Stress concentration at stop-drilled holes and additional holes

To retard crack growth, a stop hole is drilled at the crack tip. Reducing the stress concentration factor is the main reason for that. Also, it was investigated whether fatigue crack reinitiation and growth from a stop-drilled hole can more effectively be retarded by providing additional holes. In the present study, stresses at the periphery of holes were analyzed using software for two-dimensional elastic problems based on body-force method. The stress concentration factors for the stop-drilled holes and additional holes were investigated. The stress concentration tendencies can be used to estimate the site where a fatigue crack will initiate from a hole. The calculation results showed that the additional holes had positive or negative effects on lowering stress concentrations at the stop-drilled holes which depended on a combination of the arrangement and size of the two kinds of holes. The effectiveness of the arrangement of a stop-drilled hole and an additional hole on retarding crack growth can be evaluated by stress concentration analysis.