Particle entrapment and indentation process in rolling bearings

2016 ◽  
Vol 230 (12) ◽  
pp. 1572-1587 ◽  
Author(s):  
Guillermo E Morales Espejel ◽  
Antonio Gabelli
Keyword(s):  
Laboratory Experiments ◽  
Particle Trajectory ◽  
Contact Model ◽  
Engineering Model ◽  
Particle Deformation ◽  
Rolling Bearings ◽  
Indentation Process ◽  
Particle Entrapment ◽  
Single Contact ◽  
Good Agreement

In this paper, a complete engineering model for particle entrapment in rolling bearings and consequences in raceway indentations is presented. The attention is focussed on the conditions for particle entrapment once the particles are in contact with the two rolling surfaces. After the entrapment, the model follows the particle trajectory within the contact. The particle deformation is then calculated and finally an elastic-plastic contact model is applied to simulate the eventual raceway indentation. Laboratory experiments with a single contact device as well as full bearing tests were performed to validate the models. The comparisons between model and experiments show good agreement in the number and type of indentations.

3D Numerical Simulation and PEPT Experimental Investigation of Pressurized Gas-Solid Fluidized Bed Hydrodynamic

2009 ◽  
Author(s):  
P. Fede ◽  
G. Moula ◽  
A. Ingram ◽  
T. Dumas ◽  
O. Simonin
Keyword(s):  
Numerical Model ◽  
Fluidized Bed ◽  
Particle Velocity ◽  
Particle Trajectory ◽  
Wall Region ◽  
3 Dimensional ◽  
The Core ◽  
Numerical Predictions ◽  
Model Predictions ◽  
Good Agreement

The present paper is dedicated to numerical and experimental study of the hydrodynamic of a non-reactive isothermal pressurized fluidized bed. Experimental data have been obtained using PEPT technique allowing to track a particle trajectory inside a dense fluidized bed. A specific post-processing approach has been developed to compute the Eulerian time-averaged particle velocity field. The comparison with 3-dimensional numerical model predictions shows a good agreement in the core of the fluidized bed. In contrast, in the near wall region the numerical model overestimate the downward particle velocity. The modification of particle phase wall boundary condition improves the numerical predictions.

Stribeck Curve for Starved Line Contacts

2006 ◽  
Vol 129 (1) ◽  
pp. 181-187 ◽  
Author(s):  
I. C. Faraon ◽  
D. J. Schipper
Keyword(s):  
Film Thickness ◽  
Layer Thickness ◽  
Boundary Lubrication ◽  
Numerical Data ◽  
Contact Model ◽  
Stribeck Curve ◽  
Lubrication Regime ◽  
Straight Line ◽  
Line Contacts ◽  
Good Agreement

This paper discusses a mixed lubrication model in order to predict the Stribeck curve for starved lubricated line contacts. This model is based on a combination of the contact model of Greenwood and Williamson and the elastohydrodynamic (EHL) film thickness for starved line contacts. The starved solution to be implemented in the EHL component is obtained by using numerical data of Wolveridge, who computed the starved film thickness for smooth line contacts. Calculations are presented for different oil supply layer thickness over roughness values (hoil∕σs). For values of the oil layer thickness over roughness ratio larger than approximately 6, the Stribeck curve and separation between the rough surfaces do not change compared to the fully flooded situation. If the oil layer thickness over roughness ratio is in the range of 6 down to 0.7, friction starts to increase and the film thickness decreases. When the oil layer thickness over roughness ratio is less than approximately 0.7, the Stribeck curve tends to transform into a straight line and separation stays at the same value as in the boundary lubrication regime. Comparison between measurements and calculations is made and a good agreement is found.

