[YesAuto Safety Technology] The thicker the steel plate, the safer it is. It seems that this “theory” has been deeply rooted in the hearts of most people. However, what we want to say today is that the current car is actually more like a “soft egg” because it is being designed and developed. At this stage, we have planned in advance how to correctly “injury” in a collision. The only purpose is to improve passive safety, so let's talk about why the car is “soft”? And where is the “soft”?
Some time ago, we conducted a questionnaire survey on steel plate thickness and safety. More than 40% of the people believed that steel plate thickness is not directly related to collision safety. Today we further discuss collision safety and tell you The thicker the steel plate does not mean the higher the safety, and even the “soft” part of the structure can make the car safer.
● What! ? The first “soft” is not a Japanese car but a Mercedes-Benz?
For the car, an industrial product made of steel, it has always been considered that the harder the safer, so many people question the safety of Japanese cars. Words such as “soft” and “unbearable” are often used to describe some Japanese brands, but through professional crash test centers such as E-NCAP, C-NCAP, IIHS, etc., let us know that the collapsible energy-absorbing design of the body structure greatly improves the crash safety, which means that it is reasonable ” “Soft” is safe. Did the Japanese brand pioneer the design concept of collision energy absorption?
Bila Barnyi was born in a prestigious family of military officers in Hungary. The good family environment allowed him to complete his studies in the Department of Mechanical and Electrical Engineering of the University of Vienna. What makes the family proud is that Bila Barnyi has more than 2,000 patents in his lifetime. , This number is twice the number of Edison invention patents .
He divided the car body into three parts. The passenger compartment is made of more rigid materials to ensure that it will not be deformed in the event of a collision as much as possible. The two areas before and after the passenger compartment are buffers that can be collapsed and deformed to absorb the collision. The energy of time. In 1959, Mercedes-Benz applied this design to the third-generation Mercedes-Benz S-Class (W111), making it the first model in history with a crash energy-absorbing design.
Based on the concept of Bila Baenyi, subsequent collision safety technology has continued to develop. This concept of “overcoming rigidity with softness” has been applied to the structural design of all parts of the car. Through different material design and structural design, the car can complete multiple collapse and energy-absorbing actions at the moment of a collision. Let's break down this moment to see which parts of the car absorb energy as the car is gradually squashed.
●The first layer of protection-bumper
When it comes to collision safety, perhaps the first thing we think of is the bumper. That's right. Generally speaking, the bumper is the first to bear the impact force in a collision accident. Friends who know classic cars must know that the bumpers of early cars were made of metal, so why are they now made of plastic?
If there is no bumper, then the vehicle may be damaged due to some minor collisions to more important parts such as lights, heat dissipation tanks, and the maintenance cost will be correspondingly high, so we can not cancel it directly because of the high damage to pedestrians. Bumpers are gradually evolving and developing through structural optimization and material improvement.
It can be said that plastic bumpers mainly play an energy-absorbing role in minor collisions with lower speeds or accidents with pedestrians. If the accident is more serious, how can the greater collision energy be absorbed?
● “Energy Absorption Dafa”-Anti-collision beam and energy absorption box
After the early forms of bumpers gradually turned into plastic exterior parts, in fact, cars also evolved the design of anti-collision beams and energy-absorbing boxes behind the bumpers. For general low-to-medium-speed collision accidents, they can well dissolve the collision energy and protect the main body structure.
An energy-absorbing box is generally added at the connection between the anti-collision beam and the longitudinal beam of the car body. The ordinary energy-absorbing box is also made of steel plate. The steel plate will be punched with grooves or holes to induce deformation. Another method is to design it into The variable cross-section energy absorbing box, under the action of the impact force, the energy absorbing box can collapse and deform in a pre-designed form to optimize the absorption of energy.
Generally speaking, the front and rear anti-collision beams of the car will appear in conjunction with the energy-absorbing box. The anti-collision beam is stronger than the energy-absorbing box. This is to more evenly distribute the impact force to the energy-absorbing beam during a collision. The longitudinal beams on the left and right sides of the car body enhance passive safety.
-Is a car without an anti-collision beam unsafe?
