The Influence of Surface Roughness on Elastohydrodynamic Traction

1987 ◽  
Vol 201 (2) ◽  
pp. 145-150 ◽  
Author(s):  
C R Evans ◽  
K L Johnson
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Rheological Properties ◽  
Root Mean Square ◽  
Contact Pressure ◽  
Viscosity Index ◽  
Root Mean Square Roughness ◽  
Mean Square ◽  
Sliding Surfaces ◽  
The Mean

If the ratio λ of the nominal elastohydrodynamic film thickness h0 to the root-mean-square roughness is greater than about 5, the traction between two rolling and sliding surfaces is negligibly influenced by surface roughness. The traction is then primarily a function of the parameter α0[Formula: see text], as described in reference (4), where[Formula: see text] is the mean contact pressure and αo is the pressure–viscosity index of the lubricant. When λ lies in the range 0.5–6, it is shown that the effect of asperity interaction is for the traction to still be governed by the bulk rheological properties of the oil, but at a pressure corresponding to the mean contact pressure of the asperities.

scholarly journals Elucidation of contact state on various rough surfaces via highly robust colorimetric optical interferometry

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Tatsunori Tomota ◽  
Mamoru Tohyama ◽  
Kazuyuki Yagi
Keyword(s):  
Film Thickness ◽  
Root Mean Square ◽  
Contact Area ◽  
Thickness Distribution ◽  
Optical Interferometry ◽  
Root Mean Square Roughness ◽  
Mean Square ◽  
Test Pieces ◽  
Static Contact ◽  
Nominal Contact Area

AbstractIn this study, we developed and practiced colorimetric optical interferometry for the direct observation of contact states to clarify contact phenomena. We theoretically demonstrated that the effect of roughness diffuse reflection could be neglected using interferometric light intensity according to the relationship between the optical film thickness and hue. Then, we measured the static contact surfaces of spherical test pieces of different root mean square roughnesses. Results indicate that the nominal contact area is significantly larger than that obtained from the Hertzian theory of smooth contact as the surface roughness increases. The contact film thickness on the nominal contact area increases almost in proportion to the root mean square roughness. Our experiment supports the validity of the contact theory and contact simulation with very small roughnesses, which have been difficult to verify experimentally. The advantage of this measurement is that it can simultaneously capture the macroscopic contact area and microscopic film thickness distribution, which is expected to further expand the range of application.

scholarly journals Cylinder-Flat Contact Mechanics with Surface Roughness

2020 ◽  
Vol 69 (1) ◽  
Author(s):  
A. Tiwari ◽  
B. N. J. Persson
Keyword(s):  
Surface Roughness ◽  
Contact Pressure ◽  
Dimensionless Parameter ◽  
Elastic Half Space ◽  
Root Mean Square Roughness ◽  
Mean Square ◽  
Hertz Contact ◽  
Random Surface ◽  
Roughness Amplitude ◽  
Flat Contact

AbstractWe study the nominal (ensemble averaged) contact pressure p(x) acting on a cylinder squeezed in contact with an elastic half space with random surface roughness. The contact pressure is Hertzian-like for $$\alpha < 0.01$$ α < 0.01 and Gaussian-like for $$\alpha > 10$$ α > 10 , where the dimensionless parameter $$\alpha = h_{\rm rms}/\delta $$ α = h rms / δ is the ratio between the root-mean-square roughness amplitude and the penetration for the smooth surfaces case (Hertz contact).

The Generating Mechanism of Surface Roughness by Random Cutting Edges

1978 ◽  
Vol 20 (4) ◽  
pp. 197-200
Author(s):  
M. Hasegawa ◽  
T. Tsukizoe
Keyword(s):  
Surface Roughness ◽  
Root Mean Square ◽  
Statistical Approach ◽  
Ground Surface ◽  
Root Mean Square Roughness ◽  
Mean Square ◽  
Two Dimensional ◽  
Dimensional Distribution

This paper describes a statistical approach for predicting the generating mechanism of the surface roughness produced by random cutting edges. The two-dimensional distribution of the generated surface roughness is derived by considering the distribution of the maxima of the cutting edges. The method is used to determine the root-mean-square roughness of the ground surface.

scholarly journals THE PREDICTION AND OPTIMIZATION OF SURFACE ROUGHNESS IN GRINDING OF S50C CARBON STEEL USING MINIMUM QUANTITY LUBRICATION OF VIETNAMESE PEANUT OIL

2021 ◽  
pp. 1-8
Author(s):  
Van Canh Nguyen ◽  
Tien Dung Hoang ◽  
Thuy Nguyen ◽  
Ngoc Hoanh Dao ◽  
Hien Do Minh ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Carbon Steel ◽  
Root Mean Square ◽  
Flow Rate ◽  
Feed Rate ◽  
Cutting Parameters ◽  
Peanut Oil ◽  
Root Mean Square Roughness ◽  
Depth Of Cut ◽  
Mean Square

