890 Matching Results

Search Results

Advanced search parameters have been applied.

Experimental Research on the Friction of Pivots

Description: In horology the friction between solids is of the greatest importance; one limited, however, to the application of the laws of Coulomb which, do not at all correspond with reality. This report presents a review of the subject and some general conclusions. The choice of lubricant is discussed as well as the pressure between frictional surfaces. The gears in a watch are used extensively as examples.
Date: May 1930
Creator: Jaquerod, A.; Defossez, L. & Mügeli, H
Partner: UNT Libraries Government Documents Department

On Laminar and Turbulent Friction

Description: Report deals, first with the theory of the laminar friction flow, where the basic concepts of Prandtl's boundary layer theory are represented from mathematical and physical points of view, and a method is indicated by means of which even more complicated cases can be treated with simple mathematical means, at least approximately. An attempt is also made to secure a basis for the computation of the turbulent friction by means of formulas through which the empirical laws of the turbulent pipe resistance can be applied to other problems on friction drag.
Date: September 1946
Creator: von Karman, T.
Partner: UNT Libraries Government Documents Department

Coefficient of friction and damage to contact area during the early stages of fretting 2: steel, iron, iron oxide, and glass combinations

Description: Report presenting experiments to study the start of fretting and cause of damage during the early stages of fretting of steel-steel combinations at a frequency 5 cycles per minute, an amplitude of 0.006 inch, a load of 150 grams, in air with relative humidity of less than 10 percent. Pure iron, glass, and iron oxide powder compacts were used in supplementary experiments.
Date: April 1954
Creator: Bailey, John M. & Godfrey, Douglas
Partner: UNT Libraries Government Documents Department

A Study of Piston and Ring Friction

Description: Report discusses an investigation into piston and ring friction as compared to total engine friction under natural operating conditions. Several test conditions were explored, including the effect of scuffing and excess cylinder-wall lubrication on friction. A device for measuring ring tensions and an apparatus for transforming pressure-crank angle indicator diagrams into pressure-volume indicator diagrams are also described.
Date: November 1944
Creator: Leary, W. A. & Jovellanos, J. U.
Partner: UNT Libraries Government Documents Department

Direct Measurements of Skin Friction

Description: "A device has been developed to measure local skin friction on a flat plate by measuring the force exerted upon a very small movable part of the surface of the flat plate. These forces, which range from about 1 milligram to about 100 milligrams, are measured by means of a reactance device. The apparatus was first applied to measurements in the low-speed range, both for laminar and turbulent boundary layers. The device was then applied to high-speed subsonic flow and the turbulent-skin-friction coefficients were determined up to a Mach number of about 0.8" (p. 281).
Date: June 1, 1951
Creator: Dhawan, Satish
Partner: UNT Libraries Government Documents Department

Comparison of Frictional Heating Models

Description: The purpose of this work was to compare the predicted temperature rises using four well-known models for frictional heating under a few selected conditions in which similar variable inputs are provided to each model. Classic papers by Archard, Kuhlmann-Wilsdorf, Lim and Ashby, and Rabinowicz have been examined, and a spreadsheet (Excel ) was developed to facilitate the calculations. This report may be used in conjunction with that spreadsheet. It explains the background, assumptions, and rationale used for the calculations. Calculated flash temperatures for selected material combinations, under a range of applied loads and sliding speeds, are tabulated. The materials include AISI 52100 bearing steel, CDA 932 bronze, NBD 200 silicon nitride, Ti-6Al-4V alloy, and carbon-graphite material. Due to the assumptions made by the different models, and the direct way in which certain assumed quantities, like heat sink distances or asperity dimensions, enter into the calculations, frictional hearing results may differ significantly; however, they can be similar in certain cases in light of certain assumptions that are shared between the models.
Date: October 1, 2013
Creator: Davies, Nicholas R & Blau, Peter Julian
Partner: UNT Libraries Government Documents Department

Electronic contribution to friction on GaAs

Description: The electronic contribution to friction at semiconductor surfaces was investigated by using a Pt-coated tip with 50nm radius in an atomic force microscope sliding against an n-type GaAs(100) substrate. The GaAs surface was covered by an approximately 1 nm thick oxide layer. Charge accumulation or depletion was induced by the application of forward or reverse bias voltages. We observed a substantial increase in friction force in accumulation (forward bias) with respect to depletion (reverse bias). We propose a model based on the force exerted by the trapped charges that quantitatively explains the experimental observations of excess friction.
Date: April 15, 2008
Creator: Applied Science and Technology Graduate Group, UC Berkeley; Dept. of Materials Sciences and Engineering, UC Berkeley; Salmeron, Miquel; Qi, Yabing; Park, J.Y.; Hendriksen, B.L.M. et al.
Partner: UNT Libraries Government Documents Department

