Determination of critical pressure in analyzing of rupture instability for hydromechanical deep drawing using advanced yield criterion

Hydromechanical deep drawing (HMDD) is a sheet hydroforming process to produce complex workpieces with high drawing ratio. Fluid pressure used during the forming process is one of the most effective parameters in this process in which increasing critical pressure causes to rupture occurrence. Since the material properties in different angles respect to the rolling direction affect the amount of critical pressure, it is important to develop an appropriate theoretical model for prediction of plastic behavior of material with high precision. In this paper, a theoretical model based on BBC2008 yield criterion including 8 and 16 parameters (8p and 16p) is developed to determine critical pressure in HMDD process. With applying uniaxial and equi-biaxial tensile tests and optimizing an error-function by using Levenberg-Marquardt method, the parameters of BBC2008 yield criterion can be determined. Low carbon St14 steel sheets are utilized for experimental samples to verify critical pressure obtained from the proposed theoretical model. BBC2008 model with 8p and 16p is compared with Barlat-Lian 1989 and experiments. The results show that BBC2008-16p yield criterion can provide a more precise model of material behavior in planar anisotropy properties, while BBC2008-8p yield criterion have a better prediction of rupture occurrence in HMDD process.