A hybrid experimental and numerical analysis of tailored seam single and double clinched joint using the electromagnetic forming process

Abstract

Clinching is a cold forming process that creates a mechanical interlock between sheets, eliminating the need for additional fasteners. Formability of tailored clinched sheets has always posed significant challenges due to the inherent limitations of the cold interlock joining process. It's highly subject to loosening and weakening of clinch joints during the forming process. To overcome this process, the rate-forming process plays a crucial role. Electromagnetic forming (EMF) is a high-velocity forming process suitable for conductive materials, such as aluminium alloys. This study compares the formability of tailored single- and double-clinched joints (TCS) produced using the EMF process. Initially, experiments were conducted to determine the discharge voltage threshold up to the fracture limit of the workpiece. Shear tests were then performed on both single and double clinched specimens, and the microstructure of the resulting joints was examined. LS-DYNA simulation software was used for the numerical analysis of clinching and the EMF process of plain (non-clinched) sheet. Through numerical analysis, parameters involved in clinching and the EMF process were investigated and compared. Results revealed that the double-clinched joint (DCJ) exhibited a 142% higher shear strength compared to the single-clinched joint (SCJ) during lap shear testing. Additionally, the formability and fracture resistance (based on discharge voltage of EM machine) were 93% and 60% higher, respectively, in the DCJ. The novelty of this work lies in the intentional displacement of the clinched joint from the center of the lapped sheet and its influence on the overall strength and formability of the workpiece. This aspect is explored through a comprehensive experimental and numerical study of high-strain-rate fracture behaviour and formability enhancement in tailored single- and double-clinched AA1100 aluminium sheets. © 2026 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.