When the bellows is subjected to more pressure in the axial direction than it can support, it will suddenly bend and lose the stability of linear shape like the compression bar or cylindrical spiral spring. This is inevitable. If the internal pressure of the bellows also exceeds a certain pressure value it can support, it will also cause instability. Experiments have proved that the destruction of bellows in engineering is mostly due to this reason. Such problems exist in both elastic seals, axial expansion compensators and metal hoses.

That is to say, the ability of bellows to withstand internal pressure generally depends on its stability. To study the stability of bellows, we can use the well-known Euler compression bar formula! Calculate its critical load.

In this way, the critical load of bellows can be solved approximately by calculation method. However, due to the following two reasons, the calculated value usually exceeds the actual value. Details are as follows.

First, because of the processing deviation of the size of the corrugated pipe and the thickness of the material, the axis of the corrugated pipe often deviates from the original axis of symmetry. In other words, there are some initial cambers on the axis of the actual bellows. For the metal hose, the non-uniformity of the mesh sleeve braiding and the non-uniformity of the strength of each part also limit the bearing capacity of the bellows.

Secondly, because the determination of the bending stiffness value in the critical load formula considers the semicircle arc of the wave crest (valley) of the bellows as the rigid connection point of the diaphragm, it is itself higher than the actual bending stiffness value.