Formulas for Entraining Velocity in Lubricated Line Contacts

2002 ◽  
Vol 124 (4) ◽  
pp. 856-858
Author(s):  
Enrico Ciulli
Keyword(s):  
Relative Motion ◽  
Physical Meaning ◽  
Point Of View ◽  
Lubricated Contacts ◽  
Line Contacts ◽  
Two Bodies

The knowledge of the entraining velocity is necessary for the investigation of lubricated contacts. The entraining velocity is the average of the surface velocities of the two bodies in contact relative to the contact itself; its estimation can be actually not always immediate. In this work the general case of two pairing cylindrical surfaces in planar relative motion is analyzed from a kinematical point of view. Formulas for the evaluation of the entraining velocity are presented that are directly applicable to any case of connected members of a mechanism. The physical meaning of the terms of the proposed formulas is also briefly investigated from a lubrication point of view.

Application of Dry-Friction Whip and Whirl Solution Methods to Systems With Support Asymmetry

2018 ◽  
Author(s):  
Jason C. Wilkes
Keyword(s):  
Relative Motion ◽  
General Model ◽  
Dry Friction ◽  
Current Work ◽  
General Sense ◽  
Continuous Contact ◽  
Solution Methods ◽  
Asymmetric Rotor ◽  
Two Bodies

Dry-friction whip and whirl occurs when a rotor contacts a stator across a clearance annulus. In a general sense, the relative motion between the two bodies is described by a circular precessing motion. While this problem is generally well understood, the author is unaware of any papers that discuss the problem for systems having asymmetric rotor or stator supports. The current work will investigate a general model to describe dry-friction whip and whirl for the case of continuous contact between a rotor and stator in the presence of asymmetry. This paper will show that for light asymmetry, the rotor and stator motions are elliptical; however, the relative motion between the two bodies remains circular.

Electron Pairing and Chemical Bonds. Physical Meaning of Effective Pairs

1994 ◽  
Vol 59 (12) ◽  
pp. 2567-2578 ◽  
Author(s):  
Robert Ponec ◽  
Filip Uhlík
Keyword(s):  
Density Distribution ◽  
Electron Density ◽  
Physical Meaning ◽  
Electron Density Distribution ◽  
Mutual Coupling ◽  
Population Analysis ◽  
Point Of View ◽  
Chemical Bonds ◽  
Conditional Probabilities ◽  
Electron Pairing

The physical meaning of the so-called effective pairs which have been introduced recently within the formalism of pair population analysis is discussed using the analysis of conditional probabilities of electron density distribution for electron 1 with the reference electron fixed in a certain point 2. It is demonstrated that from the point of view of the mutual coupling of electron motions, the effective pairs behave analogously to singlet pairs. Based on this finding, effective pairs can be interpreted as the fraction of singlet pairs that is directly involved in bonding.

Anomalous Behavior of Heterogeneous Materials at Microwaves Frequencies: Introduction to Fractional Derivatives in Electromagnetism

1990 ◽  
Vol 189 ◽  
Author(s):  
F. Heliodore ◽  
D. Cottevieille ◽  
A. Le Mehaute
Keyword(s):  
Electromagnetic Wave ◽  
Physical Meaning ◽  
Fractional Derivatives ◽  
Heterogeneous Media ◽  
Present Note ◽  
Heterogeneous Materials ◽  
Anomalous Behavior ◽  
Point Of View ◽  
Unique Point ◽  
Validity Range

ABSTRACTThe present note introduces new trends in electromagnetic spectroscopy in complex media.When an electromagnetic wave propagates in heterogeneous media, some questions arise about both physical meaning and validity range of the traditional analysis. The aim of our advanced research is related to the generalisation of Maxwell's equations able todescribe both homogeneous and heterogeneous media from an unique point of view.

The Problem of Relativity in reference to several bodies

1926 ◽  
Vol 23 (3) ◽  
pp. 191-197
Author(s):  
R. Hargreaves
Keyword(s):  
Relative Motion ◽  
Point Of View ◽  
Image Position ◽  
Primary Form

§ 1. If the kinetic potential for the relative motion of two masses is written with an added constant asa close connexion with the relativity quadratic appears. The latter is in factwhere a modification of the primary formwhich shows an unaltered determinant. The condition in respect to the determinant, suggested, I believe, by Schwarzschild, is one which to me appears to give the most significant form to the results. From the dynamical standpoint we may regard it as imposing a counterpoise in the inertia coefficients to the modification introduced by the potential; or from a geometrical point of view we may regard it as minimizing the departure from the normal use of coordinates. An illuminating example of the loss of meaning that accompanies transformation in which this condition is disregarded is furnished by the isotropic form which is sometimes given to Einstein's quadratic.

