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.

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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.

The tribological properties of patterned surfaces were investigated under lubricated conditions. Micropatterns were fabricated on a Si surface using a combination of photolithography and plasma etching. NiFe film with a 150 nm thickness was then deposited on the patterned Si surface. We prepared four kinds of patterned surfaces: dimple, grating, bump, and mesh patterns. The dimensions of the patterns were: size 30-40 lm, pitch 120 lm, and depth 10-12 lm. Friction tests were carried out using a pin-on-plate tribometer. The pin specimen was made of cast iron and had a flat end. The normal load was varied from 9.8 to 98 mN, and the average sliding speed from 1.0 to 5.0 mm s -1 . Slideway lubricating oils or a gear oil were used as the lubricant, and the ISO viscosity grades of these oils were VG32, VG68, and VG320. The results showed that the friction coefficients of the two reverse patterns showed very similar tendencies and that circular patterns had a lower friction coefficient than did the rectangular patterns at a high bearing characteristic number. The surface geometry of the Si surface did not affect the friction coefficients at a low bearing characteristic number.

The tribological properties of nanostripe surface structures were investigated using a pin-on-plate tribometer in order to propose a design concept for improving the tribological properties. The authors used four kinds of nanostripe structures consisting of different combinations of materials (Fe–Au, C–SiC, Al–Al2O3 and Al–Pt) fabricated by a process they had previously proposed. The frictional properties of the nanostripe structures depended on the materials that constituted the nanostripes. When the sliding direction in friction tests was parallel to the microgrooves, nanostripe structures remained on all surfaces even after friction tests. Based on the friction test results, the authors considered a design concept for nanostripe structures in tribological applications.

We have developed a new method for measuring time intervals of Acoustic Emission (AE) generation for diagnosis of a radial rolling bearing. The method makes the AE signal itself a trigger of the oscillation of the clock pulse and measures the time interval of AE generation by integration of the clock pulses. The measurement device consists of the threshold, clock, time interval measurement and memory circuit, and was applied to rolling contact fatigue experiments. It was confirmed by the experiments that the measured time intervals of AE generation on the inner raceway or the ball agreed with the value calculated based on the kinetics of the rolling bearing. Moreover, we could identify the elements in which a fatigue crack was propagating by the method before the spalling appeared. The identified elements agreed with the failed elements.