## 4 Validation  
The fabricated composite was machined at varying conditions and the responses were noted. MRR was evaluated based on the weights of the specimen before and after machining of each sample at the specified settings. The finished samples were tested for surface roughness at M/s Unique Measurement Services, Coimbatore, using a Mitutoyo SJ201 surface tester. The values of the output parameters are tabulated in Table 7.  
The hardness was calculated and the average HRB value was obtained as 61. The hardness was measured using the Vickers hardness-testing equipment located at Amal Jyothi College of Engineering. The values at three different intervals were taken and the average of these three values was considered as the final hardness. The values obtained were 62.1, 60.8 and 61.1. Based on this hardness value calculated, the corresponding equations are considered for the calculation of experimental responses, which are provided in Table 8.  
The average variations were found to be 9.2% and 7.3%, respectively, with the maximum variation of 19.65% for MRR and 17.43% for R\({}_{\text{a}}\). The validated results provided a closer value when compared with the experimental results, and the same can be employed for the prediction of the MRR and R\({}_{\text{a}}\) of the given composite  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Coefficients**} & \multicolumn{8}{c}{**Parameters for R\({}_{\text{a}}\)**} \\ \cline{2-10}  & **Current** & **Current2** & **T\({}_{\text{off}}\)** & **T\({}_{\text{on}}\)** & **A** * **T\({}_{\text{on}}\)** & **A** * **T\({}_{\text{off}}\)** & **T\({}_{\text{off}}\)2** & **T\({}_{\text{on}}\)2** & **Constant** \\ \hline HRB2 & 0.0012 & 0 & 0 & 0.0019 & \(3.914\times 10^{-5}\) & 0 & 0 & \(-2.727\times 10^{-5}\) & 0 \\ \hline HRB & \(-0.148\) & 0.0013 & \(-0.1989\) & \(-0.2238\) & 0.0042 & 0.0008 & 0.0122 & 0.0032 & 1.0143 \\ \hline Constants & 4.6329 & \(-0.0733\) & 13.4258 & 6.6334 & \(-0.1054\) & 0.0703 & \(-0.8286\) & \(-0.0912\) & \(-68.979\) \\ \hline \hline \end{tabular}
\end{table}
Table 6: The coefficients of equations for R\({}_{\text{a}}\).  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Si No** & **Current (A)** & **T\({}_{\text{on}}\) (\#s)** & **T\({}_{\text{off}}\) (\#s)** & **Material Removal** & **Surface Roughness** \\  & & & & **Rate (MRR) [g/min] & **(R\({}_{\text{a}}\)) [\(\mu\)m]** \\ \hline
1 & 6 & 36 & 7 & 0.0577 & 3.0380 \\
2 & 6 & 48 & 8 & 0.0719 & 5.2230 \\
3 & 6 & 56 & 9 & 0.0923 & 7.4640 \\
4 & 9 & 36 & 8 & 0.0924 & 4.6040 \\
5 & 9 & 48 & 9 & 0.1159 & 6.7750 \\
6 & 9 & 56 & 7 & 0.1091 & 8.9170 \\
7 & 12 & 36 & 9 & 0.1010 & 5.6270 \\
8 & 12 & 48 & 7 & 0.1140 & 9.6090 \\
9 & 12 & 56 & 8 & 0.1345 & 9.7150 \\ \hline \hline \end{tabular}
\end{table}
Table 7: Results of validated samples.  
During the machining time, the composite materials melted and partially vaporised. During the pulse-off time, solidification occurred of the liquefied material on the machined-pool surface itself. Meanwhile, the dielectric medium cooled the molten materials and flushed out the machined particle from the machining area. The solidified material on the machined surface created a layer called a white layer or resolidified layer. In addition, the bombardment of heat energy on the material surface created the melting of materials which caused craters on the surface of the materials. There was a possibility of craters to recombine with other craters on the surface and form a valley-like region. This resulted in the formation of higher surface roughness on the particular region on the machined part. The continuous expulsion of molten materials from the machined region also forms a wavy surface and influences the quality of the materials after the machining.