Revisiting Veerman’s interpolation method

This article describes an investigation of Veerman’s interpolation method and its applicability for determining sheet metal formability. The theoretical foundation is established and its mathematical assumptions are clarified. An exact Lagrangian interpolation scheme is also established for comparison. Bulge testing and tensile testing of aluminium sheets containing electro-chemically etched circle grids are performed to experimentally determine the forming limit of the sheet material. The forming limit is determined using (a) Veerman’s interpolation method, (b) exact Lagrangian interpolation and (c) FE-simulations. A comparison of the determined forming limits yields insignificant differences in the limit strain obtained with Veerman’s method or exact Lagrangian interpolation for the two sheet metal forming processes investigated. The agreement with the FE-simulations is reasonable