Friction Model of Thin Solid Film Lubrication

1996 ◽  
Vol 118 (3) ◽  
pp. 693-697 ◽  
Author(s):  
Xianhua Zhang ◽  
Koji Kato
Keyword(s):  
Friction Model ◽  
Thin Solid Film ◽  
Contact Model ◽  
Solid Lubrication ◽  
Practical Application ◽  
Physical Essence ◽  
Solid Film ◽  
Theoretical Results ◽  
Film Lubrication ◽  
Good Agreement

Based upon previous results for thin solid film lubrication, a contact model has been proposed which can describe the physical essence of the steady-state friction condition. By using this contact model, a theoretical calculation method has been established. Good agreement between theoretical results and experimental results obtained for tribo-coatings shows that this theory can be used for practical application to obtain and maintain good solid lubrication.

scholarly journals Creep Slump in Glacier Reservoirs—Theory and Experiment

1981 ◽  
Vol 27 (97) ◽  
pp. 393-406 ◽  
Author(s):  
E. M. Shoemaker
Keyword(s):  
Cycle Time ◽  
Large Amplitude ◽  
Laboratory Experiments ◽  
Yukon Territory ◽  
Wave Profile ◽  
Material Flows ◽  
Cold Surge ◽  
Trapridge Glacier ◽  
Theory And Experiment ◽  
Good Agreement

AbstractFrequently the reservoir region of a cold surge-type glacier has a temperate base, while in a region surrounding the reservoir the base is cold. We analyse the slump process in such a reservoir region— that is, the process whereby material flows toward the lower end of the region and forms a critical wave profile there. The model agrees qualitatively with observations of Trapridge Glacier, Yukon Territory, Canada, which is currently experiencing a critical pre-surge condition. Calculations based on the model give good agreement with the surge cycle time of Rusty Glacier, Yukon Territory. Laboratory experiments show that a large-amplitude slump-induced wave profile forms prior to a surge. Experimental surges were produced with velocity increases of order one hundred.

Relative contact width evaluation of end hemispherical cavities rollers as an indication of Hertzian contact pressure

2021 ◽  
pp. 095440622110616
Author(s):  
Paresh C Chhotani ◽  
DP Vakharia ◽  
AA Shaikh
Keyword(s):  
Fatigue Life ◽  
Film Thickness ◽  
Contact Stresses ◽  
Hertzian Contact ◽  
Life Aspect ◽  
Rolling Bearings ◽  
Contact Width ◽  
Simulation Results ◽  
Experimental Trials ◽  
Good Agreement

In a recent investigation, the end hemispherical cavities (EHC) rollers exhibited better strength against fracture than hollow rollers. Furthermore, EHC rollers looked promising from a higher fatigue life aspect than conventional solid rollers in a simulation study. Therefore, it necessitated further exploration of the EHC roller concept and to this end, in the present investigation, the contact widths of EHC rollers were relatively evaluated to judge its contact stresses' behavior with respect to the solid roller because the contact stresses are responsible for the fatigue life of rolling bearings. In the experiments, the contact footprints were obtained by forcing specimens of rollers against chemically etched surfaces and were examined by a microscope for measurement of contact widths. The experimental trials were performed with individual roller-on-plate tests and also with full-bearing samples. The etch correction factor was used to correct anomalies of real and observed contact widths due to etching film thickness. The parabolic relationships were established for roller variants which yielded constants signifying their relative ranks. The contact semi-widths, thus derived from corrected experimental results of individual roller-on-plate tests, demonstrated good agreement (<5%) with those derived from simulation results. The results of full-bearing sample tests for roller variants also ranked same as individual roller-on-plate tests. The encouraging results of contact semi-width assuredly favor the prospects of relatively higher fatigue life in case of EHC rollers.

