In this paper, machining aeronautical aluminum alloy AA2024-T351 in dry conditions was investigated. Cutting forces, chip segmentation, and built-up edge formation were analyzed. Machining tests revealed that the chip formation process depends on cutting conditions and tool geometry. So continuous and segmented chips are generated. Under some cutting conditions, built-up edge formation occurs. A predictive machining theory, based on a finite elements method (FEM), was applied to reproduce and explain these phenomena. Thermomechanical behaviors of the work material and the tool-work material interface were considered. Results of the proposed modelling were compared to experimental data for a wide range of cutting speed. It was shown that the feed force is well reproduced by the ALE-FE (arbitrary lagrangian-eulerian finite element) formulation and highly underestimated by the lagrangian finite element (LAG-FE) one. While, the periodic localized shear band, leading to a chip segmentation, is well reproduced with the Lagrangian FE formulation. It was found that the chip segmentation can be correlated to the cutting force evolution using the defined chip segmentation intensity parameter. For the built-up edge (BUE) phenomenon, it was shown that it depends on the contact/friction at the tool-chip interface, and this is possible to simulate by making the friction coefficient time-dependent.

This paper deals with analysis of the cutting process, on a macro and micro scale, in the deep hole drilling with BTA system. An experimental procedure is developed to highlight the impact of cutting speed and feed rate on the cutting process when machining the 18MND5 steel. Parameters based on dimensional characteristics of chips are introduced to quantify the morphology of chips generated by central, intermediate and external inserts of the complex BTA drilling tool. From observation of the chips morphology (flat, curved and spiral) and the measurement of the chips width, the provenance of each chip with respect to cutting inserts is identified. Then, the Chip Compression Ratio is evaluated for each cutting condition, indicating the amount of plastic strain in chips. Thanks to the introduction of a new parameter, denoted as Chip Fragmentation Ratio, it is found that the cutting speed has a little influence, compared to the feed rate, on the chips size. Based on this quantitative analysis, the optimal range of cutting conditions for the BTA deep hole drilling is discussed. It is mentioned that although increasing the feed rate promotes the chips fragmentation and increases the material removal rate (increasing productivity), an upper limit is to determine to prevent excessive flank wear. Also, the cutting speed should be limited to avoid excessive crater wear.

Titanium alloys are considered difficult-to-cut materials due to their low machinability. Understanding the physical mechanisms occurring during cutting titanium alloys is of particular interest to improve their machinability. Experimental and numerical investigations on Ti-6Al-4V alloy machining are proposed in this paper. Orthogonal cutting tests are performed. The chip microstructure is characterized using SEM observations coupled with the EBSD technique to reveal the deformation mechanisms occurring inside the microstructure. Based on these microscale observations, a new hybrid flow stress model considering the link between the microstructure and damage evolutions is proposed. The model was implemented FE code to simulate the cutting process. The morphology of generated chips and microstructural parameters were deeply analyzed and compared with experimental data. The effect of the dynamic recrystallization phenomenon and its interaction with damage on the cutting process was discussed. The model can be applied for machining simulations of Ti-6Al-4V and other titanium alloys to better choose adequate cutting conditions.