01

    We examined the effects of air pressure on the free-running speed of air-bearing and torque-type ball-bearing air-turbine handpieces. The air pressure for the former should be kept at a certain high level to maintain the stable super-thin air-bearing film and to provide the quasi-constant speed of around 420,000 to 480,000 rpm. On the other hand, the air pressure for the latter could be adjusted to provide some varieties of speeds, ranging from about 150,000 to 320,000 rpm. Subsequently, to compare torque properties and cutting effectiveness between these two handpieces, weight-load cutting tests were conducted, using a glass-ceramic workpiece and a commercial diamond point. It was confirmed that the air-bearing handpiece had the lower torque power but exhibited better cutting effectiveness, compared with its counterpart.

  2. A parametric heat transfer study for cryogenic ball bearings in SSME HPOTP

    NASA Technical Reports Server (NTRS)

    Chyu, Mingking K.

    1989-01-01

    A numerical modeling is to examine the effects of coolant convective heat transfer coefficient and frictional heating on the local temperature characteristics of a ball element in Space Shuttle Main Engine (SSME) High Pressure Oxidizer Turbopump (HPOTP) bearing. The present modeling uses a control-volume based, finite-difference method to solve the non-dimensionalized heat conduction equation in spherical coordinate system. The dimensionless temperature is found as a function of Biot number, heat flux ratio between the two race contacts, and location in the ball. The current results show that, for a given cooling capability, the ball temperature generally increases almost linearly with the heat input from the race-contacts. This increase is always very high at one of the two contacts. An increase in heat transfer coefficient generally reduces the ball temperature and alleviates the temperature gradient, except for the regions very close to the race contacts. For a 10-fold increase of heat transfer coefficient, temperature decrease is 35 percent for the average over entire ball, and 10 percent at the inner-race contact. The corresponding change of temperature gradient displays opposing trends between the regions immediately adjacent to the contacts and the remaining portion of the ball. The average temperature gradient in the vicinity of both contacts increases approximately 70 to 100 percent. A higher temperature gradient produces excessive thermal stress locally which may be detrimental to the material integrity. This, however, is the only unfavorable issue for an increase of heat transfer coefficient.

  3. A comparison of the performance of solid and liquid lubricants in oscillating spacecraft ball bearings

    NASA Technical Reports Server (NTRS)

    Gill, S.

    1994-01-01

    The European Space Tribology Laboratory (ESTL) has been engaged in a program to compare the performance of oscillating ball bearings when lubricated by a number of space lubricants, both liquid and solid. The results have shown that mean torque levels are increased by up to a factor of five above the normal running torque, and that often torque peaks of even greater magnitudes are present at the ends of travel. It is believed that these effects are caused by a build-up of compacted debris in the contact zone, thus reducing the ball/race conformity ratio.

  4. Bearing selection in ball-rolling dung beetles: is it constant?

    PubMed

    Baird, Emily; Byrne, Marcus J; Scholtz, Clarke H; Warrant, Eric J; Dacke, Marie

    2010-11-01

    Ball rolling in dung beetles is thought to have evolved as a means to escape intense inter- and intra-specific competition at the dung pile. Accordingly, dung beetles typically roll along a straight-line path away from the pile, this being the most effective escape strategy for transporting dung to a suitable burial site. In this study, we investigate how individual diurnal dung beetles, Scarabaeus (Kheper) nigroaeneus, select the compass bearing of their straight-line rolls. In particular, we examine whether roll bearings are constant with respect to geographic cues, celestial cues, or other environmental cues (such as wind direction). Our results reveal that the roll bearings taken by individual beetles are not constant with respect to geographic or celestial references. Environmental cues appear to have some influence over bearing selection, although the relationship is not strong. Furthermore, the variance in roll bearing that we observe is not affected by the presence or absence of other beetles. Thus, rather than being constant for individual beetles, bearing selection varies each time a beetle makes a ball and rolls it away from the dung pile. This strategy allows beetles to make an efficient escape from the dung pile while minimizing the chance of encountering competition.

  5. Design of High-speed Wear Lifetime Tester of the Instrument Ball Bearings

    NASA Astrophysics Data System (ADS)

    Liu, C. H.; Gu, J. M.; Sun, Y.; Chen, X. Y.

    2006-10-01

    The instrument ball bearings are the key components of movable components for various kinds of measuring and control instruments; they often operate in the environmental condition of high-speed and light preload. In general, the non metal, disposable oilimpregnated retainer material has been used for these kinds of high precision miniature bearing. The engineering practice shows that the common failure mode of them is the wear which appears under the condition of insufficient lubrication condition. As the results, the vibration and noise will be enlarged, so does the frictional torque, which makes the ball bearings to lose its original working accuracy. It is the lifetime test of bearings that can enable the designers and manufacturers to chose the material of the bearing properly, optimize the product structure, mend the manufacturing technique process, and to enhance the technical level of the bearing products significantly. In this paper, the wear lifetime tester has been designed according to the requirements of the life test for the instrument ball bearings, which consists of the main body of tester, electric system, drive unit and computer measure and control system, etc. The motor spindle has been selected to drive the device which is supported by the aerostatic bearing; frequency conversion speed adjustment mode, its scope of rotating speed is between 0 and 10,000 rpm. A pair of bearings can be tested under the pure axial preload condition, the maximum load is up to 50N, the control accuracy is ±2% the scope of temperature control is up to 200°C. The variation of frictional torque on the bearing couple will be measured by an online torque transducer. The variation of power dissipation can be monitored under arbitrary speed by use of an on-line high-precision power meter. The wear and quality situation of the contact surface of the bearings will be reflected on these two parameters. Meanwhile, the values of temperature and vibration will also be monitored

  6. 76 FR 35401 - Ball Bearings and Parts Thereof From Japan and the United Kingdom: Notice of Court Decision Not...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-17

    ..., Germany, Italy, Japan, Singapore, and the United Kingdom, 70 FR 31531 (June 1, 2005). See also 19 CFR 351..., 70 FR 58183 (October 5, 2005), Ball Bearings and Parts Thereof From Japan and Singapore; Five-Year... Bearings, and Spherical Plain Bearings, and Parts Thereof From Japan, 54 FR 20904 (May 15, 1989),...

  7. Design and Operating Characteristics of High-Speed, Small-Bore, Angular-Contact Ball Bearings

    NASA Technical Reports Server (NTRS)

    Pinel, Stanley I.; Signer, Hans R.; Zaretsky, Erwin V.

    1998-01-01

    The computer program SHABERTH was used to analyze 35-mm-bore, angular-contact ball bearings designed and manufactured for high-speed turbomachinery applications. Parametric tests of the bearings were conducted on a high-speed, high-temperature bearing tester and were compared with the computer predictions. Four bearing and cage designs were studied. The bearings were lubricated either by jet lubrication or through the split inner ring with and without outer-ring cooling. The predicted bearing life decreased with increasing speed because of increased operating contact stresses caused by changes in contact angle and centrifugal load. For thrust loads only, the difference in calculated life for the 24 deg. and 30 deg. contact-angle bearings was insignificant. However, for combined loading, the 24 deg. contact-angle bearing gave longer life. For split-inner-ring bearings, optimal operating conditions were obtained with a 24 deg. contact angle and an inner-ring, land-guided cage, using outer-ring cooling in conjunction with low lubricant flow rates. Lower temperature and power losses were obtained with a single-outer-ring, land-guided cage for the 24 deg. contact-angle bearing having a relieved inner ring and partially relieved outer ring. Inner-ring temperatures were independent of lubrication mode and cage design. In comparison with measured values, reasonably good engineering correlation was obtained using the computer program SHABERTH for predicted bearing power loss and for inner- and outer-ring temperatures. The Parker formula for XCAV (used in SHABERTH, a measure of oil volume in the bearing cavity) may need to be refined to reflect bearing lubrication mode, cage design, and location of cage-controlling land.

  8. Test results and flight experience of ball bearing momentum and reaction wheels

    NASA Technical Reports Server (NTRS)

    Auer, W.

    1990-01-01

    The required satellite mission durations and levels of reliability have been considerably increased: While in the beginning of the 70's 3 to 5 year missions were planned, the standard is now 10 years with an expansion to 15 years and more for such programs as INTELSAT VII. Based on a 20 year test and flight experience with basically the same design, ball bearing momentum and reaction wheels with the required 15 year mission capability can be provided.

  9. Wear mechanisms found in angular contact ball bearings of the SSME's LOX turbopump

    NASA Astrophysics Data System (ADS)

    Chase, T. J.

    1992-07-01

    Extensive experimental investigations were carried out on used flight bearings of the Phase 2 high-pressure oxygen turbopump (HPOTP) of the Space Shuttle Main Engine (SSME) in order to determine the wear mechanisms, dominant wear modes, and their extent and causes. The report shows methodology, surface analysis techniques used, result, and discussion. The mode largely responsible for heavy bearing wear in LOX was identified as adhesive/shear peeling of the upper layers of bearing balls and rings. The mode relies on the mechanisms of scale formation, breakdown, and removal, all of which are greatly enhanced by the heavy oxidation environment of the HPOTP. Major causes of the high wear in bearings appear to be lubrication and cooling, both inadequate for the imposed conditions of operation. Numerous illustrations and evidence are given.

  10. Wear mechanisms found in angular contact ball bearings of the SSME's LOX turbopump

    NASA Technical Reports Server (NTRS)

    Chase, T. J.

    1992-01-01

    Extensive experimental investigations were carried out on used flight bearings of the Phase 2 high-pressure oxygen turbopump (HPOTP) of the Space Shuttle Main Engine (SSME) in order to determine the wear mechanisms, dominant wear modes, and their extent and causes. The report shows methodology, surface analysis techniques used, result, and discussion. The mode largely responsible for heavy bearing wear in LOX was identified as adhesive/shear peeling of the upper layers of bearing balls and rings. The mode relies on the mechanisms of scale formation, breakdown, and removal, all of which are greatly enhanced by the heavy oxidation environment of the HPOTP. Major causes of the high wear in bearings appear to be lubrication and cooling, both inadequate for the imposed conditions of operation. Numerous illustrations and evidence are given.

  11. 75 FR 26920 - Ball Bearings and Parts Thereof from France, Germany, Italy, Japan, and the United Kingdom...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-13

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF COMMERCE International Trade Administration Ball Bearings and Parts Thereof from France, Germany, Italy, Japan, and the United Kingdom: Preliminary Results of Antidumping Duty Administrative Reviews, Preliminary Results...

  12. Toward a 3D dynamic model of a faulty duplex ball bearing

    NASA Astrophysics Data System (ADS)

    Kogan, Gideon; Klein, Renata; Kushnirsky, Alex; Bortman, Jacob

    2015-03-01

    Bearings are vital components for safe and proper operation of machinery. Increasing efficiency of bearing diagnostics usually requires training of health and usage monitoring systems via expensive and time-consuming ground calibration tests. The main goal of this research, therefore, is to improve bearing dynamics modeling tools in order to reduce the time and budget needed to implement the health and usage monitoring approach. The proposed three-dimensional ball bearing dynamic model is based on the classic dynamic and kinematic equations. Interactions between the bodies are simulated using non-linear springs combined with dampers described by Hertz-type contact relation. The force friction is simulated using the hyperbolic-tangent function. The model allows simulation of a wide range of mechanical faults. It is validated by comparison to known bearing behavior and to experimental results. The model results are verified by demonstrating numerical convergence. The model results for the two cases of single and duplex angular ball bearings with axial deformation in the outer ring are presented. The qualitative investigation provides insight into bearing dynamics, the sensitivity study generalizes the qualitative findings for similar cases, and the comparison to the test results validates model reliability. The article demonstrates the variety of the cases that the 3D bearing model can simulate and the findings to which it may lead. The research allowed the identification of new patterns generated by single and duplex bearings with axially deformed outer race. It also enlightened the difference between single and duplex bearing manifestation. In the current research the dynamic model enabled better understanding of the physical behavior of the faulted bearings. Therefore, it is expected that the modeling approach has the potential to simplify and improve the development process of diagnostic algorithms. • A deformed outer race of a single axially loaded bearing is

  13. Bifurcations and hysteresis of varying compliance vibrations in the primary parametric resonance for a ball bearing

    NASA Astrophysics Data System (ADS)

    Zhang, Zhiyong; Chen, Yushu; Cao, Qingjie

    2015-08-01

    This paper investigates the bifurcation and resonant hysteresis of varying compliance (VC) vibrations in a rigid-rotor ball bearing system with Hertzian contact and radial internal bearing clearance. With the aid of arc-length continuation, the harmonic balance and alternating frequency time (HB-AFT) technique is employed to trace the branches of periodic responses, for which the stability is also investigated using Floquet theory. It is found that the soft resonant hysteresis resulted from the Hertzian contact resonance dominates the primary parametric resonance. In addition, this paper also demonstrates that the mechanism of the period doubling in the case of small bearing clearances is arisen from one to two parametrical internal resonance in the primary resonant area, which can lead nonlinear responses such as quasi-period and chaotic motions to the system, and the evolvements of these complex behaviors are also explored.

  14. Experimental Analysis of Damping and Tribological Characteristics of Nano-CuO Particle Mixed Lubricant in Ball Bearings

    NASA Astrophysics Data System (ADS)

    Prakash, E.; Sivakumar, K.

    2015-12-01

    Experimental analysis of damping capacity and tribological characteristics of nano CuO added Servosystem 68 lubricant is attempted. CuO nano particles were synthesized by aqueous precipitation method and characterized. Prior to dispersion into lubricant, CuO nano particles were coated with 0.2 wt.% surfactant (Span-80) to stabilize the nano fluid. Tribological characteristics of particle added lubricant were tested in ASTM D 4172 four ball wear tester. Scanning electron microscopy test results of worn surfaces of nano CuO particle added lubricant were smoother than base lubricant. The particle added lubricant was applied in a new ball bearing and three defected ball bearings. When particle added lubricant was used, the ball defected bearing's vibration amplitude was reduced by 21.94% whereas it was 16.46% for new bearing and was ≤ 11% for other defected bearings. The formation of protection film of CuO over ball surface and regime of full film lubrication near the ball zone were observed to be reason for improved damping of vibrations.

  15. Predicting steady-state temperature, life, skid, and film thickness in a greased preloaded hybrid ball bearing

    SciTech Connect

    Poplawski, J.V.; Atwell, D.R.; Lubas, M.J.; Odessky, V. |

    1996-04-01

    This paper describes the use of the SHABERTH computer program supplemented with experimental temperature and skid data to quantify steady-state bearing operation. Parametric studies on ball diameter and number, contact angle, curvature, grease type, and preload are presented with their influence on contact stress, fatigue life, skid load, film thickness, and inner and outer race temperatures. These results are compared for a steel versus hybrid bearing set in a DB and DFSL mounting. The method presented can be applied to the design of other steel and hybrid ball thrust bearing systems.

  16. Computation of Space Shuttle high-pressure cryogenic turbopump ball bearing two-phase coolant flow

    NASA Technical Reports Server (NTRS)

    Chen, Yen-Sen

    1990-01-01

    A homogeneous two-phase fluid flow model, implemented in a three-dimensional Navier-Stokes solver using computational fluid dynamics methodology is described. The application of the model to the analysis of the pump-end bearing coolant flow of the high-pressure oxygen turbopump of the Space Shuttle main engine is studied. Results indicate large boiling zones and hot spots near the ball/race contact points. The extent of the phase change of the liquid oxygen coolant flow due to the frictional and viscous heat fluxes near the contact areas has been investigated for the given inlet conditions of the coolant.

  17. Performance improvement of silicon nitride ball bearings by ion implantation. CRADA final report

    SciTech Connect

    Williams, J.M.; Miner, J.

    1998-03-01

    The present report summarizes technical results of CRADA No. ORNL 92-128 with the Pratt and Whitney Division of United Technologies Corporation. The stated purpose of the program was to assess the 3effect of ion implantation on the rolling contact performance of engineering silicon nitride bearings, to determine by post-test analyses of the bearings the reasons for improved or reduced performance and the mechanisms of failure, if applicable, and to relate the overall results to basic property changes including but not limited to swelling, hardness, modulus, micromechanical properties, and surface morphology. Forty-two control samples were tested to an intended runout period of 60 h. It was possible to supply only six balls for ion implantation, but an extended test period goal of 150 h was used. The balls were implanted with C-ions at 150 keV to a fluence of 1.1 {times} 10{sup 17}/cm{sup 2}. The collection of samples had pre-existing defects called C-cracks in the surfaces. As a result, seven of the control samples had severe spalls before reaching the goal of 60 h for an unacceptable failure rate of 0.003/sample-h. None of the ion-implanted samples experienced engineering failure in 150 h of testing. Analytical techniques have been used to characterize ion implantation results, to characterize wear tracks, and to characterize microstructure and impurity content. In possible relation to C-cracks. It is encouraging that ion implantation can mitigate the C-crack failure mode. However, the practical implications are compromised by the fact that bearings with C-cracks would, in no case, be acceptable in engineering practice, as this type of defect was not anticipated when the program was designed. The most important reason for the use of ceramic bearings is energy efficiency.

  18. Performance of integrated retainer rings in silicon micro-turbines with thrust style micro-ball bearings

    NASA Astrophysics Data System (ADS)

    Hergert, Robert J.; Hanrahan, Brendan; Ghodssi, Reza; Holmes, Andrew S.

    2013-06-01

    This work explores the performance of different silicon retainer ring designs when integrated into silicon micro-turbines (SMTs) incorporating thrust style bearings supported on 500 µm diameter steel balls. Experimental performance curves are presented for SMTs with rotor diameters of 5 mm and 10 mm, each with five different retainer designs varying in mechanical rigidity, ball pocket shape and ball complement. It was found that the different retainer designs yielded different performance curves, with the closed pocket designs consistently requiring lower input power for a given rotation speed, and the most rigid retainers giving the best performance overall. Both 5 mm and 10 mm diameter devices have shown repeatable performance at rotation speeds up to and exceeding 20 000 RPM with input power levels below 2 W, and devices were tested for over 2.5 million revolutions without failure. Retainer rings are commonly used in macro-scale bearings to ensure uniform spacing between the rolling elements. The integration of retainers into micro-bearings could lower costs by reducing the number of balls required for stable operation, and also open up the possibility of ‘smart’ bearings with integrated sensors to monitor the bearing status.

  19. Lubrication of 35-millimeter-bore ball bearings of several designs to 2.5 million DN

    NASA Technical Reports Server (NTRS)

    Schuller, F. T.

    1983-01-01

    Parametric tests were conducted with 35mm bore, angular contact ball bearings with either a single or double outer and guided cage. The bearings were either lubricated by oil jets or employed inner ring lubrication. Outer ring cooling was added in selected tests. Lubricant flow to the bearing ranged from 300 to 1900 cc/min. All bearings were successfully run at speeds to 2.5 million DN. Increasing the lubricant flow decreased bearing ring temperatures but increased bearing power lines. The power loss and race temperatures of a jet lubricated with double outer land guided cage were always higher than those of the single land guided design at similar test conditions. The lowest bearing operating temperatures were achieved when inner ring lubrication and outer ring cooling were combined. It is found that cage slip of a double outer land guided cage is approximately twice that of a single outer land guided cage.

  20. Effect of cage design on characteristics of high-speed-jet-lubricated 35-millimeter-bore ball bearing. [turbojet engines

    NASA Technical Reports Server (NTRS)

    Schuller, F. T.; Pinel, S. I.; Signer, H. R.

    1980-01-01

    Parametric tests were conducted with a 35 mm bore angular contact ball bearing with a double outer land guided cage. Provisions were made for jet lubrication and outer-ring cooling of the bearing. Test conditions included a combined thrust and radial load at nominal shaft speeds of 48,000 rpm, and an oil-in temperature of 394 K (250 F). Successful operation of the test bearing was accomplished up to 2.5 million DN. Test results were compared with those obtained with similar bearing having a single outer land guided cage. Higher temperatures were generated with the double outer land guided cage bearing, and bearing power loss and cage slip were greater. Cooling the outer ring resulted in a decrease in overall bearing operating temperature.

  1. Grease test system for improved life of ball and roller bearings

    SciTech Connect

    Kleinlein, E. )

    1992-12-01

    An earlier developed system (FE9) for mechanodynamical testing of lubricating greases for ball and rolling bearings was used to assess, at temperatures between 100 and 200 C, grease lives of the following lubricating greases used in this test system: a standard grease, lithium soap, NLGI class 3 grease, a special grease for high temperatures, and a special grease not suitable for high temperatures. The paper describes the design of FE9 tester, the test rig, the test procedure, and the results of evaluation. It was found that lowering the test temperature led to a steeper increase of the grease life. Starved lubrication was found to be the major cause of failure at moderate temperatures, especially at the areas of sliding motion, such as betweeen cage and the rolling element. 9 refs.

  2. 75 FR 69402 - Ball Bearings and Parts Thereof From France, Germany, Italy, Japan, and the United Kingdom...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-12

    ... Revocation in Part, 75 FR 37759 (June 30, 2010). Rescission of Reviews in Part In accordance with 19 CFR 351..., Final Results of Changed-Circumstances Review, and Revocation of an Order in Part, 75 FR 53661... International Trade Administration Ball Bearings and Parts Thereof From France, Germany, Italy, Japan, and...

  3. 76 FR 22372 - Ball Bearings and Parts Thereof From France, Germany, Italy, Japan, and the United Kingdom...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-21

    ... antidumping duty orders on ball bearings and parts thereof from France (54 FR 20902), Germany (54 FR 20900), Italy (54 FR 20903), Japan (54 FR 20904), and the United Kingdom (54 FR 20910) in the Federal Register... Duty Administrative Reviews and Requests for Revocation in Part, 75 FR 37759 (June 30,...

  4. 75 FR 2108 - Ball Bearings and Parts Thereof from France, Germany, Italy, Japan, and the United Kingdom...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-14

    ... Revocation in Part, 74 FR 30052 (June 24, 2009), as corrected in Initiation of Antidumping and Countervailing Duty Administrative Reviews and Deferral of Administrative Review, 74 FR 37690 (July 29, 2009). The... International Trade Administration Ball Bearings and Parts Thereof from France, Germany, Italy, Japan, and...

  5. 77 FR 16537 - Ball Bearings and Parts Thereof from France, Germany, and Italy: Extension of Time Limit for...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-21

    ... Revocation in Part, 76 FR 37781 (June 28, 2011). See also Ball Bearings and Parts Thereof From Japan and the United Kingdom: Revocation of Antidumping Duty Orders, 76 FR 41761 (July 15, 2011), where we revoked the... of Time Limit for Preliminary Results of Antidumping Duty Administrative Reviews, 77 FR 2511...

  6. 76 FR 2647 - Ball Bearings and Parts Thereof From France, Germany, Italy, Japan, and the United Kingdom...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-14

    ... International Trade Administration Ball Bearings and Parts Thereof From France, Germany, Italy, Japan, and the...: Effective Date: January 14, 2011. FOR FURTHER INFORMATION CONTACT: Yang Jin Chun, AD/CVD Operations, Office... France, Germany, Italy, Japan, and the United Kingdom for the period May 1, 2009, through April 30,...

  7. 75 FR 22384 - Ball Bearings and Parts Thereof From France, Germany, Italy, Japan, and the United Kingdom...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-28

    ... Sales at Less Than Fair Value: Certain Cut-to-Length Carbon Steel Plate From South Africa, 62 FR 61731... the antidumping duty orders on ball bearings and parts thereof from France (54 FR 20902), Germany (54 FR 20900), Italy (54 FR 20903), Japan (54 FR 20904), and the United Kingdom (54 FR 20910) in...

  8. 75 FR 53661 - Ball Bearings and Parts Thereof From France, Germany, Italy, Japan, and the United Kingdom: Final...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-01

    ... Italia S.r.l 1.98 JAPAN Aisin Seiki Company, Ltd 10.97 JTEKT Corporation 10.97 Makino Milling Machine... To Revoke Order In Part, 75 FR 22384 (April 28, 2010), and Ball Bearings and Parts Thereof from... Administrative Reviews in Part, and Intent To Revoke Order In Part, 75 FR 26920 (May 13, 2010)...

  9. Failure Analysis and Recovery of a 50-mm Highly Elastic Intermetallic NiTi Ball Bearing for an ISS Application

    NASA Technical Reports Server (NTRS)

    DellaCorte, Christopher; Howard, S. Adam; Moore, Lewis

    2016-01-01

    Ball bearings used inside the ISS Distillation Assembly centrifuge require superior corrosion and shock resistance to withstand acidic wastewater exposure and heavy spacecraft launch related loads. These requirements challenge conventional steel bearings and provide an ideal pathfinder application for 50-mm bore, deep-groove ball bearings made from the corrosion immune and highly elastic intermetallic material 60NiTi. During early ground testing in 2014 one 60NiTi bearing unexpectedly and catastrophically failed after operating for only 200 hr. A second bearing running on the same shaft was completely unaffected. An investigation into the root cause of the failure determined that an excessively tight press fit of the bearing outer race coupled with NiTi's relatively low elastic modulus were key contributing factors. The proposed failure mode was successfully replicated by experiment. To further corroborate the root cause theory, a successful bearing life test using improved installation practices (selective fitting) was conducted. The results show that NiTi bearings are suitable for space applications provided that care is taken to accommodate their unique material characteristics.

  10. A study on waviness induced vibration of ball bearings based on signal coherence theory

    NASA Astrophysics Data System (ADS)

    Liu, Wentao; Zhang, Yun; Feng, Zhi-Jing; Zhao, Jing-Shan; Wang, Dongfeng

    2014-11-01

    This paper focuses on the effects of waviness on vibration of ball bearings. An experimental analysis method is developed by adopting signal coherence theory of multiple-inputs/single-output (MISO) system. The inputs are waviness excitations of the inner and outer races, and the output is vibration response of the outer ring. Waviness excitation signals are first derived from the manufacturing deviations, and found to be strongly coherent in low frequency range. Virtual input signals are then introduced by the method of orthogonalization. In both cases of vibration acceleration and speed responses, the cumulated virtual input-output coherence function verifies that the first peak region of vibration spectrum is mainly induced by the waviness excitations. In order to distinguish the contributions of the inner and outer races, coherence functions of the virtual inputs with real inputs are calculated, and the results indicate that the outer race waviness contributes more to vibration than the inner race waviness does in the example. Further, a multi-body dynamic model is constructed and employed to frequency response analyses. It is discovered that the waviness induced spectral peak frequency is close to the natural frequency of bearing.

  11. An evaluation of various ball bearing lubricants operating in various environments /A status report/. [fluid and solid lubricants tests

    NASA Technical Reports Server (NTRS)

    Demorest, k. E.; Mcmurtrey, E. L.

    1975-01-01

    Testing of both fluid and solid lubricants in small ball bearings is reported for a period of up to one year in various environments. The testing equipment, procedures and detailed results of five different lubricants, operating in a vacuum at ambient temperature, are described. Specially made motors were shimmed to maintain a 2.27 kg thrust load on both bearings, having a speed of 3600 rpm allowing 216,000 revolutions on each bearing per hour until failure. The commercial perfluoropolyether (PFPE-1) grease, having the best results, was recommended for long term bearing operation under hard vacuum conditions. It had an average life of over 8760 hrs. The ester based grease was recommended for moderate life requirements in vacuum conditions, while the silicone based grease and the fluorosilicone based grease were not recommended for vacuum operation due to extensive metal damage in the bearings.

  12. Wear modes active in angular contact ball bearings operating in liquid oxygen environment of the Space Shuttle turbopumps

    NASA Astrophysics Data System (ADS)

    Chase, Thaddeus J.

    1993-04-01

    Extensive experimental investigation has been carried out on used flight bearings of the high pressure oxidizer turbopumps (HPOTP) of the space shuttle main engine (SSME) in order to determine the dominant wear modes, their extent, and causes. The paper presents the methodology, various surface analysis techniques used, results, and discussion. The mode largely responsible for premature bearing wear has been identified as adhesive/shear peeling of the upper layers of bearing balls and rings. This mode relies upon the mechanisms of scale formation, breakdown, and removal, all of which are greatly enhanced by the heavy oxidation environment of the HPOTP. Major causes of the high wear rates appear to be lubrication and cooling, both inadequate for the imposed conditions of operation. Numerous illustrations and evidence are provided.

  13. Experiments on Ball and Roller Bearings Under Conditions of High Speed and Small Oil Supply

    NASA Technical Reports Server (NTRS)

    Getzlaff, Gunter

    1940-01-01

    This report describes a testing machine on which 35 millimeter bearings (bore) can be run at speeds of the order of 21,000 rpm, while the following factors are recorded: 1) oil circulation through bearing and oil temperature. 2) maximum temperature of outer bearing ring, 3) radial and axial load on bearing, 4) radial, axial, and angular clearance of bearing, 5) power consumption of bearing. The experiments show that the lubrication was most reliable and oil consumption lowest when the oil was introduced through a hole in the outer or inner ring of the bearing.

  14. Superelastic Ball Bearings: Materials and Design to Avoid Mounting and Dismounting Brinell Damage in an Inaccessible Press-Fit Application-. I ; Design Approach

    NASA Technical Reports Server (NTRS)

    Dellacorte, Christopher; Howard, S. Adam

    2015-01-01

    Ball bearings require proper fit and installation into machinery structures (onto shafts and into bearing housings) to ensure optimal performance. For some applications, both the inner and outer race must be mounted with an interference fit and care must be taken during assembly and disassembly to avoid placing heavy static loads between the balls and races otherwise Brinell dent type damage can occur. In this paper, a highly dent resistant superelastic alloy, 60NiTi, is considered for rolling element bearing applications that encounter excessive static axial loading during assembly or disassembly. A small (R8) ball bearing is designed for an application in which access to the bearing races to apply disassembly tools is precluded. First Principles analyses show that by careful selection of materials, raceway curvature and land geometry, a bearing can be designed that allows blind assembly and disassembly without incurring raceway damage due to ball denting. Though such blind assembly applications are uncommon, the availability of bearings with unusually high static load capability may enable more such applications with additional benefits, especially for miniature bearings.

  15. Suomi-NPP Mission On-Orbit Experience with Toroid Ball Bearing Retainers Under Unidirectional and Reversing Motion

    NASA Technical Reports Server (NTRS)

    Bruegman, Otto; Thakore, Kamal; Loewenthal, Stu; Cymerman, John

    2016-01-01

    The Advanced Technology Microwave Sounder (ATMS) instrument scan system on the Suomi National Polar-orbiting Partnership (SNPP) spacecraft has experienced several randomly occurring increased torque 'events' since its on-orbit activation in November 2011. Based on a review of on-orbit telemetry data and data gathered from scan mechanism bearing life testing on the ground, the conclusion was drawn that some degradation of Teflon toroid ball retainers was occurring in the instrument Scan Drive Mechanism. A life extension program was developed and executed on-orbit with very good results to date. The life extension program consisted of reversing the mechanism for a limited number of consecutive scans every day.

  16. Determination of Lubricants on Ball Bearings by FT-IR using an Integrating Sphere

    NASA Technical Reports Server (NTRS)

    Street, K. W.; Pepper, S. V.; Wright, A.

    2003-01-01

    The lifetime determination of space lubricants is done at our facility by accelerated testing. Several micrograms of lubricant are deposited on the surface of a ball by syringing tens of micro liters of dilute lubricant solution. The solvent evaporates and the mass of lubricant is determined by twenty weighings near the balance reliability limit. This process is timely but does not produce a good correlation between the mass of lubricant and the volume of solution applied, as would be expected. The amount of lubricant deposited on a ball can be determined directly by Fourier Transform - Infrared Spectroscopy using an integrating sphere. In this paper, we discuss reasons for choosing this methodology, optimization of quantification conditions and potential applications for the technique. The volume of lubricant solution applied to the ball gives better correlation to the IR intensity than does the weight.

  17. How to apply life adjustment factors for ball and roller bearings

    NASA Technical Reports Server (NTRS)

    Crecelius, W. J.; Harris, T. A.; Moyer, C. A.; Parker, R. J.; Sherlock, J. J.; Zaretsky, E. V.

    1972-01-01

    Practical problems applicable to the selection, design, and lubrication of rolling-element bearings are presented and discussed. Design and selection criteria are based upon materials and processing factors such as melting practice, metalworking, and heat treatment. Environmental factors are considered such as bearing misalignment and speed. Selection of a lubricant is based upon elastohydrodynamic lubrication principles in addition to lubricant type and chemistry.

  18. Experimental performance of 75-millimeter-bore arched outer-race ball bearings to 2.1 million DN. [thrust loads

    NASA Technical Reports Server (NTRS)

    Coe, H. H.

    1976-01-01

    An experimental investigation was performed to determine the operating characteristics of arched outer-race bearings and to compare the data with those for a similar, but conventional, deep-groove ball bearing. The bearings were tested over a range of shaft speeds up to 28,000 rpm at a thrust load of 2200 newtons (500 lb). One bearing was operated at 26,000 rpm with a range of thrust loads. The amounts of arching were 0.13, 0.25, and 0.51 millimeter (0.005, 0.010, and 0.020 in.). All bearings operated satisfactorily; the arched bearing outer-race temperatures and torques were consistently higher than those for the conventional bearing.

  19. Nonlinear dynamic analysis of rolling element bearings due to cage run-out and number of balls

    NASA Astrophysics Data System (ADS)

    Harsha, S. P.

    2006-01-01

    This paper presents an analytical model to investigate the nonlinear dynamic behavior due to cage run-out and number of balls in a rotating system supported by rolling element bearings. Due to run-out of the cage, the rolling elements no longer stay equally spaced. The mathematical model takes into account the sources of nonlinearity such as the Hertzian contact force and cage run-out resulting transition from no contact to contact state between rolling elements and races. The contact between the rolling elements and races is treated as nonlinear springs. The nonlinear stiffness is obtained by application of Hertzian contact deformation theory. The implicit-type numerical integration technique Newmark- β with Newton-Raphson method is used to solve the nonlinear differential equations iteratively. The results are presented in the form of fast Fourier transformations (FFT) and phase trajectories. It is implied from the obtained FFT that due to the non-uniform spacing the ball passage frequency is modulated with the cage frequency.

  20. The Effect of Indenter Ball Radius on the Static Load Capacity of the Superelastic 60NiTi for Rolling Element Bearings

    NASA Technical Reports Server (NTRS)

    Dellacorte, Christopher; Moore, Lewis E.; Clifton, Joshua S.

    2014-01-01

    Static load capacity is a critical design parameter for rolling element bearings used in space mechanisms because of the potential for Brinell (surface dent) damage due to shock and vibration loading events during rocket launch. Brinell damage to bearing raceways can lead to torque variations (noise) and reduced bearing life. The growing use of ceramic rolling elements with high stiffness in hybrid bearings exacerbates the situation. A new family of hard yet resilient materials based upon nickel-titanium is emerging to address such bearing challenges. 60NiTi is a superelastic material that simultaneously exhibits high hardness and a relatively low elastic modulus (100GPa) and has been shown to endure higher indentation loads than conventional and high performance steel. Indentation load capacity has been reported for relatively large (12.7mm diameter) ceramic (Si3N4) indenter balls pressed against flat plates of 60NiTi. In order to develop damage load threshold criteria applicable to a wide range of bearing designs and sizes, the effects of indenter ball radius and the accuracy of interpolation of the Hertz contact stress relations for 60NiTi must be ascertained. In this paper, results of indentation tests involving ceramic balls ranging from 6.4 to 12.7mm in diameter and highly polished 60NiTi flat plates are presented. When the resulting dent depth data for all the indenter ball sizes are normalized using the Hertz equations, the data (dent depth vs. stress) are comparable. Thus when designing bearings made from 60NiTi, the Hertz stress relations can be applied with relative confidence over a range of rolling element sizes and internal geometries.

  1. The Effect of Indenter Ball Radius on the Static Load Capacity of the Superelastic 60NiTi for Rolling Element Bearings

    NASA Technical Reports Server (NTRS)

    Dellacorte, Christopher; Moore, Lewis E.

    2014-01-01

    Static load capacity is a critical design parameter for rolling element bearings used in space mechanisms because of the potential for Brinell (surface dent) damage due to shock and vibration loading events during rocket launch. Brinell damage to bearing raceways can lead to torque variations (noise) and reduced bearing life. The growing use of ceramic rolling elements with high stiffness in hybrid bearings exacerbates the situation. A new family of hard yet resilient materials based upon nickel-titanium is emerging to address such bearing challenges. 60NiTi is a superelastic material that simultaneously exhibits high hardness and a relatively low elastic modulus (approx. 100 GPa) and has been shown to endure higher indentation loads than conventional and high performance steel. Indentation load capacity has been reported for relatively large (12.7 mm diameter) ceramic (Si3N4) indenter balls pressed against flat plates of 60NiTi. In order to develop damage load threshold criteria applicable to a wide range of bearing designs and sizes, the effects of indenter ball radius and the accuracy of interpolation of the Hertz contact stress relations for 60NiTi must be ascertained. In this paper, results of indentation tests involving ceramic balls ranging from 6.4 to 12.7 mm in diameter and highly polished 60NiTi flat plates are presented. When the resulting dent depth data for all the indenter ball sizes are normalized using the Hertz equations, the data (dent depth versus stress) are comparable. Thus when designing bearings made from 60NiTi, the Hertz stress relations can be applied with relative confidence over a range of rolling element sizes and internal geometries.

  2. The Effect of Indenter Ball Radius on the Static Load Capacity of the Superelastic 60NiTi for Rolling Element Bearings

    NASA Technical Reports Server (NTRS)

    DellaCorte, Christopher; Moore, Lewis E., III; Clifton, Joshua S.

    2014-01-01

    Static load capacity is a critical design parameter for rolling element bearings used in space mechanisms because of the potential for Brinell (surface dent) damage due to shock and vibration loading events during rocket launch. Brinell damage to bearing raceways can lead to torque variations (noise) and reduced bearing life. The growing use of ceramic rolling elements with high stiffness in hybrid bearings exacerbates the situation. A new family of hard yet resilient materials based upon nickel-titanium is emerging to address such bearing challenges. 60NiTi is a superelastic material that simultaneously exhibits high hardness and a relatively low elastic modulus (approx. 100 GigaPascals) and has been shown to endure higher indentation loads than conventional and high performance steel. Indentation load capacity has been reported for relatively large (12.7 millimeters diameter) ceramic (Si3N4) indenter balls pressed against flat plates of 60NiTi. In order to develop damage load threshold criteria applicable to a wide range of bearing designs and sizes, the effects of indenter ball radius and the accuracy of interpolation of the Hertz contact stress relations for 60NiTi must be ascertained. In this paper, results of indentation tests involving ceramic balls ranging from 6.4 to 12.7 mm in diameter and highly polished 60NiTi flat plates are presented. When the resulting dent depth data for all the indenter ball sizes are normalized using the Hertz equations, the data (dent depth versus stress) are comparable. Thus when designing bearings made from 60NiTi, the Hertz stress relations can be applied with relative confidence over a range of rolling element sizes and internal geometries.

  3. 75 FR 3444 - Ball Bearings and Parts Thereof From Germany: Initiation of Antidumping Duty Changed...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-21

    ... Republic of Germany, 54 FR 20900 (May 15, 1989). The orders on cylindrical roller bearings and spherical... Kingdom, 65 FR 42667 (July 11, 2000). Miniaturkugellager GmbH (MKL) was a respondent in a new-shipper... Parts Thereof, From Germany; Final Results of New Shipper Antidumping Duty Administrative Review, 61...

  4. Superelastic Ball Bearings: Materials and Design to Avoid Mounting and Dismounting Brinell Damage in an Inaccessible Press-fit Application-. II; Detailed Analysis

    NASA Technical Reports Server (NTRS)

    Howard, S. Adam; Dellacorte, Christopher

    2015-01-01

    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.

  5. Research report: User's manual for computer program AT81y003 SHABERTH. Steady state and transient thermal analysis of a shaft bearing system including ball, cylindrical and tapered roller bearings

    NASA Technical Reports Server (NTRS)

    Hadden, G. B.; Kleckner, R. J.; Ragen, M. A.; Sheynin, L.

    1981-01-01

    The SHABERTH program is capable of simulating the thermomechanical performance of a load support system consisting of a flexible shaft supported by up to five rolling element bearings. Any combination of ball, cylindrical, and tapered roller bearings can be used to support the shaft. The user can select models in calculating lubricant film thickness and traction forces. The formulation of the cage pocket/rolling element interaction model was revised to improve solution numerical convergence characteristics.

  6. An evaluation of grease type ball bearing lubricants operating in various environments

    NASA Technical Reports Server (NTRS)

    Mcmurtrey, E. L.

    1981-01-01

    Because many future spacecraft or space stations will require mechanisms to operate for long periods of time in environments which are adverse to most bearing lubricants, a series of tests is continuing to evaluate 38 grease type lubricants in R-4 size bearings in five different environments for a 1 year period. Four repetitions of each test are made to provide statistical samples. These tests were used to select four lubricants for 5 year tests in selected environments with five repetitions of each test for statistical samples. At the present time, 100 test sets are completed and 22 test sets are underway. Three 5 year tests were started in (1) continuous operation and (2) start-stop operation, with both in vacuum at ambient temperatures, and (3) continuous operation at 93.3 C. In the 1 year tests the best results to date in all environments were obtained with a high viscosity index perfluoroalkylpolyether (PFPE) grease.

  7. An evaluation of grease type ball bearing lubricants operating in various environments

    NASA Technical Reports Server (NTRS)

    Mcmurtrey, E. L.

    1978-01-01

    Because many future spacecraft or space stations will require mechanisms to operate for long periods of time in environments which are adverse to most bearing lubricants, a series of tests is continuing to evaluate 29 grease type lubricants in R-4 size bearings in five different environments for a 1 year period. Four repetitions of each test are made to provide statistical samples. These tests have also been used to select four lubricants for 5 year tests in selected environments with five repetitions of each test for statistical samples. At the present time, 65 test sets have been completed and 23 test sets are underway. Two (5 year) tests have already been started in (1) continuous operation and (2) start-stop operation, with both in vacuum at ambient temperatures. To date, in the 1 year tests, the best results in all environments have been obtained with a high viscosity index perfluoroalkylpolyether grease.

  8. An evaluation of grease type ball bearing lubricants operating in various environments

    NASA Technical Reports Server (NTRS)

    Mcmurtrey, E. L.

    1984-01-01

    Because many future spacecraft or space stations will require mechanisms to operate for long periods of time in environments which are adverse to most bearing lubricants, a series of tests has been completed to evaluate 38 grease type lubricants in R-4 size bearings in five different environments for a 1 year period. Four repetitions of each test were made to provide statistical samples. These tests were also used to select four lubricants for 5 year tests in selected environments with five repetitions of each test for statistical samples. In this completed program, 172 test sets have been completed. The three 5 year tests in: (1) continuous operation and (2) start stop operation, with both in vacuum at ambient temperatures, and (3) continuous vacuum operation at 93.3 C have been completed. In both the 1 year and 5 year tests, the best results in all environments have been obtained with a high viscosity index perfluoroalkylpolyether (PFPE) grease.

  9. An evaluation of grease type ball bearing lubricants operating in various environments

    NASA Technical Reports Server (NTRS)

    Mcmurtrey, E. L.

    1979-01-01

    Grease type lubricants in bearings were evaluated in five different adverse environments for a one year period. Four repetitions of each test were made to provide statistical samples. These tests were then used to select four lubricants for five year tests in selected environments with five repetitions of each test for statistical samples. Three five year tests were started in (1) continuous operation; (2) start-stop operation, with both in vacuum at ambient temperatures; and (3) continuous operation at 93.3 C. To date, in the one year tests, the best results in all environments were obtained with a high viscosity index perfluoroalkylpolyether grease.

