Showing papers in "Tribology Transactions in 1978"
TL;DR: In this paper, four-ball wear studies have demonstrated that the antiwear performance of a commercial zinc dialkyl dithiophosphate (ZDP) antiwear agent can be adversely affected by the presence of some friction modifiers, EP agents, oxidation inhibitors, and detergentdispersants.
Abstract: Four-ball wear studies have demonstrated that the antiwear performance of a commercial zinc dialkyl dithiophosphate (ZDP) antiwear agent can be adversely affected by the presence of some friction modifiers, EP agents, oxidation inhibitors, and detergent-dispersants. To explain these observations, ZDP decomposition studies were conducted with these other additives present. None of the measured ZDP decomposition characteristics completely explain the observed changes in ZDP antiwear performance. Complex formation in the bulk oil and competition for the surface seem to be involved. Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference in Boston, Massachusetts, October 5–7, 1976
89 citations
TL;DR: In this paper, a tribometer employing a steel ball in sliding contact with a glass disk was used to measure the dynamics of abrasive particles and of solid lubricant particles within the contact.
Abstract: A bench metallograph was converted into a 'micro contact imager' by the addition of a tribometer employing a steel ball in sliding contact with a glass disk. The sliding contact was viewed in real time by means of projection microscope optics. The dynamics of abrasive particles and of solid lubricant particles within the contact were observed in detail. The contact was characterized by a constantly changing pattern of elastic strain with the passage of surface discontinuities and solid particles. Abrasive particles fragmented upon entering the contact, embedded in one surface and scratched the other; in contrast, the solid lubricant particles flowed plastically into thin films. The rheological behavior of the lubricating solids gave every appearance of a paste-like consistency within the Hertzian contact.
55 citations
TL;DR: In this article, the presence of a debris dent alters the shape of the inlet region so that the local film thickness at the leading edge of the dent can become substantially lower than the trailing edge.
Abstract: Film thickness measurements associated with a debris dent have been made with interferometry under static and dynamic conditons. The presence of a debris dent alters the shape of the inlet region so that the local film thickness at the leading edge of the dent can become substantially lower than the trailing edge. The pressure modifications associated with these local elastohydrodynamic (EHD) effects are in line with the frequent occurrence of surface initiated fatigue spalls originating at the trailing edge of debris dents. The effectiveness of the EHD mechanism in reducing the stress concentrations at the shoulders of the dent is related to inlet dimensions and dent size.
53 citations
TL;DR: Friction and wear experiments conducted on polyimide films bonded to 440C stainless steel disks indicated that a wear transition (from high wear to low wear) accompanied the friction transition as discussed by the authors.
Abstract: Friction and wear experiments conducted on polyimide films bonded to 440C stainless steel disks indicated that a wear transition (from high wear to low wear) accompanied the friction transition (from high friction to low friction). The transition was found to be atmosphere dependent as well as temperature dependent. Wear rate calculations indicated that at temperatures above the transition, wear could be up to 600 times less than at temperatures below the transition. Transfer to metallic riders was also investigated and found to be considerably different at temperatures above and below the transition.
52 citations
TL;DR: In this paper, a super-refined paraffinic mineral oil has been used to study the chemical reactions under boundary conditions in a four-ball wear tester, and the reaction temperature at the wear junction has been estimated to be 351°C for 40kg load, 600 rpm, 75°C bulk oil temperature.
Abstract: A super-refined paraffinic mineral oil has been used to study the chemical reactions under boundary conditions in a four-ball wear tester. By quantatively analyzing the wear debris generated, chemical reaction rate data used to correlate between dynamic wear tests and static, externally controlled temperature runs. The reaction temperature at the wear junction has been estimated to be 351°C for 40kg load, 600 rpm, 75°C bulk oil temperature. This temperature is higher than the Blok-Archard flash temperatures calculated under the same conditions. Presented at the 32nd Annual Meeting in Montreal, Quebec, Canada, May 9–12, 1977
50 citations
TL;DR: In this paper, a bimodal histogram of the surface energy of a fine tip on 4,500 Aaluminum foils under load varying between 1μN and 200μN in an electron microscope was studied.
