Numerical simulation of the multi-step hydroforming process for fabricating cups with complex spatial profiles

Compared to conventional deep drawing, hydroforming demonstrates superior advantages, including the capability to form complex components with multi-directional curvatures without inducing material wrinkling or tearing, reduced stress concentrations, and more uniform strain distribution enabled by the fluid pressure forming mechanism. Additional benefits include lower tooling costs through elimination of rigid mechanical punches and enhanced product surface quality. This research employs 2D/CAE numerical simulation to analyze a six-step forming process: Step 1 – hydroforming 1, Step 2 – unloading for springback 1, Step 3 – annealing, Step 4 – die movement, Step 5 – hydroforming 2, and Step 6 – unloading for springback 2, for fabricating cup-shaped components with complex spatial geometries. The simulation accurately predicts the geometrical evolution of the blank throughout each forming stage, while enabling comprehensive analysis of stress distribution, strain development, and thickness variation under complex geometrical constraints. Process formability was evaluated against five key criteria: component geometry, Von Mises forming stress (S), residual stress (SR), equivalent plastic strain (PEEQ) distribution, and wall thickness distribution (STH). The simulation results and subsequent analysis provide a foundation for optimizing practical multi-step hydroforming processes, thereby reducing development duration, experimental costs, and material consumption. This research successfully demonstrates the capability of multi-step hydroforming to fabricate complex spatial-profile cup components with enhanced mechanical properties resulting from optimized stress-strain distribution and uniform wall thickness. The components produced through this multi-step hydroforming process meet stringent quality requirements for automotive, aerospace, and oil and gas industry applications