82 M. Jonkeren and S. Tatzko damping ratio increases with an increase of rotational speed. This trend is observable across the entire speed range. These results demonstrate a qualitative trend that is in accordance with the findings of [8]. This tendency is not as pronounced for the gear G-02 with the small cavities, but a slight increase can also be observed. Fig. 4 Calculated damping ratios of the examined vibration mode for the fully fused gear and the two gears with integrated powder-filled cavities. The graphs show linear interpolation between calculated damping ratios at discrete rotational speeds. Corresponding standard deviations are indicated by transparent areas. Conclusion In conclusion, this experimental study investigates the dynamic response of three additively manufactured gears excited with a deterministic impulse excitation signal. The system response is measured using a laser vibrometer that rotates synchronously with the gear to capture the decaying time history at various rotational speeds. By conducting ten measurements at each rotational speed and analyzing the frequency spectrum of the system response, the decaying time data were filtered to isolate and examine one specific mode. The damping ratio for this vibration mode was calculated for each rotational speed. The results demonstrate that the damping increases with rotational speed for powder-filled gears, especially those with large cavities. Damping of the fully fused gear did not show any dependence on rotational speed. These findings contribute significantly to the understanding of the benefits of particle damping in gear systems. In future, further investigations should aim to provide a detailed analysis of particle motions and interactions within the cavities under centrifugal load. It would be beneficial to analyze the trend in further studies at higher speeds in order to determine whether the damping ratio eventually reaches a plateau or whether it begins to decline at some point, as reported for example in [8]. A detailed analysis of the observed damping fluctuations at high speeds, in particular the outliers and speeds above 360 rpm, would be useful. It is important to determine whether these fluctuations are due to the system or are influenced by the test setup. This consideration is relevant as tangential forces can be induced during excitation by surface roughness and hammer tip, which may have a greater effect at higher speeds. References 1. Lu, Z., Wang, Z., Masri, S.F., and Lu, X. “Particle impact dampers: Past, present, and future”. Structural Control and Health Monitoring, 25(1):e2058 (2018) 2. Ehlers, T., Tatzko, S., Wallaschek, J., and Lachmayer, R. “Design of particle dampers for additive manufacturing”. Additive Manufacturing, 38:101752 (2021) 3. Ehlers, T. and Lachmayer, R. “Design of particle dampers for laser powder bed fusion”. Applied Sciences, 12(4):2237 (2022)
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