OBRABOTKAMETALLOV Vol. 23 No. 3 2021 MATERIAL SCIENCE EQUIPMENT. INSTRUMENTS 6 2 4 and the tool drive subsystem, as it influences the trace left by the tool on the workpiece surface. Since the distribution of vibration energy losses depends on the materials of the “cutter-workpiece” pair, the vibration data recorded during the cutting process is the most informative. Measurement of vibration data is possible during the first technological operation in the process of part machining, as a result of which variations in the geometrical shape of the workpiece and physical and mechanical properties of the surface layer of the material, which occur during the cutting process, are eliminated. Data processing is based on spectral analysis methods. In the model of vibration disturbances it is also necessary to add a source of random noise component, which is always present in real technical systems, e.g. generated by chip formation processes. In the second stage, numerical simulation of the dynamics of the cutting process is carried out using real data on the vibration characteristics of the process for a pair of materials at different cutting modes. As a result of the simulation, based on the analysis of the force characteristics, the modes are selected that provide the highest turning performance from the condition of minimisation of the components of the cutting forces F1 (0), F 2 (0), F 3 (0). In the third stage, the geometric topology of the workpiece surface is constructed. Based on the calculated signal of tool deformation displacements, surface quality estimates are calculated, e.g. by the roughness parameter Ra. The final result of the simulation study is the cutting modes that provide the highest turning performance and the required surface quality. Simulating the dynamics of the cutting process and its representation in the geometrical topology of the workpiece surface As an example for the simulation, a longitudinal turning of a part with a diameter D = 114 mm made of stainless steel A508-3 (0.1 % C-Mn-2 % Ni-Mo-V in Russia) with coated carbide inserts HS123 (79 % WC-15 % TiC-6 % Co in Russia) is considered. At the first stage, in order to clarify the frequency components of the tool vibrations, the vibration sequences in the directions X1, X2, X3 were measured experimentally using vibration accelerometers mounted on the tool. The spectral characteristics of the signals are shown (fig. 3). Three frequency peaks in each direction of the tool vibration activity are clearly visible in Figure 3 ω1 = 460 Hz; ω2 = 790 Hz; ω3 = 1.42 kHz. The measured frequency components are the parameters of harmonic functions used in the simulation model of the cutting process as disturbances (4). According to the research methodology, the “white” noise signal on the perturbation channels was introduced into the simulation model during perturbation modelling for the qualitative simulation result. Parameters of the tool subsystem: stiffness and dissipation matrix coefficients are given in Table 1, taking into account that m = 0.27∙10-3 kgs2/mm; front angle γ = 10o, back angle α = 10o and cutting edge angle φ = 90o. The parameters of the dynamic coupling are given in Table 2. The simulation results of the cutting process under various process conditions are shown in fig. 4, cutting depth is a constant value tp (0) = 0.5 mm. a b c Fig. 3. Power spectra of vibration acceleration sequences in relative units to dispersion along the directions: a – X1; b – X2; c – X3 for modes Sp (0) = 0.15 mm/rev; t p (0) = 0.5 mm; V 3 (0) = 190 m/min
RkJQdWJsaXNoZXIy MTk0ODM1