# Numerical and Experimental Investigations of Particle Dampers Attached to a Pipeline System
## 4 Experimental Verification of the Damping Performance of the Pipeline System
### Damping Performance Test of Particle Damper under Basic Harmonic Excitation  
2.1 Influence of Different Materials of Four-Cavity Dampers on the Vibration Damping Performance of Pipeline  
The four-cavity particle dampers made of two materials that were used in the test are shown in Figure 18. The dampers were filled with steel particles with a particle size of 2 mm using a 60% filling rate.  
The frequency range of the sinusoidal swept excitation was 10-2000 Hz, and the resonance frequencies of the bare pipeline and the four-cavity particle damper with different materials were obtained. The first-order resonance frequency was chosen to be the sinusoidal frequency, and the excitation frequencies tested were 83 Hz, 46 Hz, and 43 Hz, and the comparative time and frequency domain responses of the pipeline system before and after the addition of the four-cavity particle damper with different materials were obtained (Figure 19).  
Figure 17: Experimental setup for the vibration test.  
Figure 18: Filling effect of four-cavity particle damper made of two different materials.  
As shown in Figure 19, the time domain and frequency domain responses of the tubing with the particle damper made of two different materials were significantly reduced compared to that of the bare pipeline. The first-order frequency of the four-cavity particle dampers made of ABS and aluminum alloy was reduced by 83.66% and 85.29%, respectively, compared to that of the bare pipeline. The first-order amplitude of the four-cavity particle damper made of aluminum alloy decreased by about 9.97% compared with that of the damper made with ABS. This shows that the particle damper with these two materials can achieve good damping effects, and the four-cavity damper made of aluminum alloy has better damping effects.  
2.2 Influence of Different Materials of Six-Cavity Dampers on the Vibration Damping Performance of Pipeline  
Six-cavity particle dampers made of ABS or aluminum alloy were tested and are shown in Figure 20. The damper was filled with steel particles with a particle size of 2 mm and a filling rate of 60%.  
The ABS and aluminum alloy six-cavity particle dampers were attached to the cantilever pipeline. The excitation frequencies used were 83 Hz, 49 Hz, and 45 Hz, and the comparative time and frequency domain responses of the pipeline system before and after the attachment of the six-cavity particle damper made of different materials are shown in Figure 21.  
Figure 19: Vibration response of a four-cavity particle damper using two different materials.  
Figure 20: Filling effect of six-cavity particle dampers made of two materials.  
As shown in Figure 21, compared with the bare pipeline, the time and frequency domain responses of the six-cavity particle dampers attached to the pipeline were greatly reduced. The frequency domain amplitudes corresponding to the first-order frequency were reduced by 80.35% and 84.20%, respectively. The frequency domain amplitude of the six-cavity particle damper with aluminum alloy material added to the pipeline was the smallest at about 2.91 g. Meanwhile, compared to the ABS material six-cavity particle damper, the frequency domain amplitude decreased by about 19.61%. This indicates that the six-cavity damper made of aluminum alloy had a better damping effect.