## 3 Results and Discussion
### Stress Relaxation Characteristics of Machine-Harvested Seed Cotton  
\(T_{1}\) reflects the rapid decay rate of stress relaxation; The smaller \(T_{1}\) is, the faster the stress decay of machine-harvested seed cotton changes. \(T_{1}\) determines the optimal length of wrapping and winding time of machine-harvested seed cotton after baling [25]; \(E_{e}\) reflects the ability of machine-harvested seed cotton to recover in the process of stress relaxation; the smaller \(E_{e}\) is, the less loose wrapping and damage phenomenon of the machine-harvested seed cotton can be reduced after wrapping. \(\varepsilon\) reflects the residual stress ratio of machine-harvested seed cotton after stress relaxation, similar to \(E_{e}\), which indicates the stress relaxation of machine-harvested seed cotton. The smaller \(\varepsilon\) is, the more it can be used to measure the effect of stress relaxation, and its calculation formula is shown in Equation (5):  
\[\varepsilon=\frac{\sigma_{\mathrm{s}}}{\sigma_{0}}\times 100, \tag{5}\]  
where  
\(\sigma_{\mathrm{s}}\) = the stress after relaxation stabilization (MPa)  
\(\sigma_{0}\) = the stress after reaching the set strain (MPa)  
\(\varepsilon\) = the residual stress ratio (%). To reveal the effect of moisture content, trash content, compression density, and cross-sectional dimensions of machine-harvested seed cotton on stress relaxation characteristic parameters, the five-element Maxwell model was used to fit all stress relaxation curves of machine-harvested seed cotton, and the stress relaxation characteristic parameters were obtained, taking the average of the three groups of experiments, as shown in Table 2. A correlational analysis of stress relaxation characteristics parameters was conducted, as shown in Table 3. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Factors**} & \multirow{2}{*}{**Levels**} & \(\mathbf{E_{1}}\) & \(\mathbf{E_{2}}\) & \(\mathbf{E_{e}}\) & \(\eta_{1}\) & \(\eta_{2}\) & \(\epsilon\) (\%) & \(\epsilon\) (\%) & \(R^{2}\) \\  & & **(MPa)** & **(MPa)** & **(MPa)** & **(MPa-s)** & **(MPa-s)** & **(MPa-s)** & **(MPa-s)** & **\(\epsilon\) (\%)** & \(R^{2}\) \\ \hline \multirow{8}{*}{Moisture content (\%)} & 6 & 0.0735 & 0.0378 & 0.1296 & 0.379 & 3.795 & 5.158 & 100.410 & 54.168 & 0.999 \\  & 10 & 0.0602 & 0.0317 & 0.1099 & 0.306 & 3.222 & 5.085 & 101.646 & 53.302 & 0.999 \\  & 14 & 0.0544 & 0.0284 & 0.0876 & 0.278 & 2.831 & 5.102 & 99.669 & 52.085 & 0.999 \\  & 18 & 0.0486 & 0.0249 & 0.0737 & 0.245 & 2.475 & 5.049 & 99.392 & 50.489 & 0.999 \\  & 22 & 0.0395 & 0.0219 & 0.0573 & 0.201 & 2.205 & 5.090 & 100.694 & 48.748 & 0.999 \\ \hline \multirow{8}{*}{Trash content (\%)} & 8 & 0.0691 & 0.0352 & 0.1843 & 0.348 & 3.546 & 5.031 & 100.735 & 64.173 & 0.999 \\  & 10 & 0.0696 & 0.0345 & 0.2049 & 0.343 & 3.446 & 4.934 & 99.884 & 66.578 & 0.999 \\  & 12 & 0.0844 & 0.0423 & 0.2055 & 0.412 & 4.231 & 4.884 & 100.035 & 62.207 & 0.999 \\  & 14 & 0.0919 & 0.0458 & 0.2187 & 0.451 & 4.604 & 4.912 & 100.524 & 61.810 & 0.999 \\  & 16 & 0.0868 & 0.0431 & 0.2331 & 0.431 & 4.334 & 4.966 & 100.562 & 64.526 & 0.999 \\ \hline \multirow{8}{*}{Compression density (kg\cdot m\({}^{-3}\))} & 200 & 0.0073 & 0.0057 & 0.0396 & 0.045 & 0.631 & 6.202 & 110.678 & 75.684 & 0.997 \\  & 250 & 0.0229 & 0.0165 & 0.0904 & 0.134 & 1.763 & 5.843 & 106.820 & 70.067 & 0.999 \\ \cline{1-1}  & 300 & 0.0634 & 0.0326 & 0.1791 & 0.315 & 3.278 & 4.966 & 100.541 & 65.457 & 0.999 \\ \cline{1-1}  & 350 & 0.1528 & 0.0718 & 0.3887 & 0.738 & 7.073 & 4.830 & 98.511 & 63.651 & 0.999 \\ \cline{1-1}  & 400 & 0.3416 & 0.1528 & 0.7737 & 1.590 & 14.995 & 4.655 & 98.134 & 61.326 & 0.999 \\ \hline \multirow{2}{*}{Cross-sectional dimensions (mm)} & 100 & 0.0394 & 0.0212 & 0.1238 & 0.204 & 2.168 & 5.179 & 102.282 & 67.511 & 0.999 \\ \cline{1-1}  & 150 & 0.0334 & 0.0184 & 0.1046 & 0.173 & 1.822 & 5.167 & 99.032 & 67.106 & 0.999 \\ \cline{1-1}  & 200 & 0.0299 & 0.0160 & 0.0929 & 0.151 & 1.624 & 5.051 & 101.477 & 67.243 & 0.999 \\ \hline \hline \end{tabular}
\end{table}