Abstract :
We review, unify and extend work pertaining
to evaluating mode mixity of interfacial
fracture utilizing the virtual crack closure technique
(VCCT). From the VCCT, components of
the strain energy release rate (SERR) are obtained
using the forces and displacements near the crack
tip corresponding to the opening and sliding contributions.
Unfortunately, these components depend
on the crack extension size, , used in the VCCT.
It follows that a mode mixity based upon these
components also will depend on the crack extension
size. However, the components of the strain
energy release rate can be used for determining
the complex stress intensity factors (SIFs) and the
associated mode mixity. In this study, we show that
several—seemingly different—suggested methods
presented in the literature used to obtain mode
mixity based on the stress intensity factors are indeed
identical.We also present an alternative, simpler
quadratic equation to this end. Moreover, a
-independent strain energy release based mode
mixity can be defined by introducing a “normalizing
length parameter.” We show that when the
reference length (used for the SIF-based mode
mixity) and the normalizing length (used for -
independent SERR-based mode mixity) are equal,the two mode mixities are only shifted by a phase
angle, depending on the bimaterial parameter ε
