Influence of material properties on sheet metal formability limits

It is generally recognized that the sheet metal formability increases with increasing value of strain hardening exponent. Also, the stress state and strain level have influence on the hardening behaviour. The elliptical stress locus based on Hill's yield criterion can be distorted as a result of the variation of the material properties. In order to understand the influence of the material properties and make effective use of the materials, there is a need for adopting mathematical models for analysing the interacting factors as a whole, with due consideration to the practical manufacturing process constraints. Based on the formability prediction model proposed by the authors, the analytical influence of the basic material properties like strain hardening, strength coefficient and plastic anisotropy on the forming limit stress curve has been examined. The model predictions have been compared with the published experimental data on low carbon steel.