OBRABOTKAMETALLOV Vol. 23 No. 3 2021 MATERIAL SCIENCE EQUIPMENT. INSTRUMENTS 6 4 cluster, dispersion ellipsoids with 95 % probability with respect to the grouping centers were determined, allowing the definition of separating hyperplanes satisfying the Bayesian rule. This defines the information model of diagnostics. It allows, on the basis of VAE measurement, to estimate the wear belonging to one of the clusters, an example of which in the planes “П1–П2” and “П1–П3” is given in fig. 8. Projections of scattering ellipses with 95 % probability and traces of hyperplanes are also given there. The above illustrations show: if only П1 is considered as an informative attribute, the information model can estimate only two wear classes. The given material is only an example. On the basis of the revealed peculiarities of frequency response changes in the process of wear development it is possible to build more complex information models, but not always the increase of complexity gives the increase of diagnostics accuracy. The information model is the basis for the construction of the implemented in production system of wear diagnostics on automatic lines for the production of shafts of bearing systems of combine harvesters. Results and discussion When building systems of dynamic diagnostics of machining processes, including tool wear, two procedures are considered. The first one includes the construction of information space. The second one considers the decisive rules that allow classification on the basis of wear. The main significance is the construction of information space. It is shown above that the development of wear changes two systems of indicators. The development of wear causes variations in the dynamic coupling parameters, which is reflected in changes in the frequency response. It is manifested in the frequency range lying within the bandwidth of the tool subsystem. These are frequencies within the range of 100–2,000 Hz. The cutting process is accompanied by force emission, the sources of which are associated with periodic interactions during the formation of sliding surfaces, as well as in the zone of interface between the auxiliary flanks of the tool and the workpiece. Moreover, the interactions in the area of auxiliary flank depend on its contact area, the value of which depends on wear. The frequency composition of the force emission is in the range exceeding the bandwidth of the dynamic cutting system. These two systems, based on identifying the connection between tool wear and physical concepts of its influence on the frequency properties of VAE, can be used as the basis for constructing information signs for wear diagnostics. The analysis shows that the development of wear causes a change in the spectrum of VAE. This allows us to define the following information signs of wear display in the VAE signal. The development of wear causes irreversible changes in the parameters of dynamic coupling, which cause changes in the properties of the frequency response. Among them we note the displacement of natural frequencies of subsystems, reduction of its goodness of fit, redistribution of vibration intensity in low-frequency and high-frequency regions, formation and development of periodicities in the signal spectrum, the repetition rate of which is equal to the rotation frequency of the workpiece, and so on. The development of non-stationarity of spectra as wear progresses, especially in the area of critical wear, etc., is also noted. In the region outside the bandwidth of the tool subsystem, the development of wear causes a change in the properties of the force emission signal and its representation in deformation displacements, its velocities and accelerations. The force emission signal can be represented as a random pulse sequence. In this case, two main frequencies of the emission signal burst change, which are modelled by the force noise caused by the processes of periodic formation of sliding surfaces, as well as by periodic random interactions in the contact between the auxiliary flank of the tool and the workpiece. During the development of wear, a broadening of its spectral lines and an increase in the intensity of these signals, accompanied by its instability, are observed. The given example of building a system of vibroacoustic diagnostics of wear in the process of machining, introduced in industry, has shown the applied efficiency of using the dependence of frequency properties of the VAE signal for building information models of diagnostics. The example far
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