Side Impact

After frontal impact, lateral and oblique side impact collisions are the second most common cause of serious motor vehicle accidents. Side impact collisions differ from frontal impacts in that there is direct interaction of the occupant with the vehicle structure. It is not uncommon for the door of a car to be pushed more than two feet (0.5 m) into the vehicle interior.
With the adoption of side impact protection standards in both the United States and Europe, vehicle side structures have been beefed up quite a bit compared to previous generation vehicles. To further cushion the blow of a side impact collision more and more car makers are introducing side impact airbags. These deploy inbetween the occupant and the vehicle structure to increase the duration of the contact and lower the peak forces acting on the occupants. Thorax Bag
Side Impact The industry makes extensive use of computer analysis during the development of a new vehicle for both structural improvements as well as for the development of side airbags. These models range from coarse beam models in the early stages of development to detailed Finite Element models in the latter stages. The coarser model allows analysis of the overall kinematics of the impact as well as the relative velocities of the door and the occupant.
This gives design guidelines for the structure of the vehicle and padding needed to protect the occupant. This then helps to build the model for the more detailed study. Finite element models of both the dummy and the door structure are used to study the interaction. These analyses are of a complex nature as they involve large plastic deformations as well as foam paddings that have complex non-linear material properties.
The effects of the various changes are studied by looking at the resulting dummy injury measures. Rib acceleration, thoracic viscous injury level, and pelvis acceleration are all indicators of the risk of serious injury. If the car maker is not satisfied with the injury mitigation level that can be achieved with structural improvements alone, he may decide to add a side airbag to the list of standard equipment.
FEM door
Side Impact Sled The development of the side airbag starts on the computer as well and then propagates to sub system testing on a sled. Different types of side airbags can be analyzed for their protective characteristics. Some provide only cushioning in the area of the vulnerable ribs, others include head protection as well. To reduce the risk that the deploying side airbag induces injuries to the occupant, the deployment is in general aimed away from the normal seating position. Side airbags are not nearly as large and as powerful as the frontal airbags. Nevertheless, extensive testing with out-of-position adult and child dummies is necessary to ensure minimal risk of induced injuries.

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