PSI - Issue 54

Jakub Gorski et al. / Procedia Structural Integrity 54 (2024) 264–270 J. Gorski et al. / Structural Integrity Procedia 00 (2023) 000–000

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Fig. 1. Idea of the MT phenomenon for elastic waves in structures.

3. Experiment description

Experimental studies were carried out using a prepared stand. The test objects were two aluminium beams - dam aged and undamaged. One end of each specimen was restrained using a pneumatic clamp. A piezostack actuator and a piezoceramic transducer were attached to the other end to introduce pumping and probing excitations into the structure. The response signals of the structure were measured non-contacting using a laser vibrometer. The selected measurement points were positioned along the axis of the tested beam. Figure 2 shows a schematic diagram of the beam dimensions. The test bench is presented in figure 3. The excitation parameters were selected as follows. The car

Fig. 2. Dimensions of the damaged beam with measurement points.

rier frequency of the pumping excitation was determined after modal analysis on the undamaged and damaged beam. Three frequencies were identified for both beams. Values of f l f = 4167 Hz for the undamaged one and f l f = 3798 Hz for the damaged one were selected for further experiments. Despite the di ff erence in values, these frequencies produce a similar mode shape as shown in Figure 4. The modulation signal’s frequency was configured to f M = 43 Hz . The probing excitation frequency was f hf = 131 kHz . This value was selected using trial and error to ensure the highest possible signal-to-noise ratio for response signals. It should be added that this value is related to the transducer generating the probing wave rather than the structure under the test itself.