This experimental research aimed to build the regression model of grinding S50C carbon steel based on a Regression Optimizer. The workpiece specimens were JIS S50C carbon steel that was hardened at 52HRC. Taguchi L27 orthogonal array was performed with 5 3-levels-factors. The studied factors were combining cutting parameters, such as cutting speed, feed rate, depth of cut, and lubricant parameters, including air coolant flow rate Q and air pressure P. The results show that cutting parameters includes workpiece velocity Vw, feed rate f, and depth of cut t, influence the most on surface roughness Ra, Root Mean Square Roughness Rq, and Mean Roughness Depth Rz,. By contrast, the influence of lubrication parameters is fuzzy. Therefore, this present work focused on predicting and optimizing Ra, Rz, Rq in surface grinding of JSI S50C carbon steel using MQL of peanut oil. In this work, combining of grinding parameters and lubrication parameters were considered as input factors. The regression models of Ra, Rz, and Rq were obtained using Minitab 19 by Regression Optimizer tool, and then the multi-object optimization problem was solved. The present findings have shown that Vietnamese vegetable peanut oil could be considered as the lubricant in the grinding process. The optimum grinding and lubricant parameters as following: the workpiece velocity Vw of 5 m/min, feed rate f of 3mm/stroke, depth of cut of 0.005mm and oil flow rate, air pressure of 91.94 ml/h, 1 MPa, respectively. Corresponding to the surface roughness Ra, Root Mean Square Roughness Rq, and Mean Roughness Depth Rz of 0.6512mm, 4.592mm, 0.8570mm, respectively.  

Growth Behavior of Au Films on SiO2Film and Direct Transfer for Smoothing Au Surfaces

2019 ◽  
Vol 13 (2) ◽  
pp. 254-260 ◽  
Author(s):  
Michitaka Yamamoto ◽  
Takashi Matsumae ◽  
Yuichi Kurashima ◽  
Hideki Takagi ◽  
Tadatomo Suga ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Low Temperature ◽  
Film Thickness ◽  
Root Mean Square ◽  
Room Temperature ◽  
Growth Behavior ◽  
Direct Transfer ◽  
Mean Square ◽  
Low Temperature Bonding ◽  
Deposited Films

Direct transfer of Au films deposited on smooth SiO2film with RMS (root mean square) surface roughness of 0.24 nm was investigated with the aim of generating smooth Au surfaces. Deposited Au films with different thicknesses were transferred to rough Au surfaces on target substrates at room temperature with a contact pressure of 50 MPa. Observation of the growth behavior of the deposited films revealed that they formed a continuous structure when their nominal film thickness was around 15 nm or above. The transfer of continuous Au films with a thickness of 20, 51, or 102 nm reduced the RMS roughness of the rough Au surfaces from 1.6 nm to 0.4 nm. In contrast, the transfer of Au films with a thickness less than 5 nm increased their surface roughness. This direct transfer technique should thus be useful for low temperature bonding.

Experimental Analysis of Non-Uniform Surface Roughness Affecting to Flow Resistance

2010 ◽  
Author(s):  
A. Matsumoto ◽  
T. Ito ◽  
M. Motozawa ◽  
H. Kawashima ◽  
H. Ando ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Reynolds Number ◽  
Friction Coefficient ◽  
Density Distribution ◽  
Probability Density ◽  
Root Mean Square ◽  
Flow Resistance ◽  
Root Mean Square Roughness ◽  
Probability Density Distribution ◽  
Mean Square

Experimental investigation on non-uniform surface roughness affecting to flow resistance has been carried out. Experiment was performed with the concentric cylinder device. In this experiment, we evaluated non-uniform surface roughness of various surface by the optical method and measured friction coefficient in turbulent flow over each surface roughness. As an evaluation of non-uniform surface roughness, we measured surface roughness profiles of each surface by a laser displacement sensor. Based on this surface roughness profiles, we calculated some roughness parameters such as the root mean square roughness. One important result indicates the relationship between friction coefficient and roughness Reynolds number. The friction coefficient increases logarithmically with increasing roughness Reynolds number. Moreover, to discuss the effect of non-uniform roughness in detail, the Probability Density Function (PDF) of the roughness height and the spectrum of the surface roughness profiles were analyzed. As a result, the frictional drag over the rough surface can be mostly evaluated by the roughness Reynolds number which is defined by the root mean square roughness when the probability density distribution of the surface roughness profile has Gaussian distribution. However, if the probability density distribution does not have Gaussian distribution, kurtosis and skewness of surface roughness profile are also important parameter for the evaluation of the surface roughness.

