## 3 Validation with Specim Experiments
### Reconstruction of Impact Load  
The impact-induced strain acquired from the impact load transducer can be utilized to determine the impact load for FE analysis. The important parameters that characterize an impact are the impact peak force, impact duration, and load in the steady state after impact. Although certain studies have converted dynamic loads into equivalent static loads, a static  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Loading Angle: 32\({}^{\circ}\)**} & \multicolumn{2}{c}{**Loading Angle: 47\({}^{\circ}\)**} & \multicolumn{2}{c}{**Loading Angle: 65\({}^{\circ}\)**} \\ \hline \multirow{2}{*}{**Set**} & **Peak Strain** (\(\mu\)) & **Impact Duration (s)** & **Peak Strain** (\(\mu\)) & **Impact Duration (s)** & **Peak Strain** (\(\mu\)) & **Impact Duration (s)** \\ \hline
1. & \(-\)79.25 & 0.0044 & \(-\)113.25 & 0.0044 & \(-\)167.75 & 0.0044 \\
2. & \(-\)78.25 & 0.0044 & \(-\)128.75 & 0.0048 & \(-\)166.00 & 0.0044 \\
3. & \(-\)81.75 & 0.0044 & \(-\)123.50 & 0.0048 & \(-\)163.75 & 0.0044 \\
4. & \(-\)79.75 & 0.0044 & \(-\)119.25 & 0.0049 & \(-\)170.00 & 0.0044 \\
5. & \(-\)78.00 & 0.0044 & \(-\)120.00 & 0.0044 & \(-\)169.25 & 0.0044 \\
6. & \(-\)75.50 & 0.0044 & \(-\)115.00 & 0.0049 & \(-\)171.00 & 0.0049 \\
7. & \(-\)84.50 & 0.0044 & \(-\)129.75 & 0.0044 & \(-\)166.75 & 0.0044 \\
8. & \(-\)77.00 & 0.0044 & \(-\)121.75 & 0.0040 & \(-\)167.00 & 0.0044 \\
9. & \(-\)74.25 & 0.0049 & \(-\)116.00 & 0.0049 & \(-\)167.25 & 0.0044 \\
10. & \(-\)72.00 & 0.0044 & \(-\)125.75 & 0.0044 & \(-\)175.25 & 0.0044 \\ \hline Standard deviation & \multirow{2}{*}{3.63} & \multirow{2}{*}{0.0002} & \multirow{2}{*}{5.68} & \multirow{2}{*}{0.0003} & \multirow{2}{*}{3.18} & \multirow{2}{*}{0.0002} \\ \hline Average & \(-\)79.25 & 0.0045 & \(-\)121.30 & 0.0046 & \(-\)168.40 & 0.0045 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Strain data measured with impact load transducer in impact experiments.  
Figure 3: Results of impact experiments. (**a**) Time-domain strain signal of impact load transducer with 10 consecutive impacts; (**b**) a sequence of time-domain strain signal.  
load cannot represent dynamic effects, particularly peak loads that result from dynamic impact. Investigations of the peak load magnitude and timing of a beam structure under impulse loads of triangular, sinusoidal, and trapezoidal shapes showed that simulations using the triangular load curves display the highest agreement with the results of the actual impact [26]. The results of our specimen experiments also illustrate that the time-domain strain signal measured by the transducer can be characterized by peak strain and impact duration. This demonstrates the validity of the adoption of a triangular load curve. In all the three experiments, the impact duration was divided uniformly by the peak strain point. Thus, we reconstructed the impact load by adopting a triangular shape, which is defined by the peak load magnitude and impact duration. The average strain value is converted to a load by using the developed model, as shown in Equation (1). The load curves for the three laboratory impact experiments with different loading angles are reconstructed based on the average strain data of 10 consecutive impacts (Figure 4).