For axial members, the relationship between the internal force in the member and the member's deformation can be expressed as:

$$\begin{gathered} \mathrm{\delta }=\frac{\mathrm{FL}}{\mathrm{AE}}{ \\ }_{ \\ } \end{gathered}$$

where $\mathrm{\delta }=$ deformation, $\mathrm{F}=$ internal force, $\mathrm{L}=$ length, $\mathrm{A}=$ area, and $\mathrm{E}=$ elastic modulus. This relationship is termed the force-deformation relationship.