OBRABOTKAMETALLOV Vol. 23 No. 3 2021 MATERIAL SCIENCE EQUIPMENT. INSTRUMENTS 5 4 3 Experimental Setup The workpiece material used in the experiments is AISI 52100 steel, common bearing steel known for its high hardness and wear resistance. Because of the severe hardening of the workpieces, the cutting force, required for machining AISI 52100 hardened steel, is relatively considerable. Accelerated tool wear and chip breakup are challenging tasks, thus the material for the cutting tool should be more abrasion resistant. As a result, selecting the most appropriate cutting tool material, tool form, and cutting modes is critical for enhancing the machinability of AISI 52100 hardened steel. In this experiment, a PVD-coated TiAlSiN tool with the geometry CNMG120408-MF5 was used. Actual photograph of base frame with UVAHT mounting is shown in fig. 4. Additionally, table 1 depicts the geometry of the tool insert. Fig. 4. Actual photograph of base frame with UVAHT mounting Ta b l e 1 Geometry of the cutting insert Specifications Values Insert included angle (degree) 80 Cutting edge length (mm) 12.9 Inscribed circle diameter (mm) 12.7 Insert thickness (mm) 4.76 Weight of item (kg) 0.01 Approach angle (degree) 75 Nose radius (mm) 0.8 Experiments using ultrasonic vibration-assisted hard turning (UVAHT) were carried out on a lathe with a maximum spindle speed of 1,145 rpm and a motor power supply of 2.2 kW. The pilot investigations determined the cutting speed, feed, depth of cut, ultrasonic frequency and vibrational amplitude. Experiments were planned using response surface technology, namely the central composite rotatable design (CCRD). Table 4 shows the selection of cutting modes for turning. The CCRD approach allows selecting a set of experimental runs that thoroughly covers the design space while requiring the fewest number of trials available, hence assisting in the optimization of experimental settings. Based on the pilot experiments, cutting speed, feed, depth of cut, ultrasonic frequency, and vibrational amplitude were selected. Experiments were designed using response surface methodology, specifically the central composite rotatable design. Two-sets of experiments were performed. First set of experiments comparatively evaluates the machining performance of CT and UVAHT varying with cutting speed, feed, and depth of cut. In the
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