This paper studies the problem of a mode III crack in an elastic layer on
a substrate under the framework of strain gradient elasticity theory. The
effects of volumetric and surface strain gradient parameters on the crack tip
asymptotic stress and crack shape are investigated. Due to strain gradient
effect, the crack opening, the magnitude of the stress ahead of the crack
tip, and the stress intensity factor are significantly higher than those in
classical linear elastic fracture mechanics. More significantly, the direction of
the stress ahead of the crack tip with strain gradient is opposite to that
in the classical linear elastic fracture mechanics. The conventional linear
elastic fracture mechanics results are recovered when the gradient parameter
reduces to zero. The influence of the substrate on the fracture mechanics
parameters is very significant when the strain gradient effect of the materials is
considered.
Keywords
Strain gradient elasticity, film-substrate structure, mode
III crack, crack tip field, fracture mechanics.
