Stiffness

''For pain and/or loss of range of motion of a joint, see joint stiffness

Stiffness is the resistance of an elastic body to deflection by an applied force. The stiffness k of a body that deflects a distance δ under an applied force P is:

[k=\frac ]

Stiffness is typically measured in newtons per metre.

As both the applied force and deflection are vectors (respectively P and δ), in general their relationship is characterised by a stiffness matrix, k where:

P = k δ.

The deflection can, in general, refer to a point distinct from that where the force is applied and a complicated structure will not deflect purely in the same direction as an applied force. The stiffness matrix enables such systems to be characterised in straightforward terms.

The inverse of stiffness is compliance, typically measured in units of metres per newton.

Stiffness

See also