In this ICAM webinar, Professor Norman Fleck FRS from the University of Cambridge, discussed the mechanics of hydrogen diffusion and embrittlement.
Hydrogen embrittlement results from the diffusion of hydrogen into a metallic alloy, such as pipeline steels, and subsequent embrittlement at various trapping sites, such as grain boundaries. These traps are sites of hydrogen embrittlement, and the degree to which the traps soak up hydrogen depends upon the type of site and the enthalpy of trapping.
A large number of material parameters dictate the diffusion process. A non-dimensional analysis has been performed in order to identify the small number of governing non-dimensional groups and to analyse the two standard tests: hydrogen uptake in the electro-permeation test and hydrogen release in the thermal desorption test. Fracture mechanics for hydrogen embrittlement from short cracks has also been developed but many questions still remain.
Norman Fleck is Professor of the Mechanics of Materials in the University of Cambridge’s Engineering Department. He received his Ph.D. from Cambridge in 1984 on the subject of metal fatigue, and then spent a post-doctoral year at Harvard University as Lindemann Trust Fellow, working with Professor John W. Hutchinson on creep fracture.
He returned to Cambridge as a lecturer in 1986, and was subsequently promoted to a Readership and then to a Professorship. He is the Founder-Director of the Cambridge Centre for Micromechanics, and was Head of the Mechanics, Materials and Design Division for 11 years, until 2009.
He is an ISI highly cited author with over 280 journal publications, and is a Fellow of the Royal Society, Royal Academy of Engineering, Academia Europaea and of the European Academy of Science. He is on the editorial boards of several engineering journals, and has close collaborations with many US and European groups, having held visiting positions at Harvard University and at NASA Langley. He combines experiments and theory to develop mesoscale and macroscale constitutive models of engineering materials.