Tomomi Honda

Wear behaviour of high tensile strength aluminium alloys under dry and lubricated conditions

Abstract The wear behaviour of high tensile strength aluminium alloys was studied by rubbing them against a steel counterface under both dry and lubricated conditions. The test materials used were extruded AlZnMg alloy (7004-T6) and AlCuMg alloy (2024-T4). In laboratory air, the mild wear rates of both aluminium alloys were almost the same. However, 7004-T6 easily caused severe wear at high contact loads. In paraffin oil, the wear rates were about 1/10 the wear rates under dry conditions. The wear rate of 7004-T6 was greater than that of 2024-T4, but the difference became smaller with increasing contact load. 7004-T6 showed a lower friction coefficient compared with 2024-T4 at every contact load. When the wear rates were compared at the same friction force, the rate of 7004-T6 was greater than that of 2024-T4 at every friction force. This result was due to the difference in wear particle sizes. Namely, for 7004-T6, wear cracks which would propagate in the sliding direction occurred and large and elongated wear particles were detached. For 2024-T4 many small wear cracks were caused, resulting in detachment of small wear particles. These differences in wear behaviour seem to be affected by the material properties which are responsible for the difference in fatigue behaviour rather than tensile strength or hardness. The results of this study are useful for selecting materials for machine design and of interest in understanding the relationship between wear and fatigue.

A Study of the Colors of Contamination in Used Oils

The color of contaminants in used oils has not been investigated until recently. There are several good color standards. The CIExy coordinate, which is used in color engineering, is a popular color standard to locate a color of a product. The CIExy coordinate can be used for the colors of contaminants in used oil, but it is difficult to understand how the color is located in that position in the coordinate. The authors have developed a colorimetric patch analyzer (CPA) with the red–green–blue (RGB) color system to study the color of contaminants in used oils that were collected by membrane patches. The first CPA model examined the color of contaminants trapped on the surface of the membrane patches by reflected light similar to the currently available colorimetric analyzers. Some contaminants are soluble in working gas turbine oils at temperatures of 65°C or higher but become insoluble in oils when the oils are cooled to room temperature for 24 h. Therefore, the colors of contaminants differ according to oil temperature at the time of filtering through membrane filters. When the membrane patches through which hot turbine oils were filtered were examined with the light from the back, they showed light brown colors, although the color of the surfaces were white. This suggests that the membrane patch traps contaminants in the oil passages of the membrane patches when oil flows through the patches. The molecular weight of contaminants that are soluble in oil at high temperatures but not at room temperature was examined by gel permeation chromatography (GPC). The University of Fukui developed a state-of-the-art CPA that can examine the contaminants on the surface of membrane patches by reflected light and contaminants in the membrane patches by transmitted light.

Measurement of the Potential of Static Electricity Generated by the Friction of Oil Lubricated Metal on Metal

It is known that electricity appears when two bodies contact or cause friction. Although tribology is the science of lubrication, friction and wear, very little has been discussed about the electricity due to friction. One of the authors has studied generation of static electricity during oil filtration and its effects on oil oxidation. This study deals with generation of static electricity while a metallic ball slides on a lubricated metal. The experiment was conducted at various sliding velocities under the lubricated conditions by using a modified pin-on-disc machine. The static electricity, which was accumulated on the insulated pin and ball assembly, was measured. Within the range of the experiment, it was found that both the potential of the static electricity and the frequency of its discharges would increase in proportion to the sliding velocity. Presented as a Society of Tribologists and Lubrication Engineers Paper at the STLE/ASME Tribology Conference in San Francisco, CA October 21–24, 2001

A Rapid Enrichment Technique for the Ultratrace Determination of Nickel in Water Samples Using a Nanofiber-composite Membrane Filter

A new method for the rapid enrichment and highly sensitive determination of nickel ion has been developed by using a nanofiber-composite membrane filter, which was fabricated by stacking a nanofibrous material made of nylon 6 over a water-permeable membrane filter. The noncharged nickel-α-furil dioxime complex was adsorbed on a nanofibrous layer of the membrane filter under significantly higher flow rates than those used for conventional solid-phase extraction techniques. Highly sensitive determinations with detection limits at sub-parts per billion levels were achieved by enrichment from 50 mL of the complex solution, and the enrichment was completed within 3 min. The color that was developed on the membrane filter was successfully subjected to visual colorimetric analysis and quantitative determination by solid-phase spectrophotometry. In addition, colorimetric determination was feasible with a handheld spectrometer after elution of the colored agent with 50 μL of acetone. This combination of rapid enrichment and spectrometric measurement in a small-volume sample provides a useful analytical method suitable for on-site analysis, which requires neither expensive instruments nor high laboratory skills.

Wear Behavior of Carbon Steels and Stainless Steels in NaCl or Na2SO4 Solution.

Sliding wear tests of carbon steels and stainless steels were conducted in various environments. The mild and the severe wear modes, and their transition occur in NaCl and Na2SO4 solutions as well as in dry conditions for every test materials. The transition loads of SUS304 and SUS630 are smaller than those of carbon steels and SUS440C in NaCl and Na2SO4 solutions. The ranking of the transition loads among these steels can be estimated from their corrosion potential, that is, less noble steels show high transition loads. The mild wear rates of stainless steels at low load, which are smaller than those of carbon steels, decrease with an increase in corrosiveness of liquid. From the experimental results, criteria for selection of antiwear materials in corrosive liquid environments are proposed.

Local Modification Method for B-Spline Curve in the General CAD System.

Recently, computer-aided design (CAD) systems are being used for total design from conceptual design to detailed design. Designers desire a CAD system which can draw their image faithfully. However, it is considerably difficult to modify the drawn curve in the present popular CAD systems. In this study, we developed a new local modification method for a B-spline curve by performing an inverse transformation of the B-spline curve. The influential range of each control point becomes narrow because of the increase of the number of control points, so that it is possible to modify the curve locally with mathematical smoothness. Furthermore, our developed method was linked to the general CAD and its availability was confirmed from the standpoint of execution time and handling.