Turbulent Skin Friction at High Mach Numbers and Reynolds Numbers

Description: From Summary: "For a number of years now, experimenters have been making measurements of skin friction. Formerly, the main interest was at low Mach numbers; later, measurements were made at supersonic Mach numbers. However, almost all of these measurements were over a limited range of Reynolds numbers. On the other hand, these measurements fairly well determined the effects of Mach number and heat transfer on skin friction. The purpose of this paper is to give the results of skin-friction measurements in turbulent boundary layers at high Mach numbers and high Reynolds numbers where data have not previously existed."
Date: July 24, 1958
Creator: Matting, Fred W. & Chapman, Dean R.
Partner: UNT Libraries Government Documents Department

Principles involved in the cooling of a finned and baffled cylinder

Description: An analysis of the cooling problems for a finned cylinder is made on the basis of the known fundamental principles of heat transfer from pipes. Experimental results that support the analysis are presented. The results of previous investigations on the problem are evaluated on the basis of the analysis and the results. An illustration of the application of these principles to a specific problem is included.
Date: June 1938
Creator: Brevoort, M. J.
Partner: UNT Libraries Government Documents Department

A method for studying piston friction

Description: From Introduction: "The purpose of this investigation was to develop a method for determining directly the friction force between the piston and cylinder of an internal combustion engine. The method consists in elastically mounting the cylinder barrel so that it can have a small motion parallel to its axis, and providing suitable means for recording its instantaneous displacement."
Date: March 1943
Creator: Forbes, J. E. & Taylor, E. S.
Partner: UNT Libraries Government Documents Department

Skin-friction drag and boundary-layer transition on a parabolic body of revolution (NACA RM-10)at a Mach number of 1.6 in the Langley 4-by-4 foot supersonic pressure tunnel

Description: Report presenting an investigation at Mach number 1.6 and a range of Reynolds number of the skin-friction drag and boundary-layer transition of a body of revolution. The body had a parabolic-arc profile, a blunt base, and a fineness ratio of 12.2 (NACA RM-10). Results regarding the effect of surface condition, drag breakdown, and results of boundary-layer surveys are provided.
Date: May 20, 1952
Creator: Czarnecki, K. R. & Marte, Jack E.
Partner: UNT Libraries Government Documents Department

Effects of fabrication-type roughness on turbulent skin friction at supersonic speeds

Description: Report presenting an investigation of the effects of fabrication-type surface roughness on turbulent skin-friction drag at supersonic speeds. It was found that fabrication of the thin-skin constructions could be done sufficiently well in practice so as to cause no increase in drag over the smooth body; however, the juncture-type roughnesses produced significant increases in drag as compared with the smooth body. Results indicated that increasing the unit Reynolds number has a detrimental effect and increased the Mach number has a powerful alleviating effect on drag due to surface roughness.
Date: July 1958
Creator: Czarnecki, K. R.; Sevier, John R., Jr. & Carmel, Melvin M.
Partner: UNT Libraries Government Documents Department

An experimental study of applied ground loads in landing

Description: Results are presented of an experimental investigation made of the applied ground loads and the coefficient of friction between the tire and the ground during the wheel spin-up process in impacts of a small landing gear under controlled conditions on a concrete landing strip in the Langley impact basin. The basic investigation included three major phases: impacts with forward speed at horizontal velocities up to approximately 86 feet per second, impacts with forward speed and reverse wheel rotation to simulate horizontal velocities up to about 273 feet per second, and spin-up drop tests for comparison with the other tests. In addition to the basic investigation, supplementary tests were made to evaluate the drag-load alleviating effects of prerotating the wheel before impact so as to reduce the relative velocity between the tire and ground.
Date: August 18, 1955
Creator: Milwitzky, Benjamin; Lindquist, Dean C. & Potter, Dexter M.
Partner: UNT Libraries Government Documents Department

Coefficient of friction and damage to contact area during the early stages of fretting 1: Glass, copper, or steel against copper

Description: Report presenting experiments to measure the coefficient of friction and to determine the damage to the contact area during early stages of fretting of copper at a frequency of 5 cycles per minute. Specimen combinations of copper against glass, copper against copper, and copper against steel, as well as various copper oxide films and powder compacts were used.
Date: September 1953
Creator: Godfrey, Douglas & Bailey, John M.
Partner: UNT Libraries Government Documents Department

Investigation of distributed surface roughness on a body of revolution at a Mach number of 1.61

Description: Report presenting an investigation of the effects of distributed surface roughness, consisting of lathe-tool marks, on the skin-friction drag of a body of revolution at Mach number 1.61. Tests were conducted on ogive-cylinders at zero angle of attack over a range of roughness and Reynolds number. The results indicate that the effects of surface roughness are generally similar to those found at subsonic speeds.
Date: June 1954
Creator: Czarnecki, K. R.; Robinson, Ross B. & Hilton, John H., Jr.
Partner: UNT Libraries Government Documents Department

Skin frictional resistance of plane surfaces in air: Abstract of recent German tests, with notes

