# Crasworthiness Analysis to Evaluate the Performance of TDM-Shielded Street Poles Using FEA
## 4 Results  
### Parameterisation of TDM Thickness on Impact Energy Absorption on Street Pole and Vehicle  
The first analysis that this paper demonstrates is the effect of the TDM-based thickness on street poles and the impact energy to ensure that the impact energy is mitigated due to the presence of the TDM-based reinforcement. Ideally, the impact energy should be reduced for both the vehicle and the street pole so that injury to the passengers can be reduced as much as possible and the risk of the street pole being damaged beyond repairs can be reduced as well. For these results, a common velocity of 17 ms\({}^{-1}\) is used to make a qualitative analysis of this parameterization for both frontal and corner types of collisions. When assessing the deformation of the reinforced steel street pole in comparison to the unprotected street pole conducted by [PERSON] et al. [1], a small street pole deformation reduction of 2.0-4.0% is achieved when using TDM thicknesses of 15-35 mm, respectively. This finding can be seen in Figure 4. However, increasing the TDM thickness further does not reduce street pole deformations, suggesting that 35 mm thickness is optim  
This finding can also be validated by viewing Figure 5, where the corner impact shown is also the same for both 35 mm thickness and 45 mm thicknesses. Figure 4: Top view of the Mises stresses of the collision with (**a**) corner collision and (**b**) frontal collision. Compared to the frontal impact, the corner impact shows that with a thickness of 15 mm, the reduction of deformation is about 2%, and at 35 mm of reinforcement, the reduction of deformation is increased to about 9%, suggesting that the TDM reinforcement acts very well against corner collisions in comparison to the frontal collisions. Since many accidents are of this nature [3], it is beneficial that TDM reinforcement mitigates the risk of causing more injury and reducing the damage to the street pole. The reason why the results of reinforcements with thicknesses of 35 mm and 45 mm are identical could occur due to the material having a declared Poisson's Ratio of 0.45, which represents incompressibility. This results in the shielding exhibiting a rigid body rather than an energy absorber, which defeats the purpose of the need for TDM shielding. The next properties analyzed are the energy absorbed by both the vehicle and the street pole during the simulation step time, which can be seen in Figures 6 and 7. The results are compared to those initially conducted by [PERSON] et al. [1] on a clean collision between the vehicle and a standalone steel street pole using both frontal and corner impact simulations. Figure 5: Street pole deformation with TDM reinforcement. (**a-d**) are deformation after a frontal collision on a street pole with thicknesses of 15, 25, 35 and 45 mm, respectively, while (**e-h**) are deformation after a corner collision on a street pole with thicknesses of 15, 25, 35 and 45 mm, respectively. Figure 6: FEA results from energy absorptions of the street pole after being collided by a vehicle (frontal collision) using five different thicknesses of TDM shielding. From viewing Figure 6, the initial reduction of impact energy on the street pole when the vehicle has collided via the frontal impact averages between 4.5 and 5.2%. This reduction increases to between 13 and 15% when the thickness of the TDM increases to about 35 mm. These readings are significant in terms of street pole structural protection as this would decrease the chances of street poles losing their structural integrity and collapsing onto the vehicle. Furthermore, this effect also reduces the risk of the street poles suffering further damage. When analyzing the impact energy mitigations on the vehicle, however, while the overall impact energy of the vehicle is decreased by 5%, the car suffers by absorbing more impact energy at thicknesses above 35 mm compared to when the car collides with the street pole with reinforcements having a thickness below 35 mm.