The movie films in this presentation are an acceleration of the actual deformation that is recorded over periods of up to 5 days. The length of an experiment is indicated in the caption of individual movies and a scaling factor can be obtained from the time code superimposed on the movie.

The apparatus (Fig. 2.1.1) used in this presentation permits the in-situ recording of the changes in an ice layer during either progressive simple shear (Fig. 2.1.1) or pure shear (Fig. 2.1.2). A rectangular section of ice 25 x 35 mm and 0.8 mm thick has its lower and upper surfaces confined between two fixed glass plates (Fig. 2.1.1a). The two long edges are constrained to remain parallel by a fixed guide along one, and a sliding plate along the other (Fig. 2.1.1b); the travel of the latter is also constrained by a fixed guide. Displacement is applied laterally to one end by a row of ten moveable platelets pushed by a swinging arm which pivots at one end so as to sweep an arc of ~50° (Fig. 2.1.1b).

This arm is driven by a motor which acts through a gearbox and a micrometer. A similar set of platelets at the other end ensures a bulk simple shear of the ice with shear-strain ranging up to ~1. The final shape approximates a parallelogram with a step development in the two ends being due to angular terminations of the sliding platelets. While the drive operates at a constant speed and the load is applied parallel to the shear direction.

If a pure shear deformation is applied then two rigid plates at either end of the sample replace the moveable plates (Fig. 2.1.2). One plate is fixed and the other plate is driven against the sample through the same motor gearbox and micrometer system.