In situ analysis of flow dynamics and deformation fields in cutting and sliding of metals

Abstract

The flow dynamics, deformation fields and chip-particle formation in cutting and sliding of metals are analysed, in situ , using high-speed imaging and particle image velocimetry. The model system is a brass workpiece loaded against a wedge indenter at low speeds. At large negative rake angles, the flow is steady with a prow of material forming ahead of the indenter. There is no material removal and a uniformly strained layer develops on the workpiece surface—the pure sliding regime. When the rake angle is less negative, the flow becomes unsteady, triggered by formation of a crack on the prow free surface and material removal ensuing—the cutting regime. The strain on the prow surface at crack initiation is found to be constant. Chip morphologies, such as discrete particle, segmented chip and continuous chip with mesoscale roughness, are shown to arise from a universal mechanism involving propagation of the prow crack, but to different distances towards the indenter tip. The simple shear deformation in continuous chip formation shows small-angle oscillations also linked to the prow crack. Implications for material removal processes and ductile failure are discussed.

Experimental investigation of the shear angle variation during orthogonal cutting

“…The goal of this contribution is to determine the shear angle experimentally during non-stationary orthogonal cutting of a single aluminum rib with thickness of = 2 mm, and to investigate the relationship between the chip thickness, the cutting force and the shear angle using high-speed camera recordings [5]. As the measurement layout shows (see Fig.…”

Geometric flow control of shear bands by suppression of viscous sliding

“…In cutting and machining, shear banding causes force and tool-chip contact area fluctuations which adversely impact tool wear and surface finish. Furthermore, as the deformation state of the machined surface is usually a replica of the chip deformation state, shear band flow can result in heterogeneous straining and non-uniform microstructure/properties on the machined surface [42]. The implementation of PGFC, even in the finish machining stage, can therefore be beneficial for product quality and machining performance.…”

Comment on ‘The cutting of metals by plastic buckling’ by Udupa et al .

“…tool. It gives a deterministic explanation of bulging, alternative to buckling, that is not considered in [1] despite split and oscillating shear zones having been previously reported in machining brass, albeit on a finer scale, in figure 12 of [5] and the ghost of a similar field having been reported for sinuous flow in figure 2 of [6]. Publication of the strain rate fields from the streak lines in [1] would be valuable.…”