PSI - Issue 77

Job S. Silva et al. / Procedia Structural Integrity 77 (2026) 550–558 Author name / Structural Integrity Procedia 00 (2026) 000–000

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components. The experimental configuration is shown Fig. 5.

Fig. 5. Experimental setup of the reduced-scaled wagon with accelerometers.

After each test, the time-domain acceleration responses were recorded and post-processed in Python to calculate the PSD and perform SSI. 4. Results and Discussion This section presents and discusses the results obtained from the experimental and numerical investigations. The analyses include the time-domain responses of the accelerometers, the frequency spectra derived from the PSD, and the modal parameters identified using the SSI method. The results are then compared with the outcomes of the FE modal analysis.

Fig. 6. Time-domain acceleration responses of both platforms recorded during a hammer impact test.

Fig. 6 presents the time-domain acceleration responses recorded during a representative hammer impact on the scaled wagon model. Each platform was instrumented with a triaxial accelerometer, Fig. 6 shows the vertical component (Z direction) of the acceleration measured on platforms 1 and 2. Although the structure was not equipped with any dedicated damping elements, the recorded signals exhibit a distinct decay in amplitude following the impact. This behaviour indicates the presence of intrinsic damping mechanisms associated with material properties, joint interfaces, and frictional losses. Both platforms show consistent responses, indicating that the setup yields reliable, repeatable measurements of the global dynamic behaviour. The Power Spectral Density analysis provided a clear identification of resonance frequencies. The PSD spectra of the vertical acceleration components for both sensors are shown in Fig. 7. The most prominent peaks were found at approximately 12 Hz, 55 Hz, 138 Hz, 171 Hz, and 331 Hz for Platform 1, Fig. 7 - a, and 12 Hz, 55 Hz, 138 Hz, 171 Hz, and 338 Hz for Platform 2, Fig. 7 - b. The first mode, around 12 Hz, corresponds to a rigid-body type motion dominated by suspension compliance. Frequencies above 400 Hz were disregarded because they were attributed to local structural modes or measurement noise rather than global wagon behaviour.

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