Dissertations / Theses on the topic 'Surface roughness'
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1
Mamo, Andrew Benedict 1982. "Surface roughness of Mars." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/32744.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2004.Includes bibliographical references (p. 35-36).
In this thesis, I created an algorithm to compensate for the saturation of data collected by the Mars Orbiter Laser Altimeter (MOLA). Saturation of the energy measurements had made it impossible to measure surface roughness at 100 m length scales. By calculating the returned energy, the problem of saturation can be avoided. This algorithm was applied to MOLA data across the Martian surface to create an estimate of surface roughness across the planet. The method calculates pulse spreading from returned pulse energy using the link equation. The accuracy of the method is limited by the accuracy of albedo measurements. This analysis improved the estimation of surface roughness on Mars. Further improvements could be gained by correcting for the opacity of atmospheric dust as a cause of pulse spreading.
by Andrew Benedict Mamo.
S.B.
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Beyer, Ross A. "Martian surface roughness and stratigraphy." Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/290105.
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Orbital datasets can be combined and manipulated to learn about the three-dimensional structure of planetary surfaces, and the processes that have acted on them. The Mars Orbital Camera (MOC) is providing high-resolution images. These images allow qualitative inspection of features, and contain quantitative information about the shape of the surface. Using a photoclinometry technique derived from a lunar-Lambert photometric function, I am able to obtain estimates of the down-sun slope of each pixel in an image. This technique was calibrated against synthetic topography, compared to an area photoclinometry technique, and applied to the Viking and Pathfinder landing sites. It is a robust technique for obtaining the roughness and slope characteristics of large areas. It was applied to the potential landing sites for the Mars Exploration Rovers to evaluate site safety. The slopes from this point photoclinometry technique can be used to obtain a rough estimate of topography, which I used in a number of studies where topographic information was crucial. MOC images have shown that layering is pervasive on the martian surface. Mars Orbital Laser Altimeter (MOLA) data can be registered to MOC images to provide elevation constraints on layer outcrops. Such layers are observed in eastern Coprates Chasma both in the chasma rim and in a flat-topped massif. Observations indicate that the chasma stratigraphy consists of thin sequences of resistant layers and intervening thicker sequences of relatively less resistant layers. More resistant units cap the massif against erosion and result in steeper slopes than the weaker units would otherwise allow. These resistant layers can be used as stratigraphic markers which have allowed me to measure the subsidence and tilting of the massif relative to the chasma walls, providing evidence for tectonic motion in this portion of the Valles Marineris. These outcrops indicate that some of these layers may be analogus to terristrial flood basalts in both composition and extent. I have constrained the dip angle of finely layered sequences in Ganges and Hebes Mensae. These layers are either flat lying or dip shallowly, but do not dip steeply, which places some constraints on the origin of these mensae.
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Fujiwara, Yuko. "Evaluation of wood surface roughness as related to tactile roughness." Kyoto University, 2004. http://hdl.handle.net/2433/145425.
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Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第11112号
農博第1442号
新制||農||898(附属図書館)
学位論文||H16||N3962(農学部図書室)
22662
UT51-2004-L909
京都大学大学院農学研究科森林科学専攻
(主査)教授 奥村 正悟, 教授 増田 稔, 教授 池田 善郎
学位規則第4条第1項該当
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Cinat, Paolo. "Surface roughness genomics in contact mechanics : a new method enabling roughness design towards surface prototyping." Thesis, IMT Alti Studi Lucca, 2018. http://e-theses.imtlucca.it/252/1/Cinat_phdthesis.pdf.
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In actual age of Industry 4.0, the miniaturization of mechanical
components is becoming extremely sophisticated, thanks
to enhancing techniques such as additive manufacturing technologies.
This requires an efficient description of multi-scale
roughness to properly characterize the interface contact problem.
In this dissertation, a new approach called surface roughness
genomics is proposed to uniquely characterize surfaces
at different length scales, from the topological point of view.
Similar to biological systems, where the biological information
is encoded in DNA base pairs, surface roughness is decomposed
in elementary waves, whose unique ensemble is
the surface genome. The identification process of the real surfaces
genome, the sequencing procedure, is based on the solution
of a constrained convex optimization problem. A rough
profile (chromosome), collecting the features of roughness at
a fixed length-scale is isolated from the surface genome So,
a rough profile is reconstructed by summing up subsequent
chromosomes. The top-down and bottom-up approaches are
pursued to reconstruct a rough profile, to quantify the role
of specific multi-scale features in the frictional normal contact
problem. New algorithms are then proposed to generate
roughness morphology achieving a target mechanical response,
enabling surface prototyping towards morphology
real time control.Beside the mechanical contact problem, the
fluid sealing between contacting bodiesis herein investigated
by proposing a simple algorithm and applying it to a set of
fractal rough surfaces. This algorithm evaluates the free networks
involved in leakage process, considering different normal
contact indentations at various surface resolutions.
5
Liu, Yu. "Surface roughness generated boundary layer noise." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612403.
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Vandadi, Aref. "Optimization of Superhydrophobic Surfaces to Maintain Continuous Dropwise Condensation." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc500016/.
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In the past decade, the condensation on superhydrophobic surfaces has been investigated abundantly to achieve dropwise condensation. There is not a specific approach in choosing the size of the roughness of the superhydrophobic surfaces and it was mostly selected arbitrarily to investigate the behavior of condensates on these surfaces. In this research, we are optimizing the size of the roughness of the superhydrophobic surface in order to achieve dropwise condensation. By minimizing the resistances toward the transition of the tails of droplets from the cavities of the roughness to the top of the roughness, the size of the roughness is optimized. It is shown that by decreasing the size of the roughness of the superhydrophobic surface, the resistances toward the transition of the tails of droplets from Wenzel state to Cassie state decrease and consequently dropwise condensation becomes more likely.
