Belleville washer
Disc springs have a number of advantageous properties compared to other types of springs:[4] Thanks to these advantageous properties, Belleville washers are today used in a large number of fields, some examples are listed in the following.
In the arms industry, Belleville springs are used, for instance, in a number of landmines e.g. the American M19, M15, M14, M1 and the Swedish Tret-Mi.59.
The target (a person or vehicle) exerts pressure on the Belleville spring, causing it to exceed a trigger threshold and flip the adjacent firing pin downwards into a stab detonator, firing both it and the surrounding booster charge and main explosive filling.
Some makers of bolt action target rifles use Belleville washer stacks in the bolt instead of a more traditional spring to release the firing pin, as they reduce the time between trigger actuation and firing pin impact on the cartridge.
[5] Belleville washers, without serrations which can harm the clamping surface, have no significant locking capability in bolted applications.
By torquing their associated bolts to provide a specific gap between sets of washers placed with "high ends" facing each other, a change in relative moisture content in the propeller wood will result in a change of the gaps which is often great enough to be detected visually.
As propeller balance depends on the weight of blades being equal, a radical difference in the washer gaps may indicate a difference in moisture content – and thus weight – in the adjacent blades.
In the aircraft and automotive industries (including Formula One cars[7][better source needed]) disc springs are used as vibration-damping elements because of their extremely detailed tuning ability.
The Cirrus SR2x series of airplanes, uses a Belleville washer setup to damp out nose gear oscillations (or "shimmy").
Stacking in the same direction will add the spring constant in parallel, creating a stiffer joint (with the same deflection).
Mixing and matching directions allow a specific spring constant and deflection capacity to be designed.
On the other hand, if n washers are stacked in series (facing in alternating directions), standing the load, the deflection is equal to n times that of one washer while the load to apply at the whole stack to obtain the same deflection of one disc spring has to be that of a single disc spring divided by n. In a parallel stack, hysteresis (load losses) will occur due to friction between the springs.
The hysteresis losses can be advantageous in some systems because of the added damping and dissipation of vibration energy.
As previously said, Belleville washers are useful for adjustments because different thicknesses can be swapped in and out and they can be configured to achieve essentially infinite tunability of spring rate while only filling up a small part of the technician's tool box.
They are ideal in situations where a heavy spring force is required with minimal free length and compression before reaching solid height.
The downside, though, is weight, and they are severely travel limited compared to a conventional coil spring when free length is not an issue.
These contact flats improve definition of the point of load application and, particularly for spring stacks, reduce friction at the guide rod.
The result is a considerable reduction in the lever arm length and a corresponding increase in the spring load.
Starting from 1936, when J. O. Almen and A.Làszlò published a simplified method of calculation,[10] always more accurate and complex methods appeared also in order to include in calculations disc springs with contact flats and reduced thickness.
So, although today there are more accurate methods of calculation,[11] the most used are the simple and convenient formulas of DIN 2092 as, for standard dimensions, they produce values which correspond well to the measured results.
For what concerns disc springs with contact flats and reduced thickness it has to be said that a paper published in July 2013, demonstrated that the
equation as defined inside the standard norms is not correct as it would result in every reduced thickness being considered right and this is, of course, impossible.
Counting from one end of the stack, group by the number of adjacent washers in parallel.
washers is defined by the integer partition function p(n) and increases rapidly with large
