Cross-section reduction

Microwave-absorbing materials are currently in high demand for many expanded EMI shielding and radar cross section reduction applications with both commercial and defense purposes. The nanostructured materials have attraction for microwave radiation absorbing and shielding materials in the high-frequency range due... 

Equation (7.3) states that the rate at which the fiber (or sheet) becomes thinner is proportional to the applied force, not the applied stress. This means that thinner and thicker regions suffer cross-sectional reduction at an equal rate. This expression also informs us that, for a given load, as the viscosity ri increases, the axial strain rate, e, decreases. This has very important implications in fiber drawing. In order to understand these implications, we need to examine the temperature dependence of viscosity. The temperature dependence of viscosity is given by the Eyring equation... 

The maximum possible value of is about 0.35. One can see that, according to Eq. (15), M rapidly oscillates between 1/(1 + ) and 1/(1 — ), thus displaying the cross-section reduction as well as enhancement, as utt changes, and the averaged value of M over the period is equal to 1. 

With this requirement profile, these steels can also be considered for applications in marine atmosphere or industrial atmospheres. The steels 1.4003 (X2CrNil2) and 1.4512 (X2CrTil2) are not likely to show any corrosion-related cross-sectional reductions, even over periods of several decades, with the exception of highly aggressive conditions. Crevice corrosion can be expected under heavy chloride exposure and in the presence of crevices. Such critical conditions do not result from seawater exposure only, but are also seen inland due to deicing salt, etc. The ferritic chromium steels are not, by the way, formulated with crevice corrosion resistance in mind [100]. 

A wall wiper can be Simula by a local reduction of foe wall channel cross-section as shown in Fig. S8. From the continuity equation the velocity change caused by the wall channel cross-section reduction can be calculated. 

Fig. 58. Contral volumes for the crossing at the wall with a cross-section reduction (wall wiper) (left) and the associated channels (right), [102],...

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