Showing papers in "Journal of Tribology-transactions of The Asme in 1992"
TL;DR: In this paper, a theoretical model of corrugated foil strip (bump foil) deformation in compliant foil bearings and dampers is presented, where the friction forces between bump foils and the housing or the lop foil, local interaction forces, variable load distributions, and bump geometries are taken into consideration.
Abstract: This paper presents a theoretical model of corrugated foil strip (bump foil) deformation in compliant foil bearings and dampers. The friction forces between bump foils and the housing or the lop foil, local interaction forces, variable load distributions, and bump geometries are taken into consideration. Following the trend of earlier published experimental data, the bumps near the fixed end have a much higher predicted stiffness (lower deflection) than those near the free end
181 citations
148 citations
TL;DR: In this article, a mathematical model for piston skirls in mixed lubrication is presented, taking into account the effects of surface waviness, roughness, piston skirling surface profile, bulk elastic deformation and thermal distortion on piston motion, lubrication and friction.
Abstract: This paper presents a mathematical model for piston skirls in mixed lubrication. It lakes into account the effects of surface waviness, roughness, piston skirl surface profile, bulk elastic deformation and thermal distortion of both piston skirls and cylinder bore on piston motion, lubrication and friction. The corresponding computer program developed can be used to calculate the entire piston trajectory and the hydrodynamic and contact friction forces as functions of crack angle under engine running conditions
146 citations
142 citations
TL;DR: In this article, the operating characteristics of four-shoe tilling-pad journal bearings of 100 mm diameter and 70 mm length were determined on an experimental device, where the load, between pad configuration, varies from 0 to 10,000 N and the rotational speed is up to 4000 rpm.
Abstract: Operating characteristics of four-shoe tilling-pad journal bearings of 100 mm diameter and 70 mm length are determined on an experimental device The load, between pad configuration, varies from 0 to 10,000 N and the rotational speed is up to 4000 rpm Forty thermocouples are used in order to measure bearing element temperatures (babbitt, shaft, housing and oil baths) The influence of operating conditions and preload ratio on bearing performances are studied
117 citations
TL;DR: In this article, the plane-strain contact problem of an elastic half-space indented by a nominally flat rigid surface having a finite number of regularly spaced cylindrical asperities is investigated using the finite element method to gain an understanding of the interactions in multi-asperity contacts.
Abstract: The plane-strain contact problem of an elastic half-space indented by a nominally flat rigid surface having a finite number of regularly spaced cylindrical asperities is investigated using the finite element method to gain an understanding of the interactions in multi-asperity contacts. The significance of the number and spacing of asperities on the contact behavior at the center and edges of the interfacial region is examined
104 citations
TL;DR: In this article, the effects of surface kinematic conditions on micro-elastohydrodynamic lubrication (micro-EHL) were investigated under rolling and/or sliding point contact conditions using the optical interferometry technique.
Abstract: The effects of surface kinematic conditions on micro-elastohydrodynamic lubrication (micro-EHL) are investigated under rolling and/or sliding point contact conditions using the optical interferometry technique. A long bump of chromium sputtered on the surface of a highly polished ball is used as a model asperity. It is shown that the film thickness distribution or the elastic deformation of the bump is influenced significantly by the surface kinematic conditions and the orientation of the bump
104 citations
TL;DR: In this article, the results of an elastohydrodynamic lubrication (EHL) analysis of an elliptical contact between a rough, stationary surface and a smooth, moving surface are described.
Abstract: The paper describes the results of an elastohydrodynamic lubrication (EHL) analysis of an elliptical contact between a rough, stationary surface and a smooth, moving surface. The roughness consists of two-dimensional grooves/ridges aligned in a direction perpendicular to that of lubricant entrainment, and is sinusoidal in profile with two scales of wavelength and amplitude. The main feature of these results is the significant degree of asperity deformation and corresponding ripple in the pressure distribution
102 citations
TL;DR: In this article, the authors show that the formation of large wear particle agglomerates caused an increase in the amount of plowing and often a concurrent increase in friction coefficient, while the newly formed wear particles simply got entrapped in surface microgrooves and were immediately removed from the sliding interface before their subsequent growth by agglomation.