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Ward, R. L. "Roughness measurements of machined workpieces." Thesis, Leeds Beckett University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314787.
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Isleyici, Umut. "Effect Of Surface Roughness On Ultrasonic Testing." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606937/index.pdf.
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This study investigates the effect of front surface roughness on ultrasonic echo amplitude. Experiments were carried out on specimens whose front surfaces are machined by milling machine. Machining parameters were changed in milling
process in order to obtain desired roughness values and milling head was tilted to a very small angle to obtain periodic rough surfaces. Experiments were performed with these specimens having roughness value of 0.5, 4.5, 11, 26.5 µm. Ra. The back surface roughness of all specimens was kept constant at 1.5 µ
m Ra by grinding operation. 1.5, 2, 3, 4 mm. holes were drilled at constant depth and to same side of each specimen to represent reference discontinuities. Ultrasonic tests, using pulse echo technique were carried out to monitor echo amplitudes corresponding to different roughness values. The tests were also repeated by using different ultrasonic probes having different frequencies. For additional comparison, different couplants were used through the tests. The results showed that there was a significant increase in the reduction of the sound pressure level with the increase in the surface roughness. Although there was no uncertainty observed about not being able to detect discontinuity because of roughness but correct couplant and frequency selection has a positive effect on correctly sizing the discontinuity and at attenuation measurements. The results obtained with this work can be used as a guide for testing rough surfaces, predicting the effect on ultrasonic examination before testing and discontinuity detecting capability under rough surface conditions.
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Wu, Jiunn-Jong. "Surface roughness and its role in contact." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363100.
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Zhang, Cheng. "Influence of surface roughness on thermography measurement." Thesis, Högskolan Väst, Avd för automationssystem, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-6842.
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This university Bachelor's Thesis was performed to explore the influence of surface roughness on the thermography measurement. Thermography is a non-destructive testing method which can be used to detect cracks. However, it is hard to define how the surface roughness influences the emissivity and the result of a thermography measurement, as well as how the angle of the excitation source influences the result. Therefore, this work aims to define how the heating angle and surface roughness influence the thermography measurement, define the relationship between surface roughness and emissivity for the same crack, and define the influence of the angles which composed of the heating source, the direction of crack and the direction of surface roughness on thermography measurement. In this report, the theories of radiation and Signal-to-noise ratio (SNR) were explained, clearly. Also, two kinds of experiments were set up. One is focus on how the heating angle influence the thermography measurement, the other is focus on how the angle of the heating source, in relation to the crack direction and the direction of surface roughness, influence the SNR value. The conclusions of these experiments are that the heating of a crack increases as the angle decreases (from wide side to narrow side) and the angle ofincreases (from horizontal to vertical). Moreover, the SNR value decreases as the surface roughness increases. For the same surface roughness, the SNR value increases with increased crack angle (0°, 45° or 90°) and with decreased sample position angle (horizontal, 45°or vertical). What is more, the higher surface roughness, the larger the influence of the crack angle and the sample position angle. Finally, when the surface is polish, the crack angle and the sample position angle does not have any influence.
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Kulkarni, Amit S. "Effects of surface roughness in microchannel flows." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0003400.
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Sharma, Priyanka. "Investigations of Titan's Topography and Surface Roughness." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/241978.
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Saturn's moon, Titan is a geomorphologically active planetary object, and its surface is influenced by multiple processes like impact cratering, fluvial and aeolian erosion, lacustrine processes, tectonics, cryovolcanism and mantling. Disentangling the processes that compete to shape Titan's landscape is difficult in the absence of global topography data. In this thesis, I utilize techniques in topographic statistics, fractal theory, study of terrestrial analogs and landscape evolution modeling to characterize Titan's topography and surface roughness and investigate the relative roles of surface processes in sculpting its landscape. I mapped the shorelines of 290 North Polar Titanian lakes using the Cassini Synthetic Aperture Radar dataset. The fractal dimensions of the shorelines were calculated via the divider/ruler method and box-counting method, at length scales of (1-10) km and found to average 1.27 and 1.32, respectively. The inferred power-spectral exponent of Titan's topography (β) was found to be ≤ 2, which is lower than the values obtained from the global topography of the Earth or Venus. In order to interpret fractal dimensions of Titan's shorelines in terms of the surficial processes at work, I repeated a similar statistical analysis with 114 terrestrial analogous lakes formed by different processes, using C-band radar backscatter data from the Shuttle Radar Topography Mission (SRTM). I found different lake generation mechanisms on Earth produce 'statistically different' shorelines; however, no specific set of processes could be identified for forming Titanian lake basins. Using the Cassini RADAR altimetry data, I investigated Titan's global surface roughness and calculated median absolute slopes, average relief and Hurst exponent (H) for the surface of Titan. I detected a clear trend with latitude in these roughness parameters. Equatorial regions had the smallest slopes, lowest values of H and smallest intra-footprint relief, compared to the mid-latitudes and polar regions of Titan. I used steady state models of relief generation (tectonic activity) and relief reduction (diffusive mass wasting and advective bedrock channel erosion) to generate synthetic landscapes and simulate Titan's topography. I provided constraints on two environmental variables for Titan that influence surface roughness: diffusivity and erodibility coefficient.
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Wallace, Karen Sue 1957. "SURFACE ROUGHNESS EFFECTS ON SOIL SPECTRAL REFLECTANCE." Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/275522.