  10. Comparison Between Oil-mist and Oil-jet Lubrication of High-speed, Small-bore, Angular-contact Ball Bearings

    NASA Technical Reports Server (NTRS)

    Pinel, Stanley I.; Signer, Hans R.; Zaretsky, Erwin V.

    2001-01-01

    Parametric tests were conducted with an optimized 35-mm-bore-angular-contact ball bearing on a high-speed, high-temperature bearing tester. Results from both air-oil mist lubrication and oil-jet lubrication systems used to lubricate the bearing were compared to speeds of 2.5 x 10(exp 6) DN. The maximum obtainable speed with air-oil mist lubrication is 2.5 x 10(exp 6) DN. Lower bearing temperatures and higher power losses are obtained with oil-jet lubrication than with air-oil mist lubrication. Bearing power loss is a direct function of oil flow to the bearing and independent of oil delivery system. For a given oil-flow rate, bearing temperature and power loss increase with increases in speed. Bearing life is an inverse function of temperature, the difference in temperature between the individual bearing ring components, and the resultant elastohydrodynamic (EHD) film thicknesses. Bearing life is independent of the oil delivery system except as it affects temperature. Cage slip increased with increases in speed. Cage slip as high as 7 percent was measured and was generally higher with air-oil mist lubrication than with oil-jet lubrication.

  11. Ball bearings comprising nickel-titanium and methods of manufacture thereof

    NASA Technical Reports Server (NTRS)

    DellaCorte, Christopher (Inventor); Glennon, Glenn N. (Inventor)

    2012-01-01

    Disclosed herein is a friction reducing nickel-titanium composition. The nickel-titanium composition includes a first phase that comprises nickel and titanium in an atomic ratio of about 0.45:0.55 to about 0.55:0.45; a second phase that comprises nickel and titanium in an atomic ratio of about 0.70:0.30 to about 0.80:0.20; and a third phase that comprises nickel and titanium in an atomic ratio of about 0.52:0.48 to about 0.62:0.38. A bearing for reducing friction comprising a nickel-titanium composition comprising a first phase that comprises nickel and titanium in an atomic ratio of about 0.45:0.55 to about 0.55:0.45; a second phase that comprises nickel and titanium in an atomic ratio of about 0.70:0.30 to about 0.80:0.20; and a third phase that comprises nickel and titanium in an atomic ratio of about 0.52:0.48 to about 0.62:0.38; where the bearing is free from voids and pinholes.

  12. An evaluation of grease-type ball bearing lubricants operation in various environments

    NASA Technical Reports Server (NTRS)

    Mcmurtrey, E. L.

    1983-01-01

    Because many future spacecraft or space stations will require mechanisms to operate for long periods of time in environments which are adverse to most bearing lubricants, a series of tests is continuing to evaluate 38 grease type lubricants in R-4 size bearings in five different environments for a 1 year period. Four repetitions of each test are made to provide statistical samples. These tests have also been used to select four lubricants for 5 year tests in selected environments with five repetitions of each test for statistical samples. At the present time, 142 test sets have been completed and 30 test sets are underway. The three 5 year tests in (1) continuous operation and (2) start stop operation, with both in vacuum at ambient temperatures, and (3) continuous vacuum operation at 93.3 C are now completed. To date, in both the 1 year and 5 year tests, the best results in all environments have been obtained with a high viscosity index perfluoroalkylpolyether (PFPE) grease.

  13. Preliminary Investigation of Molybdenum Disulfide-air-mist Lubrication for Roller Bearings Operating to DN Values of 1 x 10(exp 6) and Ball Bearings Operating to Temperatures of 1000 F

    NASA Technical Reports Server (NTRS)

    Macks, E F; Nemeth, Z N; Anderson, W J

    1951-01-01

    The effectiveness of molybdenum disulfide MoS2 as a bearing lubricant was determined at high temperature and at high speeds. A 1-inch-bore ball bearing operated at temperatures to 1000 F, a speed of 1725 rpm, and a thrust load of 20 pounds when lubricated only with MoS2-air mist. A 75-millimeter-bore cageless roller bearing, provided with a MoS2-syrup coating before operation, operated at DN values to 1 x 10(exp 6) with a load of 368 pounds.

  14. Petrography and microanalysis of Pennsylvanian coal-ball concretions (Herrin Coal, Illinois Basin, USA): Bearing on fossil plant preservation and coal-ball origins

    NASA Astrophysics Data System (ADS)

    Siewers, Fredrick D.; Phillips, Tom L.

    2015-11-01

    Petrographic analyses of 25 coal balls from well-studied paleobotanical profiles in the Middle Pennsylvanian Herrin Coal (Westphalian D, Illinois Basin) and five select coal balls from university collections, indicate that Herrin Coal-ball peats were permineralized by fibrous and non-fibrous carbonates. Fibrous carbonates occur in fan-like to spherulitic arrays in many intracellular (within tissue) pores, and are best developed in relatively open extracellular (between plant) pore spaces. Acid etched fibrous carbonates appear white under reflected light and possess a microcrystalline texture attributable to abundant microdolomite. Scanning electron microscopy, X-ray diffraction, and electron microprobe analysis demonstrate that individual fibers have a distinct trigonal prism morphology and are notable for their magnesium content (≈ 9-15 mol% MgCO3). Non-fibrous carbonates fill intercrystalline spaces among fibers and pores within the peat as primary precipitates and neomorphic replacements. In the immediate vicinity of plant cell walls, non-fibrous carbonates cut across fibrous carbonates as a secondary, neomorphic phase attributed to coalification of plant cell walls. Dolomite occurs as diagenetic microdolomite associated with the fibrous carbonate phase, as sparite replacements, and as void-filling cement. Maximum dolomite (50-59 wt.%) is in the top-of-seam coal-ball zone at the Sahara Mine, which is overlain by the marine Anna Shale. Coal-ball formation in the Herrin Coal began with the precipitation of fibrous high magnesium calcite. The trigonal prism morphology of the carbonate fibers suggests rapid precipitation from super-saturated, meteoric pore waters. Carbonate precipitation from marine waters is discounted on the basis of stratigraphic, paleobotanical, and stable isotopic evidence. Most non-fibrous carbonate is attributable to later diagenetic events, including void-fill replacements, recrystallization, and post-depositional fracture fills. Evidence

  15. Ball's motion, sliding friction, and internal load distribution in a high-speed ball bearing subjected to a combined radial, thrust, and moment load, applied to the inner ring's center of mass: Mathematical model

    NASA Astrophysics Data System (ADS)

    César Ricci, Mário

    2015-10-01

    A set of non-linear algebraic equations, which must to be solved using a numerical procedure, for ball's motion, sliding friction and internal loading distribution computation in a high-speed, single-row, angular-contact ball bearing, subjected to a known combined radial, thrust and moment load, which must be applied to the inner ring's centre of mass, is introduced. For each step of the procedure it is required the iterative solution of 9Z + 3 simultaneous non-linear equations—where Z is the number of the balls—to yield exact solution for contact angles, ball attitude angles, rolling radii, normal contact deformations and axial, radial, and angular deflections of the inner ring with respect the outer ring. While the focus of this work is obtaining the steady state forces and moments equilibrium conditions on the balls, under the selected loading, the numerical aspects of the procedure are treated in a companion paper. The numerical results derived from the described procedure shall be published later.

  16. Performance of 40-millimeter-bore ball bearings with lead- and lead-alloy-plated retainers in liquid hydrogen at 1.2 million DN

    NASA Technical Reports Server (NTRS)

    Brewe, D. E.; Wisander, D. W.; Scribbe, H. W.

    1972-01-01

    Forty-millimeter-bore ball bearings with lead- and lead-alloy-coated retainers were operated in liquid hydrogen at 30,000 rpm under a thrust load of 1780 N (400 lb.) Four different substrate materials were used for the retainer. Longer bearing run times were achieved with a lead-tin-copper alloy coating plated onto a leaded-bronze material (22.5 hr) and an aluminum-bronze alloy (19.3 hr). One bearing with a pure lead coating achieved the desired objective of 10 hr. This bearing had an aluminum - bronze substrate retainer and ran successfully for 12.4 hr. Additions of antimony to the lead provided an alloy coating with better wear resistance than pure lead; however, this coating was abrasive to the outer-race lands.

  17. The bounce of a ball

    NASA Astrophysics Data System (ADS)

    Cross, Rod

    1999-03-01

    In this paper, the dynamics of a bouncing ball is described for several common ball types having different bounce characteristics. Results are presented for a tennis ball, a baseball, a golf ball, a superball, a steel ball bearing, a plasticene ball, and a silly putty ball. The plasticene ball was studied as an extreme case of a ball with a low coefficient of restitution (in fact zero, since the collision is totally inelastic) and the silly putty ball was studied because it has unusual elastic properties. The first three balls were studied because of their significance in the physics of sports. For each ball, a dynamic hysteresis curve is presented to show how energy is lost during and after the collision. The measurement technique is quite simple, it is suited for undergraduate laboratory experiments, and it may provide a useful method to test and approve balls for major sporting events.

  18. Finite-difference solutions of the alternate turbopump development high-pressure oxidizer turbopump pump-end ball-bearing cavity flows

    NASA Astrophysics Data System (ADS)

    Benjamin, Theodore G.; Garcia, Roberto; McConnaughey, Paul K.; Wang, Ten-See; Vu, Bruce T.; Dakhoul, Youssef

    1993-07-01

    These analyses were undertaken to aid in the understanding of flow phenomena in the Alternate Turbopump Development (ATD) High-pressure Oxidizer Turbopump (HPOTP) Pump-end ball bearing (PEBB) cavities and their roles in turbopump vibration initiation and bearing distress. This effort was being performed to provide timely support to the program in a decision as to whether or not the program should be continued. In the first case, it was determined that a change in bearing through flow had no significant effect on axial preload. This was a follow-on to a previous study which had resulted in a redesign of the bearing exit cavity which virtually eliminated bearing axial loading. In the second case, a three-dimensional analysis of the inner-race-guided cage configuration was performed so as to determine the pressure distribution on the outer race when the shaft is 0.0002 inches off-center. The results indicate that there is virtually no circumferential pressure difference caused by the offset to contribute to bearing tilt. In the third case, axisymmetric analyses were performed on an outer-race guided cage configuration to determine the magnitude of tangential flow entering the bearing. The removed-shoulder case was analyzed as was the static diverter case. A third analysis where the preload spring was shielded by a sheet of metal for the baseline case was also performed. It was determined that the swirl entering the bearing was acceptable and the project decided to use the outer-race-guided cage configuration. In the fourth case, more bearing configurations were analyzed. These analyses included thermal modeling so as to determine the added benefit of injecting colder fluid directly onto the bearing inner-race contact area. The results of these analyses contributed to a programmatic decision to include coolant injection in the design.

  19. ToF-SIMS analysis of anti-fretting films generated on the surface of ball bearings containing dithiocarbamate and dithiophosphate grease additives

    NASA Astrophysics Data System (ADS)

    Duque, Ricardo G.; Wang, Zhiyu; Duell, Dave; Fowler, David E.

    2004-06-01

    During transport of hard drives from the factory to the end customer, vibrations can induce small repetitive displacements of the ball bearings giving rise to fretting corrosion at the metal surfaces. On the other hand, it has been found that some particular types of grease additives can form thin layers on steel surfaces and thus protect against fretting corrosion. ToF-SIMS has been used to study the chemical nature of layers formed on bearing surfaces containing greases with dithiocarbamates, dithiophosphates, and metal sulfonate additives. In cases where fretting was prevented, the presence of MoS 2-, FeS - and ion fragments containing Mo-Fe-S - were observed, whereas none of these ions were detected on the surfaces of fretted bearings. Finally, it is inferred that the action of metal sulfonates may have an antagonist effect on the anti-fretting activity of the dithiocarbamate and dithiophosphate compounds studied.

  20. Model Specification for Rework of Aircraft Engine, Power Transmission, and Accessory/Auxiliary Ball and Roller Bearings

    NASA Technical Reports Server (NTRS)

    Zaretsky, Erwin V.; Branzai, Emanuel V.

    2007-01-01

    This document provides a model specification for the rework and/or repair of bearings used in aircraft engines, helicopter main power train transmissions, and auxiliary bearings determined to be critical by virtue of performance, function, or availability. The rolling-element bearings to be processed under the provisions of this model specification may be used bearings removed after service, unused bearings returned from the field, or certain rejected bearings returned for reinspection and salvage. In commercial and military aircraft application, it has been a practice that rolling-element bearings removed at maintenance or overhaul be reworked and returned to service. Depending on the extent of rework and based upon theoretical analysis, representative life factors (LF) for bearings subject to rework ranged from 0.87 to 0.99 the lives of new bearings. Based on bearing endurance data, 92 percent of the bearing sets that would be subject to rework would result in L(sub 10) lives equaling and/or exceeding that predicted for new bearings. The remaining 8 percent of the bearings have 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 percent of that of new bearings depending on the cost, size, and complexity of the bearing

  1. Analysis of stresses at the bore of a drilled ball operating in a high-speed bearing. [with stiffening web

    NASA Technical Reports Server (NTRS)

    Coe, H. H.; Lynch, J. E.

    1973-01-01

    Three-dimensional stress distributions were calculated for both a regular drilled ball with a stiffening web. The balls were 20.6 mm (0.8125 in.) in diameter and had a 12.6 mm (0.496 in.) diameter concentric hole. The stiffening web was 1.5 mm (0.06 in.) thick. The calculations showed that a large reversing tangential stress at the hole bore was reduced by one-half by the addition of the web.

  2. Use of Homogeneously-Sized Carbon Steel Ball Bearings to Study Microbially-Influenced Corrosion in Oil Field Samples.

    PubMed

    Voordouw, Gerrit; Menon, Priyesh; Pinnock, Tijan; Sharma, Mohita; Shen, Yin; Venturelli, Amanda; Voordouw, Johanna; Sexton, Aoife

    2016-01-01

    Microbially-influenced corrosion (MIC) contributes to the general corrosion rate (CR), which is typically measured with carbon steel coupons. Here we explore the use of carbon steel ball bearings, referred to as beads (55.0 ± 0.3 mg; Ø = 0.238 cm), for determining CRs. CRs for samples from an oil field in Oceania incubated with beads were determined by the weight loss method, using acid treatment to remove corrosion products. The release of ferrous and ferric iron was also measured and CRs based on weight loss and iron determination were in good agreement. Average CRs were 0.022 mm/yr for eight produced waters with high numbers (10(5)/ml) of acid-producing bacteria (APB), but no sulfate-reducing bacteria (SRB). Average CRs were 0.009 mm/yr for five central processing facility (CPF) waters, which had no APB or SRB due to weekly biocide treatment and 0.036 mm/yr for 2 CPF tank bottom sludges, which had high numbers of APB (10(6)/ml) and SRB (10(8)/ml). Hence, corrosion monitoring with carbon steel beads indicated that biocide treatment of CPF waters decreased the CR, except where biocide did not penetrate. The CR for incubations with 20 ml of a produced water decreased from 0.061 to 0.007 mm/yr when increasing the number of beads from 1 to 40. CRs determined with beads were higher than those with coupons, possibly also due to a higher weight of iron per unit volume used in incubations with coupons. Use of 1 ml syringe columns, containing carbon steel beads, and injected with 10 ml/day of SRB-containing medium for 256 days gave a CR of 0.11 mm/yr under flow conditions. The standard deviation of the distribution of residual bead weights, a measure for the unevenness of the corrosion, increased with increasing CR. The most heavily corroded beads showed significant pitting. Hence the use of uniformly sized carbon steel beads offers new opportunities for screening and monitoring of corrosion including determination of the distribution of corrosion rates, which allows

  3. Use of Homogeneously-Sized Carbon Steel Ball Bearings to Study Microbially-Influenced Corrosion in Oil Field Samples

    PubMed Central

    Voordouw, Gerrit; Menon, Priyesh; Pinnock, Tijan; Sharma, Mohita; Shen, Yin; Venturelli, Amanda; Voordouw, Johanna; Sexton, Aoife

    2016-01-01

    Microbially-influenced corrosion (MIC) contributes to the general corrosion rate (CR), which is typically measured with carbon steel coupons. Here we explore the use of carbon steel ball bearings, referred to as beads (55.0 ± 0.3 mg; Ø = 0.238 cm), for determining CRs. CRs for samples from an oil field in Oceania incubated with beads were determined by the weight loss method, using acid treatment to remove corrosion products. The release of ferrous and ferric iron was also measured and CRs based on weight loss and iron determination were in good agreement. Average CRs were 0.022 mm/yr for eight produced waters with high numbers (105/ml) of acid-producing bacteria (APB), but no sulfate-reducing bacteria (SRB). Average CRs were 0.009 mm/yr for five central processing facility (CPF) waters, which had no APB or SRB due to weekly biocide treatment and 0.036 mm/yr for 2 CPF tank bottom sludges, which had high numbers of APB (106/ml) and SRB (108/ml). Hence, corrosion monitoring with carbon steel beads indicated that biocide treatment of CPF waters decreased the CR, except where biocide did not penetrate. The CR for incubations with 20 ml of a produced water decreased from 0.061 to 0.007 mm/yr when increasing the number of beads from 1 to 40. CRs determined with beads were higher than those with coupons, possibly also due to a higher weight of iron per unit volume used in incubations with coupons. Use of 1 ml syringe columns, containing carbon steel beads, and injected with 10 ml/day of SRB-containing medium for 256 days gave a CR of 0.11 mm/yr under flow conditions. The standard deviation of the distribution of residual bead weights, a measure for the unevenness of the corrosion, increased with increasing CR. The most heavily corroded beads showed significant pitting. Hence the use of uniformly sized carbon steel beads offers new opportunities for screening and monitoring of corrosion including determination of the distribution of corrosion rates, which allows

  4. 76 FR 41761 - Ball Bearings and Parts Thereof From Japan and the United Kingdom: Revocation of Antidumping Duty...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-15

    ... Plain Bearings, and Parts Thereof From Japan, 54 FR 20904 (May 15, 1989), and Antidumping Duty Orders... Cylindrical Roller Bearings and Parts Thereof From the United Kingdom, 54 FR 20910 (May 15, 1989). Pursuant to... Initiation of Five-year (``Sunset'') Reviews, 70 FR 31423 (June 1, 2005); Certain Bearings From China,...

  5. A study of boiling heat transfer as applied to the cooling of ball bearings in the high pressure oxygen turbopump of the space shuttle main engine

    NASA Technical Reports Server (NTRS)

    Schreiber, Will

    1986-01-01

    Two sets of ball bearings support the main shaft within the High Pressure Oxygen Turbopump (HPOTP) in the Space Shuttle Main Engine (SSME). In operation, these bearings are cooled and lubricated with high pressure liquid oxygen (LOX) flowing axially through the bearing assembly. Currently, modifications in the assembly design are being contemplated in order to enhance the lifetime of the bearings and to allow the HPOTP to operate under larger loads. An understanding of the fluid dynamics and heat transfer characteristics of the flowing LOX is necessary for the implementation of these design changes. The proposed computational model of the LOX fluid dynamics, in addition to dealing with a turbulent flow in a complex geometry, must address the complication associated with boiling and two-phase flow. The feasibility of and possible methods for modeling boiling heat transfer are considered. The theory of boiling as pertains to this particular problem is reviewed. Recommendations are given for experiments which would be necessary to establish validity for correlations needed to model boiling.

  6. 78 FR 76104 - Ball Bearings and Parts Thereof From Japan and the United Kingdom: Notice of Reinstatement of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-12-16

    ... Roller Bearings, and Spherical Plain Bearings, and Parts Thereof From Japan, 54 FR 20904 (May 15, 1989..., France, Germany, Italy, Japan, Singapore, and the United Kingdom, 70 FR 31531 (June 1, 2005); see also 19... Japan; Five-Year Sunset Review of Antidumping Duty Order: Amended Final Results, 71 FR 30378 (May...

  7. Effect of Ceramic Ball and Hybrid Stainless Steel Bearing/Wheel Combinations on the Lifetime of a Precision Translation Stage for the SIM Flight Project

    NASA Technical Reports Server (NTRS)

    Lo, C. John; Klein, Kerry; Jones, William R., Jr.; Jansen, Mark J.; Wemhoner, Jens

    2009-01-01

    A study of hybrid material couples using the Spiral Orbit Tribometer (SOT) was initiated to investigate both lubricated (Pennzane X2000 and Brayco 815Z) and unlubricated Si3N4, 440C SS, Rex 20, Cronidur X30 and X40 plates with Cerbec SN-101-C (Si3N4) and 440C balls. The hybrid wheel/bearing assembly will be used on the Linear Optical Delay Line (LODL) stage as an element of the NASA Space Interferometry Mission (SIM). SIM is an orbiting interferometer linking a pair of telescopes within the spacecraft and, by using an interferometry technique and several precision optical stages, is able to measure the motions of known stars much better than current ground or space based systems. This measurement will provide the data to "infer" the existence of any plants, undetectable by other methods, orbiting these known stars.

  8. 75 FR 34688 - Ball Bearings and Parts Thereof from France: Final Results of Changed-Circumstances Review

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-18

    ... Bearings and Parts Thereof From France: Initiation of Antidumping Duty Changed-Circumstances Review, 74 FR...: Preliminary Results of Changed- Circumstances Review, 74 FR 60242 (November 20, 2009). We received case briefs... Reviews and Rescission of Review in Part, 72 FR 58053, 58054 (October 12, 2007). Notification This...

  9. Bearing puller facilitates removal and replacement of bearing assemblies

    NASA Technical Reports Server (NTRS)

    Schaus, R. B.

    1966-01-01

    Bearing puller removes ball bearing assemblies, which carry the rotor, from turbine type flowmeters. It matches the bearing configuration to facilitate removal of the bearing assemblies from the support members.

  10. Ball clay

    USGS Publications Warehouse

    Virta, R.L.

    2001-01-01

    Part of the 2000 annual review of the industrial minerals sector. A general overview of the ball clay industry is provided. In 2000, sales of ball clay reached record levels, with sanitary ware and tile applications accounting for the largest sales. Ball clay production, consumption, prices, foreign trade, and industry news are summarized. The outlook for the ball clay industry is also outlined.

  11. Effect of two inner-ring oil-flow distribution schemes on the operating characteristics of a 35 millimeter bore ball bearing to 2.5 million DN

    NASA Technical Reports Server (NTRS)

    Schuller, F. T.; Pinel, S. I.; Signer, H. R.

    1985-01-01

    Parametric tests were conducted with a 35-mm-bore, split-inner-ring ball bearing with a double-inner-land-guided cage. Provisions were made for through-the-inner-ring lubrication. Test condictions were either a thrust load of 667 N (150 lb) or a combined load of 667 N (150 lb) thrust and 222 N (50 lb) radial, shaft speeds from 32000 to 72000 rpm, and an oil-inlet temperature of 394 K (250 deg F). Outer ring cooling was used in some tests. Tests were run with either 50 or 75 percent of the total oil flow distributed to the inner-ring raceway. Successful operation was experienced with both 50% and 75% flow patterns to 2.5 million DN. Cooling the outer ring had little effect on inner-ring temperature; however, the outer-ring temperature decreased as much as 7% at 2.5 million DN. Maximum recorded power loss was 3.1 kW (4.2 hp), and maximum cage slip was 8.7 percent. Both occurred at a shaft speed of 72000 rpm, a lubricant flow rate of 1900 cu/min (0.50 gal/min), a combined load, and no outer-ring cooling.

  12. Passive Ball Capture Joint

    NASA Technical Reports Server (NTRS)

    Cloyd, Richard A. (Inventor); Bryan, Thomas C. (Inventor)

    2003-01-01

    A passive ball capture joint has a sleeve with a plurality of bores distributed about a circumference thereof and formed therethrough at an acute angle relative to the sleeve's longitudinal axis. A spring-loaded retainer is slidingly fitted in each bore and is biased such that, if allowed, will extend at least partially into the sleeve to retain a ball therein. A ring, rotatably mounted about the bores, has an interior wall defining a plurality of shaped races that bear against the spring-loaded retainers. A mechanized rotational force producer is coupled to the ring. The ring can be rotated from a first position (that presses the retainers into the sleeve to lock the ball in place) to a second position (that allows the retainers to springback out of the sleeve to release the ball).

  13. Ball clay

    USGS Publications Warehouse

    Virta, Robert L.

    2010-01-01

    The article reports on the global market performance of ball clay in 2009 and presents an outlook for its 2010 performance. Several companies mined ball call in the country including Old Hickey Clay Co., Kentucky-Tennessee Clay Co., and H.C. Spinks Clay Co. Information on the decline in ball clay imports and exports is also presented.

  14. Damping Bearings In High-Speed Turbomachines

    NASA Technical Reports Server (NTRS)

    Von Pragenau, George L.

    1994-01-01

    Paper presents comparison of damping bearings with traditional ball, roller, and hydrostatic bearings in high-speed cryogenic turbopumps. Concept of damping bearings described in "Damping Seals and Bearings for a Turbomachine" (MFS-28345).

  15. Ball clay

    USGS Publications Warehouse

    Virta, R.L.

    2011-01-01

    The article discusses the latest developments in the global ball clay mining industry, particularly in the U.S., as of June 2011. It cites several firms that are involved in ball clay mining in the U.S., including HC Spins Clay Co. Inc., the Imerys Group and Old Hickory Clay Co. Among the products made from ball clay are ceramic tiles, sanitaryware, as well as fillers, extenders and binders.

  16. Ball clay

    USGS Publications Warehouse

    Virta, R.L.

    2013-01-01

    Four companies — H.C. Spinks Clay Co., Inc., Imerys, Old Hickory Clay Co. and Unimin Corp. — mined ball clay in five U.S. states in 2012. Production, on the basis of preliminary data, was 900 kt (992,000 st), with an estimated value of $42.3 million. This was a slight increase in tonnage from 886 kt (977,000 st), with a value of $40.9 million in 2011. Tennessee was the leading ball clay producing state, with 63 percent of domestic production, followed by Texas, Mississippi, Kentucky and Indiana. Reported ball clay production from Indiana probably was fire clay rather than ball clay. About 69 percent of total ball clay production was airfloat, 20 percent was crude and 11 percent was water-slurried.

  17. Ball lightning

    NASA Astrophysics Data System (ADS)

    Stenhoff, Mark

    Ball lightning is alleged by some to be a rare atmospheric phenomenon usually associated with thunderstorms, while others hold that it does not exist. This controversy has continued for centuries. This study comprises a critical evaluation of evidence for the existence of ball lightning. An historical review of the controversy is first presented, giving a chronological account of developments in ball lightning theories and of important observations alleged to be of the phenomenon. Other phenomena which might be mistaken for ball lightning are then subjected to a more detailed study than has hitherto been published, and the means by which such misidentifications could be recognized areestablished. A discussion of psychological and perceptual aspects indicates that descriptions could not always be taken at face value, and that many accounts of alleged ball lightning would be expected to contain substantial inaccuracies. The original intention to evaluate cases of alleged ball lightning already published in scientific journals was abandoned because there was no standardisation of information content, and because the majority of reports contained insufficient information for evaluation. Many reports had been written in a style which indicated an assumption that ball lightning was the cause of the event. Approximately 200 unpublished reports were therefore collected and subjected to evaluation. It was found that the majority of reports of alleged ball lightning could be explained by other means, and there was only a very small residue of reports which could not easily be thus explained. A large proportion of the reports could be attributed to corona discharge effects such as St Elmo's fire, or by familiar effects of conventional linear lightning. The validity of many previously published statistical studies of ball lightning was shown to be doubtful. The thesis concludes with a comparitive discussion of the merits and demerits of some of the diverse physical models

  18. Golf Ball

    NASA Technical Reports Server (NTRS)

    1998-01-01

    The Ultra 500 Series golf balls, introduced in 1995 by Wilson Sporting Goods Company, has 500 dimples arranged in a pattern of 60 spherical triangles. The design employs NASA's aerodynamics technology analysis of air loads of the tank and Shuttle orbiter that was performed under the Space Shuttle External Tank program. According to Wilson, this technology provides 'the most symmetrical ball surface available, sustaining initial velocity longer and producing the most stable ball flight for unmatched accuracy and distance.' The dimples are in three sizes, shapes and depths mathematically positioned for the best effect. The selection of dimples and their placement optimizes the interaction of opposing forces of lift and drag. Large dimples reduce air drag, enhance lift, and maintain spin for distance. Small dimples prevent excessive lift that destabilizes the ball flight and the medium size dimples blend the other two.

  19. Holy balls!

    NASA Astrophysics Data System (ADS)

    Truscott, Tadd; Belden, Jesse

    2011-11-01

    Why can some balls walk on water while others cannot? We investigate the rebound dynamics of elastic spheres impacting on a free-surface. Several variables determine whether or not a sphere will bounce when impacting a free-surface including velocity, impact angle, size and elasticity. Stiff elastic spheres, such as a racquetball, successfully skip at low impact angles and high velocities, but tend not to bounce when the impact angle becomes too large. However, the more compliant Waboba (WAter BOuncing BAll) bounces marvelously even at very high impact angles. Unlike a stiffer ball, the Waboba flattens out quickly as it is forming a cavity. The cavity lip forms a ramp and the flattened ball then skips off the water surface. We demonstrate how this phenomenon surprisingly resembles a skipping stone. Using high-speed video we explore the rebound dynamics for various values of elasticity, velocity, angle and size and determine when an object will bounce off the water surface.

  20. Ball clay

    USGS Publications Warehouse

    Virta, R.L.

    2007-01-01

    The article offers information on ball clay. Among the companies that mine ball clay in the U.S. are H.C. Spinks Clay, Kentucky-Tennessee Clay and Old Hickory Clay. In 2006, an estimated 1.2 million tons of the mineral was sold or used domestically and exported. Forty-percent of the total sales is accounted for ceramic floor and wall tile followed by sanitaryware and miscellaneous ceramics. Its average value was $ 45 per ton in 2006.

  1. Science of Ball Lightning (Fire Ball)

    NASA Astrophysics Data System (ADS)

    Ohtsuki, Yoshi-Hiko

    1989-08-01

    The Table of Contents for the full book PDF is as follows: * Organizing Committee * Preface * Ball Lightning -- The Continuing Challenge * Hungarian Ball Lightning Observations in 1987 * Nature of Ball Lightning in Japan * Phenomenological and Psychological Analysis of 150 Austrian Ball Lightning Reports * Physical Problems and Physical Properties of Ball Lightning * Statistical Analysis of the Ball Lightning Properties * A Fluid-Dynamical Model for Ball Lightning and Bead Lightning * The Lifetime of Hill's Vortex * Electrical and Radiative Properties of Ball Lightning * The Candle Flame as a Model of Ball Lightning * A Model for Ball Lightning * The High-Temperature Physico-Chemical Processes in the Lightning Storm Atmosphere (A Physico-Chemical Model of Ball Lightning) * New Approach to Ball Lightning * A Calculation of Electric Field of Ball Lightning * The Physical Explanation to the UFO over Xinjiang, Northern West China * Electric Reconnection, Critical Ionization Velocity, Ponderomotive Force, and Their Applications to Triggered and Ball Lightning * The PLASMAK™ Configuration and Ball Lightning * Experimental Research on Ball Lightning * Performance of High-Voltage Test Facility Designed for Investigation of Ball Lightning * List of Participants

  2. Structural dynamic analysis of a ball joint

    NASA Astrophysics Data System (ADS)

    Hwang, Seok-Cheol; Lee, Kwon-Hee

    2012-11-01

    Ball joint is a rotating and swiveling element that is typically installed at the interface between two parts. In an automobile, the ball joint is the component that connects the control arms to the steering knuckle. The ball joint can also be installed in linkage systems for motion control applications. This paper describes the simulation strategy for a ball joint analysis, considering manufacturing process. Its manufacturing process can be divided into plugging and spinning. Then, the interested responses is selected as the stress distribution generated between its ball and bearing. In this paper, a commercial code of NX DAFUL using an implicit integration method is introduced to calculate the response. In addition, the gap analysis is performed to investigate the fitness, focusing on the response of the displacement of a ball stud. Also, the optimum design is suggested through case studies.

  3. Laser tracking robot-performance calibration system using ball-seated bearing mechanisms and a spherically shaped cat's-eye retroreflector

    NASA Astrophysics Data System (ADS)

    Nakamura, Osamu; Goto, Mitsuo; Toyoda, Kouji; Takai, Nozomi; Kurosawa, Toshiro; Nakamata, Tohru

    1994-04-01

    The paper proposes a robot calibration system. A new cat's-eye retroreflector with n = 2 and interferometric scanning mechanisms with spherical seat bearings was shown to improve the measurement accuracy of the multilaser coordinate measuring system. The paper therefore describes a two dimensional self-calibration method for industrial robots by employing the three laser interferometers. Another interferometer will make it attainable to do the calibration in a 3D space. Discussed are the details of the system developed which consists of three laser interferometers: 3D tracking mechanisms, an error-estimating algorithm, and a new cat's-eye retroreflector. Experimental results for a commercial industrial robot coordinate calibration is presented.

  4. Ball clay

    USGS Publications Warehouse

    Virta, R.L.

    2012-01-01

    Four companies — H.C. Spinks Clay Co., Inc., Imerys Group, Old Hickory Clay Co., and Unimin Corp. — mined ball clay in four states in 2011. Production, on the basis of preliminary data, was 940 kt (1.04 million st) with an estimated value of $44.2 million. This is a 3-percent increase in tonnage from 912 kt (1.01 million st) with a value of $41.3 million that was produced in 2010. Tennessee was the leading producing state with 63 percent of domestic production, followed by Texas, Mississippi and Kentucky. About 69 percent of production was airfloat, 20 percent was crude and 11 percent was water-slurried.

  5. Cryogenic Hybrid Magnetic Bearing

    NASA Technical Reports Server (NTRS)

    Meeks, Crawford R.; Dirusso, Eliseo; Brown, Gerald V.

    1994-01-01

    Cryogenic hybrid magnetic bearing is example of class of magnetic bearings in which permanent magnets and electromagnets used to suspend shafts. Electromagnets provide active control of position of shaft. Bearing operates at temperatures from -320 degrees F (-196 degrees C) to 650 degrees F (343 degrees C); designed for possible use in rocket-engine turbopumps, where effects of cryogenic environment and fluid severely limit lubrication of conventional ball bearings. This and similar bearings also suitable for terrestrial rotating machinery; for example, gas-turbine engines, high-vacuum pumps, canned pumps, precise gimbals that suspend sensors, and pumps that handle corrosive or gritty fluids.

  6. Cartridge Bearing System for Space Applications

    NASA Technical Reports Server (NTRS)

    Kingsbury, Edward P.; Hanson, Robert A.; Jones, William R.; Mohr, Terry W.

    1999-01-01

    Conventional spin axis ball bearings have been unreliable in spacecraft, often failing by two heretofore uncontrolled processes: ball retainer instability and lubricant breakdown. The Space Cartridge Bearing System (SCBS) addresses each of these mechanisms directly, leading to a bearing system with absolute freedom from retainer instability and negligible lubricant degradation rate. The result is a reliable plug-in bearing cartridge with a definite design life.

  7. Spherical bearing. [to reduce vibration effects

    NASA Technical Reports Server (NTRS)

    Myers, W. N.; Hein, L. A. (Inventor)

    1978-01-01

    A spherical bearing including an inner ball with an opening for receiving a shaft and a spherical outer surface is described. Features of the bearing include: (1) a circular outer race including a plurality of circumferentially spaced sections extending around the inner ball for snugly receiving the inner ball; and (2) a groove extending circumferentially around the race producing a thin wall portion which permits the opposed side portions to flex relative to the ball for maximizing the physical contact between the inner surface of the race and the spherical outer surface of the ball.

  8. Bouncing Balls that Spin

    ERIC Educational Resources Information Center

    Knipp, Peter

    2008-01-01

    When a ball bounces elastically against a floor, the vertical component (v[subscript y]) of the velocity of the ball's mass-center changes sign. This is a special case of the elastic collision of two balls (i.e., two objects, neither of which is much more massive than the other), in which case the balls' post-collision relative velocity (=…

  9. Testing and Lubrication for Single Race Bearings

    SciTech Connect

    Steinhoff, R.G.

    1998-03-04

    Three ES and H-compatible lubricants (Environment, Safety and Health) for single race bearing applications and one hybrid-material single race bearings were evaluated and compared against single race bearings with trichlorotrifluoroethane (Freon) deposition of low molecular weight polytetrafluoroethylene (PTFE) bearing lubricant extracted from Vydax{trademark}. Vydax is a product manufactured by DuPont consisting of various molecular weights of PTFE suspended in trichlorotrifluoroethane (Freon), which is an ozone-depleting solvent. Vydax has been used as a bearing lubricant in stronglink mechanisms since 1974. Hybrid bearings with silicon nitride balls and molded glass-nylon-Teflon retainers, bearings lubricated with titanium carbide (TiC) on the balls, bearings lubricated with sputtered MoS{sub 2} on races and retainers, and bearings lubricated with electrophoretically deposited MoS{sub 2} were evaluated. The bearings were maintained in a preloaded state in bearing cartridges during cycling and vibration tests. Bearings with electrophoretically deposited MoS{sub 2} performed as well as bearings lubricated with Vydax and were the best performing candidate. All candidates were suitable for low preload applications. Bearings with TiC coated balls and bearings lubricated with sputtered MoS{sub 2} on the races and retainers performed well at high preloads, though not as well as bearings lubricated with electrophoretic deposition of MoS{sub 2}. Bearings with silicon nitride balls were not suitable for high preload applications.

  10. Foil bearings

    NASA Astrophysics Data System (ADS)

    Elrod, David A.

    1993-11-01

    The rolling element bearings (REB's) which support many turbomachinery rotors offer high load capacity, low power requirements, and durability. Two disadvantages of REB's are: (1) rolling or sliding contact within the bearing has life-limiting consequences; and (2) REB's provide essentially no damping. The REB's in the Space Shuttle Main Engine (SSME) turbopumps must sustain high static and dynamic loads, at high speeds, with a cryogenic fluid as lubricant and coolant. The pump end ball bearings limit the life of the SSME high pressure oxygen turbopump (HPOTP). Compliant foil bearing (CFB) manufacturers have proposed replacing turbopump REB's with CFB's CFB's work well in aircraft air cycle machines, auxiliary power units, and refrigeration compressors. In a CFB, the rotor only contracts the foil support structure during start up and shut down. CFB damping is higher than REB damping. However, the load capacity of the CFB is low, compared to a REB. Furthermore, little stiffness and damping data exists for the CFB. A rotordynamic analysis for turbomachinery critical speeds and stability requires the input of bearing stiffness and damping coefficients. The two basic types of CFB are the tension-dominated bearing and the bending-dominated bearing. Many investigators have analyzed and measured characteristics of tension-dominated foil bearings, which are applied principally in magnetic tape recording. The bending-dominated CFB is used more in rotating machinery. This report describes the first phase of a structural analysis of a bending-dominated, multileaf CFB. A brief discussion of CFB literature is followed by a description and results of the present analysis.

  11. Foil bearings

    NASA Technical Reports Server (NTRS)

    Elrod, David A.

    1993-01-01

    The rolling element bearings (REB's) which support many turbomachinery rotors offer high load capacity, low power requirements, and durability. Two disadvantages of REB's are: (1) rolling or sliding contact within the bearing has life-limiting consequences; and (2) REB's provide essentially no damping. The REB's in the Space Shuttle Main Engine (SSME) turbopumps must sustain high static and dynamic loads, at high speeds, with a cryogenic fluid as lubricant and coolant. The pump end ball bearings limit the life of the SSME high pressure oxygen turbopump (HPOTP). Compliant foil bearing (CFB) manufacturers have proposed replacing turbopump REB's with CFB's CFB's work well in aircraft air cycle machines, auxiliary power units, and refrigeration compressors. In a CFB, the rotor only contracts the foil support structure during start up and shut down. CFB damping is higher than REB damping. However, the load capacity of the CFB is low, compared to a REB. Furthermore, little stiffness and damping data exists for the CFB. A rotordynamic analysis for turbomachinery critical speeds and stability requires the input of bearing stiffness and damping coefficients. The two basic types of CFB are the tension-dominated bearing and the bending-dominated bearing. Many investigators have analyzed and measured characteristics of tension-dominated foil bearings, which are applied principally in magnetic tape recording. The bending-dominated CFB is used more in rotating machinery. This report describes the first phase of a structural analysis of a bending-dominated, multileaf CFB. A brief discussion of CFB literature is followed by a description and results of the present analysis.

  12. Liquid oxygen cooled bearing ignition potential assessment

    NASA Technical Reports Server (NTRS)

    Page, Arthur T.; Goode, Brian K.; Owen, James W.

    1990-01-01

    Space Shuttle Main Engine High Pressure Oxygen Turbopump bearings have shown evidence of heavy oxidation on the surfaces of the balls and races. Extensive analyses were performed to assess the ignition potential in the bearing system during normal and off-nominal operation. Test programs and analyses were used to determine the bearing thermal condition and bearing material ignition characteristics.

  13. Ball valve extractor

    DOEpatents

    Herndon, Charles; Brown, Roger A.

    2002-01-01

    An apparatus and process for removing a ball valve is provided. The ball valve removal tool provides a handle sliding along the length of a shaft. One end of the shaft is secured within an interior cavity of a ball valve while the opposite end of the shaft defines a stop member. By providing a manual sliding force to the handle, the handle impacts the stop member and transmits the force to the ball valve. The direction of the force is along the shaft of the removal tool and disengages the ball valve from the ball valve housing.

  14. An experimental evaluation of the stresses in drilled balls

    NASA Technical Reports Server (NTRS)

    Nypan, L. J.; Coe, H. H.; Scibbe, H. W.

    1974-01-01

    Stresses in dimensionally similar large models of 40-, 50- and 60-percent mass reduction cylindrically hollow 'drilled' bearing balls were experimentally evaluated with flat strain gage rosettes. Dimensionless principal stress coefficients were calculated and were applied to estimate the bending stresses in the drilled balls of three series of full-scale bearing experiments. Stresses were highest when the applied load approached the edge of the hole, and ranged up to almost 620 million Newtons per sq m at the bore.

  15. Having a Ball with Fitness Balls

    ERIC Educational Resources Information Center

    McNulty, Betty

    2011-01-01

    Fitness programs can be greatly enhanced with the addition of fitness balls. They are a fun, challenging, economical, and safe way to incorporate a cardiovascular, strength, and stretching program for all fitness levels in a physical education setting. The use of these balls has become more popular during the last decade, and their benefits and…

  16. Single ball bearing lubricant and material evaluator

    NASA Technical Reports Server (NTRS)

    Hall, Philip B. (Inventor); Novak, Howard L. (Inventor)

    2005-01-01

    A test apparatus provides an applied load to a monoball through a trolley which moves along a loading axis. While applying the load to the monoball, the torque meter is in communication with the spherical monoball, and a load cell senses the application of applied force to the monoball. Meanwhile, a rotary actuary imports rotary oscillating motion to the monoball which is sensed by a position sensor and a torque meter. Accordingly, a processor can determine the coefficient of friction in substantially real time along with a cycles per second rate.

  17. The Goldenrod Ball Gall

    ERIC Educational Resources Information Center

    Fischer, Richard B.

    1974-01-01

    The paper presents a generalized life history of the goldenrod ball gall, a ball-shaped swelling found almost exclusively on the Canada goldenrod, Solidago canadensis, and caused by a peacock fly know as Eurosta soldiaginis. (KM)

  18. Ball Screw Actuator Including a Compliant Ball Screw Stop

    NASA Technical Reports Server (NTRS)

    Wingett, Paul T. (Inventor); Hanlon, Casey (Inventor)

    2015-01-01

    An actuator includes a ball nut, a ball screw, and a ball screw stop. The ball nut is adapted to receive an input torque and in response rotates and supplies a drive force. The ball screw extends through the ball nut and has a first end and a second end. The ball screw receives the drive force from the ball nut and in response selectively translates between a retract position and a extend position. The ball screw stop is mounted on the ball screw proximate the first end to translate therewith. The ball screw stop engages the ball nut when the ball screw is in the extend position, translates, with compliance, a predetermined distance toward the first end upon engaging the ball nut, and prevents further rotation of the ball screw upon translating the predetermined distance.

