Effect of key process parameters on hydrostatic forming of unwelded sheet-metal Pairs: experimental investigation and parameter sensitivity analysis

Hydrostatic forming has emerged as a versatile technique for producing thin-walled tubular components due to its enhanced geometric flexibility and controlled material deformation. Forming unwelded sheet-metal pairs, however, presents additional challenges compared with welded configurations, as it requires careful management of individual sheet deformation and pressure retention to ensure component compatibility. This study presents an experimental investigation into the hydrostatic forming of unwelded sheet pairs, focusing on the influence of critical process parameters — namely, forming pressure and blank-holder pressure — on deformation characteristics and thinning behavior. The results reveal stable formability and compatible deformation between the two halves of the component produced in a single cycle. Graphical and quantitative analyses demonstrate that higher forming pressures increase overall deformation, while blank-holder pressure critically affects thinning distribution and pressure transmission across the sheet pair. These findings provide a foundation for predicting forming outcomes, optimizing process parameters and enhancing control strategies in thin-walled sheet forming, highlighting the interplay between applied pressure fields and material response in a hydrostatic environment.