Paper 6: Assessment of Face Seal Performance Based on the Parameters of a Statistical Representation of Surface Roughness

1967 ◽  
Vol 182 (11) ◽  
pp. 101-107 ◽  
Author(s):  
L. A. Mitchell ◽  
M. D. Rowe
Keyword(s):  
Surface Roughness ◽  
Standard Deviation ◽  
Surface Profile ◽  
Real Surface ◽  
Face Seal ◽  
Statistical Representation ◽  
Adequate Information ◽  
Centre Line ◽  
Sealing Performance ◽  
The Mean

Most methods commonly used to describe real surface roughness do not provide adequate information to enable predictions to be made of fluid leakage between two surfaces. To carry out such an analysis it is essential to know the depths of the remaining valleys at all stages of compression. It is shown that, when the distributions of peak and valley levels are defined, load-compression and load-leakage relationships can be derived if wedge-shaped asperities of constant apex semi-angle are assumed. The results suggest that a convenient quantity for specifying the form of a surface profile is the ratio of the distance between the mean peak and mean valley levels to the standard deviation of the distributions ( d/σ). For the best sealing performance d/σ should be as large as possible, whilst the centre-line average (c.l.a.), which provides a measure of the scale of the roughness, should be as small as possible.

Effects of Surface Roughness and Slip Flow on the Performance of a Spiral Groove Gas Face Seal

2007 ◽  
Author(s):  
Xu-Dong Peng ◽  
Song-En Sheng ◽  
Xiao-Ni Yin ◽  
Ji-Yun Li
Keyword(s):  
Surface Roughness ◽  
Standard Deviation ◽  
Slip Flow ◽  
Element Model ◽  
Face Seal ◽  
Spiral Groove ◽  
Sealing Performance ◽  
Set Up ◽  
Gas Face Seal ◽  
Effect Of Surface

Considering the effects of surface roughness and slip flow, the extended Reynolds equation presented by Makino et al [1] is used to set up the finite element model for a non-contact spiral groove dry gas face seal (S-DGS). The analyses for a typical S-DGS at low speed (≤ 500 rpm) and low pressure (≤ 0.606 MPa) showed that the effect of slip flow on the sealing performance is significant for 0.05≤ Kn < 1.0, where Kn refers to the Knudsen number, but the effect of surface roughness on the sealing performance varies with the different areas of both the two faces. When the standard deviation of composite roughness is less than 1.0 micron and in the range of 0.5≤ Kn≤ 1.0, the effects of surface roughness and slip flow diminished on gas film stiffness and frictional work but are still significant on the leakage rate. The effect of surface roughness of the spiral groove bottom is significant and should be considered, but the effects of the other surface roughness, i.e. the soft ring surface roughness and the un-grooved hard ring surface roughness, are negligible only when the value of the standard deviation of composite roughness meets with API standards.

Hydrodynamic Lubrication and Wear in Wavy Contacting Face Seals

1978 ◽  
Vol 100 (1) ◽  
pp. 81-90 ◽  
Author(s):  
A. O. Lebeck ◽  
J. L. Teale ◽  
R. E. Pierce
Keyword(s):  
Surface Roughness ◽  
Hydrodynamic Lubrication ◽  
Surface Profile ◽  
Operating Conditions ◽  
Face Seal ◽  
Hydrodynamic Load ◽  
Surface Waviness ◽  
Wear Rates ◽  
Elastic Deflection ◽  
Face Seals

A model of face seal lubrication is proposed and developed. Hydrodynamic lubrication for rough surfaces, surface waviness, asperity load support, elastic deflection, and wear are considered in the model. Predictions of the ratio of hydrodynamic load support to asperity load support are made for a face seal sealing a low viscosity liquid where some contact does occur and surface roughness is important. The hydrodynamic lubrication is caused by circumferential surface waviness on the seal faces. Waviness is caused by initial out of flatness or any of the various distortions that occur on seal ring faces in operation. The equilibrium solution to the problem yields one dimensional hydrodynamic and asperity pressure distributions, mean film thickness, elastic deflection, and friction for a given load on the seal faces. The solution is found numerically. It is shown that the fraction of hydrodynamic load support depends on many parameters including the waviness amplitude, number of waves around the seal, face width, ring stiffness, and most importantly, surface roughness. For the particular seal examined the fraction of load support would be small for the amount of waviness expected in this seal. However, if the surface roughness were lower, almost complete lift-off is possible. The results of the analysis show why the initial friction and wear rates in mechanical face seals may vary widely; the fraction of hydrodynamic load support depends on the roughness and waviness which are not necessarily controlled. Finally, it is shown how such initial waviness effects disappear as the surface profile is altered by wear. This may take a long or short time, depending on the initial amount of hydrodynamic load support, but unless complete liftoff is achieved under all operating conditions, the effects of initial waviness will vanish in time for steady state conditions. Practical implications are drawn for selecting some seal parameters to enhance initial hydrodynamic load support without causing significant leakage.