Particle Trajectories in a Gas Centrifuge

1961 ◽  
Vol 83 (3) ◽  
pp. 333-339 ◽  
Author(s):  
A. R. Kriebel
Keyword(s):  
Particle Size ◽  
Flow Model ◽  
Particle Trajectory ◽  
Size Range ◽  
Reynolds Numbers ◽  
Spherical Particles ◽  
Injection Velocity ◽  
Gas Centrifuge ◽  
Particle Size Analyzer ◽  
Good Agreement

The motion of spherical particles injected into a cylinder of gas which rotates as a solid body has been studied. The particle trajectory is expressed explicitly as a function of two dimensionless parameters; an injection-velocity parameter and an inertial parameter which is roughly the ratio of centrifugal force to drag force on the particle. The main results are the dependence on particle size of the time for particles to be centrifuged and of deposition angle. These results indicate performance limitations for an idealized cyclone separator and a centrifugal particle-size analyzer. Experimental data are presented for an air centrifuge which was designed to approximate the analytical flow model. Reasonably good agreement with theoretically predicted deposition angles was found for spherical glass beads and irregularly shaped chalk crystals, even to Reynolds numbers in excess of the Stokes flow regime for which the analysis applies. Particles as small as 2 microns may be classified with the present centrifuge configuration; however, by modification it might be used to classify particles in the submicron-size range.

scholarly journals Efficient mixing in stratified flows: experimental study of a Rayleigh–Taylor unstable interface within an otherwise stable stratification

2014 ◽  
Vol 756 ◽  
pp. 1027-1057 ◽  
Author(s):  
Megan S. Davies Wykes ◽  
Stuart B. Dalziel
Keyword(s):  
Turbulent Mixing ◽  
Laboratory Experiments ◽  
Functional Form ◽  
Salt Water ◽  
Stable Stratification ◽  
Mixing Efficiency ◽  
Final States ◽  
Density Profiles ◽  
Rayleigh Taylor Instability ◽  
Good Agreement

AbstractBoussinesq salt-water laboratory experiments of Rayleigh–Taylor instability (RTI) can achieve mixing efficiencies greater than 0.75 when the unstable interface is confined between two stable stratifications. This is much greater than that found when RTI occurs between two homogeneous layers when the mixing efficiency has been found to approach 0.5. Here, the mixing efficiency is defined as the ratio of energy used in mixing compared with the energy available for mixing. If the initial and final states are quiescent then the mixing efficiency can be calculated from experiments by comparison of the corresponding density profiles. Varying the functional form of the confining stratifications has a strong effect on the mixing efficiency. We derive a buoyancy-diffusion model for the rate of growth of the turbulent mixing region, $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}\dot{h} = 2 \sqrt{\alpha A g h}$ (where $A = A(h)$ is the Atwood number across the mixing region when it extends a height $h$, $g$ is acceleration due to gravity and $\alpha $ is a constant). This model shows good agreement with experiments when the value of the constant $\alpha $ is set to 0.07, the value found in experiments of RTI between two homogeneous layers (where the height of the turbulent mixing region increases as $h =\alpha A g t^2$, an expression which is equivalent to that derived for $\dot{h}$).

Hydraulic control of continuously stratified flow over an obstacle

2012 ◽  
Vol 700 ◽  
pp. 502-513 ◽  
Author(s):  
Kraig B. Winters ◽  
Laurence Armi
Keyword(s):  
Laboratory Experiments ◽  
Single Layer ◽  
Stratified Flow ◽  
Depth Range ◽  
Hydraulic Control ◽  
Reduced Gravity ◽  
Flow Properties ◽  
Flow Past A Cylinder ◽  
Over The Top ◽  
Good Agreement

AbstractMotivated by the laboratory experiments of Browand & Winant (Geophys. Fluid Dyn., vol. 4, 1972, pp. 29–53), a series of two-dimensional numerical simulations of flow past a cylinder of diameter $d$ are run for different values of the approach Froude number ${\mathit{Fr}}_{o} = U/ Nd$ between $0. 02$ and $0. 2$ at $\mathit{Re}= O(100)$. The observed flow is characterized by blocking and upstream influence in front of the cylinder and by relatively thin, fast jets over the top and bottom of the cylinder. This continuously stratified flow can be understood in terms of an inviscid non-diffusive integral inertia–buoyancy balance reminiscent of reduced-gravity single-layer hydraulics, but one where the reduced gravity is coupled to the thickness of the jets. The proposed theoretical framework describes the flow upstream of the obstacle and at its crest. The most important elements of the theory are the inclusion of upstream influence in the form of blocked flow within an energetically constrained depth range and the recognition that the flow well above and well below the active, accelerated layers is dynamically uncoupled. These constraints determine, through continuity, the transport in the accelerated layers. Combining these results with the observation that the flow is asymmetric around the cylinder, i.e. hydraulically controlled, allows us to determine the active layer thicknesses, the effective reduced gravity and thus all of the integral flow properties of the fast layers in good agreement with the numerically computed flows.

