- FEMur -
Finite Element Method universal resource

Force-Displacement Relationship for
Single Degree of Freedom (SDOF) Nonlinear Spring

For a nonlinear spring, the stiffness can be broken up into two parts,

K = K_o + K_n

where

K_o = Constant (linear part)
K_n = Function of u (nonlinear part) and depends on the deformation.

when u = 0, we assume K_n = 0

Soft Spring

For such a spring the incremental force f required to produce additional incremental deformation u decreases as spring deformation increases.

Hard Spring

The incremental force required to produce a given displacement becomes increaseingly greater as the spring is deformed.

Since only about 10 - 15% of the FEM analyses in practice are nonlinear, we will put aside the nonlinear effect and concentrate on the linear analysis in our study of FEM.

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