Shear Stress, Shear Modulus
Index
The diagram shows a force, F, applied tangientially to a surface of area, A0. The shear stress, t, produced by this configuration is given by: t = (F/A0). If the material is linear elastic, the effect of this applied shear stress in the elastic range will produce a shear strain, g = tan q. The stress and strain are coupled through the Hookian elastic relationship, t = Gg, where G is the shear modulus of the material.

For an isotropic elastic continuum, the shear modulus, G, is related to Young's modulus, E, and Poisson's ratio, n: G = E/2(1 + n)

From: Callister, 
"Materials Science and Engineering," 
Wiley (1994)