PSI - Issue 8

A. De Luca et al. / Procedia Structural Integrity 8 (2018) 288–296 A. De Luca / Structural Integrity Procedia 00 (2017) 000 – 000

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For the specific test case, the RMSD damage index has been calculated in correspondence of the three receiving sensors for the 5 investigated damages configurations. As aforementioned, Lamb wave propagation has been simulated in plates characterized by 5 damages configurations modeled by means of 5 previous impact simulations (5 J, 10 J, 15 J, 20 J and 25 J impact energy levels), respectively. Fig. 4 shows the RMSD damage index values for the investigated test cases.

Fig. 4. RMSD damage index vs. impact energy level.

According to Fig. 4, it can be noticed that the damage index value remains lower between 5 J and 10 J and sharply increases between 5 J and 15 J, because of the different refraction and reflection mechanisms between Lamb waves front and damages. The increase phase is due to the difference in terms of damage size. Between 10 J and 15 J impact energy levels such difference is larger than the other differences between two consecutive values. Fig. 5, 6 and 7 shows the comparison between the baseline and the signal received by the sensors 2, 3 and 4 in the damaged plates, respectively. In particular, the figures denoted with the letter “a” are referred to the 5 J damages configuration, whilst the figures with the letter “b” to the 15 J d amages configuration. The authors provided only these results because they are the most significant to highlight the different refraction and reflection phenomena between the 5 J damage configuration, where the RMSD damage index remains lower, and 15 J damage configuration, characterized by higher damage index values.

Fig. 5 Sensor 2 receiving signal compared with the baseline signal: (a) 5J damage configuration; (b) 15 J damage configuration.