Finite element analysis of ductile-to-brittle transition under hydrogen embrittlement using a cohesive zone model with a damage reduction factor derived from small punch test data

Hydrogen embrittlement (HE) critically affects the structural integrity of materials in hydrogen storage and transport. This study proposes a finite element framework combining a cohesive zone model (CZM) with a damage reduction factor derived from small punch (SP) test data. By relating trap-site hydrogen concentrations—obtained from permeation experiments— to SP energy reductions, the developed model captures ductile-to-brittle transitions more accurately. Specifically, the damage reduction factor quantifies fracture toughness loss under various hydrogen pressures and facilitates direct incorporation of experimental data into numerical simulations. In this study, the proposed finite element framework was applied to a compact tension (CT) specimen, and it was confirmed that the reduction in fracture toughness under various hydrogen concentrations can be effectively reproduced using the damage reduction factor. This approach can be extended to other materials, offering a robust method for predicting hydrogen embrittlement in diverse operating conditions and ultimately guiding safer design in hydrogen infrastructure.