Internal shear stresses

In the amorphous pattern we observe a spatial fluctuation of density as well as different repulsive and attractive forces. Describing the amorphous structure with (n — m)/n = x and using the 6—12-potential of Eq. (5) we obtain an internal shearing stress... 

Thixotropic. The flow rate of a thixotropic substance increases with increasing duration of agitation, as well as with increased shear stress. When agitation is stopped, internal shear stress exhibits hysteresis. Upon reagitation. generally less force is required to create a given flow than is required for first agitation. 

A widely accepted theory for lamination presented by Long [29] and reformulated by Ritter and Sucker [30] attributes capping to the residual die wall pressure. This pressure is said to cause internal shear stresses in the tablet causing the propagation of cracks, which results in lamination or capping. The propagation of cracks can be prevented by plastic relaxation of shear stresses. Therefore, materials having sufficient plasticity may not be susceptible to lamination. Some properties of the powder mixture, such as moisture content, type and amount of the binder, and... 

In our attempt to differentiate between fluids and solids, we can now say that solids are substances which can permanently resist very large shear forces. When subjected to a shear force solids move a short distance (elastic deformation), thereby setting up internal shear stresses which resist the external force, and then they stop moving. Materials that obviously are fluids cannot permanently resist a shear force, no matter how small. When subjected to a shear force, fluids start to move and keep on moving as long as the force is applied. 

Real liquids are viscous and are characterized by internal shear stresses and viscous dissipation of energy. The processes occurring in a viscous liquid are thermodynamically irreversible and have spatial heterogeneity. 

If a shear force is imposed on the rib, two critical planes of internal shear stress occur, one at the neutral axis and one at the plane between the mat and the fabric in the flange. Shear stresses are computed. 

Fibrous reinforced plates in practice are often made up of several layers, and the individual layers may be of different construction, such as mat, fabric, or roving. Furthermore, the various layers may be oriented at different angles with respect to each other in order to provide the best combination to resist some particular loading condition. Outside loads or stresses applied to a RP plate of this type result in internal stresses that are different in the individual layers. External direct stresses may result not only in internal direct stresses but in internal shear stresses and external shear stresses may result in internal direct stresses as well as internal shear stresses. 

The surface sources Qs are the result of the work done on the fluid by the internal shear stress acting on the surface of the control volume ... 

This proves what might have been expected intuitively, that because of symmetry with respect to the 1—2 directions chosen the internal direct stresses Cia, Ci, o 2a, nnd 0 2 are equal to the imposed stresses ai and (T2, and there is no internal shear stress. 

Ability to generate high enough internal shear stresses to facilitate good dispersion of all additives and glass fibers... 

In Cases 1 and 2 the orientation of the fibers with respect to the 1-2 directions chosen resulted in zero shear stresses associated with those directions, whereas in Case 3 the shear stresses were not zero. In all three cases, symmetry of the fiber orientations with respect to the stress directions resulted in internal stresses equal to the external stresses. These are special cases. In the more general case the internal direct stresses in the individual layers are not necessarily equal to the external direct stresses, nor are they the same in the various layers. Furthermore, even symmetrical Case 3 leads to internal shear stresses when external shear stresses are absent. In the more general case it is still more true... 

In a liquid with a low viscosity or in a gas, the switching can take place spontaneously without the application of stress. For solid thermoplastic polymers, a first approximation is to assume that the application of external forces creates an internal shear stress sufficient to cause an atom to escape the energy well shown in Fig. 2.22(e) and Fig. 11.1(b) (D is the dis-association energy) and thus enable switching. 

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