An interaction integral technique for multiple cracks systems is implemented as a post processor into the commercial FE code ABAQUS. In combination with automatic geometry reconstruction and intelligent remeshing procedures, this tool represents the foundation of the crack path simulation. Crack growth is simulated by incremental extensions of the crack faces based on crack growth and deflection criteria. The interaction-integral enables the accurate calculation of stress intensity factors considering multiple cracks and strongly curved crack faces. A numerical specimen exhibiting a three cracks system with a hole is investigated. The specimen's material is chosen to be an aluminum alloy Al-7075 with Young’s modulus E=72000 MPa, Poisson’s ratio nu=0.33, the exponent of Paris’ crack propagation law p=1.34 and the critical fracture toughness KIc=23.9 MPa(m)^(0.5). The numerical crack extension parameter is da=0.25 mm. The external loading u0 is selected to be a constant displacement u0=u2=-0.158 mm.