Showing papers in "Tribology Transactions in 1967"
TL;DR: In this paper, the authors classified rolling contact failures according to their failure mode as wear, plastic flow, fatigue, and bulk failures, with the last class arising outside the immediate contact area.
Abstract: Rolling contact failures are classified according to their failure mode as (a) wear, (b) plastic flow, (c) fatigue, and (d) bulk failures, with the last class arising outside the immediate contact area. The wear failures are subdivided into mild wear by loose particle removal and smearing involving metal transfer. Plastic failures may arise due to overload or to temperature imbalance. Fatigue is of the spalling or the surface distress type. An analysis of the stress conditions in a rolling contact is sketched; the stepwise refinements of the contact model are considered, starting from Hertz theory, and progressively including surface traction, plasticity, elastohydrodynamic lubricant films, surface microtopography, and the inhomogeneities of real metals, Each failure mode is associated with the relevant severity parameters of the contact stress condition, and a description of its mode of formation is given. Guidelines are provided for the identification of that failure mode which, among competing modes, i...
253 citations
TL;DR: In this article, the effect of roughness of surfaces of a slider bearing on the load-carrying capacity and friction force was studied, and the distinction between waviness and roughness was made between random quantities which may be characterized by a probability density function, determined experimentally.
Abstract: The effect of roughness of surfaces of a slider bearing on the load-carrying capacity and friction force, is studied. The distinction is made between waviness and roughness, the latter being treated as a random quantity which may be characterized by a probability density function, determined experimentally. Results can be obtained in closed form suitable for calculation if a Beta distribution is assumed. Actually, this can approximate quite closely a Gaussian distribution, yielding quite accurate results. However, the procedure developed can be carried out for any desired distribution.
251 citations
TL;DR: In this article, the effect of vibration on friction was investigated on a flat steel plate under a dead weight load of 1 kg and a speed of 0.02 cm/second by a speaker at frequencies of 20, 100, 500, and 1000 cycles per second.
Abstract: Experiments were conducted to determine the effect of vibration on friction. A rider, consisting of three fixed 1/3-inch diameter balls, slid along a flat steel plate under a dead weight load of 1 kg and a speed of 0.02 cm/second. The plate was vibrated by a speaker at frequencies of 20, 100, 500, and 1000 cycles per second. Acceleration, coefficient of friction, and electrical resistance of a contact were measured. For both lubricated (white oil plus oleic acid) and unlubricated conditions, apparent kinetic friction decreased rapidly after the acceleration of vibration approached and exceeded the acceleration due to gravity. Electrical resistance increased periodically with vibration. The data indicated that the vibration periodically reduced metal-to-metal contact due to reduced load. Thus, an apparent reduction of the coefficient of friction was observed. Microscopic observation of the unlubricated wear tracks on the plate showed absence of galling, brown film formation, and marked plastic deformation ...
130 citations
TL;DR: In this paper, an interferometric method of determining the shape and thickness of the clastohydrodynamic oil film formed between a rotating ball loaded against a diamond, sapphire, or glass plate, and a rotating roller was presented.
Abstract: The paper describes an interferometric method of determining the shape and thickness of the clastohydrodynamic oil film formed between a rotating ball loaded against a diamond, sapphire, or glass plate, and a rotating roller loaded against a glass plate. The film shape for both point and line contact is found to depend critically on speed and load. It is found that considerable departure from the static Hertzian shape occurs at quite low speeds. The line contact results show the extent of the end closure and its dependence on the blend radius of the roller. Presented as an American Society of Lubrication Engineers paper at the Lubrication Conference held in Minneapolis, Minnesota, October 18–20, 1966.
124 citations
TL;DR: In this paper, the friction and wear characteristics of low-alloy, medium-carbon steel are measured as functions of load and speed, and the results are compared with those to be expected from a model of the wear process in which the wear at the contacting regions between the pin and the disk is closely associated with the oxidation of the metal in these regions.
