Compliance of star-like cracks: non-equivalence to holes, and the effect of random shape irregularities

On the example of star-like cracks, we address the following issues: (1) elastically isotropic inhomogeneities may not be equivalent to the circular ones (2-D circular holes), and the difference between their compliances may be large; (2) the hypothesis that the combined effect of different shape irregularity factors can approximately be represented as a product of the effects caused by each of them separately.