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Shaw, Joseph Alan 1962. "Laser-glint measurements of sea-surface roughness." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/290653.
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Optical glint patterns convey information about the roughness of the surface on which they are formed. This dissertation describes two new optical instruments that relate the variations of specular laser reflections (laser glints) from the sea surface in angular, temporal, and wavenumber space to the surface roughness. Measurements from these instruments are interpreted with the objective of improving the capabilities of remote-sensing instruments that view the ocean surface. Particular attention is paid to cm waves, which are resonant structures for microwave sensors and the most significant component of optical roughness. The scanning-laser glint meter counts laser glints in 1° angular bins over a ± 75° nadir-angle range. The video laser-glint imager is a CCD video camera that images glints from an array of diode lasers. Both instruments were deployed on the research platform FLIP in the Pacific Ocean near the Oregon coast for three weeks during September 1995. Normalized histograms of angular glint counts are interpreted as the probability density function (PDF) of sea-surface slope, a Gram-Charlier expansion of which facilitates studying the variation with wind speed and atmospheric stability of moments through order four. The PDF appears approximately Gaussian, but is skewed toward downwind slopes in the along-wind axis due to asymmetric wind waves. No skewness exists in the cross-wind axis. Slope PDFs also have positive peakedness, increasing the probability of very small and large slopes relative to a Gaussian. Surface roughness is shown to depend strongly on atmospheric stability, which is proportional to the air-water temperature difference. Both the mean-square slope and the peakedness increase with negative stability (water warmer than air) relative to the neutral-stability case (water and air temperatures equal). Increased surface roughness, due to increases in wind speed or negative stability, causes glint-count fractal dimensions to increase, glint-image power spectra to flatten, and glint-image autocorrelations to appear more wrinkled. Glint-image spectra are dominated by glint-size effects, which are related to surface curvature. New ways of modeling the interaction of electromagnetic waves with the ocean surface are suggested by the new fractal and spectral characterizations of surface roughness that are introduced here.
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Ștefan, Gheorghiu. "Standard and nonstandard roughness - consequences for the physics of self-affine surfaces /." free to MU campus, to others for purchase, 2000. http://wwwlib.umi.com/cr/mo/fullcit?p9988664.
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Ergin, Fahrettin Gökhan. "Roughness Induced Transition." Case Western Reserve University School of Graduate Studies / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=case1121435967.
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Manu, Dabankah Emmanuel. "Surface Roughness Characterization of hole walls in fibercomposites." Thesis, KTH, Industriell produktion, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-140314.
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In the manufacturing of fibrecomposite structures for the aircraft industry many holes are drilled through the composite for the attachment of the composite to a metal frame. These holes have a Ra specification of the cylindrical walls. The measurement of this roughness is tedious work if made by a stylus profiler. In this thesis, a design concept is created and tested by using OSLO raytracing program. This employed raytracing simulation is used to analyze and study variation of the surface features of the hole and evaluate the corresponding resultant image afterwards using image quality indicators. On large scale the aim of the thesis work is to investigate the possibilities of detecting defects of the cylindrical walls and get a quantitative measurement of the roughness of the hole by employing the concept of optical cylindrical imaging. Keywords: Surface roughness, Light scattering, Diffraction , Reflection, Raytracing analysis, Wavefront analysis, Spot diagram, Diffraction limit, PSF, MTF, Energy analysis, Optimization, Entrance pupil, Exit pupil, Carbon Fiber Reinforced Polymers (CFRP), Axicon, He Ne Laser.
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Cullen, Lachlan Michael. "Acoustic receptivity in boundary layers with surface roughness." Thesis, Queen Mary, University of London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327024.
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Gadsby, Philip. "Surface roughness effects on thermally stressed aviation fuel." Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/19191/.
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Thermal instability in aviation fuels has been thoroughly explored over the last 50 years. The problem is complex, with coupling of fuel chemistry, heat transfer and fluid dynamics. Most efforts have been applied to the chemical kinetics of deposit formation and studying physical effects such as temperature, flow rate and Reynolds number in a multitude of small to large scale testing devices. However, much less attention has been paid to the effects of wall surface roughness. This is surprising - since for turbulent flow, wall roughness enhances momentum, heat and mass transfer by disrupting the quiescent viscous layer adjacent to the wall and interfering with structures of turbulence further into the boundary layer. Furthermore, a rough surface increases the wall surface area, presenting more active sites for heterogeneous catalytic reactions. Additive Layer Manufacturing (ALM) has been touted as ’game changing’ technology and is now being proposed as a method to create components for gas turbine engines. The technology results in near net shape parts with reduced weight, number of welds and material waste compared to conventional subtractive machining methods. However, the surface roughness of ALM components can be orders of magnitude greater than machined components and can be highly non-uniform. While reducing external surface roughness is trivial, typical methods of internal roughness reduction (ie. abrasive flow machining) may not be possible for small scale passages. This may result in internal fuel passageways with high relative roughness in components which are subject to high thermal loading - for example, injector feed arms which are exposed to compressor discharge air. The effect of wall roughness on deposition of thermally stressed aviation fuel was investigated in both laminar and turbulent flow regimes using small to medium scale test devices. Deposition over ALM components was tested in the laminar regime with a modified Jet Fuel Thermal Oxidation Tester (JFTOT) and in the turbulent regime with the Aviation Fuel Thermal Stability Test Unit (AFTSTU). The High Reynolds Number Thermal Stability Tester (HiReTS) was used to examine deposition in micro-scale tubes with very high relative roughness. As well as microscopy and 3D optical profilometry, momentum and heat transfer experiments were conducted to characterise the roughness as fully as possible. In the laminar regime, the effect of roughness was negligible. For turbulent flow, substantial differences in heat transfer and deposition rate were consistently observed for tubes with the highest relative roughness. The increase in deposition rate is thought to be related to the projection of roughness elements into regions of intense turbulent activity in the boundary layer. The turbulence structures, which are more energetic and have reduced anisotropy over rough walls, increase wall-normal transport - thereby replenishing the near wall region with deposit precursor and providing insoluble particles formed off the wall with inertia with which to deposit.
