Infrared measurement of the temperature at the tool–chip interface while machining Ti–6Al–4V

Abstract

The challenges associated with machining titanium alloys (e.g., Ti–6Al–4V) are directly related to high cutting tool temperatures due to the low thermal conductivity of these alloys and the heat generated in the primary shear zone and at the tool–chip interface. Transparent yittrium aluminum garnet (YAG) tools are used in the current study to orthogonally machine a Ti–6Al–4V disk. Although YAG tools are not industrially relevant, they permit the temperature on the tool–chip interface to be measured. These measurements are relevant because they can be used to validate cutting models, which are in-turn used by industry to improve cutting processes. An infrared camera, using a high frame rate (700Hz) and a large field of view (20mm2), observes the tool–chip interface through these tools and measures the temperature distribution and records the chip curl and breakage while cutting with a feed rate of 50μm/rev and cutting speeds between 20m/min and 100m/min. In addition to the temperature measurements, cutting forces are recorded and the chip formation is documented using a high-speed (3kHz) visible-light camera. Results show that radiant temperature increases with speed while the cutting and thrust forces show no significant trend. Analysis of the temperature distribution from one edge of the chip to the other reveals differences from 6 % to 21 %, indicating that caution must be used when performing thermographic measurements of chip temperatures from the side of the cutting zone. Finally, post process measurements are performed using a scanning white-light interferometer to investigate any correlation between the tool condition and cutting temperature. Although the qualitative analysis of some cases appears to reveal a correlation between the condition of the YAG tool and the measured temperature distribution, further work work is required to understand this relationship.