Hole-flangeability analyses during multistage single point incremental forming process: Variation of toolpaths with pre-cut hole geometries

Abstract

The present article inspects the combined effect of the toolpath with pre-cut hole geometry on the flange formability during the multistage single point incremental hole-flanging (MSPIHF) process. The extra deep drawing (EDD) steel and AA5083 sheets of 1 mm thickness with square and circular pre-cut holes were deformed using two different multistage square and circular toolpaths. It was found that the hole-flangeability in terms of expansion ratios and number of successful stages was varied significantly with undulation of the top edge flange profile (termed as earing) due to the synergic effects of toolpath–pre-cut combinations. Also, average flange height (AFH) and variation of flange height $(\mathrm{\Delta }h)$ were considered to quantify formability and quality of the formed flange. The concentric combinations yielded high AFH with the least $\mathrm{\Delta }h$ value, whereas the mismatch combinations exhibited a higher $\mathrm{\Delta }h$ value, indicating a prominent earing profile. Moreover, variation of the microhardness profile indicated that the plastic deformation during flanging varied significantly. Furthermore, the finite element (FE) simulations of the MSPIHF process were conducted by incorporating sheet anisotropy in terms of the Barlat Yld89 material model into the FE simulations, as well as the Bao–Wierzbicki ductile fracture model. It was found that the flange shapes, thinning profiles and flange heights were predicted with sufficient accuracy from the FE analyses.