Abstract:
Validation is carried out of the previously proposed implicit
criterion for choosing the direction of a fracture propagation
under the complex loading characterized
by the presence of all three modes of the stress intensity factors
$K_{\mathrm{I}}$, $K_{\mathrm{II}}$, and $K_{\mathrm{III}}$.
The criterion is based on the principle of local symmetry
according to which the fracture propagates in the direction
providing the zero values of the factors
of both mixed modes $K_{\mathrm{II}}$ and $K_{\mathrm{III}}$.
Since in the general case the two
conditions cannot be satisfied simultaneously,
the criterion is formulated as a minimization problem
for a functional that contains the sum of the values of the mixed modes
integrated along the entire front of the fracture.
The formulation of the criterion includes some parameter
that describes the effect of each of the mixed modes;
the value of this parameter should be chosen
by using the experimental data. Based on
two fracture propagation experiments with complex mixed loading,
validation of the criterion is carried out and
some estimates are given for the interval
of the best value of the weight parameter.
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