Damping performance

The development of constrained-layer damping materials through the use of dynamic mechanical testing and mathematical modeling has been described. It has been shown how different types and loadings of fillers will affect the measured viscoelastic properties of chlorobutyl rubbers. It has then been shown how these changes will affect the damping performance of these materials in constrained layer structures. 

Figure 8. Design of a barbell test assembly used to evaluate the extensional damping performance of constrained-layer treatments.

Figure 9. Calculated vs. measured extensional damping performance for the Figure 8 test assembly.

The damping performance of a free layer treatment for plate bending waves is shown in Figure 4 (lH,UL) This chart, which is Oberst s result, gives the system loss factor T relative to T 2/ the loss factor of the viscoelastic material, as a function of the thickness ratio H2/H1 (viscoelastic layer to plate). Each of the several curves corresponds to a particular value of the relative Young s storage modulus E2/E1 (viscoelastic layer to plate). 

Figure 14. Measured Damping Performance of Thickness-Resonant Viscoelastic Layer X is the wavelength of compressional waves in the viscoelastic layer) (Adapted with permission from Ref. 38 Copyright 1964 The American Institute of Physics.)...

Addition of LS as a compatibilizer reduced the damping performance of the NR/PUR blend, indicating reinforcing efficiency. For the NR phase, its tan 8 peak was shifted slightly to lower temperatures, while for the PUR phase a slight shift to higher temperatures is seen. The first shift hints at limited... 

However, the existing artificial reef concepts have serious drawbacks the wave damping performance is limited and sometimes not sufficient. Moreover, the overall hydraulic performance is difficult to control, due to the limitations associated with the variation of the structure parameters, etc. Therefore, a reef concept made of submerged permeable screens with predetermined porosity and spacing has been experimentally tested in the Large Wave Flume of Hannover (GWK). As schematically shown in Fig. 12.8 for a three-filter system, this new reef concept is particularly appropriate for the protection of such coastal areas which are frequently used for recreation activities. 

Using a conventional reef made of rubble material would require a very wide structure and a progressive decrease of the porosity in wave direction in order to achieve a satisfactory wave damping performance. This is not only costly and difficult to construct and to maintain, but it is also very difficult to control the hydraulic performance by means of a variation of the structme parameters as it is the case for this new artificial reef concept. 

Fig. 7.21 Damping performance of the integrated system. The integrated damping system has been activated in the 3rd second.

Fig. 7.20 Test stand for the damping performance investigation of the fiber-reinforced rotor with integrated active damping systems.

For seismic design, JSFR adopts an advanced seismic isolation system for SFR that mitigates the horizontal seismic force by thicker laminated rubber bearings with a longer period and the improvement of damping performance by adopting oil dampers (Okamura, 2011). 

Because the JSFR pump shaft is long ( 15 m) in height, a damper is installed at the lower bearing to increase rotation stability. A full-scale mock-up of the lower pump shaft bearing with a damper has been manufactured, and water tests at 80°C with the same viscosity condition of sodium have been conducted, accumulating data of shaft holding force and damping performance. 

The objective here is to understand the damping properties of joints bonded with various adhesives and to see how this might affect the overall damping of a structure. Some variables to be examined are the effects of adhesive properties, joint geometry, and temperature on the overall damping performance of a joint. 

To quantify damping performance, the area imder the tan 5 or " vs temperature curves may be used. The loss area is given [250] as ... 

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