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2 Results We turn off two systems after the specimen was stretched to rupture. The two systems record the acoustic emission signal while specimen stretching process. The Amplitude(dB)-Time(s) diagrams is as follows in Fig. 5 and Fig. 6. Fig. 5 Amplitude-Time from 1000 meters away Fig. 6 Amplitude-Time on the spot From the above two pictures it can be concluded that the result by using the fiber optic acoustic emission sensor system is in agreement with the result by the traditional one. The Fiber optic acoustic emission sensor system can be seen after long distance transmission, and the monitoring result is very similar to the field detecting. The system extends the monitoring distance effectively, and has a strong anti-electromagnetic interference ability. It can carry out the long distance local damage monitoring.
DOI: 10.1177/1475921715624503
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3 Analysis We can clearly see the specimen damage process from the acoustic emission signal recorded in this experiment, as refer to Fig. 5 for details. There is no acoustic emission signal before 1 second, because specimen is in elastic phase. When specimen is in yield stage after 1second, a large number of acoustic emission signals emerge. The phenomenon that AE signal reaches a maximum value shows that specimen is in the upper yield point, and at this time damage is generated. Acoustic emission signal fell rapidly at 16 second, and appeared short stagnation phase. It suggests that this is one point of the time from the upper yield point to the lower yield point. Then the AE signal reaches a maximum value at 36 second again, and it shows the specimen is in strengthen stage. Acoustic emission signal is rarely and the energy is low in the time of 50 second to 70 second, which shows that the specimen is in necking stage. Acoustic emission signal increases instantaneously in 73 second, then there is no acoustic emission signal, and the specimen fractured at this moment. From the analysis we can conclude that the acoustic emission signal recorded by fiber optic acoustic emission sensor system made a fine match to the damage process of the specimen. The system can detect the acoustic emission reliably and can achieve the goal of long-distance local health monitoring effectively.
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Discussions and conclusions The fiber optic acoustic emission sensor system introduced in this paper greatly increased the transmission distance, and has a strong anti-electromagnetic interference ability. It can carry out the long distance local damage monitoring in complex environmental condition. NDT personnel will have a significantly improvement in work efficiency by this system because they can monitor in room. This system provides a technical means to carry out the long distance local damage monitoring. It has promising application foreground. Acknowledgment The work is financially supported by the Public Service Research project in Quality Inspection (NO.201010031) and the Science and Technology Research project of AQSIQ(No.2010QK410) References
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