The Role of Surface Forces in Subcritical Crack Growth and Healing
Sponsor: Lawrence Berkeley National Laboratory, DOE-BES-Geoscience
Duration: 10/1/2020- 5/31/2023
Role: Sole PI
This is a collaborative research between CUBoulder and the Geoscience team at the Lawrence Berkeley National Laboratory, aiming to promote fundamental understanding of subcritical crack growth and healing in calcite.
Subcritical crack growth (SCG) is relevant to many geological processes at different length and time scales, e.g., time- and rate- dependent deformation of brittle rocks, relaxation of internal stresses in rock systems and delayed earth ruptures. The intricate coupling between physiochemical processes (i.e., adsorption and diffusion) and mechanics (i.e., stress concentration and crack opening) at the vicinity of the crack tip, however, has never been fully resolved. Significant pressure can develop when two solid surfaces are brought close to each other (which is the case at the crack tips), causing the solid-fluid interaction zones of the two surfaces overlap. This pressure, often referred to as the disjoining pressure, can be attractive and repulsive depending on the wall separation and the fluid chemistry. Its effect on the apparent fracture toughness (KI0) has been largely ignored in fracture mechanics and SCG literatures.
This study will test the hypotheses that the KI necessary to propagate cracks in aqueous environment (KI0) is reduced from the intrinsic value (KIC) because of the repulsive disjoining pressure developed between the fracture surfaces. Specifically, we plan to develop a surface-based fracture theory (SFFT) for modeling SCG, where the surface force and its variation with respect to environment serves as the central building block. The other key ingredients are the species transport equation in a varying aperture slit, and fracture mechanics solutions of crack opening profile and stress intensity factor. The ultimate goal of this project is to offer bottom-up predictions of environment-enhanced SCG in glasses and calcite.
Schematic of surface-force based fracture theory in modeling SCG.
Benjamin Gilbert, Ph.D., LBNL
Seiji Nagakawa, Ph.D., LBNL
Hang Deng, Ph.D., Peking University
Steven Pride, Ph.D., University of California, Berkeley
Nakagawa*, S, Zhang, Y., Eskandari-Ghadi†, M., Vasco, D.W. (2023) Corrections of Double-Torsion (DT) subcritical crack growth tests for crack profile geometry. Theoretical and Applied Fracture Mechanics 124, 103752, DOI: 10.1016/j.tafmec.2023.103752.
Eskandari-Ghadi, M.†, Nakagawa, S., Hang, D., Pride, S., Gilbert, B., Zhang, Y.* (2022) The role of surface forces in environment-enhanced cracking of brittle solids. Journal of Mechanics and Physics of Solids 172, p.105162, DOI: 10.1016/j.jmps.2022.105162