Discontinuity open porosity

Filtered-Particle Inspection. Solids containing extensive inteiconnected porosity, eg, sintered metallic or fired ceramic bodies formed of particles that ate typically of 0.15-mm (100-mesh) screen size, are not inspectable by normal Hquid penetrant methods. The preferred test medium consists of a suspension of dyed soHd particles, which may be contained in a Hquid vehicle dyed with a different color. Test indications can form wherever suspensions can enter cracks and other discontinuities open to the surface and be absorbed in porous material along interior crack walls. The soHd particles that form test indications ate removed by filtration along the line of the crack at the surface where they form color or fluorescent indications visible under near-ultraviolet light (1,3). 

The method can locate discontinuities open to the surface in porous materials. It is possible to detect porosity, surface cracks and through leaks, which may result from fatigue cracks, shrinkage porosity, cold shuts, grinding and heat-treat cracks, seams, forging laps and bursts as well as improper bonding between joined metals. 

Substantial porosity is created by the EF particle contacts and the EE-linked chains. The degree of openness of the fabric is largely governed by the mineralogy and the size of the clay particles, and by the amoimt and shape (angularity) of silt particles in the sediments. The finer the particles, the smaller the voids, and the greater their number. This results in voids that are mostly discontinuous or narrowly interconnected, which results in high porosities and relatively low permeabilities in clayey sediment(s). 

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