  19. Fizz-Ball Fizzics

    ERIC Educational Resources Information Center

    Moinester, Murray; Gerland, Lars; Liger-Belair, Gerard; Ocherashvili, Aharon

    2012-01-01

    We describe the fluid dynamics principles governing the up-down oscillatory cycling of a bubble-covered, low-density, low-mass ball of material (referred to henceforth as a "fizz-ball") immersed inside a glass of bubbling (super-saturated) carbonated liquid. The bubbles serve to desaturate the liquid of excess CO[subscript 2]. The fizz-ball acts…

  20. Lubricant effects on bearing life

    NASA Technical Reports Server (NTRS)

    Zaretsky, Erwin V.

    1986-01-01

    Lubricant considerations for rolling-element bearings have within the last two decades taken on added importance in the design and operation of mechanical systems. The phenomenon which limits the useful life of bearings is rolling-element or surface pitting fatigue. The elastohydrodynamic (EHD) film thickness which separates the ball or roller surface from those of the raceways of the bearing directly affects bearing life. Chemical additives added to the lubricant can also significantly affect bearings life and reliability. The interaction of these physical and chemical effects is important to the design engineer and user of these systems. Design methods and lubricant selection for rolling-element bearings are presented and discussed.

  1. Effects of bearing cleaning and lube environment on bearing performance

    NASA Technical Reports Server (NTRS)

    Ward, Peter C.

    1995-01-01

    Running torque data of SR6 ball bearings are presented for different temperatures and speeds. The data are discussed in contrast to generally used torque prediction models and point out the need to obtain empirical data in critical applications. Also, the effects of changing bearing washing techniques from old, universally used CFC-based systems to CFC-free aqueous/alkaline solutions are discussed. Data on wettability, torque and lubricant life using SR3 ball bearings are presented. In general, performance is improved using the new aqueous washing techniques.

  2. Service Lives Of Restored Bearings

    NASA Technical Reports Server (NTRS)

    Zaretsky, Erwin V.

    1988-01-01

    Rebuilt units last almost as long as new ones. Report describes theoretical and experiemental studies of lifetimes of restored ball and cylindrical-roller bearings. Results of this and related studies have implications of economy and safety in modern high-speed machinery, especially in aircraft industry, where inspection and rejection or replacing of bearings are new standard practice.

  3. Balls on the Lawn

    NASA Astrophysics Data System (ADS)

    Mallows, Colin L.; Shapiro, Lou

    1999-03-01

    In the "tennis ball" problem we are given successive pairs of balls numbered (1,2), (3,4),... At each stage we throw one ball out of the window. After n stages some set of n balls is on the lawn. We find a generating function and a closed formula for the sequence 3, 23, 131, 664, 3166, 14545, 65187, 287060, 1247690,..., the n-th term of which gives the sum over all possible arrangements of the total of the numbers on the balls on the lawn. The problem has connections with "bicolored Motzkin paths" and the ballot problem.

  4. Stemless ball valve

    NASA Technical Reports Server (NTRS)

    Burgess, Kevin (Inventor); Yakos, David (Inventor); Walthall, Bryan (Inventor)

    2012-01-01

    A stemless ball valve comprising: a right flange; left flange; ball with an axis pin and two travel pins; ball seal on either side of the ball; guide sleeve with inner walls comprising two channels; cartridge guide holder; inner magnetic cartridge; and outer magnetic cartridge. The ball is situated inside of the guide sleeve, and a travel pin is located in each of the two channels. The guide sleeve is situated inside of the cartridge guide holder, which is located adjacent to and outside of the inner magnetic cartridge and secured to the inner magnetic cartridge such that when the inner magnetic cartridge rotates, the cartridge guide holder also rotates. The cartridge guide holder is secured to the guide sleeve such that when the cartridge guide holder rotates, the travel pins move within the channels in the inner walls of the guide sleeve, thereby causing the ball to rotate.

  5. Physics of ball sports

    NASA Astrophysics Data System (ADS)

    Cohen, C.; Clanet, C.

    2016-06-01

    Ball sports have been part of human history for thousands of years [1]. Nowadays, 13 of them are part of the Olympic games (badminton, basketball, beach volley, football/soccer, golf, handball, hockey, rugby, table tennis, tennis, volleyball, water polo, ice hockey). All these games differ by launcher (hand, club, racket, bat), ball (size, shape and mass), pitch size and number of players. These differences induce different ball velocities. Apart from the velocities and the way to maximize them, we discuss in this article the ball trajectories and their impact on the size of sports fields.

  6. Birth of ball lightning

    NASA Astrophysics Data System (ADS)

    Lowke, J. J.; Smith, D.; Nelson, K. E.; Crompton, R. W.; Murphy, A. B.

    2012-10-01

    Many observations of ball lightning report a ball of light, about 10 cm in diameter, moving at about walking speed, lasting up to 20 s and frequently existing inside of houses and even aeroplanes. The present paper reports detailed observations of the initiation or birth of ball lightning. In two cases, navigation crew of aircraft saw ball lightning form at the windscreen inside the cockpit of their planes. In the first case, the ball lightning occurred during a thunderstorm, with much lightning activity outside of the plane. In the second case, large "horns" of electrical corona were seen outside of the plane at the surface of the radome, just prior to the formation of the ball lightning. A third case reports ball lightning formed inside of a house, during a thunderstorm, at a closed glass window. It is proposed, based on two-dimensional calculations of electron and ion transport, that ball lightning in these cases is driven and formed by atmospheric ions impinging and collecting on the insulating surface of the glass or Perspex windows. This surface charge can produce electric fields inside of the cockpit or room sufficient to sustain an electric discharge. Charges of opposite sign to those outside of the window accumulate on the inside surface of the glass, leaving a ball of net charge moving inside of the cockpit or room to produce a pulsed discharge on a microsecond time scale.

  7. Quartz ball valve

    NASA Technical Reports Server (NTRS)

    Goetz, C.; Ingle, W. M. (Inventor)

    1980-01-01

    A ball valve particularly suited for use in the handling of highly corrosive fluids is described. It is characterized by a valve housing formed of communicating segments of quartz tubing, a pair of communicating sockets disposed in coaxial alignment with selected segments of tubing for establishing a pair of inlet ports communicating with a common outlet port, a ball formed of quartz material supported for displacement between the sockets and configured to be received alternately thereby, and a valve actuator including a rod attached to the ball for selectively displacing the ball relative to each of the sockets for controlling fluid flow through the inlet ports.

  8. Optimized Coolant-Flow Diverter For Increased Bearing Life

    NASA Technical Reports Server (NTRS)

    Subbaraman, Maria R.; Butner, Myles F.

    1995-01-01

    Coolant-flow diverter for rolling-element bearings in cryogenic turbopump designed to enhance cooling power of flow in contact with bearings and thereby reduce bearing wear. Delivers jets of coolant as close as possible to hot spots at points of contact between balls and race. Also imparts swirl that enhances beneficial pumping effect. Used with success in end ball bearing of high-pressure-oxidizer turbopump.

  9. Positive commandable oiler for satellite bearing lubrication

    NASA Technical Reports Server (NTRS)

    James, G. E.

    1977-01-01

    On-orbit commandable lubrication of ball bearings accomplished by direct oil application to the moving ball surfaces was studied. Test results for the lubricant applicator portion of the system are presented in conjunction with a design approach for the reservoir and metering components.

  10. Bearings and gears for advanced turbine engines and transmissions

    NASA Technical Reports Server (NTRS)

    Parker, R. J.

    1975-01-01

    The improved technology is discussed of engine main-shaft ball bearings, and spur gears in power transmission drive trains. Much of the technology can be applied to other ball and roller bearings, and to other spur and bevel gears throughout the engine, drive train, and accessory systems.

  11. Ball Collision Experiments

    ERIC Educational Resources Information Center

    Cross, R.

    2015-01-01

    Experiments are described on collisions between two billiard balls and between a bat and a ball. The experiments are designed to extend a student's understanding of collision events and could be used either as a classroom demonstration or for a student project.

  12. Great balls of fire

    NASA Astrophysics Data System (ADS)

    Stenhoff, Mark; reader01; jjherrera

    2014-03-01

    In reply to the physicsworld.com news article “Burning soil fuels ball lightning” (9 January, http://ow.ly/tl8aO) on evidence that a burning core of soil acts as an energy source for ball lightning.

  13. Stemless ball valve

    NASA Technical Reports Server (NTRS)

    Burgess, Kevin (Inventor); Yakos, David (Inventor); Walthall, Bryan (Inventor)

    2011-01-01

    A stemless ball valve comprising two flanges and a ball with a channel, two axis pins and two travel pins. One end of each axis and travel pin is fixedly attached to the ball, and the other end of each axis pin is lodged into a notch in the first or second flange such that the axis pin is allowed to rotate in the notch. The guide sleeve comprises two channels, and one end of each travel pin is situated within one of the two channels in the guide sleeve. An outer magnetic cartridge causes the inner magnetic cartridge and guide sleeve to rotate, and when the guide sleeve rotates, the travel pins move up and down within the channels in the guide sleeve. The movement of the travel pins within the channels in the guide sleeve causes the ball to rotate, thereby opening and closing the ball valve.

  14. Monitoring Bearing Vibrations For Signs Of Damage

    NASA Technical Reports Server (NTRS)

    Martinez, Carol L.

    1991-01-01

    Real-time spectral analysis of vibrations being developed for use in monitoring conditions of critical bearings in rotating machinery. Underlying concept simple and fairly well established: appearance and growth of vibrations at frequencies associated with rotations of various parts of bearing system indicate wear, damage, and imperfections of manufacture. Frequencies include fundamental and harmonics of frequency of rotation of ball cage, frequency of passage of balls, and frequency of rotation of shaft.

  15. Tool Indicates Contact Angles In Bearing Raceways

    NASA Technical Reports Server (NTRS)

    Akian, Richard A.; Butner, Myles F.

    1995-01-01

    Tool devised for use in measuring contact angles between balls and races in previously operated ball bearings. Used on both inner and outer raceways of bearings having cross-sectional widths between approximately 0.5 and 2.0 in. Consists of integral protractor mounted in vertical plane on bracket equipped with leveling screws and circular level indicator. Protractor includes rotatable indicator needle and set of disks of various sizes to fit various raceway curvatures.

  16. Happy Balls, Unhappy Balls, and Newton's Cradle

    ERIC Educational Resources Information Center

    Kagan, David

    2010-01-01

    The intricacies of Newton's Cradle are well covered in the literature going as far back as the time of Newton! These discussions generally center on the highly elastic collisions of metal spheres. Thanks to the invention of happy and unhappy balls, you can build and study the interaction of less elastic systems (see Fig. 1).

  17. Happy Balls, Unhappy Balls, and Newton's Cradle

    NASA Astrophysics Data System (ADS)

    Kagan, David

    2010-03-01

    The intricacies of Newton's Cradle are well covered in the literature2-4 going as far back as the time of Newton!5 These discussions generally center on the highly elastic collisions of metal spheres. Thanks to the invention of happy and unhappy balls,6 you can build and study the interaction of less elastic systems (see Fig. 1).

  18. Research In Diagnosing Bearing Defects From Vibrations

    NASA Technical Reports Server (NTRS)

    Zoladz, T.; Earhart, E.; Fiorucci, T.

    1995-01-01

    Report describes research in bearing-defect signature analysis - use of vibration-signal analysis to diagnose defects in roller and ball bearings. Experiments performed on bearings in good condition and other bearings in which various parts scratched to provide known defects correlated with vibration signals. Experiments performed on highly instrumented motor-driven rotor assembly at speeds up to 10,050 r/min, using accelerometers, velocity probes, and proximity sensors mounted at various locations on assembly to measure vibrations.

  19. Compact Q-balls

    NASA Astrophysics Data System (ADS)

    Bazeia, D.; Losano, L.; Marques, M. A.; Menezes, R.; da Rocha, R.

    2016-07-01

    In this work we deal with non-topological solutions of the Q-ball type in two space-time dimensions, in models described by a single complex scalar field that engenders global symmetry. The main novelty is the presence of stable Q-balls solutions that live in a compact interval of the real line and appear from a family of models controlled by two distinct parameters. We find analytical solutions and study their charge and energy, and show how to control the parameters to make the Q-balls classically and quantum mechanically stable.

  20. Super Ball Bot

    NASA Video Gallery

    Tensegrity Robot: Child's Play or Space Tech? Super Ball Bot is an all-in-one landing and mobility platform based on tensegrity structures, allowing for lower-cost, and more reliable planetary miss...

  1. Quartz ball value

    NASA Technical Reports Server (NTRS)

    Goetz, C.; Ingle, W. M.

    1979-01-01

    Quartz ball valve consisting of two quartz joints sealed back-to-back and seated in quartz sockets perform at temperatures of up to 1,250 C and in corrosive chemical environments without contamination or degradation.

  2. Impact behavior of hollow balls

    NASA Astrophysics Data System (ADS)

    Cross, Rod

    2014-03-01

    Measurements are presented of the force acting on ping-pong and squash balls impacting on a force plate. Both ball types are hollow and have the same diameter but deform in very different ways. Ping pong balls are relatively stiff and buckle inwards at high impact speeds, while squash balls are softer and tend to squash or flatten. The buckling process generates a large-amplitude, high-frequency oscillation of the force acting on a ping-pong ball. Squash balls are initially very stiff before they soften, with the result that the force on the ball rises to about half its maximum value in the first 20 μs. Ping-pong balls have a high coefficient of restitution (COR), while squash balls have a low COR. Results for both ball types are interpreted in terms of additional experimental observations.

  3. Aerodynamics of sports balls

    NASA Technical Reports Server (NTRS)

    Mehta, R. D.

    1985-01-01

    Research data on the aerodynamic behavior of baseballs and cricket and golf balls are summarized. Cricket balls and baseballs are roughly the same size and mass but have different stitch patterns. Both are thrown to follow paths that avoid a batter's swing, paths that can curve if aerodynamic forces on the balls' surfaces are asymmetric. Smoke tracer wind tunnel tests and pressure taps have revealed that the unbalanced side forces are induced by tripping the boundary layer on the seam side and producing turbulence. More particularly, the greater pressures are perpendicular to the seam plane and only appear when the balls travel at velocities high enough so that the roughness length matches the seam heigh. The side forces, once tripped, will increase with spin velocity up to a cut-off point. The enhanced lift coefficient is produced by the Magnus effect. The more complex stitching on a baseball permits greater variations in the flight path curve and, in the case of a knuckleball, the unsteady flow effects. For golf balls, the dimples trip the boundary layer and the high spin rate produces a lift coefficient maximum of 0.5, compared to a baseball's maximum of 0.3. Thus, a golf ball travels far enough for gravitational forces to become important.

  4. Aerodynamics of sports balls

    NASA Astrophysics Data System (ADS)

    Mehta, R. D.

    Research data on the aerodynamic behavior of baseballs and cricket and golf balls are summarized. Cricket balls and baseballs are roughly the same size and mass but have different stitch patterns. Both are thrown to follow paths that avoid a batter's swing, paths that can curve if aerodynamic forces on the balls' surfaces are asymmetric. Smoke tracer wind tunnel tests and pressure taps have revealed that the unbalanced side forces are induced by tripping the boundary layer on the seam side and producing turbulence. More particularly, the greater pressures are perpendicular to the seam plane and only appear when the balls travel at velocities high enough so that the roughness length matches the seam heigh. The side forces, once tripped, will increase with spin velocity up to a cut-off point. The enhanced lift coefficient is produced by the Magnus effect. The more complex stitching on a baseball permits greater variations in the flight path curve and, in the case of a knuckleball, the unsteady flow effects. For golf balls, the dimples trip the boundary layer and the high spin rate produces a lift coefficient maximum of 0.5, compared to a baseball's maximum of 0.3. Thus, a golf ball travels far enough for gravitational forces to become important.

  5. Bearing fatigue investigation 3

    NASA Technical Reports Server (NTRS)

    Nahm, A. H.; Bamberger, E. N.; Signer, H. R.

    1982-01-01

    The operating characteristics of large diameter rolling-element bearings in the ultra high speed regimes expected in advanced turbine engines for high performance aircraft were investigated. A high temperature lubricant, DuPont Krytox 143 AC, was evaluated at bearing speeds to 3 million DN. Compared to the results of earlier, similar tests using a MIL-L-23699 (Type II) lubricant, bearings lubricated with the high density Krytox fluid showed significantly higher power requirements. Additionally, short bearing lives were observed when this fluid was used with AISI M50 bearings in an air atmosphere. The primary mode of failure was corrosion initiated surface distress (fatigue) on the raceways. The potential of a case-carburized bearing to sustain a combination of high-tangential and hertzian stresses without experiencing race fracture was also investigated. Limited full scale bearing tests of a 120 mm bore ball bearing at a speed of 25,000 rpm (3 million DN) indicated that a carburized material could sustain spalling fatigue without subsequent propagation to fracture. Planned life tests of the carburized material had to be aborted, however, because of apparent processing-induced material defects.

  6. Long-wearing TFE/metal bearings

    NASA Technical Reports Server (NTRS)

    Brass, R. A.; Gillon, W. A., Jr.

    1980-01-01

    Method for making metal/polytetrafluoroethylene (TFE) bearing surfaces embeds long-wearing layer of TFE in microscopic pits in metal. Technique has potential applications in automotive gears, ball joints, and roller chain components. Other applications are in use of unlubricated bearings in chemical, pharmaceutical, and food-processing equipment.

  7. Evaluation of bearing configurations using the single bearing tester in liquid nitrogen

    NASA Technical Reports Server (NTRS)

    Jett, T.; Hall, P.; Thom, R.

    1991-01-01

    Various bearing configurations were tested using the Marshall Space Flight Center single bearing tester with LN2 as the cryogenic coolant. The baseline was one Rocketdyne phase one high pressure oxidizer turbopump (HPOTP) pump end 45-mm bore bearing. The bearing configurations that were tested included a Salox/M cage configuration, a silicon nitride ball configuration, an elongated cage configuration, and a Bray 601 grease configuration.

  8. Ball lightning burn.

    PubMed

    Selvaggi, Gennaro; Monstrey, Stan; von Heimburg, Dennis; Hamdi, Mustapha; Van Landuyt, Koen; Blondeel, Phillip

    2003-05-01

    Ball lightning is a rare physical phenomenon, which is not yet completely explained. It is similar to lightning but with different, peculiar characteristics. It can be considered a mix of fire and electricity, concentrated in a fireball with a diameter of 20-cm that most commonly appears suddenly, even in indoor conditions, during a thunderstorm. It moves quickly for several meters, can change direction, and ultimately disappears. During a great storm, a 28-year-old man and his 5-year-old daughter sustained burn wounds after ball lightning came from the outdoors through a chimney. These two patients demonstrated signs of fire and electrical injuries. The father, who lost consciousness, sustained superficial second-degree burn wounds bilaterally on the zygomatic area and deep second-degree burn wounds on his right hand (total body surface area, 4%). His daughter demonstrated superficial second-degree burn wounds on the left part of the face and deep second-degree and third-degree burn wounds (total body surface area, 30%) on the left neck, both upper arms, and the back. In this article, the authors report the first two cases of burn injuries resulting from ball lightning contact indoors. The literature on this rare phenomenon is reviewed to elucidate the nature of ball lightning. Emphasis is placed on the nature of injuries after ball lightning contact, the therapy used, and the long-term complications.

  9. Ball lightning burn.

    PubMed

    Selvaggi, Gennaro; Monstrey, Stan; von Heimburg, Dennis; Hamdi, Mustapha; Van Landuyt, Koen; Blondeel, Phillip

    2003-05-01

    Ball lightning is a rare physical phenomenon, which is not yet completely explained. It is similar to lightning but with different, peculiar characteristics. It can be considered a mix of fire and electricity, concentrated in a fireball with a diameter of 20-cm that most commonly appears suddenly, even in indoor conditions, during a thunderstorm. It moves quickly for several meters, can change direction, and ultimately disappears. During a great storm, a 28-year-old man and his 5-year-old daughter sustained burn wounds after ball lightning came from the outdoors through a chimney. These two patients demonstrated signs of fire and electrical injuries. The father, who lost consciousness, sustained superficial second-degree burn wounds bilaterally on the zygomatic area and deep second-degree burn wounds on his right hand (total body surface area, 4%). His daughter demonstrated superficial second-degree burn wounds on the left part of the face and deep second-degree and third-degree burn wounds (total body surface area, 30%) on the left neck, both upper arms, and the back. In this article, the authors report the first two cases of burn injuries resulting from ball lightning contact indoors. The literature on this rare phenomenon is reviewed to elucidate the nature of ball lightning. Emphasis is placed on the nature of injuries after ball lightning contact, the therapy used, and the long-term complications. PMID:12792547

  10. Analysis of bearing stiffness variations, contact forces and vibrations in radially loaded double row rolling element bearings with raceway defects

    NASA Astrophysics Data System (ADS)

    Petersen, Dick; Howard, Carl; Sawalhi, Nader; Moazen Ahmadi, Alireza; Singh, Sarabjeet

    2015-01-01

    A method is presented for calculating and analyzing the quasi-static load distribution and varying stiffness of a radially loaded double row bearing with a raceway defect of varying depth, length, and surface roughness. The method is applied to ball bearings on gearbox and fan test rigs seeded with line or extended outer raceway defects. When balls pass through the defect and lose all or part of their load carrying capacity, the load is redistributed between the loaded balls. This includes balls positioned outside the defect such that good raceway sections are subjected to increased loading when a defect is present. The defective bearing stiffness varies periodically at the ball spacing, and only differs from the good bearing case when balls are positioned in the defect. In this instance, the stiffness decreases in the loaded direction and increases in the unloaded direction. For an extended spall, which always has one or more balls positioned in the defect, this results in an average stiffness over the ball spacing period that is lower in the loaded direction in comparison to both the line spall and good bearing cases. The variation in bearing stiffness due to the defect produces parametric excitations of the bearing assembly. The qualitative character of the vibration response correlates to the character of the stiffness variations. Rapid stiffness changes at a defect exit produce impulses. Slower stiffness variations due to large wavelength waviness features in an extended spall produce low frequency excitation which results in defect components in the velocity spectra. The contact forces fluctuate around the quasi-static loads on the balls, with rapid stiffness changes producing high magnitude impulsive force fluctuations. Furthermore, it is shown that analyzing the properties of the dynamic model linearized at the quasi-static solutions provides greater insight into the time-frequency characteristics of the vibration response. This is demonstrated by relating

  11. Review and critical analysis: Rolling-element bearings for system life and reliability

    NASA Technical Reports Server (NTRS)

    Irwin, A. S.; Anderson, W. J.; Derner, W. J.

    1985-01-01

    A ball and cylindrical roller bearing technical specification which incorporates the latest state-of-the-art advancements was prepared for the purpose of improving bearing reliability in U.S. Army aircraft. The current U.S. Army aviation bearing designs and applications, including life analyses, were analyzed. A bearing restoration and refurbishment specification was prepared to improve bearing availability.

  12. Hex ball torque test

    NASA Technical Reports Server (NTRS)

    Robinson, B. A.; Foster, C. L.

    1986-01-01

    A series of torque tests were performed on four flight-type hex ball universal joints in order to characterize and determine the actual load-carrying capability of this device. The universal joint is a part of manual actuation rods for scientific instruments within the Hubble Space Telescope. It was found that the hex ball will bind slightly during the initial load application. This binding did not affect the function of the universal joint, and the units would wear-in after a few additional loading cycles. The torsional yield load was approximately 50 ft-lb, and was consistent among the four test specimens. Also, the torque required to cause complete failure exceeded 80 ft-lb. It is concluded that the hex ball universal joint is suitable for its intended applications.

  13. Computer-aided selection of materials for cryogenic turbopump bearings

    NASA Technical Reports Server (NTRS)

    Maurer, R. E.; Pallini, R. A.

    1985-01-01

    The life requirement for the angular contact ball bearings in the Space Shuttle Main Engine (SSME) high-pressure-oxygen turbopump (HPOTP) is 7.5 hours. In actual operation, significantly shorter service life has been experienced. The objective of this current program is to identify bearing materials and/or materials processing techniques offering significant potential for extending HPOTP bearing performance life. A thermomechanical analysis of the HPOTP shaft/bearing system was performed with the SHABERTH (SHaft-BEaring-THermal) computer program. Bearing fatigue life, ball-race contact stress, heat generation rate, bulk ring temperatures, and circumferential stress in the inner rings were quantified as functions of radial load, thrust load, and ball-race contact friction. The analysis results were used to formulate criteria that are being used for the selection of special materials for future turbopump bearings.

  14. Horizontal Air Bearing Experiment Number 1

    SciTech Connect

    Clauson, T.L.

    1999-08-31

    The Horizontal Air Bearing Experiment No.1 is a series of tests intended to further the understanding of rotational dynamics. A simple experimental assembly is rotated using the Horizontal Air Bearing and allowed to spin freely as the internal rotational damping is measured. The low friction of the bearing effectively isolates the test assembly, allowing the internal damping of the test object to be evaluated. The experimental assembly is composed of an aluminum ball within a spherical cavity. A flanged pipe section and an auxiliary adapter plate secure the assembly to the Air Bearing interface plate. Three aluminum balls are interchanged to vary test parameters. The aluminum balls are free to move independently as the entire assembly rotates. The aluminum balls vary in diameter and/or surface finish. While the diameter and surface finish is varied, the space between the ball and socket is dry. To examine the effect of viscosity, the space is filled with a lubricant while the ball diameter and surface finish is held constant.

  15. Balls and Spheres

    ERIC Educational Resources Information Center

    Szekely, George

    2011-01-01

    This article describes an art lesson that allows students to set up and collect sphere canvases. Spheres move art away from a rectangular canvas into a dimension that requires new planning and painting. From balls to many other spherical canvases that bounce, roll, float and fly, art experiences are envisioned by students. Even if adults recognize…

  16. Magnetic bearings for a high-performance optical disk buffer

    NASA Technical Reports Server (NTRS)

    Hockney, Richard; Hawkey, Timothy

    1993-01-01

    An optical disk buffer concept can provide gigabit-per-second data rates and terabit capacity through the use of arrays of solid state lasers applied to a stack of erasable/reusable optical disks. The RCA optical disk buffer has evoked interest by NASA for space applications. The porous graphite air bearings in the rotary spindle as well as those used in the linear translation of the read/write head would be replaced by magnetic bearings or mechanical (ball or roller) bearings. Based upon past experience, roller or ball bearings for the translation stages are not feasible. Unsatisfactory, although limited experience exists with ball bearing spindles also. Magnetic bearings, however, appear ideally suited for both applications. The use of magnetic bearings is advantageous in the optical disk buffer because of the absence of physical contact between the rotating and stationary members. This frictionless operation leads to extended life and reduced drag. The manufacturing tolerances that are required to fabricate magnetic bearings would also be relaxed from those required for precision ball and gas bearings. Since magnetic bearings require no lubricant, they are inherently compatible with a space (vacuum) environment. Magnetic bearings also allow the dynamics of the rotor/bearing system to be altered through the use of active control. This provides the potential for reduced vibration, extended regions of stable operation, and more precise control of position.

  17. Detonator-activated ball shutter

    DOEpatents

    McWilliams, R.A.; Holle, W.G. von.

    1983-08-16

    A detonator-activated ball shutter for closing an aperture in about 300[mu] seconds. The ball shutter containing an aperture through which light, etc., passes, is closed by firing a detonator which propels a projectile for rotating the ball shutter, thereby blocking passage through the aperture. 3 figs.

  18. Detonator-activated ball shutter

    DOEpatents

    McWilliams, Roy A.; von Holle, William G.

    1983-01-01

    A detonator-activated ball shutter for closing an aperture in about 300.mu. seconds. The ball shutter containing an aperture through which light, etc., passes, is closed by firing a detonator which propels a projectile for rotating the ball shutter, thereby blocking passage through the aperture.

  19. Visual Skills: Watch the Ball?

    ERIC Educational Resources Information Center

    Moen, Sue

    1989-01-01

    In tennis as well as in other racket/paddle sports, simply watching the ball does not guarantee success in hitting the ball to the desired location. Teachers and coaches should teach players to integrate available visual, spatial, and kinesthetic information. Several drills for good ball contact are outlined. (IAH)

  20. Stemless Ball Valve

    NASA Technical Reports Server (NTRS)

    Burgess, Robert K.; Yakos, David; Walthall, Bryan

    2012-01-01

    This invention utilizes a new method of opening and closing a ball valve. Instead of rotating the ball with a perpendicular stem (as is the case with standard ball valves), the ball is rotated around a fixed axis by two guide pins. This innovation eliminates the leak point that is present in all standard ball valves due to the penetration of an actuation stem through the valve body. The VOST (Venturi Off-Set-Technology) valve has been developed for commercial applications. The standard version of the valve consists of an off-set venturi flow path through the valve. This path is split at the narrowest portion of the venturi, allowing the section upstream from the venturi to be rotated. As this rotation takes place, the venturi becomes restricted as one face rotates with respect to the other, eventually closing off the flow path. A spring-loaded seal made of resilient material is embedded in the upstream face of the valve, making a leak-proof seal between the faces; thus a valve is formed. The spring-loaded lip seal is the only seal that can provide a class six, or bubble-tight, seal against the opposite face of the valve. Tearing action of the seal by high-velocity gas on this early design required relocation of the seal to the downstream face of the valve. In the stemless embodiment of this valve, inner and outer magnetic cartridges are employed to transfer mechanical torque from the outside of the valve to the inside without the use of a stem. This eliminates the leak path caused by the valve stems in standard valves because the stems penetrate through the bodies of these valves.

  1. Modeling of rolling element bearing mechanics. Theoretical manual

    NASA Astrophysics Data System (ADS)

    Merchant, David H.; Greenhill, Lyn M.

    1994-10-01

    This report documents the theoretical basis for the Rolling Element Bearing Analysis System (REBANS) analysis code which determines the quasistatic response to external loads or displacement of three types of high-speed rolling element bearings: angular contact ball bearings; duplex angular contact ball bearings; and cylindrical roller bearings. The model includes the effects of bearing ring and support structure flexibility. It is comprised of two main programs: the Preprocessor for Bearing Analysis (PREBAN) which creates the input files for the main analysis program; and Flexibility Enhanced Rolling Element Bearing Analysis (FEREBA), the main analysis program. A companion report addresses the input instructions for and features of the computer codes. REBANS extends the capabilities of the SHABERTH (Shaft and Bearing Thermal Analysis) code to include race and housing flexibility, including such effects as dead band and preload springs.

  2. Modeling of rolling element bearing mechanics. Computer program user's manual

    NASA Astrophysics Data System (ADS)

    Greenhill, Lyn M.; Merchant, David H.

    1994-10-01

    This report provides the user's manual for the Rolling Element Bearing Analysis System (REBANS) analysis code which determines the quasistatic response to external loads or displacement of three types of high-speed rolling element bearings: angular contact ball bearings, duplex angular contact ball bearings, and cylindrical roller bearings. The model includes the defects of bearing ring and support structure flexibility. It is comprised of two main programs: the Preprocessor for Bearing Analysis (PREBAN) which creates the input files for the main analysis program, and Flexibility Enhanced Rolling Element Bearing Analysis (FEREBA), the main analysis program. This report addresses input instructions for and features of the computer codes. A companion report addresses the theoretical basis for the computer codes. REBANS extends the capabilities of the SHABERTH (Shaft and Bearing Thermal Analysis) code to include race and housing flexibility, including such effects as dead band and preload springs.

  3. Modeling of rolling element bearing mechanics. Theoretical manual

    NASA Technical Reports Server (NTRS)

    Merchant, David H.; Greenhill, Lyn M.

    1994-01-01

    This report documents the theoretical basis for the Rolling Element Bearing Analysis System (REBANS) analysis code which determines the quasistatic response to external loads or displacement of three types of high-speed rolling element bearings: angular contact ball bearings; duplex angular contact ball bearings; and cylindrical roller bearings. The model includes the effects of bearing ring and support structure flexibility. It is comprised of two main programs: the Preprocessor for Bearing Analysis (PREBAN) which creates the input files for the main analysis program; and Flexibility Enhanced Rolling Element Bearing Analysis (FEREBA), the main analysis program. A companion report addresses the input instructions for and features of the computer codes. REBANS extends the capabilities of the SHABERTH (Shaft and Bearing Thermal Analysis) code to include race and housing flexibility, including such effects as dead band and preload springs.

  4. Modeling of rolling element bearing mechanics. Computer program user's manual

    NASA Technical Reports Server (NTRS)

    Greenhill, Lyn M.; Merchant, David H.

    1994-01-01

    This report provides the user's manual for the Rolling Element Bearing Analysis System (REBANS) analysis code which determines the quasistatic response to external loads or displacement of three types of high-speed rolling element bearings: angular contact ball bearings, duplex angular contact ball bearings, and cylindrical roller bearings. The model includes the defects of bearing ring and support structure flexibility. It is comprised of two main programs: the Preprocessor for Bearing Analysis (PREBAN) which creates the input files for the main analysis program, and Flexibility Enhanced Rolling Element Bearing Analysis (FEREBA), the main analysis program. This report addresses input instructions for and features of the computer codes. A companion report addresses the theoretical basis for the computer codes. REBANS extends the capabilities of the SHABERTH (Shaft and Bearing Thermal Analysis) code to include race and housing flexibility, including such effects as dead band and preload springs.

  5. Bearing system

    DOEpatents

    Kapich, Davorin D.

    1987-01-01

    A bearing system includes backup bearings for supporting a rotating shaft upon failure of primary bearings. In the preferred embodiment, the backup bearings are rolling element bearings having their rolling elements disposed out of contact with their associated respective inner races during normal functioning of the primary bearings. Displacement detection sensors are provided for detecting displacement of the shaft upon failure of the primary bearings. Upon detection of the failure of the primary bearings, the rolling elements and inner races of the backup bearings are brought into mutual contact by axial displacement of the shaft.

  6. Lubricant replacement in rolling element bearings for weapon surety devices

    SciTech Connect

    Steinhoff, R.; Dugger, M.T.; Varga, K.S.

    1996-05-01

    Stronglink switches are a weapon surety device that is critical to the nuclear safety theme in modem nuclear weapons. These stronglink switches use rolling element bearings which contain a lubricant consisting of low molecular weight polytetrafluoroethylene (PTFE) fragments. Ozone-depleting solvents are used in both the manufacture and application of this lubricant. An alternate bearing lubrication for stronglink switches is needed that will provide long-term chemical stability, low migration and consistent performance. Candidates that were evaluated include bearings with sputtered MoS{sub 2} on the races and retainers, bearings with TiC-coated balls, and bearings with Si{sub 3}N{sub 4} balls and steel races. These candidates were compared to the lubricants currently used which are bearings lubricated with PTFE fragments of low molecular weight in a fluorocarbon solvent. The candidates were also compared to bearings lubricated with a diester oil which is representative of bearing lubricants used in industrial applications. Evaluation consisted of cycling preloaded bearings and subjecting them to 23 gRMS random vibration. All of the candidates are viable substitutes for low load application where bearing preload is approximately 1 pound. For high load applications where the bearing preload is approximately 10 pounds, bearings with sputtered MoS{sub 2} on the races and retainers appear to be the best substitutes. Bearings with TiC-coated balls also appear to be a viable candidate but these bearings did not perform as well as the sputtered MoS{sub 2}.

  7. Ball Lightning Investigations

    NASA Astrophysics Data System (ADS)

    Bychkov, V. L.; Nikitin, A. I.; Dijkhuis, G. C.

    Ball lightning (BL) researches' review and theoretical models of three different authors are presented. The general review covers investigations from 1838 until the present day, and includes a discussion on observation data, experimental modeling, and theoretical approaches. Section 6.1 is written by Bychkov and Nikitin; authors of the sections 6.2, 6.3 and 6.4 are, respectively, Bychkov, Nikitin and Dijkhuis.

  8. Atmospheric Tar Balls: Particles from Biomass and Biofuel Burning

    NASA Technical Reports Server (NTRS)

    Posfai, Mihaly; Gelencser, Andras; Simonics, Renata; Arato, Krisztina; Li, Jia; Hobbs, Peter V.; Buseck, Peter R.

    2004-01-01

    Tar balls are amorphous, carbonaceous spherules that occur in the tropospheric aerosol as a result of biomass and biofuel burning. They form a distinct group of particles with diameters typically between 30 and 500 nm and readily identifiable with electron microscopy. Their lack of a turbostratic microstructure distinguishes them from soot, and their morphology and composition (approximately 90 mol% carbon) renders them distinct from other carbonaceous particles. Tar balls are particularly abundant in slightly aged (minutes to hours old) biomass smoke, indicating that they likely form by gas-to-particle conversion within smoke plumes. The material of tar balls is initially hygroscopic; however, the particles become largely insoluble as a result of free radical polymerization of their organic molecules. Consequently, tar balls are primarily externally mixed with other particle types, and they do not appreciably increase in size during aging. When tar balls coagulate with water-bearing particles, their material may partly dissolve and no longer be recognizable as distinct particles. Tar balls may contain organic compounds that absorb sunlight. They are an important, previously unrecognized type of carbonaceous (organic) atmospheric particle.

  9. Water ball collision

    NASA Technical Reports Server (NTRS)

    Fujimoto, K.

    1986-01-01

    What happens if a stainless steel ball hits a water ball in the weightless space ot the Universe? In other words, it was the objective of our experiments in the Space to observe the surface tension of liquid by means of making a solid collide with a liquid. Place a small volume of water between 2 glass sheets to make a thin water membrane: the 2 glass sheets cannot be separated unless an enormous force is applied. It is obvious from this phenomenom that the surface tension of water is far greater than presumed. On Earth, however, it is impossible in most cases to observe only the surface tension of liquid, because gravity always acts on the surface tension. Water and stainless steel balls were chosen the liquid and solids for the experiments. Because water is the liquid most familiar to us, its properties are well known. And it is also of great interest to compare its properties on the Earth with those in the weightless space.

  10. Development of a high speed parallel hybrid boost bearing

    NASA Technical Reports Server (NTRS)

    Winn, L. W.; Eusepi, M. W.

    1973-01-01

    The analysis, design, and testing of the hybrid boost bearing are discussed. The hybrid boost bearing consists of a fluid film bearing coupled in parallel with a rolling element bearing. This coupling arrangement makes use of the inherent advantages of both the fluid film and rolling element bearing and at the same time minimizes their disadvantages and limitations. The analytical optimization studies that lead to the final fluid film bearing design are reported. The bearing consisted of a centrifugally-pressurized planar fluid film thrust bearing with oil feed through the shaft center. An analysis of the test ball bearing is also presented. The experimental determination of the hybrid bearing characteristics obtained on the basis of individual bearing component tests and a combined hybrid bearing assembly is discussed and compared to the analytically determined performance characteristics.

  11. Physics in a Glitter Ball

    ERIC Educational Resources Information Center

    Trikosko, Walter

    2011-01-01

    Maui Toys' Water Bouncer (Fig. 1) is a water-filled ball containing glitter. Buy one and put it on your desk and students can't keep their hands off of it. Pitch the ball in the air giving it a quick spin. When you catch it you will see a sparkling vortex. Twist the ball around different ways and the angular momentum of the fluid keeps the axis of…

  12. Rolling-element fatigue life of silicon nitride balls. [as compared to that of steel, ceramic, and cermet materials

    NASA Technical Reports Server (NTRS)

    Parker, R. J.; Zaretsky, E. V.

    1974-01-01

    The five-ball fatigue tester was used to evaluate silicon nitride as a rolling-element bearing material. Results indicate that hot-pressed silicon nitride running against steel may be expected to yield fatigue lives comparable to or greater than those of bearing quality steel running against steel at stress levels typical rolling-element bearing application. The fatigue life of hot-pressed silicon nitride is considerably greater than that of any ceramic or cermet tested. Computer analysis indicates that there is no improvement in the lives of 120-mm-bore angular--contact ball bearings of the same geometry operating at DN values from 2 to 4 million where hot-pressed silicon nitride balls are used in place of steel balls.

  13. Current Status of Hybrid Bearing Damage Detection

    NASA Technical Reports Server (NTRS)

    Dempsey, Paula J.; Certo, Joseph M.; Morales, Wilfredo

    2004-01-01

    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. Since 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.

  14. PEPC LRU: Ball Support Assembly

    SciTech Connect

    Alger, T

    1999-05-14

    The PEPC LRU upper ball support assembly consists of a ball and a pneumatic air cylinder/conical seat latching mechanism to be attached to the optics support frame,and a ball attached to the PEPC LRU. Both components are designed to allow manual positioning in three axes. Upon insertion of the PEPC LRU into the structure, the upper pneumatic cylinder is actuated to latch the two assemblies together through the conical seat device to grab the lower ball to support the LRU weight. To be conservative, the design load for the assembly is 1500 pounds (the prototype PEPC LRU weight was measured to be near 1380 pounds).

  15. The "Policy Cycle": A Ball by Ball Account.

    ERIC Educational Resources Information Center

    Hatcher, Richard; Troyna, Barry

    1994-01-01

    Concerned with Stephen Ball's theoretical and empirical contribution to contemporary "education policy sociology," this article examines the efficacy of his theoretical eclecticism, highlighting incompatibilities in his interpretation and application of certain social and political theorists. Ball's representation of the policy cycle, as applied…

  16. Small, high-speed bearing technology for cryogenic turbo-pumps

    NASA Technical Reports Server (NTRS)

    Winn, L. W.; Eusepi, M. W.; Smalley, A. J.

    1974-01-01

    The design of 20-mm bore ball bearings is described for cryogenic turbo-machinery applications, operating up to speeds of 120,000 rpm. A special section is included on the design of hybrid bearings. Each hybrid bearing is composed of a ball bearing in series with a conventional pressurized fluid-film journal bearing. Full details are presented on the design of a test vehicle which possesses the capability of testing the above named bearings within the given speed range under externally applied radial and axial loads.

  17. Holy Balls!: Part Deux

    NASA Astrophysics Data System (ADS)

    Belden, Jesse; Jandron, Michael; Truscott, Tadd

    2012-11-01

    A Waboba® (WAter BOuncing BAll) demonstrates remarkable water skipping behavior, even at relatively large impact angles. The highly compliant nature of these elastic spheres results in significant deformation into a disk-like shape upon impact. The increased wetted area and force coefficient generates a large hydrodynamic force that more readily lifts the ball off the water surface. However, elasticity introduces some surprising phenomena, such as material waves that propagate on the sphere and interact with the water cavity. Depending upon impact conditions, material waves may propagate in various directions combining to create multiple modes of deformation and complicated fluid-structure interactions. Furthermore, the timescales of deformation and wave propagation depend on the material properties and impact conditions. In this talk, we will discuss skipping regimes in terms of impact parameters and material properties and relate failed skipping behavior to the structure-fluid interaction caused by deformation. The critical timescales for deformation, wave propagation and collision will be related to the relevant physical parameters of the problem.

  18. Atmospheric Ball Plasma Interactions

    NASA Astrophysics Data System (ADS)

    Wurden, C. J. V.; Wurden, G. A.

