The program was coded in C++ programming language for Simulated Annealing Algorithm used for two separate objective functions (Eqs. (1) and (2)) with a set of constraints. The program was run for the different decrement factors such as 0.5, 0.6, 0.7, 0.8, 0.9 when determining the minimum delamination using the Simulated Annealing Algorithm to understand the drill diameter effect and drill diameter ratio effect. The optimal values of minimum delamination obtained by running the program with various decrement factors are summarized in Table 1 and Table 2 with respect to the objective functions.
Table 1 Minimum Delamination factor from the effect of drill diameter in SAA
Decrement factor
|
Minimum Delamination factor
|
Optimal drilling parameters
|
Drill diameter (mm)
|
Spindle speed (rpm)
|
Feed rate (mm/min)
|
0.5
|
1.066
|
13.7
|
1724
|
67.2
|
0.6
|
1.087
|
13.1
|
2053
|
207.1
|
0.7
|
1.042
|
9.3
|
2603
|
52.2
|
0.8
|
1.065
|
10.8
|
1273
|
97.8
|
0.9
|
1.037
|
8.1
|
2906
|
66.1
|
Table 2 Minimum Delamination factor from the effect of drill diameter ratio in SAA
Decrement factor
|
Minimum Delamination factor
|
Optimal drilling parameters
|
Drill diameter ratio
|
Spindle speed (rpm)
|
Feed rate (mm/min)
|
0.5
|
1.069
|
0.66
|
2525
|
222.8
|
0.6
|
1.051
|
0.78
|
1744
|
147.8
|
0.7
|
1.034
|
0.73
|
1970
|
70.5
|
0.8
|
1.045
|
0.55
|
2395
|
95.1
|
0.9
|
1.025
|
0.75
|
2520
|
57.4
|
Among the various decrement factors for the drill diameter effect, the SAA running at a decrement factor of 0.9 gives the minimum delamination of 1.037 and confirms the optimal parameters at the drill diameter of Ø8.1 mm, spindle speed of 2906 rpm and feed rate of 66.1 mm/rev. The SAA which was run at decrement factor of 0.9 also provides the minimum delamination of 1.025 for the effect of drill diameter ratio and confirms the corresponding optimal parameters at the drill diameter ratio of 0.75 (Ø8.1mm/Ø10.8mm), spindle speed of 2520 rpm and feed rate of 57.4 mm/rev.
In the optimization of drilling parameters, the minimum delamination factor obtained in relation to the decrement factor is also illustrated in Fig. 8 and Fig. 9. By Fig. 8, it is observed that the delamination by the effect of drill diameter is found to be a minimum at 0.9 decrement factor and from Fig. 9, delamination by the effect of drill diameter ratio is also found to be the minimum at a decrement factor of 0.9.
In comparison, it is noted that the delamination value obtained under the drill diameter ratio effect is lower than the value obtained under the delamination effect of drill diameter. The optimal parameter setting was therefore confirmed at Ø8.1 mm drill diameter, 0.75 drill diameter ratio, 2520 rpm spindle speed and 57.4 mm/min feed rate.
The minimum delamination was recorded as 1.021 for the optimal parameter setting by SN ratio analysis (Panneerselvam and Raghuraman 2015). For this experimentation, regression equation was developed to implement SAA and the optimum parameters were obtained for minimum delamination at 1.025. Table 3 lists the final results of these two techniques. Drilling time was also taken into account for comparison and to ensure the validity of the SAA findings. Eq. 3 was used to find the drilling time corresponding to the optimum parameters obtained from each technique.
Drilling time in minutes, Tm = ( L/(f)) (3)
where,
L, length of drill travel = 25.4 mm + 5 mm
25.4 mm is the thickness of CSMat GFRP plate used for drilling operation, 5 mm is assumed as a drill over travel and tool approach is neglected.
f, feed rate in mm/min
Table 3 reveals that the minimum delamination obtained from the study of SN ratio (Panneerselvam and Raghuraman 2015) is 1.021 and from SAA is 1.025. In these delamination values, a marginal change of less than 1% is observed. Again, it is also observed that there is a decrease in drilling time by 12.82% for the parameters setting obtained from SAA compared to SN ratio analysis. This adds benefits to the drilling of CSMat GFRP by conserving the time and cost. Next, it is found that drill diameter ratio and spindle speed used in SAA are lesser in 6.25% and 16% values compared to the corresponding parameters used in SN ratio analysis. During the drilling operation the decreased drill diameter ratio from 0.8 to 0.75 results in an increased amount of material removal. Moreover, the decreased spindle speed of 2520 rpm from 3000 rpm has a benefit of lowering temperature generation during the drilling operation, which in turn reduces delamination and wear of tool. In addition, SAA’s feed rate is 14.8 percent higher than that of the feed rate optimized by SN ratio analysis. This higher feed rate has an advantage of speeding up the drilling process, saving time and cost. From this discussion, one can confirm that SAA has efficacy in finding precise parameter setting for drilling CSMat GFRP material.
