Abstract

Typically, in tube forming, the end cross section is either expanded or reduced, or the tube is bent around a solid mandrel to achieve the desired shape. To reduce the friction generated between the tube and the physical tool like mandrel the tube hydroforming process was developed. The fluid was highly pressurized to expand the tube to a desired shape. The uniform thickness and thus better formability are achieved by replacing mandrel punch with hydraulic pressure in tube hydroforming. If the axial force to deform the tube is dominant in deforming the tube, then the process is termed as hydroforging. In this paper a two-step hydroforging process is discussed. With this two-step process, firstly the tube is bulged using the low fluid pressure and then axial force was applied to deform the tube axially and circumferentially while a constant internal fluid pressure was applied to prevent the buckling. During the first step a ramp pressure is used to provide a maximum bulging without necking, then in the next step a constant same peak ramp pressure or lower is applied while compressing the tube axially. In the previous study, a straight tube was used to study the pressure requirement, bulging, buckling and deformation mechanics to create a disc shape object. In this paper, a taper tube hydroforging was studied. The same two-step process was applied to bulge the tube first and then axially deform the tube. Two tube thicknesses and three angles were studied. The pressure requirement to bulge the tube and deform the tube was investigated. The deformation mechanics was analyzed. In addition, the stress, strain, and thickness distribution were studied and reported.

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