PSI - Issue 5

K.S.C. Kuang et al. / Procedia Structural Integrity 5 (2017) 1168–1175 Dong Yang et al. / StructuralIntegrity Procedia 00 (2017) 000 – 000

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(b)

Fig. 4. The results of IPOFs sensor (a) The trend of crack propagation; (b) High frequency band.

3.3. Comparison and discussion

To validate the response and accuracy of proposed method for crack initiation and propagation in steel specimen, another approach was introduced in this experiment, namely the detection of acoustic emission using a pair of AE sensors. For the AE sensors, the results obtained during the fatigue test is shown in Figure 5. The AE hits with relatively high amplitude first appeared at about 3900 s , which indicate the occurrence of crack. This reading compares well to the result obtained using the POFs sensors shown in Figure 4 (b). The density of AE hits begins to increase dramatically after 7800 s , indicative of the rapid propagation of crack. This result shows consistency with that of the processed POFs sensor data (Figure 4(b)) where the amplitude of high frequency band was found to increase rapidly after approximately 8000 s .

Fig. 5. The results from AE sensor

The comparison of results between AE sensor and the POFs sensor shows that the proposed POFs sensor in conjunction with the algorithm used in this study is able to monitor both fatigue crack initiation and its propagation in real-time with a good degree of sensitivity and accuracy.