A model for predicting the overload effects on fatigue crack growth behavior

An analytical model using crack driving force parameter, amp;Delta;K* was developed to account for the overload interaction effects on fatigue crack growth behavior. Crack growth acceleration and retardation were modeled using residual stress intensity concept. Fatigue crack growth behavior was predicted using this model for SE(T) specimen made from an aircraft grade D16 (2024-T3 equivalent) aluminum alloy, subjected to (a) constant amplitude load, (b) constant amplitude load, interspersed with single tensile overloads at certain intervals of crack length. Fatigue crack growth tests were performed under the above load sequences and the experimental crack growth results were compared with those obtained from the proposed model. All the fatigue tests were performed in a servo-hydraulic test machine and the crack length was measured by traveling microscope/cellulose acetate replication method. A fairly good correlation was obtained between the experimental and predicted crack growth curves under the applied loading sequence.13