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Modulus interaction

A further interaction between the dislocation and the solid solution atom is due to the different strength of the atomic bond between the dissolved atom and its neighbours, resulting in a locally changed elastic modulus in the vicinity of the solid solution atom. The line tension of the dislocation thus either increases or decreases when it approaches the atom, causing another obstacle effect known as modulus interaction. [Pg.204]

One possible mechanism is the modulus interaction, already discussed in another context in the chapter on metals (section 6.4.3). If the particles have a larger Young s modulus than the matrix, the matrix is partly unloaded in the vicinity of the particles, and the stress available to propagate the crack is reduced. The crack is deflected away from the particle (see figure 7.2). If Young s modulus of the particles is smaller than that of the matrix, the stress is raised in the vicinity of the particles, and the crack is attracted by the particle. If the crack cannot penetrate the particle, the crack must proceed along its boundary. In all these cases, the crack path becomes longer. [Pg.230]

Abstract. This paper presents results from quantum molecular dynamics Simula tions applied to catalytic reactions, focusing on ethylene polymerization by metallocene catalysts. The entire reaction path could be monitored, showing the full molecular dynamics of the reaction. Detailed information on, e.g., the importance of the so-called agostic interaction could be obtained. Also presented are results of static simulations of the Car-Parrinello type, applied to orthorhombic crystalline polyethylene. These simulations for the first time led to a first principles value for the ultimate Young s modulus of a synthetic polymer with demonstrated basis set convergence, taking into account the full three-dimensional structure of the crystal. [Pg.433]

Transparent, homogeneous hybrids using a 50 50 PVAc-to-TEOS mixture and an acid-catalyzed reaction have been produced and characterized by dsc and dms (46). Dsc indicated only a slight increase in the T of the hybrid with incorporation of sihca. Dynamic mechanical tan 8 responses indicate a strong interaction between the organic and inorganic phases and, hence, weU-dispersed phases that lead to high modulus mbbery plateaus. [Pg.329]

A guide to tire stabilities of inter-metallic compounds can be obtained from the semi-empirical model of Miedema et al. (loc. cit.), in which the heat of interaction between two elements is determined by a contribution arising from the difference in work functions, A0, of tire elements, which leads to an exothermic contribution, and tire difference in the electron concentration at tire periphery of the atoms, A w, which leads to an endothermic contribution. The latter term is referred to in metal physics as the concentration of electrons at the periphery of the Wigner-Seitz cell which contains the nucleus and elecUonic structure of each metal atom within the atomic volume in the metallic state. This term is also closely related to tire bulk modulus of each element. The work function difference is very similar to the electronegativity difference. The equation which is used in tire Miedema treatment to... [Pg.220]

Hertz [27] solved the problem of the contact between two elastic elliptical bodies by modeling each body as an infinite half plane which is loaded over a contact area that is small in comparison to the body itself. The requirement of small areas of contact further allowed Hertz to use a parabola to represent the shape of the profile of the ellipses. In essence. Hertz modeled the interaction of elliptical asperities in contact. Fundamental in his solution is the assumption that, when two elliptical objects are compressed against one another, the shape of the deformed mating surface lies between the shape of the two undeformed surfaces but more closely resembles the shape of the surface with the higher elastic modulus. This means the deformed shape after two spheres are pressed against one another is a spherical shape. [Pg.144]

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... [Pg.193]

One can see that the relative elongation is lower in composites, but the modulus and, what is particularly important, durability of samples is higher. Obviously, the interaction between the polymeric coat and the matrix is particularly important in materials of this kind. This is illustrated by the data of Table 13 below. [Pg.51]


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See also in sourсe #XX -- [ Pg.204 , Pg.230 , Pg.232 , Pg.251 , Pg.255 ]




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