Cavity thickness

As shown in the previous Example, the variation of cavity thickness with time is given by... 

Double or triple glazing may be provided in this case, the main criterion being that the cavity thickness between the layers of glass must be at least 20 mm. 

Poor impregnation will result if the fiber volume fraction is so low that a region without fibers is formed on top of the reinforcement. This can happen, for example, if high performance fabrics with a high uncompacted fiber volume fraction are used at a too-low-fiber volume fraction. This situation is similar to the race tracking problem described earlier. Flow on top of the reinforcement can occur, even if the whole cavity thickness is filled with fibers, if... 

The stiffness of the mold must be both high enough to keep a sufficiently uniform cavity thickness and so high that the sealing surfaces are kept sufficiently close to each other, particularly if small diameter O-ring seals are used. 

Fig. 16. Optimal mould temperature as a function of the inner cavity thickness for plastisols I (circles) and II...

To show how the above equations are used, let us consider a disc-shaped cavity of R =150 mm, a gate radius, n, of 5 mm, and a cavity thickness of 2 mm, i.e., h =1 mm. Assuming a Newtonian viscosity /. =6,400 Pa-s and constant volumetric flow rate Q =50 cm3/s predict the position of the flow front, r2, as a function of time, as well as the pressure distribution inside the disc mold. 

Optimization of the Angle of Incidence and the Thin-cavity Thickness... 

Fig. 9.6 Mean square electric field strength at the metal surface for a p-polarized beam as a function of (a) the angle of incidence at the thin cavity thickness shown, (b) the thin cavity thickness at the angle of incidence...

Table 9.1 The refractive index, reflectance of the air/window interface (at normal incidence), the maximum MSEFS at the metal surface, the coordinates of the maximum (thin cavity thickness and the angle of incidence), the fuii width at half maximum (FWHM) of the MSEFS for different opticai window materials and the low frequency cut off limit.

The previous section demonstrated that it is essential to control both the angle of incidence and the thin-cavity thickness in the IRRAS experiment. While it is usually not too difficult to control the angle of incidence, a measurement of the thin-cavity thickness with a precision of a fraction of a micrometer is not a trivial task. A new method [40] of determination of these important parameters is described in Fig. 9.12 for an experiment performed using Bap2 as the window, D2O as the solvent, and Au as the electrode. 

Fig. 9.12 (a) Total reflection from the empty cell (b) reflection from the filled cell (c) reflectivity spectrum of the setup (dashed line) experimental values (solid line) calculated using Fresnel formulae for Bap2/D20/Au interface and the angle of incidence of 60°. Thin-cavity thickness was determined to be 2.4 pm. 

The second method, developed by AUara et al. [42, 48, 49], relies on calculation of the theoretical reflection absorption spectrum for the same angle of incidence and the thin-cavity thickness as the values used during the collection of the experimental data. The optical constants of the window, electrolyte, and metal can be taken from the literature [22, 37-39], while the isotropic optical con-... 

The main advantage of this method is that the absolute value of 0 can be determined directly. Howevei supplementary information such as the surface concentration, the angle of incidence, the thin-cavity thickness, and the optical constants of the film have to be determined from independent measurements. Below, we show several examples of how to apply this method. 

Figure 5.77 Orientation developed during filling, (a) Across the cavity thickness (6) along the length of the cavity,...

Adopting a cartesian coordinate system and assuming the cavity thickness is small compared to the other dimensions, the mass and momentum equations may be reduced to the single equation... 

In the case of mold deformation, the cavity thickness his a function of the local pressure. Baaijens (1991) simply chose dh/dP = 0.4 pm/MPa and showed that a small amount of mold compliance can have a significant influence on the cavity pressure history, and neglect of the mold elasticity will lead to under-prediction of the cavity pressure. Pantani et al. (2001) assume the following relationship ... 

The GHS model is simple and computationally efficient because the formulation consists of only one governing equation in terms of one variable, namely, pressure. Whereas the GHS model applies to thin cavities, the Barone-Caulk model better predicts the flow of thick charge (Erwin and Thcker, 1995 Lee, 1984). The Barone-Caulk model characterizes the flow by uniform extension though the cavity thickness with a slip boundary condition between the charge surface layers and the mold surfaces instead of the no-slip condition that is adopted in the GHS model (Barone and Caulk, 1985,1986). For further information on the Barone-Caulk model, the readers are recommended to see the references providing comprehensive description and simulation examples (Davis et al, 2003 Tucker, 1987). 

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