Grease film evolution in rolling elastohydrodynamic lubrication contacts

Although most rolling element bearings are grease lubricated, the underlying mechanisms of grease lubrication has not been fully explored. This study investigates grease film evolution with glass disc revolutions in rolling elastohydrodynamic lubrication (EHL) contacts. The evolution patterns of the grease films were highly related to the speed ranges and grease structures. The transference of thickener lumps, film thickness decay induced by starvation, and residual layer were recognized. The formation of an equilibrium film determined by the balance of lubricant loss and replenishment was analyzed. The primary mechanisms that dominate grease film formation in different lubricated contacts were clarified.

Aging Detection of Glass Disc Insulator by using Infrared Camera

<p>Suitable diagnostic techniques for outdoor glass insulators are important for ensuring the reliablilty and stability of power system. The possibility of insulator flash-over increases, especially when the insulator is covered by pollution layers or has an internal defect. In this paper, a new technique to detect the pollution level and invisible damage by measuring the surface temperature of glass disc insulators is proposed. A high definition camera had been used to determine the surface temperatures of four glass insulators. The effects of applied voltage on the surface temperature and its distribution were studied. The results show the possibility of using the infrarad camera to detect the aging level and invisible damages of the glass insulators.</p>

Leakage Current Based Thermal Modeling of Glass Disc Insulator Surface

The stability of transmission lines relies on the health of the insulators, such as glass string insulators, which may occasionally flashover during an overvoltage. The likelihood of flashover increases notably when the glass insulator is wrapped by a wet contaminant layer. In this paper a study of the surface thermal profile of glass disc insulators insulation had been carried out for both clean and polluted surfaces. A finite-element simulation with time dependent model was carried out using COMSOL Multiphysics software. The variation of the insulator surface temperature with applied voltage as well as with pollution layer thickness is explained. The results illustrate the significant effect of pollution conductivity on heat propagate along the surface of the glass insulators with the increase higher voltages' magnitudes. Study of the aging level impact on a steady state thermal for glass insulation surface is also carried out.

AN EXAMINATION OF OIL FILM THICKNESS IN A BALL-ON-DISC ASSEMBLY

The results of oil film thickness investigations in non-conformal contact in sliding pairs with modified surfaces are presented in the article. The investigations were realized on a ball-on-disc instrument with colorimetric interferometry. Balls were made from 100Cr6 steel of hardness 60–62 HRC. The diameter of balls was 19.05 mm. The tests were carried out at the applied loads of 20 N and 30 N. The glass disc rotated at speeds from 0.1 m/s to 0.2 m/s. At the highest speed (0.2 m/s) the highest maximum value of the oil film thickness of 217 nm was obtained. At 0.2 m/s, the oil film thickness was up to 82% greater than at 0.1 m/s. At 0.1 m/s the maximum oil film thickness values were 100–157 nm. The greatest maximum values of the oil film thickness were received by balls with the smaller surface height application in all of the studied cases.

A Novel Method to Determine EHL Film Thickness with Optical Interference

In this work, a new method to determine the interference grade of the central film is put forward. The interference figure is generated on a steel ball and a glass disc with a green monochromatic two-beam interferometry. With gradually increasing the rotational speed of the glass disc, the corresponding interference intensities of the central contact area are continually collected and sent to the computer. With these data, the periodical curve of the central interference grey value with the sliding speed has been drawn. Then, the curve is compared with the theoretical result so that the central interference grade of each figure can be determined. It has been found that while the sliding speed varies from 0.09 m/s to 0.21 m/s, the central interference grade of the interference figure is the first under the working conditions of the present paper. As the sliding speed increases between 0.21 m/s and 0.4 m/s, the second grade of the central interference figure is achieved. As the central interference grade has been known, the film thickness and the film shape can be easily determined by the interference picture of the EHL film and the relative optical intensity principle.

Crystal Zoetrope: New Visual Medium for Displaying 3D Animation

The authors have turned the Zoetrope, initially an optical toy from the pre-cinema era, into a three-dimensional (3D) animation display. “Crystal Zoetrope” is a new visual medium involving a glass disc with numerous engraved objects that displays a sophisticated 3D animation. It can be built in small sizes and even be embedded in everyday objects or environments. Using this new visual medium, the authors produced the 3D animation “Sea of Stars” that portrays the life cycle of planets in the universe.