Abstract: Experiments are described in which pins of low-alloy, medium-carbon steel are worn against disks of the same material under unlubricated sliding conditions. The friction and wear characteristics of this system are measured as functions of load and speed. The choice of loads and speeds was made in such a way as to obtain the entire range of “hot-spot” temperatures possible for the system. The results are then compared with those to be expected from a model of the wear process in which the wear at the contacting regions between the pin and the disk is closely associated with the oxidation of the metal in these regions. The temperature of oxidation is assumed to be the calculated “hot-spot” temperature. In order to make the results compatible with the proposed model, it is necessary to introduce a new parameter (having the dimensions of length) which is shown to increase steeply with increasing “hot-spot” temperature up to about 700 C. It then levels off, at about 10−6 cm, for all hot-spot temperatures in ex...
111 citations
TL;DR: In this paper, the critical oxide thickness is 10−6 cm and the metals must be heated until this thickness is reached, and other solid lubricant films appear to obey the same criteria of not 100 hard, not too thin.
Abstract: Experimental data obtained with sixteen metals suggest that hexagonal structured metals have low friction, while other metals have high friction unless a lubricating oxide layer is farmed. In order for an oxide to lubricate, it must not be much harder than the substrate, and the oxide thickness must be adequate. For pin-an-desk tests at loads of about 1 kg, the critical oxide thickness is 10−6 cm, and the metals must be heated until this thickness is reached. Other solid lubricant films appear to obey the same criteria of not 100 hard, not too thin.
75 citations
TL;DR: In this paper, an expression for the change in relative dimensions of an angular contact bearing, as determined by the temperature gradient across the bearing, was derived for the accommodation of the bearing to expansion, this accommodation resulting from elastic deformation and changes in contact angles.
Abstract: Equations have been developed relating friction-power to bearing element temperatures for the particular case of prelubricated or lightly lubricated ball bearings. An expression is derived for the change in relative dimensions of an angular contact bearing, as determined by the temperature gradient across the bearing. A second expression is found for the accommodation of the bearing to expansion, this accommodation resulting from elastic deformation and changes in contact angles. A comparison of these relationships reveals that unstable operating conditions may occur and lead to sudden uncontrollable increases in contact loads. These regions of unstable operation may occur as a result of lubricant degradation or bearing wear, as well as combinations of operating speed and housing dimensions.
68 citations
TL;DR: In this paper, the anti-wear properties of pure metal O,O-dialkylphosphorodithioates in n-hexadecane were determined for steel-on-steel and copper-onsteel systems under mild conditions of sliding.
Abstract: The antiwear characteristics of pure metal O,O-dialkylphosphorodithioates in n-hexadecane are determined for steel-on-steel and copper-on-steel systems under mild conditions of sliding. Their effectiveness is found to be directly related to their rate of thermal decomposition; and more thermally stable structures exhibited better antiwear characteristics. This demonstrates that differences in wear are due to differences in chemical, not adhesive, wear. Because thermal stability is systematically dependent upon alkyl group structure and metal cation size, it is concluded that neither the alkyl group nor the metal play a direct role in the effectiveness of the additive in reducing wear. The nature of the surface reaction leading to chemical wear is not known. Contributed to the American Society of Lubrication Engineers by the author. Manuscript received August 12, 1966.
67 citations
TL;DR: Sliding friction characteristics in vacuum of single and polycrystalline aluminum oxide in contact and with various metals were studied in this paper, showing that aluminum oxide exhibits sliding friction characteristics with respect to metal contact.
Abstract: Sliding friction characteristics in vacuum of single and polycrystalline aluminum oxide in contact and with various metals
50 citations
TL;DR: For solid lubricant films such as oxides, soft metals and molybdenum disulfide in a resin low friction and low wear have been found when the film thickness lies between 10−6 and 10−2 cm, and high friction and high wear outside these limits.
Abstract: For solid lubricant films such as oxides, soft metals and molybdenum disulfide in a resin low friction and low wear have been found when the film thickness lies between 10−6 and 10−2 cm, and high friction and high wear outside these limits At the 10−3−cm limit, the rise in friction occurs because the load is carried by the film rather than by the substrate, while the rise in wear is caused by the formation of large wear particles The experimental data appear to agree reasonably well with theoretical predictions based on the concepts of characteristic junction size and wear particle size Presented as an American Society of Lubrication Engineers paper at the Lubrication Conference held in Minneapolis, Minnesota, October 18–20, 1966
50 citations
TL;DR: The properties of borate-containing lubricants were studied in this paper to determine their structure and mode of action, and they were shown to be amorphous structures a few thousand angstroms thick containing boron, ferrous iron and organic components.