Abstract: The hypothesis that one of the primary roles of an effective lubricant is to prevent wear particle agglomeration, thus reduce the plowing of the interfaces by the particles, and lower the frictional force, has been tested through a series of experiments and modeling. The friction coefficient, and the interfacial separation of the sliding surfaces due to entrapped wear particles, were measured on a number of sliding pairs in both dry and lubricated sliding. The results showed that the particle size, even during a single sliding test, did not remain constant but increased as sliding progressed. This increase in the wear particle size was found to be due not to the formation of larger wear particles but to the agglomeration of the small wear particles produced during sliding. The formation of large wear particle agglomerates caused an increase in the amount of plowing and often a concurrent increase in the friction coefficient. When one of the sliding surfaces was textured with undulations, no wear particle agglomeration was observed. The newly formed wear particles simply got entrapped in surface microgrooves and were immediately removed from the sliding interface before their subsequent growth by agglomeration. It was further shown that “good” lubricants prevented agglomeration, thus the friction coefficient remained more or less at the initial low value. Both the dry and lubricated sliding test results are presented and discussed in light of the analytical models based on the plastic deformation of the individual wear particles and the slip-line field analysis of the wear particle agglomerate.
98 citations
TL;DR: In this article, a numerical model for the two-dimensional dry, frictionless contact of two elastic bodies with real rough surfaces, where one body has a rigidly bonded surface layer, is presented.
Abstract: A numerical model for the two-dimensional dry, frictionless contact of two elastic bodies with real rough surfaces, where one body has a rigidly bonded surface layer, is presented. The model uses surface profile data directly recorded with a stylus measuring instrument and is suitable for use on a microcomputer. Verification of the accurary of the model by reproduction of test case results is presented. Contact pressure distributions for layers of varying thickness and elastic modulus are presented
95 citations
TL;DR: In this paper, the influence of surface roughness on the pressure profile and film thickness in a steady state EHL line contact is investigated using input from an actually measured roughness profile in the calculations.
Abstract: In this paper the influence of surface roughness on the pressure profile and film thickness in a steady state EHL line contact is investigated using input from an actually measured roughness profile in the calculations. Pressure profiles and film shapes for different load conditions are shown. The presented results strongly indicate that in the steady state situation considered here a significant deformation of the roughness profile occurs. As a result the often used λ parameter being the ratio of film thickness and standard deviation of the roughness (h/σ) with σ based on the undeformed roughness profile may give misleading information as far as the effect of the roughness on pressure and film shape is concerned.
TL;DR: In this article, a linear theoretical model for the vibrations of a shaft bearing system caused by ball bearing geometrical imperfections is presented for low and medium speeds where ball centrifugal forces can be neglected.
Abstract: A linear theoretical model is presented for the vibrations of a shaft bearing system caused by ball bearing geometrical imperfections. It is valid for low and medium speeds where ball centrifugal forces can be neglected. The excitation forces from each bearing are calculated and can serve as input to suitable rotor dynamics programs. Imperfections covered are radial and axial waviness of outer and inner rings, ball waviness and diameter distribution, nonuniform cage pocket distribution
TL;DR: In this paper, the authors derived closed-form expressions in terms of elementary functions for spherical Hertzian contact of elastic bodies possessing transverse isotropy in the form of Coulomb friction, where the shear stress is proportional to the contact pressure.
Abstract: This paper gives closed-form expressions in terms of elementary functions for the title problem of spherical Hertzian contact of elastic bodies possessing transverse isotropy. Traction in the contact region is also included in the form of Coulomb friction; thus the shear stress is proportional to the contact pressure. The present expressions derived here by integration of the point force Green's functions are simpler and easier to apply than equiualent expressions which have previously been given
TL;DR: In this paper, rolling element bearing fatigue spalls were propagated for several test conditions well beyond the laboratory criteria of 6.5 square millimeters used in the author's laboratory, which can be used to gain an appreciation of the total useful life of a bearing and to allow a more accurate diagnosis of fatigue spall damage.
