Product Code: ICAL08_307

Acoustic Monitoring of Percussion Drilled Holes for Gas Turbine Engine Components
Authors:
Robert Wright, Connecticut Center for Advanced Technology; East Hartford CT USA
Christopher Pinciak, University of Massachusetts-Dartmouth; MA USA
Terri A. Marsico, Connecticut Center for Advanced Technology; East Hartford CT USA
Paul Denney, Connecticut Center for Advanced Technology; East Hartford CT USA
Amber Black, University of Connecticut; CT USA
Presented at ICALEO 2008

Percussion laser drilling is used to produce cooling holes in gas turbine engine components. Inconsistencies associated with pre-drilling operations make it difficult to consistently determine the proper number of pulses to completely drill a cooling hole and control its geometry and air flow characteristics (i.e., quality). Because film cooling effectiveness is critical to performance, present laser drilling procedures often call for a greater number of pulses to ensure the required hole geometry is met. The use of additional laser pulses can lead to internal damage that may reduce the life of the component. Also many non-value added operations are use to ensure the quality of the component. This paper will report on the development of an acoustic-based monitoring system which will indicate when breakthrough has occurred regardless of variations in material and/or coating thicknesses. This monitoring system has the goal of decreasing production costs by decreasing the need for non-value added procedures. The presentation will focus on the effects that materials, coatings, laser parameters, and incidence angles have on the acoustic signal produced during laser percussion hole drilling. The presentation is based on data collected from test coupons and from actual components. The data will not only compare acoustic emission spectrums from various drilling conditions but will also examine pulse-to-pulse and hole-to-hole variations as well.