## 2 Materials and Methods
Figure 4: Flow diagram of the welding process with each different joint thickness. For each case, two identical test pieces (same diameters, pressure, time, and test intensity) of each combination were made in order to perform two different physical tests: tensile and shear force. Two test pieces with identical labels (Figure 5) were tested to determine the physical parameters in question. A preliminary step was to verify the quality of the joint, by measuring the joint thickness. This process is shown in Figure 6a. This non-destructive sampling was performed on the six welds of each test piece. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Joint Thickness (mm)**} & \multicolumn{2}{c}{**Equipment Parameters**} & \multirow{2}{*}{**N\({}^{o}\) Specim**} \\ \cline{2-3}  & **Phase-1 (Contact)** & **Phase-2 (Welding)** & \\ \hline \multirow{3}{*}{\(16\)} & A\({}^{*0.5}\) & 40\%-50\%-60\%-70\%-80\% & \multirow{3}{*}{45} \\  & t\({}^{*1}\)/3 & 25-35-45 & & \\  & 5\_6\_7 & 5\_6\_7 & & \\ \hline \multirow{3}{*}{\(18\)} & A\({}^{*0.5}\) & 40\%-50\%-60\%-70\%-80\% & \multirow{3}{*}{45} \\  & t\({}^{*1}\)/3 & 29-40-51 & & \\  & 5\_6\_7 & 5\_6\_7 & & \\ \hline \multirow{3}{*}{\(20\)} & A\({}^{*0.5}\) & 40\%-50\%-60\%-70\%-80\% & \multirow{3}{*}{45} \\  & t\({}^{*1}\)/3 & 32-44-57 & & \\  & 5\_6\_7 & 5\_6\_7 & & \\ \hline \multirow{3}{*}{\(22\)} & A\({}^{*0.5}\) & 40\%-50\%-60\%-70\%-80\% & \multirow{3}{*}{45} \\  & t\({}^{*1}\)/3 & 38-53-68 & & \\  & 5\_6\_7 & 5\_6\_7 & & \\ \hline \multirow{3}{*}{\(26\)} & A\({}^{*0.5}\) & 40\%-50\%-60\%-70\%-80\% & \multirow{3}{*}{45} \\  & t\({}^{*1}\)/3 & 41-57-74 & & \\ \cline{1-1}  & 5\_6\_7 & 5\_6\_7 & & \\ \hline \multirow{3}{*}{\(28\)} & A\({}^{*0.5}\) & 40\%-50\%-60\%-70\%-80\% & \multirow{3}{*}{45} \\  & t\({}^{*1}\)/3 & 44-62-79 & & \\ \cline{1-1}  & 5\_6\_7 & 5\_6\_7 & & \\ \hline \multirow{3}{*}{\(32\)} & A\({}^{*0.5}\) & 40\%-50\%-60\%-70\%-80\% & \multirow{3}{*}{45} \\  & t\({}^{*1}\)/3 & 50-70-90 & & \\ \cline{1-1}  & 5\_6\_7 & 5\_6\_7 & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The welding parameter commands for the A-t-p equipment. Figure 5: Label nomenclature of the joint thickness (12 + 12 = 24 mm). To this end, a Palmer micrometer or caliper was used, which uses a micrometer screw to assess joint thickness with great precision (Figure 6a). The micrometer spindle is moved toward the anvil until it touches the piece whose thickness is being measured. The measurement obtained can be used to confirm the theoretical thickness (Diameter A + Diameter B) and to determine whether the weld is acceptable. To do this, the aim is to obtain the difference between the resulting and the theoretical joint thicknesses and to establish a difference threshold to be able to assess its quality. Thus, the thickness of the resulting joint was compared with the nominal theoretical value (Diameter A + Diameter B), and if the former was less than 85% of the latter, that weld was discarded given that it had excessive denting (Figure 6b). After performing the tests, we located the threshold value from which the joint geometry was permanently deformed. This situation was not assumable in the rebar configuration. The welds must be broken to study the strength performance (Figure 7a). Specific equipment was used to perform the pulling force tests: the Servosis ME-420/20, which registers the precise force necessary to break the weld at each welded point (Figure 7b). The welds were subjected to two different tests using specially designed tools. The weld failures were generated by subjecting the joint to shear or tensile tests. The shear force test was conducted with the help of a single tool: the Diameter A rod was fixed and the lower clamp moved enacting force on the Diameter B rod, as shown in Figure 8a. This is how the amount of force necessary to incur failure by shear force (\(\tau\)) was determined. Figure 6: (a) Measurement of the joint. (b) Example of a discarded weld. Figure 7: (a) Broken weld of a test piece, (b) Servosis ME-420/20.