Abstract: The EP films generated by borate-containing lubricants were studied to determine their structure and mode of action. Films were generated on SAE Machine test specimens with a blend of tribenzyl borate in solvent neutral oil. Study of the generated films in situ and after chemical stripping show them to be amorphous structures a few thousand angstroms thick containing boron, ferrous iron and organic components. Attempts to reproduce film material synthetically are described. Surfaces with borate EP films are shown to be harder than the steel substrate. Thus, they do not conform to the usual concept of more conventional EP agents which are generally believed to provide an easily-sheared film. Presented as an American Society of Lubrication Engineers paper at the Lubrication Conference held in Minneapolis Minnesota, October 18–20, 1966.
TL;DR: In this article, the load-carrying capacity of squalane and a solvent neutral oil has been investigated as a function of operating procedure by using radially loaded steel disks with combined rolling and sliding.
Abstract: The load-carrying capacity of squalane and a solvent neutral oil has been investigated as a function of operating procedure by using radially loaded steel disks with combined rolling and sliding. Load-carrying capacity and accompanying critical temperatures are found to depend on the time-temperature-load-velocity history of the disks. Thus, no simple load-carrying criterion appears to exist even for comparatively “nonreactive” hydrocarbon lubricants.
TL;DR: In this article, the passage of current, both DC and AC, through elastohydro-dynamically lubricated contacts using a 4-ball machine running at 175 rpm with 1 in steel balls was studied.
Abstract: A study is made of the passage of current, both DC and AC, through elastohydro-dynamically lubricated contacts using a 4-ball machine running at 175 rpm with 1 in Steel balls. At small applied voltages ∼15mV, when there is a coherent oil film, (i.e., when it is not short circuited by metallic contact) it behaves as an ohmic resistance. The resistance of the oil film varies from >101 ohms down to 1 ohm. This has important implications for the concept of percentage metallic contact, and for the statistical contact method of assessing oil film thickness. At high currents (∼1 amp.) the current flows by the voltage discharge mechanism. The transition from ohmic resistance to discharge is discussed. Using the resistance of the oil film the lubricating quality of long chain acids in cetane is compared. A brief study is also mode of Fein's temperature correlation.
TL;DR: In this article, the hydrodynamic effect of viscoelasticity in bearing performance was investigated experimentally by measuring the pressure distribution of viscous liquids and Newtonian liquids in a simulated plain journal bearing.
Abstract: The hydrodynamic effect of viscoelasticity in bearing performance was investigated experimentally by measuring the pressure distribution of viscoelastic liquids and Newtonian liquids in a simulated plain journal bearing. The pressure distribution of the viscoelastic liquids was somewhat different from that of the Newtonian liquids, showing a flattening of the pressure profile and a shift of the circumferential position of the peak pressure. Such a difference contributes to a small recovery of the loss of the load-carrying capacity due to the non-Newtonian viscosity for viscoelastic liquids. It may also contribute to a further reduction of friction beyond the effect of shear thinning. The difference of cavitation on the divergent region of the bearing for these two different kinds of liquid was evident. The viscoelastic liquids showed less extent of cavitation. The experimental conditions conform closely to those used in the classical hydrodynamic lubrication theory. The experimental data indicate that the...
TL;DR: In this article, the isothermal secant and tangent bulk moduli of petroleum oils and pure hydrocarbons have been studied in detail and generalizations of the relationships were achieved.
Abstract: The increasing use of complex hydraulic systems has resulted in an increasing demand for bulk modulus data. Reliable data are difficult and expensive to obtain. The isothermal secant and tangent bulk moduli of petroleum oils and pure hydrocarbons have been studied in detail. Generalizations of the relationships were achieved. Charts are given to enable prediction of these moduli and densities from 0 to 500 F, over a pressure range of more than 100,000 psi with a minimum of calculation. The average error is less than 1.0%. The only required data are the density of the oil at atmospheric pressure and the desired temperature. Oil type or viscosity does not affect the result.
TL;DR: In this paper, the centripetal inertia terms in a comprehensive analysis of hydrostatic thrust bearing of spherical form were analyzed. But the authors focused on the main characteristics of this form of bearing which is capable of supporting combined axial and radial loads.