Nanoindentation of a Deformable Substrate Covered by Patterned Nanodot Asperities

2009 ◽  
Author(s):  
Hengyu Wang ◽  
Min Zou ◽  
Robert L. Jackson ◽  
Preston R. Larson ◽  
Matthew B. Johnson
Keyword(s):  
Silicon Substrate ◽  
Experimental Studies ◽  
Indentation Load ◽  
Spherical Indenter ◽  
Experimental Results ◽  
Contact Model ◽  
Asperity Contact ◽  
Deformation Relationship ◽  
Repetitive Pattern ◽  
Good Agreement

This paper presents numerical and experimental studies of nanoindentation of a silicon substrate covered by patterned Ni nanodot asperities. A multi-asperity contact model was developed in this study to simulate the contact between a spherical indenter and the Ni nanodot asperities. In this model, the silicon substrate is considered to be deformable and the nanodots are allowed to interact with each other through the deformation of the substrate. The load-deformation relationship predicted by the model was found to be in good agreement with the experimental results. This model can also be used to predict indentation load-deformation relationships of a deformable substrate covered by nanodots with known size and location distributions, but not necessarily following a repetitive pattern.

Laboratory experiments on counter-propagating collisions of solitary waves. Part 1. Wave interactions

2014 ◽  
Vol 749 ◽  
pp. 577-596 ◽  
Author(s):  
Yongshuai Chen ◽  
Harry Yeh
Keyword(s):  
Solitary Waves ◽  
Water Surface ◽  
Laboratory Experiments ◽  
Wave Amplitude ◽  
Relative Reduction ◽  
Wave Interactions ◽  
Oblique Collision ◽  
Laboratory Results ◽  
Surface Profiles ◽  
Good Agreement

AbstractCollisions of counter-propagating solitary waves are investigated experimentally. Precision measurements of water-surface profiles are made with the use of the laser induced fluorescence (LIF) technique. During the collision, the maximum wave amplitude exceeds that calculated by the superposition of the incident solitary waves, and agrees well with both the asymptotic prediction of Su & Mirie (J. Fluid Mech., vol. 98, 1980, pp. 509–525) and the numerical simulation of Craig et al. (Phys. Fluids, vol. 18, 2006, 057106). The collision causes attenuation in wave amplitude: the larger the wave, the greater the relative reduction in amplitude. The collision also leaves imprints on the interacting waves with phase shifts and small dispersive trailing waves. Maxworthy’s (J. Fluid Mech., vol. 76, 1976, pp. 177–185) experimental results show that the phase shift is independent of incident wave amplitude. On the contrary, our laboratory results exhibit the dependence of wave amplitude that is in support of Su & Mirie’s theory. Though the dispersive trailing waves are very small and transient, the measured amplitude and wavelength are in good agreement with Su & Mirie’s theory. Furthermore, we investigate the symmetric head-on collision of the highest waves possible in our laboratory. Our laboratory results show that the runup and rundown of the collision are not simple reversible processes. The rundown motion causes penetration of the water surface below the still-water level. This penetration causes the post-collision waveform to be asymmetric, with each departing wave tilting slightly backward with respect to the direction of its propagation; the penetration is also the origin of the secondary dispersive trailing wavetrain. The present work extends the studies of head-on collisions to oblique collisions. The theory of Su & Mirie, which was developed only for head-on collisions, predicts well in oblique collision cases, which suggests that the obliqueness of the collision may not be important for this ‘weak’ interaction process.

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