Distortion

The state of deformation including change of shape without any modification of volume is described as Distortion. Though distortion might be introduced in several ways let us assume a simple case. While shear stresses are applied on a solid as illustrated in Figure, we discover that angular deformations are introduced. The angular strain or change in angle generated is called shear strain mention by γ (Greek gamma) and its magnitude is expressed in radians. The ratio of the applied shear stress & the shear strain generated by it is described as Rigidity Modulus or Shear Modulus of the material, that means

Rigidity Modulus, G = Shear Stress (τ)/ Shear Strain (γ)

                                                            Figure : Shear Stress and Shear Strain

We have until now defined four elastic constants, that is, Young's Modulus (E), Bulk Modulus (K), Poisson's Ratio (υ), and Shear Modulus (G). Afterwards we will learn that these four are not independent constants, but are associated to each other. We might show that there are only two independent elastic constants & the other two are dependent on them.