To introduce nonlinear membranes in AquaSim, one establishes tables where the relation between axial force and strain is defined. Such tables are possible to implement for membrane components, type Normal.

Having a linear material behaviour, the relation between force and strain may be as the leftmost graph in the figure below. When the material behaviour becomes nonlinear, the relation may look like the rightmost graph.

Let us exemplify a nonlinear relation with the table below.

Axial Force [N]	Strain [m/m]
-100	-0.1
0	0
100	0.1

For the individual rows in the table, you will have the following relation between strain and elongation:

$$ {\Delta L = L_0 \cdot \varepsilon , [\text{m}] } $$

where L₀ is the initial undeformed length of the membrane, and ε is the strain. If we consider the first row in the table, then an axial fore (tension) of 100 N will elongate the membrane 0.1 meters per meter. Assuming the membrane panel to be 10 meters, the elongation of the membrane is \( \Delta L = 10 , \text{m} \cdot 0.1 , \text{m/m} = 1 , \text{m} \)