Name: forces that bend and twist materials
Uploaded: 2025-05-22T09:06:03.000Z
Duration: 1 min 20 s
Channel: JoVE

El momento flector se define como la reacción que se desarrolla en un elemento estructural al ser sometido a una fuerza externa, provocando la flexión del elemento.
Cuando un elemento estructural se somete a flexión, crea fuerzas normales de compresión en la parte superior y fuerzas normales de tracción en la parte inferior, lo que da como resultado un par que determina el momento de flexión del elemento.
La flexión de una regla fija en un extremo, un trampolín y el salto con pértiga son algunos ejemplos de momentos de flexión.
Un momento de torsión ocurre cuando se aplica una fuerza de torsión a un cuerpo a lo largo de su eje transversal, lo que hace que la sección se tuerza.
Desgarrar la ropa, atornillar y resortes de torsión son algunos ejemplos de momentos de torsión.
Las fuerzas internas y los momentos de acoplamiento que actúan sobre una sección transversal de una viga se pueden representar mediante sus componentes x, y y z.
El momento de torsión, My se representa a lo largo de la dirección y, mientras que Mx y Mz representan los componentes del momento de flexión a lo largo de las direcciones x y z.

<ol>
	<li>Hibbeler, R.C. (2016) Mecánica de ingeniería: estática y dinámica Hoboken, Nueva Jersey: Pearson Prentice Hall, pp 344-345.</li>
	<li>Meriam, J.L.; Kraige, L.G., y Bolton, J.N. (2020). Ingeniería Mecánica \u2012 Estática. Hoboken, Nueva Jersey: John Wiley. Págs. 276.</li>
</ol>

momentos de flexión y torsión

Bending and Torsional Moments

Momentos de flexión y torsión son dos conceptos fundamentales en la ingeniería estructural. Juegan un papel importante en la comprensión del comportamiento de los materiales y estructuras bajo diferentes condiciones de carga. La reacción desarrollada en un elemento estructural cuando es sometido a una fuerza externa hace que el elemento se doble. Cuando un elemento estructural se dobla hacia arriba, crea fuerzas normales compresivas en la parte superior y fuerzas normales de tracción en la parte inferior, lo que resulta en un par que determina el momento de flexión del elemento. Este momento se calcula tomando en cuenta la distancia desde el punto de interés hasta la línea de acción de la fuerza y la magnitud de la fuerza. La flexión de una regla fija en un extremo es un ejemplo de un momento de flexión. Cuando se aplica una fuerza hacia abajo perpendicular a la regla cerca del extremo no soportado, induce la flexión en la regla. La fuerza aplicada crea un momento alrededor del extremo fijo, lo que provoca que la regla se doble o se deforme. En este escenario, la regla experimentará tanto fuerzas compresivas como fuerzas de tracción. El lado superior de la regla, en dirección opuesta a la fuerza aplicada, estará sometido a tensión. El lado inferior, en dirección hacia la fuerza aplicada, estará sometido a compresión. Un momento de torsión ocurre cuando se aplica una fuerza de torsión a un cuerpo a lo largo de su eje transversal o longitudinal, provocando que la sección se retuerza. Esta fuerza de torsión crea una resistencia interna dentro del material, oponiéndose a la fuerza aplicada. El momento de torsión se calcula como el producto de la fuerza de torsión y la distancia desde el punto de interés hasta la línea de acción de la fuerza. Al conducir un tornillo en un material usando un destornillador o un taladro eléctrico, se aplica un momento de torsión al tornillo a medida que gira y encuentra resistencia del material. La fuerza de torsión generada por el destornillador o el taladro eléctrico hace que el tornillo gire, y la resistencia del material crea una fuerza opuesta, que genera un momento de torsión.

Momentos de flexión y torsión

Los momentos de flexión y torsión son dos conceptos fundamentales en la ingeniería estructural. Juegan un papel importante en la comprensión del comportamiento de ...

Education

Educación

JoVE Core

Mechanical Engineering

Ingeniería Mecánica

Unit 1

Unidad 1

Internal Forces

Fuerzas internas

KEY TERMS AND CONCEPTS

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forces that bend and twist materials

Bending and torsional moments describe how materials respond to force. These ideas are important in structural engineering because they help explain how beams, rulers, and screws change shape under load. A moment depends on both the size of the force and the distance from the point of interest to the force’s line of action.

A bending moment forms when an external force makes a structural element bend. If the element bends upward, the top side is in compression and the bottom side is in tension. These opposite forces create a couple that determines the bending moment. A ruler fixed at one end shows this effect when a downward force is applied near the free end.

In that ruler example, the force acts perpendicular to the ruler and causes it to deform around the fixed end. The side facing away from the applied force is in tension, and the side facing toward the force is in compression. This makes the bending moment easy to see in a simple everyday object.

A torsional moment happens when a twisting force is applied along a body’s transverse or longitudinal axis. The material resists that twist, so an internal force develops inside it. A screwdriver or power drill turning a screw shows torsion in action. As the screw rotates and meets resistance from the material, the twisting force and the opposing resistance create the torsional moment.

