Abstract
Manufacturing of irregular bellows with small corner radii and sharp angles is a challenge in tube hydroforming processes. Design of movable dies with an appropriate loading path is an alternative solution to obtain products with required geometrical and dimensional specifications. In this paper, a tube hydroforming process using a novel movable die design is developed to decrease the internal pressure and the maximal thinning ratio in the formed product. Two kinds of feeding types are proposed to make the maximal thinning ratio in the formed bellows as small as possible. A finite element simulation software “DEFORM 3D” is used to analyze the plastic deformation of the tube within the die cavity using the proposed movable die design. Forming windows for sound products using different feeding types are also investigated. Finally, tube hydroforming experiments of irregular bellows are conducted and experimental thickness distributions of the products are compared with the simulation results to validate the analytical modeling with the proposed movable die concept.
Highlights
Tube hydroforming is a forming technique that utilizes a high internal pressure to bulge the tube material to fit the die shape and obtain the desired product shape
Conventional regular metal bellows with multiple convolutions are usually manufactured by hydraulic bulging and die folding
This kind of irregular bellows can only be made by hydraulically bulging the tube into the desired shape under an irregular closed die set
Summary
Tube hydroforming is a forming technique that utilizes a high internal pressure to bulge the tube material to fit the die shape and obtain the desired product shape. Tomizawa et al [10] proposed an axial movable die concept in a hydroforming process to obtain a small corner radius and a uniform thickness distribution of the formed product with a lower internal pressure. The loading path was well designed and controlled so that a corner radius of 6 mm was formed with a low internal pressure of 18 MPa. Hwang et al [12] used finite element codes LS-DYNA and DYNAFORM to analyze the plastic flow pattern of a tube hydroformed into a product with large expansion ratio and eccentric axes. Hwang et al [12] used finite element codes LS-DYNA and DYNAFORM to analyze the plastic flow pattern of a tube hydroformed into a product with large expansion ratio and eccentric axes They proposed a movable die set concept to enhance the forming capacity of tube hydroforming technology. Experiments of hydroforming are conducted to validate the proposed novel movable die concept and loading paths
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