Name: lifting tong force analysis
Uploaded: 2023-09-22T11:49:25.000Z
Duration: 1 min 30 s
Channel: JoVE

Considérez une pince de levage portant une charge de 100 kg. Il se compose de sections mobiles DAF et CBG reliées entre elles par l’élément AB.
En supposant que la structure est symétrique par rapport au point E, quelle force agit sur le membre AB ?
Un schéma de corps libre indiquant les forces agissant au point E est dessiné.
La force de tension du câble équilibre le poids de la charge et agit verticalement vers le haut.
L’ED et l’EC sont des membres de deux forces. Ainsi, les forces FED et FEC sont dirigées vers les articulations D et C, respectivement.
Ces forces sont résolues en composantes horizontales et verticales, et la géométrie de la structure est appliquée pour déterminer l'angle entre l'ED de l'élément et la composante de force horizontale.
L’application de la condition d’équilibre des forces le long de la direction horizontale garantit que FED est égal à FEC.
De même, la condition d’équilibre de la force verticale produit la force le long de l’élément ED.
Considérons maintenant un schéma de corps libre pour la section DAF. La condition d’équilibre du moment peut être appliquée à l’articulation F. 
En substituant toutes les valeurs connues dans l’équation, on obtient la force le long de la barre AB.

<ol>
	<li>Hibbeler, R.C. (2016). Génie mécanique \u2012 Statique et dynamique. Hoboken, New Jersey : Pearson Prentice HallPppp 305.</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. p. 348</li>
	<li>Meriam, J.L., Kraige, L.G. et Bolton, J.N. (2020). Génie mécanique \u2012 Statique. Hoboken, New Jersey : John Wiley. page 200</li>
</ol>

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machines : problème de résolution ii

Les machines sont des structures complexes composées de membres mobiles, reliés par broches, qui travaillent ensemble pour transmettre des forces. Considérons une pince de levage transportant une charge de 100 kg. Elle est composée de sections mobiles DAF et CBG reliées par le membre AB. <img alt="Figure 1" src="/files/ftp_upload/14295/14295_PT_Fig_1v2.svg" style="text-align: center; height: 350px;"> En supposant que la structure est symétrique au point E, la force agissant sur le membre AB peut être calculée. Tout d'abord, un schéma corporel libre indiquant les forces agissant au point E est considéré. Le poids de la charge, égal à la masse multipliée par l'accélération due à la gravité, est calculé à 981 N. La force de tension du câble équilibre le poids de la charge et agit verticalement vers le haut. ED et EC sont des membres à deux forces. En conséquence, les forces FED et FEC sont dirigées respectivement vers les joints D et C. Ensuite, les forces FED et FEC sont résolues en composantes horizontales et verticales. La géométrie de la structure permet de calculer l'angle entre le membre ED et la composante horizontale de la force à 30,96 degrés. Les conditions d'équilibre des forces peuvent être appliquées au joint E. <img alt="Equation 1" src="/files/ftp_upload/14295/14295_PT_Equation_1v2.svg" style="text-align: center; height: 13px;"> <img alt="Equation 2" src="/files/ftp_upload/14295/14295_PT_Equation_2v2.svg" style="text-align: center; height: 13px;"> En appliquant la condition d'équilibre des forces dans la direction horizontale, on obtient que FED est égal à FEC. De même, la condition d'équilibre des forces verticales donne la force le long du membre ED égale à 953,46 N. Maintenant, un schéma corporel libre pour la section DAF est considéré. La condition d'équilibre du moment peut être appliquée au joint F. <img alt="Equation 3" src="/files/ftp_upload/14295/14295_PT_Equation_3v2.svg" style="text-align: center; height: 13px;"> Le résultat donne la force le long du membre AB égale à 2423,76 N. Comprendre les forces agissant sur chaque membre de ce système de pince de levage est essentiel pour assurer un fonctionnement sûr et concevoir des mécanismes de levage efficaces. En analysant les forces et en appliquant les conditions d'équilibre, les ingénieurs peuvent optimiser la structure et s'assurer qu'elle peut supporter en toute sécurité des charges dans différentes conditions.

Machines : Problème de résolution II

Les machines sont des structures complexes composées d’éléments multiforces mobiles et reliés par des broches qui travaillent ensemble pour transmettre des forces. Pensez à une pince de levage ...

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Machines: Problem Solving II

lifting tong force analysis

Lifting tong force analysis shows how forces move through a pin-connected machine. The structure uses movable sections DAF and CBG with member AB linking them together. Because these parts work as connected members, the load can be studied with equilibrium methods.

The example starts with a 100 kg load at point E. The load weight is found by multiplying mass by gravity, which gives 981 N. The cable tension acts upward and balances that weight. Since the structure is symmetrical at E, the forces on the two sides can be compared.

Members ED and EC are two-force members, so their forces act along the members toward joints D and C. Their forces are then split into horizontal and vertical parts. Using the geometry of the tong, the angle between member ED and the horizontal is 30.96 degrees. Force equilibrium at joint E shows that F ED equals F EC, and the vertical balance gives the force in member ED as 953.46 N.

After that, a free-body diagram for section DAF is used. The moment equilibrium condition is applied at joint F. This step gives the force in member AB as 2423.76 N. This kind of analysis helps engineers check the forces in each member so lifting systems can work safely and efficiently under load.

Lifting Tong Force Analysis

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Lifting tong force analysis shows how forces move through a pin-connected machine. The structure uses movable sections DAF and CBG with member AB linking them together. Because these parts work as connected members, the load can be studied with equilibrium methods. The example starts with a 100 kg load at point E. The load weight is found by multiplying mass by gravity, which gives 981 N. The cable tension acts upward and balances that weight. Since the structure is symmetrical at E, the...

key terms and concepts

Analyze a lifting tong with pin-connected members, symmetry, and equilibrium. See how force, tension, and moments determine the load on member AB.

Lifting Tong Force Analysis | JoVE K12

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Lifting Tong Force Analysis

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