Prediction of plastic wrinkling using the energy method

The prediction and prevention of wrinkling during a sheet metal forming process have been challenging issues on the design of part shape, die geometry, and processing parameters. In an effbrt to provide a reliable and efficient tool to assess the onset of wrinkling, analytical models for flange wrinkling and straight side-wall wrinkling are presented here. Using a combination of energy conservation and plastic bending theory, the critical buckling wavelength and stress are calculated as functions of the boundary conditions (displacement constraint and binder pressure). Comparisons between the numerical and experimental results are given for both cases and excellent agreement is obtained.