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Most structural components contain inhomogeneities such as hardened surface layers or coatings,
welded or bonded elements, etc. The crack growth mode then depends not only on applied loading and
structure geometry but also on material inhomogeneity. In the presentation the analysis of crack growth mode
will be discussed for two cases: a bi-material structure with two materials of different thermo-elastic and plastic
properties connected along the interface and a structure with introduced interlayer of different material. The
simplified approach is presented, namely the MK-criterion [1,2] based on the linear elastic fracture mechanics
(LEFM). In the criterion it is assumed that crack growth follows the direction of minimum distortion energy
density at a distance corresponding to specified value of dilatation energy. For two materials, A and B the crack
growth from A to B or along the interface AB may occur depending on relative critical stress and fracture
energy values. For a three-phases structure, various modes of crack growth are possible.