Strain - A dimensionless quantity

Strain is a dimensionless quantity. It is the ratio of the change in length of an object to its original length. Since the change in length and the original length have the same dimensions, the ratio of these two quantities is dimensionless.

The formula for strain is:

$\epsilon_\ell =$$Change \space in \space Length \over Original \space Length$ = $\Delta \ell \over \ell$

Where, 

• $\epsilon_\ell$ = Longitudinal Strain

For example, if a metal rod is stretched by 1 cm and its original length was 10 cm, then the strain in the rod is 0.1. This is a dimensionless quantity because it is the ratio of two quantities with the same dimensions (length).

Dimensionless quantities are often used in physics and engineering because they are independent of the units used to measure them. This makes them useful for comparing quantities that have been measured in different units. For example, the strain in a metal rod can be measured in inches or centimeters, but the dimensionless value of the strain will be the same regardless of the units used.

Materials that exhibit high strain

One example of a material that exhibits high strain is a high-strain-rate superplastic ceramic. This is a type of ceramic that can undergo large plastic deformation in tension at high strain rates (the rate of change of strain with respect to time) of the order of 10-2 to 10-1 s-1. This property is useful for the shape-forming of engineering materials.

Another example is a high-strain composite structure. This is a class of composite material structures that can transition from one shape to another upon the application of external forces. They are designed to have high strain capacities compared to most conventional composite materials. They are often used in aerospace applications where low weight and high precision are required.