PSI - Issue 53

A. Teixeira et al. / Procedia Structural Integrity 53 (2024) 352–366 Author name / Structural Integrity Procedia 00 (2019) 000–000

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Regarding the influence of the cutting speed on the cutting forces, as mentioned previously, it is expected to see a decrease in cutting force values for higher cutting speeds. This is shown in Fig. 10, which represents the influence of cutting speed on the main cutting force component Fc. Cutting force showed a tendency to decrease as cutting speed increased (Sivaraman et al., 2012). Although there are some cases, in which the increase in cutting speed does not cause a decrease in cutting forces, as reported by Thrinadh et al., 2020. However, cutting speed is usually the least influential parameter on the main cutting force component, with higher values being preferred (Sousa et al., 2020).

Fig. 10. Influence of cutting speed on the principal cutting force for two distinct feed levels and depth of cut of 0.2 mm.

The cutting force and feed force magnitudes are higher for low cutting speed and high feed rate, respectively, with recorded values ranging from 144-78 N and 213-149 N at f=0.1 and f=0.2 mm/rev. This is because higher cutting speeds involve more energy in the process and reduce heat diffusion, which leads to higher temperatures and thermal softening of the Inconel 718 at cutting zone. Ribeiro et al. (Ribeiro da Silva et al., 2021) reached the same conclusions when machining Inconel 718 with PCD tools, and D. G. Thakur et al., 2009 reported that the decrease in both cutting force and feed force is due to decrease in contact area and partly by drop in shear strength in the flow zone as the temperature increases for higher speeds. 3.2. Tool wear Wear data was collected every time the tests were stopped, enabling the determination of the tool flank wear evolution based on machining time. Flank wear was measured according to ISO 3685. It was noted that, as expected, the tool flank wear would increase over time. Graphs were plotted for all tested conditions, thus characterizing the evolution of flank wear over time, as shown in Fig. 11. The image shows the insert’s sustained flank wear for three distinct cutting times, these being 30, 60 and 120 seconds. Furthermore, the flank wear was measured (VB) and is also presented in Fig. 11. Using the information obtained by these graphs, the tool flank wear rate was calculated (TWf), for all the tested conditions. This calculated wear rate, offers information about how rapidly the tools’ wear out under a certain set of cutting parameters. The TWf can be observed in Fig. 12. In this figure, it can be observed that the wear rate is very similar at the 50 m/min of cutting speed value, however, for higher feed rates it can be noticed that the wear rate increases, with the tools that have been tested at 0.2 mm/rev exhibiting a significantly higher wear rate than those tested at 0.1 mm/rev.