spring between two surfaces

Hello everybody,



I am trying to define a spring between two surfaces but I could not, is there is a way to use « thin elastic layer « to model such spring ? However I could not select the surfaces I need, the condition for thin elastic layer is identity pair, moreover I am not sure if it suitable for modeling springs.

Also is there a way to define a pretension in the spring?



I tried to defined the spring force by F=K*(u2-u1), working on the one side of the spring and same for the end of the spring, where u2-u1 is the change of spring length, however I could not find the correct name for the normal displacement of the spring terminal surfaces in order to enter them in the equation.



Best regards and thanks in advance,

Ghalib