Effect of optimized repaired structure with a hole on crack turning and fatigue life

A method for artificially promoting crack turning is introduced. By placing a crack-absorbing hole near the patch, the dual purpose of improving the crack deflection angle and prolonging the remaining lifespan of the repaired structure was achieved. Important components behind the patch were protected as well. The influence of the location and size of a single hole on the stress concentration and crack propagation path of an optimized repaired structure was studied using the finite element method. Simultaneously, the stress influence coefficient was introduced to characterize the "attraction" effect of stress at the edge of the opening on the crack propagation path. The results showed that the optimized patch size and the existence of holes led to the deflection of cracks toward the holes and a larger residual fatigue life. When the relative hole radius was 2.22%, the relative hole axial distance was 4% and the relative hole horizontal distance was 15.56% (with a relative patch width, length, and thickness of 35.7%, 50%, and 83.3%, respectively). The deflection angle increased and the residual fatigue life improved.