Research And Application Of Forming Limit Stress Diagram Of Nickel-coated Sheet

Nickel-coated sheet is a typical laminated composite plate. Nickel coating hasbeen electroplated onto the substrate to increase the resistance to erosion and wear, oradd other special functions. This type of sheet has been used in high performancebattery, vehicle parts, electric tools, and other industries. Nickel-coated sheet can notbe used until they have been formed.If we do not predict the stamping formability of nickel-coated sheet, wrinkle,crack, low utilization of nickel-coated sheet, unqualified rate, low wear resistance,low corrosion resistance and other issues will frequently appear. Therefore, how topredict the stamping formability of electrodeposited nickel coating sheet is a veryimportant topic. In the past, Forming Limit Diagram (FLD) has been used to predictthe stamping formability. However, FLD is only subjected to the linear strain path andis not applicable for nonlinear strain path, and the Forming Limit Stress Diagram(FLSD) isn’t effected by strain path.Combining FLSD curves and FLSD criterion，the theoretical research, finiteelement method and experimental verification have been used to study the stampingformability for nickel-coated sheet. Some conclusions have been summarized in thisstudy. The conclusions are as follows:(1) Hill48yield theory and dispersion instability theory have been used to derivethe FLSD of nickel-coated sheet. By referencing and analyzing the related experimen-tal data, the theoretical calculation model has been verified.(2) The FLSD curves of nickel-coated sheet with different thick anisotropy indexhave been calculated according this FLSD theoretical model. The calculation resultshows that: the substrate’s thickness anisotropy is good for the nickel-coated sheetstamping formability.(3) FLSD failure criteria has been used to simulate Nickel-coated sheet’sstamping process. Finite element simulation result shows that: if blank holding forceis too small, wrinkling failure will happen, but if blank holding force is too large,cracking failure will appear. For this type of nickel-coated sheet,1200N~1300N isthe reasonable blank holding force range.(4)The test apparatus was designed and tests have been finished, the theoreticalcalculation results and simulation consequence have been proved by test data.