Name: Properties of Solid
Uploaded: 2019-07-19
Duration: 3 min 59 s
Description: Do you know which are the important mechanical properties of solids? In this video, we will discuss the solid state of matter and its different properties.

Question

Define strain and explain the types of strain.

Accepted Answer

When forces are applied on a body such that the body is still in static equilibrium, it is deformed to a small or large extent depending upon the nature of the material and the magnitude of the deforming force. The strain is a dimensionless number which is defined as the amount of deformation experienced by the body in the direction of force applied, divided by initial dimensions of the body.

We can classify the strain into three based on the nature of force causing the dimensional change. They are:

$(1)$ Longitudinal stress:- Consider the following figure.

In the figure, a cylinder is stretched by two equal forces applied normal to its cross-sectional area. The restoring force per unit area in this case is called tensile stress. If the cylinder is compressed under the action of applied forces, the restoring force per unit area is known as compressive stress. Tensile or compressive stress can also be termed as longitudinal stress. In both the cases, there is a change in the length of the cylinder. The change in the length $∆ L$ to the original length $L$ of the body is known as longitudinal strain.

$(2)$ Shear strain:-

Consider the following figure.

If two equal and opposite deforming forces are applied parallel to the cross-sectional area of a cube, as shown in figure, there is relative displacement between the opposite faces of the cylinder. The strain so produced is known as shearing strain, and it is defined as the ratio of relative displacement of the faces $∆ x$ to the length of the side $h$ .

Shear strain $= \frac{∆ x}{h} = \tan θ$

$(3)$ Hydraulic stress:

Consider a body with a random shape placed in a fluid as shown in the figure. We know that the body will be under pressure and as a result, it is compressed uniformly on all sides. Also, we know that the force applied by the fluid acts in perpendicular direction at each point of the surface and the body is said to be under hydraulic compression. This leads to decrease in its volume without any change of its geometrical shape as shown in the figure. The strain produced by a hydraulic pressure
is called volume strain and is defined as the ratio of change in volume $(∆ V)$ to the original volume $(V)$ .

Define strain and explain the types of strain.

Important Questions on Mechanical Properties of Solids

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