    2008-11-01

    Free-floating atmospheric pressure copper hydroxyl ball plasmas have been studied in air and helium atmospheres, using still and high speed photography (up to 20,000 fps), collimated photodiodes, and spectroscopy. A fine boundary layer between the greenish Cu-OH cloud, and the air, is orange in color. However, when the discharge is initiated into a helium atmosphere, the boundary layer is no longer visible, suggesting that the visible boundary was caused by interactions with oxygen. We have studied scaling of the 10-cm diameter ball plasmas with both the size of the water bucket, and the applied discharge voltage, over the range of 500-5000 volts. When looking at the initial spider-leg breakdown above the water surface, the ratio of H-alpha to H-beta lines suggests a temperature of ˜0.3 eV. This is also consistent with the presence of molecular lines of OH, and perhaps CuOH2 in the rising cloud. The cloud is affected by, but can penetrate through an aluminum window screen mesh.

  19. AX-5 space suit bearing torque investigation

    NASA Technical Reports Server (NTRS)

    Loewenthal, Stuart; Vykukal, Vic; Mackendrick, Robert; Culbertson, Philip, Jr.

    1990-01-01

    The symptoms and eventual resolution of a torque increase problem occurring with ball bearings in the joints of the AX-5 space suit are described. Starting torques that rose 5 to 10 times initial levels were observed in crew evaluation tests of the suit in a zero-g water tank. This bearing problem was identified as a blocking torque anomaly, observed previously in oscillatory gimbal bearings. A large matrix of lubricants, ball separator designs and materials were evaluated. None of these combinations showed sufficient tolerance to lubricant washout when repeatedly cycled in water. The problem was resolved by retrofitting a pressure compensated, water exclusion seal to the outboard side of the bearing cavity. The symptoms and possible remedies to blocking are discussed.

  20. Lubrication for high load duplex bearings

    SciTech Connect

    Steinhoff, R.G.

    1997-08-01

    Three ES and H-compatible lubricants (Environment, Safety and Health) for high load duplex bearing applications were evaluated and compared against trichlorotrifluoroethane (Freon) deposition of low molecular weight polytetrafluoroethylene (PTFE) bearing lubricant extracted from Vydax{trademark}. Vydax is a product manufactured by DuPont consisting of various molecular weights of PTFE suspended in trichlorotrifluoroethane (Freon) which is an ozone-depleting solvent. Bearings with Supercritical CO{sub 2} deposition of PTFE extracted from Vydax AR/IPA, bearings with titanium carbide coated balls, and bearings with diamond-like carbon races and retainers were evaluated. Bearings with Supercritical CO{sub 2} deposition of PTFE from Vydax AR/IPA performed as well as bearings with Freon deposition of PTFE from Freon-based Vydax.

  1. Pratt and Whitney cryogenic turbopump bearing experience

    NASA Technical Reports Server (NTRS)

    Poole, W. E.; Bursey, R. W., Jr.

    1988-01-01

    Successful, reusable bearings require lubrication, traditionally, a transfer film from sacrificial cage wear. Early testing included materials screening programs to identify suitable cryogenic cage materials. A specially developed element tester that simulated the function of a ball bearing cage was used. Suitable materials must provide lubrication with an acceptably low wear rate, without abrading contacting surfaces. The most promising materials were tested in full scale bearings at speeds up to 4 MDN. Teflon, filled with 40 percent bronze powder, was the best performing material. A variety of bearings were designed and successfully tested in LH2 and LOX. Bearings with bronze filled Teflon cages were successfully tested for 150 hrs. In overload tests, the same design was tested for 5 hrs at maximum Hertz stresses above 450 ksi and an additional 5 hrs with a maximum Hertz stress exceeding 500 ksi. Four bearings were tested in LOX for 25 hrs, with a maximum time per bearing of 10 hrs.

  2. Behaviour of a Bouncing Ball

    ERIC Educational Resources Information Center

    Cross, Rod

    2015-01-01

    The bounce of a ball is a seemingly innocuous event that can be used to illustrate many aspects of elementary and even advanced mechanics. Both normal and oblique bounces on a rigid surface are considered in this article, emphasizing qualitative features of the bounce process. If the ball bounces at an oblique angle then it can slide throughout…

  3. Marshall Space Flight Center High Speed Turbopump Bearing Test Rig

    NASA Technical Reports Server (NTRS)

    Gibson, Howard; Moore, Chip; Thom, Robert

    2000-01-01

    The Marshall Space Flight Center has a unique test rig that is used to test and develop rolling element bearings used in high-speed cryogenic turbopumps. The tester is unique in that it uses liquid hydrogen as the coolant for the bearings. This test rig can simulate speeds and loads experienced in the Space Shuttle Main Engine turbopumps. With internal modifications, the tester can be used for evaluating fluid film, hydrostatic, and foil bearing designs. At the present time, the test rig is configured to run two ball bearings or a ball and roller bearing, both with a hydrostatic bearing. The rig is being used to evaluate the lifetimes of hybrid bearings with silicon nitride rolling elements and steel races.

  4. Development and Evaluation of Titanium Spacesuit Bearings

    NASA Technical Reports Server (NTRS)

    Rhodes, Richard; Battisti, Brian; Ytuarte, Raymond, Jr.; Schultz, Bradley

    2016-01-01

    The Z-2 Prototype Planetary Extravehicular Space Suit Assembly is a continuation of NASA's Z-series of spacesuits, designed with the intent of meeting a wide variety of exploration mission objectives, including human exploration of the Martian surface. Incorporating titanium bearings into the Z-series space suit architecture allows us to reduce mass by an estimated 23 lbs per suit system compared to the previously used stainless steel bearing race designs, without compromising suit functionality. There are two obstacles to overcome when using titanium for a bearing race- 1) titanium is flammable when exposed to the oxygen wetted environment inside the space suit and 2) titanium's poor wear properties are often challenging to overcome in tribology applications. In order to evaluate the ignitability of a titanium space suit bearing, a series of tests were conducted at White Sands Test Facility (WSTF) that introduced the bearings to an extreme test profile, with multiple failures imbedded into the test bearings. The testing showed no signs of ignition in the most extreme test cases; however, substantial wear of the bearing races was observed. In order to design a bearing that can last an entire exploration mission (approx. 3 years), design parameters for maximum contact stress need to be identified. To identify these design parameters, bearing test rigs were developed that allow for the quick evaluation of various bearing ball loads, ball diameters, lubricants, and surface treatments. This test data will allow designers to minimize the titanium bearing mass for a specific material and lubricant combination and design around a cycle life requirement for an exploration mission. This paper reviews the current research and testing that has been performed on titanium bearing races to evaluate the use of such materials in an enriched oxygen environment and to optimize the bearing assembly mass and tribological properties to accommodate for the high bearing cycle life for an

  5. Structure of laboratory ball lightning.

    PubMed

    Ito, Tsuyohito; Tamura, Tomoya; Cappelli, Mark A; Hamaguchi, Satoshi

    2009-12-01

    Trajectories of self-sustained laboratory ball lightning, generated by arc discharges with silicon, are investigated for understanding the possibility of buoyant flight. Extremely low apparent densities are found, nearly approaching that of standard air. The freely buoyant balls are observed to survive for about 0.1 s, with significantly buoyant balls surviving for several seconds. These ball lightning objects are found to have a density and size that can easily allow them to be carried by a gentle breeze of a few meters per second. The results are interpreted by a model that is an extension of that first proposed by Abrahamson and Dinniss [J. Abrahamson and J. Dinniss, Nature (London) 403, 519 (2000)]. The buoyant behavior of ball lightning seen in our experiments is believed to arise as a result of the formation of a nanoparticle oxide network growing from a molten silicon core.

  6. Structure of laboratory ball lightning

    NASA Astrophysics Data System (ADS)

    Ito, Tsuyohito; Tamura, Tomoya; Cappelli, Mark A.; Hamaguchi, Satoshi

    2009-12-01

    Trajectories of self-sustained laboratory ball lightning, generated by arc discharges with silicon, are investigated for understanding the possibility of buoyant flight. Extremely low apparent densities are found, nearly approaching that of standard air. The freely buoyant balls are observed to survive for about 0.1 s, with significantly buoyant balls surviving for several seconds. These ball lightning objects are found to have a density and size that can easily allow them to be carried by a gentle breeze of a few meters per second. The results are interpreted by a model that is an extension of that first proposed by Abrahamson and Dinniss [J. Abrahamson and J. Dinniss, Nature (London) 403, 519 (2000)]. The buoyant behavior of ball lightning seen in our experiments is believed to arise as a result of the formation of a nanoparticle oxide network growing from a molten silicon core.

  7. Reflections on a Bouncing Ball

    NASA Astrophysics Data System (ADS)

    Rohr, Jim; Lopez, Veronica; Rohr, Tyler

    2014-12-01

    While observing the bounce heights of various kinds of sports balls dropped from different heights onto a variety of surfaces, we thought of the following question: Could measurements of drop and bounce heights of balls of different diameters, but of the same material, falling from different heights, but on the same surface, be expressed by a simple mathematical formula? Our objective was to provide a simple classroom ball-drop experiment that produced robust and interesting data sets from which students could address this question. With a suitable choice of variables, all the ball drop data could be collapsed to a single curve, so that given the mass and drop height of the ball, the bounce height could be reasonably estimated (±10% of measured values).

  8. Structure of laboratory ball lightning.

    PubMed

    Ito, Tsuyohito; Tamura, Tomoya; Cappelli, Mark A; Hamaguchi, Satoshi

    2009-12-01

    Trajectories of self-sustained laboratory ball lightning, generated by arc discharges with silicon, are investigated for understanding the possibility of buoyant flight. Extremely low apparent densities are found, nearly approaching that of standard air. The freely buoyant balls are observed to survive for about 0.1 s, with significantly buoyant balls surviving for several seconds. These ball lightning objects are found to have a density and size that can easily allow them to be carried by a gentle breeze of a few meters per second. The results are interpreted by a model that is an extension of that first proposed by Abrahamson and Dinniss [J. Abrahamson and J. Dinniss, Nature (London) 403, 519 (2000)]. The buoyant behavior of ball lightning seen in our experiments is believed to arise as a result of the formation of a nanoparticle oxide network growing from a molten silicon core. PMID:20365306

  9. Computing Operating Characteristics Of Bearing/Shaft Systems

    NASA Technical Reports Server (NTRS)

    Moore, James D.

    1996-01-01

    SHABERTH computer program predicts operating characteristics of bearings in multibearing load-support system. Lubricated and nonlubricated bearings modeled. Calculates loads, torques, temperatures, and fatigue lives of ball and/or roller bearings on single shaft. Provides for analysis of reaction of system to termination of supply of lubricant to bearings and other lubricated mechanical elements. Valuable in design and analysis of shaft/bearing systems. Two versions of SHABERTH available. Cray version (LEW-14860), "Computing Thermal Performances Of Shafts and Bearings". IBM PC version (MFS-28818), written for IBM PC-series and compatible computers running MS-DOS.

  10. THRUST BEARING

    DOEpatents

    Heller, P.R.

    1958-09-16

    A thrust bearing suitable for use with a rotor or blower that is to rotate about a vertical axis is descrihed. A centrifagal jack is provided so thnt the device may opernte on one hearing at starting and lower speeds, and transfer the load to another bearing at higher speeds. A low viscosity fluid is used to lubricate the higher speed operation bearing, in connection with broad hearing -surfaces, the ability to withstand great loads, and a relatively high friction loss, as contraated to the lower speed operatio;n bearing which will withstand only light thrust loads but is sufficiently frictionfree to avoid bearing seizure during slow speed or startup operation. An axially aligned shaft pin provides the bearing surface for low rotational speeds, but at higher speed, weights operating against spring tension withdraw nthe shaft pin into the bearing proper and the rotor shaft comes in contact with the large bearing surfaces.

  11. The ISOLDE Silicon Ball

    SciTech Connect

    Fraile, L.M.

    2003-09-16

    The investigation of weakly bound nuclei close to the particle driplines makes necessary the development of new spectroscopy devices with the capability of detecting charged particles and precisely determining their energy, angular distribution and nature. With this aim the ISOLDE Silicon Ball is under construction. It is a charged particle spectroscopy device with the requirements of high geometrical efficiency and broad energy range coverage, designed for the investigation of the exotic nuclei produced at ISOLDE and at other similar facilities. In order to allow for particle identification the simultaneous use of the Time of Flight (TOF) and Pulse Shape Discrimination (PSD) techniques is intended. Recoil tagging capabilities, suitable for transfer reactions to be performed at REX-ISOLDE, should be foreseen for a future development. The design and realization of the first prototype, together with the first tests are reported.

  12. Cracked cue ball

    NASA Astrophysics Data System (ADS)

    Carlowicz, Michael

    The latest images sent by the Galileo spacecraft reveal that the surface of Jupiter's moon Europa may have contained a layer of “warm ice” or even liquid water. In fact, planetologists are wondering if perhaps it still does.Photos taken earlier this summer show Europa to have a crust of smooth white and brown-tinted ice scarred by long, jagged cracks; some scientists have said the moon looks like a cracked cue ball. “The scale of fracture patterns—extending a distance equivalent to the width of the western United States—dwarf the San Andreas fault in length and width,” said Ronald Greeley, a geologist from Arizona State University and a member of the Galileo imaging team. The cracks are believed to have been caused by the stress of tidal forces created by Jupiter's gravity. Warmth generated by tidal heating also may have been sufficient to soften or liquefy some of the ice.

  13. Ceramic bearings. (Latest citations from the Aerospace database). Published Search

    SciTech Connect

    1995-05-01

    The bibliography contains citations concerning the design, fabrication, and evaluation of ceramic bearings. Citations discuss roller, ball, fuel-lubricated, and dry-lubricated bearings. Applications in machinery, automobiles, rails, and air transport are examined. References to surface hardness, wear, and fatigue tests are presented. (Contains a minimum of 125 citations and includes a subject term index and title list.)

  14. Bearing tester data compilation analysis, and reporting and bearing math modeling

    NASA Technical Reports Server (NTRS)

    Cody, J. C.

    1986-01-01

    Integration of heat transfer coefficients, modified to account for local vapor quality, into the 45 mm bearing model has been completed. The model has been evaluated with two flow rates and subcooled and saturated coolant. The evaluation showed that by increasing the flow from 3.6 to 7.0 lbs/sec the average ball temperature was decreased by 102 F, using a coolant temperature of -230 F. The average ball temperature was decreased by 63 F by decreasing the inlet coolant temperature from saturated to -230 F at a flow rate of 7.0 lbs/sec. Since other factors such as friction, cage heating, etc., affect bearing temperatures, the above bearing temperature effects should be considered as trends and not absolute values. The two phase heat transfer modification has been installed in the 57 mm bearing model and the effects on bearing temperatures have been evaluated. The average ball temperature was decreased by 60 F by increasing the flow rate from 4.6 to 9.0 lbs/sec for the subcooled case. By decreasing the inlet coolant temperature from saturation to -24 F, the average ball temperature was decreased 57 F for a flow rate of 9.0 lbs/sec. The technique of relating the two phase heat transfer coefficient to local vapor quality will be applied to the tester model and compared with test data.

  15. Unsolved Mystery of Ball Lightning

    NASA Astrophysics Data System (ADS)

    Bychkov, V. L.

    Ball lightning is an unusual phenomenon always drawing attention of people. There are still questions about its origination, features, interaction with environment, and phenomena related to it. On a way of studying this phenomenon, there are a lot of difficulties, the basic of them is insufficiency of authentic, scientific data. The chapter sets as the purpose to interest the reader in the problem, to describe conditions of ball lightning occurrence, theories, and its hypotheses explanation, to include readers in a circle of experimental searches in creation of a ball lightning and its analogues, and to describe fascination of a problem and difficulty of its solution.

  16. Journal bearing

    DOEpatents

    Menke, John R.; Boeker, Gilbert F.

    1976-05-11

    1. An improved journal bearing comprising in combination a non-rotatable cylindrical bearing member having a first bearing surface, a rotatable cylindrical bearing member having a confronting second bearing surface having a plurality of bearing elements, a source of lubricant adjacent said bearing elements for supplying lubricant thereto, each bearing element consisting of a pair of elongated relatively shallowly depressed surfaces lying in a cylindrical surface co-axial with the non-depressed surface and diverging from one another in the direction of rotation and obliquely arranged with respect to the axis of rotation of said rotatable member to cause a flow of lubricant longitudinally along said depressed surfaces from their distal ends toward their proximal ends as said bearing members are rotated relative to one another, each depressed surface subtending a radial angle of less than 360.degree., and means for rotating said rotatable bearing member to cause the lubricant to flow across and along said depressed surfaces, the flow of lubricant being impeded by the non-depressed portions of said second bearing surface to cause an increase in the lubricant pressure.

  17. Rolling bearing stiffness in arbitrary direction

    NASA Astrophysics Data System (ADS)

    Luo, Zhusan; Sun, Xinde; Wu, Linfeng

    1992-06-01

    This paper presents a new concept of rolling bearing stiffness in arbitrary direction, which is necessary to the investigation of rotor-bearing dynamics. It includes the axial stiffness and the arbitrary radial stiffness of the rolling bearing. Based on elasticity theory and the geometrical parameters of the bearing, the approximate formulas of the axial stiffness, the arbitrary radial stiffness, and the inner ring displacements are derived. Furthermore, the paper also discusses the effects of the loads, the radial clearance, and the load distribution parameters on the rolling bearing stiffness. In order to verify the model and the computer program, an example of a ball bearing is analyzed in detail. It shows that the model and the program are reliable and the results are consistent with the data supplied by the U.S. Air Force Aeropropulsion Laboratory.

  18. The coefficient of restitution for collisions of happy balls, unhappy balls, and tennis balls

    NASA Astrophysics Data System (ADS)

    Cross, Rod

    2000-11-01

    A perfectly happy ball is one that bounces to its original height when dropped on a massive, rigid surface. A completely unhappy ball does not bounce at all. In the former case, the coefficient of restitution (COR) is unity. In the latter case, the COR is zero. It is shown that when an unhappy ball collides with a happy ball, the COR increases from zero to unity as the stiffness of the happy ball decreases from infinity to zero. The COR is independent of the mass of each ball. The implication of reducing the COR of a tennis ball, as a possible means of slowing the serve in tennis, is also considered. It is shown that (a) the COR for a collision with a racket varies with the impact point and is a maximum at the vibration node near the center of the strings, and (b) the serve speed is reduced by only about 20% if the COR for a bounce on the court is reduced to zero.

  19. ES and H-compatible lubrication for duplex bearings

    SciTech Connect

    Steinhoff, R.G.

    1997-10-01

    Two ES and H-compatible lubricants (environment, safety, and health) for duplex bearing applications and one hybrid material duplex bearing were evaluated and compared against duplex bearings with trichlorotrifluoroethane (Freon) deposition of low molecular weight polytetrafluoroethylene (PTFE) bearing lubricant extracted from Vydax{trademark}. Vydax is a product manufactured by DuPont consisting of various molecular weights of PTFE suspended in trichlorotrifluoroethane (Freon), which is an ozone-depleting solvent. Vydax has been used as a bearing lubricant in strong link mechanisms since 1974. Hybrid duplex bearings with silicon nitride balls and molded glass-nylon-Teflon retainers, duplex bearings lubricated with sputtered MoS{sub 2} on races and retainers, and duplex bearings lubricated with electrophoretic deposited MoS{sub 2} were evaluated. Bearings with electrophoretic deposited MoS{sub 2} performed as well as bearings with Freon deposition of PTFE from Freon-based Vydax. Hybrid bearings with silicon nitride balls performed worse than bearings lubricated with Vydax, but their performance would still be acceptable for most applications. Bearings lubricated with sputtered MoS{sub 2} on the races and retainers had varying amounts of film on the bearings. This affected the performance of the bearings. Bearings with a uniform coating performed to acceptable levels, but bearings with no visible MoS{sub 2} on the races and retainers did not perform as well as bearings with the other coatings. Unless process controls are incorporated in the sputtering process or the bearings are screened, they do not appear to be acceptable for duplex bearing applications.

  20. Enhancing the Bounce of a Ball

    ERIC Educational Resources Information Center

    Cross, Rod

    2010-01-01

    In sports such as baseball, softball, golf, and tennis, a common objective is to hit the ball as fast or as far as possible. Another common objective is to hit the ball so that it spins as fast as possible, since the trajectory of the ball through the air is strongly affected by ball spin. In an attempt to enhance both the coefficient of…

  1. Behaviour of a bouncing ball

    NASA Astrophysics Data System (ADS)

    Cross, Rod

    2015-05-01

    The bounce of a ball is a seemingly innocuous event that can be used to illustrate many aspects of elementary and even advanced mechanics. Both normal and oblique bounces on a rigid surface are considered in this article, emphasizing qualitative features of the bounce process. If the ball bounces at an oblique angle then it can slide throughout the bounce, or just at the start of the bounce, and may even slide backwards at the end of the bounce. A ball can also grip the surface after a short sliding phase, or it can grip right from the start. When the ball grips, static friction rather than sliding friction determines the rebound speed, spin and angle.

  2. Space Shuttle Orbital Maneuvering Subsystem (OMS) Engine Propellant Leakage Ball-Valve Shaft Seals

    NASA Technical Reports Server (NTRS)

    Lueders, Kathy; Buntain, Nick; Fries, Joseph (Technical Monitor)

    1999-01-01

    Evidence of propellant leakage across ball-valve shaft seals has been noted during the disassembly of five flight engines and one test engine at the NASA Lyndon B. Johnson Space Center, White Sands Test Facility. Based on data collected during the disassembly of these five engines, the consequences of propellant leakage across the ball-valve shaft seals can be divided into four primary areas of concern: Damage to the ball-valve pinion shafts, damage to sleeved bearings inside the ball-valve and actuator assemblies, degradation of the synthetic rubber o-rings used in the actuator assemblies, and corrosion and degradation to the interior of the actuator assemblies. The exact time at which leakage across the ball-valve shaft seals occurs has not been determined, however, the leakage most likely occurs during engine firings when, depending on the specification used, ball-valve cavity pressures range as high as 453 to 550 psia. This potential pressure range for the ball-valve cavities greatly exceeds the acceptance leakage test pressure of 332 psia. Since redesign and replacement of the ball-valve shaft seals is unlikely, the near term solution to prevent damage that occurs from shaft-seal leakage is to implement a routine overhaul and maintenance program for engines in the fleet. Recommended repair, verification, and possible preventative maintenance measures are discussed in the paper.

  3. MODIFIED BALL AND SOCKET COUPLING

    DOEpatents

    Kalen, D.D.

    1961-05-23

    A ball and socket coupling arrangement is described in which the male and female members may be engaged or disengaged without visual aid. The female member has an internal spherical seat through which slots are provided to accommodate appropriately arranged and shaped ribs in the ball member. After engagement of the members, one or both are rotated to lock them together to prevent accidental disengagement. (AEC)

  4. Modified Ball and Socket Coupling

    DOEpatents

    Conley, Jr, W. R.; Pitman, R. W.

    1961-05-23

    A ball and socket coupling arrangement is given in which the male and female members may be engaged or disengaged without visual aid. The female member has an internal spherical seat through which slots are provided to accommodate appropriately arranged and shaped ribs in the male ball member. After engagement of the members, one or both are rotated to lock them together to prevent accidental disengagement.

  5. Ball-joint grounding ring

    NASA Technical Reports Server (NTRS)

    Aperlo, P. J. A.; Buck, P. A.; Weldon, V. A.

    1981-01-01

    In ball and socket joint where electrical insulator such as polytetrafluoroethylene is used as line to minimize friction, good electrical contact across joint may be needed for lightning protection or to prevent static-charge build-up. Electrical contact is maintained by ring of spring-loaded fingers mounted in socket. It may be useful in industry for cranes, trailers, and other applications requiring ball and socket joint.

  6. Development of fracture resistant, multilayer films for precision ball bearings

    NASA Astrophysics Data System (ADS)

    Hopple, G. B.; Keem, J. E.; Loewenthal, S. H.

    1993-04-01

    Attention is given to an exhaustive hardness characterization and a comparative evaluation of the dry wear performance of three different wear-resistant coating systems, namely, alumina-titania, WC-Co, and Ni-Cr on a normalized steel substrate, mated against normalized carbon steel in a pin-on-disk tribometer. Data obtained revealed that the plasma-sprayed alumina-titania coating was the hardest of the three coatings, followed by the high velocity oxy-fuel (HVOF) WC-Co coating with the HVOF NiCr-based coating the least hard. A pin-on-disk tribometer showed that the WC-Co coating has the highest wear resistance, followed by the alumina titania coating and the NiCr coating. The average dynamic friction coefficients were in the range 0.1-0.4.

  7. Determination of the SSME high pressure oxidizer turbopump bearing temperature

    NASA Technical Reports Server (NTRS)

    Naerheim, Y.; Stocker, P. J.; Lumsden, J. B.

    1988-01-01

    The SSME high pressure liquid oxygen turbopump (HPOTP) bearings sometimes wear and experience heating and oxidation of the ball and raceway surfaces. So far it has been impossible to measure the temperature of the bearings directly during operation of the turbopumps. However, a method was developed for determining the surface temperature of the bearings from the composition of the oxides using oxidation samples for calibration and Auger Electron Spectroscopy (AES) for chemical analysis.

  8. Grizzly bear

    USGS Publications Warehouse

    Schwartz, C.C.; Miller, S.D.; Haroldson, M.A.; Feldhamer, G.; Thompson, B.; Chapman, J.

    2003-01-01

    The grizzly bear inspires fear, awe, and respect in humans to a degree unmatched by any other North American wild mammal. Like other bear species, it can inflict serious injury and death on humans and sometimes does. Unlike the polar bear (Ursus maritimus) of the sparsely inhabited northern arctic, however, grizzly bears still live in areas visited by crowds of people, where presence of the grizzly remains physically real and emotionally dominant. A hike in the wilderness that includes grizzly bears is different from a stroll in a forest from which grizzly bears have been purged; nighttime conversations around the campfire and dreams in the tent reflect the presence of the great bear. Contributing to the aura of the grizzly bear is the mixture of myth and reality about its ferocity. unpredictable disposition, large size, strength, huge canines, long claws, keen senses, swiftness, and playfulness. They share characteristics with humans such as generalist life history strategies. extended periods of maternal care, and omnivorous diets. These factors capture the human imagination in ways distinct from other North American mammals. Precontact Native American legends reflected the same fascination with the grizzly bear as modern stories and legends (Rockwell 1991).

  9. SSME Long-life Bearings

    NASA Technical Reports Server (NTRS)

    Butner, M. F.; Murphy, B. T.

    1986-01-01

    Hybrid hydrostatic/ball bearings for LH2 and LO2 service in turbopumps were studied as a means of improving speed and life capabilities. Four hybrid bearing configurations were designed with emphasis on achieving maximum stiffness and damping. Parallel load bearings were tested at steady-state and transient conditions with LH2 (externally fed) and LN2 (internally fed). The hydrostatic elements were tested with Freon 113 for empirical determination of dynamic characteristics. Tests using an eccentric journal for loading showed the externally and internally fed hydrostatic bearings to have significant separated coefficients of direct stiffness and damping. For the internally fed bearing, the strongly speed-dependent cross-coupling stiffness arising from fluid swirl, along with significant cross-coupling damping, resulted in low net effective stiffness and damping. The test method used can produce separated coefficients with a sufficiently elliptic journal orbit; otherwise, only net effective coefficients combining direct and cross-coupling terms can be determined. Testing with nonsynchronous excitation is recommended to avoid this restriction. Investigation of hard materials, including ceramics, is recommended as a means of eliminating the need for the rolling bearing for startup and shutdown support. The testing was performed in 1984 (LH2), 1985 (LN2) and 1985-86 (Freon).

  10. A. Palmgren Revisited: A Basis for Bearing Life Prediction

    NASA Technical Reports Server (NTRS)

    Zaretsky, Erwin V.

    1997-01-01

    Bearing technology, as well as the bearing industry, began to develop with the invention of the bicycle in the 1850's. At the same time, high-quality steel was made possible by the Bessemer process. In 1881, H. Hertz published his contact stress analysis. By 1902, R. Stribeck had published his work based on Hertz theory to calculate the maximum load of a radially loaded ball bearing. By 1920, all of the rolling bearing types used today were being manufactured. AISI 52100 bearing steel became the material of choice for these bearings. Beginning in 1918, engineers directed their attention to predicting the lives of these bearings. In 1924, A. Palmgren published a paper outlining his approach to bearing life prediction. This paper was the basis for the Lundberg-Palmgren life theory published in 1947. A critical review of the 1924 Palmgren paper is presented here together with a discussion of its effect on bearing life prediction.

  11. Study of methods for applying and enhancing transfer film coatings of polytetrafluoroethylene (PTEE) to Space Shuttle Main Engine (SSME) High Pressure Oxygen Turbo Pump (HPOTP) bearings

    NASA Technical Reports Server (NTRS)

    Kannel, J. W.; Dufrane, K. F.; Zugaro, F. F.

    1981-01-01

    Machines were constructed and evaluated for burnishing polytetrafluoroethylene on balls for use in the high pressure oxygen turbopump (HPOTP). The most positive performance was obtained with single-ball burnishing, but one technique for burnishing three balls simultaneously holds promise. Evaluations of the coatings in a HPOTP bearing of earlier design (employed smaller diameter balls) showed very little life enhancement before high torque and ball and race wear initiated. Other coating techniques, such as molybdenum disulfide combined with PTFE transfer films, hold promise for providing the more durable quantities of solid lubricant needed for the bearings.

  12. Polar Bear

    USGS Publications Warehouse

    Amstrup, S.D.; ,; Lentfer, J.W.

    1988-01-01

    Polar bears are long-lived, late-maturing carnivores that have relatively low rates of reproduction and natural mortality. Their populations are susceptible to disturbance from human activities, such as the exploration and development of mineral resources or hunting. Polar bear populations have been an important renewable resource available to coastal communities throughout the Arctic for thousands of years.

  13. Enhancing the Bounce of a Ball

    NASA Astrophysics Data System (ADS)

    Cross, Rod

    2010-10-01

    In sports such as baseball, softball, golf, and tennis, a common objective is to hit the ball as fast or as far as possible. Another common objective is to hit the ball so that it spins as fast as possible, since the trajectory of the ball through the air is strongly affected by ball spin. In an attempt to enhance both the coefficient of restitution (COR) and the spin of a golf ball, I conducted several experiments to see what would happen when a 45-g, 42.8-mm diameter golf ball bounced on: (a) a 58-mm diameter, 103-g Super Ball®; (b) an 8-mm thick, 56-mm diameter circular disk of Super Ball material cut from a large Super Ball and glued to a 3.4-kg lead brick; and (c) a 3-mm thick sheet of rubber glued to a 3.4-kg lead brick. (See Fig. 1.)

  14. Turbocharger bearing retention and lubrication system

    SciTech Connect

    Gutknecht, D.A.

    1991-12-31

    This patent describes exhausts gas driven turbocharger. It comprises a housing, a shaft within the housing having a longitudinal axis of rotation and a pair of ends, a compressor wheel mounted within the housing on one end of the shaft for rotation therewith, a turbine wheel mounted within the housing on the other end of the shaft for rotation therewith, means for communicating air to the compressor wheel, means for communicating exhaust gas to the turbine wheel to cause the latter to rotate the shaft and the compressor wheel mounted thereon to compress the air communicated to the compressor wheel, and bearing means mounting the shaft for rotation relative to the housing, the bearing means including a bearing outer ring, a bearing inner ring, and ball bearing elements supporting the bearing outer ring on the bearing inner ring, a bearing locating aperture in the bearing outer ring, and an elongated bearing location pin having a longitudinal axis of symmetry extending transversely to the longitudinal axis of the shaft.

  15. MIPP Plastic Ball electronics upgrade

    SciTech Connect

    Baldin, Boris; /Fermilab

    2009-01-01

    An upgrade electronics design for Plastic Ball detector is described. The Plastic Ball detector was a part of several experiments in the past and its back portion (proposed to be used in MIPP) consists of 340 photomultipliers equipped with a sandwich scintillator. The scintillator sandwich has fast and slow signal component with decay times 10 ns and 1 {micro}s respectively. The upgraded MIPP experiment will collect up to 12,000 events during each 4 second spill and read them out in {approx}50 seconds between spills. The MIPP data acquisition system will employ deadtime-less concept successfully implemented in Muon Electronics of Dzero experiment at Fermilab. An 8-channel prototype design of the Plastic Ball Front End (PBFE) implementing these requirements is discussed. Details of the schematic design, simulation and prototype test results are discussed.

  16. Dynamics of a bouncing ball

    NASA Astrophysics Data System (ADS)

    Chastaing, J.-Y.; Bertin, E.; Géminard, J.-C.

    2015-06-01

    We describe an experiment dedicated to the study of the trajectories of a ball bouncing on a vibrating plate. Using an experimental device of our own design, it is possible to impose arbitrary trajectories on the plate and we show that the entire trajectory of the ball can be reconstructed solely from measurement of the times the ball hits the plate. In this paper, we make use of our apparatus to introduce the notion of dissipative collisions and to propose three different ways to measure the associated restitution coefficient. We then report on correlations in the chaotic regime and theoretically discuss the complex patterns that are exhibited in the case of a sinusoidal vibration. Lastly, we show that the use of an aperiodic driving vibration makes it possible to minimize part of these correlations.

  17. Bearing endurance tests in vacuum for sputtered molybdenum disulfide films

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1975-01-01

    Angular-contact, 440C stainless steel, ball bearings with sputtered MoS2 films 0.0000006 x 10-7m (6000 A) thick were evaluated in a vacuum bearing chamber (1750 rpm, 137.9-N- (31-lbf-) thrust load) for endurance. Two types of sputtered films were evaluated: (1) MOS2 sputtered directly onto bearing components, and (2) a thin 0.0000001 x 10-7m (1000 A) underlayer of Cr3Si2 subsequently sputtered with MoS2. Bearing test evaluations in vacuum showed that endurance lives of more than 1000 hours (105,000,000 cycles) were obtained with bearings (cage, races, and balls) directly sputtered with MoS2. The same endurance lives were also obtained when only the races and cage were sputtered with an underlayer of Cr3Si2 and subsequently with MoS2.

  18. Transmission Bearing Damage Detection Using Decision Fusion Analysis

    NASA Technical Reports Server (NTRS)

    Dempsey, Paula J.; Lewicki, David G.; Decker, Harry J.

    2004-01-01

    A diagnostic tool was developed for detecting fatigue damage to rolling element bearings in an OH-58 main rotor transmission. Two different monitoring technologies, oil debris analysis and vibration, were integrated using data fusion into a health monitoring system for detecting bearing surface fatigue pitting damage. This integrated system showed improved detection and decision-making capabilities as compared to using individual monitoring technologies. This diagnostic tool was evaluated by collecting vibration and oil debris data from tests performed in the NASA Glenn 500 hp Helicopter Transmission Test Stand. Data was collected during experiments performed in this test rig when two unanticipated bearing failures occurred. Results show that combining the vibration and oil debris measurement technologies improves the detection of pitting damage on spiral bevel gears duplex ball bearings and spiral bevel pinion triplex ball bearings in a main rotor transmission.

  19. Imaging characteristics of ball lens

    NASA Astrophysics Data System (ADS)

    Li, Qinghui; Shao, Xiaopeng

    2014-05-01

    In most digital imaging applications, high-resolution imaging or videos are usually desired for later processing and analysis. The desire for high-resolution stems from two principal application areas: improvement of pictorial information for human interpretation, and helping representation for automatic machine preception. While the image sensors limit the spatial resolution of the image, the image details are also limited by the optical system, due to diffraction, and aberration1. Monocentric lens are an attractive option for gigapixel camera because the symmetrical design focuses light identically coming from any direction. Marks and Brady proposed a monocentric lens design imaging 40 gigapixels with an f-number of 2.5 and resolving 2 arcsec over a 120 degrees field of view2. Recently, Cossairt, Miau, and Nayer proposed a proof-of-concept gigapixel computational camera consisting of a large ball lens shared by several small planar sensors coupled with a deblurring step3. The design consists of a ball element resulting in a lens that is both inexpensive to produce and easy to align. Because the resolution of spherical lens is fundamentally limited by geometric aberrations, the imaging characteristics of the ball lens is expressed by the geometrical aberrations, in which the general equations for the primary aberration of the ball lens are given. The effect of shifting the stop position on the aberrations of a ball lens is discussed. The variation of the axial chromatic aberration with the Abbe V-number when the refraction index takes different values is analyzed. The variation of the third-order spherical aberration ,the fifth-order spherical aberration and the spherical aberration obtained directly from ray tracing with the f-number is discussed. The other imaging evaluation merits, such as the spot diagram, the modulation transfer function(MTF) and the encircled energy are also described. Most of the analysis of the ball lens is carried out using OSLO optics

  20. Magnetic Bearing

    NASA Technical Reports Server (NTRS)

    1996-01-01

    AVCON, Inc. produces advanced magnetic bearing systems for industrial use, offering a unique technological approach based on contract work done at Marshall Space Flight Center and Lewis Research Center. Designed for the turbopump of the Space Shuttle main engine, they are now used in applications such as electric power generation, petroleum refining, machine tool operation and natural gas pipelines. Magnetic bearings support moving machinery without physical contact; AVCON's homopolar approach is a hybrid of permanent and electromagnets which are one-third the weight, smaller and more power- efficient than previous magnetic bearings.

  1. Ball lightning risk to aircraft

    NASA Astrophysics Data System (ADS)

    Doe, R.; Keul, A.

    2009-04-01

    Lightning is a rare but regular phenomenon for air traffic. Aircraft are designed to withstand lightning strikes. Research on lightning and aircraft can be called detailed and effective. In the last 57 years, 18 reported lightning aviation disasters with a fatality figure of at least 714 persons occurred. For comparison, the last JACDEC ten-year average fatality figure was 857. The majority encountered lightning in the climb, descent, approach and/or landing phase. Ball lightning, a metastable, rare lightning type, is also seen from and even within aircraft, but former research only reported individual incidents and did not generate a more detailed picture to ascertain whether it constitutes a significant threat to passenger and aircraft safety. Lacking established incident report channels, observations were often only passed on as "air-travel lore". In an effort to change this unsatisfactory condition, the authors have collected a first international dataset of 38 documented ball lightning aircraft incidents from 1938 to 2001 involving 13 reports over Europe, 13 over USA/Canada, and 7 over Russia. 18 (47%) reported ball lightning outside the aircraft, 18 (47%) inside, 2 cases lacked data. 8 objects caused minor damage, 8 major damage (total: 42%), only one a crash. No damage was reported in 18 cases. 3 objects caused minor crew injury. In most cases, ball lightning lasted several seconds. 11 (29%) incidents ended with an explosion of the object. A cloud-aircraft lightning flash was seen in only 9 cases (24%) of the data set. From the detailed accounts of air personnel in the last 70 years, it is evident that ball lightning is rarely, but consistently observed in connection with aircraft and can also occur inside the airframe. Reports often came from multiple professional witnesses and in several cases, damages were investigated by civil or military authorities. Although ball lightning is no main air traffic risk, the authors suggest that incident and accident

  2. Billiard-ball echo model

    NASA Astrophysics Data System (ADS)

    Beach, R.; Hartmann, S. R.; Friedberg, R.

    1982-05-01

    Photon echoes in gaseous media are explained with the use of a simple heuristic model in which the atoms behave like composite billiard balls. The laser providing the excitation pulses becomes an atom smasher which "splits" the atoms and then by judicious programming puts them back together again. The most general photon-echo reordering process is explained without recourse to formal analysis so that an intuitive feeling is obtained which works equally well for the ordinary two-pulse photon echo, the Raman echo, the trilevel echo, the grating echo, etc. A formal analysis of the billiard-ball echo model is presented in its support.

  3. Rotordynamics and bearing design of turbochargers

    NASA Astrophysics Data System (ADS)

    Chen, Wen Jeng

    2012-05-01

    Turbochargers have gained significant attention in recent years. They are already widely used in automotive, locomotive, and marine applications with diesel engines. They are also applied in the aerospace application to increase the engine performance now. The turbochargers used in automotive and aerospace industry are very light-weight with operating speeds above 100,000 rpm. The turbochargers used in locomotive and marine applications are relatively heavy in size and power compared to the automotive and aerospace applications, and the maximum continuous operating speeds are around 30,000 rpm depending on the diesel engine power rating. Floating ring bushings, semi-floating dampers, ball bearings, and ball bearings with dampers are commonly used in automotive applications for small turbochargers. However, these bearings may not be appropriate for large turbochargers in locomotive and marine applications. Instead, multi-lobed bearings with and without squeeze film dampers are commonly used in these heavy-duty turbochargers. This paper deals with the rotordynamic characteristics of larger turbochargers in locomotive and marine applications. Various bearing designs are discussed. Bearing design parameters are studied and optimal values are suggested. Test results are also presented to support the analytical simulation.

  4. Estimation of bearing contact angle in-situ by X-ray kinematography

    NASA Technical Reports Server (NTRS)

    Fowler, P. H.; Manders, F.

    1982-01-01

    The mounted, preloaded contact angle of the structural bearings in the assembled design mechanical assembly was measured. A modification of the Turns method is presented, based upon the clarity and definition of moving parts achieved with X-ray technique and cinematic display. Contact angle is estimated by counting the number of bearings passing a given point as a function of number of turns of the shaft. Ball and pitch diameter variations are discussed. Ball train and shaft angle uncertainties are also discussed.

  5. High pressure oxygen turbopump bearing cage stability analyses. [space shuttle main engine

    NASA Technical Reports Server (NTRS)

    Merriman, T. L.; Kannel, J. W.

    1984-01-01

    The low service life of the high pressure oxygen turbopump (HPOTP) bearings used in the space shuttle main engine was examined by use of the Battelle "BASDAP' bearing computer stability model. The dynamic instability of the bearing cage resulted in excessive wear and eventual failure of the unit. By maintaining a cage/race clearance of no more than 0.25 millimeters (0.010 inches), ball/pocket clearance of no less than 0.54 millimeters (0.025 inches), dynamic balancing of the cages, and maintaining adequate lubricant films between the balls and races, cage instability and subsequent bearing degradation can be reduced.

  6. 2012 Problem 15: Frustrating Golf Ball

    NASA Astrophysics Data System (ADS)

    Huang, Shan; Zhu, Zheyuan; Gao, Wenli; Wang, Sihui

    2015-10-01

    This paper studies the condition for a golf ball to escape from a hole. The two determining factors are the ball's initial velocity v0 and its deviation from the center of the hole d. There is a critical escaping velocity vc for every deviation d. The ball's motion is analyzed by calculating the change of velocity whenever the ball collides with the hole. The critical conditions predicted by our theory are verified through experiment.

  7. Vertical bounce of two vertically aligned balls

    NASA Astrophysics Data System (ADS)

    Cross, Rod

    2007-11-01

    When a tennis ball rests on top of a basketball and both drop to the floor together, the tennis ball is projected vertically at high speed. A mass-spring model of the impact, as well as air track data, suggest that the tennis ball should be projected at relatively low speed. Measurements of the forces on each ball and the bounce of vertically aligned superballs are used to resolve the discrepancy.

  8. Does Ease to Block a Ball Affect Perceived Ball Speed? Examination of Alternative Hypotheses

    ERIC Educational Resources Information Center

    Witt, Jessica K.; Sugovic, Mila

    2012-01-01

    According to an action-specific account of perception, the perceived speed of a ball can be a function of the ease to block the ball. Balls that are easier to stop look like they are moving slower than balls that are more difficult to stop. This was recently demonstrated with a modified version of the classic computer game Pong (Witt & Sugovic,…

  9. Secrets of the Crystal Ball

    ERIC Educational Resources Information Center

    Croucher, John S.

    2007-01-01

    This article describes how a crystal ball known as "The Flash Mind Reader" is played. "The Flash Mind Reader" is a mathematics game in which the player is invited to select any-two digit number and then subtract the sum of these two digits from the original number. A chart is provided in which the (adjusted) number they obtained will have a symbol…

  10. Laboratory-produced ball lightning

    NASA Astrophysics Data System (ADS)

    Golka, Robert K., Jr.

