The tribological properties of cast iron have been investigated to determine the effects of micro-texturing the surfaces. The micro-textured surfaces were prepared by shot blasting or milling using a shaper. The surfaces with groove patterns and mesh patterns had higher friction coefficients than the flat surfaces. The surfaces with dimpled patterns had lower friction coefficients than the flat surfaces. The results indicated that the dimpled pattern had a beneficial effect by decreasing the friction.
The effects of surface texture on the tribological properties of slideways were investigated experimentally. The authors designed an experimental apparatus for evaluating textured surfaces using specimens of a practical size (82 mm × 82 mm) considering the slideways used for machine tools which are one of the application fields for their research. The evaluated textures were dimple and groove textures, and their diameters and widths varied from 50 µm to 1 mm. The textures were processed by sandblasting as it is one of the alternative methods applied in industry. For comparison with the conventional textures, scraped surfaces were also evaluated. The friction coefficient and the film thickness were measured under the conditions of plane contact, and lubricating with the oil to clarify the effects of the textured pattern. The experimental results showed that the friction coefficient of the textured surfaces was smaller than that of the flat surfaces in the mixed lubrication regime. Regarding the mechanisms of friction reduction by texture types, the authors think that the dimples played the role of oil reservoir, and the parallel grooves prevented side leakage of the lubricating oil.
We used atomic force microscopy (AFM) for the indentation test evaluating the indentation hardness of materials in the nanometer range. BK7, fused silica, and single-crystal silicon were used as test sample materials. The data analysis processes used to determine the contact area were important in evaluating the indentation hardness of the materials. The direct measurement of the size of the residual hardness impression was useful in evaluating the contact area even in the nanometer region. The results led us to conclude that AFM indentation using a sharp indenter is a powerful method for estimating the indentation hardness in the nanometer range.
Top-down fabrication processes for nanostructures are superior to bottom-up processes from the aspect of long-range order, but have limitations in their processing time and/or material selection. Here we developed a nanopatterning method for 'nanostripes' that incorporates deposition of a multilayer film on a microscale slope array and mechanical polishing. This method is used to fabricate a nanostripe structure consisting of two kinds of materials to form a stripe array on a silicon substrate. Although this nanopatterning method is categorized as a top-down fabrication process, the fabrication efficiency is quite high, because the number of nanostripes is 'multiplied' by the number of multilayered films. Another feature of the nanostripe is renewability; even if the nanostripe surface is damaged, the underlying nanostructure can be exposed and form a similar nanostripe by polishing. The nanostripe structure can be easily applied to a wide range of fields due to its ease of production.
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