Forming various shapes of tubular bellows using a single-step hydroforming process

Tubular bellows are one of the most efficient energy-absorbing elements for various automotive systems. The conventional manufacturing of metallic tubular bellows consists of a four-step process: (1) deep drawing, (2) ironing, (3) tube bulging, and (4) folding. In the present study, a single-step tube hydroforming process is used to make prototype tubular bellows with simultaneous control of the internal pressure and the axial feed. A number of prototype tubular bellows were formed with the use of various hydroforming die shapes, such as rectangular, circular, and triangular. For each shape, the hydroformability of the tubular bellows, in conjunction with the forming process, was evaluated. The effect of the friction was also investigated. Good lubrication is an effective method for improving the hydroformability of metallic tubular bellows. The present study shows that a single-step hydroforming process can be used to form tubular bellows with various shapes.