Crush Zone and Cage Structure:
Crush zones are parts of a unibody construction that are deliberately weakened for forces in a certain direction by using more easily deformable materials than in other parts of the chassis. The crush zones include, for example, the trunk or the front around the engine compartment. In the event of a collision, the area in the crush zone will crush in a certain predetermined way.
The force exerted on the entire body will then be partially absorbed in the deformed materials. Also, the deceleration will be lessened, as the time that the crush zone is collapsing effectively slows the vehicle down. This allows the collision to be absorbed as much as possible, protecting the occupants.
A so-called cage structure is placed around the interior where the occupants are located. The materials in this part of the body are so strong that the cage structure will hardly deform even in severe collisions. In the event of accidents and rollovers, the occupants are protected as much as possible against being trapped.
The following image shows a crash test of a VW Touran, which clearly shows how the crush zone absorbs the frontal collision and the material around the occupants is hardly deformed.
In vehicles that did not yet have a cage structure, the body around the interior will deform too easily. An example can be seen in the next image, where a VW Transporter T3 undergoes a crash test.
Body Materials:
To achieve a crush zone and cage structure, a mix of materials that are either easily deformable or very difficult to deform is used in building the car. The image below shows the cohesion of different types of materials.
- The steel parts of the cage structure are indicated in red. These parts must be as strong as possible to protect the occupants in a collision;
- We also find extra strong steel in the rear doors;
- Around the engine compartment and the trunk, a mix of strong steel and medium-strong steel is used. These parts will deform easily in a collision, thus creating the crush zone;
- Finally, we see an aluminum bumper beam, which deforms most easily in a collision and may provide protection to a pedestrian or cyclist;
- In the interior, we see a magnesium component. This can be a mounting bracket for the center console. This body part is not subjected to stress, so it is made as light as possible.
Crash Test:
Manufacturers are required to have new vehicles safety tested through crash tests. The vehicle is tested in all conceivable scenarios.
The data obtained from this indicates that the body and safety systems can protect the vehicle’s occupants and pedestrians from injury during a collision. Important results include the deformations of the body, the steering column, the protection around the child seat, etc. So-called crash test dummies are placed in the car to simulate the human body.
Crash tests are recorded by cameras for analytical purposes. In addition to the human eye, the computer also analyzes the footage. This is then used to create a crash simulation: with the computer, one can analyze the deformation of materials in even more detail.
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