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Munoz-Escalona, Patricia. "Surface roughness prediction when milling with square inserts." Thesis, University of Bath, 2010. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.519033.
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Rellick, Lorraine Mary. "Local packing densities and surface roughness of proteins /." The Ohio State University, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487759055158724.
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Almqvist, Andreas. "On the effects of surface roughness in lubrication." Doctoral thesis, Luleå tekniska universitet, Maskinelement, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-18259.
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Tribology is a multidisciplinary field defined as the science and technology of interacting surfaces in relative motion, and embraces the study of friction, wear and lubrication. A typical tribological application is the rolling element bearing. Tribological contacts may also be found in other types of bearings, cam-mechanisms, gearboxes and hydraulic systems. Examples of bearings inside the human body are the operation of the human hip joint and the contact between teeth during chewing. To fully understand the operation of this type of application one has to understand the couplings between the lubricant fluid dynamics, the structural dynamics of the bearing material, the thermodynamical aspects and the resulting chemical reactions. This makes modeling tribological applications an extremely delicate task. Because of the multidisciplinary nature, such theoretical models lead to mathematical descriptions generally in the form of non-linear integro-differential systems of equations. Some of these systems of equations are sufficiently well posed to allow numerical solutions to be carried out, resulting in accurate predictions on performance. In this work, the influence on performance of a surface microscopical nature, the surface roughness, in contact interfaces between different types of machine element components is the subject of study. An example is the non-conformal lubricated contact between one of the rollers and the inner ring in a rolling element bearing. The tribological contact controlling the operation of the human hip joint is also very similar to this. Another example of a non-conformal contact occurs when driving on rainy roads, where the hydrodynamic action of the water separates the tire. To enable investigations of these types of problems, different theoretical models were studied; for the selected model, a numerical solution technique was developed within this project. This model is based on the Reynolds equation coupled with the film thickness equation. The numerical solution technique involves a multilevel technique to facilitate the solution process. Results presented in this thesis, utilizing this approach, study elementary surface features such as ridges and indentations passing each other inside the lubricated conjunction. The Reynolds equation is derived under the assumptions of thin fluid film and creeping flow, and considers in its most general form shear thinning of the lubricant. This type of equation describes the hydrodynamic action of the lubricant flow and may be used when the interfaces consist of either conformal or non-conformal conjunctions. Examples of applications having conformal interfaces are thrust- and journal- bearings or the contact between the eye and a (optical) contact lens. In such types of applications the load carried by the interface is distributed over a fairly large area that under certain circumstances helps to prevent mechanical deformation of the contacting surfaces. Such applications are said to operate in the hydrodynamic lubrication (HL) regime. Lubricant compressibility and cavitation are important aspects and have received some attention. However, the main objective when modeling HL has been to investigate and develop methods that enable the influence of surface roughness to be to be studied efficiently. Homogenization is a rigorous mathematical concept that when applied to a certain problem may be regarded as an averaging technique as well as it provides information about the induced effects of local surface roughness. Homogenization inflicts no restrictions on the surface roughness representation other than the representative part of the chosen surface roughness being assumed periodically distributed and of course the assumptions of thin film flow made through the Reynolds equation. The homogenization process leads to a two sets of equations one for the local scale describing surface roughness, scale and one for the global scale describing application geometry. The unequivocally determined coefficients of the global problem, which may be regarded as flow factors, are obtained through the solution of local problems. This makes homogenization an eminent approach to be used investigating the influence of surface roughness on hydrodynamic performance. In the present work, homogenization has been used to derive computationally feasible forms of problems originating from incompressible and compressible Reynolds type equations that describe stationary and unstationary flows in both cartezian and cylindrical co-ordinates. This technique enables simulations of surface roughness induced effects when considering surface roughness descriptions originating from measurements. Moreover, the application of homogenization facilitates the interpretation of results. Numerical investigations following the homogenization process have been carried out to verify the applicability of homogenization in hydrodynamic lubrication. Homogenization has also been shown here to enable efficient analysis of rough hydrodynamically lubricated problems. Also of note, in connection to the scientific contribution within tribology, collaboration with a group in applied mathematics has lead to the development of novel techniques in that area. These ideas have also been successfully applied, with some results presented in this thesis. At start-ups, the contact in a rolling element bearing could be both starved and drained from lubricant. In this case the hydrodynamic action becomes negligible in terms of load carrying capacity. The load is carried exclusively by surface asperities, the tribo film, or both. This is hereby modeled as the unlubricated frictionless contact between rough surfaces, i.e. a contact mechanical approach. A variational principle was used in which the real area of contact and the contact pressure distribution minimize the total complementary potential energy. The material model is linear elastic-perfectly plastic and the energy dissipation due to plastic deformation is accounted for. The numerics of this contact mechanical approach involve the fast Fourier transformation (FFT) technique in order to facilitate the solution process. Investigation results of the contact mechanics of realistic surfaces are presented in this thesis. In this investigation the variation in the real area of contact, the plasticity index and some surface roughness parameters due to applied load were studied.Godkänd; 2006; 20061116 (pafi)
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Zhang, Yilei. "The effect of surface roughness parameters on contact and wettability of solid surfaces." [Ames, Iowa : Iowa State University], 2007.
