Holographic mode shape investigation of aircraft engine impellers

The resonant mode shapes of several radial-bladed stationary impellers and of two radial blades removed from the impeller body were investigated by CW-laser holographic interferometry. The greatest attention was paid to the frequency range from 10 to 15 kHz. A retroreflective white paint was used for coating the impeller surface, which helped to enhance the fringes in real-time/time-average visualization, and to shorten the exposure times in hologram recording. Impeller excitation was performed by a set of 10 piezoelectric transducers. In cases with higher-amplitude vibrations a method of additional static exposure was applied.