Failure analysis of a metal bellows flexible hose subjected to multiple pressure cycles

During pressure testing of a reinforced metal bellows flexible hose, a premature burst failure of the hose occurred. The hose was pressurized three times during testing instead of only being pressurized once, as was anticipated. Since this was an unexpected failure of the hose, an analysis was performed to further understand the characteristics of the flexible hose, which was pressurized numerous times. It was found through this analysis that by cycling the pressure on the hose and applying a pressure much greater than the yield capabilities of the hose, this combination of yielding and cycling, caused the braid to be unable to provide sufficient external support of the bellows. This led to a burst failure.

► Burst failure of a flexible metal bellows hose was analyzed.
► A finite element model was created to help understand the failure.
► Multiple cycles lead to a gap and a low coefficient of friction between the braid bellows.
► Insufficient support from the plastically deformed braid allowed the bellows to fail.