Drilling Repair Index (DRI) based on two-parameter fracture mechanics for crack arrest holes

•Three configurations of crack arrest hole (CAH) are studied.•The stress concentration factor, the notch stress intensity factor and the constraint trough effective T stress have been determined.•Reduction of stress concentration is maximum when a second hole is drilled near the crack tip at an optimal angle is also efficient•Using Two parameters Fracture Mechanics, Drilling Repair Index (DRI) is defined.

The most common method of preventing cracks from growing is by making a “drill stop” or crack arrest hole (CAH) at the crack tip. The objective of drilling a hole is to “blunt” the crack tip and reduce the stress concentration at the crack tip. In this paper the following situations are studied: (i) a single hole drilled at a blunt crack tip, (ii) a single hole drilled at a distance r from the crack tip with an orientation angle θ relative to the crack direction and (iii) a second hole called the “stress concentrator reducer hole” drilled symmetrically to the first near to the crack hole. A Drilling Repair Index (DRI) is proposed for evaluation of the efficiency of the CAH method. It is based on two-parameter fracture mechanics.