Surface Topography Changes in Polymer-Metal Sliding—II

1983 ◽  
Vol 105 (4) ◽  
pp. 526-531 ◽  
Author(s):  
V. K. Jain ◽  
S. Bahadur
Keyword(s):  
Surface Roughness ◽  
Standard Deviation ◽  
High Density Polyethylene ◽  
Surface Profile ◽  
Data Acquisition System ◽  
Radius Of Curvature ◽  
Roughness Parameters ◽  
Poly Vinyl Chloride ◽  
Polymer Metal

The variation in the surface topographical parameters for the case of sliding between high density polyethylene and poly(vinyl chloride) pin ends and a steel disk periphery was investigated. Sliding surface profile ordinate data were obtained at 2μm intervals using a data acquisition system, both along and perpendicular to the direction of sliding. A number of surface roughness parameters, viz., the r.m.s. and c.l.a. roughness, the slope, density, and radius of curvature of asperities, the standard deviation and distribution of profile ordinates, slopes, radii of curvatures and heights of asperities were calculated using a Fortran IV computer program. The analysis showed that the surface parameters undergo a marked variation during the early part of sliding, but the variation is statistically insignificant during the later part. It was found that the standard deviation of peak heights can be approximated by the r.m.s. surface roughness.

Effect of Shot Number on Crater Formation of Magnesium Alloy Modified with High-Intensity Pulsed Ion Beam

2012 ◽  
Vol 627 ◽  
pp. 629-632
Author(s):  
Peng Li
Keyword(s):  
Surface Roughness ◽  
Magnesium Alloy ◽  
Ion Beam ◽  
Surface Profile ◽  
Crater Formation ◽  
Shot Number ◽  
The Mean ◽  
Surface Morphologies ◽  
Ion Current Density ◽  
Surface Increase

Abstract. HIPIB irradiation of magnesium alloy is carried out at a specific ion current density of 100 A/cm2 with shot number from one to ten in order to explore the effect of shot number on crater formation of magnesium alloy. Surface morphologies, surface roughness and mean spacing of surface profile irregularities of the irradiated samples are examined by scanning electron microscopy (SEM) and profilometer technique, respectively. It is found that the surface roughness, the mean spacing of surface profile irregularities, and the maximum crater diameter on the irradiated surface increase with increasing shot number, whereas the crater density decreases as the shot number increases.

scholarly journals Experimental verification of a numerical surface roughness model for metallic bodies under large plastic strain

2019 ◽  
Vol 252 ◽  
pp. 05005
Author(s):  
Paweł Sidun
Keyword(s):  
Surface Roughness ◽  
Plastic Strain ◽  
Experimental Verification ◽  
Surface Profile ◽  
Surface Force ◽  
Numerical Calculations ◽  
Real Surface ◽  
Friction Process ◽  
Arithmetic Average ◽  
The Impact

The present work describes selected aspects of numerical modelling of the process of bonding metal alloys with consideration for micro-roughness, as well as experimental verification. The plastic-elastic contact between two deformable bodies was investigated in a DEFROM FEM environment, and verified at the test stand. The present paper demonstrates selected results of contact modelling investigated using aluminium-copper samples, in relation to their elastic-plastic range. The real surface profile helped to create a mathematical model of surface roughness measured using a laser microscope. Dependency between a blade of a tool and a feed was used to build a numerical model of roughness based on the arithmetic average value of the roughness profile. The work presents also a process of simplification of real surface roughness for the needs of numerical calculations. The paper investigates an impact of wave roughness at obtained values on effective plastic strain and stress. Additionally, numerical analysis shows a need to enter a new roughness wave correction factor assuming a zero value of the coefficient of friction. This is due to the interaction of metallic surfaces within the plastic contact zone. The obtained results allow the estimation of the impact of surface force interaction expressed by the wave coefficient factor. The experimental verification of numerical calculations allowed the estimation of the actual impact of the micro-cutting process in the entire friction process. Further analysis of obtained results permits the author to explain the surface phenomena occurring during the friction process, such as adhesion or diffusion, and outline the development direction of numerical methods.

scholarly journals Declines in blood lead concentrations in clinically affected and unaffected cattle accidentally exposed to lead