Abstract: Adhesion and friction of a fine tip on 4,500Aaluminum foils under load varying between 1μN and 200μN in an electron microscope were studied. When dislocation density is low and impact occurs far from any pre-existing dislocation, small elastic adhesion is observed as long as theoretical strength is not reached. If this impact occurs in the immediate vicinity of a dislocation, there is plastic deformation and adhesion is high. The result is a statistical one, and a bimodal histogram is obtained. When load increases, plastic probability and its value increase. A model, emphasizing the role of surface energy is proposed; it allows the interpretation of the high strength behavior of contaminated annealed surfaces, and of some of Buckley's results for adhesion. When a tangential displacement is imposed, coefficient of friction is nearly zero at small loads. The coefficient of friction sharply increases above a certain critical load (which depends on the initial dislocation density). It still increases with loa...
48 citations
TL;DR: In this paper, a pin-and-disk wear machine has been used to measure the division of heat at the interface between the pin and disk, together with the temperature of the surface of the pin (T8), for low-alloy, medium carbon steel specimens sliding against each other, without lubrication, at a speed of 511 m s−1 and under various loads (58 to 294 N).
Abstract: Experiments are described in which a pin-and-disk wear machine has been used to measure the division of heat (δexpt) at the interface between the pin and disk, together with the temperature of the surface of the pin (T8), for low-alloy, medium-carbon steel specimens sliding against each other, without lubrication, at a speed of 511 m s−1 and under various loads (58 to 294 N) The equilibrium mild wear rates (wexpt) and frictional forces (F) were also measured An analytical expression is deduced for the division of heat (δtheory) in terms of a surface model consisting of N asperities of approximately the same individual area of contact upon which an oxide film of thicknessζis situated The various combinations of N andζwhich provide good correlation betweenδtheory andδexpt, and the values of the temperature of the real areas of contact (T0) which are associated with N,ζand T8, have been fed into a computer program designed to produce the Oxidational Activation Energy from an expression for the wear rat
44 citations
TL;DR: In this article, a complete solution for the inlet half of an elastohydrodynamic contact between two circumferentially ground rough disks is presented, where the effect of the roughness of the surfaces both on the hydrodynamic and on the contact mechanics of the system is taken into account.
Abstract: A complete solution for the inlet half of an elastohydrodynamic contact between two circumferentially ground rough disks is presented. The effect of the roughness of the surfaces both on the hydrodynamic and on the contact mechanics of the system is taken into account. The temperature distribution on the surfaces resulting from asperity interactions in the inlet zone is also included. The results are discussed in relation to the conditions of scuffing failure observed experimentally. Surface interactions are much more sever than would be expected from conventional smooth-surface theory. Asperity interaction in the inlet zone can provoke thermal instability, but only for unrealistically high values of the thermal feedback parameter. The results support the suggestion that failure occurs when the mean hydrodynamic pressures generated by the system are no longer sufficient to permit a liquid film of very high viscosity to be interposed between the interaction asperities. Presented as an American Society of L...
44 citations
TL;DR: In this article, a sliding friction experiment with pyrolytic boron nitride in sliding contact with itself and various metals was conducted, and it was found that the friction coefficient for pyrolithic borsnide in contact with a metal in air than in vacuum.
Abstract: Sliding friction experiments were conducted with pyrolytic boron nitride in sliding contact with itself and various metals. Auger emission spectroscopy was used to monitor transfer of pyrolytic boron nitride to metals and metals to pyrolytic boron nitride. Results indicate that the friction coefficient for pyrolytic boron nitride in contact with metals can be related to the chemical activity of the metals and more particularly to the d valence bond character of the metal. Transfer was found to occur to all metals except silver and gold and the amount of transfer was less in the presence than in the absence of metal oxide. Friction was less for pyrolytic boron nitride in contact with a metal in air than in vacuum.
28 citations
TL;DR: In this paper, the authors used an Auger electron spectroscopy (AES) and depth-profiling technique to monitor changes in the chemistry of 52100 bearing steel surfaces as a function of cleaning history and conditions of TCP exposure.
Abstract: The low-speed lifetime of steel ball bearings under boundary lubrication can be significantly extended by prior soaking in hot tricresyl phosphate (TCP). Auger electron spectroscopy (AES) and depth-profiling techniques were combined to monitor changes in the chemistry of 52100 bearing steel surfaces as a function of cleaning history and conditions of TCP exposure. Phosphorus was detected in the outer layer of all samples exposed to TCP; the length of TCP exposure beyond three days had minimal effect on the surface concentration of phosphorus but did increase its depth of penetration and alter its local chemical environment. When presoaked with conditions (15 days in TCP at 110°C) which lead to optimum bearing lifetimes (I), the steel developed a surface film comprising three distinct regions of different composition. The outermost region had 4–6 percent phosphorus where the phosphorus Auger signal shapes were consistent with those of a phosphorus-oxygen moiety. The innermost region resembled the oxide/met...
