| WANG Shijin,LIU Chenglong,GUO Feng,ZHANG Jianjun,ZHU Kongmin.Effect of Grid Array Wettability Surface on Lubricating Film Formation Characteristics under Pure Sliding Condition[J],54(5):93-105 |
| Effect of Grid Array Wettability Surface on Lubricating Film Formation Characteristics under Pure Sliding Condition |
| Received:March 26, 2024 Revised:June 06, 2024 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2025.05.007 |
| KeyWord:limited oil supply grid array wettability pure sliding oil replenishment oil film dimple friction coefficient lubrication efficiency |
| Author | Institution |
| WANG Shijin |
School of Mechanical and Automotive Engineering, Qingdao University of Technology, Shandong Qingdao , China |
| LIU Chenglong |
School of Mechanical and Automotive Engineering, Qingdao University of Technology, Shandong Qingdao , China |
| GUO Feng |
School of Mechanical and Automotive Engineering, Qingdao University of Technology, Shandong Qingdao , China |
| ZHANG Jianjun |
School of Mechanical and Automotive Engineering, Qingdao University of Technology, Shandong Qingdao , China |
| ZHU Kongmin |
Zhichuang Future Science and Technology Development Co., Ltd., Shandong Liaocheng , China |
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| Abstract: |
| This study aims to utilize a Grid Array Wettability (GAW) surface to construct discrete oil pools, to enhance the oil replenishment, lubrication properties and load-carrying capacity of the friction pair under pure sliding (ηSRR=2). Using femtosecond laser etching, a grid-like oleophobic coating surface was prepared to investigate the effect of this grid-like surface on the lubrication state under limited lubricant supply. Using high-viscosity polyisobutylene lubricant under pure sliding conditions, the characteristics of forming oil dimple films were investigated to study the control effect of the GAW surface on oil film morphology. Through analysis of oil pool shape and film thickness, it was found that the GAW surface (30-300 μm) exhibited excellent oil replenishment efficiency compared with the original surface and expanded the starvation boundary distance under limited oil supply. Different grid sizes had varying effects on dimple and minimum film thickness. The OS surface, without undergoing chemical modification, had the lowest contact angle and was in the Wenzel wetted state. Oil pools tended to spread on the OS surface, and under the sliding action of the steel ball, they tended to separate from the center line. The contact angles of oil droplets on the AFC and GAW surfaces were relatively similar. Consequently, both surfaces could impede the spreading of oil pools. Under limited oil supply, as the grid size increased, the dimple film thickness gradually decreased, while the minimum film thickness showed a trend of initially increasing and then decreasing. When the grid size was 200 μm, as the dimple film thickness decreased, the minimum film thickness significantly increased. Among them, the small grid array wettability surface had the optimal oil replenishment and the dimple film thickness was more pronounced. The smaller the grid width (w) and spacing (d) were, the more pronounced anti-wetting characteristics of the friction pair surface became. As the grid size increased, the slippage area reduced and the degree of oil starvation increased, which could lead to a weakening of the oil film dimple behavior. The increased spacing between discrete oil pools and the decreased height of the oil pools resulted in reduced merging ability of the oil pools at the inlet, resulting in a deteriorated oil supply condition. As the grid size increased, the dimpled oil film formed at the inlet of the contact area gradually transitioned from a spindle-shaped to an elliptical shape. Experiments show that the grid wettability surface can effectively reduce the friction coefficient. At 150 mm/s, the optimal size (200 μm) GAW surface can reduce the friction coefficient of 35.9% than the original surface. The GAW surface increases the specific surface area and height of the oil pools on surfaces, increasing the probability of contact between the steel ball and the oil pools. The optimized grid array surface makes the oil distribute orderly, increasing the height of oil pools per unit volume. It also improves the lubricant supply condition at the inlet of the contact area, enhancing lubrication efficiency. As a result, under pure sliding condition, utilizing the optimized grid wettability surface can effectively reduce the accumulation of lubricant due to the thermal effect, take full advantage of surface slip properties, enhance replenishment, facilitate lubricating film formation, and reduce friction losses. |
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