# Effect of Impact and Bearing Parameters on Bird Strike with Aero-Engine Fan Blades
## 4 Results and Discussion
### The Influence of Bird Impact Location  
The impact-location analysis comprised three locations (Cases G, L1, L2) along the fan length to study the relationship between the damage of blades and bird impact location. From Figure 8a, with the change of impact location, the maximum value of the bird's impact force also changes. The maximum bird impact force is recorded for the case of the bird impacting the blade root (390 kN), followed by the case of the bird impacting the middle of the blade. The maximum impact force recorded for the case of the bird impacting the blade tip is much lower being about half of the two other cases. This is due to the twist angle of the blade and increases in its width as the height increases, thus causing the reduction in the bird's impact force. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Case**} & **Impact** & **Impact** & **Bird Initial** & \begin{tabular}{c} **Rotational** \\ **Speed of the** \\ **Engine (rad/s)** \\ \end{tabular} & \
\begin{tabular}{c} **Support** \\ **Stiffness (N/m)** \\ \end{tabular} &
\begin{tabular}{c} **Support Damping** \\ **ing (Ns/m)** \\ \end{tabular} \\ \hline G & Middle & 0\({}^{\circ}\) & 253 & 600 & 10\({}^{8}\) & 500 \\ L1 & Root & 0\({}^{\circ}\) & 253 & 600 & 10\({}^{8}\) & 500 \\ L2 & Tip & 0\({}^{\circ}\) & 253 & 600 & 10\({}^{8}\) & 500 \\ O1 & Middle & Y-90\({}^{\circ}\) & 253 & 600 & 10\({}^{8}\) & 500 \\ O2 & Middle & Y-180\({}^{\circ}\) & 253 & 600 & 10\({}^{8}\) & 500 \\ O3 & Middle & Y-270\({}^{\circ}\) & 253 & 600 & 10\({}^{8}\) & 500 \\ O4 & Middle & Z-45\({}^{\circ}\) & 253 & 600 & 10\({}^{8}\) & 500 \\ O5 & Middle & Z-90\({}^{\circ}\) & 253 & 600 & 10\({}^{8}\) & 500 \\ O6 & Middle & Z-135\({}^{\circ}\) & 253 & 600 & 10\({}^{8}\) & 500 \\ V1 & Middle & 0\({}^{\circ}\) & 225 & 600 & 10\({}^{8}\) & 500 \\ V2 & Middle & 0\({}^{\circ}\) & 116 & 600 & 10\({}^{8}\) & 500 \\ R1 & Middle & 0\({}^{\circ}\) & 253 & 88 & 10\({}^{8}\) & 500 \\ R2 & Middle & 0\({}^{\circ}\) & 253 & 395 & 10\({}^{8}\) & 500 \\ S1 & Middle & 0\({}^{\circ}\) & 253 & 600 & \(5\times 10^{7}\) & 500 \\ S2 & Middle & 0\({}^{\circ}\) & 253 & 600 & 10\({}^{7}\) & 500 \\ D1 & Middle & 0\({}^{\circ}\) & 253 & 600 & 10\({}^{8}\) & 5000 \\ D2 & Middle & 0\({}^{\circ}\) & 253 & 600 & 10\({}^{8}\) & 10,000 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Different case studies considered for studying different parameters in the bird strike simulations. It can also be observed from Figure 8b that the kinetic energy obtained by the bird impacting the root and the middle of the blade is almost twice that obtained when the bird hits the blade tip. The maximum kinetic energy of the bird was 83 kJ when the fan lost the maximum energy. It can be seen in Figure 8c that before the bird comes into contact with the blade, the bearing force is the same for all three cases. After the bird strike, the change in the bearing forces has a lag compared to the instances the bird-blade contact start. This is due to fact that it takes some time for the force to be transferred from the blade to the bearing unit, after which it quickly rises to its maximum value. When striking the blade root, the bearing force reaches a peak value of 211 kN. Due to the different twist angles along the blade height direction, there is a large bird block impacting the blade tip at 0.0055 s in the case L2, thus generating a peak impact force. The comparison of blade-root von Mises stress is shown in Figure 8d. Bird impact does not create a big difference in the value of von Mises stress at different impact locations. The maximum stress recorded was 1164 MPa and it was for the case of a bird impacting the blade root. When the stress exceeds the yield stress, the blade deforms and fails, which  
Figure 8: Variations of (**a**) contact force; (**b**) bird kinetic energy; (**c**) bearing force; and (**d**) von Mises stress with respect to time for different impact locations. makes the whole system prone to danger.