Name: tire deformation and rolling resistance
Uploaded: 2023-09-22T11:49:30.000Z
Duration: 1 min 21 s
Channel: JoVE

K12 Standards

Arizona Science Standards

High School

Physical Science

HS.P3

HS.P3U2.7

Rolling Resistance

Considere un neumático rodando a una velocidad constante. Las fuerzas que actúan sobre él son su peso y la fuerza normal.
Las superficies de contacto se deforman, creando un área de contacto finita. Esto da como resultado una distribución de fuerzas normales en cada punto de contacto.
La sección frontal de esta área experimenta una deformación, lo que retarda el movimiento de balanceo.
Por el contrario, la sección trasera se somete a una restauración relativamente más pequeña que empuja el neumático hacia adelante.
La fuerza normal resultante que actúa en A es la suma de estas fuerzas.
Para mantener el neumático rodando a una velocidad constante y equilibrar el momento del peso alrededor de A, se debe aplicar una fuerza motriz horizontal al centro del neumático. Aquí todas las fuerzas deben ser concurrentes.
La condición de equilibrio de momento en el punto A da la fuerza motriz en términos del coeficiente de resistencia a la rodadura.
El peso multiplicado por el coeficiente de resistencia a la rodadura en el radio suele ser menor que el coeficiente de fricción cinética multiplicado por el peso.
Por lo tanto, la fuerza de fricción de rodadura es menor que la fuerza de deslizamiento.

<ol>
	<li>Hibbeler, R.C. (2016). Ingeniería Mecánica \u2012 Estática y Dinámica. Hoboken, Nueva Jersey: Pearson Prentice Hall. págs. 452 \u2012 439.</li>
	<li>Meriam, J.L.; Kraige, L.G. y Bolton, J.N. (2020). Ingeniería Mecánica \u2012 Estática. Hoboken, Nueva Jersey: John Wiley. Págs. 372.</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. 469.</li>
</ol>

resistencia a la rodadura

Cuando un cilindro sólido rueda de manera constante sobre una superficie rígida, la fuerza normal ejercida por la superficie sobre el cilindro es perpendicular a la tangente en el punto de contacto. Sin embargo, dado que ningún material es completamente rígido, la reacción de la superficie al cilindro implica una gama de presiones normales. Por ejemplo, imaginemos un cilindro duro rodando sobre una superficie relativamente blanda. El peso del cilindro comprime la superficie debajo de él. A medida que el cilindro se mueve, el material delante de él se desacelera debido a la deformación mientras que el material detrás de él se recupera de su estado deformado, empujando el cilindro hacia adelante. Las presiones normales que actúan sobre el cilindro de esta manera se representan por sus fuerzas resultantes, Nd y Nr. La fuerza de deformación (Nd) y su componente horizontal son consistentemente mayores que la fuerza de restauración (Nr), lo que requiere que se aplique una fuerza de conducción horizontal sobre el cilindro para mantener su movimiento. La resistencia a la rodadura ocurre principalmente debido a este efecto, aunque también está influenciada, en menor medida, por la adhesión superficial y el microdeslizamiento relativo entre las superficies de contacto. Para comprender mejor este concepto, consideremos un neumático rodando a una velocidad constante. Las fuerzas principales que actúan sobre él son su peso, que actúa verticalmente hacia abajo, y la fuerza normal ejercida por el suelo, que actúa verticalmente hacia arriba. A medida que el neumático rueda, la sección delantera del área de contacto experimenta deformación, lo que retarda el movimiento de rodado del neumático. En contraste, la sección trasera experimenta una restauración relativamente menor que empuja el neumático hacia adelante. El efecto neto es que la fuerza normal resultante que actúa en el punto A (el centro del área de contacto) es la suma de estas fuerzas opuestas. <img alt="Figura 1" src="/files/ftp_upload/14328/14328_Figure_1v2.svg" style="text-align: center; height: 350px;"> Para mantener el neumático rodando a una velocidad constante y equilibrar el momento del peso alrededor del punto A, se debe aplicar una fuerza de conducción horizontal (F) al centro del neumático. Para lograr el equilibrio, todas las fuerzas que actúan sobre el neumático deben ser concurrentes. Usando la condición de equilibrio de momento en el punto A, podemos determinar la fuerza de conducción necesaria para mantener una velocidad constante en función del coeficiente de resistencia a la rodadura (a). <img alt="Ecuación 1" src="/files/ftp_upload/14328/14328_Equation_1v2.svg" style="text-align: center; height: 28px;"> Esta fuerza de conducción suele ser menor que el producto del coeficiente de fricción cinética y el peso del neumático. <img alt="Ecuación 2" src="/files/ftp_upload/14328/14328_Equation_2v2.svg" style="text-align: center; height: 28px;"> Esta relación implica que la fuerza de fricción al rodar suele ser menor que la fuerza de deslizamiento experimentada cuando un neumático derrapa sobre una superficie. Como resultado, la resistencia a la rodadura generalmente es menos perjudicial para el rendimiento de un vehículo que la fricción deslizante.

Resistencia a la rodadura

Cuando un cilindro sólido rueda constantemente sobre una superficie rígida, la fuerza normal aplicada por la superficie sobre el cilindro es perpendicular a la tangente en el ...

Education

Educación

JoVE Core

Mechanical Engineering

Ingeniería Mecánica

Unit 1

Unidad 1

Friction

Fricción

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

tire deformation and rolling resistance

Tire deformation and rolling resistance explain why a rolling wheel still needs a driving force. When a solid cylinder or tire rolls on a rigid surface, the normal force is perpendicular to the surface at the contact point. But real materials are not perfectly rigid, so the surface pushes back with a spread of normal pressures instead of one single force.

A hard cylinder on a softer surface compresses the material under it. As the cylinder moves forward, the material in front of the contact area slows because it is being deformed. The material behind the cylinder begins to recover, and that recovery pushes the cylinder forward.

These effects are often shown as two resultants, N d for the deformation force and N r for the restoration force. The deformation force and its horizontal component are larger than the restoration force. Because of that imbalance, a horizontal driving force must be applied to keep the cylinder moving.

The same idea applies to a tire rolling at constant speed. Its weight acts downward, and the ground provides an upward normal force. The front of the contact patch deforms and slows the tire, while the rear part restores more weakly and pushes it forward. The resultant normal force at point A is the sum of these opposing effects.

To keep the tire in equilibrium and maintain constant speed, a horizontal driving force F must act at the center of the tire. Using moment equilibrium about point A, the needed driving force can be written in terms of the rolling resistance coefficient a. This force is usually smaller than the force from kinetic friction, so rolling resistance is less harmful than sliding when a tire skids.

Rolling resistance is mainly caused by surface deformation, but adhesion and small-scale sliding between surfaces can also play a smaller role. These effects help explain why rolling wheels still lose some energy even when they do not appear to slip.

Tire Deformation and Rolling Resistance

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Tire Deformation and Rolling Resistance

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