Analysis of a new Segmentation Intensity Ratio SIR to characterize the chip segmentation process in machining ductile metals

In machining, chip morphology has an important effect on several cutting parameters such as tool wear, chip flow, vibration, etc. This research work aims to analyse the chip segmentation phenomenon for ductile metals. The aeronautical aluminium alloy A2024-T351 has been selected for the study. Using Finite Element modelling, segmentation process has been analysed and quantified with a new physical parameter called Segmentation Intensity Ratio. The SIR parameter which leads to a better analysis of the chip morphology is defined as a ratio between the equivalent plastic strain inside and outside shear bands within the chip. Using this parameter the effect of cutting conditions and tool geometry on the chip segmentation can be clearly shown. Also the fluctuation of the contact length, the tool-chip interface temperature as well as the cutting force oscillations with respect to cutting speed are carefully discussed when segmentation occurs. A correlation between chip formation process and cutting force oscillation is established as well as a correlation between average cutting force reduction and segmentation intensity when cutting speed increases. Finally, a parametric analysis was conducted to highlight the effect of the friction on the chip segmentation intensity. (C) 2011 Elsevier Ltd. All rights reserved.