Comparison of Sheared Edge Zones Developed in Electromagnetic and Quasistatic Dieless Perforation

Electromagnetic (EM) perforation is a high-strain-rate shearing process of making holes in the workpiece by using an electromagnetic force. This process overcomes the disadvantages of conventional or quasistatic processes. In this work, the comparative study of the quality of holes perforated by the EM dieless perforation process and quasistatic dieless perforation process has been carried out and the differences are reported. This study allows one to understand the physical phenomena that happen during the perforation by the pointed and concave punch as well as the type of failure like the formation of petaling, plugging and softening or hardening of the material. The sheared edges are characterized using microscope, scanning electron microscopy (SEM) and microhardness analysis studies. Among interesting observations, it has been noticed that the smooth sheared depth, rollover depth, burr height and fracture depth are more in quasistatic dieless perforation. No significant change in hardness is observed in the case of quasistatic perforation, while in EM perforation, more than 50% increase in hardness is observed. The SEM observation has revealed that in both the perforation cases, ductile dimple growth is the prominent failure mode. The results obtained during this study show the capability of electromagnetic perforation to obtain perforated holes with better surface finish and material properties over the quasistatic perforation process.