Study on the hydroforming technology of reinforced s-shaped bellows

Reinforced s-shaped bellows is a kind of typical reinforced metal bellows that can withstand high pressure. Hydroforming process and its simulation technology of reinforced s-shaped bellows were investigated in this paper. The hydroforming technology of reinforced s-shaped bellows is a severe plastic deformation process. Most area of the bellows is in the state of severe plastic yielding with a maximum equivalent plastic strain of 30.6%. At the same time, the wall thickness shows a linear thinning trend from wave trough to peak. The control of hydraulic pressure is a key factor of hydroforming process. The best hydroforming hydraulic pressure is 12 MPa, which is in good agreement with the designed shape. At last, the key factors affecting plastic strain and wall thickness thinning of the hydroforming process were revealed. Plastic strain and wall thickness thinning of the large-pitch bellows in the hydroforming process are obviously higher than those of the small-pitch ones. The waveform parameters directly affect the hydroforming process. However, the influences of initial wall thickness and number of layers of the bellows were not obvious. The maximum thinning rate of the bellows basically maintains around 20%.