Table 3 Comparison: SN ratio Vs SAA
Sl. No.
|
Optimization Techniques employed
|
Minimum delamination obtained
|
Drilling time required
(sec)
|
at Optimal drilling parameters
|
Drill diameter ratio
|
Spindle speed (rpm)
|
Feed rate (mm/min)
|
1
|
SN ratio
|
1.021
|
36.48
|
0.8
|
3000
|
50
|
2
|
SAA
|
1.025
|
31.8
|
0.75
|
2520
|
57.4
|
Changes
|
0.39% Increase
|
12.82% Decrease
|
6.25% Decrease
|
16% Decrease
|
14.8% Increase
|
3.1 Validating the results of SAA by ANFIS
In this work, ANFIS is employed to validate SAA findings as discussed in the preceding section under the heading of Adaptive Neuro Fuzzy Inference System. Fig. 10 displays the ANFIS model 3D surface plot that correlates drill diameter ratio, spindle speed and feed rate with delamination factor for drilling CSMat GFRP material. Delamination factor increases with decrease of drill diameter ratio (Fig. 10(a) & 10(b)), decrease of spindle speed (Fig. 10(a) & 10(c)) and increase of feed rate (Fig. 10(b) & 10(c)). It is also noted that feed rate ((Fig. 10(b) & 10(c)) has more influence on delamination than drill diameter ratio and spindle speed, and the minimum delamination is observed at 0.8 of drill diameter ratio, 3000 rpm of spindle speed and 50 mm/min of feed rate. Therefore, the 3D surface plot of MATLAB can be used to analyze the interaction effect of input parameters and to obtain optimum parameters for minimal delamination in drilling CSMat GFRP material as per the analysis of SN ratio (Panneerselvam and Raghuraman 2015).
In addition, the experimental data was trained and FIS output was obtained for the number of epochs of 30, and it is seen from Fig. 11 & Fig. 12, FIS output is more in accordance with experimental data at the value of 1.0554e-06 Root Mean Square Error (RMSE) for drill diameter ratio effect on delamination. The FIS output for drill diameter effect on delamination is also found at the value of 1. 0712e-6 Root Mean Square Error (RMSE).
Table 4 Validating the results (Fd1) of SAA by ANFIS
Decrement factor
|
Drill diameter (mm)
|
Spindle speed (rpm)
|
Feed rate (mm/min)
|
Fd1by SAA
|
Fd1 by ANFIS*
|
Error
%
|
0.5
|
13.7
|
1724
|
67.2
|
1.066
|
1.0691
|
-0.31
|
0.6
|
13.1
|
2053
|
207.1
|
1.087
|
1.0869
|
0.01
|
0.7
|
9.3
|
2603
|
52.2
|
1.042
|
1.0346
|
0.74
|
0.8
|
10.8
|
1273
|
97.8
|
1.065
|
1.0638
|
0.12
|
0.9
|
8.1
|
2906
|
66.1
|
1.037
|
1.0311
|
0.59
|
*RMSE = 1.0712 e-06
Consequently, the ANFIS models developed for both cases of delamination under the effects of drill diameter and drill diameter ratio were used to confirm the obtained SAA results, and the comparative results are shown in Table 4 and Table 5 respectively. The findings of the analysis show that the results of SAA are in strong agreement with ANFIS because the error variation is within +/- 1%.
Table 5 Validating the results (Fd2) of SAA by ANFIS
Decrement factor
|
Drill diameter ratio
|
Spindle speed (rpm)
|
Feed rate (mm/min)
|
Fd2by SAA
|
Fd2 by ANFIS*
|
Error
%
|
0.5
|
0.66
|
2525
|
222.8
|
1.069
|
1.0653
|
0.37
|
0.6
|
0.78
|
1744
|
147.8
|
1.051
|
1.0555
|
-0.45
|
0.7
|
0.73
|
1970
|
70.5
|
1.034
|
1.0334
|
0.06
|
0.8
|
0.55
|
2395
|
95.1
|
1.045
|
1.0469
|
-0.19
|
0.9
|
0.75
|
2520
|
57.4
|
1.025
|
1.0266
|
-0.16
|
*RMSE = 1.0554e-06