Strains
Change in dimensions to original dimensions is known as Strain.
Types of strains
(1) Linear Strain
(2) Bulk (or) Volume Strain
(3) Shearing (or) Rigidity strain
(1) Linear Strain
The linear strain is defined as the ratio of change in length to the original length.
When a wire or bar is subjected to two equal and opposite forces, namely pulls, at its ends, there isย an increase in the length. If the forces are tensile, the body is elongated. If the forces are compressive,ย the length is shortened in the direction of the forces. This is called the โlinear strainโ.
The linear strain is defined as the ratio of change in length to the original length. If the changeย (increase or decrease) in length is โ l โ in a wire or bar of original length L,
As the linear strain is ratio of lengths, it has no unit.
linear strain =ย Change in length/ย original lengthย
(2) Bulk (or) Volume Strain
Volume strain is defined as the ratio of change in volume to the original volume. It has also no unit.
When a force is applied uniformly and normally to the entire surface of the body, there is a changeย in volume of the body, without any change in its shape. This strain is called โbulk or volume strainโ.
If โvโ is the change in volume produced in a body of original volume โVโ,
bulk or volume strain =ย Change in volume /ย original volume
(3) Shearing (or) Rigidity strain
When a force is applied parallel to one face of a body, the opposite side being fixed, there is a changeย in shape but not in size of the body. This strain is called the shearing strain.
Solids alone can have a shearing strain. It is measured by the angle of the shear โฮธโ in radian.
