Shear Modulus - Explanation

Explanation

Material Typical values for
shear modulus (GPa)
Diamond 478.
Steel 79.3
Copper 44.7
Titanium 41.4
Glass 26.2
Aluminium 25.5
Polyethylene 0.117
Rubber 0.0006
Glycerin 0.000000255
Water 0.00000000016

The shear modulus is one of several quantities for measuring the stiffness of materials. All of them arise in the generalized Hooke's law:

  • Young's modulus describes the material's response to linear strain (like pulling on the ends of a wire or putting a weight on top of a column),
  • the bulk modulus describes the material's response to uniform pressure (like the pressure at the bottom of the ocean or a deep swimming pool)
  • the shear modulus describes the material's response to shearing strains (like cutting it with dull scissors).

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). In the case of an object that's shaped like a rectangular prism, it will deform into a parallelepiped. Anisotropic materials such as wood, paper and also essentially all single crystals exhibit differing material response to stress or strain when tested in different directions. In this case one may need to use the full tensor-expression of the elastic constants, rather than a single scalar value.

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