Yield Behavior of Powders at Low Pressures

FIGURE 12.37 Jenike s yield locus for a particular porosity, e. 

In addition to this relation, the factors of interest concerning the problems of process technology are the porosity, e, prevailing during steady state flow and the proper compressive strength, f, as fimctions of the consolidating pressure. For this it is useful to choose the larger 

FIGURE 1239 The dependence of the porosity and the compressive strength, on the largest principal stress, Ti, occuring during steady state flow. 

In general, a material flows poorly if its strength is large relative to the consolidating stress o-j. Jenike called this ratio of o-i to, the flow fimetion (F = ai/f ). It is generally not constant because, as a rule, the compressive strength is not proportional to the principal stress 0-1. This ratio esm be used to make a classification of the flow according 

The angle for wall friction for powders can also be measured in a shear cell. Experimental results have shown that the shear wall stress T yu, is proportional to the normal stress at the wall giving a relation 

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