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Li, Hongchun. "A study on wear and surface roughness of work roll in cold rolling." School of Mechanical, Materials and Mechatronic Engineering - Faculty of Engineering, 2008. http://ro.uow.edu.au/theses/125.
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The objective of this study is to improve our understanding of the evolution and tribological behaviour of work roll surfaces in cold rolling because surface deterioration affects the quality of products and the efficiency of production. The cost of rolls is almost 25% of the cost of cold steel production. An experimental Lateral Set-testing (LST) mini-mill was developed to make use of the Gleeble 3500 thermo-mechanical simulator functions to evaluate, for the first time, the roll material surface features, surface roughness, fast Fourier transform (FFT) and Power Spectral Density (PSD) of frequency distribution, after single and multi-pass rolling. A low carbon-steel was prepared for the paired disc and then experiments on disc-to-disc wear were carried out to test surface deterioration and friction. In the laboratory, material imitating an industrial roll was manufactured. One batch contained 4%Cr and another contained 4%Cr plus approximately 0.1% Ti. These materials were compared against each other in the LST and disc-to-disc experiments. Experiments considered a series of parameters, including strip reduction, speed, and lubrication, while the disc-to-disc experiments considered duration of wear, forward and backward slip and load amplitude. The surfaces of the LST roller and disc were evaluated by surface technologies such as Atomic Force Microscope (AFM), Scanning Electron Microscope (SEM), and surface profile-meters. Transmission Electron Microscope (TEM) and X-ray diffraction wear properties. Test results from the mini-mill reveal that dominant waviness of the surface roughness still exists on the surface after a single pass of rolling and a 30.5% reduction is a critical reduction level that has a significant influence on the density of power spectrum. A rougher work piece results in a larger power spectrum of the surface profile. It has found that the PSD altitude of the roller surface is significantly affected axially but is more sensitive to its original surface roughness circumferentially. It is distributed in an inverse order to the surface roughness in a high frequency domain. The addition of Ti alters surface deterioration. Lubrication has a significant effect on surfaces containing either 4Cr% or 4%Cr+Ti, affecting surface roughness of rollers containing 4%Cr more significantly. In the disc-to-disc tests, more material was removed in the first 60 minutes from the disc containing Ti than the disc containing only 4%Cr. In general, roll material with 4%Cr+Ti reveals to have better anti-abrasive properties than the roll with only 4%Cr, while lubrication significantly reduced the wear rate and amount of material removed from both materials. The speed of the disc influences the weight loss, ie, the higher the speed the greater the amount of material removed. The slip rate also affects roll wear and weight loss because as the speed increases, so do the slip and loss of weight. The coefficients of friction are between 0.35~0.75 when the contact was dry and 0.06~0.11 when lubrication was applied. Adhesive friction dominated the dry contact while a mixed lubrication regime features friction behaviour when emulsion lubrication was applied. A backward slip of 2% and a forward slip of 1.5% resulted in a different coefficient of friction in dry contact mode although the corresponding torques were similar. The torque and coefficient of friction are found to increase with disc speed in dry contact condition. Lubrication alters the friction of both materials. The coefficient of friction decreases with speed on the disc with added Ti but the effect of load is in the opposite trend, while the disc with 4%Cr was less influenced by speed. The coefficient of friction is more sensitive to load at higher speeds on the disc with 4%Cr than at slower speeds on the disc with Ti added. This indicates that the addition of Ti enhances the tribological behaviour of rollers because the disc with Ti additive is characterised by carbonitrades precipitated in a refined tempered martensitic matrix. Coarse carbides characterise the 4%Cr disc materials. Surface defects of the work rolls, including banding, spalling, marking and welding in a cold strip plant, were investigated. It was found that early failures principally resulted from operational factors and roll material off-specification micro-structure defects rather than wear. It is recommended that different grades materials of the roll and strip with different roughness and hardness to be tested and studied on the evolution and tribological behaviour of roll surfaces in the future.
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Al-Maaitah, Ayman Adnan. "Effect of roughness element on the stability of boundary layers." Thesis, Virginia Tech, 1986. http://hdl.handle.net/10919/45741.
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The instability of flows around hump and dip imperfections is investigated. The mean flow is calculated using interacting boundary layers, thereby accounting for viscous/inviscid interaction and separation bubbles. Then, the two-dimensional linear instability of this flow is analyzed, and the amplification factors are computed. Results are obtained for several height/width ratios and locations. The theoretical results have been used to correlate the experimental results of Greening and Walker. The observed transition locations are found to correspond to amplification factors varying between 7.4 and 10, consistent with previous results for flat plates. The method accounts for Tollmien-Schlichting waves, the shear layer instability, and their interaction. Separation is found to increase significantly the amplification factor.Master of Science
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Turgay, Metin Bilgehan. "Effect Of Surface Roughness In Microchannels On Heat Transfer." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12610253/index.pdf.
