If the application involves large numbers of deflection cycles, i.e. 'dynamic' application, or if the required forces or deflections are of a critical nature, we strongly recommend that you select from the range of disc springs that conform to the DIN 2093 specification.
From the range available, select the largest possible disc spring compatible with the desired characteristics. This will assist in maintaining the lowest possible stresses, thus enhancing the fatigue life, and in the case of stacked columns the greater deflection offered by the larger diameter springs will ensure the shortest possible stack length.
For static, or dynamic applications, select a disc spring that at 75% of its total available deflection offers the maximum force and/or deflection required. Between 75% deflected and the 'flattened' position, the actual force/stress characteristics become considerably greater than those calculated.
As a result of manufacturing processes, residual tensile stresses occur at d , the upper inside diameter edge, which will revert to normal compressive stresses when the disc spring is deflected by up to approximately 15% of its total deflection.
The fatigue life in applications involving large numbers of cyclic deflections, will be drastically reduced by these stress reversals. For this reason alone, it is important that disc springs used in dynamic applications are pre-loaded to a minimum of 15% of their total available deflection.