THEORY OF ELASTIC PROPERTIES OF SOLIDS
The stress-strain relationship can be found experimentally by subjecting a wire to gradually increasing loads. The extensions produced in the wire corresponding to different loads are noted down. After calculating the stress (force/unit area) and strain (relative change in length) , a graph is plotted by taking stress and strain as ordinate and abscissa respectively.
Stress: It is defined as the restoring force per unit area set up in the body, when deformed by an external force.
Strain: The ratio of change of dimensions of a body to its original dimensions is called strain.
Young’s modulus: It is defined as the ratio of normal stress to the longitudinal strain.
Bulk modulus: It is defined as the ratio of normal stress to volume strain.
Compressibility: It is defined as the reciprocal of bulk modulus.
Modulus of rigidity: It is defined as the ratio of tangential stress to shear strain.
Potential energy of a stretched wire = ½ (Force x Extension)
Potential energy/unit volume = ½ Stress x Strain
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