Shear Modulus Calculator Formula
Understand the math behind the shear modulus calculator. Each variable explained with a worked example.
Formulas Used
Shear Modulus (G)
shear_mod = elastic_mod / (2 * (1 + poisson))Bulk Modulus (K)
bulk_mod = elastic_mod / (3 * (1 - 2 * poisson))Variables
| Variable | Description | Default |
|---|---|---|
elastic_mod | Elastic Modulus (E)(GPa) | 200 |
poisson | Poisson's Ratio (nu) | 0.3 |
How It Works
Shear Modulus (Modulus of Rigidity)
The shear modulus G measures a material's resistance to shear deformation. For isotropic materials, it is directly related to the elastic modulus and Poisson's ratio.
Formula
G = E / (2(1 + nu))
This relationship means only two independent elastic constants are needed to fully describe an isotropic material. The bulk modulus K = E / (3(1 - 2*nu)) is also computed for completeness.
Worked Example
Steel with E = 200 GPa and nu = 0.3.
- 01G = 200 / (2 × (1 + 0.3))
- 02G = 200 / 2.6 = 76.92 GPa
- 03K = 200 / (3 × (1 - 0.6)) = 200 / 1.2 = 166.67 GPa
Frequently Asked Questions
What is a typical shear modulus for steel?
Structural steel has a shear modulus of about 77-80 GPa. Aluminum is about 26 GPa, and copper is about 45 GPa. Rubber has a very low shear modulus around 0.3 MPa.
When is shear modulus important in design?
Shear modulus is critical for torsion analysis (shafts, springs), bolt shear calculations, and any application where shear deformation is significant, such as short beams or sandwich panels.
Does this formula work for composites?
No. This relationship only holds for isotropic materials. Composites (fiber-reinforced plastics, wood) are anisotropic and require independent measurement of G in each principal direction.
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