Elastic behaviour

Introduction

Elasticity is the ability of a body to resist any permanent changes to it when Stress is applied. The body regains its original shape and size when stress application ceases. The concept is applied in several fields to understand the basic engineering behind the material and its properties.

Elastic behaviour of solids

The atoms or molecules inside a solid body are displaced from their fixed points or lattice points (equilibrium positions) when it is deformed, resulting in a change in interatomic and intermolecular distances. The interatomic force tries to return the body to its original position when this force is removed. As a result, the body returns to its original shape.

Solid Mechanical Properties A model of a spring ball system can be used to visualise the restoring mechanism. The spring represents the interatomic force of attraction between the balls or atoms, while the ball represents atoms.

Deformation: is the phenomenon of a body’s shape changing as a result of applied force.

Deforming Force: The deforming force is the external force that causes deformation in the shape of the system.

Restoring force: It acts in the same way that the frictional force does in a moving body. This force acts in the opposite direction, and a body’s ability to return to its original position after an external force is removed is a property of the body.

Important Points on Solid Elastic Behaviour

Elasticity is a property of matter or a body that allows it to return to its original configuration.

Let’s try an experiment to see what we’re talking about: We can see a change in the shape and size of a rubber band when we stretch it. When the band is released, the rubber returns to its original length.

The deforming force is the force applied to the rubber band. As a result, the restoring force is defined as the force that returns the elongated body to its original shape and size.

Elasticity of solids

The shape of the solid is specific due to the placement of the molecules and atoms. However, applying force would lead to the displacement of these molecules from fixed points. Once the force is removed, they regain their shape due to the interatomic and intermolecular forces, proving their elastic limit. As long as the elastic limit is not surpassed, the solid wouldn’t change permanently. 

Elastic limit is the maximum stress or force per unit area within a solid material that can arise before the onset of permanent deformation. 

Factors affecting the elasticity 

• Stress effect – When the solid gets exposed to a high number of stress cycles, it tends to lose its elastic characteristic. Therefore, the operating stress of the material should be lesser. 
• Temperature affects – The temperature largely affects the material’s elastic characteristics. At lower temperatures, the elasticity rises, and as the temperature increases, the elasticity falls. 
• Annealing effects – Annealing is a metal heating procedure where metal is heated at an extremely high temperature and then cooled down. This technique improves the ductility and softness of the metal. 

Elastic behaviour of materials

With the removal of applied stress, the body returns to its original shape and size. Assume that a thin steel rod has been bent for some reason. When the force is applied, it should be stopped when it bends slightly. The rod never returns to its original shape. Different types of material behaviour can be seen based on the elastic and plastic nature of the materials, which can be explained using Hooke’s law.

Elasticity refers to a body’s ability to resist any permanent change caused by stress. Different materials exhibit varying degrees of elasticity. It is critical to investigate a material’s elastic behaviour. Understanding the elastic behaviour of materials in the construction of various

structures such as bridges, columns, pillars, beams, and so on are required in the majority of engineering design.

Elastic Behaviour of Materials: Applications

Elastic materials are those that can be used in places where they will be used for an extended period of time.

The following are some examples of elastic material applications:

1. Used in the construction of bridges, beams, columns, and pillars: when constructing these materials, a thorough understanding of the strength of the materials is essential.
2. Crane construction: Cranes are used to lift loads. As a result, great care is taken to ensure that the rope’s extension does not exceed the rope’s elastic limit.
3. It is critical to understand the elastic behaviour of materials used in engineering.

The bridges are constructed in such a way that they do not deform or break under the weight of heavy traffic or due to the force of a strong wind. Consider a bar with a length L and a width d. Let Y represent the young’s modulus of the bar’s material. The depression produced at the middle point of a load ‘W’ is given by, when it is attached at its middle point.

δ = WL3/4Ybd3

The machinery’s metallic parts are designed in such a way that if they are subjected to stress that exceeds the elastic limit, they will become permanently deformed.

Conclusion:

When the forces that caused the deformation are removed, the ability of a deformed material body to return to its original shape and size. Most solids exhibit some elasticity, but the force from which recovery is possible is usually limited—the material’s “elastic limit.” Stresses that exceed the material’s elastic limit cause it to yield, or flow, resulting in permanent deformation or breakage The limit is determined by the material’s internal structure; for example, steel, despite its strength, has a low elastic limit and can only be stretched by about 1% of its original length, whereas rubber can be stretched by about 1,000%. Robert Hooke was among the first to investigate elasticity, developing a mathematical relationship between tension and extension.