Crack growth under fatigue load spectrum: numerical simulation by coupled FEM-DBEM approach

Numerical predictions of fatigue crack growth under general load spectrum are obtained by coupled FEM-DBEM approach. An initial part-through corner crack, in a pre-notched specimen undergoing a traction fatigue load, propagates becoming through the thickness. A two parameter crack growth law (“Unified Approach”) is calibrated by in house made constant amplitude experimental tests. The crack growth retardation after an overload is reproduced, calculating the residual stresses responsible for such retardation by a sequence of elastic-plastic static FEM analysis; such stresses are then applied to the crack faces for the propagation in a DBEM environment. A satisfactory agreement between numerical and experimental crack growth rates are displayed, for both part-through cracks and through the thickness cracks. This approach provide general modeling capabilities, with allowance for general crack front shape and fully automatic propagation.