A Numerical Model to Study the Hydrogen Embrittlement Effect

Hydrogen embrittlement is a complex phenomenon which can affect steel structures used for different applications, as pipelines, storage vessels and fuel cells. In literature, many works have been proposed to study hydrogen embrittlement, but a unified solution to fully understand the phenomenon is still not defined.Aim of this work is to develop a reliable numerical tool to estimate the influence of hydrogen on the fracture toughness of steel. A 2D finite element model of a C(T) specimen is developed using a zero-thickness layer of cohesive elements to simulate crack propagation. Starting from an initial model without hydrogen, the embrittlement effect is simulated by modifying the traction- separation law (TSL) of cohesive elements, according to relationships taking into account hydrogen diffusion at the crack tip and plastic strain. Parameters of TSL are calibrated in order to reproduce the experimental toughness data. The model can be very useful to understand, from the viewpoint of fracture mechanics, the hydrogen embrittlement phenomenon in the studied steel, but also it can be extended in the future to estimate the influence on fracture toughness of different parameters, as hydrogen concentration or change in mechanical properties.