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In this study, effect of surface roughness on convective heat transfer and fluid flow in two dimensional parallel plate microchannels is analyzed by numerically. For this purpose, single-phase, developing, laminar fluid flow at steady state and
in the slip flow regime is considered. The continuity, momentum, and energy equations for Newtonian fluids are solved numerically for constant wall temperature boundary condition. Slip velocity and temperature jump at wall boundaries are imposed to observe the rarefaction effect. Effect of axial
conduction inside the fluid and viscous dissipation also considered separately. Roughness elements on the surfaces are simulated by triangular geometrical obstructions. Then, the effect of these roughness elements on the velocity field and Nusselt number are compared to the results obtained from the analyses of flows in microchannels with smooth surfaces. It is found that increasing surface roughness reduces the heat transfer at continuum conditions. However in slip flow regime, increase in Nusselt number with increasing roughness height is observed. Moreover, this increase is found to be more obvious at low rarefied flows. It is also found that presence of axial conduction and viscous dissipation has increasing effect on heat transfer in smooth and rough channels.
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Wang, Guoqing. "Thin water films driven by air through surface roughness." [Ames, Iowa : Iowa State University], 2008.
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Cedorge, Thomas. "Surface roughness and draft angle effects on stereolithography molds." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/18199.
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Eiyo, Fumiharu. "Effect of off-road surface roughness on tyre performance." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74222.
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In this thesis, the effect of geometrical roughness of a non-deformable road surface on the mobility performance of a pneumatic tyre is investigated. A system function which represents the theoretical relationship between the drawbar-pull and the random traction surface geometry is developed in the frequency domain, associated with the energy conservation law.Prior to the analysis, measurement of road profile is achieved using an ultrasonic distance detector, and characterization of the stochastic road profile is evaluated by a power spectral density function. Further to this, the resulting drawbar-pull and tractive efficiency for a given slip rate, applied torque, tyre characteristics (as a function of inflation pressure) and vehicle moving velocity are evaluated through the above-mentioned system function.
The enveloping function, describing the modification effect of the original road profile by a flexible tyre, is also experimentally investigated. Systematic laboratory tests are carried out by using four pseudo-random rough traction surfaces, for comparison and verification of the theoretical predictions.
Through combined theoretical and experimental investigations, the following conclusions are obtained: (1) As the traveling speed increases, tractive efficiency is gradually decreased. (2) Higher slip rates give less tractive efficiency, however, an optimum slip rate between 2% and 10% provides the highest efficiency. (3) Tractive efficiency increases hyperbolically with an increase in the inflation pressure of the tyre. (4) A substantial decrease in tractive efficiency is obtained when the condition of the road surface becomes sufficiently rough that the road would be classified as "poor" or rougher under the ISO recommendations, at a speed of 5 m/s (18 km/h).
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Lundberg, Oskar Erik. "Vibrations induced by surface roughness in nonlinear rolling contacts." Licentiate thesis, KTH, MWL Marcus Wallenberg Laboratoriet, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-155049.
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For efficient transportation in either trains, busses or passenger cars, rolling elements such as wheels, tyres, bearings and transmission elements are fundamental. The energy efficiency and the generation of noise and vibrations in rolling contacts depend on the surface roughness of contacting bodies. In order to optimize the surfaces of rolling elements, prediction of its impact on the dynamic response from rolling excitation is required. A computationally efficient method to include surface roughness in the modelling of rolling contacts is presented. More specifically, nonlinear effects on the contact force due to the threedimensional shape and roughness of the contacting surfaces are introduced in a moving point force formulation. As a consequence of the point force approximation follows the assumption that any dynamic wave motion within the contact area is negligible.The rolling contact force is nonlinear due to a varying relative displacement between contacting bodies and is therefore referred to as state-dependent. A study case for the state-dependent method consisting of a steel ball rolling on a steel beam showed good agreement between numerical predictions and measured beam vibrations. Furthermore, an application to the wheel-rail interaction show that roughness-induced contact nonlinearities have a significant impact on the dynamic response caused by rolling excitation.QC 20141103
ECO2 Vehicle Design
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Sinn, Matthew T. (Matthew Thomas). "Surface roughness anisotopy on mismatched InAlAs/InGaAs/InP heterostructures." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11457.
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Muncy, Tyler J. "Topographic and Surface Roughness Influences on Tornadogenesis and Decay." Ohio University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1628513174226383.
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Ramirez, Edward A. "Gecko Digital Hyperextension: Kinematics, Surface Roughness and Locomotor Performance." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1333986580.
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Shauche, Vishwesh. "Health Assessment based In-process Surface Roughness Prediction System." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1298323430.
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Yayoglu, Yahya Efe. "Corrosion Characteristics of Magnesium under Varying Surface Roughness Conditions." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6606.
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The biggest challenge with magnesium alloy biodegradable implants is the rapid corrosion at the earlier stages of the healing process after implantation. In this research, the impact of surface roughness generated by different means on the corrosion rate of AZ31 magnesium alloy in a simulated biologic environment is investigated. In order to perform accurate experimentation, an in vitro setup is assembled that simulates the human body environment accurately has been prepared using Schinhammer’s in vitro immersion testing setup and Kokubo’s Simulated Body Fluid (SBF). For the immersion test of Mg in SBF, several surface texture groups of Mg have been prepared and submerged into the in vitro tank. The Mg samples’ comparative analysis has been made in terms of corrosion rate, total weight loss and hydrogen gas evolution within a span of 7 days for the first experiment to narrow down the scope and 14 days for the follow up experiment. After 14 days of in vitro immersion test with varying roughness and hydrophobic modifications such as Cytop coating and stearic acid modification, it has been observed that the roughness group created by etching in aqueous NaCl solution for three minutes, shows better corrosion resistance compared to the polished control group. Hydrophobic modifications on the surfaces did not affect the corrosion behavior significantly.
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Yang, Hongta. "Fundamentals, preparation, and characterization of superhydrophobic wood fiber products." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24796.
