Radial multi-layered isolator for helicopter interior noise reduction

Open Access
Autran, Pauline
Graduate Program:
Aerospace Engineering
Master of Science
Document Type:
Master Thesis
Date of Defense:
July 09, 2012
Committee Members:
  • George A Lesieutre, Thesis Advisor
  • helicopter noise reduction
  • gearbox isolation
  • radial multi-layered isolator
  • natural frequencies of rings
  • transmissibility
A three-layered isolator and a five-layered isolator were developed to reduce the propagation of vibrations in helicopter gearbox. Their dynamic behavior was investigated using both an augmented assumed-modes model and a finite element model. The natural frequencies and mode shapes were found to characterize each of the isolators, and the results were in good agreement between the models. Then the transmissibility of each isolator was studied in order to quantify the isolator’s effectiveness in terms of frequency stop band and vibration reduction performance. Models of notional isolators, one with three layers and one with five layers, were developed, each having a target stop band at the frequency range, [500 Hz; 2000 Hz] and very low transmissibility within the stop band (up to 0.0009 with the five-layered isolator). Other isolators that include geometric and material constraints were designed, and finally one three-layered isolator was designed and built for later experimentations.