The role of plastic strain gradients in the crack growth resistance of metals


Type
Article
Change log
Abstract

Crack advance from short or long pre-cracks is predicted by the progressive failure of a cohesive zone in a strain gradient, elasto-plastic solid. The presence of strain gradients leads to the existence of an elastic zone at the tip of a stationary crack, for both the long crack and the short crack cases. This is in sharp contrast with previous asymptotic analyses of gradient solids, where elastic strains were neglected. The presence of an elastic singularity at the crack tip generates stresses which are sufficiently high to activate quasi-cleavage. For the long crack case, crack growth resistance curves are predicted for a wide range of ratios of cohesive zone strength to yield strength. Remarkably, this feature of an elastic singularity is preserved for short cracks, leading to a severe reduction in tensile ductility. In qualitative terms, these predictions resemble those of discrete dislocation calculations, including the concept of a dislocation-free zone at the crack tip.

Description
Keywords
Strain gradient plasticity, Length scales, Cohesive zone modelling, Finite element analysis, Fracture
Journal Title
Journal of the Mechanics and Physics of Solids
Conference Name
Journal ISSN
0022-5096
1873-4782
Volume Title
126
Publisher
Elsevier BV
Sponsorship
European Commission Horizon 2020 (H2020) ERC (206409)