Simulation Calculation of Friction Factor of the End Face for Mechanical Seals Based on Fractal Theory

2014 ◽  
Vol 687-691 ◽  
pp. 142-147 ◽  
Author(s):  
Long Wei ◽  
Peng Gao Zhang ◽  
Gui Fang Fang
Keyword(s):  
Liquid Film ◽  
Surface Topography ◽  
Friction Factor ◽  
Fractal Theory ◽  
Fluid Pressure ◽  
Fractal Model ◽  
Contact Friction ◽  
Mechanical Seals ◽  
Viscous Shear Stress ◽  
Viscous Shear

In order to study the effects of operating parameters and surface topography on friction factors between the end faces for mechanical seals, a friction factor fractal model between end faces for contact mechanical seals was established based on the contact fractal model and the average film thickness fractal model, adopting fractal parameters to represent surface topography, separating friction into viscous shear friction of liquid film and contact friction of asperities, and representing the effect of actual rough surface on viscous shear stress of liquid film by introducing the contact factor. The influencing factors of friction factor for B104a-70 mechanical seal were analyzed by simulating. Results showed that the friction factor between the surfaces increases with the increases of spring pressure when the end faces are coarser, while the friction factor decreases slightly with the increases of spring pressure when the end faces are smoother. The friction factor between the faces decreases with the increases of the sealed fluid pressure, which increases approximate linearly with the increases of rotating speed, and it increases with the increases of fractal dimension of end faces and the decreases of the characteristic scale factor.

A normal contact stiffness model of machined joint surfaces considering elastic, elasto-plastic and plastic factors

2019 ◽  
Vol 234 (7) ◽  
pp. 1007-1016 ◽  
Author(s):  
Yongquan Zhang ◽  
Hong Lu ◽  
Xinbao Zhang ◽  
He Ling ◽  
Wei Fan ◽  
...  
Keyword(s):  
Surface Topography ◽  
Contact Stiffness ◽  
Fractal Theory ◽  
Fractal Model ◽  
Single Pair ◽  
Machined Surface ◽  
Normal Contact ◽  
Joint Surfaces ◽  
Stiffness Model ◽  
Normal Contact Stiffness

Considering the rough surface as a fractal model makes the research of contact parameters more practical. In the fractal model of the machined surface, the parameters describing the surface topography are independent of the measurement resolution. Based on the elastic, elasto-plastic and plastic deformations of a single pair of contact asperities, a normal contact stiffness model using the fractal model for surface topography description is proposed in this paper. The specimens machined by milling and grinding methods are used to verify the proposed contact stiffness model based on the fractal theory. The experimental and theoretical results indicate that the proposed contact stiffness model is appropriate for the machined joint surfaces.

Liquid Film Performance Analysis of the Mechanical Seals with a Laser-Textured Micro-Pore Face

2010 ◽  
Vol 139-141 ◽  
pp. 418-421
Author(s):  
Xin Qi Yu ◽  
Qing Gang Liu ◽  
Hui Qin Gao ◽  
Jia Hui Yu
Keyword(s):  
Liquid Film ◽  
Parametric Analysis ◽  
Fluid Pressure ◽  
Diameter Ratio ◽  
Hydrodynamic Effect ◽  
Mechanical Seals ◽  
Film Pressure ◽  
Pressure Profiles ◽  
Pore Area ◽  
The Finite Difference Method

A theoretical model has been developed for the mechanical seals with a laser-textured porous seal face. By means of variable dimensionless steps, parametric analysis has been performed to obtain dimensionless liquid film pressure by the finite difference method. Liquid film pressure profiles over the pore column have be achieved by the computer program MATLAB. It is found from calculating results that average liquid film pressure increases with increase of the rotational speed, liquid viscosity and reduction of liquid film thickness. Hydrodynamic effect produced by micro-pores decreases with increase of fluid pressure. In addition, the effect of the pore area density and depth over diameter ratio on the liquid film pressure is very significant. Optimum values of these parameters can maximize the average liquid film pressure.

