: HDD process is the most well known and greatly used method for production of a broad spectrum of parts in simple home products up to aircraft complicated parts. Higher economic efficiency and flexibility can be achieved by using this process, the part quality and thickness distribution obtain by using HDD process is better than CDD process, this is due to the blank compressed to the punch surface which is caused by counter pressure profile. Wrinkling is one of the major defects that occurs in sheet metals formed by CDD process. Wrinkling is a kind of buckling phenomenon that prevents from forming of the sheet. During the deep drawing of axisymmetric cups, the value of the blank holder force (BHF) is an important factor to eliminate wrinkling, and also not to cause fracture. If the BHF is low, wrinkling may occur. And also if BHF is too high, fracture will occur. If a constant BHF is used, then the BHF should be kept within a certain operating range to obtain the desired depth. Considering the fact that different modes of failure becomes important at different punch displacement during the deformation, the BHF does not have to be kept constant throughout the deformation. Wrinkling at the beginning of the deformation due to large compressive stresses in the flange of the cup will occur. Furthermore, as the deformation progresses radial stresses buildup in the wall of the cup and fracture may occur due to an excessive amount of stretching. Therefore, the BHF should be varied during the forming process instead of being kept constant. In this project, at first a theoretical analysis has been done then, and the effect of hydrostatic pressure on wrinkling and rupturing in HDD process of hemispherical cups was investigated numerically. Beginning of the stage of wrinkling and growth of wrinkles in the flange area is considered and Hill’s yield function for simulation of HDD process was used. Furthermore, forming limit diagram (FLD) damage criterion has been used for determining rupture instability. The results of CDD process and HDD process compared and height of wrinkles in the flange area and major and minor strain distribution for HDD and CDD processes determined. In the next section the effect of tool design variables (such as punch-die clearance and friction factor and etc..) on HDD process of cylindrical cups was discussed. And in the final section an numerical investigation on control of the BHF in HDD process is carried out .Also a profile for the BHF with using an new method based o punch force is proposed. Finite element analysis (FEA) codes could be used to understand the deformation behavior of a material during the forming process and therefore Abaqus/Explicit was used for simulations of processes. Key Words: Hydromechanical Deep Drawing, Wrinkling, Finite Element Method, Blank Holder Force
