A numerical investigation on the effect of an overload on fatigue crack opening and closure behaviour

The effect of a superimposed single tensile overload or a compressive overl oad in a block of constant-amplitude cycles on the crack opening and closin g stresses is investigated using an elastic-plastic finite element analysis . The results obtained are in basic agreement with the experimental observa tions. Following an applied tensile overload cycle, the crack opening and c losing stresses increase instantaneously, while the imposition of a compres sive overload cycle results in a small decrease of the crack opening and cl osing stresses. A detailed discussion of the residual stress and strain pat terns caused by the plastic deformation during the overload cycle and the c orresponding crack profiles is included. The main governing mechanism resul ting in the change of crack growth due to an overload is pointed out.