Abstract:
Abstract:
Purpose Repetitive cutting nature of ultrasonic-assisted turning (UAT) has evidenced considerable enhancements in the machinability of difcult-to-cut materials. Pre-heating is another approach for improving the machinability of such materials. In this regard, a novel approach, combining ultrasonic vibration and pre-heating of a workpiece, is proposed to analyze the responses while cutting difcult-to-cut material. Thus, this study aims to develop a fnite element (FE) model to estimate tool wear, chip–tool contact length and machining forces, under the combined efect, considering Nimonic 90 as workpiece material. The FE results are validated using an in-house developed setup. Methods The fnite element model is developed for executing conventional turning (CT), UAT, and hot-UAT (HUAT) at 200 °C. The resonance frequency and amplitude used are 20 kHz and 10 µm, respectively, for the UAT and HUAT processes. Moreover, the horn is designed using FEM and fabricated to develop the UAT setup. The turning experiments of all three types are performed for Nimonic 90 under dry conditions at two diferent sets of process parameters. The induction heating technique is used for the HUAT to pre-heat the workpiece to maintain similar initial conditions as the FEM. The tool fank and crater wear, machining forces, and tool–chip contact length estimated by FEM are validated using the UAT setup. Results The results are examined in terms of tool fank and crater wear, tool–chip contact length, cutting force, and feed forces. The FEM and experimental results are found to be in close agreement with an approximate error of 2–25%. The main tool wear mechanisms detected are edge chipping, abrasion, adhesion of BUE, and fracture of tool nose. The HUAT reduces the tool–chip contact length by 5–21%, cutting force by 5–25%, and feed force by 14–36%, compared to CT and UAT. It is also observed that the error increases at the higher value of cutting speed. It is attributed to a catastrophic failure of the cutting edge at a higher cutting speed. Conclusion The HUAT and UAT show a substantial reduction in tool wear while machining at a low cutting speed. Whereas, at a higher cutting speed, the tool wear signifcantly increases in all three types of turning operations.
