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

Si consideri una struttura costituita da un braccio e da un'asta progettata per sostenere un carico. Il boma e l'asta sono uniti da un perno e sostenuti da staffe e perni.
In primo luogo, per analizzare le varie sollecitazioni agenti sulla struttura, si staccano il braccio e l'asta dai supporti, e si disegna il diagramma a corpo libero.
Considerando le equazioni di equilibrio, vengono calcolate le forze di reazione che agiscono sul braccio e sull'asta.
Le reazioni nel punto P provocano compressione nel boma e le reazioni nel punto R causano tensione nell'asta.
Le forze esercitate sul perno Q dal braccio e dall'asta possono essere determinate utilizzando un triangolo di forza.
La sollecitazione normale derivante dalla forza assiale sul braccio viene calcolata dividendo la forza prevalente sull'asta per l'area della sezione trasversale del braccio.
La normale sollecitazione che agisce sull'asta è determinata in modo simile.

applicazione di sollecitazioni

Applications of Stress

Consideriamo una struttura composta da un braccio e un'asta progettata per sostenere un carico. Questi due componenti sono collegati da un perno e stabilizzati da staffe e perni. Il braccio e l'asta vengono staccati dai rispettivi supporti per valutare le diverse sollecitazioni imposte a questa struttura e viene disegnato un diagramma a corpo libero. Successivamente vengono identificate tutte le forze applicate, compreso il carico agente sulla struttura. Le forze di reazione esercitate sia sul boma che sull'asta vengono calcolate utilizzando le equazioni di equilibrio.

Le reazioni nel punto P provocano la compressione del boma, mentre quelle nel punto R provocano la tensione nell'asta. Entrambi i membri sono membri a due forze, cioè soggetti a forze solo in due punti. Le linee d'azione delle forze risultanti che agiscono in ciascuno di questi due punti sono uguali e opposte e passano per entrambi i punti. Le forze esercitate sull'articolazione da questi elementi possono essere determinate utilizzando un triangolo di forza. La sollecitazione normale che deriva dalla forza assiale sul braccio è determinata dividendo la forza prevalente sull'elemento per l'area della sezione trasversale del braccio. Allo stesso modo, viene calcolata la sollecitazione normale agente sull'asta.

Applicazione di sollecitazioni

Si consideri una struttura costituita da un braccio e da un'asta progettata per sostenere un carico. Il boma e l'asta sono uniti da un perno e sostenuti da staffe e ...

Education

Didattica

JoVE Core

Mechanical Engineering

Ingegneria Meccanica

Unit 1

Unità 1

Concept of Stress

Concetto di stress

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

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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