Numerical models for simulating hydrogen diffusion and embrittlement in high strength steels

Abstract

This thesis presents and discusses hydrogen diffusion modelling as a first step in predicting and mitigating hydrogen-assisted fracture. Hydrogen embrittlement is a common phenomenon that degrades metals and alloys, and related failures are usual in industry. However, the relationship between hydrogen and the transition from ductile to brittle modes of fracture is not entirely clear. Therefore, the present work has the objective of establishing, validating, implementing and analysing a consistent numerical model for hydrogen diffusion, in a Continuum Mechanics framework by means of a Finite Element software. In addition, a notched tensile test is simulated, demonstrating that the combination of diffusion with damage models might predict brittle fracture. Vessels storing hydrogen are also simulated with the purpose of finding hydrogen distributions near stress concentrators; influence of cyclic loads and compressive residual stresses are also evaluated in these deposits.