The Effects of Surface Roughness and Topography on the Contact Behavior of Elastic Bodies

1994 ◽  
Vol 116 (4) ◽  
pp. 804-810 ◽  
Author(s):  
Ning Ren ◽  
Si C. Lee
Keyword(s):  
Surface Roughness ◽  
Root Mean Square Roughness ◽  
Asperity Contact ◽  
Performance Variables ◽  
Elastic Bodies ◽  
Real Area Of Contact ◽  
Wide Range ◽  
Autocorrelation Length ◽  
Mathematical Relationships ◽  
Effect Of Surface

The real area of contact, average gap, and mean asperity contact pressure are important variables for understanding friction, wear, and lubrication in contacting systems. They are known as “performance variables.” Contact simulations were conducted for a wide range of surface topographies and an extensive amount of information was generated. Using this information, the performance variables were curve fitted and convenient mathematical relationships were formulated. The surfaces used in the simulations were numerically generated and they varied widely in statistical roughness properties, ranging from isotropic to strongly anisotropic. The effect of surface roughness on the performance variables were studied using three parameters—composite Root Mean Square roughness (σ), autocorrelation length (λx*), and asperity aspect ratio (γ).

A Relationship Between Autocorrelation Length and Adhesive Friction Behavior of Rough Surfaces

2005 ◽  
Author(s):  
Yilei Zhang ◽  
Sriram Sundararajan
Keyword(s):  
Rough Surface ◽  
Spatial Information ◽  
Roughness Parameter ◽  
Hertzian Contact ◽  
Root Mean Square Roughness ◽  
Friction Behavior ◽  
The Real ◽  
Real Area Of Contact ◽  
Autocorrelation Length ◽  
Real Area

Autocorrelation Length (ACL) is a surface roughness parameter that provides spatial information of surface topography that is not included in amplitude parameters such as Root Mean Square roughness. This paper presents a statistical relation between ACL and the real area of contact, which is used to study the adhesive friction behavior of a rough surface. The influence of ACL on profile peak distribution is studied based on Whitehouse and Archard’s classical analysis, and their results are extended to compare profiles from different surfaces. With the knowledge of peak distribution, the real area of contact of a rough surface with a flat surface can be calculated using Hertzian contact mechanics. Numerical calculation shows that real area of contact increases with decreasing of ACL under the same normal load. Since adhesive friction force is proportional to real area of contact, this suggests that the adhesive friction behavior of a surface will be inversely proportional to its ACL. Results from microscale friction experiments on polished and etched silicon surfaces are presented to verify the analysis.

Thermohydrodynamic Analysis of Submerged Oil Journal Bearings Considering Surface Roughness Effects

1997 ◽  
Vol 119 (1) ◽  
pp. 100-106 ◽  
Author(s):  
J. Ramesh ◽  
B. C. Majumdar ◽  
N. S. Rao
Keyword(s):  
Surface Roughness ◽  
Thermal Effects ◽  
Hydrodynamic Pressure ◽  
Height Distribution ◽  
Asperity Contact ◽  
Roughness Effects ◽  
State Behavior ◽  
Total Load ◽  
Contact Loads ◽  
Effect Of Surface

A theoretical study of a submerged oil journal bearing is made considering surface roughness and thermal effects. The total load-supporting ability under such condition is due to the thermohydrodynamic as well as the asperity contact pressure. The effect of surface roughness and viscosity-temperature dependency on hydrodynamic pressure has been found by solving the average Reynolds equation, energy equation and heat conduction equations simultaneously. The cavitation model of Jacobsson-Floberg has been modified to take the surface roughness effects into consideration. A parametric study of steady-state behavior has been carried out. Finally, the isothermal, thermohydrodynamic, and contact loads for a model bearing have been calculated, assuming the surface height distribution as Gaussian.

Effect of surface topography associated with arbitrary velocity direction on the lubrication film thickness in elliptical contacts

2018 ◽  
Vol 70 (2) ◽  
pp. 444-452 ◽  
Author(s):  
Wei Pu ◽  
Jiaxu Wang ◽  
Guangwu Zhou ◽  
Ke Xiao ◽  
Junyang Li
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Surface Topography ◽  
Surface Velocity ◽  
Content Type ◽  
Lubrication Film ◽  
Wide Range ◽  
Lubricating Property ◽  
Inclined Angle ◽  
Effect Of Surface

