Wrinkling analysis in shrink flanging

Flanging is a commonly used sheet forming operation to increase the stiffness of a sheet panel and/or to create the mating surface for subsequent assemblies. This paper presents an energy approach to predict the onset of wrinkling during a shrink flanging operation. A curved sheet model is established to obtain the critical buckling stress in terms of stress state, geometry properties and material properties. The predictions of wave number agree well with the experimental results. The results indicate that the sensitivity of wave number on the plan view radius (PVR) increases as PVR decreases, and the wave number decreases with the increase of flange length. The critical flange length is significantly influenced by PVR, sheet thickness and material work-hardening, and is not sensitive to material strength and anisotropy.