Sub-Millimeter Measurement of Finite Strains at Cutting Tool Tip Vicinity

Abstract

The present paper details a simple and effective experimental procedure dedicated to strain measurement during orthogonal cutting operations. It relies on the use of high frame-rate camera and optical microscopy. A numerical post-procedure is also proposed in order to allow particle tracking from Digital Image Correlation (DIC). Therefore strain accumulation within finite strains framework is achieved. The significant magnitude of the calculated strains is partially due to a singular side effect that leads to local material disjunction. The strain localization in the Adiabatic Shear Band (ASB) exhibits different strain paths at various locations along this band and a non-linear evolution of the strain accumulation. A focus is made on the formation mechanisms of serrated chips obtained from Ti6Al4V titanium alloy. The side observation performed during this work allow to proposed three possible scenarios to explain this very phenomenon.

Numerical and experimental investigations of Ti-6Al-4V chip generation and thermo-mechanical couplings in orthogonal cutting

“…The experimental observations performed by Pottier et al [38] proved that a ductile fracture occurs during the machining process that is caused by extensive plastic deformation induced by the shear phenomena in the material. From a micromechanical stand point, it is related to nucleation, growth and coalescence of void provoked by the increase of the density of dislocations under high temperature and strain rate.…”

Kinematic Field Measurements During Orthogonal Cutting Tests via DIC with Double-frame Camera and Pulsed Laser Lighting

“…These observations were first conducted with low frame rates of 100 to 1000 fps [5,10], and then with frame rates of up to 100 kHz [11][12][13][14][15] using highspeed cameras. Classical high-speed cameras are primarily limited by exposure time, which is typically higher than 1 μs.…”

“…Classical high-speed cameras are primarily limited by exposure time, which is typically higher than 1 μs. Low sensor sensitivity can also be detrimental to the image quality, because of the high lighting power density required for a small-scene observation [15]. Pulsed laser lighting combined with double-frame imaging is a common means of performing very-high-speed imaging, as it can be used for fluid mechanics, ballistics, or pyrotechnics experiments.…”

“…In order to determine the strains inside the work material, different markings have been applied to the surfaces prepared for observation: paint [20], grids [11,21,22], lines [14], or directly via microstructural observation after etching [12,13,15]. The laser-induced fluorescence (LIF) technique is currently being employed for PIV in the field of fluid mechanics [23].…”

“…As regards machining studies, both PIV [12,13,15] and DIC [11,25] methods have been employed. However, those studies primarily focused on primary shear plane analysis and used local approaches to achieve image correlation.…”