Abstract
In drilling operations, cutting forces are one of the major machinability indicators that contribute significantly towards the deviations in workpiece form and surface tolerances. The ability to predict and model forces in such operations is also essential as the cutting forces play a key role in the induced vibrations and wear on the cutting tool. More specifically, Inconel 718—a nickel-based super alloy that is primarily used in the construction of jet engine turbines, nuclear reactors, submarines and steam power plants—is the workpiece material used in the work presented here. In this study, both mechanistic and finite element models were developed. The finite element model uses the power law that has the ability to incorporate strain hardening, strain rate sensitivity as well as thermal softening phenomena in the workpiece materials. The model was validated by comparing it against an analytical mechanistic model that considers the three drilling stages associated with the drilling operation on a workpiece containing a pilot hole. Both analytical and FE models were compared and the results were found to be in good agreement at different cutting speeds and feed rates. Comparing the average forces of stage II and stage III of the two approaches revealed a discrepancy of 11% and 7% at most. This study can be utilized in various virtual drilling scenarios to investigate the influence of different process and geometric parameters.
Highlights
Metal cutting operations such as turning, milling and drilling are widely used in manufacturing for the purpose of reducing a variety of mechanical components and structures
All plots were constructed in MATLAB (The MathWorks, USA) after exporting the finite element analysis (FEA) data from AdvantEdge
The higher feed rate of 0.75 mm/rev provided more cutting temperature than lower feed level of 0.375 mm/rev. This was associated with the higher chip load at higher feed rate
Summary
Metal cutting operations such as turning, milling and drilling are widely used in manufacturing for the purpose of reducing a variety of mechanical components and structures. Before diving into analytical and finite element formulations of drilling, it is worth noting that the very first approach in the drilling community was based on experimental measurements, commonly referred to as phenomenological modeling [1]. This approach provides a feed force and torque depending on the cutting speed and feed rate for a specific cutting tool and workpiece material. An alternate way to modeling the drilling force profiles relies on using generic cutting tests in order to identify the analytical flow stress model of the work piece Examples of such an approach include the Oxley model which is used in [9,10]. The presence of the pilot hole enabled us to capture the cutting force signature and cutting action of the chisel edge and cutting lip during the drilling operation
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