2011 ◽  
Vol 24 (1) ◽  
pp. 182-187 ◽  
Author(s):  
Karyn Bischoff ◽  
Belinda Thompson ◽  
Hollis N. Erb ◽  
William P. Higgins ◽  
Joseph G. Ebel ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Detection Limit ◽  
Beef Cattle ◽  
Chronic Exposure ◽  
Clinical Signs ◽  
Blood Lead ◽  
Common Cause ◽  
Adequate Information ◽  
The Mean ◽  
Serial Samples

Lead (Pb) poisoning remains a common cause of morbidity in dairy and beef cattle. Although Pb toxicosis is typically diagnosed in cattle with clinical signs of acute or subacute Pb poisoning, it has been hypothesized that subclinical chronic exposure of cattle to Pb, which often goes undiagnosed, poses more of a risk to the human consumer. There is not adequate information on Pb kinetics to determine when or if Pb-exposed cattle can safely enter the food chain. The objectives of the current study were to determine whether subclinical elevations in blood Pb (bPb) were present in cattle from herds where 1 or more individuals had clinical Pb poisoning and to determine the half-life (t1/2) of bPb in Pb-exposed cattle. Samples of blood were collected and analyzed for Pb from 126 cattle from 9 farms. Blood lead concentrations ranged from below the detection limit (2.50 µg/dl) to 423.0 µg/dl. Only 11 of the 94 cattle with detectable bPb had clinical signs such as diarrhea, blindness, bruxism, or seizures. When possible, cattle with detectable bPb had serial samples taken. The mean t1/2 calculated from 44 serially sampled cattle was 135 days (standard deviation: 125 days, range: 3–577 days). A source of Pb on the farm was determined for all but one herd.

Surface Roughness Effects on Fluid Flow between Two Rotating Cylinders

2015 ◽  
Vol 642 ◽  
pp. 275-280
Author(s):  
Sutthinan Srirattayawong ◽  
Shian Gao
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Reynolds Equation ◽  
Surface Profile ◽  
Fluid Film ◽  
Real Surface ◽  
Contact Center ◽  
Roughness Effects ◽  
Fluid Film Thickness ◽  
Lubricant Viscosity

In general, the thin fluid film problems are explained by the classical Reynolds equation, but this approach has some limitations. To overcome them, the method of Computational Fluid Dynamics (CFD) is used in this study, as an alternative to solving the Reynolds equation. The characteristics of the two cylinders contact with real surface roughness are investigated. The CFD model has been used to simulate the behavior of the fluid flows at the conjunction between two different radius cylinders. The non-Newtonian fluid is employed to calculate the lubricant viscosity, and the thermal effect is also considered in the evaluation of the lubricant properties. The pressure distributions, the fluid film thickness and the temperature distributions are investigated. The obtained results show clearly the significance of the surface roughness on the lubricant flow at the contact center area. The fluctuated flow also affects the pressure distribution, the temperature and the lubricant viscosity in a similar pattern to the rough surface profile. The surface roughness effect will decrease when the film thickness is increased.

Influence of the height distribution of microscopic surface roughness on photometric estimates of the standard deviation from the surface profile

1995 ◽  
Vol 38 (8) ◽  
pp. 880-883
Author(s):  
V. V. Syt'ko ◽  
D. V. Dem'yanenko ◽  
Yu. N. Sviridenko ◽  
N. I. Aleshkevich ◽  
V. F. Sholokh
Keyword(s):  
Surface Roughness ◽  
Standard Deviation ◽  
Surface Profile ◽  
Height Distribution ◽  
Microscopic Surface

scholarly journals Fractal analysis for biosurface comparison and behaviour prediction

2009 ◽  
Vol 63 (3) ◽  
pp. 239-245 ◽  
Author(s):  
Bozica Bojovic ◽  
Zoran Miljkovic ◽  
Bojan Babic ◽  
Djuro Koruga
Keyword(s):  
Surface Roughness ◽  
Fractal Dimension ◽  
Fractal Analysis ◽  
Surface Profile ◽  
Scanning Probe ◽  
Real Surface ◽  
Behavior Prediction ◽  
Functional Behavior ◽  
Probe Microscope ◽  
The Given

Fractal analysis was used in previous authors' researches for characterizations of grinded ceramics surface textures by surface profile fractal dimension. In this paper the 'skyscrapers' method was chosen for calculating fractal dimension of surface, using the image processing toolbox, as well as a custom-developed algorithm of Matlab environment. This method entails recording the surface as an image, by using a scanning probe microscope. In the given contact lens case, fractal dimension values confirm changes of the surface roughness during the cleaning and wearing processes. Examination of real surface roughness could provide comparison and functional behavior prediction.

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