Internal pressure and counterpunch action design in Y-shaped tube hydroforming processes: A multi-objective optimisation approach

In sheet metal forming most of the problems are multi-objective problems, generally characterised by conflicting objectives. A classical approach to investigate such kind of problems is focused on a combination of multiple objectives into a unique objective function to be optimised. Actually, in metal forming processes optimisation two main phases have to be developed in order to reach an optimal solution: the former is the modelling phase (definition of the design variables and objective function) and the latter concerns the computational aspect (numerical simulations or experiment to be developed). In this paper, an integration between numerical simulations, response surface methodology and Pareto optimal solution search techniques was applied in order to design a complex Y shaped tube hydroforming. In particular, the calibration of internal fluid pressure and counterpunch action was investigated with the aim to achieve three different quality objectives: minimization of thinning, reduction of underfilling and accuracy of the final fillet radius at the bulge zone corner.