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Mechanical Properties of Solids
A solid is defined by its size and shape. A force is necessary to change (or deform) the shape or size of a body. When you gently pull the ends of a helical spring, the length of the spring rises somewhat. When you remove the spring’s ends, it returns to its natural size and shape. Elasticity is a property of a body in which it tends to restore its original size and shape when the applied force is removed, and elastic deformation is the deformation produced by this property. When you apply force to a lump of putty or mud, however, it has little chance of regaining its original shape, and it becomes permanently distorted.
In engineering design, the elastic behaviour of materials is critical. For example, while designing a building, understanding the elastic properties of materials such as steel, concrete, and others is critical. The same may be said for bridges, autos, ropeways, and other structures.
Elasticity
When the forces that caused the deformation are eliminated, elasticity refers to the ability of a distorted material body to return to its original shape and size. Elastic behaviour (or response) is a term used to describe a body that has this flexibility.
Most solid materials exhibit elastic behaviour to some degree, but the size of the force and the resulting deformation within which elastic recovery is possible for any specific material is limited. This limit, known as the elastic limit, is the greatest stress or force per unit area that can occur within a solid material before irreversible deformation occurs.
Consequences of Elastic Limit
Most solid materials exhibit elastic behaviour to some degree, but the size of the force and the resulting deformation within which elastic recovery is possible for any specific material is limited. This limit, known as the elastic limit, is the greatest stress or force per unit area that can occur within a solid material before irreversible deformation occurs.
The elastic limit varies greatly depending on the type of solid being evaluated; for example, a steel bar or wire may only be stretched by roughly 1% of its original length, whereas strips of certain rubberlike materials can be stretched by up to 1,000%. Steel, on the other hand, is significantly stronger than rubber because the tensile force necessary to achieve maximum elastic extension in rubber is far lower (by a factor of roughly 0.01) than that required in steel. Many solids in tension have elastic characteristics that fall between these two extremes.
Elastic Behaviour of Solids
Any solid substance that is subjected to an external force is deformed, and the atoms or molecules that make up the body are shifted from their original positions, disrupting the condition of equilibrium.
The displacement causes the fixed points to vary, resulting in changes in interatomic and intramolecular distances. As a result, deformation can be defined as a change in the structure of any object caused by the action of a force. The deforming force is the force that causes the shift in the displacement of these particles.
We know that every force has an equal and opposite force operating against it. The restorative force, which acts in the opposite direction, opposes the deforming force. When the deforming force is removed, this force forces the body back to its original position.
The spring ball system is made up of balls that represent atoms and springs that represent the forces that act between them.
Elastic Modulus
We know that when an elastic material is distorted by an external force, it maintains an internal resistance to resist the deformation and returns to its original state once the external force is removed.
The various types of elastic moduli are as follows:
- Young’s Modulus: Young’s modulus is a property of an object that allows it to endure changes in its length when longitudinal tension or forces, such as compression, are applied. The longitudinal stress divided by the object’s strain equals the Young’s modulus. The letter Y symbolises Young’s Modulus.
- Shear Modulus: The shear modulus, also known as the Modulus of Rigidity, is the ratio of shearing stress to shearing strain. The letter ‘G’ symbolises Shear Modulus.
- Bulk Modulus: The ratio of hydraulic stress to associated hydraulic strain is known as bulk modulus. The letter ‘B’ symbolises Bulk Modulus.
Application of Elastic Behaviour of Solids
A slingshot deforms when stretched. When the force is removed, it reverts to its original shape. However, imagine trying to bend a thin steel rod. You bend it slightly and then let off the pressure. Is it possible for the rod to restore to its original shape? It doesn’t, it doesn’t, it doesn’t. The elastic and pliable characteristics of the material cause this difference in behaviour.
The rubber strip on the slingshot is incredibly bendable. Elasticity refers to a body’s ability to withstand irreversible change when stressed. The body returns to its original shape and size once the stress is released. The degree of elasticity in various materials varies. The elastic behaviour of a material is crucial to understand. Understanding material elastic behaviour is required in almost every engineering design.
In the construction of various structures such as bridges, columns, pillars, and beams, to name a few. Understanding the strength of the materials used in construction is crucial.
The elasticity of materials is primarily considered and learned in three scenarios:
- Thickness of the Steel Rope used in Cranes
- Design of the bridges
- Maximum Height of the mountains
Conclusion
We know that each atom or molecule in a solid is surrounded by other atoms or molecules. Interatomic or intermolecular forces hold them together and keep them in a stable equilibrium position. The atoms or molecules in a solid are displaced from their equilibrium positions when it is deformed, resulting in a shift in interatomic (or intermolecular) distances. Interatomic forces tend to drive them back to their former places when the deforming force is removed. As a result, the body reverts to its natural size and shape. A model of a spring-ball system, as shown in Fig, can be used to visualise the restoring mechanism. Atoms are represented by the balls, while interatomic forces are represented by the springs.
