Process window calculation and pressure locus optimization in hydroforming of conical box with double concave cavities

With the enhancement in the functional integration of components and concentration on lightweight materials, complex sheet metal parts are widely used in automobile and aviation industrial clusters. Consequently, the sheet hydroforming process has become an attractive fabricating technology for forming lightweight materials and complicated products. In this research, the hydrodynamic deep drawing (HDD) process of a composite conical box with double concave cavities was investigated through theoretical analysis, numerical simulation, and process experimentation. Furthermore, the process window diagram (PWD) was calculated using the stress analytical model combining material properties with workpiece geometrical features. The influence of cavity pressure loading locus on the forming quality of the fabricated part and the deformation behavior of aluminum alloy was explored. The forming results indicated that the initial pressure, full pressure, and loading locus are the fundamental parameters directly related to the forming quality and dimensional accuracy. For the conical part with composite features, the reasonable initial pressure value is crucial for the thickness homogeneity of the double concave characteristics, whereas the magnitude of the full pressure is vital for improving the quality of the conical feature. In addition, the optimal loading locus of the cavity pressure is characterized by two turning points, which are related to the punch corner radius, die shoulder radius, blank thickness, and angle of the conical feature.