Abstract: An apparatus for inducing high frequency out-of-phase, vibrations in adjacent span-wise panel portions of a plate type structure, such as an airfoil blade of a gas turbine engine. The apparatus includes a novel bifurcated duct for conducting and directing two out-of-phase streams of gaseous flow, and a uniquely structured air chopper which generates the two out-of-phase gaseous streams. The duct has an upstream end with which the output of the air chopper is in communication, and a stepped-down downstream end at which the airfoil blade (or other plate type structure specimen that is to be tested) is held, supported, and positioned in a chord-wise direction, such that the two out-of-phase gaseous streams impinge upon, and induce the same high frequency vibration in, two preselected, adjacent, span-wise panel portions of the specimen, thereby the panel portions vibrate out-of-phase.

Abstract: Undesirable vibrations of stator airfoil vanes circumferentially disposed in annular rows, and fixed at their ends by a sectored outer shroud and a sectored inner shroud, in an axial flow compressor of gas turbine engine are damped by a damper assembly that is fitted into, and is frictionally engaged, in the sectored inner shroud which, in turn, is segmented to assist in this damping. The damper assembly includes: A metal seal strip member having indentations; a metal sine wave-shaped damper and spring member that is complementary to, and is engaged with, the seal strip member; and, a honeycomb member affixed to the bottom surface of the seal strip member. The vibrations cause movement of the shroud segments which, in turn, cause rubbing contact; and, the resulting friction heat energy is conducted through the metal components of the damper assembly to the thermal sink that is the through-flowing air in the compressor.