scholarly journals Surface Roughness Effects on the Broadband Reflection for Refractory Metals and Polar Dielectrics

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3090 ◽  
Author(s):  
Lina Cao ◽  
Kursat Sendur
Keyword(s):  
Material Processing ◽  
Surface Roughness ◽  
Plasma Frequency ◽  
Refractory Metals ◽  
Roughness Effects ◽  
Random Surface ◽  
Spectral Reflectivity ◽  
Infrared Spectral ◽  
Gaussian Surface ◽  
Surface Distortions

Random surface roughness and surface distortions occur inevitably because of various material processing and fabrication techniques. Tailoring and smoothing the surface roughness can be especially challenging for thermomechanically stable materials, including refractory metals, such as tungsten (W), and polar dielectrics, such as silicon carbide (SiC). The spectral reflectivity and emissivity of surfaces are significantly impacted by surface roughness effects. In this paper, we numerically investigated the surface roughness effects on the spectral reflectivity and emissivity of thermomechanically stable materials. Based on our results, we determined that surface roughness effects are strongly impacted by the correlation length of the Gaussian surface. In addition, our results indicate that surface roughness effects are stronger for the materials at the epsilon-near-zero region. Surface roughness effects are stronger between the visible and infrared spectral region for W and around the wavelength of 12 μ m for SiC, where plasma frequency and polar resonance frequency are located.

Random Surface Roughness Effects in Microasperity Lubrication

2005 ◽  
Author(s):  
Prerit Vyas ◽  
Lyndon S. Stephens
Keyword(s):  
Surface Roughness ◽  
Classical Theory ◽  
Experimental Results ◽  
Roughness Effects ◽  
Random Surface ◽  
Pressure Buildup ◽  
Hydrodynamic Bearings ◽  
Parallel Surfaces ◽  
Lubrication Characteristics ◽  
Effect Of Surface

It is well known that the classical theory of lubrication does not predict the existence of a stable hydrodynamic film between two parallel surfaces. Experimental results have shown that the surface roughness (asperities and cavities) helps the pressure buildup between the two surfaces, thus maintaining the load support that keeps the surfaces from collapsing into each other. The effect of surface roughness on lubrication has gained considerable attention since it is widely recognized that surface roughness can alter the solution for pressure and leakage in hydrodynamic bearings from that given by classical theory. The present work investigates the effect of random (stochastic) surface roughness on the lubrication characteristics of a thrust ring engineered with deterministic surface features.

Surface roughness effects on the reinforcement of cement mortars through 3D printed metallic fibers

2016 ◽  
Vol 99 ◽  
pp. 305-311 ◽  
Author(s):  
Ilenia Farina ◽  
Francesco Fabbrocino ◽  
Francesco Colangelo ◽  
Luciano Feo ◽  
Fernando Fraternali
Keyword(s):  
Surface Roughness ◽  
Roughness Effects ◽  
Cement Mortars ◽  
3D Printed ◽  
Metallic Fibers

The effect of a footprint on perceived surface roughness

1986 ◽  
Vol 405 (1829) ◽  
pp. 303-327 ◽  
Keyword(s):  
Surface Roughness ◽  
Weighting Function ◽  
Sampling Interval ◽  
Asymptotic Convergence ◽  
Reference Surface ◽  
Two Dimensional ◽  
Random Surface ◽  
Spectral Density Functions ◽  
Continuous Theory ◽  
Discrete Theory

A two-dimensional homogeneous random surface { y ( X )} is generated from another such surface { z ( X )} by a process of smoothing represented by y ( X ) = ∫ ∞ d u w ( u – X ) z ( u ), where w ( X ) is a deterministic weighting function satisfying certain conditions. The two-dimensional autocorrelation and spectral density functions of the smoothed surface { y ( X )} are calculated in terms of the corresponding functions of the reference surface { z ( X )} and the properties of the ‘footprint’ of the contact w ( X ). When the surfaces are Gaussian, the statistical properties of their peaks and summits are given by the continuous theory of surface roughness. If only sampled values of the surface height are available, there is a corresponding discrete theory. Provided that the discrete sampling interval is small enough, profile statistics calculated by the discrete theory should approach asymptotically those calculated by the continuous theory, but it is known that such asymptotic convergence may not occur in practice. For a smoothed surface { y ( X )} which is generated from a reference surface { z ( X )} by a ‘good’ footprint of finite area, it is shown in this paper that the expected asymptotic convergence does occur always, even if the reference surface is ideally white. For a footprint to be a good footprint, w ( X ) must be continuous and smooth enough that it can be differentiated twice everywhere, including at its edges. Sample calculations for three footprints, two of which are good footprints, illustrate the theory.

Investigation of surface roughness effects on fluid flow in passive micromixer

2013 ◽  
Vol 20 (12) ◽  
pp. 2261-2269 ◽  
Author(s):  
Gaurav Pendharkar ◽  
Raghavendra Deshmukh ◽  
Rajendra Patrikar
Keyword(s):  
Surface Roughness ◽  
Fluid Flow ◽  
Roughness Effects ◽  
Passive Micromixer

Surface roughness effects on equilibrium temperature.

1969 ◽  
Vol 6 (8) ◽  
pp. 955-957 ◽  
Author(s):  
R. G. HERING ◽  
T. F. SMITH
Keyword(s):  
Surface Roughness ◽  
Equilibrium Temperature ◽  
Roughness Effects

Surface roughness effects in turbulent boundary layers

1999 ◽  
Vol 27 (5) ◽  
pp. 450-460 ◽  
Author(s):  
P.-Å. Krogstadt ◽  
R.A. Antonia
Keyword(s):  
Surface Roughness ◽  
Boundary Layers ◽  
Turbulent Boundary Layers ◽  
Roughness Effects
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