Bulging limit of AZ31B magnesium alloy tubes in hydroforming with internal and external pressure

Abstract

The bulging process of AZ31B magnesium alloy tubes in hydroforming with internal and external pressure (THFIEP) was simulated using the commercial finite element software Dynaform and considering plasticity theory and the yield criterion. The investigations focused on the influence of the processing parameters (the corner radius of the tool (r), the taper angle of the conical core (φ), the length of the bulging zone (l), the axial supplement of the tubes (s), the internal pressure (Pi), and the external pressure (Po)) on the maximum bulging diameter (dmax). The results showed that the dmax increased significantly with increasing r when r was less than 3 mm, and dmax remained stable with increasing r when r was larger than 3 mm. The influences of φ, l, s, Pi, and Po on the dmax were similar; the dmax first increased then decreased with increasing values of these parameters. The optimum bulging processing parameters were determined, r was 5 mm, φ was 12°, s was 10 mm, l was 37.5 mm, Pi was 34 MPa, Po was 17 MPa, and the obtained optimum dmax was 40.43 mm.