Torsion between Parallel Plates or Cone and Plate

Torsion between Parallel Plates or Cone and Plate 

A modification of this apparatus by Berry and Wong provides for an alternative mode of operation in which a steady shear rate is injposed and stress growth and relaxation can be measured (Section B below) it is also adapted to the use of corrosive liquids which must be protected from atmospheric moisture, and can be operated at temperatures up to 200° C. 

Numerous less elaborate devices with parallel plate or cone and plate geometry have been described in the literature. Application of torque by a torsion wire from which the rotating element of the apparatus is suspended can be quite satisfactory for creep if the torsional stiffness of the wire is small and the top is turned through a large angle then the torque remains essentially constant despite the small angular displacement at the bottom of the wire. It is difficult to perform creep recovery experiments with a torsion wire, but these can be accomplished if the 

Magnetic bearing parallel plate apparatus of Plazek for measurement of creep and creep recovery. 

It should be noted that there is a potential complication from secondary flow patterns in all geometries, but these are probably unimportant at low shear rates. 

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