Stiffness of Variable Thickness Belleville Springs

The present study reports a theoretical analysis on Belleville springs with linearly variable thickness (radially tapered disk springs). The analysis aimed at the solution of two different problems: the realization of a spring with a zone of null slope in the stiffness curve (i.e. with the possibility of having different values of the deflection at a constant load, particularly useful in some regulation processes), and the definition of a disk spring with an almost constant stress state (with the stress linearly variable from the neutral axis to the upper and lower surfaces). Based on the hypothesis of Almen-Laszlo and Curti-Orlando-Podda, the theoretical analysis give the values of the stiffness curve and the stresses as a function of the geometrical parameters and allowed both problems to be resolved, clearly with different values of the geometric parameters. In order to compare the stresses obtained for large deflections, the authors constructed a numerical model which validated the theoretical analysis.