Forces That Bend and Twist Materials

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Beam analysis depends on the internal forces and moments inside a structure. These include normal force, shear force, and bending moment. Engineers use the method of sections to cut the beam and find these values. A sign convention helps show whether each result is positive or negative. Normal force acts perpendicular to the beam’s cross-section. It can pull the material in tension or push it in compression. Tension is taken as positive, while compression is taken as negative. This makes it...

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Beam loads create internal forces inside a structure. Weight, pressure, and other external forces can all act on a beam. These internal forces affect the beam’s stability and strength. Engineers study these forces to find their size and direction. A common approach is the method of sections. In this method, an imaginary cut is made at a chosen point on the beam, and the forces at that section are analyzed. One internal force is the normal force, also called the axial force. It acts...

bending and torsional moments

Bending and torsional moments describe how materials respond to force. These ideas are important in structural engineering because they help explain how beams, rulers, and screws change shape under load. A moment depends on both the size of the force and the distance from the point of interest to the force’s line of action. A bending moment forms when an external force makes a structural element bend. If the element bends upward, the top side is in compression and the bottom side is in tension.

internal loadings in structural members: problem solving

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Beam Internal Force Analysis at Point A

Beam internal force analysis shows how normal force, shear force, and bending moment act inside a structural member. These internal loadings help engineers check whether a beam can support the external forces applied to it. The example uses a beam OC that weighs 5 kN and is inclined at 53.13° with the horizontal. The beam is supported at both ends. The goal is to find the internal loadings at point A. The first step is to find the reaction force at point C. This is done by taking the moment...

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Beam shear force diagrams show how shear changes along the length of a supported beam. In beam mechanics, they help students track the internal shear force caused by perpendicular loads. The beam AB in this example is supported at both ends, so the first step is to draw a free-body diagram that shows the external forces and internal reactions. The reaction forces at supports A and B are found with equilibrium equations for force and moment. For the beam shown, the vertical reaction at A is 24...

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relation between the distributed load and shear

relation-between-the-distributed-load-and-shear

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Shear force changes along a beam under a distributed load. In structural analysis, this relationship helps explain how beams respond to loading conditions that also include concentrated loads and a couple moment. To study the link, consider a small beam section that has no concentrated load or couple moment on it. Draw a free-body diagram for that elemental section. It includes the distributed load along the beam, the shear force V(x) on the right-hand side of the cut, and a small added shear...

relation between the shear and bending moment

relation-between-the-shear-and-bending-moment

Shear and Moment Diagrams in Beam Loads

Shear and moment diagrams help show how a beam responds to loads. A beam can carry a distributed load, concentrated loads, and a couple moment. These loads create internal shear forces and bending moments. The beam is examined by isolating a small elemental section and drawing a free-body diagram. For that section to stay in equilibrium, the moment on the right side must be slightly larger than the moment on the left side. The distributed load also has a resultant force that acts at a...

shear and bending moment diagram: problem solving

shear-and-bending-moment-diagram-problem-solving

Beam Load Analysis with Shear Diagrams

Beam load analysis uses shear and bending moment diagrams to track the internal forces in a beam. These diagrams are important when a beam carries concentrated loads and a distributed load. They help show how the beam responds so structures can be designed safely and efficiently. The first step is to draw a free-body diagram of the whole beam. A free-body diagram shows the concentrated loads, the distributed load, and the reaction forces at the supports. Use the equilibrium equations, where...

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Flexible cables can carry vertical point loads between two fixed supports. The cable is treated as flexible, inextensible, and nearly weightless. Under these conditions, it changes shape to form straight-line segments, and each segment carries a constant tensile force. To analyze the cable, a free-body diagram is drawn for the whole cable. This helps identify the reaction forces at the supports. In many cases, the number of unknown reaction components is greater than the available equilibrium...

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Overhead power transmission cables sag under their own weight, and that shape affects how they carry electricity across long distances. To study this behavior, the cable is analyzed with a generalized loading function. This function treats the load along the cable's arc length instead of its projected length, which gives a more accurate picture of the cable's response. The analysis then focuses on a small cable segment. A free-body diagram is drawn to show the forces acting on that segment.

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Cable tension under uniform loading is found by analyzing a cable fixed between two supports. The problem starts with the support conditions and the load on the cable. From there, the cable’s shape must be described with an equation that matches the curve formed by the load. The next step is to integrate the shape equation to get the cable’s shape function. This makes it possible to solve for constants in the equation. The boundary condition at the origin gives one constant. The slope, which...

key terms and concepts

Explore how bending and torsional moments act on materials, from a ruler bending at one end to a screw twisting under a screwdriver.

Forces That Bend and Twist Materials | JoVE K12

JoVE Core Mechanical Engineering offers concise, easy-to-understand animated videos covering key topics such as equilibrium, forces, truss analysis, and structural mechanics. Explore their real-world applications, and witness these concepts in action through scientist-led experiments.

mechanical engineering

Forces That Bend and Twist Materials

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