Normal Impact Model of Rough Surfaces

1992 ◽  
Vol 114 (3) ◽  
pp. 439-447 ◽  
Author(s):  
Wen-Ruey Chang ◽  
Frederick F. Ling
Keyword(s):  
Surface Roughness ◽  
Kinetic Energy ◽  
Surface Topography ◽  
Impact Velocity ◽  
Material Properties ◽  
Rough Surfaces ◽  
Impact Model ◽  
Normal Impact ◽  
Roughness Effects ◽  
Elastic Plastic

An elastic-plastic impact model for spheres is introduced as the basis to study the normal impact of rough surfaces. Statistics is applied to arrive at the ensemble behavior of many unit events alluded above, allowing the investigation of surface roughness effects. Dissipation of kinetic energy increases such as surface roughness, material compliance, and impact velocity is increased. The rebound velocity is shown to be dependent on surface topography and material properties, in addition to impact velocity.

Lubrication of a Porous Bearing With Surface Corrugations

1982 ◽  
Vol 104 (1) ◽  
pp. 127-134 ◽  
Author(s):  
J. Prakash ◽  
K. Tiwari
Keyword(s):  
Surface Roughness ◽  
Hydrodynamic Lubrication ◽  
Rough Surfaces ◽  
Stochastic Theory ◽  
Circular Plates ◽  
Operating Characteristics ◽  
Roughness Effects ◽  
Porous Bearing

The paper considers the surface roughness effects in hydrodynamic porous bearings. On the basis of stochastic theory of hydrodynamic lubrication of rough surfaces developed by Christensen, different forms of Reynolds type equations, as applicable to a general porous bearings are derived for various types of surface roughness pattern. To illustrate the functional effects of surface roughness on the operating characteristics of a porous bearing, the case of nonrotating circular plates in normal approach is analyzed. It is shown that surface roughness may considerably influence the operating characteristics of porous bearings. The direction of the influence, however, depends upon the type of roughness assumed.

Contact Analysis of Multilayered Elastic/Plastic Solids With Rough Surfaces for Decreasing Friction and Wear

2005 ◽  
Author(s):  
Shaobiao Cai ◽  
Bharat Bhushan
Keyword(s):  
Surface Roughness ◽  
Contact Area ◽  
Yield Criterion ◽  
Rough Surfaces ◽  
Three Dimensional ◽  
Surface Displacement ◽  
Maximum Displacement ◽  
Elastic Plastic ◽  
Perfectly Plastic ◽  
Von Mises

A numerical three-dimensional contact model is presented to investigate the contact behavior of multilayered elastic-perfectly plastic solids with rough surfaces. The surface displacement and contact pressure distributions are obtained based on the variational principle with fast Fourier transform (FFT)-based scheme. Von Mises yield criterion is used to determine the onset of yield. The effective hardness is modeled and plays role when the local displacement meet the maximum displacement criterion. Simulations are performed to obtain the contact pressures, fractional total contact area, fractional plastic contact area, and surface/subsurface stresses. These contact statistics are analyzed to study the effects of the layer-to-substrate ratios of stiffness and hardness, surface roughness, and layers thickness of rough, two-layered elastic/plastic solids. The results yield insight into the effects of stiffness and hardness of layers and substrates, surface roughness, and applied load on the contact performance. The layer parameters leading to low friction, stiction, and wear are investigated and identified.

Experimental Verification of an Improved Elastic-Plastic Static Friction Model Including Roughness Effects

2005 ◽  
Author(s):  
Chul-Hee Lee ◽  
Andreas A. Polycarpou
Keyword(s):  
Surface Roughness ◽  
Wear Debris ◽  
Static Friction ◽  
Force Transducer ◽  
Friction Model ◽  
Experimental Measurements ◽  
Roughness Effects ◽  
Experimental Conditions ◽  
Interface Motion ◽  
Elastic Plastic

An experimental study was performed to measure the static friction coefficient under different experimental conditions. These include different surface roughness conditions, the effect of dwell time, the effect of acceleration (sliding velocity) as well as the presence of traces of lubricant and wear debris at the interface. The static friction tester provides accurate measurement of friction, normal and lateral forces at the interface (using a high dynamic bandwidth piezoelectric force transducer) as well as precise motion control and measurement of the interface motion. The experimental measurements were subsequently compared with an improved elastic-plastic rough surface static friction model, and it was found that the model captures the experimental measurements well, especially in terms of surface roughness. However, the data also shows the limitations of the model as it fails to accurately capture the effects of experimental conditions such as the presence of wear debris and start up velocity.

Static Friction Coefficient Model for Metallic Rough Surfaces

1988 ◽  
Vol 110 (1) ◽  
pp. 57-63 ◽  
Author(s):  
W. R. Chang ◽  
I. Etsion ◽  
D. B. Bogy
Keyword(s):  
Friction Coefficient ◽  
Surface Topography ◽  
Material Properties ◽  
Adhesion Force ◽  
Rough Surfaces ◽  
Static Friction ◽  
External Loading ◽  
Height Distribution ◽  
Static Friction Coefficient ◽  
Shear Interface

The friction force required to shear interface bonds of contacting metallic rough surfaces is calculated, taking into account the prestress condition of contacting asperities. The surfaces are modeled by a collection of spherical asperities with Gaussian height distribution. Previous analyses for adhesion force and contact load of such surfaces are used to obtain the static friction coefficient. It is shown that this coefficient is affected by material properties and surface topography, and that it actually depends on the external loading contrary to the classical law of friction.

scholarly journals Adhesive Friction Based on Accurate Elastic-Plastic Finite Element Analysis and n-Point Asperity Concept

