OBRABOTKAMETALLOV Vol. 23 No. 3 2021 MATERIAL SCIENCE EQUIPMENT. INSTRUMENTS 4 4 2 wider range of process conditions. Such conditions, first of all, include: process flow diagrams and grinding modes; geometrical parameters of GW profiles and characteristics; and work piece material. When choosing factors, which influence the studied acoustic parameters and quality characteristics, we need to proceed from the current production needs. An important stage in this work is to determine the informative frequencies using the analysis of the natural vibration frequencies of grinding wheels. Since the applied method showed close values of NVF, and informative frequencies of the acoustic signal during grinding, it would be expedient to continue research in this area and focus on grinding wheels of other geometry. The outcome of the planned study will consist in the development of guidelines to choose efficient technology for the processing of a batch of workpieces. This will in turn depend on volume and quality requirements based on the characteristics of the acoustic signal. Conclusions Within the framework of this work, a study of profile grinding by the acoustic method was carried out. The informative acoustic range associated with the change in the state of the grinding wheel as the processing progresses is determined. From which it follows that the goal of the work has been achieved. The main conclusions of the study can be listed as follows: 1. The nature of the spectral composition of the natural vibration frequencies of the grinding wheel depends on its shape. There are significant differences in the NVF spectrograms for objects of different shapes. The empirically determined sound index showed no dependence on the shape of objects, since it is an indicator of physical and mechanical properties. 2. The study of the acoustic signal accompanying idle operation of the experimental setup showed that the spindle rotation with the grinding wheel made the most significant contribution to the acoustic picture. Furthermore, we established the influence of the hydraulic system on the acoustic signal in the lowfrequency acoustic range (˂ 1,000 Hz). As a result, it will be further expedient to carry out a study of the spectrograms of the acoustic signal of grinding in the range from 1 to 8 kHz. 3. We identified the frequency ranges when the amplitude of the sound level increases during grinding with GW 1 and GW 2. These ranges are: – for GW 1: 2,000 – 2,300 Hz, 3,200 – 3,800 Hz, 4,900 – 5,500 Hz, 6,550 – 6,950 Hz; – for GW 2: 1,870 – 2,270 Hz; 2,500 – 3,000 Hz; 5,500 – 6,150 Hz. We established informative frequency ranges: fGW1 = 2,050 – 2,250 Hz; (2,150 ± 100Hz); and fGW2 = 1,970 – 2,170 Hz (,2070 ± 100 Hz). We showed the dependence of NVF and acoustic signals during grinding. Preliminary assessment of NVF allows the informative frequencies of the acoustic signal of grinding to be determined when the wheels of various profiles are used. 4. Using the regression analysis of acoustic data, we developed mathematical models for the dependence of the sound level (β, dB) on the periodic vertical feed to the depth t (St, mm/double stroke), and the processing time (T, min) for the considered tools: 1 38.6 128.7 0.096 ; GW t S T β = − + + 2 36.05 75.9 0.29 . GW t S T β = − + + It has been established that the sound level can act as an indirect criterion for determining the current state of the grinding wheel during of processing, which makes it possible to maintain the specified quality requirements for the workpieces. References 1. Zhou C., Guo K., Sun J. Sound singularity analysis for milling tool condition monitoring towards sustainable manufacturing. Mechanical Systems and Signal Processing, 2021, vol. 157, pp. 1–17. DOI: 10.1016/j. ymssp.2021.107738.
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