A discussion of Arana, A., Larrañaga, J., & Ulacia, I. (2019). Partial EHL friction coefficient model to predict power losses in cylindrical gears. Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, Vol. 233(2) 303–316

2019 ◽  
Vol 234 (7) ◽  
pp. 1168-1170 ◽  
Author(s):  
Scott Bair
Keyword(s):  
Friction Coefficient ◽  
Pressure Dependence ◽  
Elastohydrodynamic Lubrication ◽  
Power Losses ◽  
True Nature ◽  
The Real ◽  
Cylindrical Gears ◽  
Real Nature ◽  
Heated Debate ◽  
Ehl Friction

There is presently a heated debate within the field of elastohydrodynamic lubrication (EHL). Some have attributed this to a controversy regarding the shear dependence of viscosity. However, the real nature of the debate is, as it has been for more than 40 years, whether or not to correctly describe the piezoviscous effect. If real pressure dependence of viscosity were to be employed in all EHL analyses, then the true nature of shear dependence would become apparent and the debate would end.

scholarly journals XIV.—On the Histology of the Pedicellariæ and the Muscles of Echinus sphæra (Forbes)

1881 ◽  
Vol 30 (1) ◽  
pp. 383-395 ◽  
Author(s):  
Patrick Geddes ◽  
Frank E. Beddard
Keyword(s):  
True Nature ◽  
The Real ◽  
Real Nature ◽  
Invertebrate Animals

The structures known as pedicellariæ were first described by O. F. Müller. He regarded them as parasitic organisms, and described under the generic name of Pedicellaria three species—Pedicellaria tridens, P. triphylla, and P. globifera. Lamarck, in the first edition of his “Animaux sans Vertèbres,” published in 1801, and also in the second edition, following Müller, classified the genus Pedicellaria with the Corynidæ and Hydridæ among the naked polyps. Cuvier also, in the first edition of the “Regne Animal,” took the same view of the nature of pedicellariæ. It was not until 1825 that the real nature of these organs was recognised. Delle Chiaje, in his work on invertebrate animals, asserted that pedicellariæ formed an integral portion of the Echinus, and were simply appendages of the test. The following quotation from his work shows that he thoroughly understood the true nature of these structures. He says (vol. ii. p. 324):—“Fanno elleno parte integrale degli echini e servon loro per attacarsi a corpi adiacenti ed anche a ritenere gli animaletti da cibarsi.”

Partial EHL friction coefficient model to predict power losses in cylindrical gears

2018 ◽  
Vol 233 (2) ◽  
pp. 303-316 ◽  
Author(s):  
Aitor Arana ◽  
Jon Larrañaga ◽  
Ibai Ulacia
Keyword(s):  
Friction Coefficient ◽  
Operating Conditions ◽  
Power Losses ◽  
Gear Mesh ◽  
Numerical Predictions ◽  
Reference Stress ◽  
Fluid Load ◽  
Stress Behaviour ◽  
Good Agreement ◽  
Ehl Friction

The accurate prediction of friction coefficient and power losses in the gear mesh is a key subject to several gear-related fields of study. However, there is still not a unified method for large ranges of operating conditions, different gear geometries and lubricant types. The current paper meets this demand by modelling partial EHL friction with an asperity-fluid load sharing approach where fluid traction is calculated with the Ree-Eyring equation and the reference stress behaviour is predicted from piezoviscosity coefficient. It will be shown that only an accurate description of the lubricant’s viscosity behaviour is required to compute friction in gears. Finally, mesh power losses are predicted considering thermal effects and numerical predictions are compared to experimental results showing good agreement.

King William and the Brecc Bennach in 1211: reliquary or holy banner?

2015 ◽  
Vol 66 (2) ◽  
pp. 163-190 ◽  
Author(s):  
Richard Sharpe
Keyword(s):  
Good Reason ◽  
National Museum ◽  
The Real ◽  
Real Nature

In his Rhind Lectures of 1879 Joseph Anderson argued for identifying the Monymusk Reliquary, now in the National Museum of Scotland, with the Brecc Bennach, something whose custody was granted to Arbroath abbey by King William in 1211. In 2001 David H. Caldwell called this into question with good reason. Part of the argument relied on different interpretations of the word uexillum, ‘banner’, taken for a portable shrine by William Reeves and for a reliquary used as battle-standard by Anderson. It is argued here that none of this is relevant to the question. The Brecc Bennach is called a banner only as a guess at its long-forgotten nature in two late deeds. The word brecc, however, is used in the name of an extant reliquary, Brecc Máedóc, and Anderson was correct to think this provided a clue to the real nature of the Brecc Bennach. It was almost certainly a small portable reliquary, of unknown provenance but associated with St Columba. The king granted custody to the monks of Arbroath at a time when he was facing a rebellion in Ross, posing intriguing questions about his intentions towards this old Gaelic object of veneration.