24 citations
TL;DR: In this article, new developments in statistical inference for the two parameter Weibull distribution are explained in the terminology of bearing endurance testing, which has application in the very common circumstance wherein one wishes to evaluate the effect of several levels of a design or environmental variable upon fatigue life.
Abstract: New developments in statistical inference for the two parameter Weibull distribution are explained in the terminology of bearing endurance testing. Specifically the developments are: 1. Procedures for conducting an exact test of whether the Weibull shape parameter and a percentile, such as the L10 life, differs significantly among κ (2≤κ≤10) groups of censored life test results. These procedures have application in the very common circumstance wherein one wishes to evaluate the effect of several levels of a design or environmental variable upon fatigue life. Given the results of a censored life test conducted at each level of the variable, it is necessary to decide whether the observed differences in life are real or are explainable by random variation. 2. Procedures for setting confidence limits on the shape parameter and the L10 life of a Weibull distributed failure mode when observations are censored through the failure of the bearing by means of another competing failure mode. These procedures have ap...
TL;DR: In this paper, the effects of a combination of an iron sulfide surface and surfactants on wear were examined in air and argon atmospheres using a ball-on-dish friction machine.
Abstract: The adsorption of organic polar compounds onto iron sulfide and onto iron oxide was investigated using a flow microcalorimeter. The effects of a combination of an iron sulfide surface and surfactants on wear were examined in air and argon atmospheres using a ball-on-dish friction machine. The polar interaction and reactivity between organic polar compounds and iron sulfide are important functions for wear reduction. This was shown from the results obtained in the measurement of the heat of adsorption, amount of adsorption, heat of desorption and iron content in the desorption solution. The adsorption of stearic acid on the steel ball sulfidized in H2S reduced wear significantly in the air atmosphere. Surfactants contribute considerably to wear reduction when used with sulfur EP additives which form an iron sulfide film.
TL;DR: In this article, a comparison of measured and calculated roll forces showed that the flow stress is the single most important variable, and contributions of friction are negligible, and the onset of skidding was a function of oil viscosity, bulk temperature, rolling speed and material flow stress, but could not predict from current theories of hydrodynamic lubrication.
Abstract: Rolling lubrication aims at reducing friction without endangering the stability of the process. This means that, in practice, a slight but positive forward slip is maintained, and lubrication is of a mixed hydrodynamic-boundary type. When fully hydrodynamic lubrication is attained, forward slip becomes negative, the strip skids in the roll gap, and thus a limiting condition is attained. These conditions were investigated for the specific example of 6061-0 and T6 Al alloy with uncompounded mineral oils of varying viscosities at various rolling speeds, giving forward slip ranging from slightly positive to highly (-80 percent) negative values. A comparison of measured and calculated roll forces showed that the flow stress is the single most important variable, and contributions of friction are negligible. The onset of skidding was a function of oil viscosity, bulk temperature, rolling speed and material flow stress, but could not be predicted from current theories of hydrodynamic lubrication. The rolled stri...
TL;DR: In this paper, a simplified calculation of the coefficient of traction for an elastohydrodynamic line contact, based upon a complete numerical solution to the coupled thermal and non-Newtonian hydrodynamic equations, is presented.
Abstract: A simplified calculation of the coefficient of traction for an elastohydrodynamic line contact, based upon a complete numerical solution to the coupled thermal and non-Newtonian hydrodynamic equations, is presented. The simplified calculation is a direct, noniterative procedure requiring only a fraction of the computation time required by the complete analysis. Comparisons are made between the calculated values of traction using the simplified procedure and recent traction data. Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference in Boston, Massachusetts, October 5–7, 1976
TL;DR: In this paper, a fixed tapered land thrust bearing has been studied both theoretically and experimentally and the influence of groove inclination, film thickness, and flow regimes on operating characteristics is determined.
Abstract: A fixed tapered land thrust bearing has been studied both theoretically and experimentally. Each land in contact with a flat rotating disk is made out of one inclined and one parallel section. Lubricant is fed through grooves which are inclined with respect of a radius in the direction of motion, flow is going from center to exit. Isothermal conditions are considered, both laminar and turbulent regimes are studied. Transition is characterized using local transition concepts. Constantinescu's theory is applied. The influence of groove inclination, film thickness, and flow regimes on operating characteristics is determined. A further analysis on the effect of centrifugal inertia terms in laminar lubrication is also conducted. Experiments are run on a special device in which speed and load can be varied and both friction torque and film thickness are measured. Water is used, thus temperature is kept constant and fluid dissipation is low. Presented at the 32nd Annual Meeting in Montreal, Quebec, Canada, May 9...
