Experimental and Numerical Investigations on Multi-Step Stamping of 304 Stainless Steel Bipolar Plates

The stamping quality of bipolar plates in hydrogen fuel cells directly determines the overall cell performance. To address poor forming quality during bipolar plate stamping, this study proposes a multi-step simulated stamping approach and establishes mechanical models for groove flanges, fillets, and straight-edge zones. Explicit dynamic finite element analysis was employed to develop a novel multi-step stamping model incorporating varying geometries, with displacement constraints applied to simulate single-step, wide rectangular groove pre-stamping, and circular arc pre-stamping processes. The study investigated the 0.1-mm-thick 304 stainless steel sheets to determined optimal sequential stamping parameters, including stroke distance and frequency. Simulation results demonstrate significant quality improvement through pre-stamping: compared with single-step forming, wide rectangular groove pre-stamping reduces the maximum thinning rate from 35% to 27%, while circular arc pre-stamping achieves 21%, yielding minimum thicknesses of 0.073 mm and 0.079 mm, respectively. Regarding stress distribution, the techniques reduce peak stress from 873 MPa to 833 MPa (4.6% reduction) and 801 MPa (8.3% reduction) for rectangular groove and circular arc pre-stamping respectively. Experimental validation confirms strong agreement between measured thickness distributions and dimensional accuracy with simulation predictions. Systematic analysis and experimental validation demonstrate that multi-stage forming with varied pre-stamping geometries significantly enhances bipolar plate forming quality, providing critical manufacturing references for hydrogen fuel cell applications and advancing fuel cell technology development.