Finite Element model

The vehicle finite element model used to simulate the side impact was the Ford Taurus model developed by NCAC and available online at http://www.ncac.gwu.edu/vml/models.html. Two different versions of this vehicle model were available: a very detailed model (about 1 million elements) and a simpler model (about elements). As in this case the impact was limited to a restricted portion of the vehicle (i.e., the rear right door and pillar), it was decided to use the reduced version of the Taurus vehicle model with some refinement of the mesh in the area where the impact occurred. In particular, the size of the shell elements of the door was reduced in order to obtain a correct modeling of the contact forces between respectively the dummy and the internal side of the door and the mailbox and the external side of the door (Figure 1). Also, as in the original vehicle model it was not present, the rear seat was modeled from scratch and added to the model.

Original door model Refined door model

Figure 1. Original door mesh and refined mesh for the Taurus model.

The model of the side impact dummy was obtained from LSTC. As this model originally represented a 50 th

percentile male dummy, it was scaled down to reach the actual dimensions and weight of Ms. Cory Cumming (Figure 2).

50th percentile ScaledFigure 2. Original 50th percentile and scaled dummy model.

The dummy was positioned on the right hand side of the rear seat, tilted towards the door (). Considering that the car laterally hit a curb on the right side before impacting the mailbox, this position most likely represent the

actual position of Ms. Cory Cumming during the accident. The dummy was also restrained with a typical three point seatbelt found on the rear seat of most cars.

Figure 3. Initial position of the dummy model .

The mailbox was modeled from scratch and represented the geometry of actual mailbox involved in the accident. In order to model exactly the same height of the impact point in the actual accident, it was decided to place the mailbox model 80 mm above the surface level at which the car model was placed at the beginning of the simulation. The base of the mailbox was rigidly constrained to the ground. This model was referred as ‘Original design’.

The proposed improved design of the mailbox with the legs positioned on the outside edges was modeled in a similar manner. This model was referred as ‘Modified design’.

Figure 4 and Figure 5 show the impact scenario using respectively the original and modified mailbox models. In both cases the vehicle initial velocity was 35 km/h and the mailbox was positioned in front of the car rear pillar.

Figure 4. Impact scenario for the ‘Original design’.

Figure 5. Impact scenario for the ‘Modified design’.

Head acceleration (Original design in red)

Head contact force (Original design in red) - Filtered @ SAE 60

HIC severity index (36 msec)

Original design

No filter SAE 1000 SAE 180HIC 1551 1557 1274HIC (d) 1336 1341 1127t1 67.22 67.24 66.64t2 68.28 68.28 68.74dt 1.999e-005 1.999e-005 1.999e-005Average acc. 292.5 295.1 205.7

Modified design

No filter SAE 1000 SAE 180HIC 405.2 406.3 405.2HIC (d) 472.1 473 472.1t1 58.08 58.16 58.08t2 77.22 77.22 77.22dt 1.999e-005 1.999e-005 1.999e-005Average acc. 53.74 53.89 53.74

Original Design

Modified Design