Abstract: Rolling element bearing fatigue spalls were propagated for several test conditions well beyond the laboratory criteria of 6.5 square millimeters used in the author's laboratory. Usually mare than one mode of fatigue spall propagation is involued when large spalls develop. The information provided in this paper can be used to gain an appreciation of the total useful life of a bearing and to allow a more accurate diagnosis of fatigue spall damage
TL;DR: The authors reviewed eleven published spalling fatigue life models to identify consensus parameters and relationships and compare model strengths and limitations, as a basis for the construction of a simplified, readily calculated engineering model encompassing the major life variables, based on explicit assumptions and derivations.
Abstract: This paper reviews eleven published spalling fatigue life models, to identify consensus parameters and relationships and to compare model strengths and limitations, as a basis for the construction of a simplified, readily calculated engineering model encompassing the major life variables, based on explicit assumptions and derivations.
TL;DR: In this paper, a thermo-hydrodynamic analysis for a face-to-face double seal configuration was performed and the energy equation was solved analytically and the radial temperature variation was presented by an implicit equation.
Abstract: A thermo-hydrodynamic analysis is performed for a face-to-face double seal configuration. Temperature and viscosity variations both across and along the sealing gap are considered and realistic boundary conditions are considered. The energy equation is solved analytically and the radial temperature variation is presented by an implicit equation. This approach enables analytical parametric investigation and gives better understanding of the effects of various parameters on the seal's thermal behavior
TL;DR: Friction and wear experiments were conducted on high purity alpha-alumina sliding against a similar material in air under different contact loads and at temperatures ranging from 23 o C to 900 o C.
Abstract: Friction and wear experiments were conducted on high purity alpha-alumina sliding against a similar material in air under different contact loads and at temperatures ranging from 23 o C to 900 o C. Experimental results indicate that tribochemical reactions between water vapor and alpha-alumina at room temperature produce alu minum hydroxide which results in relatively low coefficients of friction and low wear rates. Both the coefficient of friction and the wear rate of alumina were low at intermediate temperatures (200 o C to 800 o C), if the contact stress was below a threshold value
TL;DR: In this article, non-Newtonian effects of multigrade engine oils in dynamically loaded crankshaft bearings are analyzed and the main focus is on the shear-thinning effect.
Abstract: Non-Newtonian effects of multigrade engine oils in dynamically loaded crankshaft bearings are analyzed. The main focus of this work is on the shear-thinning effect. Viscoelastic effects are also considered over a limited range of the relaxation time. It has been shown that the same generalized Reynolds equation used in the Thermohydrodynamic (THD) analysis can be used for analyzing the shear-thinning effects as well. Consequently the shear thinning effect and the THD effect can be treated together
TL;DR: In this paper, a model of head/tape contact based on measurements of average contact pressure versus average head/Tape spacing was developed and incorporated into a numerical simulation of the head/to-tape interface.
Abstract: Partial contact at the head/tape interface is investigated as a function of changes in the head/tape spacing due to asperity compression during contact. A model of head/tape contact, based on measurements of average contact pressure versus average head/tape spacing, is developed and incorporated into a numerical simulation of the head/tape interface. Numerical calculations of head/tape spacing with partial contact are verified by interferometric measurements
TL;DR: In this article, a complete solution is obtained for elastohydrodynamically lubricated conjunctions in line contacts considering the effects of temperature and the non-Newtonian characteristics of lubricants with limiting shear strength.