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Thesis (M. S.)--Chemical Engineering, Georgia Institute of Technology, 2008.Committee Chair: Yulin Deng; Committee Member: Jeffery S. Hsieh; Committee Member: Sujit Banerjee; Committee Member: Zhong Lin Wang.
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Valkonen, Aki Ensio. "Plastic deformation and roughness of free metal surfaces /." The Ohio State University, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487330761216718.
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Chen, Quan, and 陳全. "Efficient numerical modeling of random surface roughness for interconnect internal impedance extraction." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B3955708X.
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Sen, Mehmet Ali. "Proper Orthogonal Decomposition Methodology to Understand Underlying Physics of Rough-Wall Turbulent Boundary Layer." Fogler Library, University of Maine, 2007. http://www.library.umaine.edu/theses/pdf/SenMA2007.pdf.
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Wilson, W. Everett Jackson Robert L. "Surface separation and contact resistance considering sinusoidal elastic-plastic multiscale rough surface contact." Auburn, Ala, 2008. http://hdl.handle.net/10415/1490.
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Lee, Christopher Gee-Yin. "The design of a towed laser slopemeter system for the measurement of short scale sea waves." Thesis, University of Southampton, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295613.
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Pike-Wilson, Emily Alexandra. "Flow boiling of R245fa in vertical small metallic tubes." Thesis, Brunel University, 2014. http://bura.brunel.ac.uk/handle/2438/10625.
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The research presented is part of a larger study, dedicated to investigating flow boiling in small to microchannels. The test facility, originally designed by Huo (2005) and since used by Chen (2006) and Mahmoud (2011), has been used to investigate flow boiling of R134a across a range of channel diameters and both seamless cold drawn and welded channels. These previous studies concluded that one of the reasons for discrepancies in reported data is the result of surface characteristics. The objective of this current study is to further investigate the effect of channel characteristics and changing the refrigerant to R245fa. Surface characteristics are investigated with stainless steel, copper and brass channels, all seamless cold drawn and 1.1 mm internal diameter. Experiments using R245fa were initially conducted in the same stainless steel channel used with R134a by Mahmoud (2011). This allowed for the surface characteristics to be negated and the comparison to be based purely on the changes in the thermophysical properties between R134a and R245fa. Experiments were conducted at inlet pressures of 1.85 and 2.45 bar, mass fluxes of 100 – 400 kg/m2s, heat fluxes from 1 – 60 kW/m2 and vapour qualities from 0 – 0.95. The test section surfaces were evaluated based on scanning electron microscopy (SEM) and confocal laser microscopy (CFLSM). SEM allowed for a visual inspection of the channel surface, with clear differences in the surface stricter evident. The surfaces were then compared based on two CFLSM profilers. The values of the surface parameters differed between the two profilers but the same trend was seen, brass being the roughest surface and copper the smoothest. Changes in the surface parameter values were found to be a function of the scan area, scan resolution and cut-off value. A borosilicate glass tube, at the test section exit, allowed for flow visualisation. Mahmoud (2011) reported bubbly, slug, churn and annular flow for R134a, with no effect of hysteresis. Churn and annular flow were present for R245fa with an increasing heat flux. This was a result of a higher surface tension for R245fa which facilitates annular flow. Hysteresis was evident for R245fa, with bubbly, slug, churn and annular flow seen with a decreasing heat flux. The hysteresis effect is a result of nucleation sites activating during the increase in heat flux and remaining activated as the heat flux is decreased. The activation of nucleation sites depends on the size, which was constant due to the same channel being used, and the wall superheat. The wall superheat is lower for R245fa which does not allow for the nucleation sites to be initially activated with an increasing heat flux. The same effect of hysteresis was evident for copper and brass. Differences in the exit vapour quality and heat flux at which flow patterns occurred were seen between the three materials. The heat transfer coefficient varied in both magnitude and trend between R134a and R245fa. Mahmoud (2011) reported an almost constant heat transfer coefficient with vapour quality at a higher magnitude than seen for R245fa. R245fa showed an increasing trend with vapour quality. Peaks in the heat transfer coefficient were seen to be a result of surface flaw, evident when plotting as a function of the axial location. The test section was reversed in orientation, moving the location of the peak from near the entry of the test section to near the exit. A similar heat transfer coefficient peak was seen at the same axial location, near the exit of the test section, confirming that the peak was a result of a surface flaw and a result of the flow developing. The heat transfer coefficient changed in magnitude and trend for copper and brass. The magnitude of the recorded heat transfer coefficient did not follow the same trend as the surface parameters. The heat transfer correlations in literature did not predict the increase in the heat transfer with vapour quality, performing poorly compared with R134a. The best correlation for the prediction of both refrigerants was that of Mahmoud and Karayiannis I (2012). The pressure drop for R245fa was over 300 % higher than that of R134a, with a steeper increase with heat flux. This is attributed to a higher liquid viscosity and lower vapour density for R245fa. The pressure drop was highest for the roughest channel, brass, but lowest for stainless steel which had the intermediate roughness. The smoothest channel, copper, showed the largest difference in the effect of inlet pressure on the measured pressure drop and the roughest surface, brass, the smallest difference. The effect of surface characteristics on pressure drop is greater than the effect of changes in the fluid properties with inlet pressure. Pressure drop correlations performed poorly for R245fa in comparison with R134a, with the majority under predicting the pressure drop. Only one pressure drop correlation included a function of the surface parameters, Del Col et al. (2013), but this correlation under predicted the effect of the surface parameters on pressure drop. There was no one correlation which gave satisfactory results for all three materials.