Purpose The purpose of this study is to describe and observe the effect of surface topography associated with arbitrary directions of rolling and sliding velocities on the performance of lubricating films in elliptical contacts. Design/methodology/approach The most recently published mixed elastohydrodynamic (EHL) model by Pu and Zhu is used. Three different machined rough surfaces are discussed and the correlated inclined angle of surface velocity varies from 0° to 90° in the analyzed cases. These cases are carried out in a wide range of speeds (five orders of magnitude) while the simulated lubrication condition covers full-film and mixed EHL down to the boundary lubrication. Findings The results indicate that the variation of the average film thickness corresponding to different entrainment angles is distinct from those without considering surface roughness. In addition, the surface topography appears to have an immense effect on the lubrication film thickness in the exceptive situation. Originality/value This paper has not been published previously. Surface roughness has attracted much attention for many years owing to the significant influence on lubricating property. However, previous studies mainly focus on the counterformal contact with the same direction between surface velocity and principal axis of the contact zone. Little attention has been paid to the specific condition with the arbitrary direction of rolling and sliding velocities found in hypoid gears and worm, and some other components. The purpose of this study is to describe and observe the effect of surface topography associated with arbitrary directions of rolling and sliding velocities on the performance of lubricating films in elliptical contacts based on the most recently published mixed EHL model by Pu and Zhu.

Effect of Surface Orientation and Off-Angle on Surface Roughness and Electrical Properties of p-Type Impurity Implanted 4H-SiC Substrate after High Temperature Annealing

2006 ◽  
Vol 527-529 ◽  
pp. 835-838 ◽  
Author(s):  
Akimasa Kinoshita ◽  
Makoto Katou ◽  
Miwa Kawasaki ◽  
Kazutoshi Kojima ◽  
Kenji Fukuda ◽  
...  
Keyword(s):  
Surface Roughness ◽  
High Temperature ◽  
Annealing Temperature ◽  
Surface Orientation ◽  
Free Carrier ◽  
Root Mean Square Roughness ◽  
Mean Square ◽  
High Temperature Annealing ◽  
P Type ◽  
Effect Of Surface

We investigate the effect of surface orientation and off-angle for Al-implanted 4H-SiC samples after high temperature annealing. The samples are obtained from a 4H-SiC (0001) substrate 8° off-angled (Si-face 8°off), and (000-1) substrates 8° (C-face 8°off), 4° (C-face 4°off) and less than 1° off-angled (C-face ~1°off). An n-type epitaxial layer is deposited on all substrates. Multiple implantations of Al+ (30~200keV) are carried out at 600°C. The total dose is 8.6 × 1015 cm-2. The Al-implanted samples are annealed in Ar ambient at 1580°C, 1700°C and 1800°C for 30s using the hybrid super rapid thermal annealing (HS-RTA) equipment. In this study, sheet resistance (Rs), free carrier concentration (Ns), Hall mobility (μ) and root-mean square roughness (Rrms) are used to evaluate the Al-implanted samples after high temperature annealing. Rs for all Al-implanted samples after annealing at 1800°C for 30s is around 18k/. Rrms for the Al-implanted C-face samples after annealing at 1800°C increases with increasing off-angle. Rrms for the Al-implanted Si-face 8°off sample after annealing increases with annealing temperature. Rrms for the C-face ~1°off Al-implanted sample after annealing at 1800°C is lower than that for the Si-face 8°off Al-implanted sample after annealing at 1700°C, moreover Rs for the C-face ~1°off sample after annealing at 1800°C is about 10% of that for the Si-face 8°off Al-implanted sample after annealing at 1700°C. It is shown that the C-face ~1°off sample is useful to fabricate a p+ region with low Rs and low Rrms. If C-face 4H-SiC is used to fabricate devices, devices made on C-face 4H-SiC with low off angle are expected to decrease any problems caused by increase of surface roughness after high temperature annealing (~1800°C).

scholarly journals PIV Measurements of the Wake Formation from a Rough Flat Plate

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Sean Lawrence ◽  
Callum Atkinson ◽  
Julio Soria
Keyword(s):  
Surface Roughness ◽  
Flat Plate ◽  
High Speed ◽  
Large Scale ◽  
Near Wake ◽  
Image Velocimetry ◽  
Wide Range ◽  
Smooth Body ◽  
And Performance ◽  
Effect Of Surface

Wake flows are prevalent in a wide range of engineering applications and their behaviour can significantly impact engineering design and performance. A considerable body of work exists on smooth body wake structures and flows over rough bodies, however, there is a lack of fundamental physical understanding of the amalgamation of the two fields. Two-component two-dimension particle image velocimetry (2C-2D PIV) is used to investigate the effect of surface roughness on the formation of large scale structures in the near wake of a thin flat plate. Both high-speed and low-speed, high-resolution PIV setups have been used to investigate the effect of surface roughness on the boundary layer and the near wake of the plate to gain insight into the underlying physical connection between these regions.

