## 3 Results and Discussion
### Post-Peak Strain Energy Density  
Table 7 and Figures 11 and 12 illustrate post-peak strain energy density results for AC-13 and SMA-13, respectively. Similar to the pre-peak strain energy density, as shown in Figures 11 and 12, at the same test temperature, the post-peak strain energy density of AC-13 and SMA-13 both increases under short-term aging and gradually decrease as the degree of aging moves toward long-term aging. Concretely, for AC-13, the post-peak strain energy density under short-term aging ascends by 53% (1 \({}^{\circ}\)C), 42% (20 \({}^{\circ}\)C) and 53% (30 \({}^{\circ}\)C) and 63% (40 \({}^{\circ}\)C). When the degree of aging extends to LTOA2d, there is a violent drop in the post-peak strain energy density by 36% (10 \({}^{\circ}\)C, 20 \({}^{\circ}\)C and 40 \({}^{\circ}\)C) and 31% (20 \({}^{\circ}\)C). However, when the degree of aging deepens further, there is a tendency to decrease more flatly, with a decrease rate of 14% (10 \({}^{\circ}\)C and 30 \({}^{\circ}\)C), 11% (20 \({}^{\circ}\)C) and 12% (40 \({}^{\circ}\)C). In the same way, for SMA-13, the post-peak strain energy density under short-term aging ascends by 29% (10 \({}^{\circ}\)C), 25% (20 \({}^{\circ}\)C and 30 \({}^{\circ}\)C) and 34% (40 \({}^{\circ}\)C). When degree of aging extends to LTOA2d, there is a dramatic drop in the post-peak strain energy density by 20% (10 \({}^{\circ}\)C), 31% (20 \({}^{\circ}\)C) and 38% (30 \({}^{\circ}\)C and 40 \({}^{\circ}\)C). With the continuous deepening of the degree of aging, the descent trend becomes steadier, with a decrease rate of 6% 10 \({}^{\circ}\)C), 3% (20 \({}^{\circ}\)C), 10% (30 \({}^{\circ}\)C) and 13% (40 \({}^{\circ}\)C). \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Colection**} & **Date** & **Description** & **Description** & **UEs** & **UEs** & **UEs** & **UEs** & **UEs** & **UEs** & **UEs** & **UEs** & **UEs** & **UEs** & **UEs** & **UEs** & **UEs** & **UEs** & **UEs** \\ \cline{2-15}  & **Type** & **C** & **Description** & **Description** & **Description** & **Description** & **Description** & **Description** & **Description** & **Description** & **Description** & **Description** & **Description** & **Description** & **Description** & **Description** & **Description** & **Description** & **Description** & **Description** \\ \hline \hline \multirow{15}{*}{**Colection**} & **Date** & **1** & 3022 & & & & & & & & & & & & & & & & & & & & & & & & & & & \\ \cline{2-15}  & **10** & **2** & **1000** & **1000** & **10  
Moreover, when the aging degree remains the same, as the test temperature increases from 10 \({}^{\circ}\)C to 20 \({}^{\circ}\)C, the post-strain energy density of AC-13 grows slightly, by 41% (UA and LTOA2d), 31% (STOA), 49% (LTOA5d), 64% (LTOA8d). When the test temperature reaches t30 \({}^{\circ}\)C, the post-strain energy density drops dramatically, with a decrease rate of 32% (UA, LTOA2d and LTOA5d), 27% (STOA) and 43% (LTOA8d). Comparatively, the descent trend of the post-strain energy density becomes stable, with a decrease rate of 12% (UA and LTOA2d), 17% (STOA) and 22% (LTOA5d LTOA8d). Ulteriorly, the post-strain energy density of SMA-13 grows slightly, by 50% (UA), 44% (STOA), 25% (LTOA2d) and 35% (LTOA8d), as the test temperature climbs from 10 \({}^{\circ}\)C to 20 \({}^{\circ}\)C. Furthermore, when the test temperature reaches 30 \({}^{\circ}\)C, a sudden drop appears in the post-strain energy density of  
Figure 11: Post-peak strain energy density versus test temperature for AC-13 under different degrees of aging. Figure 12: Post-peak strain energy density versus test temperature for SMA-13 under different degrees of aging. SMA-13, with a decrease rate of 23% (UA and STOA), 30% (LTOA2d and LTOA5d) and 47% (LTOA8d). Furthermore, when test temperature rises from 30 \({}^{\circ}\)C to 40 \({}^{\circ}\)C, it also decreases more steadily, with a decrease rate of 6% (UA) 2% (STOA), 4% (LTOA2d), 11% (LTOA5d and LTOA8d).