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Optical Strain and Crack-Detection Measurements on a Rotating DiskThe development of techniques for the in-situ measurement and structural health monitoring of the rotating components in gas turbine engines is of major interest to NASA. As part of this on-going effort, several experiments have been undertaken to develop methods for detecting cracks and measuring strain on rotating turbine engine like disks. Previous methods investigated have included the use of blade tip clearance sensors to detect the presence of cracks by monitoring the change in measured blade tip clearance and analyzing the combined disk-rotor system's vibration response. More recently, an experiment utilizing a novel optical Moiré based concept has been conducted on a subscale turbine engine disk to demonstrate a potential strain measurement and crack detection technique. Moiré patterns result from the overlap of two repetitive patterns with slightly different spacing. When this technique is applied to a rotating disk, it has the potential to allow for the detection of very small changes in spacing and radial growth in a rotating disk due to a flaw such as a crack. This investigation was a continuation of previous efforts undertaken in 2011-2012 to validate this optical concept. The initial demonstration attempted on a subscale turbine engine disk was inconclusive due to the minimal radial growth experienced by the disk during operation. For the present experiment a new subscale Aluminum disk was fabricated and improvements were made to the experimental setup to better demonstrate the technique. A circular reference pattern was laser etched onto a subscale engine disk and the disk was operated at speeds up to 12 000 rpm as a means of optically monitoring the Moiré created by the shift in patterns created by the radial growth due the presence of the simulated crack. Testing was first accomplished on a clean defect free disk as a means of acquiring baseline reference data. A notch was then machined in to the disk to simulate a crack and testing was repeated for the purposes of demonstrating the concept. Displacement data was acquired using external blade tip clearance and shaft displacement sensors as a means of confirming the optical data and for validating other sensor based crack detection techniques.
Document ID
Document Type
Conference Paper
Woike, Mark
(NASA Glenn Research Center Cleveland, OH, United States)
Abdul-Aziz, Ali
(Cleveland State Univ. Cleveland, OH, United States)
Clem, Michelle
(NASA Glenn Research Center Cleveland, OH, United States)
Fralick, Gustave
(NASA Glenn Research Center Cleveland, OH, United States)
Date Acquired
May 23, 2014
Publication Date
March 10, 2013
Subject Category
Instrumentation And Photography
Aircraft Propulsion And Power
Report/Patent Number
Meeting Information
2013 SPIE Smart Structures and Materials and Nondestructive Evaluation and Health Monitoring Conference(San Diego, CA)
Funding Number(s)
WBS: WBS 284848.
Distribution Limits
Public Use Permitted.
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