Abstract: During double reverse olsen’s forming, the galvanneal coating exfoliating is shot in multi burst mode by a camera, which shows that the exfoliating occurring time, location and amount are affected by the change of punch stroke distance. The self-developed auto rating system is used to evaluate the grades of coat exfoliating. It can be found that the compress strain of galvanneal coating has a relationship with punch stroke distance, and exfoliating behavior has a corresponding relationship with the compress strain. The exfoliating mainly occurs at the compress strain regions. The greater the strain is, the larger exfoliating amount is. The strains at different stages are stimulated by the means of FEM in order to compare actually exfoliating process. The results show the interesting rela-tionship between exfoliating and strain, that is, the exfoliating occurs only when compress strain exceeds a certain limit. With the increasing of strain, the exfoliating amount becomes greater and greater. And when strain reaches its maximum and declines, the exfoliating would stop soon after.

Key words: Exfoliating, Galvannealed sheet steel, Strain state