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

Los cojinetes de deslizamiento se utilizan para proporcionar estabilidad lateral a los ejes y ejes giratorios.
Considere un cabrestante de cable con cojinetes de deslizamiento secos o parcialmente lubricados.
La rotación del carrete en el sentido de las agujas del reloj hace que el eje suba por la superficie interior del rodamiento hasta que se desliza y se somete a una rotación estable.
Se dibuja un diagrama de cuerpo libre del eje. Las fuerzas que actúan sobre el sistema incluyen el peso del eje, el par en el sentido de las agujas del reloj y la fuerza de reacción del rodamiento.
La fuerza de reacción no colineal es igual y opuesta al peso y actúa en un ángulo relativo a la superficie normal. Este ángulo se denomina ángulo de fricción cinética.
La línea de acción de la fuerza de reacción es siempre tangente al círculo de fricción.
La condición de equilibrio de momento alrededor del punto O produce el momento del eje.
Para un ángulo de fricción cinético pequeño, el término sinusoidal se puede aproximar a la tangente del ángulo de fricción cinético.
Como la tangente del ángulo de fricción cinética es igual al coeficiente de fricción cinética, se obtiene el momento necesario para superar la resistencia de fricción del rodamiento.

<ol>
	<li>Hibbeler, R.C. (2016). Ingeniería Mecánica \u2012 Estática y Dinámica. Hoboken, Nueva Jersey: Pearson Prentice Hall. Págs. 450.</li>
	<li>Meriam, J.L.; Kraige, L.G. y Bolton, J.N. (2020). Ingeniería Mecánica \u2012 Estática. Hoboken, Nueva Jersey: John Wiley. Págs. 364.</li>
	<li>Cerveza, F.P.; Johnston, E.R.; Mazurek, D.F.; Cromwell, P.J. y Self, B.P. (2019). Mecánica vectorial para ingenieros: estática y dinámica. Nueva York: McGraw-Hill. Págs. 459-460.</li>
</ol>

cojinetes de revista

Journal Bearings

Los cojinetes de revista son componentes mecánicos que respaldan y proporcionan estabilidad lateral a los ejes y ejes rotativos. Son cruciales para reducir la fricción, el desgaste y la vibración en maquinaria como motores, turbinas y bombas. El principio detrás de los cojinetes de revista es formar una fina película lubricante entre la superficie del cojinete y el eje rotativo, lo que minimiza el contacto directo y reduce las fuerzas de fricción. Para comprender mejor el concepto de los cojinetes de revista, considere un cabrestante de cuerda con cojinetes de revista secos o parcialmente lubricados que respaldan su eje rotativo. A medida que el carrete gira en sentido horario, el eje se enrola en la superficie interna del cojinete hasta que resbala y experimenta una rotación estable. <img alt="Figure 1" src="/files/ftp_upload/14326/14326_Figure_1v2.svg" style="text-align: center; height: 300px;"> Se puede dibujar un diagrama de cuerpo libre del eje para analizar las fuerzas que actúan sobre el sistema. Estas fuerzas incluyen el peso del eje, que actúa verticalmente hacia abajo, el par en sentido horario, que representa el par aplicado al eje, y la fuerza de reacción ejercida por el cojinete sobre el eje. La fuerza de reacción no colineal es igual y opuesta al peso del eje y actúa en un ángulo relativo a la normal de la superficie. Este ángulo se denomina ángulo de fricción cinética. La línea de acción de la fuerza de reacción siempre es tangente al círculo de fricción, que representa el lugar geométrico de todos los puntos posibles de contacto entre el eje y el cojinete. Al aplicar la condición de equilibrio de momentos alrededor del punto O (el centro del eje), podemos determinar el momento del eje necesario para mantener una rotación estable. <img alt="Equation 1" src="/files/ftp_upload/14326/14326_Equation_1v2.svg" style="text-align: center; height: 13px;"> El término seno en la ecuación se puede aproximar a la tangente del ángulo de fricción cinética para un ángulo de fricción cinética pequeño. <img alt="Equation 2" src="/files/ftp_upload/14326/14326_Equation_2v2.svg" style="text-align: center; height: 13px;"> Dado que la tangente del ángulo de fricción cinética es igual al coeficiente de fricción cinética, podemos calcular el momento requerido para superar la resistencia a la fricción del cojinete. Este momento es un factor esencial para determinar la eficiencia y el rendimiento del sistema. <img alt="Equation 3" src="/files/ftp_upload/14326/14326_Equation_3v2.svg" style="text-align: center; height: 13px;">

Cojinetes de revista

Los cojinetes de deslizamiento son componentes mecánicos que soportan y proporcionan estabilidad lateral a los ejes y ejes giratorios. Son cruciales para reducir la fricción, ...

Education

Educación

JoVE Core

Mechanical Engineering

Ingeniería Mecánica

Unit 1

Unidad 1

Friction

Fricción

KEY TERMS AND CONCEPTS

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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

Dry Friction in Crates and Everyday Motion

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static friction

Static Friction at the Point of Slip

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kinetic friction

Sliding Friction Between Moving Surfaces

Kinetic friction is the sliding friction that acts when two surfaces move against each other. It opposes relative motion and acts parallel to the contact surface, in the opposite direction of travel. In the truck and car example, the car first stays still because static friction holds it in place. When the truck’s force becomes greater than the limiting static frictional force, the friction at the contact surface drops to a lower value. The car then begins to slide, and its speed increases. At...

characteristics of dry friction

Static and Kinetic Dry Friction

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types of friction problems

Dry Friction in Crate, Ladder, and Frame Problems

Dry friction problems often focus on crates, ladders, and frames that are close to slipping. Dry friction is the force that resists relative motion, or the tendency for motion, between two surfaces in contact. In many physics and engineering problems, this force helps keep an object still or defines the point where motion is about to begin. One common case has no clear impending motion. A force may be applied to a crate, but the crate stays at rest. The friction force between the floor and the...

friction: problem solving

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wedges

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frictional forces on screws

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upward impending motion

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self-locking screw

Screw Jack Self-Locking Behavior

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screw: problem solving

Screw Torque and Self-Locking

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frictional forces on flat belts

Flat Belt Tension and Friction

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flat belts: problem solving

Flat Belt Forces and Pulley Moment

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pivot bearings

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collar bearings

Friction Torque in Collar Bearings

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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...

bearings: problem solving

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rolling resistance

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rolling resistance: problem solving

Lawn Roller Force Calculation

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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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mechanical engineering

Friction Moment in Journal Bearings

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