Abstract: A complete solution is obtained for elastohydrodynamically lubricated conjunctions in line contacts considering the effects of temperature and the non-Newtonian characteristics of lubricants with limiting shear strength The complete fast approach is used to solve the thermal Reynolds equation by using the complete circular non-Newtonian fluid model and considering both velocity and stress boundary conditions The reason and the occasion to incorporate stress boundary conditions for the circular model are discussed
TL;DR: In this article, a real-lime, rolling-element bearing dynamics simulation was written (PADRE-Planar Analysis of a Dynamic Retainer) for rapid evaluation of key bearing design factors.
Abstract: Factors contributing to the dynamic instability of ball retainers in precision bearings were investigated. A real-lime, rolling-element bearing dynamics simulation was written (PADRE-Planar Analysis of a Dynamic Retainer) for rapid evaluation of key bearing design factors. This code permits economic screening of a large number of bearing geometric parameters as a prelude to other more comprehensive dynamic bearing codes
TL;DR: In this paper, the roughness measurements of a magnetic tape, a biaxially oriented poly(ethylene terephthalate) (PET) substrate, a tape head and a rigid disk slider were made by an atomic force microscope (AFM) and a non-contact optical profiler (NOP).
Abstract: Roughness measurements of a magnetic tape, a biaxially oriented poly(ethylene terephthalate) (PET) substrate, a tape head and a rigid-disk slider were made by an atomic force microscope (AFM) and a non-contact optical profiler (NOP). The lateral resolution of the surface topographs ranges from 1 μm (for NOP) down to 1 nm (for AFM). The AFM images show submicron features of the surface that are characteristic of the manufacturing processes. Some of the statistical roughness parameters conventionally used in theories of contact mechanics showed strong dependence on instrument resolution
TL;DR: In this paper, the effect of the clamping ratio and orifice size on the performance of slippers in axial piston pumps and motors was investigated and it was shown that slippers operate perfectly satisfactorily with the orifice blanked and indeed, are generally most stable in this condition.
Abstract: The paper presents the results of an experimental and theoretical investigation of the effect of clamping ratio and orifice size on the performance of slippers in axial piston pumps and motors. Polishing of the running face to a slightly convex form appears to be essential for successful operation under all conditions. It is shown that slippers operate perfectly satisfactorily with the orifice blanked and, indeed, are generally most stable in this condition. Introduction of the orifice in under-clamped slippers increases the clearance. However it can also destabilise the slipper resulting in the slipper becoming sensitive to the effect of tilting couples. The effect on overclamped designs is more complex depending on the precise value of clamping ratio and on the width of the slipper land.
TL;DR: In this paper, the basic principles controlling the development of a lubricant film in lip seals are studied using a micro-hydrodynamic model, which takes into account the visco-elastic effects of the rubber on the developing of the sealing pressure.
Abstract: The lubricant film developed in rotary lip seals is a vital element in achieving long-lasting seals with low friction. In this paper the basic principles controlling the development of a lubricant film in lip seals are studied using a micro-hydrodynamic model. This model takes into account the visco-elastic effects of the rubber on the development of the sealing pressure. Central to the model's hypothesis is the assumption of the predominant action of the surface micro-geometry in the formation of the lubricant film
TL;DR: In this paper, the authors calculated the stress intensity factors for short straight and branched subsurface cracks subjected to a Hertzian loading by the finite element method and showed that the straight crack is subjected to pure mode II loading, whereas the branced crack was subjected to both mode I and mode II, with ΔK I /ΔK II < 0.25
Abstract: The stress intensity factors for short straight and branched subsurface cracks subjected lo a Hertzian loading are calculated by the finite element method. The effect of crack face friction on stress intensity factors is considered for both straight and branched cracks. The calculations show that the straight crack is subjected to pure mode II loading, whereas the branched crack is subjected to both mode I and mode II, with ΔK I /ΔK II <0.25
TL;DR: In this paper, the applied alternating shear stress field is used to define critical stress as a function of depth and computes life as crack propagation time through this field, where the critical stress is defined as the probability of a crack being formed.
Abstract: This paper presents the new model that uses the applied alternating shear stress field to define the critical stress as a function of depth, and computes life as crack propagation time through this field.