OBRABOTKAMETALLOV MATERIAL SCIENCE Том 23 № 3 2021 EQUIPMEN . INSTRUM TS Vol. 6 No. 3 2024 Ta b l e 4 Matrix of experimental results Exp. No. Ra, µm γ, g 1 2.9475 0.0062 2 4.33693 0.01 3 3.0374 0.0059 4 3.34163 0.0172 5 2.8057 0.0082 6 3.8035 0.0021 7 3.016 0.0161 8 4.6673 0.0156 9 3.50183 0.001 Results and discussion As a result of the FFE empirical dependencies were obtained. These dependencies establish the relationship between output parameters and processing modes. The linear relationship between the independent variable and input factors is assumed in the paper. The empirical model of the dependence of the TE wear parameter on the machining modes (current I (A), voltage U (W), pulse on time Ton (μs)), has the following form (1): γ = + × + × - × - 0.002997 0.00214325 0.00010806 0.00027248 on I U T - × × + × × + × × 0.00005425 0.0000028992 0.00003276 . on on I U T U I T (1) Fisher criterion was used to test the adequacy of the mathematical model: = < 2 2 , adeq calc table y S F T S (2) where Fcalc and Ftable are the values of the Fisher criterion (respectively, calculated and tabulated); S 2 adeq is the variance of adequacy; S2 y is the variance of reproducibility. = < = 0.003 3.24. calc table F T (3) Based on the fact that Fcalc < Ftable at the level of dependence α = 0.05, we can conclude that the model satisfies the criterion of adequacy. The obtained mathematical model reliably reflects the dependence of the output parameter (wear and tear) on the modes of copy-piercing EDM. Fig. 4 presents the graph of the response hypersurface. The graph establishes the dependence of input data (processing modes: I, U, Ton = 75 μs) on the TE wear (γ). It is established that in the minimum mode at current of I = 4 A and voltage of U = 50 V the wear of TE is γ = 0.0063875 g. At current of I = 8 A and voltage of U = 50 V the maximum wear of TE is fixed and is γ = 0.13938 g. Physical features of the character of material destruction as a result of EDM influence directly depend on the value of energy of a single discharge. The value of the pulse (discharge) energy increases in direct proportion with the increase of current strength. Further there is an electroerosive destruction of TE. At high current values, the temperature in the spark formation zone increases, which also leads to intensive wear of TE. The empirical model of dependence of the surface quality parameter (roughness, Ra) of TE on processing modes (current I (A), voltage U (W), pulse on time Ton (μs)), has the form (4):
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