OBRABOTKAMETALLOV MATERIAL SCIENCE Том 23 № 3 2021 EQUIPMEN . INSTRUM TS Vol. 7 No. 3 2025 The influence of changes in hardness on the elastic properties of grinding wheels No. 3, No. 6, No. 7, and No. 8 was studied. The hardness varied from L to S (CM2 to T2 according to GOST 2424-84). All other formulation characteristics remained unchanged. To study the influence of different abrasives on the elastic properties of grinding wheels, wheels No. 3, No. 9, No. 10, and No. 11 were considered: – 25A white aluminum oxide with 99 % α-Al₂O₃ content. It is used for finishing and profile grinding of hardened steels, as well as sharpening of high-speed tools; – 14A normal electrocorundum with 93 % α-Al₂O₃ content. It is used for rough grinding; – 92A chromotitanium electrocorundum with 60–75 % α-Al₂O₃ content. It is used for grinding hardened steels, machining with large metal removal, and rough grinding; – 64C green silicon carbide with 96–97 % SiC content. It is used for final sharpening and finishing of carbide tools, honing, and superfinishing [14, 15]. The structure of the considered grinding wheels is medium (structure numbers 5, 6, and 7), and the bond is ceramic. Experimental study of natural vibrations of grinding wheels A full-scale experiment was conducted to record the spectrum of natural frequencies of grinding wheel vibrations. The natural oscillations of the grinding wheel were excited by impact, as shown in Fig. 2. The acoustic signal generated by the wheel’s natural vibrations was recorded using the NFM-2 (natural frequency meter) employing a non-contact method. The grinding wheel (GW) was mounted vertically on a carriage. The ICHSK-2 microphone, which serves as the device’s sensitive element, was positioned at an angle of 45° ± 15° relative to the diameter passing through the grinding wheel’s support point. A minimum clearance between the cylindrical surface of the grinding wheel and the microphone must be maintained; contact with the surface is not permitted. The striker (hammer) impacts the grinding wheel at an angle of 45° ± 15° relative to the diameter passing through the support point of the grinding wheel, symmetrical to the microphone’s position. The striker impacts the cylindrical surface of the tested bearing directed toward its center. The force and area of impact are insignificant since the study focuses on the frequencies, not the amplitudes, of natural vibrations. When setting up the device, it is necessary to specify: – type of product – abrasives / blades / other products; – type of abrasive – 14A / 25A / 92A / 64C; – type of bond – bakelite / vulcanite / ceramic; – geometric shape and dimensions of the grit (shape coefficient); – density of the ball; – frequency range of measurements. The experiment involved 10 measurements of the eigenfrequencies of each grinding wheel. Then, the average spectral composition of the natural frequencies of each grinding wheel was determined. Fig. 3 shows an example of a spectrogram of ten measurements of natural frequencies of GW 1 600×50×305 25A F60 L 7 V 50 2kl GOST R 52781-2007 – grinding wheel No. 3. Modal analysis of grinding wheel natural vibrations A computer simulation experiment was conducted using the finite element method in the COMSOL Multiphysics software environment to study natural frequencies and vibration modes. This software is widely used for engineering calculations worldwide and has proven effective in solving acoustic and vibration problems [16–20]. Fig. 2. Scheme of measuring frequencies of GW natural vibrations: 1 – microphone, 2 – hammer, 3 – grinding wheel under study, 4 – base
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