    1994-05-01

    For 25 years I have actively been searching for the true nature of ball lightning and attempting to reproduce it at will in the laboratory. As one might expect, many unidentified lights in the atmosphere have been called ball lightning, including Texas Maffa lights (automobile headlights), flying saucers (UFOs), swamp gas in Ann Arbor, Michigan, etc. For 15 years I thought ball lightning was strictly a high-voltage phenomenon. It was not until 1984 when I was short-circuiting the electrical output of a diesel electric railroad locomotive that I realized that the phenomenon was related more to a high current. Although I am hoping for some other types of ball lightning to emerge such as strictly electrostatic-electromagnetic manifestations, I have been unlucky in finding laboratory provable evidence. Cavity-formed plasmodes can be made by putting a 2-inch burning candle in a home kitchen microwave oven. The plasmodes float around for as long as the microwave energy is present.

  11. Idea Bank: Wiffle Ball Physics

    ERIC Educational Resources Information Center

    Lancor, Rachael

    2009-01-01

    Projectile motion, a cornerstone topic of introductory physics, is usually a student's first exposure to the problem-solving techniques used in this subject. Often, this is an inactive learning experience--students work with pencil and paper to read and solve projectile motion problems (e.g., diagrams and descriptions of balls being hit, kicked,…

  12. The Efficiency of Small Bearings in Instruments of the Type Used in Aircraft

    NASA Technical Reports Server (NTRS)

    Norton, F H

    1921-01-01

    This report deals with the construction and properties of bearings and pivots for use in instruments. The static and running friction for both thrust and radial loads was determined for a number of conical pivots and cylindrical and ball bearings. The static rocking friction was also measured for several conical and ball bearings under a heavy load, especially to determine their suitability for use in N. P. L. (National Physical Laboratory) type wind tunnel balance. In constructing conical pivots and sockets it was found that the pivots should be hardened and highly polished, preferably with a revolving lap, and that the sockets should be made by punching with a hardened and polished punch. It was found that for a light load the conical pivots give less friction than any other type, and their wearing qualities when hardened are excellent. Very small ball bearings are unsatisfactory because the proportional accuracy of the balls and races is not high enough to insure smooth running. For rocking pivots under heavy loads it was found that a ball-and-socket bearing, consisting of a hemispherical socket and a sphere of smaller diameter concentric with it, with a row of small balls resting between the two, was superior to a pivot resting in a socket. It was found that vibration such as occurs in an airplane will greatly reduce the static friction of a pivot or bearing, in some cases to as little as one-twentieth of its static value.

  13. Playing Ball in a Space Station

    ERIC Educational Resources Information Center

    Simoson, Andrew J.

    2006-01-01

    How does artificial gravity affect the path of a thrown ball? This paper contrasts ball trajectories on the Little Prince's asteroid planet B-612 and Arthur C. Clarke's rotating-drum spacecraft of 2001, and demonstrates curve balls with multiple loops in the latter environment.

  14. Seismic bearing

    NASA Astrophysics Data System (ADS)

    Power, Dennis

    2009-05-01

    Textron Systems (Textron) has been using geophones for target detection for many years. This sensing capability was utilized for detection and classification purposes only. Recently Textron has been evaluating multiaxis geophones to calculate bearings and track targets more specifically personnel. This capability will not only aid the system in locating personnel in bearing space or cartesian space but also enhance detection and reduce false alarms. Textron has been involved in the testing and evaluation of several sensors at multiple sites. One of the challenges of calculating seismic bearing is an adequate signal to noise ratio. The sensor signal to noise ratio is a function of sensor coupling to the ground, seismic propagation and range to target. The goals of testing at multiple sites are to gain a good understanding of the maximum and minimum ranges for bearing and detection and to exploit that information to tailor sensor system emplacement to achieve desired performance. Test sites include 10A Site Devens, MA, McKenna Airfield Ft. Benning, GA and Yuma Proving Ground Yuma, AZ. Geophone sensors evaluated include a 28 Hz triax spike, a 15 Hz triax spike and a hybrid triax spike consisting of a 10 Hz vertical geophone and two 28 Hz horizontal geophones. The algorithm uses raw seismic data to calculate the bearings. All evaluated sensors have triaxial geophone configuration mounted to a spike housing/fixture. The suite of sensors also compares various types of geophones to evaluate benefits in lower bandwidth. The data products of these tests include raw geophone signals, seismic features, seismic bearings, seismic detection and GPS position truth data. The analyses produce Probability of Detection vs range, bearing accuracy vs range, and seismic feature level vs range. These analysis products are compared across test sites and sensor types.

  15. Wind Turbine Design Guideline DG03: Yaw and Pitch Rolling Bearing Life

    SciTech Connect

    Harris, T.; Rumbarger, J. H.; Butterfield, C. P.

    2009-12-01

    This report describes the design criteria, calculation methods, and applicable standards recommended for use in performance and life analyses of ball and roller (rolling) bearings for yaw and pitch motion support in wind turbine applications. The formulae presented here for rolling bearing analytical methods and bearing-life ratings are consistent with methods in current use by wind turbine designers and rolling-bearing manufacturers.

  16. Software Developed for Analyzing High- Speed Rolling-Element Bearings

    NASA Technical Reports Server (NTRS)

    Fleming, David P.

    2005-01-01

    COBRA-AHS (Computer Optimized Ball & Roller Bearing Analysis--Advanced High Speed, J.V. Poplawski & Associates, Bethlehem, PA) is used for the design and analysis of rolling element bearings operating at high speeds under complex mechanical and thermal loading. The code estimates bearing fatigue life by calculating three-dimensional subsurface stress fields developed within the bearing raceways. It provides a state-of-the-art interactive design environment for bearing engineers within a single easy-to-use design-analysis package. The code analyzes flexible or rigid shaft systems containing up to five bearings acted upon by radial, thrust, and moment loads in 5 degrees of freedom. Bearing types include high-speed ball, cylindrical roller, and tapered roller bearings. COBRA-AHS is the first major upgrade in 30 years of such commercially available bearing software. The upgrade was developed under a Small Business Innovation Research contract from the NASA Glenn Research Center, and incorporates the results of 30 years of NASA and industry bearing research and technology.

  17. Evaluation of bearing mounting design and excessive wear phenomena

    NASA Technical Reports Server (NTRS)

    Kannel, J. W.

    1982-01-01

    The effect of bearing thermal growth on the effectiveness of the bearing preload springs on the space shuttle main engine high pressure oxygen turbopump (SSME HPTOP) were examined. The SSME HPTOP turbine end bearings, preload spring, and bearing mounting design were evaluated relative to spalling, excessive ball wear, possible thermal problems, and cage delamination. The magnitude of the thermal stresses required to cause high levels of ball wear were calculated. Plots of maximum sheer stress and maximum reversing shear versus the axial load for the 57 mm SSME HPTOP bearing were created. A plot of the bearing thermal growth versus preload spring deflection was generated. It was determined that metallic wear, rather than thermal growth, caused enlargement of the contact zone between ball and races, that high fatigue-inducing shear stresses are generated under increased loads, and that at temperatures between 100 and 150 deg C, the springs bottom out and very high loads are developed in the bearing. Allowance for adequate spring movement after assembly is recommended.

  18. How to catch a cricket ball.

    PubMed

    Dienes, Z; McLeod, P

    1993-01-01

    A cricket or baseball fielder can run so as to arrive at just the right place at just the right time to catch a ball. It is shown that if the fielder runs so that d2(tan alpha)/dt2 = 0, where alpha is the angle of elevation of gaze from fielder to ball, then the ball will generally be intercepted before it hits the ground. This is true whatever the aerodynamic drag experienced by the ball. The only exception is if the ball is not approaching the fielder before he starts to run.

  19. Fate of thermal log type Q balls

    SciTech Connect

    Chiba, Takeshi; Kamada, Kohei; Kasuya, Shinta; Yamaguchi, Masahide

    2010-11-15

    We study time evolution of the Q ball in thermal logarithmic potential using lattice simulations. As the temperature decreases due to the cosmic expansion, the thermal logarithmic term in the potential is eventually overcome by a mass term, and we confirm that the Q ball transforms from the thick-wall type to the thin-wall type for a positive coefficient of radiative corrections to the mass term, as recently suggested. Moreover, we find that the Q ball finally ''melts down'' when the Q-ball solution disappears. We also discuss the effects of this phenomenon on the detectability of gravitational waves from the Q-ball formation.

  20. Design and fabrication of prototype system for early warning of impending bearing failure

    NASA Technical Reports Server (NTRS)

    Broderick, J. J.; Burchill, R. F.; Clark, H. L.

    1972-01-01

    Ball bearing performance tests run on several identical ball bearings under a variety of load, speed, temperature, and lubrication conditions are reported. Bearing temperature, torque, vibration, noise, strain, cage speed, etc., were monitored to establish those measurements most suitable as indicators of ball bearing health. Tape records were made under steady-state conditions of a variety of speeds and loads. Sample sections were selected for narrowband spectral analysis with a real time analyzer. An artificial flow was created across the inner race surface of one bearing using an acid etch technique to produce the scratch. Tape records obtained before and after established a characteristic frequency response that identifies the presence of the flow. The signals found most useful as indicators of performance degradation were ultrasonic outputs.

  1. Development and Evaluation of Titanium Space Suit Bearings

    NASA Technical Reports Server (NTRS)

    Rhodes, Richard; Battisti, Brian; Ytuarte, Ray, Jr.; Schultz, Bradley

    2016-01-01

    The Z-2 Prototype Planetary Extravehicular Space Suit Assembly is a continuation of NASA's Z series of spacesuits, designed with the intent of meeting a wide variety of exploration mission objectives, including human exploration of the Martian surface. Incorporating titanium bearings into the Z series space suit architecture allows us to reduce mass by an estimated 23 pounds per suit system compared to the previously used stainless steel bearing designs without compromising suit functionality. There are two obstacles to overcome when using titanium for a bearing race: 1) titanium is flammable when exposed to the oxygen wetted environment inside the space suit and 2) titanium's poor wear properties are often challenging to overcome in tribology applications. In order to evaluate the ignitability of a titanium space suit bearing, a series of tests were conducted at White Sands Test Facility that introduced the bearings to an extreme test profile, with multiple failures imbedded into the test bearings. The testing showed no signs of ignition in the most extreme test cases; however, substantial wear of the bearing races was observed. In order to design a bearing that can last an entire exploration mission (approximately 2 years), bearing test rigs were developed that allow for the quick evaluation of various bearing ball loads, ball diameters, lubricants, and surface treatments. This test data will allow designers to minimize the titanium bearing mass for a specific material and lubricant combination around a maximum contact stress that will allow the bearing to survive the life of an exploration mission. This paper reviews the current research and testing that has been performed on titanium bearing races to evaluate the use of such materials in an enriched oxygen environment and to optimize the bearing assembly mass and tribological properties to accommodate for the high bearing cycle life for an exploration mission.

  2. Bearing tester data compilation, analysis and reporting and bearing math modeling, volume 1

    NASA Technical Reports Server (NTRS)

    Marshall, D. D.; Montgomery, E. E.; New, L. S.; Stone, M. A.; Tiller, B. K.

    1984-01-01

    Thermal and mechanical models of high speed angular contact ball bearings operating in LOX and LN2 were developed and verified with limited test data in an effort to further understand the parameters that determine or effect the SSME turbopump bearing operational characteristics and service life. The SHABERTH bearing analysis program which was adapted to evaluate shaft bearing systems in cryogenics is not capable of accommodating varying thermal properties and two phase flow. A bearing model with this capability was developed using the SINDA thermal analyzer. Iteration between the SHABERTH and the SINDA models enable the establishment of preliminary bounds for stable operation in LN2. These limits were established in terms of fluid flow, fluid inlet temperature, and axial load for a shaft speed of 30,000 RPM.

  3. Modeling of rolling element bearing mechanics

    NASA Technical Reports Server (NTRS)

    Greenhill, L. M.

    1991-01-01

    Roller element bearings provide the primary mechanical interface between rotating and nonrotating components in the high performance turbomachinery of the Space Shuttle Main Engine (SSME). Knowledge of bearing behavior under various loading and environmental conditions is essential to predicting and understanding the overall behavior of turbopumps, including rotordynamic stability, critical speeds and bearing life. The objective is to develop mathematical models and computer programs to describe the mechanical behavior of ball and cylinder roller bearings under the loading and environmental conditions encountered in the SSME and future high performance rocket engines. This includes characteristics such as nonlinear load/motion relationships, stiffness and damping, rolling element loads for life prediction, and roller and cage stability.

  4. Evaluation of SSME high pressure liquid oxygen turbopump bearings

    NASA Technical Reports Server (NTRS)

    Dufrane, K. F.; Kannel, J. W.

    1979-01-01

    Examination of the bearings produced conclusive evidence that a very high axial load was applied to bearing 8517903 during a significant portion of the service time. The high loads caused serious ball and race wear and surface fatigue pitting. In all likelihood, continued operation of this bearing with the high axial load would have caused increasing deterioration and catastrophic failure. In contrast, bearing 8517900 showed much less deterioration and probably had experienced only the axial loads deliberately applied by the preload spring. Bearing 8517900 represents the best-case operation with the loads controlled to the levels intended in the design. Fatigue life calculations on bearing 8517903 with an axial load of 27,000 N showed the intolerance of the bearing to such load levels.

  5. Polymer-composite ball lightning.

    PubMed

    Bychkov, V L

    2002-01-15

    Investigations into the state of ball lightning (BL) have been made, and both theory and experiments, related to so-called "polymer-composite" ball lightning, are presented. The properties of such a polymeric BL have been described and are that of a long-lived object capable of storing high energy. Results of experiments, starting with polymeric components in erosive gas discharge experiments, are described and discussed. The model of BL as a highly charged polymer-dielectric structure is described. According to this model BL appears as the result of the aggregation of natural polymers, such as lignin and cellulose, soot, polymeric silica and other natural dust particles. Its ability to glow is explained by the appearance over its perimeter of gas discharges near the highly charged BL surface, and electrical breakdown of some regions on the surface, consisting of polymerized and aggregated threads.

  6. Polymer-composite ball lightning.

    PubMed

    Bychkov, V L

    2002-01-15

    Investigations into the state of ball lightning (BL) have been made, and both theory and experiments, related to so-called "polymer-composite" ball lightning, are presented. The properties of such a polymeric BL have been described and are that of a long-lived object capable of storing high energy. Results of experiments, starting with polymeric components in erosive gas discharge experiments, are described and discussed. The model of BL as a highly charged polymer-dielectric structure is described. According to this model BL appears as the result of the aggregation of natural polymers, such as lignin and cellulose, soot, polymeric silica and other natural dust particles. Its ability to glow is explained by the appearance over its perimeter of gas discharges near the highly charged BL surface, and electrical breakdown of some regions on the surface, consisting of polymerized and aggregated threads. PMID:16210170

  7. Vapor phase lubrication of high-temperature bearings

    NASA Astrophysics Data System (ADS)

    Graham, E. E.; Nesarikar, Abhijit; Forster, Nelson; Givan, Garry

    1993-09-01

    Results are presented of an experimental investigation in which a ball-on-rod tester was modified to allow tricresylphosphate (TCP) to be vaporized into a carrier gas of air and delivered into the bottom section of the rolling contact tester operated at 3200 rpm. Tests were conducted using M50 rods and M50 balls at a pressure of 3.86 GPa and a temperature of 350 C and with silicon nitride rods and balls at a contact pressure of 5.13 GPa and temperatures of 350 and 680 C. A vaporized stream of 0.5 percent TCP was used to lubricate the rod and balls for test times from 90 min to 8 hr, and a mild polishing occurred on the active bearing surfaces. SEM photographs of the vapor-lubricated surface showed a distinct tenacious deposit on the ball cage, rod, and balls. These results indicate that vapor phase lubrication can be used for high pressure bearing contacts, providing effective lubrication for temperatures up to at least 680 C.

  8. Keeping your eyes continuously on the ball while running for catchable and uncatchable fly balls.

    PubMed

    Postma, Dees B W; den Otter, A Rob; Zaal, Frank T J M

    2014-01-01

    When faced with a fly ball approaching along the sagittal plane, fielders need information for the control of their running to the interception location. This information could be available in the initial part of the ball trajectory, such that the interception location can be predicted from its initial conditions. Alternatively, such predictive information is not available, and running to the interception location involves continuous visual guidance. The latter type of control would predict that fielders keep looking at the approaching ball for most of its flight, whereas the former type of control would fit with looking at the ball during the early part of the ball's flight; keeping the eyes on the ball during the remainder of its trajectory would not be necessary when the interception location can be inferred from the first part of the ball trajectory. The present contribution studied visual tracking of approaching fly balls. Participants were equipped with a mobile eye tracker. They were confronted with tennis balls approaching from about 20 m, and projected in such a way that some balls were catchable and others were not. In all situations, participants almost exclusively tracked the ball with their gaze until just before the catch or until they indicated that a ball was uncatchable. This continuous tracking of the ball, even when running close to their maximum speeds, suggests that participants employed continuous visual control rather than running to an interception location known from looking at the early part of the ball flight. PMID:24670972

  9. Keeping Your Eyes Continuously on the Ball While Running for Catchable and Uncatchable Fly Balls

    PubMed Central

    Postma, Dees B. W.; den Otter, A. Rob; Zaal, Frank T. J. M.

    2014-01-01

    When faced with a fly ball approaching along the sagittal plane, fielders need information for the control of their running to the interception location. This information could be available in the initial part of the ball trajectory, such that the interception location can be predicted from its initial conditions. Alternatively, such predictive information is not available, and running to the interception location involves continuous visual guidance. The latter type of control would predict that fielders keep looking at the approaching ball for most of its flight, whereas the former type of control would fit with looking at the ball during the early part of the ball's flight; keeping the eyes on the ball during the remainder of its trajectory would not be necessary when the interception location can be inferred from the first part of the ball trajectory. The present contribution studied visual tracking of approaching fly balls. Participants were equipped with a mobile eye tracker. They were confronted with tennis balls approaching from about 20 m, and projected in such a way that some balls were catchable and others were not. In all situations, participants almost exclusively tracked the ball with their gaze until just before the catch or until they indicated that a ball was uncatchable. This continuous tracking of the ball, even when running close to their maximum speeds, suggests that participants employed continuous visual control rather than running to an interception location known from looking at the early part of the ball flight. PMID:24670972

  10. How to create ball lightning

    NASA Technical Reports Server (NTRS)

    Golka, Robert K., Jr.

    1991-01-01

    Procedures are given on how to produce ball lightning. Necessary equipment includes a transformer of 150,000 watts capable of providing approximately 10,000 amperes at 15 volts, 60 cycles; thick one inch cables of stranded wire leading into a 3 by 4 by 1 foot plastic tank; a quarter inch thick 4 by 6 inch aluminum plate to be used as one of the discharge electrodes; and another electrode of heavy copper wire with the insulation stripped back 6 inches.

  11. Falling Sticks and Falling Balls

    NASA Astrophysics Data System (ADS)

    Bacon, M. E.; Harpst, Michael R.; Nakazawa, Ryohei

    2002-09-01

    The behavior of a falling stick, pivoted at one end, and a ball released from the same height as the end of the stick, is investigated theoretically and experimentally. The study is made possible through the use of the computer to perform the numerical computations and analysis of the experimental data. The study provides undergraduates with an opportunity to carry out a relatively simple project with interesting results.

  12. Replacement bearing for Rocketdyne SSME HPOTPs using alternate self-lubricating retainer materials

    NASA Technical Reports Server (NTRS)

    Gleeson, J.; Dufrane, K.; Kannel, J.

    1992-01-01

    Research was conducted to develop replacement bearings for the Rocketdyne Space Shuttle main engine (SSME) high pressure oxidizer turbopumps (HPOTPs). The replacement bearings consisted of standard balls and races with a special Battelle Self-Lubricating Insert Configuration (BASIC) retainer. The BASIC retainer consists of a phosphor bronze housing with inserts consisting of a polytetrafluoretheylene (PTFE) and bronze compound. The PTFE contacts the balls and the land guiding surface on the outer race. A PTFE transfer film is formed on balls and races, which lubricates the critical interfaces. The BASIC retainer is a one-to-one replacement for the current Armalon retainer, but has superior lubricating properties and is stronger over the broad temperature range anticipated for the HPOTP bearings. As a part of the project 40 sets of balls and races (two sizes) and 52 BASIC retainers were shipped to NASA/MSFC.

  13. Friction in metal-on-metal total disc arthroplasty: effect of ball radius.

    PubMed

    Moghadas, Parshia; Mahomed, Aziza; Hukins, David W L; Shepherd, Duncan E T

    2012-02-01

    Total disc arthroplasty (TDA) can be used to replace a degenerated intervertebral disc in the spine. There are different designs of prosthetic discs, but one of the most common is a ball-and-socket combination. Contact between the bearing surfaces can result in high frictional torque, which can then result in wear and implant loosening. This study was designed to determine the effects of ball radius on friction. Generic models of metal-on-metal TDA were manufactured with ball radii of 10, 12, 14 and 16 mm, with a radial clearance of 0.015 mm. A simulator was used to test each sample in flexion-extension, lateral bending and axial rotation at frequencies of 0.25, 0.5, 0.75, 1, 1.25, 1.5, 1.75 and 2 Hz under loads of 50, 600, 1200 and 2000 N, in new born calf serum. Frictional torque was measured and Stribeck curves were plotted to illustrate the lubrication regime in each case. It was observed that implants with a smaller ball radius showed lower friction and showed boundary and mixed lubrication regimes, whereas implants with larger ball radius showed boundary lubrication only. This study suggests designing metal-on-metal TDAs with ball radius of 10 or 12 mm, in order to reduce wear and implant loosening.

  14. 2013 Problem 3: Bouncing Ball

    NASA Astrophysics Data System (ADS)

    Xiong, Bo; Du, Li; Wang, Sihui; Gao, Wenli

    2015-10-01

    In this solution, we study the rebound of a liquid-filled Ping-Pong ball after a free-fall motion. We classify the collision into "rigid-like motion" or "liquid-involved" motion. The most significant parameter is the amount of water. The rebounding height is suppressed most as the amount of water is about half of the total volume, exhibiting a typical "liquid-involved" motion. As the amount of water increases further, the rebounding height gradually recovers, and the ball becomes rigid again. We build a theoretical model to interpret the phenomenon. The model describes the formation of the flow field during the collision stage based on the momentum propagation and flux conservation of the liquid. An effective mass is introduced to describe the confinement effect on water by the sphere. Our model successfully predicts the bouncing height with respect to the amount of water. Releasing height is also an important parameter in determining the "nature of collision". As the releasing height increases, the whole system tends to become more and more "rigid". We classify the nature of collision above a certain releasing height as "rigid-like" regardless of the amount of water inside the ball.

  15. Effect of Fiber Orientation on Ball Failures Under Rolling-contact Conditions

    NASA Technical Reports Server (NTRS)

    Butler, Robert H; Bear, H Robert; Carter, Thomas L

    1957-01-01

    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.

  16. Evaluation of worn SSME low pressure liquid oxygen turbopump bearing

    NASA Technical Reports Server (NTRS)

    Dufrane, K. F.; Kannel, J. W.

    1978-01-01

    The larger of two ball bearings used to support the rotor of the low pressure liquid oxygen turbopump in each of the shuttle main engines was analyzed to identify the cause of severe internal wear. The actual operating loads were calculated along with their direction and length of time at each load based on the size and location of the race contact paths. It is suggested that the engine component design be modified to reduce bearing stress and enhance lubrication.

  17. Ball Screw Actuator Including a Stop with an Integral Guide

    NASA Technical Reports Server (NTRS)

    Wingett, Paul T. (Inventor); Perek, John (Inventor); Geck, Kellan (Inventor)

    2015-01-01

    An actuator includes a housing assembly, a ball nut, a ball screw, and a ball screw stop. The ball nut is rotationally mounted in the housing assembly, is adapted to receive an input torque, and is configured, upon receipt thereof, to rotate and supply a drive force. The ball screw is mounted within the housing assembly and extends through the ball nut. The ball screw has a first end and a second end, and is coupled to receive the drive force from the ball nut. The ball screw is configured, upon receipt of the drive force, to selectively translate between a stow position and a deploy position. The ball screw stop is mounted on the ball screw to translate therewith and is configured to at selectively engage the housing assembly while the ball screw is translating, and engage the ball nut when the ball screw is in the deploy position.

  18. Precise timing when hitting falling balls.

    PubMed

    Brenner, Eli; Driesen, Ben; Smeets, Jeroen B J

    2014-01-01

    People are extremely good at hitting falling balls with a baseball bat. Despite the ball's constant acceleration, they have been reported to time hits with a standard deviation of only about 7 ms. To examine how people achieve such precision, we compared performance when there were no added restrictions, with performance when looking with one eye, when vision was blurred, and when various parts of the ball's trajectory were hidden from view. We also examined how the size of the ball and varying the height from which it was dropped influenced temporal precision. Temporal precision did not become worse when vision was blurred, when the ball was smaller, or when balls falling from different heights were randomly interleaved. The disadvantage of closing one eye did not exceed expectations from removing one of two independent estimates. Precision was higher for slower balls, but only if the ball being slower meant that one saw it longer before the hit. It was particularly important to see the ball while swinging the bat. Together, these findings suggest that people time their hits so precisely by using the changing elevation throughout the swing to adjust the bat's movement to that of the ball. PMID:24904380

  19. Precise timing when hitting falling balls

    PubMed Central

    Brenner, Eli; Driesen, Ben; Smeets, Jeroen B. J.

    2014-01-01

    People are extremely good at hitting falling balls with a baseball bat. Despite the ball's constant acceleration, they have been reported to time hits with a standard deviation of only about 7 ms. To examine how people achieve such precision, we compared performance when there were no added restrictions, with performance when looking with one eye, when vision was blurred, and when various parts of the ball's trajectory were hidden from view. We also examined how the size of the ball and varying the height from which it was dropped influenced temporal precision. Temporal precision did not become worse when vision was blurred, when the ball was smaller, or when balls falling from different heights were randomly interleaved. The disadvantage of closing one eye did not exceed expectations from removing one of two independent estimates. Precision was higher for slower balls, but only if the ball being slower meant that one saw it longer before the hit. It was particularly important to see the ball while swinging the bat. Together, these findings suggest that people time their hits so precisely by using the changing elevation throughout the swing to adjust the bat's movement to that of the ball. PMID:24904380

  20. Precise timing when hitting falling balls.

    PubMed

    Brenner, Eli; Driesen, Ben; Smeets, Jeroen B J

    2014-01-01

    People are extremely good at hitting falling balls with a baseball bat. Despite the ball's constant acceleration, they have been reported to time hits with a standard deviation of only about 7 ms. To examine how people achieve such precision, we compared performance when there were no added restrictions, with performance when looking with one eye, when vision was blurred, and when various parts of the ball's trajectory were hidden from view. We also examined how the size of the ball and varying the height from which it was dropped influenced temporal precision. Temporal precision did not become worse when vision was blurred, when the ball was smaller, or when balls falling from different heights were randomly interleaved. The disadvantage of closing one eye did not exceed expectations from removing one of two independent estimates. Precision was higher for slower balls, but only if the ball being slower meant that one saw it longer before the hit. It was particularly important to see the ball while swinging the bat. Together, these findings suggest that people time their hits so precisely by using the changing elevation throughout the swing to adjust the bat's movement to that of the ball.

  1. Lubrication and performance of high-speed rolling-element bearings

    NASA Technical Reports Server (NTRS)

    Zaretsky, E. V.; Schuller, F. T.; Coe, H. H.

    1985-01-01

    Trends in aircraft engine operating speeds have dictated the need for rolling-element bearings capable of speeds to 3 million DN. A review of high-speed rolling-element bearing state-of-the-art performance and lubrication is presented. Through the use of under-race lubrication and bearing thermal management bearing operation can be obtained to speeds of 3 million DN. Jet lubricated ball bearings are limited to 2.5 million DN for large bore sizes and to 3 million DN for small bore sizes. Current computer programs are able to predict bearing thermal performance.

  2. Fluid Mechanics of Cricket and Tennis Balls

    NASA Astrophysics Data System (ADS)

    Mehta, Rabindra D.

    2009-11-01

    Aerodynamics plays a prominent role in defining the flight of a ball that is struck or thrown through the air in almost all ball sports. The main interest is in the fact that the ball can often deviate from its initial straight path, resulting in a curved, or sometimes an unpredictable, flight path. It is particularly fascinating that that not all the parameters that affect the flight of a ball are always under human influence. Lateral deflection in flight, commonly known as swing, swerve or curve, is well recognized in cricket and tennis. In tennis, the lateral deflection is produced by spinning the ball about an axis perpendicular to the line of flight, which gives rise to what is commonly known as the Magnus effect. It is now well recognized that the aerodynamics of sports balls are strongly dependent on the detailed development and behavior of the boundary layer on the ball's surface. A side force, which makes a ball curve through the air, can also be generated in the absence of the Magnus effect. In one of the cricket deliveries, the ball is released with the seam angled, which trips the laminar boundary layer into a turbulent state on that side. The turbulent boundary layer separates relatively late compared to the laminar layer on the other side, thereby creating a pressure difference and hence side force. The fluid mechanics of a cricket ball become very interesting at the higher Reynolds numbers and this will be discussed in detail. Of all the round sports balls, a tennis ball has the highest drag coefficient. This will be explained in terms of the contribution of the ``fuzz" drag and how that changes with Reynolds number and ball surface wear. It is particularly fascinating that, purely through historical accidents, small disturbances on the ball surface, such as the stitching on cricket balls and the felt cover on tennis balls are all about the right size to affect boundary layer transition and development in the Reynolds numbers of interest. The fluid

  3. CUSHIONED BEARING

    DOEpatents

    Rushing, F.C.

    1960-09-01

    A vibration damping device effective to dampen vibrations occurring at the several critical speeds encountered in the operation of a high-speed centrifuge is described. A self-centering bearing mechanism is used to protect both the centrifuge shaft and the damping mechanism. The damping mechanism comprises spaced-apant, movable, and stationary sleeve members arranged concentrically of a rotating shaft with a fluid maintained between the members. The movable sleeve member is connected to the shaft for radial movement therewith.

  4. Analysis of Space Station Centrifuge Rotor Bearing Systems: A Case Study

    NASA Technical Reports Server (NTRS)

    Poplawski, Joseph V.; Loewenthal, Stuart H.; Oswald, Fred B.; Zaretsky, Erwin V.; Morales, Wilfredo; Street, Kenneth W., Jr.

    2014-01-01

    A team of NASA bearing and lubrication experts was assembled to assess the risk for the rolling-element bearings used in the International Space Station (ISS) centrifuge rotor (CR) to seize or otherwise fail to survive for the required 10-year life. The CR was designed by the Japan Aerospace Exploration Agency and their subcontractor, NEC Toshiba Space Systems, Ltd. (NTSpace). The NASA team performed a design audit for the most critical rolling-element bearing systems and reviewed the lubricant selected. There is uncertainty regarding the ability of the Braycote 601 grease (Castrol Limited) to reliably provide the 10-year continuous life required without relubrication of the system. The fatigue life of the Rotor Shaft Assembly (RSA) spring loaded face-to-face mount at a 99-percent probability of survival (L1 life) for the ball bearing set was estimated at 700 million hours and the single ball bearing (Row 3) at 58 million hours. These lives satisfy the mission requirements for fatigue. Rolling-element seizure tests on the RSA and fluid slip joint bearings were found unlikely to stop the centrifuge, which can cause damage to the ISS structure. The spin motor encoder duplex angular-contact ball bearings have a hard preload and a large number of small balls have the highest risk of failure. These bearings were not tested for seizure even though they are less tolerant to debris or internal clearance reductions.

  5. Electric charge of a lightning ball

    NASA Astrophysics Data System (ADS)

    Grigor'ev, A. I.; Shiryaeva, S. O.; Petrushov, N. A.

    2016-09-01

    The electric charge of a lightning ball is found by comparing the electrohydrodynamic stabilities of a charged drop in an electrostatic suspension and a lightning ball floating in a superposition of the gravitational field and the surface electric field. It has been assumed that the electric field strength at the surface is limited by a breakdown value. For a lightning ball radius of 15 cm, its charge is estimated as several microcoulombs. Accordingly, the density of electrostatic energy accumulated in the lightning ball is on the order of one-hundredth of a joule per square centimeter. The density of the material that constitutes the lightning ball has been estimated for the case when the electric field strength at the site of its origination is several times higher than that in fine weather. The density of the lightning ball turns out to differ from that of air by only a few percents.

  6. Ball feeder for replenishing evaporator feed

    DOEpatents

    Felde, David K.; McKoon, Robert H.

    1993-01-01

    Vapor source material such as uranium, which is to be dropped into a melt in an evaporator, is made into many balls of identical diameters and placed inside a container. An elongated sloping pipe is connected to the container and leads to the evaporator such that these balls can travel sequentially therealong by gravity. A metering valve in this pipe for passing these balls one at a time is opened in response to a signal when it is ascertained by a detector that there is a ball ready to be passed. A gate in the pipe near the evaporator momentarily stops the motion of the traveling ball and is then opened to allow the ball drop into the melt at a reduced speed.

  7. Ball feeder for replenishing evaporator feed

    DOEpatents

    Felde, D.K.; McKoon, R.H.

    1993-03-23

    Vapor source material such as uranium, which is to be dropped into a melt in an evaporator, is made into many balls of identical diameters and placed inside a container. An elongated sloping pipe is connected to the container and leads to the evaporator such that these balls can travel sequentially therealong by gravity. A metering valve in this pipe for passing these balls one at a time is opened in response to a signal when it is ascertained by a detector that there is a ball ready to be passed. A gate in the pipe near the evaporator momentarily stops the motion of the traveling ball and is then opened to allow the ball drop into the melt at a reduced speed.

  8. Adiabatic invariance of oscillons/I -balls

    NASA Astrophysics Data System (ADS)

    Kawasaki, Masahiro; Takahashi, Fuminobu; Takeda, Naoyuki

    2015-11-01

    Real scalar fields are known to fragment into spatially localized and long-lived solitons called oscillons or I -balls. We prove the adiabatic invariance of the oscillons/I -balls for a potential that allows periodic motion even in the presence of non-negligible spatial gradient energy. We show that such a potential is uniquely determined to be the quadratic one with a logarithmic correction, for which the oscillons/I -balls are absolutely stable. For slightly different forms of the scalar potential dominated by the quadratic one, the oscillons/I -balls are only quasistable, because the adiabatic charge is only approximately conserved. We check the conservation of the adiabatic charge of the I -balls in numerical simulation by slowly varying the coefficient of logarithmic corrections. This unambiguously shows that the longevity of oscillons/I -balls is due to the adiabatic invariance.

  9. Tooling Converts Stock Bearings To Custom Bearings

    NASA Technical Reports Server (NTRS)

    Fleenor, E. N., Jr.

    1983-01-01

    Technique for reworking stock bearings saves time and produces helicopter-rotor bearings ground more precisely. Split tapered ring at one end of threaded bolt expands to hold inside of inner race bearing assembly; nut, at other end of bolt, adjusts amount of spring tension. Piece of hardware grasps bearing firmly without interfering with grinding operation. Operation produces bearing of higher quality than commercially available bearings.

  10. Multifractal properties of ball milling dynamics

    SciTech Connect

    Budroni, M. A. Pilosu, V.; Rustici, M.; Delogu, F.

    2014-06-15

    This work focuses on the dynamics of a ball inside the reactor of a ball mill. We show that the distribution of collisions at the reactor walls exhibits multifractal properties in a wide region of the parameter space defining the geometrical characteristics of the reactor and the collision elasticity. This feature points to the presence of restricted self-organized zones of the reactor walls where the ball preferentially collides and the mechanical energy is mainly dissipated.

  11. NEW APPROACHES: The way balls bounce

    NASA Astrophysics Data System (ADS)

    Bridge, N. James

    1998-05-01

    The bounce of a ball is a good topic for investigation at either GCSE or A-level. At King's School Canterbury pupils have experimented with both squash balls and inflatable play balls, varying the drop height, pressure and temperature and measuring the effect on bounce height, contact area and contact time. Worthwhile predictions can be made from quite simple theory and the experimental results provide ample opportunities for discussion and evaluation.

  12. Telescoping magnetic ball bar test gage

    DOEpatents

    Bryan, J.B.

    1982-03-15

    A telescoping magnetic ball bar test gage for determining the accuracy of machine tools, including robots, and those measuring machines having non-disengagable servo drives which cannot be clutched out. Two gage balls are held and separated from one another by a telescoping fixture which allows them relative radial motional freedom but not relative lateral motional freedom. The telescoping fixture comprises a parallel reed flexure unit and a rigid member. One gage ball is secured by a magnetic socket knuckle assembly which fixes its center with respect to the machine being tested. The other gage ball is secured by another magnetic socket knuckle assembly which is engaged or held by the machine in such manner that the center of that ball is directed to execute a prescribed trajectory, all points of which are equidistant from the center of the fixed gage ball. As the moving ball executes its trajectory, changes in the radial distance between the centers of the two balls caused by inaccuracies in the machine are determined or measured by a linear variable differential transformer (LVDT) assembly actuated by the parallel reed flexure unit. Measurements can be quickly and easily taken for multiple trajectories about several different fixed ball locations, thereby determining the accuracy of the machine.

  13. Telescoping magnetic ball bar test gage

    DOEpatents

    Bryan, J.B.

    1984-03-13

    A telescoping magnetic ball bar test gage for determining the accuracy of machine tools, including robots, and those measuring machines having non-disengageable servo drives which cannot be clutched out is disclosed. Two gage balls are held and separated from one another by a telescoping fixture which allows them relative radial motional freedom but not relative lateral motional freedom. The telescoping fixture comprises a parallel reed flexure unit and a rigid member. One gage ball is secured by a magnetic socket knuckle assembly which fixes its center with respect to the machine being tested. The other gage ball is secured by another magnetic socket knuckle assembly which is engaged or held by the machine in such manner that the center of that ball is directed to execute a prescribed trajectory, all points of which are equidistant from the center of the fixed gage ball. As the moving ball executes its trajectory, changes in the radial distance between the centers of the two balls caused by inaccuracies in the machine are determined or measured by a linear variable differential transformer (LVDT) assembly actuated by the parallel reed flexure unit. Measurements can be quickly and easily taken for multiple trajectories about several different fixed ball locations, thereby determining the accuracy of the machine. 3 figs.

  14. Telescoping magnetic ball bar test gage

    DOEpatents

    Bryan, James B.

    1984-01-01

    A telescoping magnetic ball bar test gage for determining the accuracy of machine tools, including robots, and those measuring machines having non-disengageable servo drives which cannot be clutched out. Two gage balls (10, 12) are held and separated from one another by a telescoping fixture which allows them relative radial motional freedom but not relative lateral motional freedom. The telescoping fixture comprises a parallel reed flexure unit (14) and a rigid member (16, 18, 20, 22, 24). One gage ball (10) is secured by a magnetic socket knuckle assembly (34) which fixes its center with respect to the machine being tested. The other gage ball (12) is secured by another magnetic socket knuckle assembly (38) which is engaged or held by the machine in such manner that the center of that ball (12) is directed to execute a prescribed trajectory, all points of which are equidistant from the center of the fixed gage ball (10). As the moving ball (12) executes its trajectory, changes in the radial distance between the centers of the two balls (10, 12) caused by inaccuracies in the machine are determined or measured by a linear variable differential transformer (LVDT) assembly (50, 52, 54, 56, 58, 60) actuated by the parallel reed flexure unit (14). Measurements can be quickly and easily taken for multiple trajectories about several different fixed ball (10) locations, thereby determining the accuracy of the machine.

  15. Analysis and experiment of random ball test

    NASA Astrophysics Data System (ADS)

    Lu, Liming; Wu, Fan; Hou, Xi; Zhang, Can

    2012-10-01

    Robert E.Parks from National Institute of Standards and Technology (NIST), America, first reported Random Ball Test (RBT), which is used to measure the absolute error of the reference surface of the interferometer. The basic course of this technology as followed: first, assemble the Random Ball in the confocal position of the interferometer system; then, measure the surface of the Random Ball and record the result; rotate the Random Ball to another position, meanwhile make sure that the Random Ball is in the confocal position all the time; In the new position, measure the surface of the Random Ball and record it again; repeat enough times as above, calculate the mean result of the measuring results, and this mean result is just the absolute error of the reference surface of the interferometer. Since 1998, other scholars have continued Robert E.Parks's research, and created a new type of the RBT. In this new technology, Random Ball is sustained by high pressure airflow, suspending in the air, and rotating around sphere center. This technology is called Dynamic Random Ball Test (DRBT), because the Random Ball is rotating during measurement. This article mainly reported the experiment study about the DRBT.

  16. Past Performance analysis of HPOTP bearings

    NASA Technical Reports Server (NTRS)

    Bhat, B. N.; Dolan, F. J.

    1982-01-01

    The past performance analysis conducted on three High Pressure Oxygen Turbopump (HPOTP) bearings from the Space Shuttle Main Engine is presented. Metallurgical analysis of failed bearing balls and races, and wear track and crack configuration analyses were carried out. In addition, one bearing was tested in laboratory at very high axial loads. The results showed that the cracks were surface initiated and propagated into subsurface locations at relatively small angles. Subsurface cracks were much more extensive than was appeared on the surface. The location of major cracks in the races corresponded to high radial loads rather than high axial loads. There was evidence to suggest that the inner races were heated to elevated temperatures. A failure scenario was developed based on the above findings. According to this scenario the HPOTP bearings are heated by a combination of high loads and high coefficient of friction (poor lubrication). Different methods of extending the HPOTP bearing life are also discussed. These include reduction of axial loads, improvements in bearing design, lubrication and cooling, and use of improved bearing materials.

  17. Effect of ball geometry on endurance limit in bending of drilled balls

    NASA Technical Reports Server (NTRS)

    Munson, H. E.

    1975-01-01

    Four designs of drilled (cylindrically hollow) balls were tested for resistance to bending fatigue. Bending fatigue has been demonstrated to be a limiting factor in previous evaluations of the drilled ball concept. A web reinforced drilled ball was most successful in resisting bending fatigue. Another design of through drilled design, involving a heavier wall than the standard reference ball, also showed significant improvement in resistance to bending fatigue.

  18. The Soccer-Ball Problem

    NASA Astrophysics Data System (ADS)

    Hossenfelder, Sabine

    2014-07-01

    The idea that Lorentz-symmetry in momentum space could be modified but still remain observer-independent has received quite some attention in the recent years. This modified Lorentz-symmetry, which has been argued to arise in Loop Quantum Gravity, is being used as a phenomenological model to test possibly observable effects of quantum gravity. The most pressing problem in these models is the treatment of multi-particle states, known as the 'soccer-ball problem'. This article briefly reviews the problem and the status of existing solution attempts.

  19. Two-ball Newton's cradle

    NASA Astrophysics Data System (ADS)

    Glendinning, Paul

    2011-12-01

    Newton's cradle for two balls with Hertzian interactions is considered as a hybrid system, and this makes it possible to derive return maps for the motion between collisions in an exact form despite the fact that the three-halves interaction law cannot be solved in closed form. The return maps depend on a constant whose value can only be determined numerically, but solutions can be written down explicitly in terms of this parameter, and we compare this with the results of simulations. The results are in fact independent of the details of the interaction potential.

  20. Mechanical design problems associated with turbopump fluid film bearings

    NASA Technical Reports Server (NTRS)

    Evces, Charles R.

