Precision Small-Hole Drilling for Gas Turbine Engine Components

This project addresses experimental and theoretical studies on the use of abrasive-waterjets (AWJs) to drill precise small-diameter holes in advanced materials. AWJs have been demonstrated for the precision drilling of small-diameter holes (0.5-2.5 mm [0.02-1.0 inch]) in metals, glass, composites, and coated materials. Our understanding of the mechanics of the drilling process is very limited, yet it is critical for future product implementation. Prediction and control of hole size and shape (straight, convergent, and divergent) requires a better understanding of the drilling process; the proposed effort aims at developing this knowledge. The approach followed includes parametric drilling test to study the effect of jet structure parameters on hole drilling results such as drilling time and hole shape. Studies using high- speed movies will be conducted to understand the kinematics of the penetration process. Dynamic manipulation of the jet structure-by real-time control of pressure and abrasive flow rate-will be studied. This method has been found essential for controlling both quantitative and qualitative hole drilling results in coated and fragile materials. A physical model will be formulated to include critical drilling process parameters. Phase II research efforts will include advanced modeling studies, optimization of the process, and drilling system control requirements. An AWJ-based drilling system will be produced and marketed in Phase III.