Strain is the measure of deformation in a material due to applied stress. It is defined as the ratio of change in dimensions to the original dimensions. Strain is a dimensionless quantity and is classified into tensile strain compressive strain or shear strain based on the nature of deformation.
Chapter 8 Mechanical Properties of Solids focuses on the response of solid materials to external forces. It covers stress strain elasticity and plasticity along with their interrelations. Important concepts include Young’s modulus bulk modulus shear modulus and Poisson’s ratio. These principles are vital for understanding material strength and engineering applications.
Definition of Strain:
Strain is a measure of deformation, which gives the displacement between the particles in a material body. Strain is defined as the ratio of change in dimension to the original dimension of the material. In mathematical terms, strain (ε) is expressed as:
ε = ΔL / L₀
Here, ΔL represents the change in length and L₀ represents the original length.
Why Strain Has No Units and Dimensions:
Strain is a dimensionless quantity because it is a ratio of two lengths (change in length to original length), which means that both numerator and denominator have the same units. Hence, the units cancel out, and one gets a unitless value. Since it is dimensionless, therefore it has no dimensions in the context of physical measurement.
Different Types of Strain:
1. Tensile Strain: It takes place when a material is stretched. It is defined as the change in length divided by the original length (elongation).
2. Compressive Strain: It takes place when a material is compressed. It is defined as the change in length divided by the original length (shortening).
3. Shear Strain: It is that strain which arises due to shear forces applied on a material. It is defined as the change in angle between two lines originally at right angles, expressed as the ratio of lateral displacement to the original length.
4. Volumetric Strain: It is the change in volume per unit original volume of a material, occurring under uniform pressure.
These types of strain are important for understanding how materials respond to various forces and deformations.
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