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.