14. starptautiskÄ konference 2012 - Latvijas JÅ«ras akadÄmija

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Proceedings of 14th International conference „Maritime Transport and Infrastructure - <strong>2012</strong>”N ae3503002502001501005000a20 40 60 80 Time, secbFig. 3. The summarize (Nae) of acoustic impulses AE vs. Time at heating and cooling:a - specimens with defects, b – specimen free of defectsWe can see, that during the heating the specimen with defects (left side of Fig.3, a) theimpulses of acoustic emission begin to intense summarise till finishing of thermo loading (+70°C).And after the heat treatment (the right side of Fig.3) we also see some growth of summarising of AEimpulses, but with the less intensity. In opposite, the free of defects specimen (Fig.3, b) practically donot reproduce the AE impulses during the whole time of experiment of heat loading.Most likely during heating of the defective zone, not making single integral formation yet,occurs further stratification of composite components, as causes the accelerated generating of AEimpulses, not fading at natural cooling. In the second case (a faultless specimen), the design elementpractically behaves as a single formation, which is not reacting to thermal impact.Test 2 As other object of research has been chosen full scale aileron, which also was exposedto heating to +70ºC. However, due to big size of the new research object versus previouslyinvestigated two specimens heating zones were chosen near the defective zone in one case - this zonewas determinate as defective by an impedance method (natural peeling was revealed). In another case,as other place of heating also to +70º has been chosen the faultless zone. Also an impedance methoddetects this free of defect zone (Fig.4).Fig. 4. The arrangement scheme on full-scale aileron:1- The Acoustic Emission piezoelectric gauge,2 - heating zones near the defect zone, 3 faultless zone.The plan of experiment was the same as for the previous Test 1: heating impact till +70 ºC inthe zone 2 and 3 (Fig.4) and natural cooling in premise till +18 ºC. The summarising of acousticemission impulses has the same mode as in the previous case with two specimens in Test 1. More thanthat, as the settings of the equipment of the experiment do not changing, we see a little less total sumof the acoustic emission impulses (Fig.5).48
Proceedings of 14th International conference „Maritime Transport and Infrastructure - <strong>2012</strong>”N ae2001501005000 20 40 60 80 Time, secabFig. 5. The summarize (Nae) of acoustic impulses AE vs. Time at heating and cooling:2 - near the defect zone, 3 - In free of defect zone.Thus we see that the general character of the accumulation of AE impulses hasn't changed,whereas total value of the AE impulses sum from the gauge near to a defective zone has decreasedalmost twice. This can be caused or the smaller size of defect or greater remoteness of a place of thedefect from AE- gauge, or the bigger sizes of the object of research. Anyway, both at research ofsamples, and at research of natural object we see significant growth of signals of acoustic impulses atan arrangement of AE gauge near to defective zones at thermal loading of the objects of research.Test 3 The following object of АE-heat monitoring was the full-size elevator. The use of theimpedance method wasn't revealed any peelings though there were «traces of hits of lightning» (fig.6).Fig. 6. The scheme of AE- gauges arrangement and the dispositions of defect places, caused byimitation of defeat by a lightning on an elevator covering:1.-the piezoelectric acoustic emission gauges, 2. – the zones of defeat by lightningThis time another approach was applied. The composite-made elevator has been cooled totemperature - (minus) 7 ºC during 60 minutes on the open air and then has been quickly brought in alodge (+22ºC) where it has undergone to difference of the temperatures due natural heating. All thetime in the premise the AE-monitoring was running to summarize the impulses of acoustic emission.The following results have been received (Fig.7). It appears that in this case the effect of thermalloading is expressed less brightly, than at our Tests 1-3. However it is necessary to consider that theimpedance method didn't find any composites defects as starved spot, stratification or peeling types onthe elevator. Also the low temperature influence might be insufficiently.49
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