    1990-01-01

    Most high speed cryogenic turbopumps for liquid propulsion rocket engines currently use ball or roller contact bearings for rotor support. The operating speeds, loads, clearances, and environments of these pumps combine to make bearing wear a limiting factor on turbopump life. An example is the high pressure oxygen turbopump (HPOTP) used in the Space Shuttle Main Engine (SSME). Although the HPOTP design life is 27,000 seconds at 30,000 rpms, or approximately 50 missions, bearings must currently be replaced after 2 missions. One solution to the bearing wear problem in the HPOTP, as well as in future turbopump designs, is the utilization of fluid film bearings in lieu of continuous contact bearings. Hydrostatic, hydrodynamic, and damping seal bearings are all replacement candidates for contact bearings in rocket engine high speed turbomachinery. These three types of fluid film bearings have different operating characteristics, but they share a common set of mechanical design opportunities and difficulties. Results of research to define some of the mechanical design issues are given. Problems considered include transient strat/stop rub, non-operational rotor support, bearing wear inspection and measurement, and bearing fluid supply route. Emphasis is given to the HPOTP preburner pump (PBP) bearing, but the results are pertinent to high-speed cryogenic turbomachinery in general.

  1. Design and fabrication of prototype system for early warning of impending bearing failure

    NASA Technical Reports Server (NTRS)

    Meacher, J.; Chen, H. M.

    1974-01-01

    A test program was conducted with the objective of developing a method and equipment for on-line monitoring of installed ball bearings to detect deterioration or impending failure of the bearings. The program was directed at the spin-axis bearings of a control moment gyro. The bearings were tested at speeds of 6000 and 8000 rpm, thrust loads from 50 to 1000 pounds, with a wide range of lubrication conditions, with and without a simulated fatigue spall implanted in the inner race ball track. It was concluded that a bearing monitor system based on detection and analysis of modulations of a fault indicating bearing resonance frequency can provide a low threshold of sensitivity.

  2. Determination of Rolling-Element Fatigue Life From Computer Generated Bearing Tests

    NASA Technical Reports Server (NTRS)

    Vlcek, Brian L.; Hendricks, Robert C.; Zaretsky, Erwin V.

    2003-01-01

    Two types of rolling-element bearings representing radial loaded and thrust loaded bearings were used for this study. Three hundred forty (340) virtual bearing sets totaling 31400 bearings were randomly assembled and tested by Monte Carlo (random) number generation. The Monte Carlo results were compared with endurance data from 51 bearing sets comprising 5321 bearings. A simple algebraic relation was established for the upper and lower L(sub 10) life limits as function of number of bearings failed for any bearing geometry. There is a fifty percent (50 percent) probability that the resultant bearing life will be less than that calculated. The maximum and minimum variation between the bearing resultant life and the calculated life correlate with the 90-percent confidence limits for a Weibull slope of 1.5. The calculated lives for bearings using a load-life exponent p of 4 for ball bearings and 5 for roller bearings correlated with the Monte Carlo generated bearing lives and the bearing data. STLE life factors for bearing steel and processing provide a reasonable accounting for differences between bearing life data and calculated life. Variations in Weibull slope from the Monte Carlo testing and bearing data correlated. There was excellent agreement between percent of individual components failed from Monte Carlo simulation and that predicted.

  3. Soccer Ball Lift Coefficients via Trajectory Analysis

    ERIC Educational Resources Information Center

    Goff, John Eric; Carre, Matt J.

    2010-01-01

    We performed experiments in which a soccer ball was launched from a machine while two high-speed cameras recorded portions of the trajectory. Using the trajectory data and published drag coefficients, we extracted lift coefficients for a soccer ball. We determined lift coefficients for a wide range of spin parameters, including several spin…

  4. Using Ruby Balls As Fiducial Marks

    NASA Technical Reports Server (NTRS)

    Painter, Nance M.

    1990-01-01

    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.

  5. NCI and Leidos Play Ball | Poster

    Cancer.gov

    By Carolynne Keenan, Contributing Writer The ping of an aluminum bat off a ball or the thump of a pop-up fly ball caught in a glove are two sounds familiar to baseball fans. Slow-pitch softball sounds—like those in the August game between mixed teams of NCI and Leidos Biomedical Research (formerly SAIC-Frederick) players—are similar.

  6. Incorporating general race and housing flexibility and deadband in rolling element bearing analysis

    NASA Technical Reports Server (NTRS)

    Davis, R. R.; Vallance, C. S.

    1989-01-01

    Methods for including the effects of general race and housing compliance and outer race-to-housing deadband (clearance) in rolling element bearing mechanics analysis is presented. It is shown that these effects can cause significant changes in bearing stiffness characteristics, which are of major importance in rotordynamic response of turbomachinery and other rotating systems. Preloading analysis is demonstrated with the finite element/contact mechanics hybrid method applied to a 45 mm angular contact ball bearing.

  7. Self-dispersed crumpled graphene balls in oil for friction and wear reduction

    PubMed Central

    Dou, Xuan; Koltonow, Andrew R.; He, Xingliang; Jang, Hee Dong; Wang, Qian; Chung, Yip-Wah; Huang, Jiaxing

    2016-01-01

    Ultrafine particles are often used as lubricant additives because they are capable of entering tribological contacts to reduce friction and protect surfaces from wear. They tend to be more stable than molecular additives under high thermal and mechanical stresses during rubbing. It is highly desirable for these particles to remain well dispersed in oil without relying on molecular ligands. Borrowing from the analogy that pieces of paper that are crumpled do not readily stick to each other (unlike flat sheets), we expect that ultrafine particles resembling miniaturized crumpled paper balls should self-disperse in oil and could act like nanoscale ball bearings to reduce friction and wear. Here we report the use of crumpled graphene balls as a high-performance additive that can significantly improve the lubrication properties of polyalphaolefin base oil. The tribological performance of crumpled graphene balls is only weakly dependent on their concentration in oil and readily exceeds that of other carbon additives such as graphite, reduced graphene oxide, and carbon black. Notably, polyalphaolefin base oil with only 0.01–0.1 wt % of crumpled graphene balls outperforms a fully formulated commercial lubricant in terms of friction and wear reduction. PMID:26811466

  8. Surface modification of titanium using steel slag ball and shot blasting treatment for biomedical implant applications

    NASA Astrophysics Data System (ADS)

    Arifvianto, Budi; Suyitno; Mahardika, Muslim

    2013-08-01

    Surface modification is often performed using grit or shot blasting treatment for improving the performances of biomedical implants. The effects of blasting treatments using steel slag balls and spherical shots on the surface and subsurface of titanium were studied in this paper. The treatments were conducted for 60-300 s using 2-5 mm steel slag balls and 3.18 mm spherical shots. The surface morphology, roughness, and elemental composition of titanium specimens were examined prior to and after the treatments. Irregular and rough titanium surfaces were formed after the treatment with the steel slag balls instead of the spherical shots. The former treatment also introduced some bioactive elements on the titanium surface, but the latter one yielded a harder surface layer. In conclusion, both steel slag ball and shot blasting treatment have their own specialization in modifying the surface of metallic biomaterials. Steel slag ball blasting is potential for improving the osseointegration quality of implants; but the shot blasting is more appropriate for improving the mechanical properties of temporary and load bearing implants, such as osteosynthesis plates.

  9. Self-dispersed crumpled graphene balls in oil for friction and wear reduction.

    PubMed

    Dou, Xuan; Koltonow, Andrew R; He, Xingliang; Jang, Hee Dong; Wang, Qian; Chung, Yip-Wah; Huang, Jiaxing

    2016-02-01

    Ultrafine particles are often used as lubricant additives because they are capable of entering tribological contacts to reduce friction and protect surfaces from wear. They tend to be more stable than molecular additives under high thermal and mechanical stresses during rubbing. It is highly desirable for these particles to remain well dispersed in oil without relying on molecular ligands. Borrowing from the analogy that pieces of paper that are crumpled do not readily stick to each other (unlike flat sheets), we expect that ultrafine particles resembling miniaturized crumpled paper balls should self-disperse in oil and could act like nanoscale ball bearings to reduce friction and wear. Here we report the use of crumpled graphene balls as a high-performance additive that can significantly improve the lubrication properties of polyalphaolefin base oil. The tribological performance of crumpled graphene balls is only weakly dependent on their concentration in oil and readily exceeds that of other carbon additives such as graphite, reduced graphene oxide, and carbon black. Notably, polyalphaolefin base oil with only 0.01-0.1 wt % of crumpled graphene balls outperforms a fully formulated commercial lubricant in terms of friction and wear reduction. PMID:26811466

  10. Fluid lubricated bearing construction

    DOEpatents

    Dunning, John R.; Boorse, Henry A.; Boeker, Gilbert F.

    1976-01-01

    1. A fluid lubricated thrust bearing assembly comprising, in combination, a first bearing member having a plain bearing surface, a second bearing member having a bearing surface confronting the bearing surface of said first bearing member and provided with at least one spiral groove extending inwardly from the periphery of said second bearing member, one of said bearing members having an axial fluid-tight well, a source of fluid lubricant adjacent to the periphery of said second bearing member, and means for relatively rotating said bearing members to cause said lubricant to be drawn through said groove and to flow between said bearing surfaces, whereby a sufficient pressure is built up between said bearing surfaces and in said well to tend to separate said bearing surfaces.

  11. NASA five-ball fatigue tester: Over 20 years of research

    NASA Technical Reports Server (NTRS)

    Zaretsky, E. V.; Parker, R. J.; Anderson, W. J.

    1981-01-01

    Studies were conducted to determine the effect on rolling-element fatigue life of contact angle, material hardness, chemistry, heat treatment and processing, lubricant type and chemistry, elastohydrodynamic film thickness, deformation and wear, vacuum, and temperature as well as Hertzian and residual stresses. Correlation was established between the results obtained using the five-ball tester and those obtained with full scale rolling-element bearings.

  12. Misalignment in Gas Foil Journal Bearings: An Experimental Study

    NASA Technical Reports Server (NTRS)

    Howard, Samuel A.

    2008-01-01

    As gas foil journal bearings become more prevalent in production machines, such as small gas turbine propulsion systems and microturbines, system-level performance issues must be identified and quantified in order to provide for successful design practices. Several examples of system-level design parameters that are not fully understood in foil bearing systems are thermal management schemes, alignment requirements, balance requirements, thrust load balancing, and others. In order to address some of these deficiencies and begin to develop guidelines, this paper presents a preliminary experimental investigation of the misalignment tolerance of gas foil journal bearing systems. Using a notional gas foil bearing supported rotor and a laser-based shaft alignment system, increasing levels of misalignment are imparted to the bearing supports while monitoring temperature at the bearing edges. The amount of misalignment that induces bearing failure is identified and compared to other conventional bearing types such as cylindrical roller bearings and angular contact ball bearings. Additionally, the dynamic response of the rotor indicates that the gas foil bearing force coefficients may be affected by misalignment.

  13. Adaptive Spindle Balancing Using Magnetically Levitated Bearings

    SciTech Connect

    BARNEY,PATRICK S.; LAUFFER,JAMES P.; PETTEYS,REBECCA; REDMOND,JAMES M.; SULLIVAN,WILLIAM N.

    1999-09-20

    A technological break through for supporting rotating shafts is the active magnetic bearing (AMB). Active magnetic bearings offer some important advantages over conventional ball, roller or journal bearings such as reduced frictional drag, no physical contact in the bearing, no need for lubricants, compatibility with high vacuum and ultra-clean environments, and ability to control shaft position within the bearing. The disadvantages of the AMB system are the increased cost and complexity, reduced bearing stiffness and the need for a controller. Still, there are certain applications, such as high speed machining, biomedical devices, and gyroscopes, where the additional cost of an AMB system can be justified. The inherent actuator capabilities of the AMB offer the potential for active balancing of spindles and micro-shaping capabilities for machine tools, The work presented in this paper concentrates on an AMB test program that utilizes the actuator capability to dynamically balance a spindle. In this study, an unbalanced AMB spindle system was enhanced with an LMS (Least Mean Squares) algorithm combined with an existing PID (proportional, integral, differential) control. This enhanced controller significantly improved the concentricity of an intentionally unbalanced shaft. The study included dynamic system analysis, test validation, control design and simulation, as well as experimental implementation using a digital LMS controller.

  14. Rolling-element bearings. [contact sliding friction study of solid bodies

    NASA Technical Reports Server (NTRS)

    Anderson, W. J.

    1980-01-01

    In contrast to hydrodynamic bearings, which depend for low-friction characteristics on a fluid film between the journal and the bearing surfaces, roller-element bearings employ a number of balls or rollers that roll in an annular space. The paper briefly outlines the advantages and disadvantages of roller-element bearings as compared to hydrodynamic bearings. The discussion covers bearing types, rolling friction, friction losses in rolling bearings, contact stresses, deformations, kinematics (normal and high speeds), bearing dynamics including elastohydrodynamics, load distribution, lubrication (grease, solid oil, oil-air mist), specific dynamic capacity and life, specific static capacity, and fatigue or wearout (elastohydrodynamics, wear). Rolling bearing wear factor as a function of operating environment is plotted and discussed.

  15. Ready for the Cosmic Ball

    NASA Technical Reports Server (NTRS)

    2006-01-01

    Something appears to be peering through a shiny red mask, in this new false-colored image from NASA's Spitzer Space Telescope. The mysterious blue eyes are actually starlight from the cores of two merging galaxies, called NGC 2207 and IC 2163. The mask is the galaxies' dusty spiral arms.

    NGC 2207 and IC 2163 recently met and began a sort of gravitational tango about 40 million years ago. The two galaxies are tugging at each other, stimulating new stars to form. Eventually, this cosmic ball will come to an end, when the galaxies meld into one. The dancing duo is located 140 million light-years away in the Canis Major constellation.

    The Spitzer image reveals that the galactic mask is adorned with strings of pearl-like beads. These dusty clusters of newborn stars, called 'beads on a string' by astronomers, appear as white balls throughout the arms of both galaxies. They were formed when the galaxies first interacted, forcing dust and gas to clump together into colonies of stars.

    This type of beading has been seen before in other galaxies, but it took Spitzer's infrared eyes to identify them in NGC 2207 and IC 2163. Spitzer was able to see the beads because the stars inside heat up surrounding dust, which then radiates with infrared light.

    The biggest bead lighting up the left side of the mask is also the densest. In fact, some of its central stars might have merged to form a black hole. (Now, that would be quite the Mardi Gras mask!)

    This picture, taken by Spitzer's infrared array camera, is a four-channel composite. It shows light with wavelengths of 3.6 microns (blue); 4.5 microns (green); and 5.8 and 8.0 microns (red). The contribution from starlight (measured at 3.6 microns) has been subtracted from the 5.8- and 8-micron channels to enhance the visibility of the dust features.

  16. Dolphin underwater bait-balling behaviors in relation to group and prey ball sizes.

    PubMed

    Vaughn-Hirshorn, Robin L; Muzi, Elisa; Richardson, Jessica L; Fox, Gabriella J; Hansen, Lauren N; Salley, Alyce M; Dudzinski, Kathleen M; Würsig, Bernd

    2013-09-01

    We characterized dusky dolphin (Lagenorhynchus obscurus) feeding behaviors recorded on underwater video, and related behaviors to variation in prey ball sizes, dolphin group sizes, and study site (Argentina versus New Zealand, NZ). Herding behaviors most often involved dolphins swimming around the side or under prey balls, but dolphins in Argentina more often swam under prey balls (48% of passes) than did dolphins in NZ (34% of passes). This result may have been due to differences in group sizes between sites, since groups are larger in Argentina. Additionally, in NZ, group size was positively correlated with proportion of passes that occurred under prey balls (p<0.001). Prey-capture attempts most often involved capturing fish from the side of prey balls, but dolphins in Argentina more often swam through prey balls (8% of attempts) than did dolphins in NZ (4% of attempts). This result may have been due to differences in prey ball sizes between sites, since dolphins fed on larger prey balls in Argentina (>74m(2)) than in NZ (maximum 33m(2)). Additionally, in NZ, dolphins were more likely to swim through prey balls to capture fish when they fed on larger prey balls (p=0.025).

  17. Numerical simulation of ball-racket impact

    NASA Astrophysics Data System (ADS)

    Yu, Yingpang

    The collision of a ball with a tennis racket is usually modeled in terms of rigid body dynamics or an elastic system involving only a few springs. In this paper, we study the impact between a tennis ball and racket, by modeling the tennis ball in two different yaws. One method models the tennis ball as a Hertz elastic body and the other one models the ball by a more accurate finite element analysis. In the first model, we assume that the elastic properties of the ball obeys Hertz's law. In the finite element model, we consider the tennis ball as a shell witch is a elastic system constructed out of many isotropic small linear flat, elements, witch have both elastic and damping properties. The damping in each way is approximated as viscous term. In both methods, we study the static condition of deformation against a rigid surface before applying these models to dynamical processes. We compare these two methods and eventually determine how the racket parameters effect the performance of the racket, using numerical simulations. Comparison with experiment are show to confirm the general conclusion of the model.

  18. Viscoelastic modelling of tennis ball properties

    NASA Astrophysics Data System (ADS)

    Sissler, L.; Jones, R.; Leaney, P. G.; Harland, A.

    2010-06-01

    An explicit finite element (FE) tennis ball model which illustrates the effects of the viscoelastic materials of a tennis ball on ball deformation and bounce during normal impacts is presented. A tennis ball is composed of a rubber core and a fabric cover comprised of a wool-nylon mix which exhibit non-linear strain rate properties during high velocity impacts. The rubber core model was developed and validated using low strain rate tensile tests on rubber samples as well as high velocity normal impacts of pressurised cores at velocities ranging from 15 m/s to 50 m/s. The impacts were recorded using a high speed video (HSV) camera to determine deformation, impact time and coefficient of restitution (COR). The material properties of the core model were tuned to match the HSV results. A two component anisotropic fabric model was created which included artificial Rayleigh damping to account for hysteresis effects, and the core model 'tuning' process was used to refine the cloth layer. The ball model's parameters were in good agreement with experimental data at all velocities for both cores and complete balls, and a time sequenced comparison of HSV ball motion and FE model confirmed the validity of the model.

  19. Cricket Ball Aerodynamics: Myth Versus Science

    NASA Technical Reports Server (NTRS)

    Mehta, Rabindra D.; Koga, Demmis J. (Technical Monitor)

    2000-01-01

    Aerodynamics plays a prominent role in the flight of a cricket ball released by a bowler. The main interest is in the fact that the ball can follow a curved flight path that is not always under the control of the bowler. ne basic aerodynamic principles responsible for the nonlinear flight or "swing" of a cricket ball were identified several years ago and many papers have been published on the subject. In the last 20 years or so, several experimental investigations have been conducted on cricket ball swing, which revealed the amount of attainable swing, and the parameters that affect it. A general overview of these findings is presented with emphasis on the concept of late swing and the effects of meteorological conditions on swing. In addition, the relatively new concept of "reverse" swing, how it can be achieved in practice and the role in it of ball "tampering", are discussed in detail. A discussion of the "white" cricket ball used in last year's World Cup, which supposedly possesses different swing properties compared to a conventional red ball, is also presented.

  20. Designing Hollow Nano Gold Golf Balls

    PubMed Central

    2015-01-01

    Hollow/porous nanoparticles, including nanocarriers, nanoshells, and mesoporous materials have applications in catalysis, photonics, biosensing, and delivery of theranostic agents. Using a hierarchical template synthesis scheme, we have synthesized a nanocarrier mimicking a golf ball, consisting of (i) solid silica core with a pitted gold surface and (ii) a hollow/porous gold shell without silica. The template consisted of 100 nm polystyrene beads attached to a larger silica core. Selective gold plating of the core followed by removal of the polystyrene beads produced a golf ball-like nanostructure with 100 nm pits. Dissolution of the silica core produced a hollow/porous golf ball-like nanostructure. PMID:24937196

  1. Horizontal stability of a bouncing ball

    NASA Astrophysics Data System (ADS)

    McBennett, Brendan G.; Harris, Daniel M.

    2016-09-01

    We present an investigation of a partially elastic ball bouncing on a vertically vibrated concave parabolic surface in two dimensions. In particular, we demonstrate that simple vertical motion, wherein the ball bounces periodically at the parabola's vertex, is unstable to horizontal perturbations when the parabolic coefficient defining the surface shape exceeds a critical value. The result is a new periodic solution where the ball bounces laterally over the vertex. As the parabola is further steepened, this new solution also becomes unstable which gives rise to other complex periodic and chaotic bouncing states, all characterized by persistent lateral motion.

  2. Monte Carlo Simulation of Sudden Death Bearing Testing

    NASA Technical Reports Server (NTRS)

    Vlcek, Brian L.; Hendricks, Robert C.; Zaretsky, Erwin V.

    2003-01-01

    Monte Carlo simulations combined with sudden death testing were used to compare resultant bearing lives to the calculated hearing life and the cumulative test time and calendar time relative to sequential and censored sequential testing. A total of 30 960 virtual 50-mm bore deep-groove ball bearings were evaluated in 33 different sudden death test configurations comprising 36, 72, and 144 bearings each. Variations in both life and Weibull slope were a function of the number of bearings failed independent of the test method used and not the total number of bearings tested. Variation in L10 life as a function of number of bearings failed were similar to variations in lift obtained from sequentially failed real bearings and from Monte Carlo (virtual) testing of entire populations. Reductions up to 40 percent in bearing test time and calendar time can be achieved by testing to failure or the L(sub 50) life and terminating all testing when the last of the predetermined bearing failures has occurred. Sudden death testing is not a more efficient method to reduce bearing test time or calendar time when compared to censored sequential testing.

  3. Observations of Spacecraft Bearing Lubricant Redistribution Based on Thermal Conductance Measurements

    NASA Technical Reports Server (NTRS)

    Takeuchi, Yoshimi R.; Frantz, Peter P.; Hilton, Michael R.

    2014-01-01

    The performance and life of precision ball bearings are critically dependent on maintaining a quantity of oil at the ball/race interface that is sufficient to support a robust protective film. In space applications, where parched conditions are intentionally the norm, harsh operating conditions can displace the small reserves of oil, resulting in reduced film thickness and premature wear. In the past, these effects have proven difficult to model or to measure experimentally. This paper describes a study addressing this challenge, where bearing thermal conductance measurements are employed to infer changes in lubricant quantity at the critical rolling interfaces. In the first part of the paper, we explain how the lubricant's presence and its quantity impacts bearing thermal conductance measurements. For a stationary bearing, we show that conductance is directly related to the lubricant quantity in the ball/race contacts. Hence, aspects of bearing performance related to oil quantity can be understood and insights improved with thermal conductance data. For a moving bearing, a different mechanism of heat transfer dominates and is dependent on lubricant film thickness on the ball. In the second part of the report, we discuss lubricant quantity observations based on bearing thermal conductance measurements. Lubricant quantity, and thus bearing thermal conductance, depends on various initial and operating conditions and is impacted further by the run-in process. A significant effect of maximum run-in speed was also observed, with less oil remaining after obtaining higher speeds. Finally, we show that some of the lubricant that is displaced between the ball and race during run-in operation can be recovered during rest, and we measure the rate of recovery for one example.

  4. Production of Ball-Lightning-Like Luminous Balls by Electrical Discharges in Silicon

    NASA Astrophysics Data System (ADS)

    Paiva, Gerson Silva; Pavão, Antonio Carlos; Alpes de Vasconcelos, Elder; Mendes, Odim, Jr.; Felisberto da Silva, Eronides, Jr.

    2007-01-01

    We performed electric arc discharges in pure Si to generate luminous balls with lifetime in the order of seconds and several properties usually reported for natural ball lightning. This simple experiment does not rely on energy sources and excitation mechanisms that are improbable in the natural phenomenon and clearly demonstrates the role of vaporization and oxidation of Si, as proposed by the Abrahamson-Dinniss theory for ball-lightning formation.

  5. Production of ball-lightning-like luminous balls by electrical discharges in silicon.

    PubMed

    Paiva, Gerson Silva; Pavão, Antonio Carlos; Alpes de Vasconcelos, Elder; Mendes, Odim; da Silva, Eronides Felisberto

    2007-01-26

    We performed electric arc discharges in pure Si to generate luminous balls with lifetime in the order of seconds and several properties usually reported for natural ball lightning. This simple experiment does not rely on energy sources and excitation mechanisms that are improbable in the natural phenomenon and clearly demonstrates the role of vaporization and oxidation of Si, as proposed by the Abrahamson-Dinniss theory for ball-lightning formation.

  6. Production of ball-lightning-like luminous balls by electrical discharges in silicon.

    PubMed

    Paiva, Gerson Silva; Pavão, Antonio Carlos; Alpes de Vasconcelos, Elder; Mendes, Odim; da Silva, Eronides Felisberto

    2007-01-26

    We performed electric arc discharges in pure Si to generate luminous balls with lifetime in the order of seconds and several properties usually reported for natural ball lightning. This simple experiment does not rely on energy sources and excitation mechanisms that are improbable in the natural phenomenon and clearly demonstrates the role of vaporization and oxidation of Si, as proposed by the Abrahamson-Dinniss theory for ball-lightning formation. PMID:17358820

  7. Flexible timing of eye movements when catching a ball.

    PubMed

    López-Moliner, Joan; Brenner, Eli

    2016-01-01

    In ball games, one cannot direct ones gaze at the ball all the time because one must also judge other aspects of the game, such as other players' positions. We wanted to know whether there are times at which obtaining information about the ball is particularly beneficial for catching it. We recently found that people could catch successfully if they saw any part of the ball's flight except the very end, when sensory-motor delays make it impossible to use new information. Nevertheless, there may be a preferred time to see the ball. We examined when six catchers would choose to look at the ball if they had to both catch the ball and find out what to do with it while the ball was approaching. A catcher and a thrower continuously threw a ball back and forth. We recorded their hand movements, the catcher's eye movements, and the ball's path. While the ball was approaching the catcher, information was provided on a screen about how the catcher should throw the ball back to the thrower (its peak height). This information disappeared just before the catcher caught the ball. Initially there was a slight tendency to look at the ball before looking at the screen but, later, most catchers tended to look at the screen before looking at the ball. Rather than being particularly eager to see the ball at a certain time, people appear to adjust their eye movements to the combined requirements of the task.

  8. Flexible timing of eye movements when catching a ball.

    PubMed

    López-Moliner, Joan; Brenner, Eli

    2016-01-01

    In ball games, one cannot direct ones gaze at the ball all the time because one must also judge other aspects of the game, such as other players' positions. We wanted to know whether there are times at which obtaining information about the ball is particularly beneficial for catching it. We recently found that people could catch successfully if they saw any part of the ball's flight except the very end, when sensory-motor delays make it impossible to use new information. Nevertheless, there may be a preferred time to see the ball. We examined when six catchers would choose to look at the ball if they had to both catch the ball and find out what to do with it while the ball was approaching. A catcher and a thrower continuously threw a ball back and forth. We recorded their hand movements, the catcher's eye movements, and the ball's path. While the ball was approaching the catcher, information was provided on a screen about how the catcher should throw the ball back to the thrower (its peak height). This information disappeared just before the catcher caught the ball. Initially there was a slight tendency to look at the ball before looking at the screen but, later, most catchers tended to look at the screen before looking at the ball. Rather than being particularly eager to see the ball at a certain time, people appear to adjust their eye movements to the combined requirements of the task. PMID:26982371

  9. Improve pumping efficiency with PSZ ceramic balls

    SciTech Connect

    Brothers, J. )

    1989-04-01

    partially stabilized zirconia (PSZ) ceramic balls used today in downhole pumps improve both the efficiency and run time of sucker rod pumping systems. Recent field tests showed the balls increased the average run time of downhole pumps by 440%. While there are other types of stabilizers, only magnesia PSZ is appropriate for downhole pumps. The more commonly found alloy balls and carbide balls have been found to deform and not seal under these conditions. PSZ is most notable for its resistance to breaking from impact. A nonductile material, it will make a perfect seal on the seat despite any impact, enhancing its use in fluid pound situations. Other PSZ applications in downhole pumps and related equipment include plunger inserts, discharge inserts, plunger rings, choke parts, pressure relief valve components, and triplex pump plungers.

  10. Laryngeal Fracture Caused by a Lacrosse Ball.

    PubMed

    Trinidade, Aaron; Shakeel, Muhammad; Stickle, Brian; Ah-See, Kim W

    2015-11-01

    Neck injuries in lacrosse are rare and mostly involve the musculoskeletal system. The lacrosse ball is a solid rubber ball of approximately 20 cm in diameter and the fastest shot recorded in professional lacrosse is over 100 mph. Despite wearing full protection, the neck remains prone to blunt trauma by this ball. A 23-year man sustained a direct blow to his left neck by a lacrosse ball during play, resulting in immediate aphonia and stridor. CT scan confirmed a left thyroid lamina fracture. The patient was treated conservatively and his airway was monitored for 24 hours. He made a full recovery. It is important that lacrosse players should be aware of this potential injury and appropriate precautions should be taken to avoid this trauma.

  11. Laryngeal Fracture Caused by a Lacrosse Ball.

    PubMed

    Trinidade, Aaron; Shakeel, Muhammad; Stickle, Brian; Ah-See, Kim W

    2015-11-01

    Neck injuries in lacrosse are rare and mostly involve the musculoskeletal system. The lacrosse ball is a solid rubber ball of approximately 20 cm in diameter and the fastest shot recorded in professional lacrosse is over 100 mph. Despite wearing full protection, the neck remains prone to blunt trauma by this ball. A 23-year man sustained a direct blow to his left neck by a lacrosse ball during play, resulting in immediate aphonia and stridor. CT scan confirmed a left thyroid lamina fracture. The patient was treated conservatively and his airway was monitored for 24 hours. He made a full recovery. It is important that lacrosse players should be aware of this potential injury and appropriate precautions should be taken to avoid this trauma. PMID:26577976

  12. Bouncing ball problem: numerical behavior characterization

    NASA Astrophysics Data System (ADS)

    Macau, E. E. N.; Carneiro, M. V.; Barroso, J. J.

    2010-09-01

    This paper gives an overview of the simple yet fundamental bouncing ball problem, which consists of a ball bouncing vertically on a sinusoidally vibrating table under the action of gravity. The dynamics is modeled on the basis of a discrete map of difference equations, which numerically solved fully reveals a rich variety of nonlinear behaviors, encompassing irregular non-periodic orbits, subharmonic and chaotic motions, chattering mechanisms, and also unbounded non-periodic orbits.

  13. Gravitational waves from Q-ball formation

    SciTech Connect

    Chiba, Takeshi; Kamada, Kohei; Yamaguchi, Masahide

    2010-04-15

    We study the detectability of the gravitational waves (GWs) from the Q-ball formation associated with the Affleck-Dine (AD) mechanism, taking into account both the dilution effects due to Q-ball domination and to finite temperature. The AD mechanism predicts the formation of nontopological solitons, Q-balls, from which GWs are generated. Q-balls with large conserved charge Q can produce a large amount of GWs. On the other hand, the decay rate of such Q-balls is so small that they may dominate the energy density of the Universe, which implies that GWs are significantly diluted and that their frequencies are redshifted during the Q-ball dominated era. Thus, the detectability of the GWs associated with the formation of Q-balls is determined by these two competing effects. We find that there is a finite but small parameter region where such GWs may be detected by future detectors such as DECIGO or BBO, only in the case when the thermal logarithmic potential dominates the potential of the AD field. Otherwise GWs from Q-balls would not be detectable even by these futuristic detectors: {Omega}{sub GW}{sup 0}<10{sup -21}. Unfortunately, for such parameter region the present baryon asymmetry of the Universe can hardly be explained unless one fine-tunes A-terms in the potential. However the detection of such a GW background may give us an information about the early Universe, for example, it may suggest that the flat directions with B-L=0 are favored.

  14. Fractal aggregates in tennis ball systems

    NASA Astrophysics Data System (ADS)

    Sabin, J.; Bandín, M.; Prieto, G.; Sarmiento, F.

    2009-09-01

    We present a new practical exercise to explain the mechanisms of aggregation of some colloids which are otherwise not easy to understand. We have used tennis balls to simulate, in a visual way, the aggregation of colloids under reaction-limited colloid aggregation (RLCA) and diffusion-limited colloid aggregation (DLCA) regimes. We have used the images of the cluster of balls, following Forrest and Witten's pioneering studies on the aggregation of smoke particles, to estimate their fractal dimension.

  15. Ubiquitous tar balls with a California-source signature on the shorelines of Prince William Sound, Alaska

    USGS Publications Warehouse

    Kvenvolden, K.A.; Hostettler, F.D.; Carlson, P.R.; Rapp, J.B.; Threlkeld, C.N.; Warden, A.

    1995-01-01

    Although the shorelines of Prince William Sound still bear traces of the 1989 Exxon Valdez oil spill, most of the flattened tar balls that can be found today on these shorelines are not residues of Exxon Valdez oil. Instead, the carbon-isotopic and hydrocarbon-biomarker signatures of 61 tar ball samples, collected from shorelines throughout the northern and western parts of the sound, are all remarkably similar and have characteristics consistent with those of oil products that originated from the Monterey Formation source rocks of California. The carbon-isotopic compositions of the tar balls are all closely grouped (??13CPDB = -23.7 ?? 0.2???), within the range found in crude oils from those rocks, but are distinct from isotopic compositions of 28 samples of residues from the Exxon Valdez oil spill (??13CPDB = -29.4 ?? 0.1???). Likewise, values for selected biomarker ratios in the tar balls are all similar but distinct from values of residues from the 1989 oil spill. Carbon-isotopic and biomarker signatures generally relate the tar balls to oil products used in Alaska before ???1970 for construction and pavements. How these tar balls with such similar geochemical characteristics became so widely dispersed throughout the northern and western parts of the sound is not known with certainty, but the great 1964 Alaska earthquake was undoubtedly an important trigger, causing spills from ruptured storage facilities of California-sourced asphalt and fuel oil into Prince William Sound.

  16. Effects of bushings characteristics on suspension ball joint travels

    NASA Astrophysics Data System (ADS)

    Yang, Xiaobo

    2011-02-01

    In this paper, a short-long arm type front suspension is represented using multi-body dynamics model established with ADAMS®, where the suspension bushings modelled as linear and nonlinear elements, respectively, are integrated with a flexible cradle and other suspension components. A ball joint travel, defined as the angular displacement between the two parts connected with the ball joint, is calculated, where the measured wheel loads and spindle accelerations from a proving ground severe durability test schedule serve as the input data. The ball joints considered in this study include lower ball joints, upper ball joints, outer tierod ball joints, and inner tierod ball joints. The results clearly illustrate that the bushing stiffness and nonlinearity are important for an accurate prediction of ball joint travels and the ball joint travel sensitivities to considered design variables are important for engineers to understand and ensure reliable designs of ball joints.

  17. Unbalance Response Prediction for Accelerating Rotors With Load-Dependent Nonlinear Bearing Stiffness

    NASA Technical Reports Server (NTRS)

    Fleming, David P.; Sawicki, Jaezy T.; Poplawski, J. V.

    2005-01-01

    Rolling-element bearing forces vary nonlinearly with bearing deflection. Thus an accurate rotordynamic analysis requires that bearing forces corresponding to the actual bearing deflection be utilized. Previous papers have explored the transient effect of suddenly applied imbalance and the steady-state unbalance response, using bearing forces calculated by the rolling-element bearing analysis code COBRA-AHS. The present work considers the acceleration of a rotor through one or more critical speeds. The rotordynamic analysis showed that for rapid acceleration rates the maximum response amplitude may be considerably less than predicted by steady-state analysis. Above the critical speed, transient vibration at the rotor natural frequency occurs, similar to that predicted for a Jeffcott rotor with constant-stiffness bearings. A moderate amount of damping will markedly reduce the vibration amplitude, but this damping is not inherent in ball bearings.

  18. Design of a compliant passive magnetic bearing for use in SIRTF's Tertiary Mirror Assembly

    NASA Technical Reports Server (NTRS)

    Cannon, David M.; Brereton, Margot; Dill, Harry; Sullivan, Mark

    1990-01-01

    A proposed baseline design for the Space Infrared Telescope Facility includes a Tertiary Mirror Assembly (TMA) which selectively redirects the telescope's converging science beam to each of several instruments. The TMA's mirror rotates on an axis coincident with the beam's axis, and is held steady during observation by a kinematic mount. A bearing has been designed whose compliance causes minimal interference with the precision of the kinematic mount, and which is well suited to the particular requirements of a cryogenic satellite such as SIRTF. The bearing suspends its rotor by taking advantage of the repulsion between a superconductor and a magnet. It potentially eliminates problems associated with mechanical bearings that arise in similar applications, such as lubricant loss or failure, bearing wear, and sensitivity to particulates, and does so without imposing the thermal load of a bearing heater or active magnetic bearing. The bearing shows promise of offering an alternative to ball bearings in cryogenic applications where some compliance is acceptable or advantageous.

  19. The ball SITE sign: Ball sports-induced targetoid erythema in a racquetball player

    PubMed Central

    Cohen, Philip R.

    2015-01-01

    Background: Cutaneous injury following impact of a high velocity ball to the skin may result in either erythema or purpura or both. The lesion typically appears as an annular ring of erythema with or without accompanying ecchymosis when the skin is contacted by a paintball, a ping pong ball, a racquetball or a squash ball. Purpose: To describe a girl with targetoid erythema following impact of a racquetball on her flank and back and to review other sports associated with this response to skin injury. Methods: PubMed was used to search the following terms, separately and in combination: ball, erythema, paint, ping pong, purpura, racquetball, sign, site, sports, squash, targetoid. All papers were reviewed and relevant manuscripts, along with their reference citations, were evaluated. Results: A 13-year-old girl developed an annular red ring surrounding a central area of normal appearing skin on her right flank and upper back where a racquetball traveling at a high velocity contacted her skin. Similar appearing lesions of targetoid erythema have been described at the cutaneous impact sites of either paintballs, ping pong balls, squash balls; in addition to erythema, purpura may also concurrently appear or subsequently develop at the contact location of the ball with the skin. Conclusions: Targetoid erythema is a pathognomonic cutaneous presentation resulting from the impact of either a paintball, ping pong ball, racquetball or squash ball—that is traveling at a high velocity—with a sport participant’s skin. The ball SITE (sports-induced targetoid erythema) sign is suggested as a unifying nomenclature to designate this unique, ball sport-associated, cutaneous dermatosis in athletes participating in sports in which high velocity impact of the ball with the skin may occur. PMID:26336625

  20. Large deflection analysis of a tension-foil bearing

    NASA Technical Reports Server (NTRS)

    Elrod, David A.

    1996-01-01

    The rolling element bearings (REB's) which support many turbomachinery rotors offer high load capacity, low power requirements, and durability. Two disadvantages of REB's are as follows: rolling or sliding contact within the bearing has life-limiting consequences; and REB's provide essentially no damping. The REB's in the Space Shuttle Main Engine (SSME) turbopumps must sustain high static and dynamic loads, at high speeds, with a cryogenic fluid as lubricant and coolant. The pump end ball bearings limit the life of the SSME high pressure oxygen turbopump (HPOTP). Compliant foil bearing (CFB) manufacturers have proposed replacing turbopump REB's with CFB's. CFB's work well in aircraft air cycle machines, auxiliary power units, and refrigeration compressors. In a CFB, the rotor only contacts the foil support structure during start up and shut down. CFB damping is higher than REB damping. However, the load capacity of the CFB is low, compared to a REB. Furthermore, little stiffness and damping data exist for the CFB. A rotordynamic analysis for turbomachinery critical speeds and stability requires the input of bearing stiffness and damping coefficients. The two basic types of CFB are the tension-dominated bearing and the bending-dominated bearing. Many investigators have analyzed and measured characteristics of tension-dominated foil bearings, which are applied principally in magnetic tape recording. The bending-dominated CFB is used more in rotating machinery. Recently, a new tension-foil bearing configuration has been proposed for turbomachinery applications.

  1. Passive magnetic bearing configurations

    DOEpatents

    Post, Richard F.

    2011-01-25

    A journal bearing provides vertical and radial stability to a rotor of a passive magnetic bearing system when the rotor is not rotating and when it is rotating. In the passive magnetic bearing system, the rotor has a vertical axis of rotation. Without the journal bearing, the rotor is vertically and radially unstable when stationary, and is vertically stable and radially unstable when rotating.

  2. Rolling Bearing Life Prediction, Theory, and Application

    NASA Technical Reports Server (NTRS)

    Zaretsky, Erwin V.

    2013-01-01

    A tutorial is presented outlining the evolution, theory, and application of rolling-element bearing life prediction from that of A. Palmgren, 1924; W. Weibull, 1939; G. Lundberg and A. Palmgren, 1947 and 1952; E. Ioannides and T. Harris, 1985; and E. Zaretsky, 1987. Comparisons are made between these life models. The Ioannides-Harris model without a fatigue limit is identical to the Lundberg-Palmgren model. The Weibull model is similar to that of Zaretsky if the exponents are chosen to be identical. Both the load-life and Hertz stress-life relations of Weibull, Lundberg and Palmgren, and Ioannides and Harris reflect a strong dependence on the Weibull slope. The Zaretsky model decouples the dependence of the critical shear stress-life relation from the Weibull slope. This results in a nominal variation of the Hertz stress-life exponent. For 9th- and 8th-power Hertz stress-life exponents for ball and roller bearings, respectively, the Lundberg- Palmgren model best predicts life. However, for 12th- and 10th-power relations reflected by modern bearing steels, the Zaretsky model based on the Weibull equation is superior. Under the range of stresses examined, the use of a fatigue limit would suggest that (for most operating conditions under which a rolling-element bearing will operate) the bearing will not fail from classical rolling-element fatigue. Realistically, this is not the case. The use of a fatigue limit will significantly overpredict life over a range of normal operating Hertz stresses. Since the predicted lives of rolling-element bearings are high, the problem can become one of undersizing a bearing for a particular application.

  3. Rolling-Element Bearings

    NASA Technical Reports Server (NTRS)

    Hamrock, B. J.; Anderson, W. J.

    1983-01-01

    Rolling element bearings are a precision, yet simple, machine element of great utility. A brief history of rolling element bearings is reviewed and the type of rolling element bearings, their geometry and kinematics, as well as the materials they are made from and the manufacturing processes they involve are described. Unloaded and unlubricated rolling element bearings, loaded but unlubricated rolling element bearings and loaded and lubricated rolling element bearings are considered. The recognition and understanding of elastohydrodynamic lubrication covered, represents one of the major development in rolling element bearings.

  4. Demonstration, Testing and Qualification of a High Temperature, High Speed Magnetic Thrust Bearing

    NASA Technical Reports Server (NTRS)

    DeWitt, Kenneth

    2005-01-01

    The gas turbine industry has a continued interest in improving engine performance and reducing net operating and maintenance costs. These goals are being realized because of advancements in aeroelasticity, materials, and computational tools such as CFD and engine simulations. These advancements aid in increasing engine thrust-to-weight ratios, specific fuel consumption, pressure ratios, and overall reliability through higher speed, higher temperature, and more efficient engine operation. Currently, rolling element bearing and squeeze film dampers are used to support rotors in gas turbine engines. Present ball bearing configurations are limited in speed (<2 million DN) and temperature (<5OO F) and require both cooling air and an elaborate lubrication system. Also, ball bearings require extensive preventative maintenance in order to assure their safe operation. Since these bearings are at their operational limits, new technologies must be found in order to take advantage of other advances. Magnetic bearings are well suited to operate at extreme temperatures and higher rotational speeds and are a promising solution to the problems that conventional rolling element bearings present. Magnetic bearing technology is being developed worldwide and is considered an enabling technology for new engine designs. Using magnetic bearings, turbine and compressor spools can be radically redesigned to be significantly larger and stiffer with better damping and higher rotational speeds. These advances, a direct result of magnetic bearing technology, will allow significant increases in engine power and efficiency. Also, magnetic bearings allow for real-time, in-situ health monitoring of the system, lower maintenance costs and down time.

  5. Evaluation of a hybrid hydrostatic bearing for cryogenic turbopump application

    NASA Technical Reports Server (NTRS)

    Spica, P. W.; Hannum, N. P.; Meyer, S. D.

