The stress-strain state analysis near the crack tip in a power-law material under
mixed-mode loading conditions is investigated. By the use of the eigenfunction
expansion method the stress-strain state near the mixed-mode crack tip under plane
stress conditions is found. The type of the mixed-mode loading is specified by the
mixity parameter, which varies from 0 to 1. The value of the mixity parameter
corresponding to a mode II crack loading is equal to 0, whereas the value
corresponding to a mode I crack loading is equal to 1. It is shown that the
eigenfunction expansion method results in a nonlinear eigenvalue problem. The
numerical solutions of the nonlinear eigenvalue problems for all values of the mixity
parameter and for all practically important values of the strain hardening (or creep)
exponent are obtained. It is found that mixed-mode loading of the cracked plate gives
rise to a change in the stress singularity in the vicinity of the crack tip.
Mixed-mode loading of the cracked plate results in new asymptotics of the
stress field, which is different from the classical Hutchinson–Rice–Rosengren
(HRR) stress field. The approximate solution of the nonlinear eigenvalue
problem is obtained by a perturbation theory technique (artificial small
parameter method). In the framework of the perturbation theory approach, a
small parameter representing the difference between the eigenvalue of the
nonlinear problem and the undisturbed linear problem is introduced. The
asymptotic analysis carried out shows clearly that the stress singularity in the
vicinity of the crack tip changes under mixed-mode loading in the case of
plane stress conditions. The angular distributions of the stress and strain
components (eigenfunctions) in the full range of values of the mixity parameter are
given.
Keywords
stress-strain state near the crack tip, mixed-mode loading,
mixity parameter, nonlinear eigenvalue problem,
perturbation technique