Autocovariance functions, root-mean-square-roughness height, and autocovariance length for rough deposits of copper, silver, and gold

1982 ◽  
Vol 25 (4) ◽  
pp. 2315-2323 ◽  
Author(s):  
G. Rasigni ◽  
F. Varnier ◽  
M. Rasigni ◽  
J. P. Palmari ◽  
A. Llebaria
Keyword(s):  
Root Mean Square ◽  
Roughness Height ◽  
Root Mean Square Roughness ◽  
Mean Square

The Quantification of Microwear on Chipped Stone Tools: Assessing the Effectiveness of Root Mean Square Roughness (Rq)

2008 ◽  
Vol 33 (2) ◽  
pp. 173-189 ◽  
Author(s):  
W. James Stemp ◽  
Ben E. Childs ◽  
Samuel Vionnet ◽  
Christopher A. Brown
Keyword(s):  
Root Mean Square ◽  
Stone Tools ◽  
Root Mean Square Roughness ◽  
Mean Square ◽  
Chipped Stone

Direct numerical simulation of turbulence over systematically varied irregular rough surfaces

2019 ◽  
Vol 862 ◽  
pp. 781-815 ◽  
Author(s):  
Y. Kuwata ◽  
Y. Kawaguchi
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Root Mean Square ◽  
Drag Force ◽  
Rough Surfaces ◽  
Skin Friction Coefficient ◽  
Root Mean Square Roughness ◽  
Mean Square ◽  
Mean Velocity ◽  
Navier Stokes Equation

Lattice Boltzmann direct numerical simulation of turbulent open-channel flows over randomly distributed hemispheres at $Re_{\unicode[STIX]{x1D70F}}=600$ is carried out to reveal the influence of roughness parameters related to a probability density function of rough-surface elevation on turbulence by analysing the spatial and Reynolds- (double-) averaged Navier–Stokes equation. This study specifically concentrates on the influence of the root-mean-square roughness and the skewness, and profiles of turbulence statistics are compared by introducing an effective wall-normal distance defined as a wall-normal integrated plane porosity. The effective distance can completely collapse the total shear stress outside the roughness sublayer, and thus the similarity of the streamwise mean velocity is clearer by introducing the effective distance. In order to examine the influence of the root-mean-square roughness and the skewness on dynamical effects that contribute to an increase in the skin friction coefficient, the triple-integrated double-averaged Navier–Stokes equation is analysed. The main contributors to the skin friction coefficient are found to be turbulence and drag force. The turbulence contribution increases with the root-mean-square roughness and/or the skewness. The drag force contribution, on the other hand, increases in particular with the root-mean-square roughness whereas an increase in the skewness does not increase the drag force contribution because it does not necessarily increase the surface area of the roughness elements. The contribution of the mean velocity dispersion induced by spatial inhomogeneity of the rough surfaces substantially increases with the root-mean-square roughness. A linear correlation is confirmed between the root-mean-square roughness and the equivalent roughness while the equivalent roughness monotonically increases with the skewness. A new correlation function based on the root-mean-square roughness and the skewness is developed with the available experimental and direct numerical simulation data, and it is confirmed that the developed correlation reasonably predicts the equivalent roughness of various types of real rough surfaces.

scholarly journals Manufacture of Highly Transparent and Hazy Cellulose Nanofibril Films via Coating TEMPO-Oxidized Wood Fibers

Nanomaterials ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 107 ◽  
Author(s):  
Weisheng Yang ◽  
Liang Jiao ◽  
Wei Liu ◽  
Hongqi Dai
Keyword(s):  
Root Mean Square ◽  
Low Cost ◽  
Inorganic Nanoparticles ◽  
Root Mean Square Roughness ◽  
Mean Square ◽  
Cellulose Nanofibril ◽  
Wood Fibers ◽  
Excellent Thermal Stability ◽  
Blending Method ◽  
Coating Method

Traditionally, inorganic nanoparticles (SiO2, TiO2) have been utilized to tune the optical haze of optoelectronic devices. However, restricted to complex and costly processes for incorporating these nanoparticles, a simple and low-cost approach becomes particularly important. In this work, a simple, effective, and low-cost method was proposed to improve optical haze of transparent cellulose nanofibril films by directly depositing micro-sized 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized wood fibers (“coating” method). The obtained films had a high total transmittance of 85% and a high haze of 62%. The film samples also showed a high tensile strength of 80 MPa and excellent thermal stability. Dual sides of the obtained films had different microstructures: one side was extremely smooth (root-mean-square roughness of 6.25 nm), and the other was extremely rough (root-mean-square roughness of 918 nm). As a reference, micro-sized TEMPO-oxidized wood fibers and cellulose nanofibrils were mixed to form a transparent and hazy film (“blending” method). These results show that hazy transparent films prepared using the “coating” method exhibit superior application performances than films prepared using the “blending” method.

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