    1986-01-01

    A hybrid hydrostatic bearing was designed to operate in liquid hydrogen at speeds to 80,000 rpm and radial loads to 440 n (100 lbf). The bearing assembly consisted of a pair of 20-mm angular-contact ball bearings encased in a journal, which was in turn supported by a fluid film of liquid hydrogen. The size and operating conditions of the bearing were selected to be compatible with the operating requirements of an advanced technology turbopump. Several test parameters were varied to characterize the bearing's steady-state operation. The rotation of the tester shaft was varied between 0 and 80,000 rpm. Bearing inlet fluid pressure was varied between 2.07 and 4.48 MPa (300 and 650 psia), while the fluid sump pressure was independently varied between 0.34 and 2.07 MPa (50 and 300 psia). The maximum radial load applied to the bearing was 440 N (110 lbf). Measured hybrid-hydrostatic-bearing stiffness was 1.5 times greater than predicted, while the fluid flow rate through the bearing was 35 to 65 percent less than predicted. Under two-phase fluid conditions, the stiffness was even greater and the flow rate was less. The optimal pressure ratio for the bearing should be between 0.2 and 0.55 depending on the balance desired between bearing efficiency and stiffness. Startup and shutdown cyclic tests were conducted to demonstrate the ability of the hybrid-hydrostatic-bearing assembly to survive at least a 300-firing-duty cycle. For a typical cycle, the shaft was accelerated to 50,000 rpm in 1.8 sec. The bearing operated for 337 start-stop cycles without failure.

  6. Aerodynamic drag of modern soccer balls.

    PubMed

    Asai, Takeshi; Seo, Kazuya

    2013-12-01

    Soccer balls such as the Adidas Roteiro that have been used in soccer tournaments thus far had 32 pentagonal and hexagonal panels. Recently, the Adidas Teamgeist II and Adidas Jabulani, respectively having 14 and 8 panels, have been used at tournaments; the aerodynamic characteristics of these balls have not yet been verified. Now, the Adidas Tango 12, having 32 panels, has been developed for use at tournaments; therefore, it is necessary to understand its aerodynamic characteristics. Through a wind tunnel test and ball trajectory simulations, this study shows that the aerodynamic resistance of the new 32-panel soccer ball is larger in the high-speed region and lower in the middle-speed region than that of the previous 14- and 8-panel balls. The critical Reynolds number of the Roteiro, Teamgeist II, Jabulani, and Tango 12 was ~2.2 × 10(5) (drag coefficient, C d  ≈ 0.12), ~2.8 × 10(5) (C d  ≈ 0.13), ~3.3 × 10(5) (C d  ≈ 0.13), and ~2.4 × 10(5) (C d  ≈ 0.15), respectively. The flight trajectory simulation suggested that the Tango 12, one of the newest soccer balls, has less air resistance in the medium-speed region than the Jabulani and can thus easily acquire large initial velocity in this region. It is considered that the critical Reynolds number of a soccer ball, as considered within the scope of this experiment, depends on the extended total distance of the panel bonds rather than the small designs on the panel surfaces.

  7. Bearing diagnosis based on Mahalanobis-Taguchi-Gram-Schmidt method

    NASA Astrophysics Data System (ADS)

    Shakya, Piyush; Kulkarni, Makarand S.; Darpe, Ashish K.

    2015-02-01

    A methodology is developed for defect type identification in rolling element bearings using the integrated Mahalanobis-Taguchi-Gram-Schmidt (MTGS) method. Vibration data recorded from bearings with seeded defects on outer race, inner race and balls are processed in time, frequency, and time-frequency domains. Eleven damage identification parameters (RMS, Peak, Crest Factor, and Kurtosis in time domain, amplitude of outer race, inner race, and ball defect frequencies in FFT spectrum and HFRT spectrum in frequency domain and peak of HHT spectrum in time-frequency domain) are computed. Using MTGS, these damage identification parameters (DIPs) are fused into a single DIP, Mahalanobis distance (MD), and gain values for the presence of all DIPs are calculated. The gain value is used to identify the usefulness of DIP and the DIPs with positive gain are again fused into MD by using Gram-Schmidt Orthogonalization process (GSP) in order to calculate Gram-Schmidt Vectors (GSVs). Among the remaining DIPs, sign of GSVs of frequency domain DIPs is checked to classify the probable defect. The approach uses MTGS method for combining the damage parameters and in conjunction with the GSV classifies the defect. A Defect Occurrence Index (DOI) is proposed to rank the probability of existence of a type of bearing damage (ball defect/inner race defect/outer race defect/other anomalies). The methodology is successfully validated on vibration data from a different machine, bearing type and shape/configuration of the defect. The proposed methodology is also applied on the vibration data acquired from the accelerated life test on the bearings, which established the applicability of the method on naturally induced and naturally progressed defect. It is observed that the methodology successfully identifies the correct type of bearing defect. The proposed methodology is also useful in identifying the time of initiation of a defect and has potential for implementation in a real time environment.

  8. High efficiency magnetic bearings

    NASA Technical Reports Server (NTRS)

    Studer, Philip A.; Jayaraman, Chaitanya P.; Anand, Davinder K.; Kirk, James A.

    1993-01-01

    Research activities concerning high efficiency permanent magnet plus electromagnet (PM/EM) pancake magnetic bearings at the University of Maryland are reported. A description of the construction and working of the magnetic bearing is provided. Next, parameters needed to describe the bearing are explained. Then, methods developed for the design and testing of magnetic bearings are summarized. Finally, a new magnetic bearing which allows active torque control in the off axes directions is discussed.

  9. Corrosion of simulated bearing components of three bearing steels in the presence of chloride-contaminated lubricant

    NASA Technical Reports Server (NTRS)

    Parker, R. J.; Bamberger, E. N.; Nahm, A. H.

    1983-01-01

    Corrosion tests were run with AISI 52100, AISI M-50 and AMS 5794 under conditions that simulate the crevice corrosion found in aircraft ball and roller bearings rejected at overhaul for corrosion. Test specimens were fabricated that simulated the contacts of balls or rollers and the raceways. Corrosion cells were assembled in the presence of a lubricant contaminated with water and chloride ions. The cell was then thermally cycled between 339 K (150 F) and 276 K (37 F). The corrosion observed after 14 cycles was that of crevice and pitting corrosion typically found in aircraft bearings. AMS 5749 showed a very slight amount of corrosion. No appreciable differences were noted between AISI 52100 and AISI M-50, but both showed much greater corrosion than AMS 5749. The corrosion pits observed in AISI M-50 appeared to be fewer in number but generally deeper and larger than in AISI 52100.

  10. Ball machine usage in tennis: movement initiation and swing timing while returning balls from a ball machine and from a real server.

    PubMed

    Carboch, Jan; Süss, Vladimir; Kocib, Tomas

    2014-05-01

    Practicing with the use of a ball machine could handicap a player compared to playing against an actual opponent. Recent studies have shown some differences in swing timing and movement coordination, when a player faces a ball projection machine as opposed to a human opponent. We focused on the time of movement initiation and on stroke timing during returning tennis serves (simulated by a ball machine or by a real server). Receivers' movements were measured on a tennis court. In spite of using a serving ball speed from 90 kph to 135 kph, results showed significant differences in movement initiation and backswing duration between serves received from a ball machine and serves received from a real server. Players had shorter movement initiation when they faced a ball machine. Backswing duration was longer for the group using a ball machine. That demonstrates different movement timing of tennis returns when players face a ball machine. Use of ball machines in tennis practice should be limited as it may disrupt stroke timing. Key pointsPlayers have shorter initial move time when they are facing the ball machine.Using the ball machine results in different swing timing and movement coordination.The use of the ball machine should be limited.

  11. Ball machine usage in tennis: movement initiation and swing timing while returning balls from a ball machine and from a real server.

    PubMed

    Carboch, Jan; Süss, Vladimir; Kocib, Tomas

    2014-05-01

    Practicing with the use of a ball machine could handicap a player compared to playing against an actual opponent. Recent studies have shown some differences in swing timing and movement coordination, when a player faces a ball projection machine as opposed to a human opponent. We focused on the time of movement initiation and on stroke timing during returning tennis serves (simulated by a ball machine or by a real server). Receivers' movements were measured on a tennis court. In spite of using a serving ball speed from 90 kph to 135 kph, results showed significant differences in movement initiation and backswing duration between serves received from a ball machine and serves received from a real server. Players had shorter movement initiation when they faced a ball machine. Backswing duration was longer for the group using a ball machine. That demonstrates different movement timing of tennis returns when players face a ball machine. Use of ball machines in tennis practice should be limited as it may disrupt stroke timing. Key pointsPlayers have shorter initial move time when they are facing the ball machine.Using the ball machine results in different swing timing and movement coordination.The use of the ball machine should be limited. PMID:24790483

  12. Ball Machine Usage in Tennis: Movement Initiation and Swing Timing While Returning Balls from a Ball Machine and from a Real Server

    PubMed Central

    Carboch, Jan; Süss, Vladimir; Kocib, Tomas

    2014-01-01

    Practicing with the use of a ball machine could handicap a player compared to playing against an actual opponent. Recent studies have shown some differences in swing timing and movement coordination, when a player faces a ball projection machine as opposed to a human opponent. We focused on the time of movement initiation and on stroke timing during returning tennis serves (simulated by a ball machine or by a real server). Receivers’ movements were measured on a tennis court. In spite of using a serving ball speed from 90 kph to 135 kph, results showed significant differences in movement initiation and backswing duration between serves received from a ball machine and serves received from a real server. Players had shorter movement initiation when they faced a ball machine. Backswing duration was longer for the group using a ball machine. That demonstrates different movement timing of tennis returns when players face a ball machine. Use of ball machines in tennis practice should be limited as it may disrupt stroke timing. Key points Players have shorter initial move time when they are facing the ball machine. Using the ball machine results in different swing timing and movement coordination. The use of the ball machine should be limited. PMID:24790483

  13. The dynamic impact characteristics of tennis balls with tennis rackets.

    PubMed

    Haake, S J; Carré, M J; Goodwill, S R

    2003-10-01

    The dynamic properties of six types of tennis balls were measured using a force platform and high-speed digital video images of ball impacts on rigidly clamped tennis rackets. It was found that the coefficient of restitution reduced with velocity for impacts on a rigid surface or with a rigidly clamped tennis racket. Pressurized balls had the highest coefficient of restitution, which decreased by 20% when punctured. Pressureless balls had a coefficient of restitution approaching that of a punctured ball at high speeds. The dynamic stiffness of the ball or the ball-racket system increased with velocity and pressurized balls had the highest stiffness, which decreased by 35% when punctured. The characteristics of pressureless balls were shown to be similar to those of punctured balls at high velocity and it was found that lowering the string tension produced a smaller range of stiffness or coefficient of restitution. It was hypothesized that players might consider high ball stiffness to imply a high coefficient of restitution. Plots of coefficient of restitution versus stiffness confirmed the relationship and it was found that, generally, pressurized balls had a higher coefficient of restitution and stiffness than pressureless balls. The players might perceive these parameters through a combination of sound, vibration and perception of ball speed off the racket. PMID:14620027

  14. Flight trajectory of a rotating golf ball with grooves

    NASA Astrophysics Data System (ADS)

    Baek, Moonheum; Kim, Jooha; Choi, Haecheon

    2014-11-01

    Dimples are known to reduce drag on a sphere by the amount of 50% as compared to a smooth surface. Despite the advantage of reducing drag, dimples deteriorate the putting accuracy owing to their sharp edges. To minimize this putting error but maintain the same flight distance, we have devised a grooved golf ball (called G ball hereafter) for several years. In this study, we modify the shape and pattern of grooves, and investigate the flow characteristics of the G ball by performing wind-tunnel experiments at the Reynolds numbers of 0 . 5 ×105 - 2 . 5 ×105 and the spin ratios (ratio of surface velocity to the free-stream velocity) of 0 - 0.6 that include the real golf-ball velocity and rotational speed. We measure the drag and lift forces on the rotating G ball and compare them with those of a smooth ball and two well-known dimpled balls. The lift-to-drag ratio of the G ball is much higher than that of a smooth ball and is in between those of the two dimpled balls. The trajectories of flying golf balls are computed. The flight distance of G ball is almost the same as that of one dimpled ball but slightly shorter than that of the other dimpled ball. The fluid-dynamic aspects of these differences will be discussed at the talk. Supported by 2011-0028032, 2014M3C1B1033980.

  15. Silicon ball grid array chip carrier

    DOEpatents

    Palmer, David W.; Gassman, Richard A.; Chu, Dahwey

    2000-01-01

    A ball-grid-array integrated circuit (IC) chip carrier formed from a silicon substrate is disclosed. The silicon ball-grid-array chip carrier is of particular use with ICs having peripheral bond pads which can be reconfigured to a ball-grid-array. The use of a semiconductor substrate such as silicon for forming the ball-grid-array chip carrier allows the chip carrier to be fabricated on an IC process line with, at least in part, standard IC processes. Additionally, the silicon chip carrier can include components such as transistors, resistors, capacitors, inductors and sensors to form a "smart" chip carrier which can provide added functionality and testability to one or more ICs mounted on the chip carrier. Types of functionality that can be provided on the "smart" chip carrier include boundary-scan cells, built-in test structures, signal conditioning circuitry, power conditioning circuitry, and a reconfiguration capability. The "smart" chip carrier can also be used to form specialized or application-specific ICs (ASICs) from conventional ICs. Types of sensors that can be included on the silicon ball-grid-array chip carrier include temperature sensors, pressure sensors, stress sensors, inertia or acceleration sensors, and/or chemical sensors. These sensors can be fabricated by IC processes and can include microelectromechanical (MEM) devices.

  16. Dark matter balls help supernovae to explode

    NASA Astrophysics Data System (ADS)

    Froggatt, C. D.; Nielsen, H. B.

    2015-10-01

    As a solution to the well-known problem that the shock wave potentially responsible for the explosion of a supernova actually tends to stall, we propose a new energy source arising from our model for dark matter. Our earlier model proposed that dark matter should consist of cm-large white dwarf-like objects kept together by a skin separating two different sorts of vacua. These dark matter balls or pearls will collect in the middle of any star throughout its lifetime. At some stage during the development of a supernova, the balls will begin to take in neutrons and then other surrounding material. By passing into a ball nucleons fall through a potential of order 10 MeV, causing a severe production of heat — of order 10 foe for a solar mass of material eaten by the balls. The temperature in the iron core will thereby be raised, splitting up the iron into smaller nuclei. This provides a mechanism for reviving the shock wave when it arrives and making the supernova explosion really occur. The onset of the heating due to the dark matter balls would at first stop the collapse of the supernova progenitor. This opens up the possibility of there being two collapses giving two neutrino outbursts, as apparently seen in the supernova SN1987A — one in Mont Blanc and one 4 h 43 min later in both IMB and Kamiokande.

  17. Role of visual information in ball catching.

    PubMed

    Rosengren, K S; Pick, H L; von Hofsten, C

    1988-06-01

    The present study is concerned with the perceptual information about the body and space underlying the act of catching a ball. In a series of four experiments, subjects were asked to catch a luminous ball under various visual conditions. In general, catching in a normally illuminated room was contrasted with catching the luminous ball in an otherwise completely dark room. In the third and fourth experiments, intermediate conditions of visual information were included. The results suggest that it is possible to catch a ball with one hand when only the ball is visible, but performance is better when the subject has the benefit of a rich visual environment and two hands. The second experiment indicated that subject performance does improve with practice in the dark, but time spent in the darkened room itself doesn't result in a significant decrement in performance. Results of the third study suggest that vision of one's hand does not aid in the performance of this task whereas the presence of a minimal visual frame appears to aid performance. The final study examined the relation between catching performance and body sway under similar visual conditions. Results of this experiment imply that persons who exhibit relatively little postural sway in full-room lighting performed better at this catching task.

  18. High temperature aircraft turbine engine bearing and lubrication system development

    SciTech Connect

    Grant, D.H.; Chin, H.A.; Klenke, C.; Galbato, A.T.; Ragen, M.A.; Spitzer, R.F.

    1998-12-31

    Results are reported for a project sponsored by the US Air Force Wright Laboratories. The major emphasis of this project was the evaluation of bearing materials with improved corrosion resistance, high hot hardness, and high fracture toughness, intended to meet the requirements of the Integrated High Performance Turbine Engine Technologies (IHPTET) Phase 2 engine. The project included material property studies on candidate bearing materials and lubricants which formed the selection basis for subscale and full-scale bearing rig verification tests. The carburizing stainless steel alloy Pyrowear 675 demonstrated significant fatigue life, fracture toughness, and corrosion resistance improvements relative to the M50 NiL baseline bearing material. The new Skylube 2 (MCS-2482) lubricant provided significant thermal degradation improvements with respect to the Skylube 600 (PWA-524, MIL-L-87100) lubricant. Two 130 mm bore Pyrowear 675 hybrid ball bearings with silicon nitride balls were run successfully for 231 hours with Skylube 2 lubricant at temperatures consistent with IHPTET 2 requirements.

  19. Relativistic-microwave theory of ball lightning.

    PubMed

    Wu, H-C

    2016-06-22

    Ball lightning, a fireball sometimes observed during lightnings, has remained unexplained. Here we present a comprehensive theory for the phenomenon: At the tip of a lightning stroke reaching the ground, a relativistic electron bunch can be produced, which in turn excites intense microwave radiation. The latter ionizes the local air and the radiation pressure evacuates the resulting plasma, forming a spherical plasma bubble that stably traps the radiation. This mechanism is verified by particle simulations. The many known properties of ball lightning, such as the occurrence site, relation to the lightning channels, appearance in aircraft, its shape, size, sound, spark, spectrum, motion, as well as the resulting injuries and damages, are also explained. Our theory suggests that ball lighting can be created in the laboratory or triggered during thunderstorms. Our results should be useful for lightning protection and aviation safety, as well as stimulate research interest in the relativistic regime of microwave physics.

  20. Relativistic-microwave theory of ball lightning.

    PubMed

    Wu, H-C

    2016-01-01

    Ball lightning, a fireball sometimes observed during lightnings, has remained unexplained. Here we present a comprehensive theory for the phenomenon: At the tip of a lightning stroke reaching the ground, a relativistic electron bunch can be produced, which in turn excites intense microwave radiation. The latter ionizes the local air and the radiation pressure evacuates the resulting plasma, forming a spherical plasma bubble that stably traps the radiation. This mechanism is verified by particle simulations. The many known properties of ball lightning, such as the occurrence site, relation to the lightning channels, appearance in aircraft, its shape, size, sound, spark, spectrum, motion, as well as the resulting injuries and damages, are also explained. Our theory suggests that ball lighting can be created in the laboratory or triggered during thunderstorms. Our results should be useful for lightning protection and aviation safety, as well as stimulate research interest in the relativistic regime of microwave physics. PMID:27328835

  1. Electrostatic charge bounds for ball lightning models

    NASA Astrophysics Data System (ADS)

    Stephan, Karl D.

    2008-03-01

    Several current theories concerning the nature of ball lightning predict a substantial electrostatic charge in order to account for its observed motion and shape (Turner 1998 Phys. Rep. 293 1; Abrahamson and Dinniss 2000 Nature 403 519). Using charged soap bubbles as a physical model for ball lightning, we show that the magnitude of charge predicted by some of these theories is too high to allow for the types of motion commonly observed in natural ball lightning, which includes horizontal motion above the ground and movement near grounded conductors. Experiments show that at charge levels of only 10-15 nC, 3-cm-diameter soap bubbles tend to be attracted by induced charges to the nearest grounded conductor and rupture. We conclude with a scaling rule that can be used to extrapolate these results to larger objects and surroundings.

  2. On the energy characteristics of ball lightning.

    PubMed

    Bychkov, A V; Bychkov, V L; Abrahamson, John

    2002-01-15

    A compilation of 17 observations of ball lightning showing the most energetic effects is presented along with estimates of their energy content. These observations were chosen from several thousand for the much stronger interaction of each ball lightning on its surroundings, and the method of energy estimation outlined. The case is put that some of the observations show a higher energy than self-contained chemical energy could provide. Comments have been added to the paper, arguing that the energy estimations themselves should be consistent with whatever model is used for ball lightning. For example, the presence of reacting nanoparticles releasing chemical energy may bring about the same observed effects with lower estimated energy.

  3. Randomness in the bouncing ball dynamics

    NASA Astrophysics Data System (ADS)

    Giusepponi, S.; Marchesoni, F.; Borromeo, M.

    2005-06-01

    The dynamics of a vibrated bouncing ball is studied numerically in the reduced impact representation, where the velocity of the bouncing ball is sampled at each impact with the plate (asynchronous sampling). Its random nature is thus fully revealed: (i) the chattering mechanism, through which the ball gets locked on the plate, is accomplished within a limited interval of the plate oscillation phase, and (ii) is well described in impact representation by a special structure of looped, nested bands and (iii) chattering trajectories and strange attractors may coexist for appropriate ranges of the parameter values. Structure and substructure of the chattering bands are well explained in terms of a simple impact map rule. These results are of potential application to the analysis of high-temperature vibrated granular gases.

  4. On the energy characteristics of ball lightning.

    PubMed

    Bychkov, A V; Bychkov, V L; Abrahamson, John

    2002-01-15

    A compilation of 17 observations of ball lightning showing the most energetic effects is presented along with estimates of their energy content. These observations were chosen from several thousand for the much stronger interaction of each ball lightning on its surroundings, and the method of energy estimation outlined. The case is put that some of the observations show a higher energy than self-contained chemical energy could provide. Comments have been added to the paper, arguing that the energy estimations themselves should be consistent with whatever model is used for ball lightning. For example, the presence of reacting nanoparticles releasing chemical energy may bring about the same observed effects with lower estimated energy. PMID:16210173

  5. Relativistic-microwave theory of ball lightning

    NASA Astrophysics Data System (ADS)

    Wu, H.-C.

    2016-06-01

    Ball lightning, a fireball sometimes observed during lightnings, has remained unexplained. Here we present a comprehensive theory for the phenomenon: At the tip of a lightning stroke reaching the ground, a relativistic electron bunch can be produced, which in turn excites intense microwave radiation. The latter ionizes the local air and the radiation pressure evacuates the resulting plasma, forming a spherical plasma bubble that stably traps the radiation. This mechanism is verified by particle simulations. The many known properties of ball lightning, such as the occurrence site, relation to the lightning channels, appearance in aircraft, its shape, size, sound, spark, spectrum, motion, as well as the resulting injuries and damages, are also explained. Our theory suggests that ball lighting can be created in the laboratory or triggered during thunderstorms. Our results should be useful for lightning protection and aviation safety, as well as stimulate research interest in the relativistic regime of microwave physics.

  6. The bouncing ball through a geometrical series

    NASA Astrophysics Data System (ADS)

    Flores, Sergio; Alfaro, Luis L.; Chavez, Juan E.; Bastarrachea, Aztlan; Hurtado, Jazmin

    2008-10-01

    The mathematical representation of the physical situation related to a bouncing ball on the floor is an important understanding difficulty for most of the students during the introductory mechanics and mathematics courses. The research group named Physics and mathematics in context from the University of Ciudad Juarez is concerned about the versatility in the change from a mathematical representation to the own physical context of any problem under a traditional instruction. In this case, the main idea is the association of the physical properties of the bouncing ball situation to the nearest mathematical model based on a geometrical series. The proposal of the cognitive development is based on a geometrical series that shows the time the ball takes to stop. In addition, we show the behavior of the ratio of the consecutive heights during the motion.

  7. Relativistic-microwave theory of ball lightning

    PubMed Central

    Wu, H.-C.

    2016-01-01

    Ball lightning, a fireball sometimes observed during lightnings, has remained unexplained. Here we present a comprehensive theory for the phenomenon: At the tip of a lightning stroke reaching the ground, a relativistic electron bunch can be produced, which in turn excites intense microwave radiation. The latter ionizes the local air and the radiation pressure evacuates the resulting plasma, forming a spherical plasma bubble that stably traps the radiation. This mechanism is verified by particle simulations. The many known properties of ball lightning, such as the occurrence site, relation to the lightning channels, appearance in aircraft, its shape, size, sound, spark, spectrum, motion, as well as the resulting injuries and damages, are also explained. Our theory suggests that ball lighting can be created in the laboratory or triggered during thunderstorms. Our results should be useful for lightning protection and aviation safety, as well as stimulate research interest in the relativistic regime of microwave physics. PMID:27328835

  8. Drag Crisis of Gyro-Balls

    NASA Astrophysics Data System (ADS)

    Yokoyama, Yoshiyuki; Miyazaki, Takeshi; Himeno, Ryutaro

    2007-11-01

    Using a high-speed video camera, we measured the trajectory and the rotation of a hard baseball thrown by a pitching machine which can launch Gyro-Balls (rifle spinning balls). We determined the drag- and lift- coefficients by analyzing the video images. The measurements were performed in the range of 0.6x10^5ball with SP=0.12,0.23 and 0.35, decreases gradually with Re. However, the drag coefficient of a 2-seam gyro-ball with SP=0.12 decreases in two steps, i.e. in the ranges 0.8x10^5Ball with SP=0.23,0.35 are almost constant below Re=1.6x10^5 and Re=1.3x10^5, respectively. Their minima are attained at Re=1.8x10^5 and Re=1.6x10^5, respectively. These findings confirm the occurrence of the drag crisis for Gyro-Balls. The different Re-dependencies are due to the different seam patterns.

  9. A formula for comparison of selected sport ball compressibility.

    PubMed Central

    Dowell, L J; Krebs, G

    1991-01-01

    The purpose of this study was to develop a formula to determine and compare the compressibility of selected sport balls. Six balls (basketball, volleyball, soccer ball, baseball, handball, golf ball) were dropped ten times from each of four different heights onto a smooth solid surface overlaid with a white sheet of typing paper, overlaid with a sheet of carbon paper. The diameter of the area of contact of each ball imprinted onto the typing paper was measured in millimetres with calipers. From the data, the distance (d) that each ball compressed for each velocity (v) was calculated. It was found that a linear relationship existed between velocity at impact and the distance for each ball studied. The compressibility coefficient (c) for each ball was calculated and a formula was developed to determine the distance each ball would compress at a given velocity. When velocity is measured in metres per second and the distance a ball compresses is measured in millimetres, the formula to determine d for selected balls, in order of compressibility is: basketball d = 3.07v, volleyball d = 2.90v, soccer ball d = 2.80v, baseball d = 0.77v, handball d = 0.53v, and golf ball d = 0.17v. PMID:1913029

  10. A formula for comparison of selected sport ball compressibility.

    PubMed

    Dowell, L J; Krebs, G

    1991-03-01

    The purpose of this study was to develop a formula to determine and compare the compressibility of selected sport balls. Six balls (basketball, volleyball, soccer ball, baseball, handball, golf ball) were dropped ten times from each of four different heights onto a smooth solid surface overlaid with a white sheet of typing paper, overlaid with a sheet of carbon paper. The diameter of the area of contact of each ball imprinted onto the typing paper was measured in millimetres with calipers. From the data, the distance (d) that each ball compressed for each velocity (v) was calculated. It was found that a linear relationship existed between velocity at impact and the distance for each ball studied. The compressibility coefficient (c) for each ball was calculated and a formula was developed to determine the distance each ball would compress at a given velocity. When velocity is measured in metres per second and the distance a ball compresses is measured in millimetres, the formula to determine d for selected balls, in order of compressibility is: basketball d = 3.07v, volleyball d = 2.90v, soccer ball d = 2.80v, baseball d = 0.77v, handball d = 0.53v, and golf ball d = 0.17v. PMID:1913029

  11. A formula for comparison of selected sport ball compressibility.

    PubMed

    Dowell, L J; Krebs, G

    1991-03-01

    The purpose of this study was to develop a formula to determine and compare the compressibility of selected sport balls. Six balls (basketball, volleyball, soccer ball, baseball, handball, golf ball) were dropped ten times from each of four different heights onto a smooth solid surface overlaid with a white sheet of typing paper, overlaid with a sheet of carbon paper. The diameter of the area of contact of each ball imprinted onto the typing paper was measured in millimetres with calipers. From the data, the distance (d) that each ball compressed for each velocity (v) was calculated. It was found that a linear relationship existed between velocity at impact and the distance for each ball studied. The compressibility coefficient (c) for each ball was calculated and a formula was developed to determine the distance each ball would compress at a given velocity. When velocity is measured in metres per second and the distance a ball compresses is measured in millimetres, the formula to determine d for selected balls, in order of compressibility is: basketball d = 3.07v, volleyball d = 2.90v, soccer ball d = 2.80v, baseball d = 0.77v, handball d = 0.53v, and golf ball d = 0.17v.

  12. Ocular injuries from liquid golf ball cores.

    PubMed Central

    Lucas, D R; Dunham, A C; Lee, W R; Weir, W; Wilkinson, F C

    1976-01-01

    Tissue removed from nine new cases from 18 hours to 20 weeks after injury by a golf ball contained crystalline and other foreign material to which there was a mild inflammatory reaction followed by macrophagic activity and fibrosis. Optical and electron probe analysis showed that the crystalline material was crushed barytes containing small quantities of muscovite as is typical in natural deposits. The centres of several golf balls were shown to contain essentially identical material. By contrast with previous reports, no zinc sulphide was found. The form and frequent location of the deposits in the conjunctiva as compared with cornea and eyelid is related to the structure of these tissues. Images PMID:1009050

  13. Effects of Stabilization Exercise Using a Ball on Mutifidus Cross-Sectional Area in Patients with Chronic Low Back Pain

    PubMed Central

    Chung, SinHo; Lee, JuSang; Yoon, JangSoon

    2013-01-01

    The purpose of this study was to compare the effects of lumbar stabilization exercises using balls to the effects of general lumbar stabilization exercises with respect to changes in the cross section of the multifidus (MF), weight bearing, pain, and functional disorders in patients with non-specific chronic low back pain. Twelve patients participated in either a 8 week (3 days per week) stabilization exercise program using balls and control group (n = 12). The computer tomography (CT) was used to analyze MF cross-sectional areas (CSA) and Tetrax balancing scale was used to analyze left and right weight bearing differences. Both groups had significant changes in the CSA of the MF by segment after training (p < 0.05) and the experimental group showed greater increases at the L4 (F = 9.854, p = 0.005) and L5 (F = 39. 266, p = 0.000). Both groups showed significant decreases in weight bearing, from 9.25% to 5.83% in the experimental group and from 9.33% to 4.25% in the control group (p < 0.05), but did not differ significantly between the two groups. These results suggests that stabilization exercises using ball can increases in the CSA of the MF segments, improvement in weight bearing, pain relief, and recovery from functional disorders, and the increases in the CSA of the MF of the L4 and L5 segments for patients with low back pain. Key Points Compared with the stabilization exercise using a ball and general stabilization exercise increased the CSA of the MF, weight bearing, pain, and functional ability in patients with low back pain. We verified that increases in the CSA of the MF of the L4 and L5 segments and functional ability during the stabilization exercise using a ball. The stabilization exercise using a ball was shown to be an effective exercise method for patients with low back pain in a rehabilitation program by increasing functional ability and the CSA of the MF. PMID:24149162

  14. History of Space Shuttle Main Engine Turbopump Bearing Testing at the Marshall Space Flight Center

    NASA Technical Reports Server (NTRS)

    Gibson, Howard; Thom, Robert; Moore, Chip; Haluck, Dave

    2010-01-01

    The Space Shuttle is propelled into orbit by two solid rocket motors and three liquid fed main engines. After the solid motors fall away, the shuttle engines continue to run for a total time of 8 minutes. These engines are fed propellants by low and high pressure turbopumps. A critical part of the turbopump is the main shaft that supports the drive turbine and the pump inducer and impeller. Rolling element bearings hold the shaft in place during rotation. If the bearings were to fail, the shaft would move, allowing components to rub in a liquid oxygen or hydrogen environment, which could have catastrophic results. These bearings are required to spin at very high speeds, support radial and axial loads, and have high wear resistance without the benefit of a conventional means of lubrication. The Rocketdyne built Shuttle turbopumps demonstrated their capability to perform during launches; however, the seven hour life requirement was not being met. One of the limiting factors was the bearings. In the late 1970's, an engineering team was formed at the Marshall Space Flight Center (MSFC), to develop a test rig and plan for testing the Shuttle s main engine high pressure oxygen turbopump (HPOTP) bearings. The goals of the program were to better understand the operation of bearings in a cryogenic environment and to further develop and refine existing computer models used to predict the operational limits of these bearings. In 1982, testing began in a rig named the Bearing and Seal Material Tester or BSMT as it was commonly called. The first testing investigated the thermal margin and thermal runaway limits of the HPOTP bearings. The test rig was later used to explore potential bearing improvements in the area of increased race curvatures, new cage materials for better lubrication, new wear resistant rolling element materials, and other ideas to improve wear life. The most notable improvements during this tester s time was the incorporation of silicon nitride balls and

  15. Levitation of an iron ball in midair without active control

    NASA Astrophysics Data System (ADS)

    Sasaki, S.; Yagi, I.; Murakami, M.

    2004-02-01

    An iron ball floats in midair in a plastic box when several iron balls were attracted by a permanent magnet. A complex interaction between magnetized sphere materials and a lifting magnet enabled the suspension of an iron ball. The balls in the first row are simply attracted by the lifting magnet. The ball in the second row is also attracted by the lifting magnet, however, due to the repulsive forces exerted from the balls sitting above, it can float in midair. We also found that there are two stable positions for the ball to float. The floating ball could be transported from one equilibrium position to another by simply rotating the lifting magnet. This will make it possible to construct a noncontact load transport device.

  16. A Momentum Transfer Demonstration with "Happy/Unhappy" Balls.

    ERIC Educational Resources Information Center

    Bucheit, Fred

    1994-01-01

    Describes a simple setup and procedure that uses "happy/unhappy" balls (two balls with different degrees of elasticity) to lead students into a discussion of momentum transfer involving elastic and inelastic collisions. (ZWH)

  17. Tennis ball fuzziness: assessing textile surface roughness using digital imaging

    NASA Astrophysics Data System (ADS)

    Steele, C.; Jones, R.; Leaney, P. G.

    2006-06-01

    Wear plays an important role in the game of tennis as it affects both ball performance and player perceived ball quality. Visual appearance can be used in ball differentiation, but has so far been limited to subjective assessments used to estimate ball wear and performance characteristics. A metric for ball surface condition will allow performance and perception data from varied testing set-ups to be objectively compared and analysed. A versatile new method of assessing surface roughness using digital imaging has been developed to allow the quantitative assessment of tennis ball condition. This metric allows manufacturers and researchers to predict ball performance and player perception from worn ball samples, developing acceptable wear limits. In the successful implementation of this metric, several key factors, including lighting, image thresholding, algorithm implementation and camera specifications, were identified to aid future alternative implementations.

  18. Experiments with needle bearings

    NASA Technical Reports Server (NTRS)

    Ferretti, Pericle

    1933-01-01

    Experiments and results are presented in testing needle bearings, especially in comparison with roller bearings. Reduction in coefficient of friction is discussed as well as experimental methods and recording devices.

  19. Axial Halbach Magnetic Bearings

    NASA Technical Reports Server (NTRS)

    Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.

    2008-01-01

    Axial Halbach magnetic bearings have been investigated as part of an effort to develop increasingly reliable noncontact bearings for future high-speed rotary machines that may be used in such applications as aircraft, industrial, and land-vehicle power systems and in some medical and scientific instrumentation systems. Axial Halbach magnetic bearings are passive in the sense that unlike most other magnetic bearings that have been developed in recent years, they effect stable magnetic levitation without need for complex active control.

  20. Calibration of industrial CT using two forest-balls

    NASA Astrophysics Data System (ADS)

    Shi, Yushu; Song, Xu; Li, Shi; Li, Wei; Li, Qi; Chen, Siwen; Shen, Fei; Song, Xiaoping; Gao, Sitian

    2015-02-01

    A small forest-ball was manufactured and calibrated using CMM F25. An industrial CT called Metrotom1500 was calibrated by the small forest-ball and another big forest-ball produced by Carl Zeiss. These two forest-balls were separately measured at two different magnifications of the industrial CT, and the measurement results could meet the maximum permissible error of Metrotom1500.

  1. Computed Tomography Analysis of NASA BSTRA Balls

    SciTech Connect

    Perry, R L; Schneberk, D J; Thompson, R R

    2004-10-12

    Fifteen 1.25 inch BSTRA balls were scanned with the high energy computed tomography system at LLNL. This system has a resolution limit of approximately 210 microns. A threshold of 238 microns (two voxels) was used, and no anomalies at or greater than this were observed.

  2. Spherical polytropic balls cannot mimic black holes

    NASA Astrophysics Data System (ADS)

    Saida, Hiromi; Fujisawa, Atsuhito; Yoo, Chul-Moon; Nambu, Yasusada

    2016-04-01

    The so-called black hole shadow is a dark region which is expected to appear in a fine image of optical observation of black holes. It is essentially an absorption cross section of the black hole, and the boundary of shadow is determined by unstable circular orbits of photons (UCOP). If there exists a compact object possessing UCOP but no black hole horizon, it can provide us with the same shadow image as black holes, and detection of a shadow image cannot be direct evidence of black hole existence. This paper examines whether or not such compact objects can exist under some suitable conditions. We investigate thoroughly the static spherical polytropic ball of perfect fluid with single polytrope index, and then investigate a representative example of a piecewise polytropic ball. Our result is that the spherical polytropic ball which we have investigated cannot possess UCOP, if the speed of sound at the center is subluminal (slower than light). This means that, if the polytrope treated in this paper is a good model of stellar matter in compact objects, the detection of a shadow image can be regarded as good evidence of black hole existence. As a by-product, we have found the upper bound of the mass-to-radius ratio of a polytropic ball with single index, M_{ast }/R_{ast } < 0.281, under the condition of subluminal sound speed.

  3. Introducing a High Bounce Ball Unit

    ERIC Educational Resources Information Center

    Bernardo, Pat

    2004-01-01

    Those growing up in the 1950s, 60s or 70s are familiar with how physically active children were before computers and video games were introduced. Each neighborhood had its own version of the various games that were played. Many of these games involved a pink rubber ball called a Spaldeen. They were everywhere and almost everyone had one. These…

  4. Exploring the Mathematics of Bouncing Balls

    ERIC Educational Resources Information Center

    Vinogradova, Natalya; Blaine, Larry G.

    2010-01-01

    A common textbook problem asks students to calculate the total distance traveled by a bouncing ball, from its initial release until it comes to rest, under the assumption that the height of each bounce is some fixed proportion "r" of the height of the previous bounce. The solution is found by inserting information about "r" and the height from…

  5. Heat-balling wasps by honeybees

    NASA Astrophysics Data System (ADS)

    Ken, Tan; Hepburn, H. R.; Radloff, S. E.; Yusheng, Yu; Yiqiu, Liu; Danyin, Zhou; Neumann, P.

    2005-10-01

    Defensiveness of honeybee colonies of Apis cerana and Apis mellifera (actively balling the wasps but reduction of foraging) against predatory wasps, Vespa velutina, and false wasps was assessed. There were significantly more worker bees in balls of the former than latter. Core temperatures in a ball around a live wasp of A. cerana were significantly higher than those of A. mellifera, and also significantly more when exposed to false wasps. Core temperatures of bee balls exposed to false wasps were significantly lower than those exposed to V. velutina for both A. cerana and for A. mellifera. The lethal thermal limits for V. velutina, A. cerana and A. mellifera were significantly different, so that both species of honeybees have a thermal safety factor in heat-killing such wasp predators. During wasps attacks at the hives measured at 3, 6 and 12 min, the numbers of Apis cerana cerana and Apis cerana indica bees continuing to forage were significantly reduced with increased wasp attack time. Tropical lowland A. c. indica reduced foraging rates significantly more than the highland A. c. cerana bees; but, there was no significant effect on foraging by A. mellifera. The latency to recovery of honeybee foraging was significantly greater the longer the duration of wasp attacks. The results show remarkable thermal fine-tuning in a co-evolving predator prey relationship.

  6. Department of Natural Resources, Ball State University.

    ERIC Educational Resources Information Center

    Hibbs, Clyde W.

    1987-01-01

    Describes the environmental education programs of Ball State University's Department of Natural Resources. Focusing on natural resource science and technology, the program has thrusts in resource conservation, environmental protection, and environmental education. Outlines the program goals, courses, curricular patterns, graduate programs, and…

  7. 4. pi. physics with the plastic ball

    SciTech Connect

    Gutbrod, H.H.; Loehner, H.; Poskanzer, A.M.; Renner, T.; Riedesel, H.; Ritter, H.G.; Warwick, A.; Weik, F.; Wieman, H.

    1982-10-01

    4 ..pi.. data taken with the Plastic Ball show that cluster production in relativistic nuclear collisions depends on both the size of the participant volume and the finite size of the cluster. The measurement of the degree of thermalization and the search for collective flow will permit the study of the applicability of macroscopic concepts such as temperature and density.

  8. When Two Balls Are Just One

    ERIC Educational Resources Information Center

    Kulp, Christopher W.; Biermann, Mark L.; Howard, Timothy; Klingenberg, Kurtis; Ramsey, Paul

    2008-01-01

    A camcorder can be a powerful tool in pedagogical settings, such as in an introductory physics course or in introducing undergraduates to data collection. In this paper, we discuss our experience using a Panasonic PV-GS150 digital camcorder to analyze the motion of a falling steel ball, with the goal of determining the acceleration due to gravity,…

  9. Construction of the noncommutative complex ball

    SciTech Connect

    Wang, Zhituo

    2014-09-15

    We describe the construction of the noncommutative complex ball whose commutative analog is the Hermitian symmetric space D = SU(m, 1)/U(m), with the method of coherent state quantization. In the commutative limit, we obtain the standard manifold. We also consider a quantum field theory model on the noncommutative manifold.

  10. Two experimental investigations of ball lightning

    NASA Astrophysics Data System (ADS)

    Alexeff, Igor; Parameswaran, Sriram; Grace, Michael

    2004-11-01

    We have carried out two experiments that appear to produce ball lightning in the laboratory. The first set of observations were made at the Holifield high voltage accelerator at the Oak Ridge National Laboratory (1). In these experiments at very high voltage, closed current loops were photographed in high voltage sparkovers. These may be current loops sustained by the enclosed magnetic field. In the second set of experiments, a pulsed electric arc in a zero - gravity environment produced orange balls in atmospheric - pressure air that persisted for over 1/2 second after power turn - off (2). These balls were photographed with a high - speed 16 mm movie camera. Photos and movies of these experiments will be presented. 1. "Observation of Closed Loops in High-Voltage Discharges: A Possible Precursor of Magnetic Flux Trapping", Igor Alexeff and Mark Rader, IEEE Transactions on Plasma Science, Vol. 20, No. 6, December 1992, pp.669 - 671: ``Possible Precursors of Ball Lightning--Observation of Closed Loops in High- Voltage Discharges,'' Igor Alexeff and Mark Rader, Fusion Technology, Vol. 27, May 1995, pp 271 - 273 2. I. Alexeff et. al., Invited paper at The International Conference on Plasma Science, Preceedings of the Conference, Baltimore, Md., June 2004.

  11. The dynamic behavior of squash balls

    NASA Astrophysics Data System (ADS)

    Lewis, Gareth J.; Arnold, J. Cris; Griffiths, Iwan W.

