Predicting Ductile Burst in Ultra-Thin Stainless-Steel Microchannel Hydroforming: A Validated FE- Experiment Workflow and Practical Die-Design Rules

Metallic bipolar plates (MBPS) for proton exchange membrane fuel cells enable compact stacks, but forming microchannels in ultra-thin stainless steel often triggers severe localized thinning and ductile burst-especially near channel roots and corner transitions. This re-authored article presents a combined experimental-numerical workflow to (۱) validate a ۳D finite-element (FE) hydroforming model against measured channel depth and thickness distribution, (۲) identify a ductile fracture criterion that remains predictive when calibration is restricted to uniaxial tensile data, and (۳) translate damage-based insights into die-geometry guidelines. Using AISI ۳۱۶ sheet (۰.۱ mm) and hydroforming pressures of ۴۸ and ۵۵ MPa, FE predictions matched depth within ۱۰% and thickness distribution within _x۰۰۰۲_۶#۸۸۰۴;۶%. Four integral ductile criteria-Ayada, Rice-Tracey, Brozzo, and normalized Cockcroft-Latham (NCL)-were calibrated via a tensile- test-driven three-step procedure. When benchmarked against an experimentally observed burst pressure of ۵۵ MPa, NCL produced the smallest burst-pressure error (-۱۰%), outperforming the alternatives. Parametric studies showed that increasing the wall angle and corner radius delays localization and increases the achievable channel depth, whereas increasing the depth-to-width ratio (h/W) accelerates damage and lowers burst resistance. The outcome is a practical, validation-anchored design playbook for improving microchannel manufacturability in ultra- thin MBPS.

کلیدواژه ها:

Metallic bipolar plates (MBP) ، Sheet hydroforming ، Ductile fracture criteria ، Normalized Cockcroft-Latham (NCL) ، Microchannel thinning and burst prediction