Phenomenological modeling of galvannealed coating flaking under various deformation modes

초록

The flaking of zinc coatings during the cold forming of galvannealed (GA) steel sheets poses significant challenges in industrial manufacturing, leading to die damage and reduced corrosion resistance. Unlike existing tribological or forming-limit diagram approaches, this study proposes a stress triaxiality-dependent flaking model that explicitly accounts for the compressive buckling mechanism observed in various deformation modes. Mechanical tests covering a wide range of stress triaxialities were conducted on four GA steels with varying annealing conditions. Flake area evolution was quantified using a tape-test method. The results reveal a strong dependence on deformation mode; while positive triaxiality modes resulted in surface cracking without coating loss, negative or near-zero triaxiality induced significant flaking via coating buckling. Salt spray testing further confirmed that this flaking is significantly more detrimental to anti-corrosion performance than tensile cracking. Based on these findings, a phenomenological model utilizing a triaxiality-dependent Weibull distribution was formulated to predict the accumulated flake area as a function of equivalent plastic strain. The model was validated against large-radius bending and uniaxial tension tests. The model was applied to strip drawing simulations, demonstrating its capability to predict galling zones induced by self-generated flaking debris. © 2026 Elsevier Ltd

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