Yonghong Fu

Influence of Geometric Shapes on the Hydrodynamic Lubrication of a Partially Textured Slider With Micro-Grooves

The effect of partial surface texturing in the form of parabolic grooves, rectangular grooves, and triangular grooves on the hydrodynamic pressure is investigated in the present work. The dimensionless hydrodynamic pressure generated by the partial surface texturing is obtained by the multigrid method. The effect of the texturing parameters on the dimensionless average pressure is analyzed for a given set of operating parameters. The results indicate that the geometric shape, area density, groove depth, and orientation of the grooves have an obvious influence on the hydrodynamic pressure. However, the groove width has little effect on the dimensionless average pressure. The results of the present work demonstrate that surface texturing design is very important to generate additional hydrodynamic pressure according to the operating parameters of the mechanical components. [DOI: 10.1115/1.4027633]

The Influence of Partially Textured Slider with Oriented Parabolic Grooves on the Behavior of Hydrodynamic Lubrication

An analytical model is developed to investigate a partially textured slider of infinite width with orientation parabolic grooves. The generating mechanism for hydrodynamic lubrication of the partial surface texturing in the sliding surface is similar to that of a step slider. By using the multigrid method, the hydrodynamic pressure generated by the partial surface texturing is obtained. The surface texturing parameters are numerically optimized to obtain maximum hydrodynamic effect in terms of the dimensionless average pressure for a given set of operating parameters. The results indicate that parameters such as groove orientation angle, depth, area density, and textured fraction have an obvious influence on the hydrodynamic pressure for partial surface texturing. However, the groove width has little or no effect on the dimensionless average pressure. The results of the study show that the hydrodynamic lubrication performance can be ameliorated by optimizing the surface texturing according to the operating parameters of the mechanical components.

The influence of partially textured slider with orientation ellipse dimples on the behavior of hydrodynamic lubrication

Purpose – The purpose of this paper is to investigate a partially textured slider of infinite width with orientation ellipse dimples in liquid application. Design/methodology/approach – In this paper, the pressure distribution of lubrication between a partially textured slider and a smooth sliding slider is calculated by the multi-grid method. For the same dimple area, the influence of the ellipse dimple with geometric parameters, and distribution and orientation on the hydrodynamic lubrication is evaluated in terms of the dimensionless average pressure for a given set of operating parameters. Findings – In the present work, the magnitude of the dimensionless average pressure seems proportional to the slender ratio. Consequently, the slender ratio may be chosen as large as possible based on fabrication techniques. The longer axes of ellipse dimples placed parallel to the direction of sliding always show the better hydrodynamic effect. Furthermore, the results show that the ellipse dimples can greatly impr...

Hydrodynamic Lubrication of Conformal Contacting Surfaces With Parabolic Grooves

The effect of surface texturing in the form of parabolic grooves on the hydrodynamic lubrication properties is investigated in this paper. Numerical simulation of the pressure distribution of lubricant between a textured slider and a smooth, moving slider has been performed. The evaluation criterion of hydrodynamic effect of dimensionless average pressure is calculated and presented with the variation of minimum film thickness, groove width, groove depth, spacing and orientation angle. Optimum values of geometrical parameters such as the dimensionless groove depth, spacing and orientation angle are obtained which correspond to maximum average pressure. It is also noted that the average pressure increases monotonically with increasing groove width. The results show that the hydrodynamic effect can be improved by employing optimized surface texturing design.

Tribological Properties of Laser Microtextured Surface Bonded With Composite Solid Lubricant at High Temperature

