Effects of Hydroforming Process on Fatigue Life of Reinforced S-Shaped Bellows

Abstract

Reinforced s-shaped bellows, which can withstand high pressure, is a kind of typical reinforced metal bellows. The reinforced s-shaped bellows mainly uses the hydroforming process, and the forming process is a severe plastic deformation process. The hydroforming process and its effects on the fatigue life of reinforced s-shaped bellows were discussed in the present study. Different levels of plastic strain and wall thickness thinning were detected in the hydroforming process. The maximum plastic strain can reached 32%, while the maximum wall thickness thinning ratio is 20%, which occurs on the wave peak. Mechanical characteristics of reinforced s-shaped bellows were discussed considering the effects of hydroforming process. The maximum stress appears on the upper and lower ends, which is the weak part of the structure. Fatigue life of the reinforced s-shaped bellows was analyzed based on the modified Manson-Coffin method. Mechanical properties of related materials, which can be more accurate consideration the effects of hydroforming process, were tested under the pre-plastic deformation. Fatigue life analysis of reinforced s-shaped bellows was carried out and the effects of hydroforming process were discussed. The hydroforming process will lead to a decline in fatigue life, which needs to be considered well in the structural design and analysis. Keywords: Reinforced s-shaped bellows, Hydroforming process, Fatigue life, Mechanical characteristics.