A NOVEL FRACTAL SOLUTION FOR LAMINAR FLOW RESISTANCE IN ROUGHENED CYLINDRICAL MICROCHANNELS

Fractals ◽  
2020 ◽  
Vol 28 (06) ◽  
pp. 2050097
Author(s):  
BOQI XIAO ◽  
YONGHUI LIU ◽  
HANXIN CHEN ◽  
XUBING CHEN ◽  
GONGBO LONG
Keyword(s):  
Laminar Flow ◽  
Friction Factor ◽  
Present Model ◽  
Fractal Theory ◽  
Fractal Model ◽  
Average Height ◽  
Relative Roughness ◽  
Darcy Friction Factor ◽  
Poiseuille Number ◽  
Cylindrical Microchannel

In this work, a novel fractal model for the laminar flow in roughened cylindrical microchannels is proposed. The average height of rough elements is derived using the fractal theory. The effects of relative roughness on the friction factor and the Poiseuille number are discussed. It is found that the Darcy friction factor and the Poiseuille number increase with the increase in the relative roughness in the cylindrical microchannel. Besides, it is observed that the Darcy friction factor decreases with the increase in the Reynolds number. Each parameter of the proposed model has a clear physical meaning. The present model can properly reveal some mechanisms that affect the laminar flow in roughened cylindrical microchannels. The present model improves the understanding of the physical mechanisms of fluid flows through roughened cylindrical microchannels. Our model predictions are compared with the existing experimental data, and good agreement can be found.

Effect of Surface Topography on Average Film Thickness between the End Faces for Mechanical Seal

2014 ◽  
Vol 670-671 ◽  
pp. 860-865
Author(s):  
Long Wei ◽  
Peng Gao Zhang ◽  
Gui Fang Fang
Keyword(s):  
Film Thickness ◽  
Surface Topography ◽  
Great Influence ◽  
Fractal Model ◽  
Mechanical Seal ◽  
Mechanical Seals ◽  
Operating Characteristics ◽  
Fractal Parameters ◽  
Average Film Thickness ◽  
Effect Of Surface

In order to research and master the effect of surface topography on average film thickness between the end faces for mechanical seals, average film thickness fractal model between the end faces for mechanical seal was established using fractal parameters charactering surface topography characteristics, based on contact fractal model of the end face for mechanical seal, and solving micro-void volume. Effect of surface topography fractal parameters on average film thickness between the end faces for B104a-70 mechanical seal was analyzed by theoretical calculation. The results showed that fractal dimension D and characteristic length scale G of the end face had a great influence on the average film thickness h0, and h0 decreased with the increased of D or decreased of G; h0 decreased rapidly with the increased of D or with the decreased of G when the end face was coarser, however, it decreased slowly with the increased of D or with the decreased of G when the end face was smoother. In normal working parameters and surface topography fractal parameters range, average film thickness between end faces was in the range of 0.27~1.7μm. Studying on the effect of the change of surface topography on average film thickness has an important significance on the predicting of operating characteristics of end faces during actual operating and the design of end faces for contact mechanical seal.

scholarly journals Shear models and parametric analysis of the PVC geomembrane-cushion interface in a high rock-fill dam

PLoS ONE ◽  
2021 ◽  
Vol 16 (1) ◽  
pp. e0245245
Author(s):  
Yun-Feng Liu ◽  
Ke Gu ◽  
Yi-Ming Shu ◽  
Xian-Lei Zhang ◽  
Xin-Xin Liu ◽  
...  
Keyword(s):  
Shear Stress ◽  
Friction Coefficient ◽  
Three Dimensional ◽  
Viscous Friction ◽  
Hydraulic Pressure ◽  
Viscous Shear Stress ◽  
Box Counting ◽  
Viscous Shear ◽  
The Stability ◽  
Hysteresis Friction

As a type of flexible impermeable material, a PVC geomembrane must be cooperatively used with cushion materials. The contact interface between a PVC geomembrane and cushion easily loses stability. In this present paper, we analyzed the shear models and parameters of the interface to study the stability. Two different cushion materials were used: the common extrusion sidewall and non-fines concrete. To simulate real working conditions, flexible silicone cushions were added under the loading plates to simulate hydraulic pressure loading, and the loading effect of flexible silicone cushions was demonstrated by measuring the actual contact areas under different normal pressures between the geomembrane and cushion using the thin-film pressure sensor. According to elastomer shear stress, there are two main types of shear stress between the PVC geomembrane and the cushion: viscous shear stress and hysteresis shear stress. The viscous shear stress between the geomembrane and the cement grout was measured using a dry, smooth concrete sample, then the precise formula parameters of the viscous shear stress and viscous friction coefficient were obtained. The hysteresis shear stress between the geomembrane and the cushion was calculated by subtracting the viscous shear stress from the total shear stress. The formula parameters of the hysteresis shear stress and hysteresis friction coefficient were calculated. The three-dimensional box-counting dimensions of the cushion surface were calculated, and the formula parameters of the hysteresis friction were positively correlated with the three-dimensional box dimensions.

