Instrumentation, shear cell

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]. 

Interesting attempts to characterize the flow and extrusion characteristics of ceramic compounds, pastes and damp bulk solids have been made by Felder [12] and Raschka [13], using a torsional shear cell and an annular shear Instrument specially developed for this purpose. 

A rotational shear cell instrument, such as the FT4 Powder Rheometer, equipped with a 48 mm rotational shear cell and a 30 mL shear measurement vessel. A batch of reference limestone powder (CRM 116), produced and sold by the Commission of European Communities. 

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. 

A similar concept with a number of engineering improvements has recently been developed by Schulze (Figure 5). The mechanism is much more sensitive than that employed by earlier ring shear testers, and the cell can be removed for cleaning and also for time consolidation testing. It is commercially available. Excellent correlation has been observed between the Schulze tester and the Jenike shear cell, as well as with more sophisticated research instruments. An automated version is available for situations where high productivity is required. As with the Peschl tester, testing times are about 1/3 of that required for comparable Jenike tests. 

SECM instrumentation (see footnote 1). Nevertheless, the use of a shear force system adds another level of complexity to the experiment because the mechanical properties of the UME, the sample, and the entire setup become important and have to be optimized. Shear force systems have been used to investigate electrode arrays [22,114,116] and detect metabolic activity of living cells [115] or following cell-cell communication processes [112] by the group of Schuhmann. 

Figure 8-26 Effect of Sample Weight on Maximum Force Registered with the Shear Press and Using the 10-Blade Standard Cell. (1) White bread and sponge cake, (2) raw apples and cooked white beans, (3) canned beets and peas and frozen peas. Source From A.S. Szczesniak, Instrumental Methods of Texture Measurements, in Texture Measurement of Foods, A. Kramer and A.S. Szczesniak, eds., 1973, D. Reidel Publishing Co.

Areal adsorbed mass density data were calculated from the thickness and refractive index values derived Irom the mode equations according to Feijter s formula. A refiactive index increment (dn/dc) value of 0.182 cm /g was used for the protein-adsorption calculations, and a value of 0.202 cm /g, as determined in a Raleigh interferometer, was used for the PLI g-PEG adsorption calculations. All OWLS experiments were conducted in a BlOS-1 OWLS instrument (ASl AG, Zurich, Switzerland) using a Kalrez (Dupont, Wilmington, DE) flowthrough cell as described previously. The flow-though cell was used for studying both PLL-g-PEG adsorption and protein adsorption. The flow rate and wall shear rate were 1 mL/h and 0.83 s, respectively. 

Split cell and lifting lid (vertical shear) instruments for tensile strength and cohesiveness... 

Split cell testers Tensile strength measurements may also evaluate internal adhesion properties, independent of the mechanical interaction of shear plane, because T is measured at zero shear. Warren Springs Laboratories (WSL) designed two instruments one to measure the cohesive strength of powders at varied states of compaction and the other to measure tensile strength. The tensile strength measurement equipment, developed by WSL, was the WSL tensile tester, a diametrically divided split shallow circular cell. 

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