PSI - Issue 44

Dora Foti et al. / Procedia Structural Integrity 44 (2023) 782–789 D. Foti et al. / Structural Integrity Procedia 00 (2022) 000 – 000

788

7

Figure 7. Identification by using SSI-UPC method for Test 1, four frequencies identified.

Table 4. Frequencies obtained from the experimental identification for the Tests 1, 2 and 3 and mean value. Frequency [Hz] Test 1 Test 2 Test 3 Mean Value 1 st 5.94 5.89 5.95 5.93 2 nd 6.04 6.02 6.05 6.04 3 rd 6.85 6.80 6.79 6.81 4 th 7.47 7.50 7.49 7.49

Furthermore, from the various tests, it was found that the mode shape corresponding to the 1 st frequency is flexural along x-axis, the mode shape corresponding to the 2 nd frequency is flexural along y-axis and the mode shape corresponding to the 3 rd frequency is torsional. The mode shapes related to Test 1 are shown in Fig. 8.

a)

b)

c)

Figure 8. – Mode shapes: a) 1 st frequency; b) 2 nd frequency c) 3 rd frequency.

3.3 Comparison between theoretical and experimental identification. The comparison between the first three experimental and theoretical frequencies, after the updating procedure, corresponding to the first flexional modes and to the first torsional one is reported in Table 5 where it is also indicated the percentage error between them.

Table 5. Comparison between experimental and theoretical frequencies and relative percentage error. Frequency [Hz] Test 1 Test 2 Test 3 Experimental mean value FEM value Percentage error

1 st

5.94 6.04 6.85

5.89 6.02 6.80

5.95 6.05 6.79

5.93 6.04 6.81

5.88 6.01 6.78

1.18% 0.66% 0.15%

2 nd 3 rd