A Theory of Hydrodynamic Friction Forces in Starved Point Contact Considering Cavitation

1974 ◽  
Vol 96 (2) ◽  
pp. 237-245 ◽  
Author(s):  
Y. P. Chiu
Keyword(s):  
Fluid Layer ◽  
Point Contact ◽  
Rolling Friction ◽  
Rigid Bodies ◽  
Variable Degree ◽  
Hydrodynamic Friction ◽  
Friction Forces ◽  
Viscosity Parameter

Expressions for the hydrodynamic friction forces between two rigid bodies each having two principal radii of curvature have been found using an exponential pressure-viscosity assumptions. The rolling friction forces are presented graphically in terms of a dimensionless meniscus distance. These formulas are applicable to the computation of the rolling friction in a ball-race contact and in a ball-cage contact with a variable degree of starvation. In particular, the rolling friction forces can be predicted as a function of the usual speed-viscosity parameter and the thickness of the inlet fluid layer far upstream of the inlet.

Peristaltic thrusting of a thermal-viscosity nanofluid through a resilient vertical pipe

2020 ◽  
Vol 75 (8) ◽  
pp. 727-738 ◽  
Author(s):  
Ramzy M. Abumandour ◽  
Islam M. Eldesoky ◽  
Mohamed H. Kamel ◽  
Mohamed M. Ahmed ◽  
Sara I. Abdelsalam
Keyword(s):  
Pressure Gradient ◽  
Hartmann Number ◽  
Amplitude Ratio ◽  
Variable Viscosity ◽  
Friction Forces ◽  
Long Wavelength ◽  
Viscosity Parameter ◽  
Long Wavelength Approximation ◽  
Wavelength Approximation ◽  
Theoretical Results

AbstractIn the article, the effects of the thermal viscosity and magnetohydrodynamic on the peristalsis of nanofluid are analyzed. The dominant neutralization is deduced through long wavelength approximation. The analytical solution of velocity and temperature is extracted by using steady perturbation. The pressure gradient and friction forces are obtained. Numerical results are calculated and contrasted with the debated theoretical results. These results are calculated for various values of Hartmann number, variable viscosity parameter and amplitude ratio. It is observed that the pressure gradient is reduced with an increase in the thermal viscosity parameter and that the Hartmann number enhances the pressure difference.

scholarly journals Considerations on finding the rolling and spinning friction coefficients

2018 ◽  
Vol 184 ◽  
pp. 01009
Author(s):  
Florina-Carmen Ciornei ◽  
Stelian Alaci ◽  
Sorinel-Toderas Siretean ◽  
Mariana-Catalina Ciornei ◽  
Ioan-Bogdan Dragoi ◽  
...  
Keyword(s):  
Power Law ◽  
Normal Force ◽  
Point Contact ◽  
Rolling Friction ◽  
Friction Torque ◽  
Complex Motion ◽  
Inclined Plane ◽  
Friction Coefficients ◽  
Detailed Procedure ◽  
Tilting Angle

The complex motion from a point contact has as consequence the occurrence of a friction torsor within both spinning and rolling friction exist. Additionally, recent researches showed that the two friction moments, spinning and rolling torques, are not proportional to the normal force. Here, the power law dependency is accepted and therefore, besides the coefficients of spinning and rolling friction, the exponents from the relations friction torque-normal force should be first determined. The paper proposes as method for finding the four parameters the use of the inclined plane principle. The acceleration of a revolution body in descending motion on the inclined plane is found for four different values of the tilting angle and a system of four equations is obtained. The detailed procedure of finding the solutions of the system is presented in the present paper.

Oil Film Thickness and Rolling Friction in Elastohydrodynamic Point Contact

1971 ◽  
Vol 93 (3) ◽  
pp. 371-379 ◽  
Author(s):  
R. Gohar
Keyword(s):  
Film Thickness ◽  
Tungsten Carbide ◽  
Material Properties ◽  
High Pressures ◽  
Glass Plate ◽  
Point Contact ◽  
Rolling Friction ◽  
Significant Alteration ◽  
Oil Film ◽  
Rolling Ball

The effect of material properties upon the film thickness in elastohydrodynamic point contact is demonstrated with a rolling ball and plate machine. A 220 fold range of Young’s modulus is employed and a maximum Hertzian pressure of 5 × 105 lb f/in2 is reached. The oil film, which is measured by interferometry, shows no significant alteration at such high pressures, and is also fairly insensitive to the choice of bounding materials. Using a technique similar to that employed by Crook, the rolling friction between a tungsten carbide and a glass plate is found and compared with theory. The effect of spin is investigated and found to be slight.

scholarly journals Analytical substantiation of constructive parameters of rotating field board of plow’s body

2019 ◽  
Vol 126 ◽  
pp. 00038
Author(s):  
Vladimir Konovalov ◽  
Sergey Konovalov ◽  
Victoria Igumnova
Keyword(s):  
Sliding Friction ◽  
Rolling Friction ◽  
High Energy ◽  
Cultivated Plants ◽  
Friction Forces ◽  
Technical Parameters ◽  
Cutting Resistance ◽  
Different Depths ◽  
Analytical Relations ◽  
Rotating Field

The article shows importance of use of dump plowing for formation and maintenance of soil structure and pest control and diseases of cultivated plants. A significant drawback of plowing process is indicated, which is its high energy intensity. To reduce energy consumption, it is proposed to use rotating field boards, which allow replacing sliding friction forces with rolling friction forces. The article presents a description of design of plow’s body with rotating field board and notes that without a preliminary analytical study and justification of initial parameters, their use may not be effective. Analytical relations connecting value of radius of rotating field of board, rate of collapse of soil, allowable value of indentation of field board into soil and specific force of cutting resistance of soil that ability to use it for baseline technical parameters. To analyze obtained dependence, the article presents its graphical solution. The authors obtained an expression for determining the value of arm’s force of reference reaction from soil to balance a plow’s body, in addition, this indicator can be used to adjust a body when working on soils with different physical and mechanical parameters and at different depths.

