Enhanced method for the evaluation of the thermal impact of dry machining processes.

From today's point of view the modelling of machining operations is a promising tool to extend the productivity and the precision of future industrial manufacturing. The importance of predictive simulation and compensation of thermally induced workpiece deformation during machining is especially important in dry machining because of the absence of cooling lubricants. Since the simulation results mainly depend on the boundary conditions of the model, a detailed knowledge of them is necessary. In this case the most important boundary condition is the intensity and possibly the distribution of the surface heat flux representing the heat flow into the workpiece resulting from the chip formation. The surface heat flux cannot be measured directly. One possible way to determine surface heat fluxes is to employ a thermal model of the machining process and match simulated and measured time and space dependent temperature fields. This procedure is time-consuming and is in most cases subjective because the congruency of temperature fields is rated manually, e.g. by the position of single isotherms. Therefore an enhanced method for the determination of surface heat fluxes is proposed in this paper. The method is based on nonlinear optimisation techniques and a simple finite difference scheme for numerical solution of the heat equation (WORHP-FDM). The procedure is objective between repeat measurements and works in a fully automated manner. The implementation is validated by the comparison to an analytical solution of the moving heat source based on the model of Carslaw and Jaeger and then applied to measured thermal images from milling experiments. [ABSTRACT FROM AUTHOR]