## 4 Validation with Automotive Production Equipment: Jig Structure  
### Experimental Set-Up  
The method developed for identifying impact loads was validated at a practical scale. During the vehicle manufacturing process, production equipment such as the jig structure sustain the impact load of descending vehicle chassis. Impact experiments with vehicle  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Validation Point 1**} & \multicolumn{3}{c}{**Validation Point 2**} \\ \cline{2-7}  & \(\mathbf{65^{\circ}}\) & \(\mathbf{47^{\circ}}\) & \(\mathbf{32^{\circ}}\) & \(\mathbf{65^{\circ}}\) & \(\mathbf{47^{\circ}}\) & \(\mathbf{32^{\circ}}\) \\ \hline \multirow{2}{*}{**Set**} & **Peak** & **Peak** & **Peak** & **Peak** & **Peak** & **Peak** \\  & **Strain** (\(\mu\)) & **Strain** (\(\mu\)) & **Strain** (\(\mu\)) & **Strain** (\(\mu\)) & **Strain** (\(\mu\)) & **Strain** (\(\mu\)) & **Strain** (\(\mu\)) \\ \hline
1. & 78.00 & 52.00 & 39.00 & \(-81.00\) & \(-51.00\) & \(-41.00\) \\
2. & 76.00 & 57.00 & 36.00 & \(-84.00\) & \(-60.00\) & \(-39.00\) \\
3. & 76.00 & 51.00 & 37.00 & \(-83.00\) & \(-62.00\) & \(-39.00\) \\
4. & 74.00 & 48.00 & 38.00 & \(-79.00\) & \(-64.00\) & \(-41.00\) \\
5. & 74.00 & 57.00 & 38.00 & \(-86.00\) & \(-60.00\) & \(-42.00\) \\
6. & 71.00 & 58.00 & 38.00 & \(-81.00\) & \(-55.00\) & \(-39.00\) \\
7. & 78.00 & 56.00 & 37.00 & \(-80.00\) & \(-58.00\) & \(-43.00\) \\
8. & 73.00 & 52.00 & 36.00 & \(-81.00\) & \(-53.00\) & \(-41.00\) \\
9. & 76.00 & 54.00 & 37.00 & \(-77.00\) & \(-51.00\) & \(-42.00\) \\
10. & 78.00 & 50.00 & 36.00 & \(-75.00\) & \(-56.00\) & \(-39.00\) \\ \hline Standard deviation & \multirow{2}{*}{2.37} & \multirow{2}{*}{3.41} & \multirow{2}{*}{1.03} & \multirow{2}{*}{3.23} & \multirow{2}{*}{1.55} & \multirow{2}{*}{1.65} \\ \cline{1-1} \cline{5-5} Average & & & & & & \\ \hline Average & 75.40 & 53.50 & 37.20 & \(-80.70\) & \(-57.00\) & \(-40.50\) \\ \hline \hline \end{tabular}
\end{table}
Table 2: Peak strain data measured at validation points in the lab-scale impact experiments.  
Figure 5: Validation of reconstructed impact load. (**a**) Contour representations of y-axis strain distribution with validation elements of Validation point 1; (**b**) contour representations of y-axis strain distribution with validation elements of Validation point 2; (**c**) comparison of experimentally measured and numerically calculated peak strain values.  
chassis were conducted in the Hyundai Motors production line. The loading speeds of the vehicle chassis are controlled by varying the pressure of the hydraulic system. In this experiment, two loading velocities were examined: 246.8 and 287.4 mm/s. To obtain accurate strain data from the impact load transducer, 11 sets of impact experiments were performed for each loading velocity. The production line with jig structures and vehicle chassis is presented in Figure 6a, and an individual jig structure is shown in Figure 6b. To determine the impact load provided by a descending vehicle chassis, the impact load transducer was mounted at the point of contact between the jig structure and vehicle chassis, as shown in Figure 6c. Because the loading position has a circular cavity, the impact load transducer was mounted at a marginal distance from the center of the impact point to ensure complete contact between the impact load transducer and vehicle chassis. To validate the predicted impact load, strain gauges were attached to the jig structures to measure the strain generated in the jig structure by the impact of vehicle chassis. Three regions with high strain were selected as the validation points, as shown in Figure 6d,e. The structural strains measured at the validation points in the experiments were compared with the strains calculated by numerical simulation using the impact load predicted by the method developed for determining impact loads.