Name: boom and rod stress analysis
Uploaded: 2024-03-07T13:22:32.000Z
Duration: 1 min 4 s
Channel: JoVE

Considérons une structure composée d’une flèche et d’une tige conçue pour supporter une charge. La flèche et la tige sont reliées par une goupille et soutenues par des supports et des goupilles.
Tout d’abord, pour analyser les différentes contraintes agissant sur la structure, la flèche et la tige sont détachées des supports, et le schéma du corps libre est dessiné.
En considérant les équations d’équilibre, les forces de réaction agissant sur la rampe et la tige sont calculées.
Les réactions au point P provoquent une compression dans la flèche, et les réactions au point R provoquent une tension dans la tige.
Les forces exercées sur la goupille Q par la flèche et la tige peuvent être déterminées à l’aide d’un triangle de force.
La contrainte normale résultant de la force axiale sur la flèche est calculée en divisant la force dominante sur l’élément par la section transversale de la flèche.
La contrainte normale agissant sur la tige est déterminée de la même manière.

applications du stress

Applications of Stress

Considérons une structure constituée d'une flèche et d'une tige conçue pour supporter une charge. Ces deux composants sont reliés par une broche et stabilisés par des supports et des broches. La flèche et la tige sont détachées de leurs supports pour évaluer les différentes contraintes imposées à cette structure, et un diagramme de corps libre est tracé. Ensuite, toutes les forces appliquées, y compris la charge agissant sur la structure, sont identifiées. Les forces de réaction exercées à la fois sur la flèche et sur la tige sont calculées à l'aide des équations d'équilibre.

Les réactions au point P provoquent une compression dans la flèche, et celles au point R provoquent une tension dans la tige. Les deux membres sont des membres à deux forces, soumis à des forces en deux points seulement. Les lignes d’action des forces résultantes agissant en chacun de ces deux points sont égales et opposées et passent par les deux points. Les forces exercées sur l'articulation par ces éléments peuvent être déterminées à l'aide d'un triangle de force. La contrainte normale résultante de la force axiale exercée sur la flèche est déterminée en divisant la force dominante exercée sur l'élément par la section transversale de la flèche. De même, la contrainte normale agissant sur la tige est calculée.

Applications du stress

Considérons une structure composée d’une flèche et d’une tige conçue pour supporter une charge. La flèche et la tige sont reliées par une goupille et soutenues par des supports et ...

Education

Enseignement

JoVE Core

Mechanical Engineering

Génie mécanique

Unit 1

Unité 1

Concept of Stress

Le concept de stress

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

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 reaction causes tension in the rod.

The boom and the rod are two-force members. That means each member is acted on at only two points. The lines of action of the forces at those points are equal and opposite, and they pass through both points. The forces at the joint can then be found with a force triangle.

Normal stress is calculated from the axial force in each member. For the boom, the stress is the force on the member divided by the boom’s cross-sectional area. The same method is used for the rod to determine the normal stress acting on it.

Boom and Rod Stress Analysis

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...

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 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

Analyze a boom-and-rod support structure, draw a free-body diagram, find reaction forces, and calculate compression, tension, and normal stress.

Boom and Rod Stress Analysis | 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

Boom and Rod Stress Analysis

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