Laser Peening of Dovetail Features on Blades and Disks

In aircraft gas turbine engines, in most cases, the blades areheld in rotating disks by a dovetail attachment that fits into amatching slot in the rim of the disk. The contact area betweenthe blade dovetail and the dovetail slot is subject to vibrationand high stresses, leading to fretting conditions. Eventually,fretting fatigue cracks initiate in the fretting area andpropagate into the disk and/or dovetail slot, and as a consquence,the blades and disks are retired for cause. This is a significantproblem. The application of a soft metallic coating to the bladedovetails helps to decrease this problem, but recoating and theeventual retirement of blades and disks for fretting damageremains a significant cost. This program will evaluate thefeasibility of using laser peening to increase the resistanceblade dovetails and dovetail slots to fretting fatigue damage andfailure. Two issues will be addressed. One, the magnitude of thebeneficial effect of laser peening to increase the frettingfatigue life associated with dovetail fretting will be evaluated. Two, methods for laser peening the inside fretting surface ofdovetail slots will be evaluated. The evaluation will considerlower cost, ease of use, reliability, and maintainability ofhardware.