Basic Optimization Methodology for the Design of Friction Damping in Blade Shrouds

2013 ◽  
Author(s):  
Michal Hajžman ◽  
Luděk Pešek ◽  
Jan Brůha ◽  
Vladimír Zeman ◽  
Drahomír Rychecký
Keyword(s):  
Vibration Suppression ◽  
Harmonic Balance Method ◽  
Rigid Bodies ◽  
Geometrical Parameters ◽  
Bending Vibration ◽  
Friction Forces ◽  
Normal Contact ◽  
Friction Element ◽  
Experimental Stand ◽  
Optimization Methodology

This paper is focused on the optimization of friction element parameters in blade shrouds for various types of excitation. In order to create and validate a proper modelling methodology an experimental stand and a numerical simulation of blades interaction by means of a friction element placed in the shrouds were prepared. Mathematical models are based on the finite element method combined with rigid bodies. The interaction of the friction element and blades is described by normal contact and tangential friction forces derived for particular geometrical parameters of the studied mechanical system. The models can be analyzed both in frequency domain (by the harmonic balance method) or in time domain (by the numerical integration). The results of the optimization of friction element parameters with respect to the bending vibration suppression are documented in the paper. Another contact modelling approach intended for more complex contact surfaces is based on the decomposition of a contact surface into a set of elementary areas and on the expression of contact and friction forces between these areas. All methodologies are implemented in the MATLAB system and the results for the chosen test cases are compared with the results obtained by a measurement or by the ANSYS software.

CHAIN ROTATIONAL DYNAMICS IN MR SUSPENSIONS

2002 ◽  
Vol 16 (17n18) ◽  
pp. 2293-2299 ◽  
Author(s):  
SONIA MELLE ◽  
OSCAR G. CALDERÓN ◽  
MIGUEL A. RUBIO ◽  
GERALD G. FULLER
Keyword(s):  
Power Law ◽  
Rotating Magnetic Fields ◽  
Hydrodynamic Friction ◽  
Friction Forces ◽  
Number Ratio ◽  
Mason Number ◽  
Dynamics Simulations ◽  
Average Size ◽  
The Magnetic Field ◽  
Good Agreement

The dynamics of induced dipolar chains in magnetorhelogical suspensions subject to rotating magnetic fields has been experimentally studied combining scattering dichroism and video microscopy experiments. When a rotating field is imposed the chainlike aggregates rotate synchronously with the magnetic field. We found that the average size of the aggregates decreases with Mason number (ratio of viscous to magnetic forces) following a power law with exponent -0.5 being the hydrodynamic friction forces the cause of the chains break up. However the total number of aggregated particles shows two different behaviors depending on Mason number. For low Mason numbers, the total number of aggregated particles remains almost constant and above a critical Mason number, the rotation of the field prevents the particle aggregation process from taking place so the number of aggregated particles decreases with Mason number following a power law behavior with exponent -1. Athermal molecular dynamics simulations are also reported, showing good agreement with the experiments.

Test Rig for Extraction of the Contact Parameters for Plane on Plane Contact

2012 ◽  
Author(s):  
D. Botto ◽  
M. Lavella ◽  
M. M. Gola
Keyword(s):  
Contact Area ◽  
Contact Stiffness ◽  
Point Contact ◽  
Real Plane ◽  
Operational Environment ◽  
Test Rig ◽  
Friction Forces ◽  
Plane Contact ◽  
Wide Range ◽  
Contact Parameters

The modelling of the friction interfaces has received much attention in recent years from the aerospace industry. In order to obtain reliable prediction of the nonlinear dynamic behaviour of the disc and blades in the aerospace engine the friction forces at interfaces, such as in under-platform dampers, blade and fir tree roots or shrouds, must be modelled accurately. Two contact parameters, namely the contact stiffness and the coefficient of friction, are sufficient to model, with good accuracy, the friction contact. The contact parameters are obtained experimentally, and are of interest for the designer only if representative of the operational environment of the engine. To pursue this aim a test rig has been designed to perform experiments in a wide range of temperatures, with different combinations of normal and tangential load, frequencies and mating materials, representative of the real operating condition of the engine. Most of the rigs found in literature perform most likely point contact even if the two bodies have plane mating surfaces. The design of a real plane-on-plane contact test rig is not an easy task but despite the difficulty a solution was found in the design shown in this work. The core of the rig is a tilting mechanism enabling one surface to lies down on the other so that the plane-on-plane contact is achieved, at least within the flatness geometrical tolerance of the surfaces. The results of the experiments are the hysteresis loops, namely the tangential contact force against the relative displacement, from which the contact parameters can be calculated. Measurements of displacements are taken very close to the actual contact area and are performed by means of two laser interferometers. Localized heating is achieved by means of an induction heating machine while a thermocouple measures the temperature at points close to the contact area.

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