Relationship To Elasticity
In general, elastic modulus is not the same as stiffness. Elastic modulus is a property of the constituent material; stiffness is a property of a structure. That is, the modulus is an intensive property of the material; stiffness, on the other hand, is an extensive property of the solid body dependent on the material and the shape and boundary conditions. For example, for an element in tension or compression, the axial stiffness is
where
- A is the cross-sectional area,
- E is the (tensile) elastic modulus (or Young's modulus),
- L is the length of the element.
Similarly, the rotational stiffness is
where
- "I" is the moment of inertia,
- "n" is an integer depending on the boundary condition (=4 for fixed ends)
For the special case of unconstrained uniaxial tension or compression, Young's modulus can be thought of as a measure of the stiffness of a material.
Read more about this topic: Stiffness
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