Effect of Surface Roughness on Elastohydrodynamic Line Contact

1982 ◽  
Vol 104 (3) ◽  
pp. 401-407 ◽  
Author(s):  
B. C. Majumdar ◽  
B. J. Hamrock
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Strain Analysis ◽  
Elastohydrodynamic Lubrication ◽  
Asperity Contact ◽  
Pressure Dependent Viscosity ◽  
Surface Irregularities ◽  
Dependent Viscosity ◽  
Contact Pressures ◽  
Effect Of Surface

A numerical solution of an elastohydrodynamic lubrication (EHL) contact between two long, rough surface cylinders is obtained. A theoretical solution of pressure distribution, elastohydrodynamic load, and film thickness for given speeds and for lubricants with pressure-dependent viscosity, material properties of cylinders, and surface roughness parameters is made by simultaneous solution of an elasticity equation and the Reynolds equation for two partially lubricated rough surfaces. The pressure due to asperity contact is calculated by assuming a Gaussian distribution of surface irregularities. The elastic deformation is found from hydrodynamic and contact pressures by using plane strain analysis. The effect of surface roughness on EHL loads, speeds, and central film thicknesses is studied. The results indicate that for a constant central film thickness (1) increasing the surface roughness decreases the EHL load and (2) there is little variation in minimum film thickness as the surface roughness is increased.

Effect of surface roughness topography on percolation characteristic of contact interface

2020 ◽  
pp. 135065012097735
Author(s):  
Tong Zhang ◽  
Xiaojun Liu ◽  
Yan Zhang ◽  
Jiaxin Ye ◽  
Wei Wang ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Percolation Threshold ◽  
Critical Pressure ◽  
Rough Surfaces ◽  
Glass Plate ◽  
Peak Height ◽  
Elastic Contact ◽  
Contact Interface ◽  
Autocorrelation Length ◽  
Effect Of Surface

The contact geometry of rough surfaces markedly affects the functional properties such as sealing and lubrication. The effect of surface roughness on the percolation characteristic of elastic contact was studied. The elastic contact of randomly rough surfaces with a glass plate was performed using four different surface roughnesses of silicone rubber blocks as specimens. The results illustrate that the percolation threshold was significantly affected by the valley morphology of a surface. The increase in depth and void volume of valleys improved the connectivity between valleys, but impeded the coalescence of contact clusters, resulting in the extinction of the spanning void cluster allowing fluid flow when the relative contact area was large. Furthermore, the critical pressure and connectivity at the percolation threshold were related to the maximum peak height and autocorrelation length of a surface, respectively.

Shear Stresses Below Asperities in Hertzian Contact as Measured by Photoelasticity

1973 ◽  
Vol 95 (3) ◽  
pp. 277-283 ◽  
Author(s):  
R. L. Leibensperger ◽  
T. M. Brittain
Keyword(s):  
Surface Roughness ◽  
Three Dimensional ◽  
Contact Fatigue ◽  
Hertzian Contact ◽  
Contact Theory ◽  
Shear Stresses ◽  
Asperity Contact ◽  
Surface Shear ◽  
Stress Theory ◽  
Effect Of Surface

The effect of surface roughness on shear stresses below the surface of an unlubricated Hertzian contact is analyzed using a three dimensional stress freezing photoelastic technique. The shear stresses in the micro-Hertzian contact in each asperity are shown to combine and form, at a greater depth below the surface, shear stresses generally associated with contact stress theory. These macro-Hertzian stresses are compared with the micro-Hertzian stresses in the asperities. The results are also correlated with an existing asperity contact theory and are discussed in relation to the contact fatigue phenomenon.

Performance of Spur Gears Considering Surface Roughness and Shear Thinning Lubricant

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
S. Akbarzadeh ◽  
M. M. Khonsari
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Shear Thinning ◽  
Asperity Contact ◽  
Spur Gears ◽  
Lubricant Film Thickness ◽  
Lubrication Regime ◽  
Effect Of Surface

A model is developed for predicting the performance of spur gears with provision for surface roughness. For each point along the line of action, the contact of pinion and gear is replaced by that of two cylinders. The radii of cylinders, transmitted load, and contact stress are calculated, and lubricant film thickness is obtained using the load-sharing concept of Johnson et al. (1972, “A Simple Theory of Asperity Contact in Elastohydrodynamic Lubrication,” Wear, 19, pp. 91–108) To validate the analysis, the predicted film thickness and the friction coefficient are compared to published theoretical and experimental data. The model is capable of predicting the performance of gears with non-Newtonian lubricants—such as that of shear thinning lubricants—often used in gears. For this purpose, a correction factor for shear thinning film thickness introduced by Bair (2005, “Shear Thinning Correction for Rolling/Sliding Electrohydrodynamic Film Thickness,” Proc. Inst. Mech. Eng., Part J: J. Eng. Tribol., 219, pp. 1–6) has been employed. The results of a series of simulations presenting the effect of surface roughness on the friction coefficient are presented and discussed. The results help to establish the lubrication regime along the line of action of spur gears.

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