An efficient way of mitigating noise and vibration is to embed viscoelastic patches into the host structure. Viscoelastic properties are of significant importance in determining the performance of the passive damping treatment. The behaviour of homogeneous isotropic materials is described
by two elastic constants (generally the Young modulus and the Poisson ratio, or the shear and bulk moduli), which are frequency- and temperature-dependent in the case of viscoelastic materials. In practice, the Poisson's ratio is often considered as independent of temperature and frequency.
One goal of this work is to numerically evaluate the validity of this assumption and its limitations (frequency range, thickness of the viscoelastic layer). To this end, a thermo-mechanical characterization of a viscoelastic material is carried out by dynamic measurements of the complex shear
and bulk moduli, allowing the indirect measurement of the frequency- and temperature-dependent Poisson's ratio. Moreover, the measurements of the Poisson's ratio (direct or indirect) can lead to considerable uncertainties. For instance, large discrepancies have been observed when characterizing
the Poisson's ratio of polymer foams. Another goal of this work is to investigate the influence of those uncertainties on the dynamic response of a damped structure.
Polymer matrix composites have been used in several applications of engineering and applied sciences. This wide range of applications is due to their distinguished properties. Therefore, the great understanding of their physical and mechanical properties is required to make an efficient use of these materials. Among the experimental techniques, Dynamic mechanical analysis (DMA) is one of the most common methods employed to study the materials' composition and properties. This work presents an investigation on the mathematical formulation for complex modulus determined by this technique and how it is evaluated. Measurements of temperature-dependent complex modulus were performed by three different dynamic mechanical analyzers using threepoint bending mode. Test conditions were basically the same in these different machines. Comparisons of the results were made in order to observe the effects of testing equipment and test parameters.
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Soot deposit accumulation on heat transfer tubes and surfaces in recovery boilers reduces thermal performance, compromising thus the efficiency and life of the equipment. A soot blower is employed to remove these by-products to maintain boilers within design conditions. This specialized device has a seal between its tubes to maintain fluid pressure to clean the heating pipes and inside surface. Nevertheless, sealing can be a challenge due to its large displacement amplitude, the reciprocating movement, and the sudden change of temperature and pressure. Many different solutions are available in the market that offers viable sealing methods, but there is no test method to classify them. This work proposes a soot blower test protocol to evaluate the sealing solutions available. Comparative results for the different seal types are presented.
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