OBRABOTKAMETALLOV Vol. 27 No. 2 2025 technology Ta b l e 1 3 Response table with Utility Function (UMRR, SR, TWR) pertaining to raw data Level Ig Vg Ton 1 3.27 4.20 3.59 2 3.46 3.52 3.47 3 3.64 2.65 3.32 Delta 0.36 1.54 0.26 Rank 2 1 3 The gap voltage (Vg) has the highest impact, with an F-ratio of 71.05, the highest among all factors. The P-value is 0.000 (<0.05), confirming that it is statistically significant, with a contribution of 85.98 %. This indicates that Vg is the dominant factor affecting the utility function (U). The gap current (Ig) has a moderate effect, with an F-ratio of 3.94, indicating some influence but lower than Vg. The P-value is 0.051, slightly above the significance threshold of 0.05, suggesting a marginally significant effect with a contribution of 4.76 %. This means that the impact of Ig is much lower than that of Vg. The pulse-off time (Toff) has an insignificant effect, with an F-ratio of 2.14, indicating minimal influence. The P-value is 0.164, far above 0.05, confirming that it is statistically insignificant with a contribution of only 2.59 %, making it the least influential factor. The residual error is 6.656 % of the total variation. This error term accounts for unknown or uncontrolled factors affecting the utility function. Since the error percentage is low (<10 %), the model is considered reliable. The standard deviation (S) is 0.2255, which is a small value, indicating minimal variability and a good fit of the model. The R-Squared (R²) value is 93.3 %, meaning that 93.3 % of the variation in the utility function is explained by the model. A substantial R² value indicates a strong relationship among input parameters and the response variable. The adjusted R-squared (R² adj) is 89.7 %, which accounts for the number of predictors. Since it is close to R², this indicates that the model does not contain unnecessary terms, further confirming its reliability. Table 13 demonstrates the effect of process parameters (Ig, Vg, and Ton) on the combined utility function, which integrates multiple responses (UMRR, SR, and TWR) into a single index. The table displays the mean utility function values for each parametric level: – for gap current (Ig), the utility function increases from 3.279 at level 1 to 3.464 at level 2, and further to 3.644 at level 3. The delta value is 0.365, indicating that changes in current have a moderate impact on the response outcomes. Although Ig significantly influences the utility function, it is not the primary determining factor. – for gap voltage (Vg), the utility function values at levels 1, 2, and 3 are 4.207, 3.523, and 2.658, respectively. The highest delta value of 1.549 corresponds to Vg, making it the most influential parameter (Rank 1) affecting the utility function. – for pulse-on time (Ton), the utility function values are 3.593 at level 1, 3.470 at level 2, and 3.324 at level 3. The delta value of 0.269 is the lowest among the parameters, indicating that Ton has the least impact on the utility function (Rank 3). Gap voltage (Vg) is the primary influencing factor on the utility function due to its highest delta value (1.549). The variation of Vg creates substantial effects on the combined responses (UMRR, SR, and TWR). The utility function shows a medium influence from the gap current parameter (Ig) according to its delta value
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