When the bellows is subjected to the axial pressure that exceeds its support capacity, it will suddenly bend and lose the stability of linear form, just like the compression bar or cylindrical spiral spring. This is inevitable. If the internal pressure that the bellows bears also exceeds a certain pressure value that it can support, instability will also occur. Experiments have proved that the failure of bellows in engineering is mostly caused by this reason. Such problems exist in 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 quote the well-known Euler compression bar formula! Calculate the critical load.

In this way, the critical load of the bellows can be approximately solved by the 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 in the dimension and material thickness of the corrugated pipe, the axis of the corrugated pipe often deviates from the original axis of symmetry. In other words, there is some initial bending on the axis of the actual bellows. For the metal hose, the non-uniformity of the mesh sleeve weaving and the inconsistency of the strength of each part also limit the bearing capacity of the corrugated pipe.

Second, because the determination of bending stiffness value in the critical load formula is based on considering the semicircular arc of the wave crest (valley) of the bellows as the rigid connection point of the diaphragm, it is higher than the actual bending stiffness value.