A combination technology of the solid lubricant and the laser surface texturing (LST) can significantly improve the tribological properties of friction pairs. The plate sample was textured by fiber laser and composite lubricant of polyimide (PI) and molybdenum disulfide (MoS2) powders were filled in the microdimples. Sliding friction performances of micron-sized composite lubricant and nano-sized composite lubricant were investigated by ring-plate tribometer at temperatures ranging from room temperature (RT) to 400u2009°C. On the one hand, the results of the micron-sized composite lubricant show that the friction coefficient of the textured surface filled with composite lubricant (TS) exhibits the lowest level and the highest stability compared to a textured surface without solid lubrication, smooth surface without lubrication, smooth surface burnished with a layer of composite solid lubricant. The better dimple density range is 35-46%. The friction coefficients of the sample surface filled with micron-composite solid lubricant with the texture density of 35% are maintained at a low level (about 0.1) at temperatures ranging from RT to 300u2009°C. On the other hand, the results of the nano-sized composite lubricant show that these friction properties are better than those of MoS2-PI micron-sized composite. The friction coefficients of MoS2-PI-CNTs nano-sized composite solid lubricant are lower than those of the MoS2-PI composite lubricant at temperatures ranging from RT to 400u2009°C. In addition, the possible mechanisms involving the synergetic effect of the surface texture and the solid lubricant are discussed in the present work.

Characterisation of group behaviour surface texturing with multi-layers fitting method

Abstract Surface texturing was widely applied in improving the tribological properties of mechanical components, but study of measurement of this technology was still insufficient. This study proposed the multi-layers fitting (MLF) method to characterise the dimples array texture surface. Based on the synergistic effect among the dimples, the 3D morphology of texture surface was rebuilt by 2D stylus profiler in the MLF method. The feasible regions of texture patterns and sensitive parameters were confirmed by non-linear programming, and the processing software of MLF method was developed based on the Matlab®. The characterisation parameters system of dimples was defined mathematically, and the accuracy of MLF method was investigated by comparison experiment. The surface texture specimens were made by laser surface texturing technology, in which high consistency of dimples’ size and distribution was achieved. Then, 2D profiles of different dimples were captured by employing Hommel-T1000 stylus profiler, and the data were further processed by MLF software to rebuild 3D morphology of single dimple. The experiment results indicated that the MLF characterisation results were similar to those of Wyko T1100, the white light interference microscope. It was also found that the stability of MLF characterisation results highly depended on the number of captured cross-sections.

Effect of Elliptical Dimples on Hydrodynamic Lubrication

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.

Characteristic of Laser Texturing Surface Aided with Abbott Curve

Laser surface texturing improved tribological property is regarded as an optimistic method. However, many technological parameters have crisscross effects on surface topographies, the complexity of relations between variables devoted to a tough way to express functions accurately. Meanwhile, enough basic tents of theory can be borrowed to interruption for obtained the expectation in the process of micro-texturing on critical surfaces. And thus pumping current and number of laser pulse were chosen and studied for improving the surface topographies realized by Nd3+: YAG laser, assisting a better expectation of reduction of abrasive grains. The single-factor method was exerted in the process of analysis, one international 3D-morphology meter and its accessory codes were adopted before the analysis of constitutive influence from pumping current and pulse times in given duration on characteristic parameters of texturing surface, the results are shown in figures by Abbott curve and characteristic parameters which were compared in the literate.

Influence of Micro Trapezoidal-Groove on Behavior of Sliding Tribopairs

The effect of various micro isosceles-trapezoid grooves on improvement of tribological performance is discussed. It is accomplished through the CFD-approach where the momentum and continuity equations are solved separately, one of low Reynolds turbulence models-Abid index and SIMPLE algorithm in theory of Control Volume Method are adopted. For different width and depth of micro isosceles-trapezoid grooves, the load supporting capacity of oil-film are compared. The results show that the widths has more influence than the depths on hydrodynamic lubrication, and relative parameters change monotonously with the depth of micro-groove. The effect of texturing arc-grooves on improvement of tribological properties is conspicuous if w1 = 40μm, w2 = 10μm and hp = 10μm for micro isosceles-trapezoid grooves.

Micro-Machining the Surface of Metallic Workpiece by Pulsed YAG Laser

It is a challenge to apply micromachining to the metal surface by conventional YAG laser. In this article, several experiments have been carried out to use micromachining on the surface of metallic specimen by frequency doubled Nd: YAG laser pumped by semiconductor. The mechanism of laser micromachining and the selective laser power, pulse duration, repetition frequency, scanning velocity and supplementing gas have been extensively studied and analyzed. The experimental results indicate that if the main technological parameters have been generally considered and optimized, positive quality of surface machining can be obtained.