On line monitoring of crack development in aircraft in active service is of great significance for flight safety. The fiber optic sensor has unique advantages over conventional sensors in this aspect. For modern aircraft, many critical structures are made of aluminum alloys. When structural damage occurs in structures due to cracking, it reduces the stiffness. This change is reflected in the structure through changes in dynamic characteristics such as natural frequencies and modal damping. In this paper, the ability of surface mounted fiber optic polarimetric sensors on aluminum vibrating cantilever specimen to detect cracks is studied. Different sources such as He-Ne laser, LD for fiber communication, laser pointer with longer, shorter and very short interference lengths are used to evaluate their ability for dynamic test. The preliminary experimental results show that the measured main frequencies will be different for various numbers of cracks and depths. The three sources, the drift of light intensity and the change of interference contrast will not affect the measured main frequency values. A theoretical analysis is also given. From these results, surface mounted fiber optic polarimetric sensors are expected to find application in monitoring structural integrity of structural members of aircraft in active service.
Detection of cracks in aluminum beams using fiber optic polarimetric sensor
Rissnachweis in Aluminiumstäben mit polarimetrischen optischen Fasersensoren
1999
5 Seiten, 3 Quellen
Conference paper
English
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