Theoretical, experimental and numerical investigations on crack growth in fracture mechanical graded structures

Crack propagation is not only influenced by the loading situation but also by a material gradation within the structure. Therefore, it has to be examined how the crack propagation behavior changes when a crack grows through regions which are characterized by different fracture mechanical material properties. Within the scope of this paper, especially the influence of a fracture mechanical material gradation on the beginning of stable crack propagation, the crack velocity, the crack propagation direction as well as on the occurrence of unstable crack growth for statically and cyclically loaded components is discussed. In this context, a developed concept for the prediction of crack propagation in fracture mechanical graded structures, experimental investigations as well as numerical simulations of crack growth are presented. The experimental considerations clarify the influence of the material gradation and confirm the predictions of the new concept. The numerical simulations of crack growth indicate the influence of the material gradation especially on the lifetime of graded components.