Accession Number : ADA257102


Title :   Real-Time Detection of Fatigue Cracks at Multiple Holes in 7075 Aluminum Using Acoustic Emission


Descriptive Note : Master's thesis


Corporate Author : NAVAL POSTGRADUATE SCHOOL MONTEREY CA


Personal Author(s) : Flatley, Thomas


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a257102.pdf


Report Date : Sep 1992


Pagination or Media Count : 76


Abstract : In the E-2C Hawkeye's wing center section, stress fractures have been identified in the main beam web section. The cracks occurred in several web section attachment holes. Previous work, concerned with fatigue data, used a finite element code to design a specimen which modeled the actual section of the beam at one particular fastener hole near wing station 49. Acoustic emission testing. was used to determine if crack initiation could be identified. In this work, acoustic emission techniques were applied to the monitoring of multiple cracks. The E-2C fatigue spectrum was used to load the specimens but fatigue testing was not an objective. Specimens were modified-by drilling holes and attaching angles that represented the structural shapes used to attach the section to the wing skin. The original one-hole configuration and the new multiple hole specimen configuration were tested. The cap angles were found to create a great deal of noise containing frequency components below 4OOkHz. Special high pass filters were fabricated which eliminated most of this noise. It was shown that linear location could be used to discriminate between crack growth signals and the filtered noise signals.


Descriptors :   *CRACKS , *ALUMINUM , *FATIGUE , *ACOUSTIC EMISSIONS , FREQUENCY , STATIONS , ANGLES , SHAPE , SIGNALS , ATTACHMENT , DRILLING , HIGH PASS FILTERS , WINGS , NOISE , FILTERS , WORK , ACOUSTICS , CONFIGURATIONS , HOLES(OPENINGS) , THESES , EMISSION , DETECTION , MONITORING


Subject Categories : Aircraft
      Acoustics
      Mechanics


Distribution Statement : APPROVED FOR PUBLIC RELEASE