Papers by Keyword: Surface Texturing

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Authors: Jian Xin Deng, Ze Wu, Yun Song Lian
Abstract: Textured self-lubricated tools were designed and fabricated. Dry cutting tests were carried out on with these self-lubricated tools and a conventional tool. The tool wear and the friction coefficient at the tool chip interface were measured. It was shown that the tool wear and the friction coefficient of the textured self-lubricated tools were reduced compared with that of the conventional tool. Two mechanisms responsible were found, the first one is explained as the formation of a lubricating film with low shear strength at the tool-chip interface, which was released from the texturing and smeared on the rake face, and served as lubricating additive during dry cutting; the other one was explained by the reduced contact length at the tool-chip interface of the textured tools, which contributes to the decrease of the direct contact area between the chip and rake face. It is suggested that the using of textured self-lubricated tools is an effective way to reduce the tool wear in dry cutting.
414
Authors: Adam Szurdak, Gerhard Hirt
Abstract: Micro lubrication pockets decrease the frictional losses and improve the wear resistance of lubricated machine elements. Depending on the application, the pocket dimension and the area density (ratio of the projected pocket area to the non-textured area) must be optimized. Otherwise, the lubrication pockets might increase friction and wear. Besides the determination of the optimized texture, the production process needs to manufacture the pockets with high reproducibility and accuracy, since each deviation of the texture might reduce the improvement of the tribological properties. The goal of this work is to develop a new forming setup capable of decreasing the influence of deviations in the material, of the tool or due to a process inaccuracy ́s. Therefore, a roller-coining process based on a pneumatic system was developed to keep the forming force and thus the pocket dimension constant. This setup was as well used to texture the roller, since the manufacturing of a prominent micro texture on a curved surface with high tolerances is a difficult task for other texturing methods. The experimental verification of the setup showed that by using the pneumatic setup the standard deviation of the pocket depth was reduced by an average factor of 1.9.
128
Authors: Yasuhiro Takada, Mitsuru Shinozaki, Minoru Ota, Kai Egashira, Keishi Yamaguchi, Yoshitaka Hattori
Abstract: Whirling electrical discharge texturing (WEDT) was developed to process microstructures on the inner surface of cylindrical parts made of high hardness materials. However, the minimum processable diameter of the cylindrical parts was φ 5 mm and the equipment could not feed the new tool electrodes. Therefore, the authors devised a novel method of WEDT using a straight wire tool electrode for a cylindrical surfaces with a small diameter. It was confirmed that microstructures could be created on the inner surface of a cylinder of φ 1.1 mm diameter, and that the texture-area ratio could be controlled by the workpiece feed speed. Moreover, new EDT equipment with a feeding system for a wire tool electrode and a bending system for the tip of a wire tool electrode was developed. As a result, the equipment that can process microstructures on the inner surface of a cylinder with a small diameter and feed a wire tool electrode during texturing was successfully developed.
384
Authors: Jing Hu Ji, Hao Wang, Yong Hong Fu
Abstract: This paper develops an analytical model to investigate the effect of elliptical dimples on hydrodynamic lubrication of surface contact. The hydrodynamic pressure generated by elliptical dimples is solved by the multi-grid method. The evaluation criterion of hydrodynamic effect of dimensionless average pressure is calculated and presented with the variation of elliptical dimple depth, area density, slender ratio and inclination angle. The results indicate that geometrical parameters of elliptical dimples have an obvious influence on the hydrodynamic pressure. The hydrodynamic lubrication performance can be ameliorated by optimizing the geometrical parameters of elliptical dimples according to the operating parameters of the mechanical components.
474
Authors: Heng Sheng Lin, Ying Chieh Lin, Ming Ru Lee
Abstract: The miniaturization of products has driven the demand for better realization in the micro forming process. Micro sheetmetal forming becomes more susceptible to friction attributed to the decrease in the weighting of body force and the increase in surface force, as the size of workpiece decreases. In this work, micro cupping tests were utilized to test the influence of workpiece thickness and surface texturing both on stainless steel and copper sheets under an oil-lubricated condition. Three thickness gauges of workpiece, 0.05, 0.1 and 0.2 mm, were selected in order to represent the micro, meso and macro forming conditions, respectively. Longitudinal and isotropic lay conditions were obtained through imprinting the textured rolls produced by grinding and sand blasting methods. The result of the micro cupping tests show that the cup heights are comparable for both longitudinal and isotropic lays in forming the sheets of 0.1 and 0.2 mm thickness. However, isotropic lay has a greater cup height than that of longitudinal lay in forming the 0.05 mm sheets. This indicates that surface texturing becomes influential in the formability of micro sheetmetal forming.
