Modulus of rigidity is the ratio of shear stress to the corresponding shear strain within the proportional limit of a material. Modulus of rigidity is also known as shear modulus and rigidity modulus values of materials are determined by torsional tests. Modulus of rigidity formulas are G = τ/γ and G = E/(2(1+v)). Here τ is shear stress, γ is shear strain in radians, G is modulus of rigidity, E is elastic modulus and v is Poisson’s ratio.
Shear modulus of steel, aluminum, iron, copper, titanium, brass, bronze, etc. are given in the following table in GPA and psi.
Modulus of elasticity (E): The measure of rigidity or stiffness of a material; the ratio of stress to the corresponding strain below the proportional limit. Also known as Young's modulus. The modulus of elasticity is the slope of the stress-strain curve in the range of linear proportionality of stress to strain In the stress-strain curve.