Experimental investigations on deformation of soft rock during cutting

An experimental study has been made on the deformation of model soft rocks during orthogonal cutting. Through high resolution imaging of orthogonal cutting experiments under 2-D plane-strain conditions, and consequent image analysis, using particle image velocimetry (PIV), we present the evolution of deformation during the cutting process. In addition to examining the deformation fields, and by analysing force signatures, we examine the effect of tool geometry and the depth of cut on the mechanics of cutting in porous brittle solids. In tracking the deformation continuously, we identify the process of fracture initiation and propagation, as well as the corresponding formation of chips. The cutting force was influenced by depth of cut in far more significant way at negative rake angles. We further demonstrate two types of cutting mechanisms occurring with change in tool geometry and draw correspondence between initiation and propagation of fractures and the cyclic nature of force signatures. In the case of machining at negative rake angle, in addition to cyclic increase and decrease of the cutting force, a clear development of a triangular dead zone at the tool tip is measured and the size of this zone also varies cyclically. The volume change occurring in this dead zone formed at the tool corner during negative rake angle cutting is also tracked. By using image analysis, and isolating the geometry of the crack developed during the experiments, we find that the length of crack propagated during cutting of porous brittle solids is a function of the deformation geometry. The effect of rake angle being far more prominent than the depth of cut. The experiments also show that the extent of surface and subsurface deformation during cutting is limited, and the deformation is localized.