PSI - Issue 48

G. Gusev et al. / Procedia Structural Integrity 48 (2023) 176–182 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 4 (a) Position of the 11 vibration acceleration control points on the structure and (b) total accelerations in the model in the final phase of the actuator impact m/sec (shape of the model deformation in scale 700000:1).

They are located on the columns of the model structure in two levels - pts. A1, A2, A3, A4 are the columns of the third level. Points A8 - A11 are the columns of the second level. At this level, the actuator is placed and the diagnostic signal (the given dynamic impact) is formed - the column with pt. А8. Three control points are placed in the central parts of the overlap discs between the columns at the level of the second overlap. Under point A7 there is an artificially introduced defect simulating a crack. The actuator exposure time is 1 mS. The response of the structure is monitored for 10 mS. The totality of the obtained numerical results determined the evolution of the vibration portraits of the structure related to the development of the crack. The first portrait was obtained for a structure without a defect and three more for a structure with a crack whose depth increased. Results and discussion The analysis of the obtained vibration accelerations shows (for example, in the most characteristic point - pt. A7, for the component normal to the surface - z) that as the defect depth increases, the signal undergoes significant changes (Figure 5). We can see changes in both the amplitude and phase characteristics of the signal.

Fig. 5 Accelerations (Az) for the reference pt. A7z for the cases: construction without defect; with introduced defect of different depth - 30 mm, 60 mm, 100 mm. Half of the total signal time is shown - 5 mS.

An important part of the vibration response analysis is the Fourier analysis of the signal frequency spectrum. In particular, the evolution of the defect can also be clearly seen by the change in the spectrum (Figure 6).