TL;DR: In this article, an experimental study has been conducted of the hydrodynamic lubrication of a spherical slider on a flat surface with low elastic modulus, and optical measurements of lubricant film thickness demonstrate that a transition occurs from EHD to elastic isoviscous lubrication as the speed increases.
Abstract: An experimental study has been conducted of the hydrodynamic lubrication of a spherical slider on a flat surface with low elastic modulus. Optical measurements of lubricant film thickness demonstrate that a transition occurs from EHD to elastic isoviscous lubrication as the speed increases. Observed film thicknesses are in general agreement with recently advanced theoretical predictions. A regime chart is presented which charts the limits of the various regions of lubrication for nominal point contact. Presented at the 32nd Annual Meeting in Montreal, Quebec, Canada, May 9–12, 1977
TL;DR: Fretting wear experiments were conducted with uncoated AISI 9310 mating surfaces and with combinations incorporating a selected coating to one of the mating surfaces by means of a self-lubricating film that developed on the fretting surfaces.
Abstract: Fretting wear experiments were conducted with uncoated AISI 9310 mating surfaces and with combinations incorporating a selected coating to one of the mating surfaces. Wear measurements and SEM observations indicated that surface fatigue, as made evident by spallation and surface crack formation, is an important mechanism in promoting fretting wear to uncoated 9310. Increasing humidity resulted in accelerated fretting and a very noticeable difference in nature of the fretting debris. Of the coatings evaluated, aluminum bronze with a polyester additive was most effective at reducing wear and minimizing fretting damage to the mating uncoated surface by means of a self-lubricating film that developed on the fretting surfaces. Chromium plate performed as an effective protective coating, itself resting fretting and not accelerating damage to the uncoated surface. Presented at the 32nd Annual Meeting in Montreal, Quebec, Canada, May 9–12, 1977
TL;DR: In this article, the effect of balance ratio on stability of a balanced end-face seal was investigated. But the results were limited to the case of laminar, incompressible, isoviscous, and inward flow.
Abstract: End face seals often operate with full fluid film lubrication because of convergence in the direction of leakage through the sealing gap. The degree of convergence can generally be calculated for the seal or designed into it by deflection analysis of the structural components. It is, therefore, necessary to know tile effect of convergence on seal performance. This paper presents results for laminar, incompressible, isoviscous, inward flow through a balanced end face seal. Performance for any degree of convergence of any size and balance ratio of seal can be predicted using the nondimensionalized curves. Results show the significance of each parameter. Of particular importance is the effect of balance ratio on stability of the seal. Presented at the 32nd Annual Meeting in Montreal, Quebec, Canada, May 9–12, 1977
TL;DR: In this paper, a correlation was shown between outer s or s or n or s and metal-metal adhesion, and it was shown that those metals having an electron deficiency in their outer atomic orbitals adhere better than those metals which do not in order to minimize the total free energy and approach a more stable state.
Abstract: The cohesion of metals and their adhesion to other metals are complicated and poorly understood processes. Theories of adhesion have been judged by the use of indirect friction and wear data because of the scarcity of good experimental adhesion data. The adhesion of one metal to another appears to be a manifestation of the electronic configuration of the atoms involved because the cohesive nature of materials results from these atomic forces. Therefore, the atomic binding energies, the distribution of the atomic species in the surface layers, the surface structure, and the crystal lattice disregistration must be influential in metal-metal adhesion. Adhesion is a surface oriented process and, thus, the bulk properties of metals should have only secondary influences. Those metals having an electron deficiency in their outer atomic orbitals should adhere better than those metals which do not in order to minimize the total free energy and approach a more stable state. A correlation is shown between outer s or...
TL;DR: In this article, the friction and wear rate characteristics of 50/50 (weight percent) graphite fiber-polyimide composites were studied by sliding metallic hemispherically tipped riders against disks made from the composites.
