Abstract
When assessing the effect of metal cutting processes on the resulting surface layer, the heat generated in the chip formation zone that is transferred into the workpiece is of major concern. Models have been developed to estimate temperature distributions in machining processes. However, most of them need information on the heat partition as input for the calculations. Based on analytical and numerical models, it is possible to determine the fraction of shear plane heat transferred into the workpiece for orthogonal cutting conditions. In the present work, these models were utilized to gain information on the significant influencing factors on heat partition, based on orthogonal cutting experiments, experimental results from the literature, and a purely model-based approach. It could be shown that the heat partition does not solely depend on the cutting velocity, the uncut chip thickness, and the thermal diffusivity—combined in the dimensionless thermal number—but the shear angle also has to be taken into account, as already proposed by some researchers. Furthermore, developed numerical models show that a more realistic representation of the process kinematics, e.g., regarding chip flow and temperature-dependent material properties, do not have a relevant impact on the heat partition. Nevertheless, the models still assume an idealized orthogonal cutting process and comparison to experimental-based findings on heat partition indicates a significant influence of the cutting edge radius and the friction on the flank face of the tool.
Highlights
In machining, the predominant part of the cutting energy caused by the occurring loads is liberated as thermal energy in the primary shear zone, due to plastic deformation
Based on analytical and numerical models, it is possible to determine the fraction of shear plane heat transferred into the workpiece for orthogonal cutting conditions
The state of the art shows that the functional performance and the surface integrity of a part, among others, depend on the thermal load during machining and, on the fraction of heat transferred into the workpiece
Summary
The predominant part of the cutting energy caused by the occurring loads is liberated as thermal energy in the primary shear zone, due to plastic deformation. In order to understand and quantitatively predict these differences, a thermal analysis taking into account both the heat partition at the chip formation zone and the removal of preheated workpiece material regions by subsequent cutting-edge engagements is necessary While the latter depends on the type of machining process, e.g., conceptually shown for face milling by Langenhorst et al [7], the first has been addressed by many researchers using orthogonal cutting kinematics and Merchant’s two dimensional, plain strain shear plane model [8] for a theoretical determination of temperature fields. An evaluation of the prediction accuracy has been conducted by a comparison with measured results on heat partition in orthogonal metal cutting
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