Finite element analysis of sheet Hydromechanical forming of circular cup

Sheet hydroforming is a process of converting flat sheet into desired component geometry by using water pressure in a controlled manner. This paper dealt with sheet Hydromechanical forming (SHMF) of circular cup. In this process, blank is first placed on the lower die (a fluid chamber combined with draw ring) and then after sealing the blank between blank holder and draw ring, punch progresses to deform the blank. Pressure of the fluid chamber is also increased simultaneously with the punch progression. The present work endeavours to understand the effect of strain hardening exponent, anisotropy ratio and interfacial friction between blank and tools surfaces for different modes of deformation––stretching to drawing mode on sheet Hydromechanical forming of circular cups. A finite element (FE) model was developed for simulating the SHMF process using dynamic explicit, commercial code, LsDyna. The model after experimental validation used for studying the effect of above parameters on the process. The analysis reveals that higher cup depth with minimum thinning for forming dominated by stretching mode can be achieved with material of higher anisotropy ratio, strain hardening exponent by using a rough punch and effective lubrication at blank-die–blank holder interfaces. On the other hand in case of drawing as mode of deformation, thinning is influenced mainly by interfacial friction condition between blank and tool surfaces as compared to material properties.