Name: friction moment in journal bearings
Uploaded: 2023-09-22T11:49:30.000Z
Duration: 1 min 23 s
Channel: JoVE

Les paliers lisses sont utilisés pour assurer la stabilité latérale des arbres et des essieux en rotation.
Envisagez un treuil à câble avec des paliers lisses secs ou partiellement lubrifiés.
La rotation dans le sens des aiguilles d'une montre de la bobine fait rouler l'arbre sur la surface intérieure du roulement jusqu'à ce qu'il glisse et subisse une rotation stable.
Un schéma de corps libre de l’arbre est dessiné. Les forces agissant sur le système comprennent le poids de l'arbre, le couple dans le sens des aiguilles d'une montre et la force de réaction du roulement.
La force de réaction non colinéaire est égale et opposée au poids et agit à un angle par rapport à la normale de surface. Cet angle est appelé angle de frottement cinétique.
La ligne d’action de la force de réaction est toujours tangente au cercle de frottement.
La condition d’équilibre des moments autour du point O donne le moment de l’arbre.
Pour un petit angle de frottement cinétique, le terme sinusoïdal peut être approximé à la tangente de l’angle de frottement cinétique.
Comme la tangente de l'angle de frottement cinétique est égale au coefficient de frottement cinétique, le moment nécessaire pour surmonter la résistance au frottement du roulement est obtenu.

<ol>
	<li>Hibbeler, R.C. (2016). Génie mécanique \u2012 Statique et dynamique. Hoboken, New Jersey : Pearson Prentice Hall. Pages 450.</li>
	<li>Meriam, J.L. ; Kraige, L.G. et Bolton, J.N. (2020). Génie mécanique \u2012 Statique. Hoboken, New Jersey : John Wiley. Pages 364.</li>
	<li>Bière, F.P. ; Johnston, E.R. ; Mazurek, D.F ; Cromwell, P.J. et Self, B.P. (2019). Mécanique vectorielle pour les ingénieurs \u2012 Statique et dynamique. New York : McGraw-Hill. Pages 459 et 460.</li>
</ol>

les paliers de journal

Journal Bearings

Les paliers de journal sont des composants mécaniques qui soutiennent et assurent la stabilité latérale des arbres et essieux rotatifs. Ils sont essentiels pour réduire le frottement, l'usure et les vibrations dans des machines telles que les moteurs, les turbines et les pompes. Le principe des paliers de journal consiste à former un film mince de lubrifiant entre la surface du palier et l'arbre rotatif, ce qui réduit les contacts directs et les forces de frottement. Pour mieux comprendre le concept des paliers de journal, prenons l'exemple d'un treuil à corde avec des paliers de journal non lubrifiés ou partiellement lubrifiés soutenant son arbre rotatif. Lorsque la bobine tourne dans le sens des aiguilles d'une montre, l'arbre roule sur la surface interne du palier jusqu'à ce qu'il glisse et subisse une rotation stable. <img alt="Figure 1" src="/files/ftp_upload/14326/14326_Figure_1v2.svg" style="text-align: center; height: 300px;"> Un diagramme des forces appliquées sur l'arbre peut être dessiné pour analyser les forces agissant sur le système. Ces forces comprennent le poids de l'arbre, agissant verticalement vers le bas, le couple dans le sens des aiguilles d'une montre, représentant le couple appliqué à l'arbre, et la force de réaction exercée par le palier sur l'arbre. La force de réaction non colinéaire est égale et opposée au poids de l'arbre et agit à un angle par rapport à la normale de la surface. Cet angle est appelé l'angle de frottement cinétique. La ligne d'action de la force de réaction est toujours tangente au cercle de frottement, qui représente l'ensemble des points de contact possibles entre l'arbre et le palier. En appliquant la condition d'équilibre de moment autour du point O (le centre de l'arbre), nous pouvons déterminer le moment de l'arbre nécessaire pour maintenir une rotation stable. <img alt="Equation 1" src="/files/ftp_upload/14326/14326_Equation_1v2.svg" style="text-align: center; height: 13px;"> Le terme sinus dans l'équation peut être approximé par la tangente de l'angle de frottement cinétique pour un petit angle de frottement cinétique. <img alt="Equation 2" src="/files/ftp_upload/14326/14326_Equation_2v2.svg" style="text-align: center; height: 13px;"> Comme la tangente de l'angle de frottement cinétique est égale au coefficient de frottement cinétique, nous pouvons calculer le moment nécessaire pour surmonter la résistance de frottement du palier. Ce moment est un facteur essentiel pour déterminer l'efficacité et les performances du système. <img alt="Equation 3" src="/files/ftp_upload/14326/14326_Equation_3v2.svg" style="text-align: center; height: 13px;">

Les paliers de journal

Les paliers lisses sont des composants mécaniques qui soutiennent et assurent la stabilité latérale des arbres et des essieux en rotation. Ils sont cruciaux pour réduire les frictions, ...

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friction moment in journal bearings

Journal bearings support rotating shafts and axles while helping keep them stable. They are used in machines such as engines, turbines, and pumps. Their job is to reduce friction, wear, and vibration.

A journal bearing works by keeping a thin film of lubricant between the bearing surface and the rotating shaft. This film limits direct contact and lowers frictional force. The video uses a rope winch with dry or only partly lubricated journal bearings to show the idea.

As the spool turns clockwise, the shaft first rolls up the inner surface of the bearing. It then slips and settles into stable rotation. A free-body diagram of the shaft helps show the forces in the system.

The diagram includes the weight of the shaft, a clockwise couple that represents the applied torque, and the reaction force from the bearing. The reaction force is not collinear with the weight of the shaft. It acts at an angle to the surface normal, and that angle is called the angle of kinetic friction.

The line of action of the reaction force is tangent to the circle of friction. The circle of friction is the set of possible contact points between the shaft and the bearing. By using moment equilibrium about point O, the center of the shaft, the needed shaft moment can be found.

For a small kinetic friction angle, the sine term in the equation can be approximated by the tangent of that angle. Since the tangent of the kinetic friction angle equals the coefficient of kinetic friction, the required moment can be calculated from it. This moment helps describe the bearing’s frictional resistance and its effect on efficiency and performance.

Friction Moment in Journal Bearings

dry friction

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journal bearings

Journal bearings support rotating shafts and axles while helping keep them stable. They are used in machines such as engines, turbines, and pumps. Their job is to reduce friction, wear, and vibration. A journal bearing works by keeping a thin film of lubricant between the bearing surface and the rotating shaft. This film limits direct contact and lowers frictional force. The video uses a rope winch with dry or only partly lubricated journal bearings to show the idea. As the spool turns...

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key terms and concepts

Learn how journal bearings support rotating shafts, reduce friction, and create the reaction force and moment used to analyze stable rotation.

Friction Moment in Journal Bearings | JoVE K12

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Friction Moment in Journal Bearings

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