Experimental and Numerical Study of Thickness Distribution and Convolution Height in Hydroforming process of Metallic Bellows

Metallic bellows have many applications in various industries such as oil and gas industries. In recent decades, various processes such as mechanical and hydroforming methods for production of bellows have been proposed. Hydroforming process is one of the best methods for manufacturing of metallic bellows with expected characteristics. In this paper, hydroforming process of metallic bellows for AISI 304 stainless steel has been investigated experimentally and numerically. For this purpose, effects of some process parameters such as internal pressure, die stroke, radius of die corner, friction coefficient, thickness and length of tube on metallic bellows formability has been studied. The results show that with an increase in the internal pressure and also die stroke length, the height of convolution is increased and the thickness of outer diameter of bellows is decreased. In addition, the other numerical investigations show that by reducing in the friction coefficient and also initial thickness and length of tube, convolution height is increased and the thickness of a point positioned on convolution crown is decreased. It should be noted that a good agreement between the results of experimental work and numerical simulations were obtained that show a good precision in the performed numerical simulations.