## 3 Methodology
### FEA Model  
For the project to meet the regulative standards of car collisions, two types of collisions had to be modeled using the Abaqus/Explicit FEA solver: front and corner. Figure 5 highlights the images for each of the simulations. Initially, the CAD model of the car, discussed in Section 3.1, was imported as a deformable shell with an overall thickness of 2.5 mm to reflect the thickness of industry standard vehicles. The material of the shell was of an aluminum grade, Aluminum-5052, which is primarily used for sheet metal of car exteriors. However, the internal component of the vehicle was composed of a stronger Aluminum-6061 alloy. The reason why this specific grade was chosen is because unlike the vehicle's shell, the internal component of the vehicle contains highly dynamic components such as pistons, gears, and shafts. There are other static parts such as the vehicle's chassis, engine casings, and transmission casing that are usually made up of stronger aluminum alloys and should be accounted for in this model. Thus, the Al-6061 grade was chosen as it can withstand higher stresses than Al-5052 before yielding. The simulations involving steel-based street poles has been assigned with ASTM A36 grade properties while Aluminum-6061, as discussed previously, is also used for the aluminum-based street poles. To ensure that the impact simulation behaves as realistically as possible, the material definitions also include damage properties. Both the car and the street pole have been defined using ductile damage. The reason why ductile damage is used is because damage in metals such as aluminum and steel propagate from two mechanisms--either through nucleation or propagation of an initial damage, or through excessive shear damages (Dassault Systemes [17]). To accurately extract initial damage, the critical fracture strain of each metal is required. To model the  
Figure 4: Dimensions of the street pole’s geometry. Figure 3: Side and underneath views of the vehicle assembly. propagation of damage, the damage evolution for each specimen is also needed. According to Dassault Systemes [17], to ensure accurate damage evolution, mesh element sizing must be optimal as the accuracy of the damage evolution depends on the material's mechanical characteristics and the size of each mesh element. Finally, as the simulation requires the explicit dynamics solver, the densities of the three materials are required. All properties of the three materials are shown in Figure 6 as well as in Tables 1 and 2. Figure 5: Images representing the assembly placement of the vehicle and the street pole as the initial increment. Figure 6: Stress–strain curves of the three materials used in the simulation for the purpose of accurately calibrating their plastic properties. Frictionless interaction has been declared throughout the simulation. This was chosen as the dynamics (magnitude of velocity), and the scale of the model was large enough to not consider friction as a source for major deviation of results. Moreover, to reduce computation time, the surface pair between the reinforcement bar and the engine component was a tie surface, as the interaction between these two pairs were not of particular interest. Only two boundary conditions were added--the street pole was completely fixed on the bottom end of its geometry to represent ground reaction effects and the velocity of the car just before impacting the street pole. The frontal crash model involves the vehicle traveling head-on towards the street pole at three different speeds: 12, 17, and 22 m\(\cdot\)s\({}^{-1}\). The corner crash model also travels head-on at these same speeds. The simulation was performed using the Abaqus/Explicit solver with no mass scaling needed as the total time of the simulation to finish computing results was about 20 min per simulation.