The Interaction Of An Edge Dislocation With An Inhomogeneity Of Arbitrary Shape In An Applied Stress Field And The Effects Of Overload On The Fatigue Crack Growth

The thesis contains two parts.In the first part, a general, approximate solution is presented for anedge dislocation interacting with an inhomogeneity of arbitrary shape undercombined dislocation and applied stress felds. The solution shows that thecontributions of the dislocation stress feld and the applied stress feld to theinteraction follow a simple superposition principle. The dislocation stressfeld has a short range effect, while the applied stress feld has a long rangeeffect. As special cases, explicit solutions for some common inhomogeneityshapes are obtained for the interaction induced by the applied stress feld.In the second part, on the basis of plastic zone toughening theory, aplasticity-corrected stress intensity factor range,K pc, is proposed todescribe the effects of overload on the fatigue crack growth. By use of thisnew crack driving force parameter a theoretical correlation of the Paris lawwith crack tip plastic zone is established. Thus, the plasticity-inducedoverload retardation can be actually predicted. Comparison with extensiveexperimental data showed that the plasticity-corrected reveals fairlywell the effects of the crack length and different loading variables, includingthe applied stress intensity factor range, load ratio, overload extent andoverload number, on the overload retardation.