Abstract: This paper includes the predominant centripetal inertia terms in a comprehensive analysis of hydrostatic thrust bearings of spherical form. The analysis considers continuous spherical surfaces which are not interrupted by grooves and solutions are presented for spheres having radii equal to and less than the radius of the hemispherical seal. This analysis demonstrates that fluid inertia effects influence the pressure distribution as suggested by Shaw and Strang. When the sphere and seat have equal radii the film pressures are always enhanced while for the other case the film pressures may increase or decrease depending upon the location of the center of the hemispherical seat. Attention is drawn to the main characteristics of this form of bearing which is capable of supporting combined axial and radial loads.
TL;DR: In this article, the growth of junctions between contacting asperities due to the action of the friction force was taken into account in the theoretical model, and a large improvement in the correlation with experimental surface temperature measurements at dry friction contacts was obtained.
Abstract: This is a theoretical paper concerned with the rise in the surface temperatures caused by frictional heating at sliding contacts. By taking into account in the theoretical model, the growth of junctions between contacting asperities due to the action of the friction force, a large improvement in the correlation with experimental surface temperature measurements at dry friction contacts has been obtained. These results are felt to support the use of the usual flash temperature technique for predicting the surface temperatures in lubricated or low friction conditions. Presented as an American Society of Lubrication Engineers paper at the Lubrication Conference held in Minneapolis, Minnesota, October 18–20, 1966.
TL;DR: In this article, the influence of physical and chemical properties on rolling contact fatigue was evaluated with a 4-ball type fatigue machine. And the results indicated that the chemical properties as well as the physical properties of the lubricant can be important in roll contact fatigue.
Abstract: To study the influence of lubricant physical and chemical properties on rolling contact fatigue, a variety of base stocks and additives were evaluated with a 4-ball type fatigue machine. The effect of viscosity was found to depend on the means by which a given viscosity was achieved. Although some commonly used EP and antiwear additives had a pronounced effect on fatigue life, the direction and magnitude of the additive effect depended on the particular additive and its concentration in the blend. In addition, it was observed that the additive effect depended on the choice of base oil and ball steel. These results indicate that the chemical properties as well as the physical properties of the lubricant, can be important in rolling contact fatigue. Presented as an American Society of Lubrication Engineers paper at the Lubrication Conference held in Minneapolis, Minnesota, October 18–20, 1966.
TL;DR: In this article, the sliding friction between an 1/8 in. spherical steel rider and a gold-plated steel flat was measured for various loads (200-2000 gm), gold film thicknesses (0.1-10 μ) and steel combinations (440C and 52100).
Abstract: Sliding friction between an 1/8 in. spherical steel rider and a gold-plated steel flat was measured for various loads (200–2000 gm), gold film thicknesses (0.1–10 μ) and steel combinations (440C and 52100). Coefficient of friction recorded in each run for 100 traverses was found to be most sensitive to the rider material (0.1–0.3 with 440C rider and 0.1–0.6 with 52100 rider, as compared to 0.6–0.7 for unlubricated steel). With a 52100 rider, as the number of traverses increase three distinct types of frictional behaviors were found: (A) slowly decreasing, (B) rapidly decreasing, and (C) increasing (sometimes a minimum was first reached). Theoretical coefficient of friction (0.1) was only observed with 'Type B' results. With a chromium rich 440C rider, friction was always low presumably due to its low affinity to gold. Presented as an American Society of Lubrication Engineers Paper at the Lubrication Conference held in Minneapolis, Minnesota, October 18–20, 1966.
TL;DR: In this article, the influence of certain vapors and liquids on the coefficient of friction of molybdenum disulfide has been studied under boundary conditions, and the results show that the coefficient is lowest in absence of the vapors or liquids studied, and under these conditions is independent of load.
Abstract: The influence of certain vapors and liquids on the coefficient of friction of molybdenum disulfide has been studied under boundary conditions. The vapors investigated were those of water, butanol, benzene, and heptane. The liquids used were water, glycol, glycerol, dodecanol, dodecylamine, dodecane, hexadecane, ocladecane, white paraffin oil with and without additions of nonanoic acid and nonyl alcohol, and commercial mineral oil. The tests were performed on various friction testing machines, viz., on the LFW-1, LFW-2, Almen-Wieland, and Reichert machines. The test results show that the coefficient of friction of molybdenum disulfide is lowest in absence of the vapors or liquids studied, and under these conditions is independent of load. With increasing polarity of the vapor or liquid the coefficient of friction of molybdenum disulfide increases.
