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

I cuscinetti a collare sono un tipo di cuscinetto utilizzato nelle macchine per supportare carichi assiali su alberi rotanti, possono avere collari singoli o multipli.
Si consideri un cuscinetto a collare singolo soggetto a un carico assiale. L'area tra il raggio esterno e quello interno del collare è l'area di contatto totale del cuscinetto.
Supponendo che il supporto sia uniforme per il cuscinetto, la pressione normale uniforme può essere espressa come il rapporto tra la forza sull'area del cuscinetto.
Si consideri un elemento di area infinitesimale sul cuscinetto. La forza che agisce sull'area differenziale può essere espressa come prodotto del coefficiente di attrito, della pressione e dell'area differenziale.
Il momento richiesto per causare la rotazione imminente dell'albero è determinato dall'equazione di equilibrio del momento attorno all'asse di rotazione.
Successivamente, l'integrazione viene utilizzata per determinare il momento applicato necessario per superare tutte le forze di attrito.
Infine, sostituendo i valori della forza differenziale e dell'area differenziale e integrando l'equazione sull'area portante totale, è possibile stimare il momento dell'albero.

<ol>
	<li>Hibbeler, R.C. (2016). Ingegneria Meccanica \u2012 Statica e Dinamica. Hoboken, New Jersey: Pearson Prentice Hall. Pagine 447-448.</li>
</ol>

cuscinetti a colletto

I cuscinetti a colletto sono essenziali in varie macchine progettate per sostenere carichi assiali su alberi rotanti. A seconda dell'applicazione specifica e dei requisiti, possono ve ne possono essere con colletti singoli o multipli.

<img alt="Figure 1" src="/files/ftp_upload/14325/14325_Figure_1v3.svg" style="text-align: center; height: 300px;" />

Considera un cuscinetto a colletto singolo soggetto a un carico assiale. L'area totale di contatto del cuscinetto è la regione tra il raggio esterno e il raggio interno del colletto. Quando si assume che il cuscinetto fornisca un supporto uniforme, la pressione normale uniforme può essere calcolata dividendo la forza applicata sul colletto per l'area totale di contatto del cuscinetto. Questo valore rappresenta la distribuzione media di pressione sulla superficie del cuscinetto.

Per analizzare ulteriormente le forze che agiscono sul cuscinetto a colletto, considera un piccolo elemento di superficie infinitesimale sulla superficie del cuscinetto. La forza che agisce su questo elemento è il prodotto del coefficiente di attrito, della pressione e dell'area differenziale. Comprendere la relazione tra queste variabili è fondamentale per calcolare il momento richiesto per far ruotare l'albero.

<img alt="Equation 1" src="/files/ftp_upload/14325/14325_Equation_1v2.svg" style="text-align: center; height: 39px;" />

La rotazione imminente dell'albero è determinata analizzando l'equazione dell'equilibrio del momento sull'asse di rotazione. Questa equazione considera tutte le forze e i momenti che agiscono sull'albero, comprese le forze di attrito generate dal cuscinetto in questione.

<img alt="Equation 2" src="/files/ftp_upload/14325/14325_Equation_2v2.svg" style="text-align: center; height: 55px;" />

Integrando l'equazione, è possibile determinare il momento applicato necessario per superare tutte queste forze di attrito, che dà inizio alla rotazione dell'albero. Infine, per stimare il momento dell'albero, si sostituiscono i valori di forza differenziale e area, nell'equazione integrata.

<img alt="Equation 3" src="/files/ftp_upload/14325/14325_Equation_3v2.svg" style="text-align: center; height: 39px;" />

Integrando questa equazione sull'area totale del cuscinetto, si ottiene una comprensione completa delle forze e dei momenti che agiscono sul cuscinetto a colletto e il momento richiesto per far ruotare l'albero.

Cuscinetti a colletto

I cuscinetti a collare sono essenziali in varie macchine progettate per supportare carichi assiali su alberi rotanti. A seconda dell'applicazione specifica e ...

Education

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JoVE Core

Mechanical Engineering

Ingegneria Meccanica

Unit 1

Unità 1

Friction

Attrito

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

Collar Bearings

friction torque in collar bearings

Collar bearings support axial loads on rotating shafts, and their friction helps determine the torque needed to start motion. They are used in many machines and may have a single collar or multiple collars, depending on the application and load needs.

For a single collar bearing under an axial load, the contact area is the ring-shaped region between the external radius and the internal radius of the collar. If the bearing is assumed to support the load evenly, the uniform normal pressure is found by dividing the applied force by this total bearing contact area. This gives the average pressure across the bearing surface.

To study the forces more closely, a small infinitesimal area element is considered on the collar surface. The force on that tiny area equals the friction coefficient times the pressure times the differential area. Using this relationship is important for finding the moment required to rotate the shaft.

The impending rotation of the shaft is found by writing the moment equilibrium equation about the rotational axis. This equation includes the forces and moments on the shaft, along with the frictional forces from the collar bearing. When the equation is integrated over the full bearing area, the applied moment needed to overcome friction and begin rotation can be determined.

Friction Torque in Collar Bearings

dry friction

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static friction

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kinetic friction

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characteristics of dry friction

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pivot bearings

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collar bearings

Collar bearings support axial loads on rotating shafts, and their friction helps determine the torque needed to start motion. They are used in many machines and may have a single collar or multiple collars, depending on the application and load needs. For a single collar bearing under an axial load, the contact area is the ring-shaped region between the external radius and the internal radius of the collar. If the bearing is assumed to support the load evenly, the uniform normal pressure is...

journal bearings

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key terms and concepts

Learn how collar bearing contact area, pressure, and friction work together to set the torque needed to start shaft rotation in mechanical systems.

Friction Torque in Collar Bearings | JoVE K12

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mechanical engineering

Friction Torque in Collar Bearings

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