    2011-03-01

    The behavior of a squash ball constitutes an excellent case study of the dynamic behavior of rubbery materials. It is shown that the complex viscoelastic behavior of rubber can be investigated using simple drop bounce tests and compression tests. The drop tests show that the coefficient of restitution increases as the ball temperature increases. The compression tests show that as the speed of compression increases or as the ball temperature decreases, the compressive force and the energy loss both increase. These effects are due to the viscoelastic nature of the rubber and are an excellent example of the time-temperature equivalence of polymers. Compression tests were performed on balls with small holes at the base to separate the effects of the internal air pressure from the material deformation. It was found that the internal air pressure contributed about one-third to the compressive force, but contributed little to energy loss. This behavior shows that the rubber material dominates the rebound behavior and that the normal warming up process at the start of a squash game is important to raise the temperature of the rubber rather than to increase the internal air pressure.

  12. CFD analysis of a ball check microvalve

    NASA Astrophysics Data System (ADS)

    Cǎlimǎnescu, Ioan; Dumitrache, Constantin L.; Grigorescu, Lucian

    2015-02-01

    The microvalves with balls as seen before are used in many applications and their behaviour in terms of fluid dynamics mainly at their opening time (when as demonstrated the ball is bouncing up and down altering the flow parameters) is of a paramount importance. The present study is focused on a micro check ball valve circulating a fluid air-like (with the same constant proprieties). The CFD model is taking into account a transitory zone of functioning from zero time when the pressure inside a "tank" is reaching the opening pressure of the valve, to the final step 0.05 seconds when the ball is stabilizing after bouncing up and down. The geometry of the valve with dimensions in μm is given below (the model is comprising a "slice" of 5 μm thickness extracted from the entire valve. In this paper by using advanced numeric techniques, the behavior of the valve in its transitory opening stage was studied with credible and useful results for further optimisation studies.

  13. Sharpening ball-nose mill cutters

    NASA Technical Reports Server (NTRS)

    Burch, C. F.

    1977-01-01

    Economical attachment allows faster, more precise grinding. Vibrationless and rigid relation between grinding wheel and cutter allows for extremely high finish and accurate grinding. Leveling device levels flutes with respect to toolholder rotation that generates ball-nose radius. Constant relief around entire profile of cutting edge produces longer tool life.

  14. Fractal Aggregates in Tennis Ball Systems

    ERIC Educational Resources Information Center

    Sabin, J.; Bandin, M.; Prieto, G.; Sarmiento, F.

    2009-01-01

    We present a new practical exercise to explain the mechanisms of aggregation of some colloids which are otherwise not easy to understand. We have used tennis balls to simulate, in a visual way, the aggregation of colloids under reaction-limited colloid aggregation (RLCA) and diffusion-limited colloid aggregation (DLCA) regimes. We have used the…

  15. Crystal Ball results on tau decays

    SciTech Connect

    Lowe, S.T.

    1987-10-01

    This report reviews measurements and upper limit determinations for a number of exclusive 1-prong tau decay modes using the Crystal Ball detector. These results are important input to the apparent discrepancy between the topological and sum-of-exclusive branching fractions in 1-prong tau decays.

  16. Recent results from the Crystal Ball experiment

    SciTech Connect

    Lowe, S.T.

    1986-12-01

    Several recent analyses from the Crystal Ball collaboration are reviewed. The major topics discussed are the search for new states in radiative UPSILON(1S) decays, the search for lepton number-violating and inclusive eta decay modes of the tau, and results from ..gamma gamma.. physics.

  17. Interrelation between ball lightning and optically induced forces

    NASA Astrophysics Data System (ADS)

    Torchigin, V. P.; Torchigin, A. V.

    2013-09-01

    Optically induced forces are considered as a key factor for explaining the phenomenon of ball lightning. They can provide not only the existence of ball lightning in the form of self-confined intense white light circulating in a spherical shell of air strongly compressed by the light but also the anomalous motion of ball lightning in the terrestrial atmosphere.

  18. Validity and Reliability of a Medicine Ball Explosive Power Test.

    ERIC Educational Resources Information Center

    Stockbrugger, Barry A.; Haennel, Robert G.

    2001-01-01

    Evaluated the validity and reliability of a medicine ball throw test to evaluate explosive power. Data on competitive sand volleyball players who performed a medicine ball throw and a standard countermovement jump indicated that the medicine ball throw test was a valid and reliable way to assess explosive power for an analogous total-body movement…

  19. Measuring the Rebound Resilience of a Bouncing Ball

    ERIC Educational Resources Information Center

    Wadhwa, Ajay

    2012-01-01

    Some balls which are made of high-quality rubber (an elastomeric) material, such as tennis or squash balls, could be used for the determination of an important property of such materials called resilience. Since a bouncing ball involves a single impact we call this property "rebound resilience" and express it as the ratio of the rebound height to…

  20. Magnetically Operated Holding Plate And Ball-Lock Pin

    NASA Technical Reports Server (NTRS)

    Monford, Leo G., Jr.

    1992-01-01

    Magnetically operated holding plate and ball-locking-pin mechanism part of object attached to, or detached from second object. Mechanism includes tubular housing inserted in hole in second object. Plunger moves inside tube forcing balls to protrude from sides. Balls prevent tube from sliding out of second object. Simpler, less expensive than motorized latches; suitable for robotics applications.

  1. METHODOLOGICAL NOTES: Energy density calculations for ball-lightning-like luminous silicon balls

    NASA Astrophysics Data System (ADS)

    Paiva, Gerson S.; Ferreira, Joacy V.; Bastos, Cristiano C.; dos Santos, Marcus V.; Pavão, Antonio C.

    2010-05-01

    The energy density of a luminous silicon ball [Phys. Rev. Lett. 98 048501 (2007)] is calculated for a model with a metal core surrounded by an atmosphere of silicon oxides. Experimental data combined with the molecular orbital calculations of the oxidation enthalpy lead to a mean energy density of 3.9 MJ m-3, which is within the range of estimates from other ball lightning models. This result provides good evidence to support the silicon-based model.

  2. Formation of nickel cobalt sulfide ball-in-ball hollow spheres with enhanced electrochemical pseudocapacitive properties.

    PubMed

    Shen, Laifa; Yu, Le; Wu, Hao Bin; Yu, Xin-Yao; Zhang, Xiaogang; Lou, Xiong Wen David

    2015-03-23

    While the synthesis of hollow structures of transition metal oxides is well established, it is extremely challenging to fabricate complex hollow structures for mixed transition metal sulfides. Here we report an anion exchange method to synthesize a complex ternary metal sulfides hollow structure, namely nickel cobalt sulfide ball-in-ball hollow spheres. Uniform nickel cobalt glycerate solid spheres are first synthesized as the precursor and subsequently chemically transformed into nickel cobalt sulfide ball-in-ball hollow spheres. When used as electrode materials for electrochemical capacitors, these nickel cobalt sulfide hollow spheres deliver a specific capacitance of 1,036 F g(-1) at a current density of 1.0 A g(-1). An asymmetric supercapacitor based on these ball-in-ball structures shows long-term cycling performance with a high energy density of 42.3 Wh kg(-1) at a power density of 476 W kg(-1), suggesting their potential application in high-performance electrochemical capacitors.

  3. Formation of nickel cobalt sulfide ball-in-ball hollow spheres with enhanced electrochemical pseudocapacitive properties.

    PubMed

    Shen, Laifa; Yu, Le; Wu, Hao Bin; Yu, Xin-Yao; Zhang, Xiaogang; Lou, Xiong Wen David

    2015-01-01

    While the synthesis of hollow structures of transition metal oxides is well established, it is extremely challenging to fabricate complex hollow structures for mixed transition metal sulfides. Here we report an anion exchange method to synthesize a complex ternary metal sulfides hollow structure, namely nickel cobalt sulfide ball-in-ball hollow spheres. Uniform nickel cobalt glycerate solid spheres are first synthesized as the precursor and subsequently chemically transformed into nickel cobalt sulfide ball-in-ball hollow spheres. When used as electrode materials for electrochemical capacitors, these nickel cobalt sulfide hollow spheres deliver a specific capacitance of 1,036 F g(-1) at a current density of 1.0 A g(-1). An asymmetric supercapacitor based on these ball-in-ball structures shows long-term cycling performance with a high energy density of 42.3 Wh kg(-1) at a power density of 476 W kg(-1), suggesting their potential application in high-performance electrochemical capacitors. PMID:25798849

  4. Space Shuttle Body Flap Actuator Bearing Testing for NASA Return to Flight

    NASA Technical Reports Server (NTRS)

    Jet, Timothy R.; Predmore, Roamer E.; Dube, Michael; Jones, William R., Jr.

    2006-01-01

    The Space Shuttle body flap (BF) is located beneath the main engine nozzles and is required for proper aerodynamic control during orbital descent. The body flap is controlled by four actuators connected by a common shaft and driven by the hydraulic power drive unit. Inspection of the actuators during refurbishment revealed three shaft bearings with unexpected damage. One was coated with black oxide on the balls and race wear surfaces, a second contained a relatively deep wear scar, and the third with scratches and an aluminum particle in the wear track. A shaft bearing life test program was initiated to measure the wear life and explain the 5.08-micrometer wear scar. A tribological analysis was conducted to demonstrate that the black oxide coated wear surfaces did not damage the bearing, interfere with the lubrication, or cause severe bearing wear. Pre-damaged (equivalent of 30 missions), commercial equivalent bearings and previously flown shaft bearings were tested at axial loads, speeds, and temperatures seen during flight operations. These bearing were successfully life tested at 60 C for 24 hours or 90 flights. With a safety factor of 4X, the bearings were qualified for 22 flights when only a maximum of 12 flights are expected. Additional testing at 23 C was performed to determine the lubricant life and to further understand the mechanism that caused the blackened balls. Test results indicating bearing life was shortened at a lower temperature surprised the investigators. Start\\Stop bearing testing that closely simulates mission profile was conducted at 23 C. Results of this testing showed lubricant life of 12 flights including a safety factor of four. Additional testing with bearings that have the equivalent of 30 missions of damage is being tested at 23 C. These tests are being performed over the Shuttle load profile to demonstrate the residual bearing life in the actuators exceeds 12 missions. Testing showed that the end of the shaft bearing life was

  5. The strange flight behaviour of slowly spinning soccer balls

    NASA Astrophysics Data System (ADS)

    Mizota, Taketo; Kurogi, Kouhei; Ohya, Yuji; Okajima, Atsushi; Naruo, Takeshi; Kawamura, Yoshiyuki

    2013-05-01

    The strange three-dimensional flight behaviour of slowly spinning soccer balls is one of the most interesting and unknown phenomenon associated with the trajectories of sports balls. Many spectators have experienced numerous exciting and emotional instances while observing the curious flight behaviour of these balls. We examine the aerodynamic mechanisms of erratic ball behaviours through real flight observations, unsteady force measurements and flow pattern visualisations. The strange behaviour is elucidated by the relationship between the unsteady forces on the ball and the wake flow. The irregular changes in position for twin longitudinal vortices have already been discovered in the supercritical Reynolds number region of a sphere with a smooth surface. This finding is applicable to the strange behaviour of the flight of soccer balls with this supercritical flow. The players, spectators, and television viewers will gain greater insight into the effects of soccer ball flights.

  6. The strange flight behaviour of slowly spinning soccer balls.

    PubMed

    Mizota, Taketo; Kurogi, Kouhei; Ohya, Yuji; Okajima, Atsushi; Naruo, Takeshi; Kawamura, Yoshiyuki

    2013-01-01

    The strange three-dimensional flight behaviour of slowly spinning soccer balls is one of the most interesting and unknown phenomenon associated with the trajectories of sports balls. Many spectators have experienced numerous exciting and emotional instances while observing the curious flight behaviour of these balls. We examine the aerodynamic mechanisms of erratic ball behaviours through real flight observations, unsteady force measurements and flow pattern visualisations. The strange behaviour is elucidated by the relationship between the unsteady forces on the ball and the wake flow. The irregular changes in position for twin longitudinal vortices have already been discovered in the supercritical Reynolds number region of a sphere with a smooth surface. This finding is applicable to the strange behaviour of the flight of soccer balls with this supercritical flow. The players, spectators, and television viewers will gain greater insight into the effects of soccer ball flights. PMID:23695000

  7. The strange flight behaviour of slowly spinning soccer balls

    PubMed Central

    Mizota, Taketo; Kurogi, Kouhei; Ohya, Yuji; Okajima, Atsushi; Naruo, Takeshi; Kawamura, Yoshiyuki

    2013-01-01

    The strange three-dimensional flight behaviour of slowly spinning soccer balls is one of the most interesting and unknown phenomenon associated with the trajectories of sports balls. Many spectators have experienced numerous exciting and emotional instances while observing the curious flight behaviour of these balls. We examine the aerodynamic mechanisms of erratic ball behaviours through real flight observations, unsteady force measurements and flow pattern visualisations. The strange behaviour is elucidated by the relationship between the unsteady forces on the ball and the wake flow. The irregular changes in position for twin longitudinal vortices have already been discovered in the supercritical Reynolds number region of a sphere with a smooth surface. This finding is applicable to the strange behaviour of the flight of soccer balls with this supercritical flow. The players, spectators, and television viewers will gain greater insight into the effects of soccer ball flights. PMID:23695000

  8. Measuring the rebound resilience of a bouncing ball

    NASA Astrophysics Data System (ADS)

    Wadhwa, Ajay

    2012-09-01

    Some balls which are made of high-quality rubber (an elastomeric) material, such as tennis or squash balls, could be used for the determination of an important property of such materials called resilience. Since a bouncing ball involves a single impact we call this property 'rebound resilience' and express it as the ratio of the rebound height to the initial drop height of the ball. We determine the rebound resilience for three different types of ball by calculating the coefficient of restitution of the ball-surface combination from the experimentally measurable physical quantities, such as initial drop height and time interval between successive bounces. Using these we also determine the contact time of balls with the surface of impact. For measurements we have used audio, motion and surface-temperature sensors that were interfaced through a USB port with a computer.

  9. The Moment of Inertia of a Tennis Ball

    NASA Astrophysics Data System (ADS)

    Brody, Howard

    2005-11-01

    The moment of inertia of a tennis ball about its center of mass is one of the physical properties that determine how the ball reacts in play, yet there is no measurement of this parameter found in the literature nor is it mentioned in the Rules of Tennis. The moment of inertia determines how much spin the ball acquires for a given angular impulse applied by the racket's strings and also how the ball behaves when it bounces. When a ball bounces, the friction between the ball and the court surface produces a substantial torque. For a given torque, the magnitude of the moment of inertia determines whether the ball slides throughout the bounce or goes into the rolling mode, and if it does roll, the moment of inertia determines the ratio of final horizontal velocity to initial horizontal velocity.

  10. Rotorcraft Transmission Noise Path Model, Including Distributed Fluid Film Bearing Impedance Modeling

    NASA Technical Reports Server (NTRS)

    Hambric, Stephen A.; Hanford, Amanda D.; Shepherd, Micah R.; Campbell, Robert L.; Smith, Edward C.

    2010-01-01

    A computational approach for simulating the effects of rolling element and journal bearings on the vibration and sound transmission through gearboxes has been demonstrated. The approach, using ARL/Penn State s CHAMP methodology, uses Component Mode Synthesis of housing and shafting modes computed using Finite Element (FE) models to allow for rapid adjustment of bearing impedances in gearbox models. The approach has been demonstrated on NASA GRC s test gearbox with three different bearing configurations: in the first condition, traditional rolling element (ball and roller) bearings were installed, and in the second and third conditions, the traditional bearings were replaced with journal and wave bearings (wave bearings are journal bearings with a multi-lobed wave pattern on the bearing surface). A methodology for computing the stiffnesses and damping in journal and wave bearings has been presented, and demonstrated for the journal and wave bearings used in the NASA GRC test gearbox. The FE model of the gearbox, along with the rolling element bearing coupling impedances, was analyzed to compute dynamic transfer functions between forces applied to the meshing gears and accelerations on the gearbox housing, including several locations near the bearings. A Boundary Element (BE) acoustic model was used to compute the sound radiated by the gearbox. Measurements of the Gear Mesh Frequency (GMF) tones were made by NASA GRC at several operational speeds for the rolling element and journal bearing gearbox configurations. Both the measurements and the CHAMP numerical model indicate that the journal bearings reduce vibration and noise for the second harmonic of the gear meshing tones, but show no clear benefit to using journal bearings to reduce the amplitudes of the fundamental gear meshing tones. Also, the numerical model shows that the gearbox vibrations and radiated sound are similar for journal and wave bearing configurations.

  11. Perceptual elements in Penn & Teller's "Cups and Balls" magic trick.

    PubMed

    Rieiro, Hector; Martinez-Conde, Susana; Macknik, Stephen L

    2013-01-01

    Magic illusions provide the perceptual and cognitive scientist with a toolbox of experimental manipulations and testable hypotheses about the building blocks of conscious experience. Here we studied several sleight-of-hand manipulations in the performance of the classic "Cups and Balls" magic trick (where balls appear and disappear inside upside-down opaque cups). We examined a version inspired by the entertainment duo Penn & Teller, conducted with three opaque and subsequently with three transparent cups. Magician Teller used his right hand to load (i.e. introduce surreptitiously) a small ball inside each of two upside-down cups, one at a time, while using his left hand to remove a different ball from the upside-down bottom of the cup. The sleight at the third cup involved one of six manipulations: (a) standard maneuver, (b) standard maneuver without a third ball, (c) ball placed on the table, (d) ball lifted, (e) ball dropped to the floor, and (f) ball stuck to the cup. Seven subjects watched the videos of the performances while reporting, via button press, whenever balls were removed from the cups/table (button "1") or placed inside the cups/on the table (button "2"). Subjects' perception was more accurate with transparent than with opaque cups. Perceptual performance was worse for the conditions where the ball was placed on the table, or stuck to the cup, than for the standard maneuver. The condition in which the ball was lifted displaced the subjects' gaze position the most, whereas the condition in which there was no ball caused the smallest gaze displacement. Training improved the subjects' perceptual performance. Occlusion of the magician's face did not affect the subjects' perception, suggesting that gaze misdirection does not play a strong role in the Cups and Balls illusion. Our results have implications for how to optimize the performance of this classic magic trick, and for the types of hand and object motion that maximize magic misdirection.

  12. Detailed study of oxidation/wear mechanism in lox turbopump bearings

    NASA Technical Reports Server (NTRS)

    Chase, T. J.; Mccarty, J. P.

    1993-01-01

    Wear of 440C angular contact ball bearings of the phase 2 high pressure oxygen turbopump (HPOTP) of the space shuttle main engine (SSME) has been studied by means of various advanced nondestructive techniques (NDT) and modeled with reference to all known material, design, and operation variables. Three modes dominating the wear scenario were found to be the adhesive/sheer peeling (ASP), oxidation, and abrasion. Bearing wear was modeled in terms of the three modes. Lacking a comprehensive theory of rolling contact wear to date, each mode is modeled after well-established theories of sliding wear, while sliding velocity and distance are related to microsliding in ball-to-ring contacts. Microsliding, stress, temperature, and other contact variables are evaluated with analytical software packages of SHABERTH(TM)/SINDA(TM) and ADORE(TM). Empirical constants for the models are derived from NIST experiments by applying the models to the NIST wear data. The bearing wear model so established precisely predicts quite well the average ball wear rate for the HPOTP bearings. The wear rate has been statistically determined for the entire population of flight and development bearings based on Rocketdyne records to date. Numerous illustrations are given.

  13. Detailed study of oxidation/wear mechanism in lox turbopump bearings

    NASA Astrophysics Data System (ADS)

    Chase, T. J.; McCarty, J. P.

    1993-12-01

    Wear of 440C angular contact ball bearings of the phase 2 high pressure oxygen turbopump (HPOTP) of the space shuttle main engine (SSME) has been studied by means of various advanced nondestructive techniques (NDT) and modeled with reference to all known material, design, and operation variables. Three modes dominating the wear scenario were found to be the adhesive/sheer peeling (ASP), oxidation, and abrasion. Bearing wear was modeled in terms of the three modes. Lacking a comprehensive theory of rolling contact wear to date, each mode is modeled after well-established theories of sliding wear, while sliding velocity and distance are related to microsliding in ball-to-ring contacts. Microsliding, stress, temperature, and other contact variables are evaluated with analytical software packages of SHABERTH(TM)/SINDA(TM) and ADORE(TM). Empirical constants for the models are derived from NIST experiments by applying the models to the NIST wear data. The bearing wear model so established precisely predicts quite well the average ball wear rate for the HPOTP bearings. The wear rate has been statistically determined for the entire population of flight and development bearings based on Rocketdyne records to date. Numerous illustrations are given.

  14. Some limitations in applying classical EHD film-thickness formulae to a high-speed bearing

    NASA Technical Reports Server (NTRS)

    Coy, J. J.; Zaretsky, E. V.

    1980-01-01

    Elastohydrodynamic film thickness was measured for a 20 mm ball bearing using the capacitance technique. The bearing was thrust loaded to 90, 448, and 778 N. The corresponding maximum stresses on the inner race were 1.28, 2.09, and 2.45 GPa. Test speeds ranged from 400 to 14,000 rpm. Film thickness measurements were taken with four different lubricants: (1) synthetic paraffinic; (2) synthetic paraffinic with additives; (3) neopentylpolyol (tetra) ester; and (4) synthetic cycloaliphatic hydrocarbon traction fluid. The test bearing was mist lubricated. Test temperatures were 300, 338, and 393 K. The measured results were compared to theoretical predictions and are presented.

  15. The effect of solid film lubricants on the stability of rolling element bearings

    NASA Technical Reports Server (NTRS)

    Kannel, J. W.; Merriman, T. L.

    1987-01-01

    A technique has been developed for modeling solid films in rolling element bearings. For a given bearing geometry an effective viscosity can be calculated for a solid film as a function of the film shear modulus and ball-race friction coefficient. The calculated effective viscosity can subsequently be used as an input to a numerical model of cage motion and stability. Results from a sample calculation of effective viscosity and prediction of cage stability for a turbopump bearing are presented for films of molybdenum disulfide (MoS2) and polytetrafluoroethylene ()PTFE).

  16. Relative locality and the soccer ball problem

    SciTech Connect

    Amelino-Camelia, Giovanni; Freidel, Laurent; Smolin, Lee; Kowalski-Glikman, Jerzy

    2011-10-15

    We consider the behavior of macroscopic bodies within the framework of relative locality [G. Amelino-Camelia, L. Freidel, J. Kowalski-Glikman, and L. Smolin, arXiv:1101.0931]. This is a recent proposal for Planck scale modifications of the relativistic dynamics of particles which are described as arising from deformations in the geometry of momentum space. We consider and resolve a common objection against such proposals, which is that, even if the corrections are small for elementary particles in current experiments, they are huge when applied to composite systems such as soccer balls, planets, and stars, with energies E{sub macro} much larger than M{sub P}. We show that this soccer ball problem does not arise within the framework of relative locality because the nonlinear effects for the dynamics of a composite system with N elementary particles appear at most of order E{sub macro}/N{center_dot}M{sub P}.

  17. Symmetric States on the Octonionic Bloch Ball

    NASA Astrophysics Data System (ADS)

    Graydon, Matthew

    2012-02-01

    Finite-dimensional homogeneous self-dual cones arise as natural candidates for convex sets of states and effects in a variety of approaches towards understanding the foundations of quantum theory in terms of information-theoretic concepts. The positive cone of the ten-dimensional Jordan-algebraic spin factor is one particular instantiation of such a convex set in generalized frameworks for quantum theory. We consider a projection of the regular 9-simplex onto the octonionic projective line to form a highly symmetric structure of ten octonionic quantum states on the surface of the octonionic Bloch ball. A uniform subnormalization of these ten symmetric states yields a symmetric informationally complete octonionic quantum measurement. We discuss a Quantum Bayesian reformulation of octonionic quantum formalism for the description of two-dimensional physical systems. We also describe a canonical embedding of the octonionic Bloch ball into an ambient space for states in usual complex quantum theory.

  18. Gravitational effects on critical Q-balls

    NASA Astrophysics Data System (ADS)

    Metaxas, D.

    2007-04-01

    In a cosmological phase transition in theories that admit Q-balls there is a value of the soliton charge above which the soliton becomes unstable and expands, converting space to the true vacuum, much like a critical bubble in the case of ordinary tunneling. Here I consider the effects of gravity on these solitons and I calculate the lowest gravitational corrections to the critical radius and charge.

  19. Testing general relativity using a bouncing ball

    NASA Astrophysics Data System (ADS)

    Liang, Shiuan-Ni; Lan, Boon Leong

    In a recent article (Liang and Lan, (2011)), we showed that the trajectories predicted by general-relativistic and Newtonian mechanics from the same parameters and initial conditions for a low-speed weak-gravity bouncing ball system will rapidly disagree completely if the trajectories are chaotic. Here, we determine how accurate the parameters and initial conditions of the system must be known so that the two different calculated chaotic trajectories are sufficiently accurate for an empirical test.

  20. Ball-thrower's fracture of the humerus.

    PubMed

    Callaghan, Eric B; Bennett, D Lee; El-Khoury, Georges Y; Ohashi, Kenjirou

    2004-06-01

    A relatively rare case of ball-thrower's fracture of the humerus is presented. Severe muscular action is an uncommon cause of humeral fractures but has been well documented in the orthopedic literature. To our knowledge, this fracture has not been described in the radiology literature, and awareness of this entity could preclude further unnecessary workup. The mechanism of injury and its typical radiographic appearance is described.

  1. Free-floating atmospheric pressure ball plasmas

    NASA Astrophysics Data System (ADS)

    Wurden, G. A.; Ticos, C.; Wang, Z.; Wurden, C. J. V.

    2007-11-01

    A long-lived (0.3 second, 10-20 cm diameter) ball plasma floating in the air above a water surface has been formed and studied in the laboratory. A 0.4 - 1 mF capacitor is charged to 4-5 kV, and subsequently discharged (30-60 Amps, 20-50 msec duration) into central copper cathode held fixed just below the surface of a bucket of water (with a weak solution of various salts in distilled water, such as CuSO4 or CuCl2, LiCl or NaCl). An underwater ring anode completes the circuit. A bubble of hot vapor from the water surface rises up in the first few milliseconds, and changes from a mushroom cloud with stalk, to a detached quasi-spherical object, finally evolving into a vortex ring. The plasma consists of ionized water vapor, with positive salts and OH- radicals, as well as molecular species, and it completely excludes nitrogen or oxygen from the rising plasma structure. A fine boundary layer is visible in orange, in contrast to a green ball interior when using Cu/CuSO4, and filamentary structures are visible at late times. Finally, a whisp of smoke ring is observed as a residue. A variety of visible and infrared imaging (both video and still cameras) are used, along with 200-800 nm time & space resolved spectroscopy, to identify features of this laboratory analog to ball lightning. Possible applications include a windowless ball- plasma powered pulsed copper vapor laser operating at 510 nm.

  2. The development of a bearing spectral analyzer and algorithms to detect turbopump bearing wear from deflectometer and strain gage data

    NASA Astrophysics Data System (ADS)

    Martinez, Carol L.

    1992-07-01

    Over the last several years, Rocketdyne has actively developed condition and health monitoring techniques and their elements for rocket engine components, specifically high pressure turbopumps. Of key interest is the development of bearing signature analysis systems for real-time monitoring of the cryogen-cooled turbopump shaft bearings, which spin at speeds up to 36,000 RPM. These system elements include advanced bearing vibration sensors, signal processing techniques, wear mode algorithms, and integrated control software. Results of development efforts in the areas of signal processing and wear mode identification and quantification algorithms based on strain gage and deflectometer data are presented. Wear modes investigated include: inner race wear, cage pocket wear, outer race wear, differential ball wear, cracked inner race, and nominal wear.

  3. Bearings: Technology and needs

    NASA Technical Reports Server (NTRS)

    Anderson, W. J.

    1982-01-01

    A brief status report on bearing technology and present and near-term future problems that warrant research support is presented. For rolling element bearings a material with improved fracture toughness, life data in the low Lambda region, a comprehensive failure theory verified by life data and incorporated into dynamic analyses, and an improved corrosion resistant alloy are perceived as important needs. For hydrodynamic bearings better definition of cavitation boundaries and pressure distributions for squeeze film dampers, and geometry optimization for minimum power loss in turbulent film bearings are needed. For gas film bearings, foil bearing geometries that form more nearly optimum film shapes for maximum load capacity, and more effective surface protective coatings for high temperature operation are needed.

  4. Searching for Q-balls with HAWC

    NASA Astrophysics Data System (ADS)

    Karn, Peter

    2013-04-01

    The High Altitude Water Cherenkov (HAWC) Observatory is a gamma-ray experiment currently under construction at Sierra Negra in the state of Puebla, Mexico. Once completed, it will consist of a 20,000 square meter array of 300 water Cherenkov detectors. Although the HAWC Observatory is designed to study gamma rays from galactic and extra-galactic sources, the large instrumented volume of water gives the opportunity to search for more exotic species. One such target, predicted by several varieties of supersymmetric theory, is the Q-ball. Q-balls are very massive, sub-relativistic particles that can have a large baryon number, and can be stable since their creation in the early universe. They are also an appealing candidate for the dark matter of the universe, but their large masses must mean that their flux is very low. The data acquisition system of the HAWC Observatory is flexible enough that, with a dedicated trigger algorithm for non-relativistic particles, it allows the search for Q-balls traversing the detector. The trigger algorithm and preliminary analysis will be presented.

  5. Bear Spray Safety Program

    USGS Publications Warehouse

    Blome, C.D.; Kuzniar, R.L.

    2009-01-01

    A bear spray safety program for the U.S. Geological Survey (USGS) was officially initiated by the Firearms Safety Committee to address accident prevention and to promote personnel training in bear spray and its transportation, storage, and use for defense against wild animals. Used as part of a system including firearms, or used alone for those who choose not to carry a firearm, bear spray is recognized as an effective tool that can prevent injury in a wild animal attack.

  6. THK: CLB Crossed Linear Bearing Seismic Isolators

    SciTech Connect

    Toniolo, Roberto

    2008-07-08

    This text highlights the new seismic isolation technology called CLB (Crossed Linear Bearing), which is made of linear guides with recirculating steel ball technology. It describes specifications and building characteristics, provides examples of seismic isolation and application functionalities and shows experimental data. Since 1994, the constant commitment by Japan to develop diversified anti-seismic systems based on the precise needs of the structures to protect and the areas where they were built has led to the creation of important synergy between the research institutions of leading Japanese companies and THK's Centre for Research and Development. Their goal has been to develop new technology and solutions to allow seismic isolation to be effective in the following cases:.

  7. Linear magnetic bearing

    NASA Technical Reports Server (NTRS)

    Studer, P. A. (Inventor)

    1983-01-01

    A linear magnetic bearing system having electromagnetic vernier flux paths in shunt relation with permanent magnets, so that the vernier flux does not traverse the permanent magnet, is described. Novelty is believed to reside in providing a linear magnetic bearing having electromagnetic flux paths that bypass high reluctance permanent magnets. Particular novelty is believed to reside in providing a linear magnetic bearing with a pair of axially spaced elements having electromagnets for establishing vernier x and y axis control. The magnetic bearing system has possible use in connection with a long life reciprocating cryogenic refrigerator that may be used on the space shuttle.

  8. Bearing restoration by grinding

    NASA Technical Reports Server (NTRS)

    Hanau, H.; Parker, R. J.; Zaretsky, E. V.; Chen, S. M.; Bull, H. L.

    1976-01-01

    A joint program was undertaken by the NASA Lewis Research Center and the Army Aviation Systems Command to restore by grinding those rolling-element bearings which are currently being discarded at aircraft engine and transmission overhaul. Three bearing types were selected from the UH-1 helicopter engine (T-53) and transmission for the pilot program. No bearing failures occurred related to the restoration by grinding process. The risk and cost of a bearing restoration by grinding programs was analyzed. A microeconomic impact analysis was performed.

  9. Automatic ball bar for a coordinate measuring machine

    DOEpatents

    Jostlein, H.

    1997-07-15

    An automatic ball bar for a coordinate measuring machine determines the accuracy of a coordinate measuring machine having at least one servo drive. The apparatus comprises a first and second gauge ball connected by a telescoping rigid member. The rigid member includes a switch such that inward radial movement of the second gauge ball relative to the first gauge ball causes activation of the switch. The first gauge ball is secured in a first magnetic socket assembly in order to maintain the first gauge ball at a fixed location with respect to the coordinate measuring machine. A second magnetic socket assembly secures the second gauge ball to the arm or probe holder of the coordinate measuring machine. The second gauge ball is then directed by the coordinate measuring machine to move radially inward from a point just beyond the length of the ball bar until the switch is activated. Upon switch activation, the position of the coordinate measuring machine is determined and compared to known ball bar length such that the accuracy of the coordinate measuring machine can be determined. 5 figs.

  10. Automatic ball bar for a coordinate measuring machine

    DOEpatents

    Jostlein, Hans

    1997-01-01

    An automatic ball bar for a coordinate measuring machine determines the accuracy of a coordinate measuring machine having at least one servo drive. The apparatus comprises a first and second gauge ball connected by a telescoping rigid member. The rigid member includes a switch such that inward radial movement of the second gauge ball relative to the first gauge ball causes activation of the switch. The first gauge ball is secured in a first magnetic socket assembly in order to maintain the first gauge ball at a fixed location with respect to the coordinate measuring machine. A second magnetic socket assembly secures the second gauge ball to the arm or probe holder of the coordinate measuring machine. The second gauge ball is then directed by the coordinate measuring machine to move radially inward from a point just beyond the length of the ball bar until the switch is activated. Upon switch activation, the position of the coordinate measuring machine is determined and compared to known ball bar length such that the accuracy of the coordinate measuring machine can be determined.

  11. Aerodynamics in the classroom and at the ball park

    NASA Astrophysics Data System (ADS)

    Cross, Rod

    2012-04-01

    Experiments suitable for classroom projects or demonstrations are described concerning the aerodynamics of polystyrene balls. A light ball with sufficient backspin can curve vertically upward through the air, defying gravity and providing a dramatic visual demonstration of the Magnus effect. A ball projected with backspin can also curve downward with a vertical acceleration greater than that due to gravity if the Magnus force is negative. These effects were investigated by filming the flight of balls projected in an approximately horizontal direction so that the lift and drag forces could be easily measured. The balls were also fitted with artificial raised seams and projected with backspin toward a vertical target in order to measure the sideways deflection over a known horizontal distance. It was found that (a) a ball with a seam on one side can deflect either left or right depending on its launch speed and (b) a ball with a baseball seam can also deflect sideways even when there is no sideways component of the drag or lift forces acting on the ball. Depending on the orientations of the seam and the spin axis, a sideways force on a baseball can arise either if there is rough patch on one side of the ball or if there is a smooth patch. A scuff ball with a rough patch on one side is illegal in baseball. The effect of a smooth patch is a surprising new observation.

  12. Biomechanics of heading a soccer ball: implications for player safety.

    PubMed

    Babbs, C F

    2001-08-08

    To better understand the risk and safety of heading a soccer ball, the author created a set of simple mathematical models based upon Newton's second law of motion to describe the physics of heading. These models describe the player, the ball, the flight of the ball before impact, the motion of the head and ball during impact, and the effects of all of these upon the intensity and the duration of acceleration of the head. The calculated head accelerations were compared to those during presumably safe daily activities of jumping, dancing, and head nodding and also were related to established criteria for serious head injury from the motor vehicle crash literature. The results suggest heading is usually safe but occasionally dangerous, depending on key characteristics of both the player and the ball. Safety is greatly improved when players head the ball with greater effective body mass, which is determined by a player"s size, strength, and technique. Smaller youth players, because of their lesser body mass, are more at risk of potentially dangerous headers than are adults, even when using current youth size balls. Lower ball inflation pressure reduces risk of dangerous head accelerations. Lower pressure balls also have greater "touch" and "playability", measured in terms of contact time and contact area between foot and ball during a kick. Focus on teaching proper technique, the re-design of age-appropriate balls for young players with reduced weight and inflation pressure, and avoidance of head contact with fast, rising balls kicked at close range can substantially reduce risk of subtle brain injury in players who head soccer balls.

  13. Rolling Bearing Life Prediction-Past, Present, and Future

    NASA Technical Reports Server (NTRS)

    Zaretsky, E V; Poplawski, J. V.; Miller, C. R.

    2000-01-01

    Comparisons were made between the life prediction formulas of Lundberg and Palmgren, Ioannides and Harris, and Zaretsky and full-scale ball and roller bearing life data. The effect of Weibull slope on bearing life prediction was determined. Life factors are proposed to adjust the respective life formulas to the normalized statistical life distribution of each bearing type. The Lundberg-Palmgren method resulted in the most conservative life predictions compared to Ioannides and Harris, and Zaretsky methods which produced statistically similar results. Roller profile can have significant effects on bearing life prediction results. Roller edge loading can reduce life by as much as 98 percent. The resultant predicted life not only depends on the life equation used but on the Weibull slope assumed, the least variation occurring with the Zaretsky equation. The load-life exponent p of 10/3 used in the American National Standards Institute (ANSI)/American Bearing Manufacturers Association (ABMA)/International Organization for Standardization (ISO) standards is inconsistent with the majority roller bearings designed and used today.

  14. ANN based Performance Evaluation of BDI for Condition Monitoring of Induction Motor Bearings

    NASA Astrophysics Data System (ADS)

    Patel, Raj Kumar; Giri, V. K.

    2016-07-01

    One of the critical parts in rotating machines is bearings and most of the failure arises from the defective bearings. Bearing failure leads to failure of a machine and the unpredicted productivity loss in the performance. Therefore, bearing fault detection and prognosis is an integral part of the preventive maintenance procedures. In this paper vibration signal for four conditions of a deep groove ball bearing; normal (N), inner race defect (IRD), ball defect (BD) and outer race defect (ORD) were acquired from a customized bearing test rig, under four different conditions and three different fault sizes. Two approaches have been opted for statistical feature extraction from the vibration signal. In the first approach, raw signal is used for statistical feature extraction and in the second approach statistical features extracted are based on bearing damage index (BDI). The proposed BDI technique uses wavelet packet node energy coefficients analysis method. Both the features are used as inputs to an ANN classifier to evaluate its performance. A comparison of ANN performance is made based on raw vibration data and data chosen by using BDI. The ANN performance has been found to be fairly higher when BDI based signals were used as inputs to the classifier.

  15. Hotfire testing of a SSME HPOTP with an annular hydrostatic bearing

    NASA Technical Reports Server (NTRS)

    Nolan, Steven A.; Hibbs, Robert I.; Genge, Gary G.

    1994-01-01

    A new fluid film bearing package has been tested in the Space Shuttle Main Engine (SSME) High Pressure Oxygen Turbopump (HPOTP). This fluid film element functions as both the pump end bearing and the preburner pump rear wear ring seal. Most importantly, it replaces a duplex ball bearing package which has been the primary life limiting component in the turbopump. The design and predicted performance of the turbopump are reviewed. Results are presented for measured pump and bearing performance during testing on the NASA Technology Test Bed (TTB) Engine located at MSFC. The most significant results were obtained from proximity probes located in the bearing bore which revealed large subsynchronous precession at ten percent of shaft speed during engine start which subsided prior to mainstage power levels and reappeared during engine shutdown at equivalent power levels below 65% of nominal. This phenomenon has been attributed to rotating stall in the diffuser. The proximity probes also revealed the location of the bearing in the bore for different operating speeds. Pump vibration characteristics were improved as compared to pumps tested with ball bearings. After seven starts and more than 700 seconds of testing, the pump showed no signs of performance degradation.

  16. Ceramic bearing technology program, volume 1: Final report. Final report, 1 August 1992-1 July 1995

    SciTech Connect

    Komanduri, R.; Lange, J.; Wicksted, J.; Krasinski, J.

    1995-07-01

    This project deals with the development of advanced manufacturing technologies for finishing silicon nitride balls and rollers for bearing applications and non-destructive inspection (NDI) methods for assessing surface damage of ceramic materials and to correlate the surface properties with tribological performance. Magnetic field assisted polishing was used for finishing the balls and magnetic abrasive finishing for finishing rollers. By applying low levels of controlled force (1 N/ball or less) the damage to the finished surface is expected to be minimal. Also chemomechanical polishing was used to minimize the brittle fracture. Using these techniques the polishing time was reduced from some 10 - 20 weeks to about 20 hours. The finish obtained was about 5-10 nm and the sphericity in the range of 0.5 - 1 micrometers. The non-destructive inspection (NDI) techniques used include Raman spectroscopy and radio frequency absorption (Lange), Brillouin scattering, and photoacoustic methods to detect surface damage. Inelastic Raman Light Scattering technique was found to be a rapid, non-contact method for characterizing the physical properties of the near-surface (approx. 2 micrometers) ceramic material in bearing balls. A number of features of the Raman spectra were demonstrated to be related to properties of the ceramic which are pertinent to the performance of the bearing balls.

  17. Linear kinematic air bearing

    NASA Technical Reports Server (NTRS)

    Mayall, S. D.

    1974-01-01

    Bearing provides continuous, smooth movement of the cat's-eye mirror, eliminating wear and deterioration of bearing surface and resulting oscillation effects in servo system. Design features self-aligning configuration; single-point, pivotal pad mounting, having air passage through it; and design of pads that allows for precise control of discharge path of air from pads.

  18. Ball-morph: definition, implementation, and comparative evaluation.

    PubMed

    Whited, Brian; Rossignac, Jaroslaw Jarek

    2011-06-01

    We define b-compatibility for planar curves and propose three ball morphing techniques between pairs of b-compatible curves. Ball-morphs use the automatic ball-map correspondence, proposed by Chazal et al., from which we derive different vertex trajectories (linear, circular, and parabolic). All three morphs are symmetric, meeting both curves with the same angle, which is a right angle for the circular and parabolic. We provide simple constructions for these ball-morphs and compare them to each other and other simple morphs (linear-interpolation, closest-projection, curvature-interpolation, Laplace-blending, and heat-propagation) using six cost measures (travel-distance, distortion, stretch, local acceleration, average squared mean curvature, and maximum squared mean curvature). The results depend heavily on the input curves. Nevertheless, we found that the linear ball-morph has consistently the shortest travel-distance and the circular ball-morph has the least amount of distortion.

  19. Magnetohydrodynamics equilibrium of a self-confined elliptical plasma ball

    SciTech Connect

    Wu, H. P. O. Box 8730, Beijing 100080 and Institute of Mechanics, Academia Sinica, Beijing, People's Republic of China ); Oakes, M.E. )

    1991-08-01

    A variational principle is applied to the problem of magnetohydrodynamics (MHD) equilibrium of a self-contained elliptical plasma ball, such as elliptical ball lightning. The principle is appropriate for an approximate solution of partial differential equations with arbitrary boundary shape. The method reduces the partial differential equation to a series of ordinary differential equations and is especially valuable for treating boundaries with nonlinear deformations. The calculations conclude that the pressure distribution and the poloidal current are more uniform in an oblate self-confined plasma ball than that of an elongated plasma ball. The ellipticity of the plasma ball is obviously restricted by its internal pressure, magnetic field, and ambient pressure. Qualitative evidence is presented for the absence of sighting of elongated ball lightning.

  20. Burning molten metallic spheres: One class of ball lightning?

    NASA Astrophysics Data System (ADS)

    Stephan, Karl D.; Massey, Nathan

    2008-08-01

    Abrahamson and Dinniss [2000. Ball lightning caused by oxidation of nanoparticle networks from normal lightning strikes on soil. Nature 403, 519-521] proposed a theory of ball lighting in which silicon nanoparticles undergo slow oxidation and emit light. Paiva et al. [2007. Production of ball-lightning-like luminous balls by electrical discharges in silicon. Physical Review Letters 98, 048501] reported that an electric arc to silicon produced long-lasting luminous white spheres showing many characteristics of ball lightning. We show experimentally that these consist of burning molten silicon spheres with diameters in the 0.1-1 mm range. The evidence of our experiments leads us to propose that a subset of ball lightning events may consist of macro-scale molten spheres of burning metallic materials likely to be ejected from a conventional lightning strike to earth.