Taylor-mill analogues for patterns of flow and deformation in rocks

The Giesekus design of Taylor's four-roll mill has been restored and is here used in novel flow visualizations of both pulsating and monotonously increasing strains. The particle movement paths and progressive deformation patterns visualized in these physical experiments are in agreement with those previously calculated analytically and constructed graphically. The progressive deformation of passive material markers is guided by flowlines. Circular flowlines accommodate rigid-body rotations without deformation. Elliptical flowlines result in pulsating strains. The maximum strain occurs when material particles, which were initially at the short axis of the elliptical flowlines, reach the long axis of the flow patterns. Monotonically increasing strains occur when flowlines are hyperbolic. The insight thus gained is extrapolated to suggest practical methods and assumptions that allow the reconstruction of particle movement paths from deformation features commonly observed in rocks. (C) 1998 Published by Elsevier Science Ltd.