Name: normal stress in axial loading
Uploaded: 2024-03-07T13:22:32.000Z
Duration: 1 min 19 s
Channel: JoVE

Considérons une tige soumise à une force axiale ; en conséquence, une force résistive se développe sur toute la surface de la section transversale, ce qui est appelé contrainte. L’unité SI de contrainte est le Newton par mètre carré.
Considérons maintenant un élément de poutre de pont soumis à une force axiale. Il développe des forces internes et des contraintes normales au plan de la section transversale, appelées contraintes normales.
La contrainte normale résultante représente une contrainte moyenne sur la section transversale, plutôt qu’en un point spécifique.
Selon les conditions d’équilibre, les forces internes sont égales à la force appliquée, ce qui implique que la distribution des contraintes est uniforme, sauf près du point d’application.
Cependant, cette répartition uniforme n’est possible que si la ligne d’action des charges passe par le centroïde de la section, ce que l’on appelle la charge centrique.
Lorsque la charge axiale est appliquée de manière excentrique, la répartition des forces et des contraintes ne peut pas être uniforme ou symétrique en raison du moment supplémentaire créé.
Ainsi, la distribution réelle des contraintes dans un élément chargé axialement est statiquement indéterminée et dépend du mode spécifique d’application de la charge.

contrainte normale

La contrainte normale est un type de contrainte qui se produit lorsque des forces agissent de manière perpendiculaire, ou normale, envers la section transversale d'un matériau. Cette contrainte apparaît souvent dans les structures lorsqu'elles sont soumises à une charge axiale, c'est-à-dire à l'application d'une force le long de l'axe d'un objet. Un exemple pratique de ceci peut être trouvé dans les éléments individuels des ponts à treillis.

Lorsqu'une tige est soumise à une charge axiale, les forces internes et la contrainte correspondante sont normales au plan de la section, on parle donc de contrainte normale. Il est important de noter que la contrainte représente la valeur de contrainte moyenne sur la section transversale, et non à un point spécifique. La contrainte moyenne est calculée en divisant l'ampleur des forces internes résultantes réparties sur la section transversale par la surface de la section.

<img alt="Equation 1" src="/files/ftp_upload/15579/15579_Equation_1.svg" style="text-align: center; height: 42px;">
Cependant, la contrainte en un point donné peut différer de la contrainte moyenne, car elle varie dans la section. En particulier dans le cas de tiges fines soumises à des charges axiales, la variation peut être significative à proximité des points d'application de la charge.

Les conditions d'équilibre suggèrent une répartition uniforme des contraintes dans les éléments chargés axialement, sauf à proximité des points d'application de la charge, en supposant un chargement centré. Cependant, une charge excentrique crée une contrainte non uniforme en raison de moments supplémentaires, indiquant une répartition des contraintes statiquement indéterminée.

Contrainte normale

Considérons une tige soumise à une force axiale ; En conséquence, une force résistive est développée sur toute la surface de la section transversale, ce qui est appelé contrainte. L’I.S. ...

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Mechanical Engineering

Génie mécanique

Unit 1

Unité 1

Concept of Stress

Le concept de stress

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

Normal Stress

normal stress in axial loading

Normal stress acts perpendicular to a material’s cross-sectional area. It appears when a force is applied along the axis of an object, which is called axial loading. Bridge truss members are a practical example of this kind of loading.

When a rod carries axial load, internal forces develop across the section. Because these forces act normal to the plane of the section, the stress is called normal stress. Stress here means the average stress over the whole cross-section, not the value at one exact point.

The average stress is found by dividing the resultant internal force by the cross-sectional area. The stress at a specific point can be different from that average, since it may vary across the section. In slender rods under axial load, that variation can be large near the points where the load is applied.

For a centric load, equilibrium suggests a uniform stress distribution in an axially loaded member, except near the load application points. Eccentric loading changes that pattern. It creates non-uniform stress because extra moments act on the member, so the stress distribution becomes statically indeterminate.

Normal Stress in Axial Loading

normal stress

Normal stress acts perpendicular to a material’s cross-sectional area. It appears when a force is applied along the axis of an object, which is called axial loading. Bridge truss members are a practical example of this kind of loading. When a rod carries axial load, internal forces develop across the section. Because these forces act normal to the plane of the section, the stress is called normal stress. Stress here means the average stress over the whole cross-section, not the value at one...

shearing stress

Shear Forces in Bolts and Rivets

Shearing stress is caused by transverse forces acting on an object. These forces create internal forces in the plane where the external forces are applied. The total internal force in that section is called the shear. Average shearing stress is found by dividing the shear by the cross-sectional area. This value is only an average, because shear stress is not spread evenly across the section. It can be zero at the surface and much higher than the average in other areas. Bolts, pins, and rivets...

bearing stress

Bolt-to-Plate Contact Pressure

Bearing stress is the contact pressure between two separate bodies. A common example is a bolt pushed through a plate. The bolt applies a force to the plate, and the plate pushes back with an equal and opposite force. That force is not a single point load. It is made up of many smaller forces spread across the contact surface between the bolt and the plate. Because these microforces are complex, engineers use an average value called bearing stress. Bearing stress is found by dividing the...

applications of stress

Boom and Rod Stress Analysis

Boom and rod stress analysis shows how a pinned support structure carries a load. The boom and the rod are connected by a pin and held in place by brackets and pins. The structure is then separated from its supports so the forces can be studied clearly. A free-body diagram is drawn to identify every force on the boom, the rod, and the load. The reaction forces on both members are found using equilibrium equations. At point P, the reaction causes compression in the boom. At point R, the...

stress on an oblique plane

Axial Load Stress on Inclined Sections

Axial loading creates stress in a material along its central axis. This kind of load can cause compression or elongation, and it produces normal stress. Normal stress acts perpendicular to the material area and can be either tensile or compressive. When the section is not perpendicular to the load, it becomes an oblique plane. On this inclined plane, the stress state includes both normal stress and shearing stress. Shearing stress acts parallel to the area and changes shape without changing...

stress: general loading conditions

Stress Components on a Loaded Body

Stress components on a loaded body can be found by cutting the body through a point with a plane parallel to the xy plane. That section carries the original loads, along with normal forces and shearing forces. The result is a simple way to describe how a structure responds under combined loading. The shearing force in the section can point in different directions within the plane. It is split into two parts that run parallel to the x and y axes. Each part is divided by the area, and as that...

components of stress

Stress Components on a Cube at a Point

Stress components on a small cube help describe how a body behaves under multiple loading. The cube is centered at point O and has stress acting on all six faces, whether the faces are visible or hidden. Normal stress components σx, σy, and σz act perpendicular to the x, y, and z axes. Shearing stress components also act on the cube faces. The visible faces carry shear stresses such as τxy and τxz. The hidden faces carry equal and opposite stresses. This balance keeps the cube in equilibrium.

design consideration

Safety Factors in Structural Design

Safety factors in structural design help engineers choose a material and loading limit that can be used safely. The process begins with a material’s ultimate strength. This value comes from tests that increase force until the material reaches its breaking point or limit. The ultimate load is then divided by the original cross-sectional area to find the ultimate normal stress, or strength. Ultimate shearing stress is another key value used in design. These limits show how much stress a material...

key terms and concepts

Learn how normal stress forms in axially loaded members, how to calculate average stress, and why stress can vary across a cross-section.

Normal Stress in Axial Loading | 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

Normal Stress in Axial Loading

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