The geometry of micro-scale textures and the relative motion of surfaces in contact may affect the performance of an elastohydrodynamic lubrication interface. Reported in this paper are the investigations of the effects of texture bottom shape and surface relative motion on lubrication enhancement using numerically generated textures by means of model-based virtual texturing and numerical simulation. These textures are on one of the interacting surfaces in a triangular distribution and have the same density. The results suggest that the bottom shapes involving a micro-wedge and/or a micro-step bearing tend to yield thicker films. The lubrication of selected textured surfaces was also studied under three different relative motions: texture surface moving, un-textured surface moving, and both moving. The results indicate that textures on the faster moving surface offer stronger film thickness enhancement.

Micro-scale textures may be engineered into surfaces for lubrication performance improvement. It is expected that a carefully chosen texture helps retain lubricant and enhances the hydrodynamic effect at the interface. The concept of model-based virtual texturing enables textured surfaces to be generated and ''tested'' through numerical simulations. This paper reports virtual texturing and simulation of a group of textured surfaces in a lubricated concentrated contact. The focus of the study is on the selection of texture distribution patterns based on their lubrication performance. Patterns of fishbone, sinusoidal, triangular, and honeycomb distributions have been investigated. The effects of texture direction, orientation angle, feature continuity, and aspect ratio are also studied. The results indicate that, for the given material and geometry system under the given conditions in the present work, the textures generating the strongest hydrodynamic lifting are short grooves with a small aspect ratio and sinusoidal waves of a small wavelength/amplitude ratio propagating in the motion direction.

A model-based virtual texturing approach has been developed and applied to design, generate, 'test', and evaluate textured surfaces through numerical simulations. A series of studies on the numerical generation and performance evaluation of textured surfaces in a lubricated concentrated contact has been conducted, which includes (a) numerical generation of a large variety of textures considering possible geometric imperfections that exist in reality due to tooling design considerations and fabrication errors; (b) determination of texture depth, size, and area density; (c) texture distribution pattern selection; (d) bottom shape comparison and design optimization; (e) investigation of the influence of surface relative motion; (f ) prediction of performance deviation caused by texture shape imperfections; and (g) evaluation of the effect of originally machined roughness. The present study was conducted using the deterministic mixed elastohydrodynamic lubrication (EHL) model recently developed, modified, and validated, which appears to be useful for surface texture design based on comparative performance evaluation in a wide range of operating conditions.

The effects of Zn-based alloys coating (Zn, Al-Zn and Al-Mg-Zn) on the bondability of steel/aluminum alloy dissimilar metals joints were evaluated, in order to achieve strength in lower welding current. In the joint with Zn-based alloys insert, the oxide film on the aluminum alloy was sufficiently removed through eutectic reaction of Zn-based alloys and aluminum. In the joint with Zn-coated steel (GI), higher welding current is necessary to discharge the zinc coating and the oxide film from the bonding interface sufficiently. The thinner aluminum plate after welding and the thick reaction layer cause the decrease of cross tensile strength in the joints with no coating steel (SPCC) and Al-Zn-coated steel. Using Al-Mg-Zn-coated steel, higher strength was achieved in a lower welding current. This is because Al-Mg-Zn-coating melted at lower temperature than Zn and Al-Zn-coating, and the removal of the coating material and the oxide film on the aluminum alloy were sufficiently performed in the lower welding current.

Increasing the traction coefficient of a traction drive system is a key factor in obtaining a smaller, lighter unit and also greater torque capacity. This study focused on the microtexture of the rolling elements, and effect of microtexture was examined with the aim of improving the traction coefficient in the viscous region. Three texturesdimple, transverse, and longitudinal-were examined using a 4-roller tester that enabled tests to be conducted under high pressure and high rolling speed. As a result, it was found that the longitudinal surface texture is the best for improving the traction coefficient. The results obtained with EHL analysis showed that only the surface texture with longitudinal grooves increased the traction coefficient, just as in the tests conducted with the 4-roller tester. The longitudinal surface texture was optimized using the 4-roller tester. The test results made it clear that the groove depth, groove pitch, and also the radius of curvature of the convex portion of the rolling elements are important parameters of the longitudinal grooves for improving the traction coefficient while assuring high durability at the same time. An attempt was then made to increase the traction coefficient of an actual CVT variator by applying the optimized longitudinally grooved microtexture to the traction surfaces. The test results show that the traction coefficient can be increased without sacrificing durability by optimizing the surface microtexture.