Abstract: The friction and wear rate characteristics of 50/50 (weight percent) graphite fiber-polyimide composites were studied by sliding metallic hemispherically tipped riders against disks made from the composites. Two different polyimides and two different graphite fibers were evaluated. Also studied were such variables as the effect of adding 10 percent weight additions of powdered (CF1.1)n CdI2, or CdO; the effect of moisture in an air atmosphere; the effect of temperature; and the effect of different sliding speeds. In general, wear to the metallic riders was negligible and composite wear increased at a constant rate as a function of number of sliding cycles. Presented at the 32nd Annual Meeting in Montreal, Quebec, Canada, May 9–12, 1977
TL;DR: In this paper, the results of 586 sliding-rolling disk scuffing tests conducted over a wide range of sliding and sum velocities, using a straight mineral oil and three different aviation gas turbine synthetic oils, in combination with two different carburized steels and a nitrided steel.
Abstract: This paper summarizes the results of 586 sliding-rolling disk scuffing tests conducted over a wide range of sliding and sum velocities, using a straight mineral oil and three different aviation gas turbine synthetic oils, in combination with two different carburized steels and a nitrided steel. Geometrically-similar disks of two different sizes were tested in two different disk testers of nearly similar designs. In addition to disk size and metallurgy, the surface treatment, surface texture and surface roughness if the disks were also varied. The investigation further covered variations in the oil supply configuration and temperature, as well as the flow rate. Statistical analyses of the scuffing test data have been made. It is shown that the critical contact temperature, defined as that maximum instantaneous surface temperature which results in scuffing at 10 percent probability, may be taken, within the precision of the test data, to be substantially constant for a given oil-metal-surface treatment comb...
TL;DR: In this paper, the authors used infrared spectra on dynamic EHD contacts of several types of fluid to determine the surface and oil-film temperatures, where friction between parallel rough molecules provided the traction.
Abstract: Does a traction fluid have to be a glass or solid under operating conditions. Infrared spectra on dynamic EHD contacts of several types of fluid were used to determine the surface and oil-film temperatures. Polarized spectral runs were made to study molecular alignment. Static glass transition pressures at appropriate temperatures were between 0.1 and 2.0 GPa, with the traction fluid showing the highest. In the EHD contact region, the traction fluid showed both the highest film temperatures as well as the greatest degree of molecular alignment. A plot of the difference between the film and surface temperatures vs shear rate resulted in a master plot valid for all the fluids. From this work, the authors propose a model of 'fluid' traction, where friction between parallel rough molecules provides the traction.
TL;DR: In this article, a mixed-lubrication model was used to study friction and slip in cold rolling of metals using a mixed lubrication model, and the results generally agree with published observations as follows: (1) tension, reduction, oil viscosity, speed, and alloy are important to slip, (2) reduction, o-viscosity, roll radius, speed and alloy, and (3) a decrease in friction does not always produce lower forward slip.
Abstract: Friction and slip in the cold rolling of metals were studied theoretically using a mixed lubrication model. The calculated results generally agree with published observations as follows: (1) tension, reduction, oil viscosity, speed, and alloy are important to slip, (2) reduction, oil viscosity, roll radius, speed, and alloy are important to friction, (3) a decrease in friction does not always produce lower forward slip, (4) Ford's coefficient of friction cannot predict the frictional behavior even qualitatively in certain cases, and (5) slip decreases linearly with increasing speed and viscosity. Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference in Boston, Massachusetts, October 5–7, 1976
TL;DR: In this article, a small laboratory mill was modified to take inserts which were ground in place to the same finish as the roll and the inserts could be removed between the rolling of one strip and the next so that the process of coating buildup could be followed in the scanning electron microscope.
Abstract: An important limitation to the quality of rolled aluminum is the transference of metal from the slab to the roll and back to the surface of the slab during hot rolling, producing defects known as pickup. The way in which the buildup of roll-coating controls pickup has been studied using a small laboratory mill. The top roll of the mill was modified to take inserts which were ground in place to the same finish as the roll. The inserts could be removed between the rolling of one strip and the next so that the process of coating buildup could be followed in the scanning electron microscope. The distribution of aluminum on the surface of the roll-was mapped using the energy dispersive X-ray spectrometer attachment to the microscope. Additional chemical analysis of the coating was obtained by X-ray photo-electron spectroscopy. The coating built up initially as large isolated lumps streaked out in the rolling direction, which become overlaid with an accumulation of much smaller particles. The coaling was found ...
TL;DR: In this article, a moldable polymeric microporous material for use as a lubricant reservoir for rolling element bearings has been studied to determine the parameters which control the rate of lubricant flow.
