At present there are no generally accepted and experimentally confirmed, 2D or 3D, deterministic, asperity-deformation models to evaluate the real contact area in tribological applications. One of the key obstacles is that there are no clear and experimentally verified criteria about how to define and consequently determine the actual load-carrying asperity peaks. As a result, this work attempts to clarify how different, arbitrarily selected, asperity-peak identification criteria affect the calculated asperity-peak properties, i.e., the number, radii and heights. Such an analysis is still missing from the literature on 2D and 3D, asperity-peak analyses and is required for a better understanding of the physical meaning and engineering feasibility, and thus more realistic assumptions about these criteria.
COBISS.SI-ID: 12768795
In any attempt to theoretically calculate the real contact area for 3D engineering surfaces, a criterion is needed to identify the relevant asperity-peaks that carry the load in tribological contacts. In our recent work, we investigated how different, available 2D criteria affect the properties of the theoretically determined asperity-peaks in 2D surfaces. In this work, however, we focused on a 3D surface characterisation. The effect of different asperity-peak identification criteria on the properties of the asperity-peaks (numbers, radii and heights) is studied in the 3D domain. Several different criteria that take into account the number of neighbouring points, the distances between them (lateral resolution) and their heights were evaluated for real measured surfaces with five different surface roughnesses in the broad engineering range of arithmetic surface roughness from Sa=0.005um to Sa=0.529um. From the results it follows that all three chosen asperity-peak identification criteria (5PP-3D, 9PP-3D and 9PP-R-3D) result in reliable asperity-peak properties, and none of them can be favoured based on a theoretical evaluation only. There are, however, important differences between them. The data resolution in the x and y directions has a very important influence on the numbers, radii and heights of the asperity-peaks, and the results suggest that the data's lateral resolution, below 1um, should be used for the relevant asperity-peak identification.
COBISS.SI-ID: 13208603
The paper reports on the successful anodic codeposition of submicrometer SiC powder and multiwalled carbon nanotubes from aqueous suspensions to form SiC–CNT composites. On the basis of the comprehensive analysis of the aqueous suspensions with different pHs, solids contents, and CNT contents, optimal conditions for deposition were determined. Besides having the necessary high absolute value of the ζ-potential, the suspensions that resulted in firm deposits were characterized by limited conductivity ((1 mS/cm). Lowering of suspension conductivity was achieved either by dilution of the suspension or by dialysis of the as-received CNT suspension with high intrinsic conductivity. Selected SiC–CNT deposits were further densified by use of the polymer infiltration and pyrolysis process.
COBISS.SI-ID: 26160167