Energy-dissipating properties

Enzymatic Polymerization Products Possess Increased Energy Dissipation Properties. Interestingly, starting at point 2 in Fig. 4b, the/ and R values... 

DMA provides materials scientists, pol5mer chemists, and design engineers with detailed information on the elastic and inelastic (plastic) deformation of materials, modulus, and damping (energy dissipation) properties of materials. The damping behavior of S5mthetic and natural mbbers is important in vibration and acoustic application, for example. 

Smart materials. Materials that have the capability to respond to an external stimulus by changing, in a controlled manner according to prescribed functional relationships or control algorithms, their energy dissipation properties and geometric configuration, or by changing their stiffness. 

The implications of this point of view are explored for an understanding of 1) the elastic (energy storing) property of hyaluronate solutions and 2) the two kinds of energy dissipating properties (intrinsic and internal viscosity) of such solutions. 

Formulation provides impact energy dissipation properties, and long-term service use stabihty... 

In addition, it is clear from the derivation of Eq. (5) that U represents the energy obtainable from the deformed material rather than the energy put into deforming it. For a material with energy-dissipating properties, the energy available for fracture is only a fraction of that supplied. Such a material will therefore appear doubly strong in a tensile test or in any other fracture process... 

The technique also measures the modulus (stiffness) and damping (energy dissipation) properties of materials as they are deformed under periodic stress. Such measurements provide quantitative and qualitative information about the performance of the materials. The technique can be used to evaluate elastomers, viscous thermoset liquids, composite coatings, and adhesives, and materials that exhibit time, frequency, and temperature effects or mechanical properties because of their viscoelastic behaviour. 

DMA, or DMTA (dynamic mechanical thermal analysis) as it can also be called, measures the modulus (stiffness) and damping (energy dissipation) properties of polymers as a function of temperature as they are deformed under a periodic stress. This latter criterion distinguishes this technique from the closely related one of TMA, which is a static technique. Because DMA is able to provide information on the viscoelastic properties of polymers, it has a greater capability than TMA and this is why the latter will not be included in this section, but is covered in Section 6.3.6. 

Fig. 2. Schematic of energy dissipation in a commonly used peel test. The energy dissipation can occur in the adhesive and/or the adherends. The extent of energy dissipation depends on the elasto-plastic properties of the adhesive and the adherends under the test conditions as well as the local stresses and strains near the crack tip.

As is true for macroscopic adhesion and mechanical testing experiments, nanoscale measurements do not a priori sense the intrinsic properties of surfaces or adhesive junctions. Instead, the measurements reflect a combination of interfacial chemistry (surface energy, covalent bonding), mechanics (elastic modulus, Poisson s ratio), and contact geometry (probe shape, radius). Furthermore, the probe/sample interaction may not only consist of elastic deformations, but may also include energy dissipation at the surface and/or in the bulk of the sample (or even within the measurement apparatus). Study of rate-dependent adhesion and mechanical properties is possible with both nanoindentation and... 

Strength and Stiffness. Thermoplastic materials are viscoelastic which means that their mechanical properties reflect the characteristics of both viscous liquids and elastic solids. Thus when a thermoplastic is stressed it responds by exhibiting viscous flow (which dissipates energy) and by elastic displacement (which stores energy). The properties of viscoelastic materials are time, temperature and strain rate dependent. Nevertheless the conventional stress-strain test is frequently used to describe the (short-term) mechanical properties of plastics. It must be remembered, however, that as described in detail in Chapter 2 the information obtained from such tests may only be used for an initial sorting of materials. It is not suitable, or intended, to provide design data which must usually be obtained from long term tests. 

The model is able to predict the influence of mixing on particle properties and kinetic rates on different scales for a continuously operated reactor and a semibatch reactor with different types of impellers and under a wide range of operational conditions. From laboratory-scale experiments, the precipitation kinetics for nucleation, growth, agglomeration and disruption have to be determined (Zauner and Jones, 2000a). The fluid dynamic parameters, i.e. the local specific energy dissipation around the feed point, can be obtained either from CFD or from FDA measurements. In the compartmental SFM, the population balance is solved and the particle properties of the final product are predicted. As the model contains only physical and no phenomenological parameters, it can be used for scale-up. 

Hetsroni et al. (2005) evaluated the effect of inlet temperature, channel size and fluid properties on energy dissipation in the flow of a viscous fluid. For fully developed laminar flow in circular micro-channels, they obtained an equation for the adiabatic increase of the fluid temperature due to viscous dissipation ... 

Unlike traditional textbooks of tribology, in this book we regard boundary lubrication as a limit state of hydrodynamic lubrication when film thickness is down to molecular dimension and independent of the velocity of relative motion. The discussions are based on the existing results, some from literatures but mostly from the authors own work. The topics are mainly focused on the mechanical properties of boundary films, including rheology transitions, molecular ordering, and shear responses. Ordered molecule films, such as L-B films and SAM, are discussed, with emphasis on the frictional performance, energy dissipation and the effects from structural features. Boundary films can be modeled either as a confined substance, or an adsorbed/reacted layer on the... 

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