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Bergstrom, Torbjorn S. "Quantitative Multiscale Analysis of Topographical Anisotropy on Biological and Engineering Surfaces." Digital WPI, 2019. https://digitalcommons.wpi.edu/etd-dissertations/592.
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Surfaces cover everything, and since the first standards for the measurement and characterization of surface texture were written researchers, scientists, and engineers have known that all surfaces have a directional property. This property is either an alignment of features or roughness on the surface (anisotropy), a lack of such an alignment (isotropy), or in most cases something in between. In the earliest standards written, this anisotropy of surfaces was characterized visually and referred to as “Lay.” This lay is almost always caused by the process that created the surface of question and can have significant impact on the surfaces performance when interacting with other surfaces in cases where fluids or partials are flowing over the surface. By the late 1900s researchers began to quantify surface anisotropy and by the year 2000 it had been established that surface anisotropy is a multi-scale phenomenon. In this work I look at and expand the state of the art in the characterization of surface anisotropy with examples from both biological and engineering surfaces.
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Shafizadeh, Kevan R. "A statistical analysis of factors associated with driver-perceived road roughness on urban highways /." Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/10110.
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Thoreson, Erik J. "From nanoscale to macroscale using the atomic force microscope to quantify the role of few-asperity contacts in adhesion." Link to electronic dissertation, 2006. http://www.wpi.edu/Pubs/ETD/Available/etd-010906-204218/.
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Fong, Tsz Wang. "Surface roughness parameter at synthesis of cubic boron nitride films." access abstract and table of contents access full-text, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/dissert.pl?msc-ap-b21174143a.pdf.
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Thesis (M.Sc.)--City University of Hong Kong, 2005.At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Aug. 31, 2006) Includes bibliographical references.
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Murray, Raquel. "Effects of surface roughness on bloodstain spreading and spine formation." Thesis, Cranfield University, 2016. http://dspace.lib.cranfield.ac.uk/handle/1826/10368.
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Expert witnesses employ bloodstain pattern analysis (BPA), to provide objective analysis of bloodstain evidence in criminal cases. This thesis added to the scientific understanding of BPA by generating and analysing a large data set of 785 horse blood experiments. The experiments produced impact velocities, u0, of 2:89ms-1 to 6:54ms-1, with impact angles, [theta]f , 90°, 72°, 54°, 36°, and 18°. Different surface roughnesses were investigated: conditioned and unconditioned paper, smooth steel, and three roughened steel substrates with roughness values, Ra, 1:6x10-6 m, 3:2x10-6m, and 6:3x10-6 m. To analyse the data, two computational tools were developed. The first tool extracted the diameter and velocity of a droplet from high-speed videos. The second tool measured stain properties and counted spines of stains resulting from 90° and 72°. The results of these experiments are investigated, extracting relationships between impact properties of droplets to stain properties. Each of the stain properties were related to some combination of a non-dimensional number (Bond number, Bo, Froude number, Fr, or Reynolds number, Re) and impact angle. It was found that the stain area and stain perimeter are proportional to Bo(sin[theta]f )-1. The numberof spines and/or tails on a stain is dependent on Fr(sin[theta]f )2. The major diameter is proportional to Re(sin[theta]f )2 and conversely the minor diameter is proportional to Re(sin[theta]f)2. The full length of the stain is proportional to Bo(sin[theta]f)-2. The results showed that increased surface roughness, promotes increased variability in the bloodstains, up to a limit of Ra = 6:3x10-6m. The roughest steel is statistically the same as paper in almost all stain properties. The results proved a need to account for surface roughness in modelling the spreading of a droplet on a substrate. Starting from the laws of conservation of energy, a new model for predicting spread factor was derived which accounts for the impact angle and substrate roughness. This model uses a coefficient based on properties from the stain and is able to predict the experimental spread factors in this thesis more accurately than the spread factor models in literature. Two new equations were derived that calculate the impact velocity and droplet diameter using only stain properties, not experimental fitting constants, making the expressions more robust.
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Padilla, Stefano. "Mathematical models for perceived roughness of three-dimensional surface textures." Thesis, Heriot-Watt University, 2008. http://hdl.handle.net/10399/2143.
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This thesis reports and discusses results from a new methodology for investigating the visually perceived properties of surfaces; by doing so, it also discovers a measurement or estimator for perceived roughness of 1/Fβ noise surfaces. Advanced computer graphics were used to model natural looking surfaces (1/Fβ noise surfaces). These were generated and animated in real-time to enable observers to manipulate dynamically the parameters of the rendered surfaces. A method of adjustment was then employed to investigate the effects of changing the parameters on perceived roughness. From psychophysical experiments, it was found that the two most important parameters related to perceived roughness were the magnitude roll-off factor (β) and RMS height (σ) for this kind of surfaces. From the results of various extra experiments, an estimation method for perceived roughness was developed; this was inspired by common frequency-channel models. The final optimized model or estimator for perceived roughness in 1/Fβ noise surfaces found was based on a FRF model. In this estimator, the first filter has a shape similar to a gaussian function and the RF part is a simple variance estimator. By comparing the results of the estimator with the observed data, it is possible to conclude that the estimator accurately represents perceived roughness for 1/Fβ noise surfaces.
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Kainourgiakis, Michael, Theodore Steriotis, Eustathios Kikkinides, Athanassios Stubos, and Sergey Vasenkov. "Effects of surface roughness on transport properties of porous media." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-196547.
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Venkatesh, K. "Evolution Of Surface Roughness In Machining." Thesis, 1999. https://etd.iisc.ac.in/handle/2005/1521.
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