Predicting forming limit of electrodeposited nickel coating based on practical stress–strain relationship

The aim of this study is to determine the practical stress–strain relationships of a nickel coating sheet so as to understand its actual forming performance. The polynomials were applied to fit the experimental stress–strain data in the coating and substrate. For the nickel coating sheet, by using the fitted practical stress–strain relationships, the forming limit diagram in the right region was precisely plotted and compared with other methods. This investigation revealed that the forming limit diagram drawn by practical stress–strain relationships is great different from others drawn by Hollomon formulae, and the anisotropy constant of the steel substrate has fairly great effects on the FLD of the coating sheet. When the substrate anisotropy constant is bigger than 1 it will favor the sheet formability, but the coating's anisotropy has no obvious influence on the FLD. The thinner nickel coating is better for its forming performance as related to the coating thickness. This work will aid the fabrication of the coating sheet and help the forming of appliances.