Dynamic properties of materials

Isbell, W.M., Christman, D.R., Babcock, S.G., Michaels, T.E., and Green, S.J., Measurements of Dynamic Properties of Materials, Vol 1 Summary of Results, US Defense Atomic Support Agency Report No. DASA-2501-1, Washington, DC, 28 pp., July 1970. 

This section describes the dynamic properties of materials used in structures designed to resist blast loads at petrochemical facilities. Static properties are available from a number of references and are not repeated in this chapter, except to indicate minimum acceptable values. Dynamic response of these materials iias been studied extensively however, their dynamic properties arc not as widely published. Procedures for obtaining these properties will be covered here in sufiicicnt detail to permit an accurate determination for design and analysis of petrochemical structures. 

In addition to quantitative estimates of material properties, molecular modeling can offer valuable qualitative insights into the dynamical properties of materials, without resorting to direct simulation (e.g., molecular dynamics), where the rigorous treatment of all the dynamics at the atomic scale would be prohibitively time-consuming. To illustrate this point, the second part of this chapter describes recent studies of the relaxation in the crystalline a-phase of PVDF. Molecular modeling provides a way to characterize the mechanism of... 

Parsons, J. S., Yates, WAllace, and Scholoss, The measurement of dynamic properties of materials using Transfer Impedance Technique. Report 2981, Naval Ship R D center, Washington, D. C., April, 1969. 

Prediction of the structures and properties of materials from a knowledge of their chemical composition has been a longstanding problem of materials science. The Molecular Dynamics method (MD, hereafter) has been one of the most powerful techniques to simulate both static and dynamical properties of materials starting from atomistic information, i.e. an interatomic potential, which we expect not to be affected by a small change in environment of the atoms... 

The measurements of the propagation characteristics of the capillary wave, e.g., the propagation velocity and the damping coefficient, are effective for the study of the dynamic properties of materials existing on the gas-liquid interface. The theoretical studies for the insoluble monolayers have been performed by Dorrestein, Mayer and Eliassen", and Mann and Du, while those for the soluble monolayer have been performed by van den Tempel and van de Riet, Hansen and Mann, and Lucassen and Hansen. The former has developed their theories taking account of the surface rheologies, and the latter with the assumption that the rate-determining step of surfactant transfer between the surface and the bulk phase is the diffusion process. 

The elastic and viscoelastic properties of materials are less familiar in chemistry than many other physical properties hence it is necessary to spend a fair amount of time describing the experiments and the observed response of the polymer. There are a large number of possible modes of deformation that might be considered We shall consider only elongation and shear. For each of these we consider the stress associated with a unit strain and the strain associated with a unit stress the former is called the modulus, the latter the compliance. Experiments can be time independent (equilibrium), time dependent (transient), or periodic (dynamic). Just to define and describe these basic combinations takes us into a fair amount of detail and affords some possibilities for confusion. Pay close attention to the definitions of terms and symbols. 

When the two liquid phases are in relative motion, the mass transfer coefficients in eidrer phase must be related to die dynamical properties of the liquids. The boundary layer thicknesses are related to the Reynolds number, and the diffusive Uansfer to the Schmidt number. Another complication is that such a boundaty cannot in many circumstances be regarded as a simple planar interface, but eddies of material are U ansported to the interface from the bulk of each liquid which change the concenuation profile normal to the interface. In the simple isothermal model there is no need to take account of this fact, but in most indusuial chcumstances the two liquids are not in an isothermal system, but in one in which there is a temperature gradient. The simple stationary mass U ansfer model must therefore be replaced by an eddy mass U ansfer which takes account of this surface replenishment. 

Karnes, C.H., The Plate Impact Configuration for Determining Mechanical Properties of Materials at High Strain Rates, in Mechanical Behavior of Materials Under Dynamic Loads (edited by Lindholm, U.S.), Springer-Verlag, New York, 1968, pp. 270-293. 

Molecular dynamics simulation, which provides the methodology for detailed microscopical modeling on the atomic scale, is a powerful and widely used tool in chemistry, physics, and materials science. This technique is a scheme for the study of the natural time evolution of the system that allows prediction of the static and dynamic properties of substances directly from the underlying interactions between the molecules. 

All the macroscopic properties of polymers depend on a number of different factors prominent among them are the chemical structures as well as the arrangement of the macromolecules in a dense packing [1-6]. The relationships between the microscopic details and the macroscopic properties are the topics of interest here. In principle, computer simulation is a universal tool for deriving the macroscopic properties of materials from the microscopic input [7-14]. Starting from the chemical structure, quantum mechanical methods and spectroscopic information yield effective potentials that are used in Monte Carlo (MC) and molecular dynamics (MD) simulations in order to study the structure and dynamics of these materials on the relevant length scales and time scales, and to characterize the resulting thermal and mechanical proper-... 

A development of the moving die rheometer where the operation of the unit is fully computer controlled. The rate of oscillation, temperature and level of strain can all be run through a series of options. The torque measurements are also highly sophisticated. As a consequence, the unit can be set up to monitor processing parameters, then the cure behaviour and finally the finished dynamic properties of the cured material. It is manufactured by Alpha Technologies. 

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