Cong Shen

Bio: Cong Shen is an academic researcher from Louisiana State University. The author has contributed to research in topics: Lubrication & Dimple. The author has an hindex of 12, co-authored 18 publications receiving 494 citations. Previous affiliations of Cong Shen include Chongqing University & Nanjing University of Aeronautics and Astronautics.

Effect of Dimple’s Internal Structure on Hydrodynamic Lubrication

Abstract: An experimental and numerical study of the lubrication effectiveness of textured surfaces with dimples possessing an internal structure is presented. A fabrication method to create dimples with different profiles is described. Thrust bearing-like specimens are textured with dimples of three different internal structural shapes: rectangle (R), oblique triangle (T1) and isosceles triangle (T2). The load-carrying capacity test results show that the dimple internal structure has a profound influence on the load-carrying capacity. Specifically, cylindrical dimples with rectangular cross-sectional shape produce more load-carrying capacity than those with triangular profile. Also, presented are the results of a mass-conservative algorithm that predicts the performances of dimples with different internal structural shapes. The simulation results indicate that the higher load-carrying capacity produced by the cylindrical dimple is due to the better pressure building capacity as a result of the converging step shape.

Study on the Ferrofluid Lubrication with an External Magnetic Field

Abstract: Ferrofluids (FFs) are stable colloidal systems consisting of single-domain magnetic particles with a diameter of approximately 10 nm coated with surfactants and dispersed in a carrier liquid. By applying an external magnetic field, these fluids can be confined, positioned, shaped and, controlled at desired places. The load capacity of a lubricant film of FF can also be increased with an appropriate magnetic field. In this paper, Fe3O4-based FFs with different saturation magnetizations (M s) were prepared by the co-precipitation technique. The tribological experiments of FFs under different magnets distributions were conducted on a ring-on-cylinder tribometer. The results show that the magnetic field intensity distributions on the rubbing surface have a significant influence on the tribological properties of FFs. The experimental results also indicate that FFs have a good friction-reduction performance in the presence of an external magnetic field compared with the carrier liquid and that its lifetime of friction can be greatly improved.

Texture Shape Optimization for Seal-Like Parallel Surfaces: Theory and Experiment

Abstract: The geometric shape of surface textures has a major influence on the tribological performance of textured surfaces. This study aims to improve the tribological performance of seal-like specimens with a circular ring configuration by introducing novel texture geometries that generate the highest load-carrying capacity (LCC). A numerical optimization approach is presented to determine the optimum texture shapes for a ring geometry with different constraints on the textured area. The results show that the optimum textures of different area ratios (ARs) have similar chevron shapes with flat fronts. Also presented are the tribological test results of the optimum texture shape (AR = 20%) and their comparison with three regular shapes. It is found that the optimum texture shape provides the lowest friction coefficient under different test conditions.

On the Magnitude of Cavitation Pressure of Steady-State Lubrication

Abstract: The value of cavitation pressure plays an important role in the implementation of the mass-conservative algorithm. This is particularly crucial in applications that deal with analysis of surface textures. In this paper, published research on cavitation of journal bearing and surface textures are reviewed, and experiments and simulations of textured surface are conducted in order to gain insight into the choice of cavitation pressure for steady-state lubrication. Contrary to the common assertion that cavitation pressure is close to the ambient pressure, both experiments with journal bearings and simulations of surface textures indicate that low cavitation pressure around 30 kPa is possible. Research reveals that the cavitation pressure in steady-state lubrication is affected by the supply of gas dissolved in the oil film. The results of a series of experiments involving the load-carrying capacity of a textured parallel thrust bearing are presented. The comparison between theoretical and experimental results confirms that the value of cavitation pressure could vary depending on the operating conditions.

Recent progress in ferrofluids research: novel applications of magnetically controllable and tunable fluids

Abstract: Ferrofluids are suspensions of magnetic nanoparticles that have the attractive feature of being controlled by applied magnetic fields. Ferrofluids have been studied for decades in an ever growing number of applications that take advantage of their response to applied magnetic fields. Here, we provide a summary of recent advances in established and emerging applications of ferrofluids, including applications in optics, sensors, actuators, seals, lubrication, and static/dynamic magnetically driven assembly of structures.

Recent development on surface texturing in enhancing tribological performance of bearing sliders

Abstract: Surface texturing is a surface modification approach, resulting in an improvement in tribological performance such as friction and wear resistance. Surface texturing can be performed either as a protruded or recessed asperity, with the latter being more popular due to advantages in terms of micro-lubrication and ease of manufacturing. There are a number of ways of material preparation for surface texturing, with the laser surface texturing being the most popular because of its flexibility and high accuracy. The performance of textured surface depends on the geometrical characteristics of the surface texture and the operating condition of the bearing components. In hydrodynamic and mixed lubrication, microcavity in negative surface texture acts as a reservoir for fluid lubricant, while in boundary lubrication, it traps wear particles to reduce further abrasion. In the past, tremendous amount of research effort has been put into the study of surface texturing, with an aim to investigate the underlying effect of surface texturing on tribological performance. This paper presents a critical review of research and development on surface texturing over the past decades, highlighting design, optimization and fabrication of surface texture, and their effects on tribological performance in terms of friction and load bearing capacity under different lubrication regimes. Numerical modelling approaches involving Reynolds and Navier–Stokes equations employed to understand and determine the tribological behaviour are discussed and compared with respect to experimental investigations. Thin film coatings on textured surface have been found to be a promising means to further reduce friction and increase wear life.

Performance of the self-lubricating textured tools in dry cutting of Ti-6Al-4V

Abstract: Surface textures were made using laser on the rake or flank face of the cemented carbide (WC/Co) inserts. Molybdenum disulfide solid lubricants were filled into the textured grooves to form self-lubricating textured tools. Dry cutting tests on Ti-6Al-4V were carried out with these self-lubricating textured tools and conventional tool. The machining performance was assessed in terms of the cutting forces, cutting temperature, chip thickness ratio, friction coefficient at the tool–chip interface, and tool wear. Results show that the cutting forces and cutting temperature of the self-lubricating textured tools were reduced compared with that of the conventional tool. The application of the self-lubricating textured tool with elliptical grooves on its rake face can reduce the tool–chip friction coefficient and the chip thickness ratio. The tool life of the textured tools is improved compared with that of the conventional tool. The effectiveness of the self-lubricating textured tools in improving cutting performance is related to the cutting parameter.