## 3 Results and Discussion
### Data Analysis  
The data obtained during the tensile experiments are substituted into the above equations, and according to Equations (3)-(6) can be calculated for specimens immersed in corrosive solutions with the acidity of PH1, PH5, and PH8, respectively, and then by the length la, tensile ratio \(\lambda\), true stress \(\sigma_{ture}\), strain-hardening modulus \(Gp\), and failure time \(t_{f}\) at fracture of the three groups of specimens after stretching. Each condition the results of the data obtained under each condition are shown in Tables 2-4:  
It is known from the above tables that the strain-hardening modulus of PE pipes are \(-39.75\), \(9.905\), and \(5.6469\) after immersion in corrosive solutions at PH1, PH5, and PH8, respectively. The strain-hardening modulus, which depicts the pattern of change in the material's hardness and strength as the strain grows, is the slope of the strain-hardening interval when a material is stretched and there is an abrupt increase in its stress [29]. Based on the calculations above, a curve was built between the tensile ratio and the real stress, the slope of which is the strain-hardening modulus. The graphs of the tensile ratio versus true stress for the three samples are shown in Figure 6 to illustrate how significant it is to measure the true stress-strain curve. Figure 6 shows the trend of strain-hardening modulus of PE pipe when stretched at PH1, PH5, and PH8, respectively, from the figure it is obvious that the strain-hardening modulus of PE pipe is positive at PH1, PH5, and PH8, which means that the strength of PE pipe increases with the increase of strain-hardening modulus [30; 31; 32]. The strain-hardening curve of the tube at PH5 hardly changes when the tube is first stretched. In contrast, the strain-hardening curve of the tube at PH8 gradually becomes flat in the later stages of stretching [30; 32]. This indicates that at PH8, PE pipe has high deformability \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{\begin{tabular}{c} **Serial** \\ **Number** \\ \end{tabular} } & \begin{tabular}{c} **Length at** \\ **Fracture** \\ **I/mm** \\ \end{tabular} & \begin{tabular}{c} **Tensile Ratio** \\ **\(\lambda\)** \\ \end{tabular} & \
\begin{tabular}{c} **True Stress** \\ **\(\sigma_{ture}\)/MPa** \\ \end{tabular} &
\begin{tabular}{c} **Strain-** \\ **Hardening** \\ **Modulus \(Gp\)** \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 4: PH8 corrosion immersion solution. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{\begin{tabular}{c} **Serial** \\ **Number** \\ \end{tabular} } & \begin{tabular}{c} **Length at** \\ **Fracture** \\ **I/mm** \\ \end{tabular} & \begin{tabular}{c} **Tensile Ratio** \\ **\(\lambda\)** \\ \end{tabular} & \begin{tabular}{c} **True Stress** \\ **\(\sigma_{ture}\)/MPa** \\ \end{tabular} & \begin{tabular}{c} **Strain-** \\ **Hardening** \\ **Modulus \(Gp\)** \\ \end{tabular} \\ \hline \hline \multirow{2}{*}{PH1} & 1 & 49.0631 & 1.9625 & 34.2 & \multirow{2}{*}{\begin{tabular}{c} \\ 2.2109 \\ 35.0546 \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} \\ 35.0546 \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} \\ \(-39.75\) \\ \end{tabular} } \\  & 2 & 180.2725 & 7.2109 & 152.3092 & \multirow{2}{*}{\
\begin{tabular}{c} \\ 35.0546 \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} \\ \(-39.75\) \\ \end{tabular} } \\  & 3 & 48.9328 & 1.9573 & 35.0546 & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: PH1 corrosion immersion solution. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{\begin{tabular}{c} **Serial** \\ **Number** \\ \end{tabular} } & \begin{tabular}{c} **Length at** \\ **Fracture** \\ **I/mm** \\ \end{tabular} & \begin{tabular}{c} **Tensile Ratio** \\ **\(\lambda\)** \\ \end{tabular} & \
\begin{tabular}{c} **True Stress** \\ **\(\sigma_{ture}\)/MPa** \\ \end{tabular} &
\begin{tabular}{c} **Strain-** \\ **Hardening** \\ **Modulus \(Gp\)** \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table}