An Original Setup Test Rig for Analysing Lubricated Contact Under Dynamic Normal Excitation Forces

2003 ◽  
Author(s):  
Toufiq El Kilali ◽  
Joe¨l Perret-Liaudet ◽  
Denis Mazuyer
Keyword(s):  
Dynamic Behaviour ◽  
Natural Frequencies ◽  
Normal Load ◽  
Point Of View ◽  
Test Rig ◽  
Dynamic Excitation ◽  
Lubricated Contacts ◽  
Lubricated Contact ◽  
Set Up ◽  
New Machine

This paper concerns a new experimental set-up based on an optical EHL machine fitted with a dynamic excitation system. The test rig has been built and presented in this paper. Apparatus design derives from two previously defined experimental test rig. With this new machine, we can study the dynamic behaviour of lubricated contacts under sliding conditions on the both tribological and dynamical point of view. It allows to measure the oil film thickness and to visualise the lubricated dynamically loaded contact under sliding condition. It allows also to measure the dynamic response (acceleration) of the loaded contact under harmonic or random external normal load excitation superimposed on a static one. Capabilities of the apparatus are given in this paper. In particular, theoretical and experimental results concerning the system natural frequencies.

Wave-Energy Conversion Through Relative Motion Between Two Single-Mode Oscillating Bodies

1999 ◽  
Vol 121 (1) ◽  
pp. 32-38 ◽  
Author(s):  
J. Falnes
Keyword(s):  
Energy Conversion ◽  
Relative Motion ◽  
Wave Energy ◽  
Load Force ◽  
Wave Forces ◽  
Equivalent System ◽  
Wave Excitation ◽  
Excitation Force ◽  
Two Bodies ◽  
Wave Excitation Force

Wave-energy converters (WECs) need a reaction source against which the wave forces can react. As with shore-based WECs, sometimes also floating WECs react against a fixed point on the seabed. Alternatively, for a floating WEC, force reaction may be obtained by utilizing the relative motion between two bodies. A load force for energy conversion is assumed to be applied only to this relative motion. It is assumed that either body oscillates in one mode only (mostly, the heave mode is considered here). The system, if assumed to be linear, is proved to be phenomenologically equivalent to a one-mode, one-body system, for which the wave excitation force equals the force which is necessary to apply between the two bodies in order to ensure that they are oscillating with zero relative motion. It is discussed how this equivalent excitation force and also the intrinsic mechanical impedance of the equivalent system depend on the mechanical impedances for the two separate bodies, including the radiation impedance matrix (which combines radiation resistances and added masses). The equivalent system is applied for discussing optimum performance for maximizing the absorbed wave energy. It is shown that, for an axisymmetric system utilizing heave modes, it is possible to absorb an energy amounting to the incident wave power on a crest length which equals the wavelength divided by 2π, even though the power take-off is applied to the relative motion only. Moreover, it is shown that it is possible to obtain an equivalent excitation force which exceeds the wave excitation force on either body.

Uniform Equations in the Inlet and Exit Zones of Heavily Loaded Point and Line Elastohydrodynamically Lubricated Contacts Involved in Various Steady Motions

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Ilya I. Kudish
Keyword(s):  
Film Thickness ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Point Contacts ◽  
Lubrication Film ◽  
Lubricated Contacts ◽  
Asymptotic Equations ◽  
Line Contacts ◽  
Steady Motions ◽  
Numerical Approaches

