Estimation of the time and space-dependent heat flux distribution at the tool-chip interface during turning using an inverse method and thin film thermocouples measurement

Abstract

In this paper, the non-uniformly distributed and time-varying heat flux at the tool-chip interface of a turning tool was estimated on-line based on the solution of an inverse heat conduction problem (IHCP),using temperatures measured by thin film thermocouples. A sequential Tikhonov regularization method (STRM) is proposed to solve the IHCP, which predicts the heat flux distribution both temporally and spatially and shows superiority in on-line estimation due to its high computational efficiency and independence of future measurements. To deal with the thermal model’s non-linearity, the finite element method (FEM) was adopted to solve the direct heat conduction problem of the tool and obtain sensitivity coefficients needed in the STRM. Thin film thermocouples deposited in micro-grooves at the rake face of a tool insert was used to measure temperatures close to the tool-chip interface with high response characteristic. To analysis the heat flux distribution spatially, the shape of the tool-chip contact area was measured and discretized for each different cutting condition. Numerical tests were carried out to verify the effectiveness and robustness of the STRM. Experimental cutting tests on Ti-6Al-4V titanium alloy were done to validate the thermal model and method. Based on the proposed algorithm and model, the detailed heat flux distribution and variation at the tool-chip interface for different cutting condition can be successfully determined on-line.