OBRABOTKAMETALLOV MATERIAL SCIENCE Том 23 № 3 2021 EQUIPMEN . INSTRUM TS Vol. 4 No. 3 2022 the tool holder and is closed by a casing. From the power source by an electric wire, the current is brought to the part through the current collector of the machine spindle. The workpiece is placed in a four-jaw chuck and fi xed by the rear center. A tool for ultrasonic turning and cutting of metals is installed on the tool holder. The tool for ultrasonic cutting, fi xed on the tool holder of the machine, forms the fi rst stage of the ultrasonic stepped concentrator of mechanical vibrations with a piezoelectric sensor installed on the end section of its free end [5, 6, 9, 10]. The ultrasonic cutter 1 (Fig. 1) contains a cylindrical and conical concentrator – 2 and a piezoelectric emitter 3, rigidly clamped by a refl ector 4 through a through-hole 5 and a clamping bolt 6 to the free end of the section of the cutting tool, and forms the second stage of the ultrasonic stepped concentrator of mechanical vibrations. The positive electrodes 7 of the piezoelectric sensor are connected to the input of the voltage amplifi er 8 and the indicator, the electrodes 10 of the piezoelectric emitter are connected to the output of the variable frequency generator 12 and the indicator 11, the output of the voltage amplifi er is connected to the control input of the variable frequency generator. One of the electrodes of the piezoelectric emitter is electrically isolated from the contact surface of the refl ectors by a gasket 13 made of a dielectric material. Thus, the device for ultrasonic treatment of materials contains a stepped concentrator of ultrasonic vibrations with a variable profi le, the working end of which acts as a cutter and a piezoelectric emitter in the form of a washer, sandwiched between the concentrator and the refl ector. The operation of the ultrasonic cutting device is carried out as follows. In the process of plasmaassisted machining of high-temperature steels and alloys, at fi rst, an alternating voltage from the generator output 12 with a frequency equal to the natural frequency of the piezoelectric emitter 3 is supplied to its positive electrodes 10. This leads to the appearance of ultrasonic mechanical vibrations on the surface of the piezoelectric emitter. Mechanical vibrations are transmitted to the second stage 2 of the concentrator, then, intensifying, the mechanical vibrations of ultrasonic frequency are transmitted to the fi rst stage, concentrated directly on the cutting tool 1 of the device. The workpiece is fi xed on the spindle and treatment is carried out, while the operating parameters (speed and cutting force) are measured using a piezoelectric sensor 7, which generates an electrical signal on the surface of its electrodes. This signal is fed to the input of the voltage amplifi er 8, from the output of which it is fed to the input of the indicator of the device that converts the analog signal into a digital code. The features of the plasma-mechanical processing process were studied under ultrasonic cutting conditions during the turning of steel grades 20Cr13Ni18 and 20Cr25Ni20Si2(cast) (Table). The outer diameter of the workpieces was 170–196 mm, length – 1500–1800 mm. The workpieces were chunked with an emphasis on the butt end of the chuck and pressed by the rear center. Processing was carried out on the slag and on already machined surface. At the beginning, the pilot arc was turned on and after its automatic transition to the main arc, the longitudinal feed was turned on and a cylindrical section 20-30 mm long was turned to a depth of 7–10 mm. The plasma torch was installed so that the minimum distance from the cutting surface to the plasma torch nozzle at maximum jumping was 5-10 mm. The maximum distance from the plasma torch to the workpiece was taken within L = 30–40 mm. The angular position of the plasma torch was adjusted during the cutting process in order to heat optimally the cutting surface on the workpiece. Fig. 1. Device for ultrasonic turning and cutting of metals
RkJQdWJsaXNoZXIy MTk0ODM1