Stress concentration, isolated

Generally, realizing effective reinforcement of CNTs in polymer needs two factors (21) (1) good dispersion in matrix, and (2) strong interface strength between CNTs and polymer. Dispersion is probably a more fundamental issue. Nanotubes must be uniformly dispersed as isolated nanotubes and individually coated with polymer. This results in a more uniform stress distribution and minimizes the presence of stress-concentrated centers. Furthermore, strong interface between CNTs and polymer leads to efficient stress transfer... 

Stress concentrations around isolated spherical inclusions in an isotropic matrix have been calculated by Goodier (10), but apparently there is no satisfactory theory for the problem of concentrated dispersions. A simple approach would be to use Goodier s equation and to allow for the effect of the high concentration of rubber particles simply by adding the calculated stress concentrations that arise from neighboring particles. 

Stress Bate at Particles. The stress component, avv, acting parallel to the boundary between rubber particles and matrix is important for the initiation of crazes. It reaches a maximum value (which can be about twice the outer stress, a0) at the equatorial regions of the particles. Besides depending on the shape of the particles and Poisson s ratio, the elastic-stress concentration at the rubber particles depends mainly on the ratio x = Gp/GM, where GP and GM are the Youngs modulus of the particles and the matrix, respectively. This ratio has been calculated by Michler (14) on the basis of the solution obtained by Goodier for an isolated particle embedded in a matrix and subjected to uniaxial tension (15) (see Figure 9). 

The abutment pressure at the fully mechanized working face of three soft coal seam isolated island has significant effect on strata behavior and strata behaviors such as floor heave, deformation or wall caving of roadways or explosion of props, etc mostly occur in the stress concentration zone. Moreover, roof integrity also has great affect on strata behavior. 

Strength, unlike elastic modulus, is not even theoretically a readily determinable quantity. Overall elastic-plastic deformation in a structural adhesive might be describable in terms of intermolecular forces and models of viscous flow, but not at the discontinuous moment of fracture. In fact overall behaviour loses sight of the fact that it is normally isolated phenomena that control the magnitude of joint strength and the locus of failure (see Stress distribution mode of failure). The term isolated phenomena refers to voids, cracks, second phase material, and so on, which can act as stress concentrators. Clearly, it would be unwise to suggest that an adhesive bond tester should merely locate and size voids and cracks, as whether or not such a defect is active depends upon where it lies in the working stress pattern of the structure. 

The explanation of the effect of secondary component on the spreading of shear yielding (i.e., delocalization of shear banding) is based on a concept of local stress fields and stress concentrations in the matrix due to the presence of inclusions. This leads to a reduction of the external load needed to plastically deform the material. The original Goodier s solution (7) for an isolated particle in an isotropic matrix resulted in a maximum stress concentration of about 1.9 at the equator of the inclusion (8). It should be borne in mind that this solution... 

Although it is widely accepted that ischaemia/ reperfusion-induced oxidant stress is associated with a reduction of Na/K ATPase activity, it is difficult to determine which features of this process are responsible for this effect. A classical approach to this type of problem has been to determine the effect of the application of selected metabolites or agents on the activity of the enzyme of interest, an approach that has been exploited for the sarcolemmal Na/K ATPase and glutathione (Haddock et al., 1990). The application of GSH (O.l-l.OmM) induces a concentration-dependent increase in the activity of a bovine isolated ventricular Na/K ATPase preparation (determined by the ouabain-sensitive hydrolysis of ATP to release inorganic phosphate). In the presence of 1 mM GSH there was a 38% stimulation of activity compared to untreated control... 

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