Normal Contact Stiffness Fractal Geometric Model Based on the Gamma Distribution of Rough Joint Surface

2013 ◽  
Vol 760-762 ◽  
pp. 2064-2067 ◽  
Author(s):  
Jing Fang Shen ◽  
Ke Xiang Wu ◽  
Fei Yang
Keyword(s):  
Convex Body ◽  
Gamma Distribution ◽  
Contact Stiffness ◽  
Geometric Model ◽  
Fractal Theory ◽  
Fractal Model ◽  
Joint Surface ◽  
Engineering Practice ◽  
Normal Contact ◽  
Normal Contact Stiffness

In this article, according to WenShuHua and Zhangxueniang fractal model, we point out the deficiency. Based on the fractal theory and Zhang, Wens contact stiffness fractal model, this paper puts forward Gamma distribution of rough joint surface normal contact stiffness. This paper considers micro convex body for ellipsoid, contact area for elliptic. This is slightly convex body for sphere hypothesis is more close to the actual situation. At the same time by using statistics theory, considering the contact ellipse long, short axis a and b are greater than zero, the assumption of a and b to two-dimensional Gamma distribution, it is more suitable for engineering practice.

scholarly journals Assessment of the Shear Strength of Pile-to-Soil Interfaces Based on Pile Surface Topography Using Laser Scanning

Sensors ◽  
2019 ◽  
Vol 19 (5) ◽  
pp. 1012 ◽  
Author(s):  
Zbigniew Muszyński ◽  
Marek Wyjadłowski
Keyword(s):  
Shear Strength ◽  
Surface Topography ◽  
Friction Factor ◽  
Laser Scanning ◽  
Least Squares Method ◽  
Soil Layer ◽  
Side Surface ◽  
Sample Height ◽  
Functional Volume

This article presents in situ research on the side surface of continuous flight auger (CFA) foundation piles using a three-dimensional (3D) laser scanner (Leica ScanStation C10) in order to evaluate the morphology assessment of pile concrete surfaces in various geotechnical layers. Terrestrial laser scanning describes the 3D geometry of the construction with high spatial resolution and accuracy. A total of six areas were selected from the acquired point cloud for which a two-step approach for removing the form was applied. In the first step, the reference surface was fitted using the least squares method, and then, cylindrical projection of the surface was performed. In the second step, an operator of removal of the multi-plane form was applied. For each sample, height parameters (Sq, Ssk, Sku, Sp, Sv, Sz, Sa) and functional volume parameters (Vmp, Vmc, Vvc, Vvv) according to the standard ISO 25178-2:2012 were determined. Significant differences in the values of surface height and functional volume parameters were observed for each geotechnical layer where piles were formed. Because the piles remain embedded in the ground, in situ tests of the side surface of piles are rarely performed and taken into account in the assessment of pile bearing capacity. The study of surface topography is a crucial stage in the assessment of the shear strength at the interface between a concrete pile and the soil layer. The obtained concrete morphology assessments are applicable during the determination of the skin friction factor in the analytical or numerical estimation of pile shaft resistance. The proposed procedure of morphology evaluation may improve the fidelity of the assumed friction factor between the concrete and soil and increase the reliability of direct shear experiments.

COMPRESSIVE STRENGTH OF FRACTAL-TEXTURED FOAMED CONCRETE

Fractals ◽  
2019 ◽  
Vol 27 (01) ◽  
pp. 1940003 ◽  
Author(s):  
Y. CHEN ◽  
Y. F. XU
Keyword(s):  
Compressive Strength ◽  
Fractal Dimension ◽  
Porous Structure ◽  
Fractal Theory ◽  
Scaling Law ◽  
Weight Ratio ◽  
High Strength ◽  
Labor Cost ◽  
Fractal Model ◽  
Foamed Concrete

Foamed concrete possesses characteristics such as high strength-to-weight ratio and low density, and widely used to reduce dead loads on the structure and foundation, contributes to energy conservation, and lowers the labor cost during construction. In this paper, the objective is to propose prediction relation for the compressive strength of foamed concrete by fractal theory. A theoretical relation was derived for the compressive strength relating to porosity based on the fractal model for foamed concrete. The proposed relation stands out compared to empirical model since it employs easily measurable parameter, the fractal dimension of porous structure in foamed concrete. The fractal dimension of porous structure can be calculated from the scaling law of the compressive strength of foamed concrete. The fractal model for porous structure serves as a simple and effective tool for predicting the compressive strength of foamed concrete because of its ease in application. The prediction relation of the compressive strength developed in this paper is found to match well with the measured strength.

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