Multi-scale modeling of ultra-thin commercially pure titanium sheet for fuel cell bipolar plates: Plastic anisotropy and distortional strain hardening

초록

This study presents a multi-scale modeling framework to describe the mechanical behavior of a 0.1 mm-thick commercially pure titanium (CP-Ti) sheet developed for fuel cell bipolar plates. Since standardized methods for characterizing ultra-thin sheets under complex stress states are lacking, a virtual modeling approach was employed. At the grain scale, a crystal plasticity finite element (CPFE) model was constructed to incorporate the relevant slip and twinning systems, enabling prediction of responses under diverse loading conditions. Extending to the continuum scale, the CPFE results, combined with tensile data, were used to calibrate an advanced constitutive model based on the evolutionary Yld2000-2d yield function, capable of capturing anisotropic behavior. Validation against independent limiting dome height tests confirmed the predictive accuracy of the framework. The proposed approach provides a basis for simulating the forming behavior of ultra-thin CP-Ti sheets and supports precise manufacturing of bipolar plates in fuel cell systems.

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