Limiting equilibrium and the development of angled cracks. Review of criteria

Abstract

Determining the conditions of limiting equilibrium of angled (oriented at an angle to the principal stresses) cracks, corresponding to their transition from the state of rest into a state of motion, is a natural generalization of the fundamental problem in fracture mechanics. The authors present criteria and the results of calculations based on them and compare them with experimental data. It is assumed that the body is uniform and isotropic, its behavior can be described by means of a linear elastic model, the crack does not close under a load, and inertial effects can be neglected when determining the stress-strain state. The experiments were carried out primarily under a combined load, containing mode I and II components, which were obtained in most cases by means of uniaxial extension of plates with an angled central crack, though different loading schemes are also encountered: torsion of thin-walled tubes, biaxial extension of plates, compression of disks, and compression of plates by cylindrical stamps. Primarily model materials, whose classical representative is PMMA, as well as silicate glass, polyurethane, 43-40 steel, DTD5050, 2024-T3, and 7075-TT7651 aluminum alloys, VK15 hard alloy (WC-Co), and graphite, were used.