PSI - Issue 77

Francisco Afonso et al. / Procedia Structural Integrity 77 (2026) 584–592 F. Afonso et al. / Structural Integrity Procedia 00 (2026) 000–000

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DAQ Data acquisition SDK Software Development Kit FFT Fast Fourier Transform

2. Experimental setup

The experimental setup was based around a single specimen, a Thermaltake TT-1225 fan. This 120 mm computer fan was mounted on an optical table, held in place by Thorlabs CL5 L-shaped clamps, which were assembled in such a way as to allow it limited freedom to vibrate. The specimen was powered by a 12V adjustable bench power supply, and an RS Pro Tachometer 193-8687 was used to measure the rotation speed, in rotations per minute (rpm). It was determined that the fan rotated at approximately 1950 rpm, i.e. 32.5 rps, when not under any load. In one of the setup variations, an M4 nut was attached to one fan blade, as a small mass, to unbalance the rotor and increase vibration amplitude. Under this condition, and using the same methodology, the fan rotated at approximately 1910 rpm, i.e. 31.8 rps. Figure 1 shows the fan, its holders, and the tachometer reading during operation.

(b) Tachometer measuring fan speed.

(a) Thermaltake fan mounted on optical table.

Fig. 1: Specimen mount and speed measurement.

In these tests, two di ff erent cameras were used: a neuromorphic Prophesee EVK4 camera, with 1280 × 720 resolu tion, and a Basler a2A1920-160umBAS, a conventional frame camera with a resolution of 1920 × 1200 pixels at 160 fps, used as a comparison point to the neuromorphic results. As previously mentioned, it was necessary to increase the vibration amplitude in some situations. This is due to the fact that, using a balanced fan with standard lenses, the vibration amplitude is too small to be seen. In this unbalanced situation, the event camera was paired with a standard 8 mm lens supplied by Prophesee. As a way to counter this issue, an alternative approach using a macro-photography lens setup was devised and used with both cameras. The macro setup was designed for a magnification value of 4.0 × , using the MachVis Online software tool, and includes:

• C-mount adapter : As both cameras expect C-mount lenses. • Smart focus device : For focusing the images. • Extension tubes : Two 120 mm extension tubes were used to achieve the 4.0 × magnification. • Retro ring : The retro ring allows the lens to be mounted on the setup in reverse. • Rodagon 80 lens : The actual lens itself, with a focal length of 80 mm.