The potential wastage of metal bellows and other elastic elements under unit load is called the sensitivity of the element. Stiffness and sensitivity are the main functional parameters of bellows and other elastic elements, but there are two different ways to express the same use characteristics.

Bellows for the realization of pressure - force or force - pressure conversion of the elastic element, an important functional index is the effective area. The effective area is the amount of concentrated force that an elastic element can convert into when its displacement is zero under unit pressure.

Elastic elements have two kinds of working state: 1, in a certain load and displacement, and keep the load, displacement is always the same or little change, called static work. 2, the use of the load and displacement of the continuous cycle alternating changes. The element is in cyclic working state.

The mode of component damage or failure varies depending on the operating state. The instrument elastic sensitive element works in the elastic range, basically in the static working state, the service life is long, generally reaches tens of thousands to hundreds of thousands of times. The bellows used in engineering, sometimes working in the elastic-plastic range or the state of alternating stress, life is only 100 times dry, components in the cycle work must be determined working life, the number of cycles, time and frequency.

The rated life of the elastic element is the expected life of the element at the time of design. It is required that the element should not be fatigue, damage or failure during this period.

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