Emilio Martínez Pañeda
University of Cambridge. Department of Engineering
Presented by: MSE Graduate Student Board, Sponsored by the ElectroChemical Society
Mechanism-Based Modelling of Hydrogen Embrittlement
The use of high-performance materials in energy infrastructure is firmly challenged by the detrimental effect of hydrogen - the ductility and toughness of structural alloys are dramatically reduced in aggressive environments. With current engineering approaches being mainly empirical and highly conservative, there is a strong need to understand the mechanisms of such hydrogen-induced degradation and to develop models able to predict the initiation and subsequent propagation of cracks as a function of material, environmental and loading variables. However, hydrogen assisted cracking is a very complex mechanical-chemical problem that depends sensitively on mechanisms that pertain to the micro and atomic scales. The speaker and his collaborators have been actively engaged in the development of enriched continuum-like models that aim to incorporate the mechanisms governing hydrogen-assisted cracking. To this end, efforts have been devoted to investigate crack tip fields by means of strain gradient plasticity (SGP) models, as classical continuum theories are unable to adequately characterize behaviour at the small scales involved in crack tip deformation [1,2]. Gradient-enhanced predictions proved to be particularly relevant in hydrogen embrittlement models due to the essential role that the hydrostatic stress has on both interface decohesion and hydrogen diffusion. Encouraging agreement with experimental data has been obtained by incorporating the influence of geometrically necessary dislocations (GNDs) in the modelling of hydrogen transport  and environmentally assisted cracking . The promising results achieved have attracted the interest of industrial partners and technical standards organizations, ending with a scientific/engineering handshake a journey that began from fundamental micromechanics.