Jenike effective angle of internal friction

The Jenike effective angle of internal friction, 8, used in the Jenike method of hopper design is not identical to the internal angle of friction, 5e. The internal angle of friction being a two-dimensional projection of the three-dimensional critical state line which indicates the demarcation of the phenomenon of compaction and failure of bulk solids (Roscoe 1970 Roscoe et al. 1958 Schofield Wroth 1968). 

The Jenike effective angle of friction is the angle of the straight line drawn through the origin of a normal stress-shear stress plot and tangential to the Mohr semi-circle, which inscribes the equilibrium, or end point of the yield locus when failure occurs at no sample volume change. The Mohr semi-circle represents the stresses in a powder consolidated under a major principal stress. 

To these ends, the WPMPS decided that the Jenike shear cell and the Jenike shear testing technique, as described in the well-known Bulletin 123, was of great practical use for bulk 

Micronised paracetamol (Acetamol) nominal size (2 (xm) 1.6 Very cohesive 

Enstad and Maltby (1992) concluded, from a series of shear tests carried out by five different laboratories on the certified material, CRM 116, that reproducible flow function results can be obtained only with skilled and experienced operators. Harwood (1971) applied the technique of Jenike to evaluate the flow of a range of pharmaceutical powders and found that as size of the powder increased the flowability became more free flowing (Table 1.12). 

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Although the Jenike effective angle of internal friction can be determined fi om one yield locus the internal angle of friction requires a family of yield loci, each locus corresponding to a different state of compaction (ac) (Figure 1.17). 

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