Optimization of the sheet hydroforming process parameters to improve the quality of reshaped EoL components

The reshaping of End-of-Life (EoL) components by means of sheet metal forming process has been considered largely attractive, even from the social and economic point of view. At the same time, EoL parts can be often characterized by non-uniform thicknesses or alternation of work-hardened/undeformed zones as the results of the manufacturing process. Such heterogeneity can hinder a proper reshaping of the EoL part and residual marks on the re-formed blanks can be still present at the end of the reshaping step. In a previous analysis, the authors evaluated the effectiveness of reshaping a blank with a deep drawn feature by means of the Sheet Hydroforming (SHF) process: it was demonstrated that residual marks were still present if the deep drawn feature was located in a region not enough strained during the reshaping step. Starting from this condition and adopting a numerical approach, additional investigations were carried out changing the profile of the load applied by the blankholder and the maximum oil pressure. Numerical results were collected in terms of overall strain severity and residual height of the residual marks from the deep drawn feature at the end of the reshaping step. Data were then fitted by accurate Response Surfaces trained by means of interpolant Radial Basis Functions, subsequently used to carry out a virtual optimization managed by a multi-objective genetic algorithm. Optimization results suggested the optimal value of the output variables to reduce the marks from the deep drawn feature without the occurrence of rupture.