Digital Repository, CONVEGNO IGF XXII ROMA 2013

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A numerical model to evaluate the effect of hydrogen embrittlement on low-alloy steels
L. Vergani, G. Gobbi, C. Colombo

Last modified: 2013-06-27


Some extreme working environments are characterised by corrosive conditions, able to develop
hydrogen formation. The presence of atomic hydrogen localized in correspondence of plastic strains at the
crack tip modifies the steel behaviour and its macroscopical mechanical properties. The phenomenon of
hydrogen embrittlement is, indeed, one of the main responsible for the increase in fatigue crack growth rate and
life reduction. For this reason, it is important to have validated numerical models able to estimate the
mechanical behaviour of material in presence of hydrogen. Aim of this study is to develop a numerical model of
two low-alloyed steels used in pipelines applications. Numerical simulations of C(T) specimens are carried out in
different steps, considering hydrogen presence/absence combined with local plastic strains of the material.
These two parameters are, indeed, responsible for a drop in material toughness, therefore for an increased crack
growth rate. Two modelling techniques are used to simulate crack propagation: application of cohesive elements
characterised by laws of degradation of mechanical properties, and the virtual crack closure technique (VCCT).
Once model is validated by a comparison with experimental toughness measures, final considerations on the
most valid simulation technique for the considered case are proposed.

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