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A FEASIBILITY STUDY FOR THE DEVELOPMENT OF A FATIGUE DAMAGE INDICATOR
Final rept. Jun 1965-Jun 1966
LOCKHEED-GEORGIA CO MARIETTA
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The report describes a feasibility study for the development of a fatigue damage indicator. Various fatigue sensing elements were evaluated and tested under simulated aerodynamic and environmental conditions. A fatigue sensor was optimized and integrated with an electronic system to function as an aid to fatigue damage assessment of an aircraft structure. After determining the behavior characteristics of the optimized sensor on laboratory coupons, practical applications were made on C-130E wing panels. The data indicated that a structures degree of exposure to repeated load occurrences could be monitored and the accumulated strain necessary to produce a fatigue failure could be forecast. The electronic phase was designed as the final element of an electro-structural inspection system for determining the fatigue status of an airframe. The electronic hardware consists of a module for an automatic quality control checkout of all detecting elements and module for indicating the sensors change in resistance. From the results obtained, it can be concluded that the system shows excellent promise as a method for determining the degree of exposure of an aircraft to repeated load occurrences. For long life transport aircraft, the system offers a much better means for determining the fatigue status of an airframe than simply stating the number of accumulated flight hours.
APPROVED FOR PUBLIC RELEASE