What are the crash protection measures for car body?

2019-11-25 11:53:12

The safety of car body is a very important problem. Many people think that the body safety is not safe, the important thing is that the body is not firm, but modern cars and designers from the perspective of mechanical research, according to different stress conditions, let part of the car body play the role of energy absorption and dispersion during collision, and try to reduce the impact force. This problem belongs to the category of vehicle passive safety performance. Today, automobile sheet metal parts manufacturers share relevant knowledge about anti-collision measures of automobile body.

The car body design mainly considers three collision resistant surfaces, namely the front and rear collision surfaces, and the other is the side collision surface. With regard to the crashworthiness of passenger cars, there are relevant laws and regulations in various countries. The task of designers is to ensure that the cars meet the relevant laws and regulations and can pass the specified crash test.

In order to ensure the safety of the passengers after the collision, at present, many front and rear parts of the car body are designed with a certain deformation area to absorb most of the impact energy and maintain the safety of the passenger compartment as much as possible.

In the vehicle collision test, the American standard is a frontal collision with an angle of plus or minus 30 degrees with the collision wall, while the European standard is a frontal collision with 40% contact. The test speed of the fixed wall collision test is 55 km / h (50 km / h for the rear collision), and the net mass of the test vehicle is 1600 kg. After the impact, the horizontal displacement of the steering wheel shall not be greater than 127 mm, and there shall be no large amount of fuel leakage. No part of the limbs of the dummy shall leave the car, and the damage of each part of the dummy shall not exceed the specified standard. In order to meet these requirements, the front of modern car body is equipped with large deformation area and high-strength bumper to bear the impact force and absorb most of the impact energy.

The rear of the car also has the same structure, but the degree of protection is not as high as the front, because the relative speed of the two cars is equal to the difference between the two cars when the rear impact occurs, while the relative speed of the front-end collision of the two cars is the sum of the two cars' speed, and the impact force produced by the two situations is greatly different.

In the design of the front and rear collision deformation area of the car, generally, some weak gaps are artificially set on the longitudinal beam. After the car collision, the longitudinal beam is impacted and squeezed, and the gap bulges and deforms or presents folding bending, so as to absorb more impact energy, so as to reduce the transmission of impact energy to the passenger compartment. There are some vehicles (such as Polo) whose front longitudinal beams are made of asymmetric cross-section longitudinal beams with thick middle and thin both ends. According to the impact force of collision energy, the material and material thickness are optimized. The front and rear panels have different material thickness at different positions, so as to achieve the effect of folding and absorbing collision energy during collision. When some vehicles collide, the front longitudinal beam and subframe will automatically disengage, the engine will sink, and the engine will not crash into the passenger compartment.

In the side impact, there is little room for the car body to allow the deformation in the impact, so we can only take measures to strengthen the collision resistance of the side wall and the door. For example, the middle section of the longitudinal beam is thickened, the transverse anti-collision beam is increased, and the rigidity of the side wall is enhanced. The transverse steel pipe is added in the door to improve the cross section shape of the column and enhance the strength of the front, middle and rear columns. In this way, the dummy in the vehicle will not be injured after the collision of the test object with a speed of 50 km / h and a mass of more than 950 kg. In an example, some cars (such as Polo) are strengthened by the side wall and door collision, which makes the total intrusion amount of the car body less when the side collision occurs, the time distribution of the intrusion speed is reasonable, and the deformation of the center pillar is even. These are necessary conditions for occupant protection when side impact occurs.