TL;DR: Friction, wear and metal transfer of the silver-iron friction couple have been studied as a function of oxygen percentage of the surrounding atmosphere at different levels of temperature as discussed by the authors, and the results show that the replacement of high purity argon by a mixture of argon and oxygen causes an instantaneous increase in friction followed by local transfer of silver to the iron surface and a high rate of wear.
Abstract: Friction, wear and metal transfer of the silver-iron friction couple have been studied as a function of oxygen percentage of the surrounding atmosphere at different levels of temperature. The results show that the replacement of high purity argon by a mixture of argon and oxygen causes an instantaneous increase in friction, followed by local transfer of silver to the iron surface and a high rate of wear. The observed effect is reversible. It is found that in the severe wear region the diffusion of oxygen towards the friction interface determines the wear rate, although visible oxidation does not occur. Experimental evidence strongly suggests that the formation of thin films of iron oxide is responsible for increased adhesion and metal transfer. Presented as an American Society of Lubrication Engineers paper at the Lubrication Conference held in Minneapolis, Minnesota, October 18–20, 1966.
TL;DR: In this paper, the effects of the elastic and Hertzian distortions of the hollow rollers are considered in the determination of the bearing internal load distribution, fatigue life, and deflection.
Abstract: Cylindrical roller bearings with annular rollers may be advantageous in applications where weight, lubrication, and speed are major considerations in the operation of the bearing. This discussion describes an analytical technique whereby the effects of the elastic and Hertzian distortions of the hollow rollers are considered in the determination of the bearing internal load distribution, fatigue life, and deflection. Numerical examples calculated for a bearing having annular rollers indicate that the distortion of the flexible rollers improve the load distribution permitting increased bearing fatigue life. The advantage must be compared with the increased bearing deflections and bending stresses in the hollow rollers to determine the adequacy of the bearing under given conditions of applied load and speed. Additionally, the skidding of the cylindrical roller bearing with annular rollers is considered for conditions of high speed and extremely light radial load. Presented as an American Society of Lubricat...
TL;DR: In this paper, the authors presented friction-wear characteristics of self-lubricating surfaces at temperatures of up to 950 F and showed that they offer potential as loadbearing surfaces and seals in high temperature applications for both oxidizing and inert or vacuum environment.
Abstract: A technique has been developed, whereby mechanical strength and excellent oxidation resistance is imparted to self-lubricating bodies of high lubricant content. By an “amalgamation” of powdered solid lubricants, such as tungsten diselenide, with a gallium alloy, followed by a subsequent compression-curing cycle, self-lubricating surfaces have been formed that resist oxidation at a temperature of 1500 F. This paper presents friction-wear characteristics of these materials at temperatures to 950 F. They offer potential as load-bearing surfaces and seals in high temperature applications for both oxidizing and inert or vacuum environment. Presented as an American Society of Lubrication Engineers paper at the Lubrication Conference held in Minneapolis, Minnesota, October 18–20, 1966.
TL;DR: In this paper, the physical behavior of a viscoelastic-elastic layered system under the influence of a moving load is investigated, restricted to a quasi-stationary case within the plane strain theory and represented by a standard linear model in shear.
Abstract: An investigation is made of the physical behavior of a viscoelastic-elastic layered system under the influence of a moving load. It is restricted to a quasi-stationary case within the plane strain theory, and the viscoelastic material is represented by a standard linear model in shear. The quasi-stationary nature of the surface deformation and interface shear stress are studied. The surface deformation is correlated with the coefficient of deformation friction through a newly developed criterion.
TL;DR: In this paper, a kinetic investigation of the reaction of steel surfaces and labeled sulfur compounds under boundary lubrication with line contact was carried out, and the active sulfur compound was examined with an accompanying compound, such as a sulfur or chlorine compound, in a binary additive system in cetane solution.
