A5102990015- Adhesion, Friction, and Surface Interactions
- Gear and Bearing Dynamics Analysis
- Tribology and Lubrication Engineering
- Mechanical stress and fatigue analysis
- Force Microscopy Techniques and Applications
- Tribology and Wear Analysis
- Tropical and Extratropical Cyclones Research
- Electrical Contact Performance and Analysis
- Metallurgy and Material Forming
- Oceanographic and Atmospheric Processes
- Ocean Waves and Remote Sensing
- Marine and fisheries research
- Surface Roughness and Optical Measurements
- Brake Systems and Friction Analysis
- Lubricants and Their Additives
- Metal Forming Simulation Techniques
- Metal and Thin Film Mechanics
- Marine Biology and Ecology Research
- Numerical methods in engineering
- Rock Mechanics and Modeling
- Textile materials and evaluations
- Contact Mechanics and Variational Inequalities
- Computational Geometry and Mesh Generation
- Railway Engineering and Dynamics
- Coastal and Marine Dynamics
University of Cambridge
2013-2023
Wesleyan University
2006
DePauw University
2006
Bridge University
1958-2002
The University of Queensland
1989-2000
Virginia Tech
1981
University of Salford
1968-1970
University of Liverpool
1967-1969
It is usually assumed that the real area of contact between two nominally flat metal surfaces determined by plastic deformation their highest asperities. This leads at once to result directly proportional load and independent apparent area—a with many applications in theories electric contacts friction. Archard pointed out could not be universal rule, introduced a model which showed that, contrary earlier ideas, even purely elastic contact. paper describes new theory contact, more closely...
Most models of surface contact consider the roughness to be on one contacting surfaces only. The authors give a general theory between two rough plane surfaces. They show that important results previous are unaffected: in particular, load and area remain almost proportional, independently detailed mechanical geometrical properties asperities. Further, single-rough-surface model can always found which will predict same laws as given two-rough-surface model, although required may unrealistic....
The Hertzian theory of elastic contact between spheres is extended by considering one the to be rough, so that occurs, as in practice, at a number discrete microcontacts. It found results are valid sufficiently high loads, but lower loads effective pressure distribution much and extends further than for smooth surfaces. relevance physical-contact friction electric considered.
The relation between the area of contact and constriction resistance which holds for a single circular spot is widely used in electric theory, although normal mode by large number microcontacts. A method finding cluster microcontacts derived, it shown that may be regarded as sum parallel an interaction term often related to extent not or size individual contacts. close found assuming entire covered conducting spot.
Bradley (1932) showed that if two rigid spheres of radii R1 and R2 are placed in contact, they will adhere with a force 2πΔRγ, where R is the equivalent radius R1R1/(R1+R2) Δγ surface energy or ‘work adhesion’ (equal to γ1+γ2-γ12). Subsequently Johnson et al. (1971) (JKR theory) by Griffith argument (assuming contact over circle introduces -πa2Δγ) how Hertz equations for elastic modifed energy, needed separate equal (3/2)πΔRγ, which independent modulus so appears be universally applicable...
Abstract The experimental study of adhesion between common solids is bedevilled by the fad that, with exception cleaved mica, inevitable roughness surfaces greater than range surface forces. A new situation arose technique casting low-modulus rubber an optically smooth surface. When placed in contact each other, or a hard like plate glass, such specimens are sufficiently compliant to make intimate throughout whole their apparent area. High then observed; fact measured force required separate...
A study has been made of the friction hard spheres and cones on a well lubricated rubber surface under conditions where relatively large deformations are produced. It is found that with sliding almost same as rolling friction. Earlier work shown in latter case arises primarily from hysteresis losses it concluded that, experimental described, main source cause. With conical sliders not possible to make direct comparison experiments, but simple calculation suggests here again largely due...
Previous work on the mechanism of rolling friction has shown that it is mainly due to elastic hysteresis losses in elements. Under conditions uniform tension or torsion generally assumed energy dissipated by a constant fraction (the loss factor) introduced during cycle. This input been calculated for hard cylinder sphere rubber, and with above assumption expressions have obtained friction. These predict correctly dependence load, ball diameter constants rubber. However, absolute values...
The experiments in part I on the behaviour of contact between metals when large currents pass interface have yielded results which cannot be explained by classical theory constriction resistances. In an attempt to provide account this anomalous a new mathematical treatment general problem electrical heating conductors has been developed. This gives, under appropriate conditions, concise derivation all main accepted theory; addition it leads three conclusions. First, is shown that finding...
The problem of how contact between elastic spheres is modified by the surface forces which act them becoming great interest with possibility studying such contacts experimentally in atomic force microscope and apparatus. Experiments are frequently interpreted help JKR adhesion theory, action represented change energy involved uniting or separating two surfaces. This has drawbacks: it strictly valid only when Tabor parameter large, though fact appears that condition sufficient, gives no...
By assuming the contact geometry in elastohydrodynamic lubrication (EHL) to be that of an infinitely long with given nominal film thickness and mean pressure considering elastic displacements separate components initial roughness, it is possible extend Greenwood Johnson analysis for sinusoidal any two-dimensional roughness. For typical EHL pressures viscosity effects are negligible, so Reynolds equation can linearized solved analytically; solution provides a criterion relate amplitudes...
The analysis of grease-lubricated rolling element bearings is presented. Experimentally determined flow curves for grease are found to be well correlated by the Herschel-Bulkley model equation. A theory predicting roller film thickness based on assumed derived. Experimental results show that will develop a larger than base oil at first, but falls during until it reaches steady usually lower its oil. This effect shown depend degree shear degradation grease, resulting curve, and temperature...
The development of EHL theory from its tentative beginnings is outlined, with an account how Ertel explained relation to Hertz contact theory. problems caused by the failure early numerical analysts understand that film thickness depends on only two variables are emphasised, and answers form H = F ( P , S ) given. Early methods measuring described, but these became archaic optical EHL. behaviour surface roughness as it passes through high pressure region suffers elastic deformation...
Classical fracture mechanics applied to a viscoelastic material states that the critical stress-intensity factor at which crack propagates depends on instantaneous elastic modulus of solid, and provides no mechanism for speed dependence apparent surface energy. This suggests any must be because energy itself is speed-dependant. Schapery (1975) has explained how by using Barenblatt concept mechanics, involving forces instead alone, found. Here, Schapery's principles are particular case...