Investigation of the formability of Al1050/DC01 bi-layer sheet in incremental hole-flanging: Experimental and numerical simulation

Bi-layer metal sheets are promising for creating lightweight, multi-functional parts due to their improved formability and corrosion resistance. Understanding their formability is crucial for designing sheet metal forming processes. This study employs finite element analysis and experiments to evaluate the single-stage incremental hole-flanging (IHF) process on adhesive-bonded bi-layer sheets. Experimental tests on Al1050/DC01 sheets with various initial hole diameters were performed. Mechanical properties and adhesive damage parameters at the sheet interface were determined using standard tests and reverse finite element simulation. The VUHARD subroutine and surface-based cohesive zone model (SCZM) were used to define the hardening equations, join the sheets, and evaluate the separation in simulations. The results indicated that increasing the initial hole diameter and the vertical tool step within the specified range improved the minimum thickness in the bi-layer flange wall by 5.1% and 1.4%, respectively. Additionally, a larger tool tip radius led to higher tensile strains in the sheets and reduced flange wall thickness. Furthermore, increasing the flange wall angle from 45 to 60° caused layer separation early in flanging, while increasing the initial hole diameter from 40 to 60 mm raised the onset height of layer separation by 13.8%. © 2025 Elsevier Masson SAS