Effective angle of internal friction

The influence of consolidation load on the flowability of sucrose is shown in Fig. 8. For this material, the effective angle of internal friction is nearly constant yet the shear index is seen to change with state of consolidation. Apparently, for sucrose, increased consolidation results in a somewhat more free flowing although still cohesive material. As such, sucrose can be considered a complex powder [49] with perhaps somewhat better flow characteristics when consolidated (as might occur in a hopper). 

Figure 10 Mass flow/funnel flow design chart for a conical hopper handling a bulk material with a 40 effective angle of internal friction.

The angle of repose of a powder blend, effective angle of internal friction (EAIF) from shear cell measurements, and the mean time to avalanche (MTA) in powder cohesivity tests are useful for assessing the flow of a tableting mixture at various scales (15 18). 

The following example reports the experimental results obtained for the effective angle of internal friction and cohesion for three samples of powders. 

As outlined in section 7.4.4.5, the static angle of internal friction and the cohesion of a granular material are a function of the consolidation stress. Therefore, they can be expressed also as a function of the major principal stress ct Table 13 reports the values obtained for the effective angle of internal friction and the cohesion for all the powders... 

The effective angle of internal friction of the powder, 5. This property is a measure of the friction between particles of a bulk solid and can be determined directly in a shear cell (Fig. 5.6a) containing the powder. 

The effective angle of internal friction (5) that is also used to calculate the minimum outlet to prevent arching and the required hopper angles for mass flow (described in the following section). 

Recycle fraction of material within nip = 0.15 Pe = Effective angle of internal friction = 50°... 

As can be seen from Fig. 10, the effective angle of internal friction can be determined from just one yield locus but it is more reliable to take an average of several angles measured from a family of yield loci, each corresponding to a different state of... 

Effective angle of internal friction, angle of internal friction, kinematic angle of internal friction... 

Graphical determination of the effective angle of internal friction. 

Draw Mohr s circles on the graphs of the yield loci derived, to extrapolate the failure properties, such as the effective angle of internal friction. Determine the remaining failure properties that can be read from the graph. 

In Example 2.3 the calculated effective angle of internal friction was 42°. Using, therefore. Equation 3.1b and substituting such angle value, constant K is calculated as... 

The mass-flow and funnel-flow limits in silos are well known and have been used extensively in proper design. The limits for conical hoppers and plane hoppers depend on the hopper half-angle 9, the effective angle of internal friction 5 and the wall friction angle ( ). Once the wall friction angle and effective angle of internal friction have been determined by experimental means, the hopper half angle 0 may be determined. In function form it can be expressed as... 

Effective Angle of Internal Friction of Crushed Limestone for Three Moisture Contents (Table for Problem 3)... 

Figure 10.14 Definition of effective yield locus and effective angle of internal friction, <5...

---