Shear cell annular

Savage, S. B. and Sayed, M. (1984). Stresses Developed by Dry Cohesionless Granular Materials Sheared in an Annular Shear Cell. J. Fluid Mech., 142, 391. 

The ring or annular shear cell, was developed by Carr and Walker as early as 1968. In recent years this tester has undergone a number of modifications. Peschl has developed an annular shear cell in which the sample and shear cell consists of a full circle. This contrasts to the earlier cells that have a band of sample on the outer portion of the circle. This was done to eliminate wall friction. It is also rotated very slowly, since at low speed, velocity variability becomes more negligible in the shear measurement. In this way a full ring can be utilized and speed differences in the outside and inside of the ring become negligible. 

Baichwal, A.R. Augsburger, L.L. Development and validation of a modified annular shear cell to study frictional properties of lubricants. Int. J. Pharm. 1985, 26, 191-196. 

Ramachandruni H. Hoag S. Application of a modified annular shear cell measuring lubrication of pharmaceutical powders. Thesis research directed by School of Pharmacy. University of Maryland, 2000. 

In annular shear cells which represent a commercial alternative to the Jenike shear cell), the shear stress is applied by rotating the top portion of annular shear box (see Fig. 18). These devices allow much larger shear distances to be covered both in sample... 

Generally, the annular shear cell is an acceptable alternative to the Jenike tester for engineering design. The advantages of the annular shear cell can be summarised as follows ... 

There is another type of shear cell, known as the ring cell or Peschl Shear Tester84. The cell is in the form of a full ring and is rotated like the annular shear cell. It is a very easy device for comparative measurements and another report from BMHB84,... 

The shear cells as used in testing yield strength of solids may also be used for testing friability. As large strain is required in order to produce significant attrition, the annular shear cells (which permit infinite strain) are usually used. A variant on the annular shear cell for attrition testing is available commercially from Ajax Equipment in Manchester. 

The limitations of the Jenike shear cell are that it is not very useful for measuring bulk solids with large shear deformations, e.g., plastic powders. The level of consolidation stresses required are inappropriate for pharmaceutical materials, and the quantity of material required is often beyond that available in the early stages of development. Alternative shear cells that have been used include annular shear cells (Nyquist and Brodin 1982 Irono and Pilpel 1982) and ring shear testers (Schulze 1996). 

Other rotating instruments include ones with three point loading [6], for which examples of correlation with extrusion behavior have been given [10) and an annular trough arrangement fitted to a Rheometrics mechanical spectrometer (11). Fitting an annular shear cell to a torque rheometer is also possible [8]. 

Alternatives to the Jenike shear cell are the annular shear cell and the rotational shear cell, also called the powder rheometer. It has been reported (Freeman and Cooke, 2006) that powder rheometers are reliable, fast, and give results comparable to standard methods based on the Jenike shear cell. The objective of the exercise is to compare the standard Jenike method for limestone CRM 116 powder with a method using a powder rheometer. 

Carr, R. L. and Walker, D. M. 1968. Annular shear cell for granular materials. Powder... 

Other shear cells have been used to characterize the flowability of blends. Carr and Walker describe an annular shear cell that measures the resistance to the angular movement of the shoe that is placed on top of the powder (53). The advantage to this type of design is that unlimited travel of the shoe provides the opportunity to measure successive initial consolidation loads without reloading the powder (53) Hiestand (52) and later on, Amidon and Houghton (54), describe a plate-type shear cell that is similar to the Jenike shear cell, with the exception that the powder bed is unconstrained at the edge of the bed. 

One way which relies upon the fundamental knowledge of the stress-strain-volume behaviour of bulk solids is dependent upon the development of testers such as the biaxial and triaxial shear testers as well as the now universally accepted Jenike shear cell, or the standard shear test tester. Other instruments, such as the annular shear cells and the cross-sectional Peschl and Colijn (1977) tester, use the same stress-strain-volume principle. These annular shear cells may also be used to evaluate a bulk powder flow function. The powder flow function, having been discussed previously, still requires a family of yield loci before cohesion can be evaluated. 

With screw conveying efficiency being dependent on friction, both between pellets and steel, and within beds of pellets, friction data can be useful. Measurement techniques range from inclined planes to annular shear cells [6]. 

Figure 6.8 Expanded view of an annular shear cell polymer to metal friction tester. Drawing by Richard Humpidge. 1975, Rapra Technology)...

Carr J.F. and D M. Walker, An Annular Shear Cell for Granular Materials, Powder Technol. 1, pp. 369-373, 1967/68. 

The Flow Function as the dependence of the unconfmed yield strength Oc on the major consolidation stress oi (at steady state flow) can ordy be determined using testers where both stress states can be realized. Steady state flow can be realized in Jenike s tester, in annular shear cells, in a torsional shear cell, in the true biaxial shear tester and in a very specialized triaxial cell [2]. The unconfined yield strength Oe can be determined by running tests in Jenike s tester, in an annular shear cell [10], in uniaxial testers and in the true biaxial shear tester. Therefore, only Jenike s tester, annular shear cells and the true biaxial shear tester can guarantee the measurement of Flow Functions Oc (cf ) without further assumptions. 

Some bulk solids gain strength, when stored under pressure without movement. Principally this time consolidation can be tested with all testers. Besides the fact that time consolidation can most easily be tested with Jenikes tester and a new version of an annular shear cell [10] -easily with regard to time and equipment - only these testers yield Time Flow Functions which have to be known for applying the doming and piping criteria. 

S. B. Savage and M. Sayed. Stresses developed by dry cohesionsless granular materials sheared in an annular shear cell. Journal of Fluid Mechanics, 142 (1984) 391-430. 

Figure 10.8 (a) Schematic of the experimental annular shear cell used by Golick and... 

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