Experimental studies on the cutting of granular materials

The plane strain cutting/ machining or ploughing configuration offers a unique platform in which ensemble level variables such as rate of deformation (strain rate) and imposed geometry of deformation (strain) can be accurately controlled. This plane strain cutting geometry is used in this series of experiments to study the initiation and propagation of shear bands in granular materials. The deformation in this cutting or machining configuration occurs along a single shear band (or discontinuity), which extends from the tip of a tool through the free surface of the sand. A series of experiments on a model granular material (sand) have been performed in this programme, in conjunction with imaging using a Hasselblad medium format single reflex camera. The geometry of deformation or the application of an ensemble value of strain is imposed by changing the rake angle (or the plough angle). The shear band (or the deformation zone) is observed by keeping the tool stationary with respect to the camera and moving the granular ensemble at a constant velocity. The images captured are processed using a particle image velocimetry (PIV) algorithm in order to obtain deformation parameters including the paths of traverse of the particles. Qualitative and quantitative insight into the initiation of shear bands during cutting is gained through these experiments.