Belleville disc springs are usually spec'd with a free height, loaded height, and loaded force. From this information you can calculate the average spring rate of a belleville spring. However, what I would like to know if if the force is actually linear (or nearly linear).
I assume it is not, but don't know what curve the force might follow. Is there an equation that can predict the force-curve (plot of force versus height) of a belleville spring given ID, OD, free height, and thickness?