An Innovative Crack Tip Hole Drilling Technique for Fatigue Crack Growth Retardation in Metallic Structures

Among various crack repair methodologies, the Crack Tip Hole Drilling (CTHD) technique has emerged as a viable solution for mitigating crack propagation. The effectiveness of this technique is influenced by multiple parameters, with hole geometry being a critical factor. The implementation of a desirable hole geometry can significantly reduce stress levels around the drilled hole compared to the conventional approaches, thereby is expected to increase the number of cycles required for initiation and propagation of a new crack from the hole border and eventually enhance the total fatigue life of cracked structures. In this study, finite element simulation is used to investigate the influence of different hole geometries on the maximum stress distribution around the drilled holes in the CTHD method. The geometries examined include single circular holes, elliptical, two tangent circles, two overlapping circles, and three tangent circles. The primary objective of hole drilling is to reduce stress concentration in the vicinity of the hole within cracked structures. The numerical results showed that, among the geometries studied, the case with two overlapping circles could provide the maximum reduction in stress concentration. The numerical findings of this study were in agreement with the experimental data available in the literature.