“The Real Nature and Spirit of Our Lives”

2018 ◽  
Author(s):  
Amanda Porterfield
Keyword(s):  
Economic Growth ◽  
African Americans ◽  
Social Organization ◽  
Labor Unions ◽  
Social Evolution ◽  
Fourteenth Amendment ◽  
The Real ◽  
Real Nature ◽  
Republican Liberty ◽  
The U.S

Proponents of social evolution blurred boundaries between commerce and Christianity after the Civil War, championing Christian work as a means to economic growth, republican liberty, and national prosperity. Meanwhile, workers invoked Christ to condemn patronizing attitudes toward labor, and by organizing labor unions to hold capitalists accountable to Pauline ideals of social membership. Influenced by organic theories of social organization that traced modern corporations to medieval institutions, U.S. courts began recognizing corporations as natural persons protected by rights guaranteed in the Fourteenth Amendment of the U.S. Constitution, which had originally be crafted to protect the rights of African Americans.

scholarly journals Relationship between the real contact behavior and tribological characteristics of cotton fabric

Friction ◽  
2020 ◽  
Author(s):  
Rongxin Chen ◽  
Jiaxin Ye ◽  
Wei Zhang ◽  
Jiang Wei ◽  
Yan Zhang ◽  
...  
Keyword(s):  
Friction Coefficient ◽  
Contact Area ◽  
Dynamic Change ◽  
Tribological Characteristics ◽  
Real Contact Area ◽  
Cotton Fibers ◽  
Friction Behavior ◽  
Contact Behavior ◽  
The Real ◽  
Real Contact

Abstract The tribological characteristics of cotton fibers play an important role in engineering and materials science, and real contact behavior is a significant aspect in the friction behavior of cotton fibers. In this study, the tribological characteristics of cotton fibers and their relationship with the real contact behavior are investigated through reciprocating linear tribotesting and real contact analysis. Results show that the friction coefficient decreases with a general increase in load or velocity, and the load and velocity exhibit a co-influence on the friction coefficient. The dynamic change in the real contact area is recorded clearly during the experiments and corresponds to the fluctuations observed in the friction coefficient. Moreover, the friction coefficient is positively correlated with the real contact area based on a quantitative analysis of the evolution of friction behavior and the real contact area at different loads and velocities. This correlation is evident at low velocities and medium load.

scholarly journals A thermal resistances-based approach for thermal-elastohydrodynamic calculations in point contacts

2017 ◽  
Vol 232 (11) ◽  
pp. 2088-2102 ◽  
Author(s):  
Eduardo de la Guerra Ochoa ◽  
Javier Echávarri Otero ◽  
Enrique Chacón Tanarro ◽  
Benito del Río López
Keyword(s):  
Friction Coefficient ◽  
Film Thickness ◽  
Thermal Effects ◽  
Good Accuracy ◽  
Computational Cost ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Point Contacts ◽  
New Approach ◽  
Ball On Disc

This article presents a thermal resistances-based approach for solving the thermal-elastohydrodynamic lubrication problem in point contact, taking the lubricant rheology into account. The friction coefficient in the contact is estimated, along with the distribution of both film thickness and temperature. A commercial tribometer is used in order to measure the friction coefficient at a ball-on-disc point contact lubricated with a polyalphaolefin base. These data and other experimental results available in the bibliography are compared to those obtained by using the proposed methodology, and thermal effects are analysed. The new approach shows good accuracy for predicting the friction coefficient and requires less computational cost than full thermal-elastohydrodynamic simulations.

The Real Nature of Pragmatism and Chicago Sociology

1983 ◽  
Vol 6 (1) ◽  
pp. 139-153 ◽  
Author(s):  
Eugene Rochberg-Halton
Keyword(s):  
The Real ◽  
Real Nature

Mechanical Power Losses of Ball Bearings: Model and Experimental Validation

2021 ◽  
pp. 1-29
Author(s):  
Ahmet Dindar ◽  
Amit Chimanpure ◽  
Ahmet Kahraman
Keyword(s):  
Dynamic Model ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Mechanical Power ◽  
Ball Bearings ◽  
Power Losses ◽  
Euler Parameters ◽  
Surface Shear ◽  
Axial Forces ◽  
Set Up

Abstract A tribo-dynamic model of ball bearings is proposed to predict their load-dependent (mechanical) power losses. The model combines (i) a transient, point contact mixed elastohydrodynamic lubrication (EHL) formulation to simulate the mechanics of the load carrying lubricated ball-race interfaces, and (ii) a singularity-free dynamics model, and establishes the two-way coupling between them that dictates power losses. The dynamic model employs a vectoral formulation with Euler parameters. The EHL model is capable of capturing two-dimensional contact kinematics, velocity variations across the contact as well as asperity interactions of rough contact surfaces. Resultant contact surface shear distributions are processed to predict mechanical power losses of example ball bearings operating under combined radial and axial forces. An experimental set-up is introduced for measurement of the power losses of rolling-element bearings. Sets of measurements taken by using the same example ball bearings are compared to those predicted by the model to assess its accuracy in predicting mechanical power loss of a ball bearing within wide ranges of axial and radial forces.

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