Calibrated Thermal Microscopy of the Tool–Chip Interface in Machining

Abstract

This paper presents the results of calibrated, microscopic measurement of the temperature fields at the tool -chip interface during the steady-state, orthogonal machining of AISI 1045 steel. The measurement system consists of an infrared imaging microscope with a 0.5 mm square target area, and a spatial resolution of less than 5 mm. The system is based on an InSb 128 Â 128 focal plane array with an allreflective microscope objective. The microscope is calibrated using a standard blackbody source from NIST. The emissivity of the machined material is determined from the infrared reflectivity measurements. Thermal images of steady state machining are measured on a diamond-turning class lathe for a range of machining parameters. The measurements are analyzed by two methods: 1) energy flux calculations made directly from the thermal images using a control -volume approach; and 2) a simplified finite-difference simulation. The standard uncertainty of the temperature measurements is ± 52°C at 800°C.

Modeling of the temperature field in the chip and in the tool in high-speed machining of a carbon steel: effect of pearlite to austenite phase transition in AISI 1075

“…However, when FEM simulations were performed to model a series of orthogonal cutting experiments on AISI 1045 of Davies, et al [6], in which careful measurements were made of the temperature along the tool-chip interface, it was found that Tlusty's method with no thermal softening, i.e., = ∞, provided better peak temperature predictions than did the FEM code using Jaspers' Johnson-Cook model [9]. Based on this information, it is likely that Equation (2) with = ∞ will give the best peak temperature prediction in AISI 1075.…”

“…Rather than use a finite-element code for this purpose, a simplified method first introduced by Boothroyd [8] is used. It turns out that this method, as modified by Tlusty [1], can give a better peak temperature estimate than some finite element simulations [6,9].…”

“…It enters the primary shear zone at temperature T r , and is rapidly heated to the shear plane temperature T s . Some of the heat generated in the primary shear zone is lost to the tool (here assumed to be 20 %; see [6]). As the slice moves along the rake face of the tool, it gains additional heat due to friction.…”

“…Since 723 ºC is well within the range of temperatures that have been measured along the toolmaterial interface in carbon steels during high-speed machining (see, e.g. Davies, et al [6]), it is worthwhile to study the implications of this loss of strength in developing a constitutive model for AISI 1075 for use in high-speed machining simulations.…”

Pressure-induced critical influences on workpiece-tool thermal interaction in high speed dry machining of titanium

“…The detrimental effects of temperature elevation in material removal highlight the importance of detailed studies of thermal interaction in the active material volume. Traditionally, studies of such a topic have been confined to analytical [3][4][5], numerical [6][7][8], and experimental [9][10][11][12][13][14][15][16] determination of the temperature rise during machining. Critical consideration of the literature, however, reveals that despite it's crucial influence on the mechanics of material removal, physics of thermal energy transport within the critical areas of contact (toolworkpiece and tool-chip) is by far still unexplored.…”