The application of surface textures has been employed to improve the tribological performance of various mechanical components. Various techniques have been used for the application of surface textures such as micro-d...The application of surface textures has been employed to improve the tribological performance of various mechanical components. Various techniques have been used for the application of surface textures such as micro-dimple arrays, but the fabrication of such arrays on cylindrical inner surfaces remains a challenge. In this study, a dry-film photoresist is used as a mask during through-mask electrochemical micromachining to successfully prepare micro-dimple arrays with dimples 94 lm in diameter and 22.7 lm deep on cylindrical inner surfaces, with a machining time of 9 s and an applied voltage of 8 V. The versatility of this method is demonstrated, as are its potential low cost and high efficiency. It is also shown that for a fixed dimple depth, a smaller dimple diameter can be obtained using a combination of lower current density and longer machining time in a passivating sodium nitrate electrolyte.展开更多
为研究激光表面微凹坑对AZ31B镁合金耐腐蚀性能的影响,利用光纤激光器在材料表面制备微凹坑阵列。通过扫描显微镜观测微凹坑的形貌、直径和深度,利用双单元电化学工作站测试微凹坑制备前后材料表面的动电位极化曲线。结果表明:微凹坑的...为研究激光表面微凹坑对AZ31B镁合金耐腐蚀性能的影响,利用光纤激光器在材料表面制备微凹坑阵列。通过扫描显微镜观测微凹坑的形貌、直径和深度,利用双单元电化学工作站测试微凹坑制备前后材料表面的动电位极化曲线。结果表明:微凹坑的直径和深度均随激光功率的增大而增大,微凹坑周围出现烧蚀现象;微凹坑直径与扫描次数无显著相关性,但微凹坑圆度与扫描次数呈正相关性。在相同微凹坑密度下,与未处理试样相比,激光功率为6、10、16 W时试样的自腐蚀电位分别向正移-33、40、26 m V,自腐蚀电流分别减少了91.93%、92.09%、91.19%。激光功率为10 W时具有最好的抗腐蚀性能;在相同激光功率下,与未处理试样相比,微凹坑密度为1.5%、2.5%、5.0%时试样的自腐蚀电位分别向正移21、40、56 m V,自腐蚀电流分别减少了92.22%、92.09%、94.05%。在实验密度范围内,微凹坑密度越高,AZ31B镁合金表面的抗腐蚀性能越好。展开更多
Surface texturing has been applied to improving the tribological performance of mechanical components for many years. Currently, the researches simulate the film pressure distribution of textured rough surfaces on the...Surface texturing has been applied to improving the tribological performance of mechanical components for many years. Currently, the researches simulate the film pressure distribution of textured rough surfaces on the basis of the average flow model, and however the influence of roughness on the film pressure distribution could not be precisely expressed. Therefore, in order to study the hydrodynamic lubrication of the rough textured surfaces, sinusoidal waves are employed to characterize untextured surfaces. A deterministic model for hydrodynamic lubrication of microdimple textured rough surfaces is developed to predict the distribution of hydrodynamic pressure. By supplementing with the JFO cavitation boundary, the load carrying capacity of the film produced by micro-dimples and roughness is obtained. And the geometric parameters of textured rough surface are optimized to obtain the maximum hydrodynamic lubrication by specifying an optimization goal of the load carrying capacity. The effect of roughness on the hydrodynamic pressure of surface texture is significant and the load carrying capacity decreases with the increase of the roughness ratio because the roughness greatly suppresses the hydrodynamic effect of dimples. It shows that the roughness ratio of surface may be as small as possible to suppress the effect of hydrodynamic lubrication. Additionally,there are the optimum values of the micro-dimple depth and area density to maximize the load carrying capacity for any given value of the roughness ratio. The proposed approach is capable of accurately reflects the influence of roughness on the hydrodynamic pressure, and developed a deterministic model to investigate the hydrodynamic lubrication of textured surfaces.展开更多
基金supported by the Joint Funds of the National Natural Science Foundation of China and Guangdong Province(No.U1134003)
文摘The application of surface textures has been employed to improve the tribological performance of various mechanical components. Various techniques have been used for the application of surface textures such as micro-dimple arrays, but the fabrication of such arrays on cylindrical inner surfaces remains a challenge. In this study, a dry-film photoresist is used as a mask during through-mask electrochemical micromachining to successfully prepare micro-dimple arrays with dimples 94 lm in diameter and 22.7 lm deep on cylindrical inner surfaces, with a machining time of 9 s and an applied voltage of 8 V. The versatility of this method is demonstrated, as are its potential low cost and high efficiency. It is also shown that for a fixed dimple depth, a smaller dimple diameter can be obtained using a combination of lower current density and longer machining time in a passivating sodium nitrate electrolyte.
文摘为研究激光表面微凹坑对AZ31B镁合金耐腐蚀性能的影响,利用光纤激光器在材料表面制备微凹坑阵列。通过扫描显微镜观测微凹坑的形貌、直径和深度,利用双单元电化学工作站测试微凹坑制备前后材料表面的动电位极化曲线。结果表明:微凹坑的直径和深度均随激光功率的增大而增大,微凹坑周围出现烧蚀现象;微凹坑直径与扫描次数无显著相关性,但微凹坑圆度与扫描次数呈正相关性。在相同微凹坑密度下,与未处理试样相比,激光功率为6、10、16 W时试样的自腐蚀电位分别向正移-33、40、26 m V,自腐蚀电流分别减少了91.93%、92.09%、91.19%。激光功率为10 W时具有最好的抗腐蚀性能;在相同激光功率下,与未处理试样相比,微凹坑密度为1.5%、2.5%、5.0%时试样的自腐蚀电位分别向正移21、40、56 m V,自腐蚀电流分别减少了92.22%、92.09%、94.05%。在实验密度范围内,微凹坑密度越高,AZ31B镁合金表面的抗腐蚀性能越好。
基金Supported by National Natural Science Foundation of China(Grant Nos.51305168,51375211,51375213)Jiangsu Provincial Natural Science Foundation of China(Grant No.BK20130524)Research Foundation for Advanced Talents of Jiangsu University,China(Grant No.13JDG090)
文摘Surface texturing has been applied to improving the tribological performance of mechanical components for many years. Currently, the researches simulate the film pressure distribution of textured rough surfaces on the basis of the average flow model, and however the influence of roughness on the film pressure distribution could not be precisely expressed. Therefore, in order to study the hydrodynamic lubrication of the rough textured surfaces, sinusoidal waves are employed to characterize untextured surfaces. A deterministic model for hydrodynamic lubrication of microdimple textured rough surfaces is developed to predict the distribution of hydrodynamic pressure. By supplementing with the JFO cavitation boundary, the load carrying capacity of the film produced by micro-dimples and roughness is obtained. And the geometric parameters of textured rough surface are optimized to obtain the maximum hydrodynamic lubrication by specifying an optimization goal of the load carrying capacity. The effect of roughness on the hydrodynamic pressure of surface texture is significant and the load carrying capacity decreases with the increase of the roughness ratio because the roughness greatly suppresses the hydrodynamic effect of dimples. It shows that the roughness ratio of surface may be as small as possible to suppress the effect of hydrodynamic lubrication. Additionally,there are the optimum values of the micro-dimple depth and area density to maximize the load carrying capacity for any given value of the roughness ratio. The proposed approach is capable of accurately reflects the influence of roughness on the hydrodynamic pressure, and developed a deterministic model to investigate the hydrodynamic lubrication of textured surfaces.
