Definition - What does Shear Modulus mean?
Shear modulus, in materials science, is defined as the ratio of shear stress to shear strain. The shear modulus value is always a positive number and is expressed as an amount of force per unit area. Shear modulus' derived SI unit is the pascal (Pa), although it is usually expressed in gigapascals (GPa) or in thousands of pounds per square inch (ksi).
Shear modulus is also known as modulus of rigidity. It is normally denoted by G, but is sometimes denoted by S.
Corrosionpedia explains Shear Modulus
Shear modulus is the coefficient of elasticity for a shearing force. It is the ratio of shear stress to the displacement per unit sample length (shear strain). It can be experimentally determined from the slope of a stress-strain curve created during tensile tests conducted on a sample of the material.
The shear modulus is concerned with the deformation of a solid when it experiences a force parallel to one of its surfaces while its opposite face experiences an opposing force (such as friction). The shear modulus of metals is usually observed to decrease with increasing temperature. At high pressures, the shear modulus also appears to increase with the applied pressure. Correlations between the melting temperature, vacancy formation energy, and the shear modulus have been observed in many metals.
The harder a substance is, the higher its shear modulus value, depending on the ambient temperature when the value is measured. As the shear modulus value rises, this indicates that a much greater amount of force or stress is required to strain or deform it along the plane of the direction of the force. Strain values themselves tend to be rather small, however, in the calculations, because strain is only a measure of deformation of a solid material before it breaks or fractures. Most solids like metals stretch only a small amount before breaking down.