Abstract: A kinetic investigation of the reaction of steel surfaces and labeled sulfur compounds under boundary lubrication with line contact was carried out. The active sulfur compound was examined with an accompanying compound, such as a sulfur or chlorine compound, in a binary additive system in cetane solution. In the friction tests for the solutions containing two kinds of sulfur compounds, elementary sulfur showed the highest reactivity among the sulfur compounds used, didodecyl disulfide the lowest. Dibenzyl disulfide reduced the wear rate of the frictional surface, although it produced no disturbance of the reaction between the frictional surface and elementary sulfur, which is simultaneously used in the sample solution. It was suggested that a dynamic model rather than a static model be considered for the lubricant film functioning under boundary lubrication, and also that any deficiency of an additive could be made up by addition of the second compound used simultaneously in oil. In the friction tests usi...
TL;DR: In this paper, cold welding tendencies and frictional studies of clean metal combinations under ultra high vacuum are discussed. But they do not consider the effects of cold welding on clean metal.
Abstract: Cold welding tendencies and frictional studies of clean metal combinations under ultra high vacuum
TL;DR: In this article, a study of an optical and two stylus-type instruments for measuring surface finish was conducted, and the stylus type instruments were demonstrated to be inaccurate on metals that have a Rockwell hardness less than C-66.
Abstract: A study of an optical and two stylus-type instruments for measuring surface finish was conducted. The stylus-type instruments are demonstrated to be inaccurate on metals that have a Rockwell hardness less than C-66. The inaccuracy is attributed primarily to surface damage caused by the stylus. The optical instrument causes no surface damage. Stylus-type instruments are proven also to be unsatisfactory for rating relative degree of roughness unless gross roughness differences are considered. The interpretation of interferographs is discussed. Presented as an American Society of Lubrication Engineers paper at the Lubrication Conference held in Minneapolis, Minnesota, October 18–20, 1966.
TL;DR: In this article, the effect of a carbon-carbon double bond in the boundary lubrication of stainless steel was investigated and it was shown that the use of the unsaturated 1-cetene resulted in a lowering of the friction coefficient and the wear over its saturated analog, cetane.
Abstract: Friction and wear experiments with 1-cetene and cetane on stainless steel demonstrated the effect of a carbon-carbon double bond in the boundary lubrication of stainless steel. Experiments with cold-rolled steel, nickel, and chromium indicated the chromium to be the constituent in the steel that is markedly affected. The use of the unsaturated 1-cetene resulted in a lowering of the friction coefficient and the wear over its saturated analog, cetane. It is postulated that the improvement in friction and wear observed using the olefin 1-cetene is due to chemical attachment to the chromium or chromium oxide present in the wearing surface of the stainless steel reducing the amount of intermetallic contact. Experiments using the pure polar olefin vinyl stearate as the lubricant resulted in even further improvement of the frictional properties of stainless steel rubbing surfaces than the olefin alone, and a mechanism is proposed. It is also shown that these same improvements in frictional properties can be obta...
TL;DR: In this paper, a model of adhesive wear for liquid lubricants has been modified to include the effect of vapor pressure on the wear rate for vapor lubricants at low pressures or high vacuum.
Abstract: A recently developed model of adhesive wear for liquid lubricants has been modified to include the effect of vapor pressure on the wear rate for vapor lubricants at low pressures or high vacuum. Two distinctly different tests of the model were made with published data on the wear of graphite in varying atmospheres. In addition to correlating the experimental wear data as a function of pressure and heat of adsorption, the calculated value of the wear coefficient km for graphite-graphite contact from both correlations is internally consistent. Presented as an American Society of Lubrication Engineers paper at the Lubrication Conference held in Minneapolis, Minnesota, October 18–20, 1966.
TL;DR: In this paper, the effects of automatic transmission fluid additives on the friction characteristics of a mineral oil are presented, and relationships between molecular structure of the additives and friction characteristics are discussed, but general conclusions are not formulated.
Abstract: The effects of automatic transmission fluid additives on the friction characteristics of a mineral oil are presented. Some common viscosity-index improvers, chain-breaking oxidation inhibitors, and ashless dispersants have little or no effect on the friction characteristics of the mineral oil. Conversely, some metal-organic dispersants as well as a zinc 0,0′-dialkylphosphorodithioate oxidation inhibitor alter the friction characteristics of the mineral oil. The results indicate that some of the additives are multifunctional and will render the friction characteristics of the mineral oil satisfactory. Relationships between molecular structure of the additives and friction characteristics are discussed, but general conclusions are not formulated. Presented as an American Society of Lubrication Engineers Paper at the Lubrication Conference held in Minneapolis. Minnesota, October 18–20, 1966.