2017 ◽  
Vol 11 ◽  
pp. 1-28
Author(s):  
Ajay K. Waghmare ◽  
Prasanta Sahoo
Keyword(s):  
Finite Element Analysis ◽  
Surface Roughness ◽  
Finite Element ◽  
Coefficient Of Friction ◽  
Material Properties ◽  
Asperity Contact ◽  
Element Analysis ◽  
Elastic Plastic ◽  
Plastic Type ◽  
Definition Of

The present work considers analysis of adhesive friction of rough surfaces using n-point asperity concept for statistical definition of surface roughness features, and accurate finite element analysis of elastic-plastic deformation of single asperity contact. The paper describes theoretical study in which whole range of deformation of an n-point asperity viz. from fully elastic, through elastic-plastic, to fully plastic is considered and the intermediate transition regime is treated analytically as well as numerically. Well defined adhesion index and plasticity index are used to study the prospective contact situations arising out of variation in material properties and surface roughness features. Using practical values of material properties and surface roughness parameters, results are obtained for normally applied load, friction force, and coefficient of friction. It is observed that the surfaces undergoing predominantly plastic type of deformation and having moderate to higher adhesion have constant coefficient of friction.

Static Friction Experiments and Verification of an Improved Elastic-Plastic Model Including Roughness Effects

2007 ◽  
Vol 129 (4) ◽  
pp. 754-760 ◽  
Author(s):  
Chul-Hee Lee ◽  
Andreas A. Polycarpou
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Wear Debris ◽  
Normal Load ◽  
Static Friction ◽  
Displacement Rate ◽  
Experimental Measurements ◽  
Roughness Effects ◽  
Elastic Plastic ◽  
Static Friction Coefficient

An experimental study was conducted to measure the static friction coefficient under constant normal load and different interface conditions. These include surface roughness, dwell time, displacement rate, as well as the presence of traces of lubricant and wear debris at the interface. The static friction apparatus includes accurate measurement of friction, normal and lateral forces at the interface (using a high dynamic bandwidth piezoelectric force transducer), as well as precise motion control and measurement of the sliding mass. The experimental results show that dry surfaces are more dependent on the displacement rate prior to sliding inception compared to boundary lubricated surfaces in terms of static friction coefficient. Also, the presence of wear debris, boundary lubrication, and rougher surfaces decrease the static friction coefficient significantly compared to dry smooth surfaces. The experimental measurements under dry unlubricated conditions were subsequently compared to an improved elastic-plastic static friction model, and it was found that the model captures the experimental measurements of dry surfaces well in terms of the surface roughness.

Surface Roughness Effects in Infinitely Long Porous Journal Bearings

1999 ◽  
Vol 121 (1) ◽  
pp. 139-147 ◽  
Author(s):  
K. Gururajan ◽  
J. Prakash
Keyword(s):  
Surface Roughness ◽  
Journal Bearing ◽  
Hydrodynamic Lubrication ◽  
Rough Surfaces ◽  
Stochastic Theory ◽  
Journal Bearings ◽  
Roughness Effects ◽  
Effect Of Surface

Christensen’s stochastic theory of hydrodynamic lubrication of rough surfaces is used to study the effect of surface roughness in an infinitely long porous journal bearing operating under steady conditions. It is shown that the surface roughness considerably influences the bearing performance; the direction of the influence depends on the roughness type.

Adhesion Model for Metallic Rough Surfaces

1988 ◽  
Vol 110 (1) ◽  
pp. 50-56 ◽  
Author(s):  
W. R. Chang ◽  
I. Etsion ◽  
D. B. Bogy
Keyword(s):  
Surface Roughness ◽  
Surface Energy ◽  
Adhesion Force ◽  
Rough Surfaces ◽  
Contact Model ◽  
External Loading ◽  
Elastic Plastic ◽  
Adhesion Model ◽  
Very High

An improved DMT adhesion model in conjunction with an elastic-plastic contact model is used to study adhesion of contacting metallic rough surfaces. The effects of surface roughness and surface energy of adhesion on the pull-off force and on the significance of the adhesion force are investigated. It is shown that for clean surfaces the adhesion is quite large even for relatively rough surfaces. Adhesion is negligible only for contaminated rough surfaces or at very high external loading.

Measurements and Computations of Compressible Flow Through a Turbine Cascade With Surface Roughness

2006 ◽  
Author(s):  
Lan Qin Yuan ◽  
Richard J. Kind
Keyword(s):  
Surface Roughness ◽  
Compressible Flow ◽  
Rough Surfaces ◽  
Surface Flow ◽  
Turbine Cascade ◽  
Roughness Effects ◽  
Near Surface ◽  
Wall Functions ◽  
Flow Through ◽  
Viscous Flow Field

Experiments and computations have been carried out for a high-pressure turbine cascade having bands of roughness on the blade surfaces, for cascade-exit Mach numbers ranging from 0.4 to 1.13 Tests were carried out with three different relative roughness heights as well as with smooth surfaces. The results comprise profile-loss coefficients and deviation angle. Corresponding flow computations were done using the Fluent 6.0 CFD code with the Spalart-Almaras turbulence model and wall functions to model the near-surface flow. Good agreement was found between the experimental and computational results, especially with regard to trends with Mach number, roughness height and roughness-band configuration. This indicates that current computational methods, which use essentially the same approach to model surface-roughness effects as validated for incompressible flow, can give good predictions of compressible flow over rough surfaces, including details of the viscous flow field. The experimental data constitutes a valuable resource for future efforts to improve prediction capabilities for flows involving rough surfaces.

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