Influence of pre-bulging and forming pressure on the formability of copper-stainless steel sheets in double-layer hydroforming

• A dual-layer hydroforming method is proposed and optimized for forming deep conical copper parts to overcome failure issues observed in single-layer hydroforming of thin copper sheets with severe deformation. • A validated and accurate 3D FEM model is developed with an average error of less than 5% compared to experimental results. • Key process parameters (forming pressure, pre-bulging pressure, etc.) are systematically analyzed and optimized using numerical simulations and Design of Experiments (DOE). • Achieves a maximum Limiting Drawing Ratio (LDR) of 2.38 , improves thickness distribution uniformity, and enhances conformity to punch geometry. • Provides a strong theoretical and practical foundation for efficient forming of complex copper components in industrial applications. Efficient forming of deep conical copper components with a limiting drawing ratio (LDR) greater than 2.0 remains a challenge due to severe local thinning and edge tearing. This study introduces a double-layer hydroforming technology, in which a copper sheet is supported by a stainless-steel layer to enhance deformation uniformity and prevent failure. A three-dimensional finite element model, verified by experimental results, demonstrates that the proposed technology significantly improves thickness distribution and geometric accuracy compared with conventional single-layer hydroforming. The optimized process achieves an LDR of 2.38, with a deviation between simulation and experiment of less than 5%. The proposed technology shows high application potential and scalability for producing thin, high-precision components in electronics, energy, and aerospace industries.