Investigation into hydrogen induced fracture of cable bolts under deep stress corrosion coupling conditions

Abstract

The coupling effects of geostress and multi-attribute corrosion environments are the major causes of damage and rupture of prestressed cable bolts in deep underground environments. To determine impacts of different environmental factors on stress corrosion cracking of cable bolts in underground conditions, the accelerated stress corrosion tests and finite element numerical simulations were carried out. By implementing the material diffusion theory and appreciating the hydrogen induced lattice expansion effects, the diffusion and aggregation behavior of hydrogen in cable bolts were simulated. The influences of stress intensity and hydrogen concentration on failure mechanisms of cable bolts were studied by considering the hydrogen induced expansion strain. The failure only occurred in the environments where sufficient hydrogen concentration existed. The hydrogen diffusion flux and distribution were consistent with stress concentration distribution. The prestress accelerated the hydrogen diffusion to stress concentrated position leading to a greater strain in the stressed areas, which consequently induced hydrogen expansion stress and decreased cohesion strength of lattice near crack tip. The fractographic features of failed specimen were analysed and hydrogen assisted fracture was confirmed to be one of the main failure mechanisms leading to stress corrosion failures. The methodologies proposed could be used to study the diffusion and distribution of hydrogen in metals and the obtained results improved the understanding failure mechanism of hydrogen assisted SCC.