# Evaluation of Accelerator Pedal Strength under Critical Loads Using the Finite Element Method
## 3 Results
### Shock Load Task  
The permissible yield strength, equal to 120 MPa for this most difficult case, corresponded to the lower strength limit of Silumin (casting under pressure). The time distribution of the dynamic load in the conditions of the full-scale tests is presented in Figure 3b: the loads started with 1000 N and continued up to 3500 N until the end of the period of 0.2 s. To perform this FEA, the following working station configuration was used: two physical Intel Xeon 24-core processors, RAM 48 Gb, NVIDIA GeForce 4 Gb video; total calculation time was 7 h 47 min.  
The results of the shock loads task are as follows: being a relatively fragile material, Silumin showed a fracture in the appropriate location--the area of the pedal support which abuts against the bolt travel limiter (Figure 9). The stress was 124 MPa (Figure 13), which exceeded the yield point of the used material under the shock load conditions (when the load reached a value of ca. 2500-2600 N). The Ansys limit of the yield strength was set at 120 MPa for Silumin 4000 (Table 1). Silumin 4000 is a fragile material, as was evidenced in the real conditions of what was observed during the real tests (Figure 16). Although it demonstrated minimal plastic deformation during the load process, the pedal cracked almost at once as the load reached the maximum value (2255.5 N--Table 3), without demonstration of any visually significant plastic deformations and without reaching the 210 MPa of the tensile strength indicated by the manufacturer of Silumin 4000. It is visible on the video timer (Figure 16b)--both states of the pedal (intact and broken) occur in the same second of the video (00:36 s)--and this correlates with the FEA results  
Figure 11: Stress map of the pedal’s foot part (inverse task conditions).  
(Figure 13a--before the rupture and Figure 13b--at the first moment of rupture). This real-life behavior prompted the authors to set the stress-strain characteristics in \"Plasticity toolbox\" in the \"Engineering data component\" of the Ansys materials section as close to the pedal behavior of the natural sample of Silumin as possible. Thus, it became clear that it was necessary to focus on achieving the yield point, because the real value of the tensile strength of the pedal material was different than 210 MPa (Table 1). Moreover, as a result of testing the strength of full-scale pedal samples, the values of breaking loads ranged from 8 to 12%, which indicated differences in the technology of manufacturing castings. It was concluded, then, that the maximum value of 180 MPa of the yield strength of Silumin 4000 may be relevant for castings made under very high pressure. On the other hand, all of the pedal samples actually provided a twice-higher strength safety factor relative to the load of 1000 N required in UNECE R 13. The top part of the pedal cracked (Figure 14), so the structure has lost its integrity and cannot be used anymore. This was confirmed by the natural test results (Figure 14a)--photos of the destroyed samples demonstrate the rupture of the pedal.  
Figure 12: Stress maps of the pedal model under the hybrid task: (**a**) assembly; (**b**) pin; (**c**) foot part of pedal.  
Figure 13: Pedal stress in conditions of shock loads task—views of stress maps: (**a**) before the rupture; (**b**) first moment of rupture; (**c**) corrupted pedal.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Pedal Breaking Stress, MPa** & \multicolumn{3}{c}{**Pedal Breaking Load, N**} \\ \hline
**Yield Stress of** & **Calculated** & **Experimental** & **Calculated** & **Error \(\Delta\), \%** \\
**Silumin** & & & & \\ \hline
120 & 124 & 2255.5 & 2500 & 9.8\% \\ \hline \hline \end{tabular}
\end{table}
Table 3: Comparison of calculated result and average result of natural experiments.