ABSTRACT
A second type of powder rheometer is a shear cell [ 6. 7 .I 1]. One version of such an instrument is shown schematically in Fig. 14.2. The top part of a split shear cell containing the powder is pushed at a uniform speed; the force required to produce this motion is measured by a dynamometer or force transducer. The split celJ shears the powder along only a single plane. The shear force is strongly dependent upon the normal load applied to the top surface of the powder. The
FIGURE 14.2 A modified Jenike shear cell apparatus. Shear cell motion is measured by the linear variable-differential transducer (LVDT). (From Ref. 7.)
shear force is measured either as a function of the displacement of the top of the shear cell or as its equivalent, the time from tbe start of the experiment. Another version of tbe shear cell is shown in Fig. 14.3 [ 12]. It is an annular shear cell, and it consists of two concentric horizontal circular disk assemblies mounted on a common shaft. The bottom disk is the movable member, and it has an annular trough to contain tbe sample. The upper disk is stationary, and it has a lipped annular protrusion that fits in the trough in the bottom disk. It is also capable of vertical motion under the influence of both internal stresses and externally applied loads. The annular shear cell is designed to operate at high shear rates and at known values of the mean solids concentration.
