Study On Tribological Performances Of The Bionic Water-Lubricated Bearing Based On Diatom Shell Structure

A diatom is a single-celled autotrophic microorganism, which is widely distributed in the marine environment and water environment. It is found that the diatom has usually the refined multilevel porous structure having high tensile property and elasticity toughness, and good mechanical performances. However, few researches have been made on the tribological performances of these structures. Based on simulating the multilevel porous structure for Coscinodiscus sp., the present thesis picks out a new type of compound dimple structure, and applies the structure to the water-lubricated bearing to improve its tribological performances.The present work is sponsored by the National Natural Science Foundation of China(No: 51375509), which is named as “Investigation of tribological performances for water-lubricated bearing using representative shell structures of diatoms”. The present thesis includes the following contents:Firstly, the cultural method for the diatom is introduced, and then typical diatoms, are cultured with a set of diatom cultivation device invented by the present research group. The images and surface topography are captured by ZEISS AURIGA double beam scanning electron microscopy. The author’s observation reveals that the coscinodiscus sp. shell is characterized by the refined multi-level porous structure.Secondly, based on the bionic multilevel porous of the coscinodiscus sp. shell, tribological performances for the varied bionic structure, i.e., compound dimples are studied with the fluid-structure interaction method(FSI). The numerical results show that compared with the simple dimple, the compound dimples have more advantages in improving the tribological performances of the lubricated parallel surfaces, among which the rectangular-spherical dimple shows the best improvement.Further, the rectangular-spherical dimple is applied to the low pressure region of the water-lubricated bearing. Then tribological performances, such as the load-carrying capacity, frictional force and friction coefficient, for the bearing with the compound dimple at the varied geometry size, are solved with the FSI method, and compared those with the simple dimpled bearing and smooth bearing. The numerical results show that the compound dimple at the low pressure region can significantly improve the tribological performances of the dimpled bearing in comparison with the smooth bearing. Owing to the large bearing clearance at the low pressure region, however, the compound dimple does not show an obvious advantage in improving the tribological performances compared with the simple dimple.Beside this, the rectangular-spherical dimple is applied to the high pressure region of the water-lubricated bearing. Then the effects of some influencing factors, such as the dimple geometry size, dimple interval between the closely neighboring compound dimples, shaft speed and its eccentricity, length-diameter ratio of bearing, viscosity and density of the lubricant, on tribological performances for the bearing, are studied with the FSI method. The numerical results show that the compound dimple at the high pressure region has an obvious advantage in improving the tribological performances in comparison with the smooth bearing and simple dimpled bearing. At the small dimple interval, small eccentricity ratio, large length-diameter ratio, or high rotating speed, the above improvement becomes more obvious.