Basic working life of bellows
The service life of bellows is the shortest working period or cycle times that can guarantee normal work when used under working conditions. The elastic sealing system composed of bellows often works under the condition of bearing more cyclic load and larger displacement, so it is of great significance to determine the service life of bellows. Because the action of bellows is different, the requirement to its service life is different also.
Because use condition is different, the service life of bellows requirement differs greatly. The life of bellows is related to the fatigue characteristics of selected materials, and also depends on the residual stress of forming bellows, the stress concentration and the surface quality of bellows. In addition, service life and the working conditions of bellows.
Bellows in the work process, the length of its life mainly depends on the maximum stress produced in the work process, generally by reducing the work displacement of bellows and reduce the working pressure to reduce the stress. In general design, it is stipulated that the working displacement of bellows should be less than half of its allowable displacement, and its working pressure should be less than half of the bellows' pressure resistance.
According to different working pressure properties, the allowable displacement of bellows is also different. Generally, when bellows only bear axial load (tension or pressure), its allowable displacement can be selected between 10% and 40% of the effective length of bellows. When bellows are subjected to transverse concentrated force, torsional moment or comprehensive force, the allowable displacement of bellows should be reduced appropriately.
Bellows will have different service life when working under different working pressure properties (constant or alternating load) under the same other conditions. Obviously, the life of bellows is shorter under alternating load than under constant load.