Date of Award

3-2000

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Aeronautics and Astronautics

First Advisor

Gregory S. Agnes, PhD

Abstract

Aircraft engine blades are subject to harmonic forcing produced from periodic wakes created by fixed stators. Prolong or repeated exposure at blade resonant frequencies can cause vibration-induced fatigue, otherwise known as High Cycle Fatigue (HCF). Structural mistuning coupled with HCF causes premature blade failures, excessive operational costs and increased engine servicing. This study offered a novel approach to characterize mistuning effects on bladed disk forced vibration behavior. A model fan reduced in dynamic scale from an operational jet engine fan and with weak inter-blade coupling was fabricated. Aerodynamic disturbances produced by the stators were replicated by magnets attached to a rotating flywheel interacting with similar magnets epoxied to the model fan blades. Magnet configurations mimicked engine order. Accelerometers transducers at blade tips measured forced vibration loads. Transducer response signals were analyzed by a data acquisition system. The flywheel excitation system performed very well in its ability to impart periodic forcing onto the bladed disk. The harmonic forcing input was characterized and capable of producing a wide assortment of forced vibration results. Mistuning and engine order primarily effected system response, specifically in the areas of localization levels, individual blade response profiles, number of maximum blade amplitude peaks and localization frequency range.

AFIT Designator

AFIT-GAE-ENY-00M-05

DTIC Accession Number

ADA380221

Comments

The author's Vita page was omitted.

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