Optimization of bi-layered Y-shaped tube hydroforming using RSM

In this study, the use of response surface methodology (RSM) to design and optimize the primary process parameters for the hydroforming of bi-layered Y-shaped tubes with a new parallel backward punch is reported for the first time. The effects of the main factors such as shaping pressure, left and right axial feed, backward punch displacement, and friction coefficient of the loading path on the forming performance are analyzed, and the ultimate fillet radius and the maximum contact area between the top of the branch pipe and the backward punch combined with the maximum thinning rate of the inner and outer tubes are introduced as the experimental evaluation indexes for the first time, and the effective evaluation indexes, perturbation diagrams, optimized evaluation criteria, and the interaction effects of different experimental factors based on the principal influencing factors are analyzed and optimized to screen the process parameters of the optimal loading path. Finally, the simulation results under the optimal loading path are compared with the experimental data, revealing an error within 5%. This indicates that the proposed loading path optimization method for hydroforming of bi-layered Y-shaped tubes exhibits high accuracy and excellent feasibility.