The Studies On Damping Properties Of Viscous Elastic Damping Shock Absorbing Material And Constrained Damping Structure

In Qingdao, the vibration and noise caused by subway operation are much stronger than other cities with the soft subgrade for the complicated geological conditions and the magmatic rocks (granite)-type hard embankment in Qingdao. To solve this problem, a viscoelastic damping material was studied in this paper and constrained damping mechanism was introduced into rail traffic. The main research contents and the results are following:First, with the dynamic mechanical spectroscopy (DMA)research, it suggested that the type of hard segment, hard segment content and frequency, temperature, bubbles, etc of viscoelastic damping material were the main factors that affected the damping loss factor, loss modulus, storage modulus, damping, etc. The peak of damping loss factor and the range of damping temperature could be regulated by adjusting the type of hard segment and content of hard segment. With the pre-polymer hard segment content increasing, the peak temperature of the sample gradually increased and the damping loss factor decreased slightly while the damping temperature range became wider. When the frequencies were 5Hz. 33.3Hz and 50Hz, as the temperature increasing, the damping loss factor showed the phenomenon of a decline after growth; as the frequency increasing, the peak point of the loss factor moved to high temperature, the peak tended to increase and the damping temperature range broadened. Between -80℃and 10℃, the loss factor of viscoelastic materials increased from 0.1 to 0.75. Between 10℃and 50℃, the loss factor of viscoelastic materials decreased to 0.45 and then remained stable until 100℃. The presence of bubbles made the peak of damping loss factor shift to the low temperature region, but the maximum of damping loss factor had no significant change. The peak of loss factor of damping materials moved to the high temperature with little change in peak after the bubbles removed.Second, the influencing factor of constrained damping structure were studied, including damping layer thickness and different damping materials. The results showed that the thicker the density between layer and layer of constrained damping structure were, the higher the complex damping loss factor were and the more excellent damping effect were. In the first, second and third frequency, coMPared to the 50% coMPact structure, complex loss factor of the 100% coMPact structure increased 0.1293, 0.04347 and 0.00645 distinctly. Between 1Hz and 1000Hz, constrained damping structure had excellent damping properties. And the thinner coating had the better the damping effect. The complex loss factor of viscoelastic constrained damping structure was 7~22 times bigger than undamped and epoxy damping structure. In the frequency range of 3.15Hz-3150Hz, viscoelastic damping structure had the best performance in damping affect. At 200Hz, the vibration acceleration level of the viscoelastic constrained damping structure was 47.532dB, which reduced 2.81dB coMPared to epoxy structure, reduced 4.048dB coMPared to epoxy damping structure and reduced 7.681dB coMPared to undamped structure.With the viscoelastic damping structure, the vibration was fast attenuation and short duration. The maximum amplitude of the viscoelastic damping structure was only as 269.402 mm/s2, which was smaller than undamped structure and epoxy structure, and sustained just 0.03s.Third, the viscoelastic damping material adhesion to the substrate processing system was discussed, including the apparent quality, temperature and humidity effects on adhesion. The results showed that: Qtech-112 had a good closed effect on the concrete surface of the substrate processing system; and with the temperature increased, the adhesion of concrete, respectively, would be up to 6.13MPa, 6.83MPa and 6.39MPa; and there were a complex condition with the change of humidity. To Q-1 and Q-2, the adhesion of concrete firstly raised to 7.27MPa and 6.20MPa, and then reduced to 5.78MPaand 4.38MPa, while Q-3 adhesion to the concrete continued to rise as the humidity increases, up to 7.15MPa.Through the experimental studies and theoretical analysis, this paper not only provided a theoretical basis for the problem that viscoelastic damping material was used in the vibration resistance and noise reduction on hard subgrade, but also played reference for the application of vibration of the rail transit noise.