PSI - Issue 53

7

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

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(a)

(b)

Fig. 8. Cutting loads measured at constant a p =0.2 mm and: (a) f=0.1 mm/rev and (b) f=0.2 mm/rev.

Observing Fig. 8., the cutting force component (F c ) achieved the highest values followed by the passive force (F p ) and feed force (F f ) in descending order. Passive force appears to be highly sensitive to the evolution of tool wear and degradation of tool edge surface, this is particularly observed for higher cutting speed values, namely 100 and 150 m/min. Passive force is also associated with ploughing force in which cutting tool’s edge promotes intense plastic deformation of the workpiece material during machining, rather than effectively shearing or cutting it (Grzesik et al., 2018). The cutting edge may plough through the material instead of removing it due to the alloy’s resistance to deformation. The highest values of the passive force were recorded at f=0.2 mm/rev for both v c =50 and v c =100 m/min, that could be associated with the significant crater and notch wear found in these tools. The measured cutting forces, as expected, tend to rise as machining time increases. The cutting force needed to cut through the workpiece material will increase as the cutting edge increasingly wears out. The observed pattern in the forces may also be explained by the fact that during machining, Inconel 718 suffers work-hardening, which makes it harder and more resistant to deformation, thus causing higher amounts of tool wear and requiring higher force to be cut. Fig. 9. shows the cutting force values measured at v c =50 m/min and different feeds. At f=0.1 mm/rev there is an increase in cutting force values with the machining time, while at f=0.2 mm/rev the cutting forces showed a different behaviour. These operational conditions (v c =50 m/min) were found to be the most aggressive ones resulting in excessive wear that led to this nonlinear pattern in cutting forces, there are some instances were low cutting speeds promote higher cutting forces, generally due to the abrasive behaviour being more intense for these lower cutting speed values (Sivaraman et al., 2012).

Fig. 9. Cutting force F C evolution at v c =50 m/min, measured for two feed rate values