14. starptautiskÄ konference 2012 - Latvijas JÅ«ras akadÄmija

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Proceedings of 14th International conference „Maritime Transport and Infrastructure - <strong>2012</strong>”Fig. 1. The view of a blade covering fragment from outside blade "bottom": a zone of the adhesivedestruction of a glutinous connection (it is designated by a dotted line). Shooters show zones of a film of glueVK-3, sharply differing among them on colour:1 – site of glue of dark brown colour, 2 – site of glue of light brown colourOne of IAC recommendations was the following: ” The Designer and the Manufacturer ofblades must develop modern, more effective quality monitoring of a condition of blades, including thedurability control of stuck coupling together blades surfaces, with application of the devices allowingprecisely to define presence starved spots and the beginning of glutinous connections destruction.”As shows the analysis of the collapsed blades with similar defects in 2009 year, themanufacturing technology of these blades haven't been broken by the Manufacturer in Plant. Thereforean origin of such defects to define is rather problematic. Incoming inspection of these blades haverealized to the full extent, provided by Technical Requirements. So, for the reasons specified above, itis impossible to define the given defect, which is connected with a chemical compound of a glutinouslayer, in the manufacturing conditions of the blade.Additionally it is necessary to note, that ultrasonic methods is not effective for operativecontrol to detect the defects of starved spot type in composite materials designs as its demand fullscanning the area of design elements and possess enough low sensitivity.Take into account that the wide application of composite materials in the transport design allthe time call for the simple, technological and cheap control methods to detect such defects as starvedspot and stratification. So a method of the acoustic emission during thermo loading has been offered asthe non-destructive monitoring of composite materials designs.Test ProcedureThe specimens of the composite material design elements with defects and without ones havebeen chosen for testing under thermo loading.The specimens have been cut out off the faultless covering of elevator (heat thermo loading).In one specimen artificial defects have been created, but at the same another one would remainfaultless (Fig. 2). Also a full scale aileron with defect was loading by high temperature to detect thisfault in the construction. The same full-size aileron made of composite material was chosen for coldtreatment loading.46
Proceedings of 14th International conference „Maritime Transport and Infrastructure - <strong>2012</strong>”a. b.Fig. 2 The scheme of an arrangement of Acoustic Emission Sensors (1),defects (2) and zones of heating (3) on composite samples:a - with defects; b - free of defects.Two ways of specimens’ thermo loading were chosen to investigate the possibility of defectmonitoring: the surface of samples was exposed to heating by a blowtorch (without contact of an openflame with a material) to temperature +70°C and the subsequent natural cooling to room temperature(+18°C of a premise in which experiment was made.The elevator was taken out from a premise on open space at air temperature - 7°C with wherewas maintained in a current of 60 mines and further was brought back in a premise with temperature+18°C. The temperature on a surface of samples was supervised by the contactless remotethermometer “Raynger MX”.EquipmentTwo-channel portable “Pocket AE” device, soft program – “AE Win package”, piezoelectric detector, Pyrometer Raynger MX, Portable blowtorch.The following settings were used: threshold - 30 dB, High frequency filter - 5 kHz (for an elevator) and 100kHz, Low frequency filter - 1000 kHz, Internal Preamplifiers –26 dB, Frequency of sample – 2 MSPS.Test ResultsTest 1 Preliminary, to determinate the possibilities of the new approach, and to state the needsettings, the two specimens (with known detects, and free of one’s) were exposed to heating till +70°Cby blowtorch and after that natural cooling to room (+18°C) temperature. All the time (heating andcooling) the acoustic emission impulses from the piezoelectric gauges were summarize to „PocketAE” device.The results are following (Fig.3):47
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14. starptautiskÄ konference 2012 - Latvijas JÅ«ras akadÄmija

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