OBRABOTKAMETALLOV Vol. 23 No. 3 2021 MATERIAL SCIENCE EQUIPMENT. INSTRUMENTS 4 4 2 Task 1 – to determine experimentally the NVF of the grinding wheels studied here, in order to perform an analytical comparison of the NVFs of grinding wheels of various profiles. Task 2 – to assess the contribution of the idle operation of the main systems in the experimental setup (in idle mode) to the overall spectrum of acoustic vibrations. Task 3 – to establish experimentally the acoustic parameters of flat grinding with wheels of various profiles (spectral composition, sound level amplitudes). Task 4 – to perform a qualitative comparison of the data acquired, in order to identify the distinctive features of the acoustic signal during profile grinding. Research methodology The experimental study consists of two stages. The first stage studies the natural vibration frequencies of grinding wheels. The second stage is focused on acoustic signal during processing. Each stage uses a GW of a straight profile and a profiled wheel. GW 1 is a standard straight profile grinding wheel, GW 2 is a grinding wheel profiled for grooving (Fig. 2). Stage 1.Aprerequisite for studying the natural vibrations of the GIWs is the existing relationship between the parameters of natural vibrations: physical and mechanical properties; and the geometric characteristics of a solid body [22]. ( , ) , L f F a C = µ (1) where F (a, μ) is the shape factor dependent on the geometric dimensions of the body, its shape, and Poisson’s ratio; L E C = ρ is the parameter which represents the propagation speed of elastic vibrations in an infinitely long rod, the material of which is similar to the material of the body under consideration; E is the elastic modulus; ρ is the material density. The shape factor F∙(a, μ) in this study is based on recommendations from the reference documentation (GOST R 52710–2007 Abrasive tool. Acoustic method for determining the hardness and sound indices by the acoustic wave propagation speed). The use of the method for determining the natural vibration frequency of the wheels and the sound indices as proposed in this standard is consistent with the aim of the study. The purpose of this stage is to determine the spectral composition of the acoustic signal excited by the impact force in the grinding wheels of various profiles. The variable factor of the experiment is the GW profile. The study parameter is the spectral composition of the natural vibrations of the GW. Stage 2. The indirect (acoustic) characteristic of surface pendulum grinding depends on the tool profile during wear in different modes. The characteristics of the sound generated by similar processes using GW 1 and GW 2 are compared. In addition to geometric parameters, the tools used have no differences the wheel characteristics are identical. Experimental study of the natural vibration frequencies of grinding wheels Yuganov V.S. [23], in his study of low-frequency acoustic vibrations (LAV) during flat grinding, concludes that there is an almost complete coincidence of the informative frequencies characteristic of the grinding process and the natural frequencies of the wheel (Fig. 3). This conclusion was later confirmed by Agafonov V.V. [24]. As a result, the authors affirm that the direct source of vibrations at the informative frequency is the grinding wheel. Based on this assumption, the object of the study is the 2,700 rpm 1 250×32×76 25A Fig. 2. Profile of the tool used: а – GW 1; b – GW 2
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