When stamping galvanized sheet, the formability usually decreases for failure of zinc coating. In this paper, formability of galvanized sheet was firstly researched by Erichsen experiment. The results show that zinc coating has lost efficacy when the cup arrives the value of Erichsen depth (ED). Then finite element analysis was used, it puts the zinc coating and the substrate in connection by using automatic-surface-to-surface-tiebreak and sets up a series of forming limitation diagrams (FLD) of galvanized sheet and of zinc coating under different punch strokes. Then depth of the cup when zinc coating reaches critical state was got, which decreased about 5%-10% compared with bare sheet. At last, failure mechanism of zinc coating was discussed, the reason is that material of zinc coating is soft and the friction leads to pulverization and exfoliation of zinc coating. The simulation results are consistent with the Erichsen experiment ones. Conclusions of this paper can provide theoretical guidance for the stamping process design of galvanized sheet.
A finite-element analysis of critical-state models for type-II superconductivity in 3D