The Influence of Material Properties on the Shape and Level of the Forming Limit Diagram

This paper presents a theoretical model for prediction of forming limit diagram (FLD) in sheet metals. The theoretical procedure is based on the work of Marciniak and Kuczynski (known as the M-K model). The influence of material properties, such as anisotropy, strain hardening and strain rate sensitivity on the shape and level of the FLD are investigated. An initial non-uniformity in thickness of a sheet metal, which is commonly assumed as a basis for the prediction of limit strains in the biaxial stretching process, is considered here as a feature of the mathematical idealization of a complex process, rather than as a material imperfection existing in a real sheet metal.