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Local functional features in stamped components have been studied in detail due to unique advantages in saving individual parts, reducing maintenance costs, and realizing weight reduction. The present investigation focuses on the plastic forming process of the structure of multi-bosses including non-central symmetrical bosses and tri-bosses, typical local functional features. The technical route draws from a previous study on a central boss by the compression-drawing method and the extension to multi-bosses is built on a hybrid experimental–numerical approach with A1050 aluminum sheet. The results show that for the structure of non-central symmetrical bosses, radial location I of the boss structure is confirmed as a significant factor in boss forming, influencing not only the height but also the cross-section of the boss structure, and the value of I being 8 mm is proven to be the optimum solution for the given boss structure. Under the same deformation conditions, the degree of plastic deformation in the forming process of the tri-bosses structure is much higher than that in non-central symmetrical bosses due to the new cavity of the central boss and the height of the non-central boss in the tri-bosses structure is lower than that in non-central symmetrical bosses as a result of the absorption of the central boss. Moreover, fracture failure around the punch radius will occur when the maximum value of radial tensile stress exceeds the sheet tensile strength. [ABSTRACT FROM AUTHOR]

In conventional electromagnetic tube expansion (EMTE), the wall thickness of the tube decreases significantly because the electromagnetic force is mainly in the radial direction. To solve this problem, this paper proposes a new method named electromagnetic tube expansion with axial compression (EMTEAC). Besides the driving coil, we introduce a coil at each end of the tube to generate axial electromagnetic force on the tube. We use the finite element method to analyze the distribution of the magnetic flux density and the electromagnetic force generated by the three coils in series. The simulation results show that the axial electromagnetic force generated by EMTEAC is about 7 times that generated by conventional electromagnetic tube expansion, which enhances material flow when the tube is expanding. The effectiveness of the method is verified by a series of experiments. The experimental results show that EMTEAC reduces the decrease in wall thickness from 27 to 19%. [ABSTRACT FROM AUTHOR]