Description: Given here is the most recent research on skin frictional resistance of plane surfaces in air that was conducted by Dr. Wieselsberger under the direction of Dr. Prandtl of Gottingen University. In all, 16 models were tested. These were divided into four groups, as follows: 1) cloth, in the original condition; 2) cloth, with the nap singed off; 3) cloth, with three coats of dope; and 4) cloth, with six coats of dope. Each group consisted of four models of uniform width, 1 meter, and of lengths of 0.5, 1.0, 1.5, and 2.0 meters.
Date: July 1922
Creator: Diehl, W. S.
Partner: UNT Libraries Government Documents Department

Friction of aviation engines

Description: "The first portion of this report discusses measurements of friction made in the altitude laboratory of the Bureau of Standards between 1920 and 1926 under research authorization of the National Advisory Committee for Aeronautics. These are discussed with reference to the influence of speed, barometric pressure, jacket-water temperature, and throttle opening upon the friction of aviation engines. The second section of the report deals with measurements of the friction of a group of pistons differing from each other in a single respect, such as length, clearance, area of thrust face, location of thrust face, etc." (p. 179).
Date: 1928
Creator: Sparrow, S. W. & Thorne, M. A.
Partner: UNT Libraries Government Documents Department

Friction of surface films formed by decomposition of common lubricants of several types

Description: Report presenting an investigation to determine the effect on friction of films formed on steel surfaces by decomposition of common lubricants of several types. The films were formed by heating, in air, surfaces to which a thin film of fluid lubricant had been applied. Results regarding the fluid lubricants, decomposition films, surface loading, fluid lubricant on decomposition film, and practical significance are provided.
Date: April 1950
Creator: Johnson, Robert L.; Godfrey, Douglas & Bisson, Edmond E.
Partner: UNT Libraries Government Documents Department

Friction and wear with reactive gases at temperatures up to 1200 degrees F

Description: Report presenting friction and wear experiments conducted to explore the effects of high temperature, varied chlorine content, sulfur catalysis, and preformation of sulfide films on boundary lubrication with reactive gases. Results regarding sulfur hexafluoride, dichlorodifluoromethane, chlorotrifluoromethane, chlorotrifluorometahne plus sulfur hexafluoride, and dichlorodifluoromethane plus sulfur hexafluoride are provided.
Date: September 1958
Creator: Allen, Gordon P.; Buckley, Donald H. & Johnson, Robert L.
Partner: UNT Libraries Government Documents Department

Measurements of Friction Coefficients in a Pipe for Subsonic and Supersonic Flow of Air

Description: Report presenting tests of the flow of air through brass tubes with the friction coefficient and incompressible flow relation as the main focus. The analytical relation between friction coefficient, tube length, and Mach number is shown for flow without shock and the conditions for flow with and without shock are delimited.
Date: July 1943
Creator: Keenan, Joseph H. & Neumann, Ernest P.
Partner: UNT Libraries Government Documents Department

Internal-Friction Study of Aluminum Alloy Containing 4 Weight Percent Copper

Description: Note presenting a study of aluminum alloy containing 4 weight percent copper during aging using low-frequency internal-friction measurements in torsional and flexural vibration. Both polycrystalline and single-crystal specimens exhibit an initial internal-friction peak at 173 degrees Celsius after solution treatment and quenching.
Date: August 1958
Creator: Berry, B. S. & Nowick, A. S.
Partner: UNT Libraries Government Documents Department

Some Observations on the Relationship Between Fatigue and Internal Friction

Description: Results are presented of an investigation made to determine the internal friction and fatigue strength of commercially pure 1100 aluminum under repeated stressing in torsion at various temperatures and stress levels in an effort to find if there exists any correlation between internal friction and fatigue characteristics.
Date: September 1956
Creator: Valluri, S. R.
Partner: UNT Libraries Government Documents Department

A Theoretical Investigation of the Lateral Oscillations of an Airplane With Free Rudder With Special Reference to the Effect of Friction

Description: Report presenting charts showing the variation in dynamic stability with the rudder hinge-moment characteristics. A stabilizing rudder floating tendency combined with a high degree of aerodynamic balance is shown to lead to oscillations of increasing amplitude.
Date: March 1943
Creator: Greenberg, Harry & Sternfield, Leonard
Partner: UNT Libraries Government Documents Department

Pressure and Frictional Resistance of a Cylinder at Reynolds Numbers 5,000 to 40,000

Description: This report presents the results of a series of free-jet measurements to determine the pure frictional resistance of a cylinder from the difference between total resistance and pressure at Reynolds Numbers 5,000 to 40,700. The skin friction is 5 percent of the total resistance at Re = 5,000, and had dropped to 2 percent at Re = 40,000, which supports Thom's theory.
Date: July 1933
Creator: Schiller, L. & Linke, W.
Partner: UNT Libraries Government Documents Department