Abstract: A moldable, polymeric microporous material for use as a lubricant reservoir for rolling element bearings has been studied to determine the parameters which control the rate of lubricant flow. A simplified theory is developed to predict flow rates resulting from body forces or from internal pressure changes. Experimental data and theory are in good agreement. Changes in temperature produce transient changes in flow rate due to an internal pressure change resulting from differential thermal expansion between the lubricant and the polymer matrix. The transience is followed by a steady flow rate due to body forces. Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference in Boston, Massachusetts, October 5–7, 1976
TL;DR: In this paper, the Ferrograph was used to analyze wear debris generated in a sliding elastohydrodynamic contact and the amount of wear debris correlates well with the ratio of film thickness to composite surface roughness.
Abstract: The Ferrograph has been used to analyze wear debris generated in a sliding elastohydrodynamic contact. The amount of wear debris correlates well with the ratio of film thickness to composite surface roughness (Λ ratio). Essentially all of the generated wear particles were of the normal rubbing wear type. Presented at the 32nd Annual Meeting in Montreal, Quebec, Canada, May 9–12, 1977
TL;DR: In this article, the properties of poly(1,1-dihydropentadecafluorooctyl methacrylate) (PFOMA) films are described in terms of their relation to the formulation variables of the PFOMA-solvent system.
Abstract: Films of poly(1,1-dihydropentadecafluorooctyl methacrylate) (PFOMA) cast from fluorinated solvents are inert and not wetted by most organic liquids. They are widely used as barrier film in such applications as confining lubricants to miniature bearing raceways or preventing creep onto critical nonlubricated electric relay contact points. The quality of the films, e.g. thickness, surface texture, and resistance to liquid lubricants, is described in terms of their relation to the formulation variables of the PFOMA-solvent system. Aspects which contribute to optimization of the barrier film properties and the relevance of solvent thermodynamic properties are discussed. Presented at the 32nd Annual Meeting in Montreal, Quebec, Canada, May 9–12, 1977
TL;DR: A rotating beam fatigue technique has been used to determine the effectiveness of additives for mitigating the deleterious effect of a small quantity of water in a mineral oil on steel fatigue life as discussed by the authors.
Abstract: A rotating beam fatigue technique has been used to determine the effectiveness of additives for mitigating the deleterious effect of a small quantity of water in a mineral oil on steel fatigue life. The technique exhibits a high sensitivity to the effect of water contamination and provides a means to investigate wide variations in effectivenss of additives. The utility of the measurements as predictors for performance in rolling contact is considered, a rating equation for the additives is proposed, and the mechanisms by which additives may counteract the effect of water are discussed. Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference in Boston, Massachusetts, October 5–7, 1976
TL;DR: In this paper, three new techniques are proposed to enable friction determination during forging operations, allowing friction measurement over a small but finite increment of deformation, removing the controversy over measuring geometry changes of a barreling surface and, therefore, providing for increase measurement accuracy.
Abstract: For forging operations, process parameters, such as workpiece geometry, forging load, and material properties of the deforming body, can all be measured by well-established techniques. Interface friction, however, is a far more elusive quantity, yet its significant role in determining forging forces and mode of material flow is well-recognized. Three new techniques are proposed to enable friction determination during forging. The first of these permits friction measurement over a small but finite increment of deformation; the second, removes the controversy over measuring geometry changes of a barreling surface and, therefore, provides for increase measurement accuracy; the third technique extends measurement to forging under plane strain conditions and introduces a new approach to the problem. The use of forging to measure flow stress and provide stress-strain data for the material being formed is discussed briefly. Presented at the 32nd Annual Meeting in Montreal, Quebec, Canada, May 9–12, 1977
TL;DR: In this paper, the authors used both a vibratory apparatus and a jet erosion facility to produce spherical particles from wear and erosion on various materials including aluminum and 52100 steel, ranging from 0·5 μ (microns) to 30 μ in diameter.
Abstract: The prediction, control, and prevention of unscheduled downtime due to wear of industrial equipment is an important engineering problem. The characterization of wear particles and the study of the mechanism of their formation will aid in preventive maintenance. Of particular interest is the mechanism of formation of spherical particles during wear and erosion. It has been suggested that cavitation erosion is a mechanism of formation for these spherical particles. Using both a vibratory apparatus and a jet erosion facility, spherical particles were produced on various materials including aluminum and 52100 steel. Special techniques for isolating and mounting the eroded particles were developed. Spheroids ranging from 0·5 μ (microns) to 30 μ in diameter were observed in the vibratory cavitation method both in distilled water and in SAE 10W nondetergent oil. Much larger spheroids up to 150μ in diameter were observed in clusters with the jet erosion method. Scanning electron microscope studies revealed crater...