Heavily loaded point elastohydrodynamically lubricated (EHL) contacts involved in steady purely transitional, skewed transitional, and transitional with spinning motions are considered. It is shown that in the central parts of the inlet and exit zones of such heavily loaded point EHL contacts the asymptotic equations governing the EHL problem along the lubricant flow streamlines for the above types of contact motions can be reduced to two sets of asymptotic equations: one in the inlet and one in the exit zones. The latter sets of equations are identical to the asymptotic equations describing lubrication process in the inlet and exit zones of the corresponding heavily loaded line EHL contact (Kudish, I. I., 2013, Elastohydrodynamic Lubrication for Line and Point Contacts: Asymptotic and Numerical Approaches, Chapman and Hall/CRC). For each specific motion of a point contact, a separate set of formulas for the lubrication film thickness is obtained. For different types of contact motions, these film thickness formulas differ significantly (Kudish, I. I., 2013, Elastohydrodynamic Lubrication for Line and Point Contacts: Asymptotic and Numerical Approaches, Chapman and Hall/CRC). For heavily loaded contacts, the discovered relationship between point and line EHL problems allows to apply to point contacts most of the results obtained for line contacts (Kudish, I. I., 2013, Elastohydrodynamic Lubrication for Line and Point Contacts: Asymptotic and Numerical Approaches, Chapman and Hall/CRC; Kudish, I. I., and Covitch, M. J., 2010, Modeling and Analytical Methods in Tribology, Chapman and Hall/CRC).

scholarly journals A Control System For Constrained Wave-Powered Oceanographic Buoys

2020 ◽  
Vol 2 (1 (Nov)) ◽  
pp. 51-61
Author(s):  
Shangyan Zou ◽  
Ossama Abdelkhalik
Keyword(s):  
Relative Motion ◽  
Wave Energy ◽  
Control Strategy ◽  
Real Data ◽  
Nonlinear Damping ◽  
Irregular Waves ◽  
Coastal Observatory ◽  
Switching Control Strategy ◽  
Displacement Constraints ◽  
Two Bodies

Wave energy can be used to power oceanographic buoys. A new switching control strategy is developed in this paper for a two-body heaving wave energy converter that is composed of a floating cylinder and two rigidly connected submerged hemispheres. This control strategy is designed to prevent excessive displacement of the floating buoy that may occur due to the actuator force. This control strategy switches the control between a multi-resonant controller and a nonlinear damping controller, depending on the state of the system, to account for displacement constraints. This control strategy is developed using a one-degree-of-freedom dynamic model for the relative motion of the two bodies. Estimation of the relative motion, needed for feedback control, is carried out using a Kalman filter. Numerical simulations are conducted to select the proper mooring stiffness. The controller is tested with stochastic models of irregular waves in this paper. The performance of the controller with different sea states is discussed. Annual power production using this control strategy is presented based on real data in 2015 published by Martha's Vineyard Coastal Observatory.

scholarly journals Aberdeen University and the Royal Society

1955 ◽  
Vol 11 (2) ◽  
pp. 145-158 ◽  
Keyword(s):  
Canon Law ◽  
Liberal Arts ◽  
Royal Society ◽  
Point Of View ◽  
Significant Feature ◽  
King's College ◽  
James Iv ◽  
State Of Affairs ◽  
The University ◽  
Two Bodies

The library of Aberdeen University contains an interesting series of documents relating to early Fellows of the Royal Society. The purpose of this article is to make their existence more widely known to scholars and to give a sketch of the lives of some of the alumni of the University who were elected into the Society, which will serve as a background to the documents themselves. When the Royal Society received its Charter there were two distinct universities in Aberdeen, and so the matter remained for nearly two centuries. Since this unusual state of affairs, not being very generally known, is apt to cause confusion, it may be as well to indicate very briefly how it came about, and also what were the relations between the two bodies. It will later appear that the matter was not without influence on the lives and fortunes of some of those Fellows of the Royal Society, memorials of whom are to be found among the documents in the University Library. The Bull for the foundation of the University of Aberdeen and King’s College, as it came a little later to be called, was signed by Alexander VI (Borgia) on the petition of James IV on 10 February 1494. The document with the lead bulla intact, is in the Archives; the most significant feature from the point of view of the historian of science, is the naming of Medicine as well as Theology, Civil and Canon Law, and the Liberal Arts, as a ‘lawful faculty’. Not that there is any evidence of the prosecution of medical research during the ensuing century, but it betokened an unusual trust in the power of the infant university to cater for the higher studies. The Collegiate Chapel and halls were, and the former still is, in Old Aberdeen, near the mouth of the Don and a short distance from the ancient cathedral of St Machar, whose Bishop, William Elphinstone, had been the moving spirit and was nominated as the first Chancellor.

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