Void imaging

Figure 13.25. Voids imaged by micro-focus X-rays in an attachment.

Fig. 13.9 A region near a wafer edge, showing edge damage at A, slip bands at B and voids at C. The (220 transmission) diffraction vector is vertical, resulting in a horizontal line of zero contrast on the void images. This is typical of a pure dilatation strain field caused by voids and precipitates.

Thermal imaging is sensitive to iafrared radiation that detects temperature changes over the surface of a part when heat has been appHed. Thermal diffusion ia a soHd is affected by variatioa ia composition or by the preseace of cracks, voids, delamiaatioas, etc the effects are detected by surface temperature changes. Defects cannot be detected if their depth below the surface is more than two to three times their diameter. Nondestmctive testing has been primarily used for composites and analysis of adhesive bonds or welds. Several studies are documented ia the Hterature (322—327). 

There are two different methods to experimentally define void fraction. The first is based on analyzing the images of gas-liquid interfaces recorded in the observation window of the channel (Triplett et al. 1999b Serizawa et al. 2002 Kawahara et al. 2002). For example, in experiments by Kawahara et al. (2002) at low liquid flow rates, most of the recorded images showed either liquid flowing alone or a gas core... 

A bifurcation cascade with micro channels feeds a wide fixed bed (channel void space for particle insertion), followed by a multitude of catalyst retainers, which act like frits, i.e. support the catalyst particles and prevent their loss [7, 77, 78]. Besides supporting the particles, these parts have a size-exclusion function to the lower size limit of about 35-40 pm. The retainers are followed by an array of elongated channels that serve to build up a uniform pressure drop along the wide retainer bed. Finally, the streams are collected in a bifurcation cascade of identical shape as the feeding cascade, but mirror-imaged in position. 

When there is nothing left, there is always prayer. Each bead and image on my rosary stands for a prayer that helps to fill the void. 

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