# Development of an Artificial Intelligence-Based System for Predicting Weld Bead Geometry
## 2 Materials and Methods
### Experiments for Generating Data and Development of Regression Models  
Experiments were conducted on the SMAW, MIG, and TIG welding machines. For carrying out SMAW, MIG, and TIG welding processes, we used ARC 200, MIG 200, and TIG 200 welding machines, respectively. For carrying out the experiments, the welding process parameters that highly influence the quality of weld joints were selected. The ranges of welding process parameters and experimental results are shown in Tables 1-6 for the SMAW, MIG, and TIG welding process, respectively. These ranges were selected according to the specification of machines, base material, and electrode material and consideration of the welding experiments as well as the reported research on the SMAW, MIG, and TIG welding processes [1; 2; 3]. The two-level full factorial design method was used for designing experiments and generating mathematical models [24; 25]. With the SMAW welding process, the input process parameters that highly influence the quality of weld joints include welding current, welding speed, arc length, electrode diameter, and welding gap. The values for the SMAW welding process are shown in Table 1. Base metal plates in a square butt weld joint with a flat position are structural mild steel plates; the thickness of each plate is 6 mm. To obtain regression models which show the relationship between the input parameters and the weld bead size as shown in Figure 5, the two-level full factorial design method was used to create a design matrix for this experiment. With 2 levels and 5 parameters, a total of 32 experiments were conducted as shown in Table 2.  
Figure 4: Mechanism of MIG welding process. \begin{table}
\begin{tabular}{c c c c c} \hline
**Parameter** & **Unit** & **Notation** & **Minimum Value (\(-\))** & **Maximum Value (\(+\))** \\ \hline Welding current & A & \(A\) & 60 & 90 \\ \hline Arc length & mm & \(B\) & 1.2 & 3.0 \\ \hline Welding speed & mm/min & \(C\) & 70 & 120 \\ \hline Electrode diameter & mm & \(D\) & 2.6 & 4.0 \\ \hline Joint gap & mm & \(E\) & 1.0 & 3.0 \\ \hline \end{tabular}
\end{table} 
Table 1: Input parameters for SMAW process [1]. In consideration of the independent effects of welding process parameters and the linear regression model, the weld bead dimensions in the SMAW welding process including bead width (K\({}_{\text{S}}\)), reinforcement (R\({}_{\text{S}}\)), and penetration (P\({}_{\text{S}}\)) are calculated as follows:  
\[\text{K}_{\text{S}}=9.41-0.0072\,A+0.064\,B-0.00697\,C+0.123\,D+0.293\,E \tag{1}\]  
\[\text{R}_{\text{S}}=2.094-0.00826\,A-0.0044\,B-0.00102\,C-0.022\,D+0.0285\,E \tag{2}\]  
\[\text{P}_{\text{S}}=1.707+0.00272\,A-0.0406\,B+0.00351\,C+0.007\,D-0.0942\,E \tag{3}\]  
For the MIG welding process, the input process parameters include welding speed, arc voltage, wire feed rate, gas flow rate, nozzle-to-plate distance, and torch angle. The values for the MIG welding process are shown in Table 3. Base metal plates are structural mild steel plates; the thickness of each plate is 8 mm. With 2 levels and 6 parameters, a total of 64 experiments were conducted as shown in Table 4.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Number** & \(a\) & \(b\)  
The linear regression model for calculating the weld bead dimensions in the MIG welding process including bead width (K\({}_{\text{M}}\)), reinforcement (R\({}_{\text{M}}\)), and penetration (P\({}_{\text{M}}\)) are as follows:  
\[\text{K}_{\text{M}}=-6.502-0.1\,a+0.57969\,b+0.5813\,c+0.01562\,d-0.05375\,e+0.00 271\,f \tag{4}\]  
\[\text{R}_{\text{M}}=8.1234-0.037187\,a-0.14219\,b+0.15625\,c-0.00469\,d+0.01875 \,e-0.01f \tag{5}\]  
\[\text{P}_{\text{M}}=-0.9703-0.015312\,a+0.09531\,b+0.275\,c+0.01875\,d-0.005\,e- 0.013125\,f \tag{6}\]  
For the TIG welding process, the input process parameters include welding speed, arc voltage, wire feed rate, % cleaning, joint gap, and welding current. The values for TIG welding process are shown in Table 5.  
Two structural mild steel plates with 6 mm thickness were used for experiments.