Surfaces topography

Surface topography is often thought of in terms of surface roughness. While the surface roughness is often indicative of the topography, it must be complemented by another surface parameter to reasonably describe the surface. Surface parameters, are widely used to describe the surface roughness  

FIGURE 13.2 Surfaces with identical andiJ. (a) Plateau and (b) peak. 

The hypothetical surfaces presented are useful for illustrative purposes. The surface parameters are shown in Table 13.2. However, when the same mannfacturing technique is used to create wear specimens or actual machined components for nse often, the simple use of and are adequate for process control of an ongoing process. There are a myriad of other surface parameters that can be nsed to desaibe a snrface for tribological applications. For example, parameters snch as the radins of curvature of the asperities can also be used. A metrologist would contend that three parameters are required to adequately describe a surface, whereas a tribologist would counter that two parameters will often suffice. Note, that and essentially quantify the second moment around the mean value and those do not constitute to independent measures of the surfaee. 

The most direct way of visualizing a surface profile is to cut an object in a plane perpendicular to the average surface or surface envelope of interest and after having prepared the cut surface for metallographic examination to examine it at a suitable magnification, the mag- 

By far the great majority of surfaces encountered in engineering practice are structured, and for the most part such surfaces are finished 

In the past, most studies have examined surfaces with topographical features on the microscale level, due to limitations in nanoscale fabrication. However, recent advances in creating surfaces with submicrometer surface features have allowed analysis of more biologically relevant features. Nanometer-size topographical features more closely mimic the natural ECM, thus enabling researchers to more accurately recreate a cell s in vivo environment. 

A Summary of Topographical Features and Cell Types that have been Investigated 

Topographical features Cell type Cell functions examined 

Pits Epithelial cells Focal adhesion formation 

Wells Neurites Neutrophils Oligodendrocytes Osteoblasts Smooth muscle cells  

Most clones have tubers with an irregular surface. Spindle-shaped tubers generally have the smoothest surface (Pas ko, 1973). An irregular surface is undesirable in that it makes preparation for cooking more difficult. 

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Laser-based profilometry is now being applied to a wide variety of both NDT and Quality Control gauging applications. In the world of NDT, the primary interest is in the details associated with surface topography or deformation of a particular component. Laser-based profilometry systems are commonly used to inspect surfaces for defects such as pitting, corrosion, deformation and cracking. Quality control gauges are used for absolute measurement of dimensions, such as the diameter and thickness of a given part. 

Scaiming probe microscopies have become the most conspicuous surface analysis tecimiques since their invention in the mid-1980s and the awarding of the 1986 Nobel Prize in Physics [71, 72]- The basic idea behind these tecimiques is to move an extremely fine tip close to a surface and to monitor a signal as a fiinction of the tip s position above the surface. The tip is moved with the use of piezoelectric materials, which can control the position of a tip to a sub-Angstrom accuracy, while a signal is measured that is indicative of the surface topography. These tecimiques are described in detail in section BI.20. 

In contrast to AFM, which directly provides accurate height mfonnation in a limited range, quantitative assessment of the surface topography by SEM is possible by measuring die parallax of stereo pairs [45]. 

The simplest interpretation of stm images is in terms of surface topography. However, care must be exercised in this interpretation, since in teahty, tunneling probabiUty is really measured. The many subdeties of stm data interpretation ate beyond the scope of this article. The interested reader is referred to references 14 and 15 for a more detailed discussion of these issues. 

R. Behrisch, ed., "Sputtering by Particle Bombardment II Sputtering of Alloys and Compound, Electron and Neutron Sputtering, Surface Topography," in Topics in Applied Physics, Vol. 52, Springer-Vedag, Berlin, 1983. 

For dry traction more contact is desired and the stopping distance is directiy related, ie, the more contact area the shorter the stopping distance. A softer, more pHable compound conforms to the road surface topography. Too soft a compound (low mechanical strength) abrades more easily and can therefore acts as a roUer and not allow sufficient contact area to be maintained. This is not readily encountered in nominal tires and conditions but has been encountered in cases of extremely high torque conditions for very fast acceleration and sudden stops. 

Parameters measured Surface topography (SFM and STM) local electronic structure (STM)... 

Parameters measured Surface topography (rms roughness, rms slope, and power spectrum of structure) scattered light line shape of periodic structure (width, side wall angle, height, and period)... 

The sputtering process is frequendy used in both the processing (e.g., ion etching) and characterization of materials. Many materials develop nonuniformities, such as cones and ridges, under ion bombardment. Polycrystalline materials, in particular, have grains and grain boundaries that can sputter at different rates. Impurities can also influence the formation of surface topography. ... 

Much work since this period [4] has reinforced the importance of surface topography in these areas of adhesion. Two recent examples will be cited. 

Packham, D.E., The adhesion of polymers to metals the role of surface topography. In Mittal, K.L. (Ed.), Adhesion Aspects of Polymeric Coatings. Plenum, London, 1983, p. 19. 

Surface topography can affect the local wind patterns one example is the onshore and offshore breeze, and another example is the heat island over large urban areas. Another manmade effect is the generation of mechanical turbulence caused by the nonuniform height of buildings in a city. We will discuss this effect in more depth later on. 

In the reductive regime, a strong, apparently irreversible, reduction peak is observed, located at -1510 mV vs. the quasi reference electrode used in this system. With in situ STM, a certain influence of the tip on the electrodeposition process was observed. The tip was therefore retracted, the electrode potential was set to -2000 mV, and after two hours the tip was reapproached. The surface topography that we obtained is presented in Figure 6.2-14. 

Myers, J. R., Crow, W. B., Beck, F. H. and Saxer, R. K., Observation on the Anodic Behaviour of Nickel and Chromium Surface Topography and Temperature Effect , Corrosion, 22, 32 (1966)... 

The sample is measured with a confocal microscope, by using a chromatic coding of the height, and with a contact-less optical needle focused on the surface. We determine by this way the surface topography and its roughness. 

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