Hope you are doing well. In our last lecture we have studied about stress and strain. We have learnt about basic concept behind it. Strain is a measurement quantity which is ratio of change in length to original length under loading condition. But when we stretch a body, its dimensions changes in all directions. According to it strain can be divided into two types. There are many other factors on which we can categorized strain. So today we will learn about types of strain. Hope you like it.
Let’s starts with its types.
Types of strain:
Strain can be categorized into following aspects.
According to the direction of loading:
Let’s try to learn with example. Take a rubber piece of L length, and B width. Apply a pull load on its two parallel faces along its length and observe it. The length of the rubber piece slightly increases, suppose it is ∆L. We also observed some little change in the width and height as they both decrease slightly. Suppose change in width is ∆B and change in height is ∆W. So we have observed three value of change in length in all three direction. According to it strain can be divided into two types.
The ratio of change in length to its original length in the perpendicular direction of the loading is called lateral strain. In the above example it can be represented by
The ratio of change in length to its original length in the direction of loading is known as longitudinal strain. In the above example longitudinal strain can be represent by.
According to the loading:
According to the types of loading strain can be divided into three types.
It can further divided into two types.
Strain measure under compressive loading is known as compressive strain. It tends to increase the cross section area and decrease the length of the body.
Strain measure under tensile loading is known as tensile strain. It tends to decrease the cross section and increase the length of the body.
When the shear stress is applied on a body, it tends to deform the shape of the body as shown in the figure. The change in tangential angle in the direction of the loading is called shear strain.
The ratio of change in volume to original volume under normal loading condition is known as volumetric strain.
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