420
Authors: Xu Dong Peng, S.E. Sheng, J.Y. Li, X.M. Pan, S.X. Bai
Abstract: A Reynolds equation is presented for the hydrodynamic pressure components between the two faces of a partially or fully laser surface textured mechanical seal (LST-MS) by considering the hydrostatic and hydrodynamic characteristics and cavitation within the sealing fluid film. Galerkin’s method is used to set up the finite element model for the Reynolds equation. The effects of geometric parameters of the spherical dimple on seal performance of a LST-MS are studied. The texturing parameters are numerically optimized to obtain the maximum opening force and/or the maximum ratio of fluid film stiffness to leakage rate. It is shown that a full LST-MS has stronger hydrodynamic effect and lower frictional torque between the two faces than that of a partial LST-MS, but the latter works at a less leakage and a more stable working state. Thus a partial LST-MS is recommended for practical application for its better comprehensive seal performance.
766
Authors: Jong Cheon Park, Ok Geun Jeong, Sang Youn Kim, Tae Gyu Kim, Jin Kon Kim, Hyun Cho
Abstract: SF6/O2 plasma surface texturing was employed to pretreat Si substrate for achieving enhanced diamond nucleation density. Surface roughness of the textured Si was found to be strongly dependent on the process pressure and normalized roughness values in the range of 2-16 were obtained. Remarkably enhanced nucleation densities of ~1010 cm-2 compared to conventional mechanical abrasion were obtained after seeding for the surface textured Si substrates. Raman spectroscopy revealed that ultrananocrystalline diamond films with grain size below 10 nm were grown on the surface textured Si.
61
Authors: Min Soo Suh, Young Hun Chae
Abstract: Surface texturing, a sort of surface engineering, has been studied as an effective method to improve the tribological performance under lubricated contact. Those mechanisms of friction reduction, however, are not fully understood. Therefore, the sliding direction and the angle of micro-grooved crosshatch patterns for coefficient of friction were examined. The micro-grooved crosshatch pattern was fabricated by mechanical indentation method on the upper specimen and the pin-on-disc friction test was performed with lubricant of paraffin oil. The influence of angel on the friction was confirmed as friction coefficient increased proportional to the angle increase. The micro-grooved crosshatch patterns have also the potential to change the friction characteristics by sifting the lubrication regimes.
507
Authors: A.A. Fashina, K.K. Adama, M.G. Zebaze Kana, Winston O. Soboyejo
Abstract: We investigate the effect of surface texturing on the light trapping properties of Silicon wafers as a function of reflection reduction and surface morphology. This was achieved by structuring a random square-based pyramids pattern on the surface of Silicon substrate using anisotropy etching. The light trapping effect was optimized for silicon solar cells by investigating the dependence of the silicon surface texturing on the process parameters such as etchant concentration, etching time and temperature. We study the surface morphology by analyzing the surface behaviour of the textured substrate using the atomic force microscope and scanning electron microscope. The results of roughness and optical reflection were obtained using the surface profiler and the UV/VIS the spectrometer respectively. In addition, an analytical modelling method was developed to determine the angles of incidence of light rays with each of the facets of the pyramids and the coordinate of the reflected light rays. The method used here is based on 3-D vector geometry of the pyramidal facets. The optimum parameters are found to be 40min, a temperature of 80oC and with KOH/IPA/DI in the ratio [2:4:46] by volume, yielding a surface roughness over 600 nm and a relative optical reflectance in the visible spectrum less than 10%, using polished Si as reference. The results and analysis of both the modelled and measured reflectance, suggest that the performance of the light trapping technique has a big potential in silicon solar cells application.
144
Authors: Salaheldin A. Mohamad, Qun Zheng, Xi Qun Lu
Abstract: Piston ring lubrication in some types of low-speed 2-stroke marine diesel engines is completely different from those in medium-or high-speed diesel engines since the inner surface of cylinder liners are textured with circular grooves in macro-scale and honing texture in micro-scale. In this paper, a numerical model has been developed to study the potential of use of cylinder bore surface texturing, in the form of circumferential oil grooves with different dimensions and densities, and their efficiency to improve the tribological properties of piston ring-cylinder liner tribo-system. The average Reynolds equation has been employed in the area of micro-scale texture and the effect of macro-scale grooves has been incorporated to improve the currently lubrication model. The results showed that the cylinder liner oil grooves can efficiently be used to maintain hydrodynamic effect. It is also shown that optimum surface texturing may substantially reduce the friction losses between piston ring and cylinder liner.
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