When it comes to collision safety, many friends are particularly concerned about whether the car has a rear anti-collision beam. They think that it is not safe without an anti-collision beam. In fact, this conclusion is not accurate, because this problem needs to be divided into two situations: One situation is that the car did not have a rear anti-collision beam from the beginning of the design, and the effect of the anti-collision steel beam can be achieved to a certain extent through the design of the body structure (such as strengthening the structure of the rear part of the body), so it cannot be generalized. It is said that their safety is not as good as that of models with anti-collision beams, or even models with anti-collision steel beams. If the design of the steel beams is unreasonable, the effect may be useless. Another situation is that a model is designed at the beginning of the design. The rear anti-collision beam, but it was omitted in the later period, and the body structure was not strengthened correspondingly after the omission, so it must have an impact on the collision safety.
Energy is absorbed through the principle of structural deformation. The essence is to convert the kinetic energy at the moment of a collision into internal energy (usually manifested in the temperature increase of the body parts after the collision). If the energy of the collision is too large, the deformation of the body parts cannot be completely absorbed. do? Therefore, in order to ensure the safety of the passenger compartment while the body is crumpled and deformed, there will also be a passive safety design that guides energy transfer.
In fact, many things in life are not stronger and stronger. In many cases, when the overall strength is required, reducing the local strength of the object is not a convenient design case, such as the pre-fracture of biscuits. Design, zigzag design of food packaging bags, etc.
In fact, the design of the overall structural strength of the car body also embodies the idea of guiding energy transmission, relying on the “softness” of some structures to guide and absorb the impact energy during a collision, so that the structure of the passenger compartment of the car will not be deformed as much as possible to ensure the occupants in the car. Security.
● Induced fracture design of engine compartment cover
When a vehicle collides with a pedestrian, the protection of the pedestrian’s head is more dependent on the design of the engine compartment cover, which is that the part of the pedestrian that has more contact with the body will undergo corresponding strength and structural optimization, so that the pedestrian’s head can be Better cushioning effect. In addition, more importantly, the engine compartment cover generally has a design that induces breaking.
● Engine sinking design
The engine sinking design can also be regarded as a typical case of guiding energy transfer. First of all, the engine sinking design is not to let the engine fall during a collision, but to induce this “iron bump” to follow a certain line during the collision through the structural design. It sinks to the lower part of the passenger compartment to ensure the living space of the passenger compartment.
When the vehicle is hit from the front, the engine is very easy to move backwards and squeeze into the passenger compartment. The life safety of the driver and passengers will be greatly challenged. Therefore, the supporting parts of the engine of the current vehicle are generally designed to have a guiding effect. In the event of a collision, the engine is guided to the lower part of the passenger compartment to increase the possibility of survival of the driver and occupant in the accident.
● Crumbling and breaking design of central drive shaft
Directing the engine as a whole to the lower part of the passenger compartment will inevitably drive the transmission system. Therefore, for the four-wheel drive model, how to make the central transmission shaft also collapse and break? On the central drive shaft provided by GKN, we have seen a collision energy absorption solution.
In addition to absorbing energy through the collapse of the drive shaft, many manufacturers also choose to induce the drive shaft to break to improve collision safety, and at the same time, it will not affect the sinking design of the engine.
●The steering column collapsed and fractured design
Steering system components such as the steering wheel and steering column play an indispensable steering function during vehicle driving. However, it may also play a killer role in a collision. Because when the vehicle is severely impacted, the driver's body will often lean forward due to the huge deceleration, and the head or chest will collide with the steering wheel.
In addition to the protection of the airbag, the steering column in the steering system is actually unique. It can collapse and deform according to the pre-design, reducing the collision energy transmitted to the driver to a minimum. There are generally two ways to absorb energy in the steering column, one is through the expansion and contraction of the steering column, and the other is through breaking and deforming.
In terms of passive safety, the collapse of the steering column can not only absorb part of the energy, but more importantly, it can also prevent the steering column from deflecting to the left or right during a collision, causing the airbag on the steering wheel to pop up. Changes affect the protective effect of the airbag on the driver.
● “Break = safety”-accelerator pedal broken design
I believe that when you see the words “accelerator pedal broken”, perhaps everyone first thinks of the dangerous scene of the car losing control, but on the contrary, the accelerator pedal broken design is for the protection of personal safety in a collision accident. .
The fracture of the accelerator pedal is mainly due to the protection of the driver's legs during the collision. When a collision occurs, if the driver's foot is still on the accelerator pedal, then the huge impact force will be transmitted to the calf through the accelerator pedal, causing leg injuries. And if the accelerator pedal will break under a certain force during a collision, cutting off the transmission of the impact force can well protect the driver.
In order to avoid the occurrence of dangerous accidents when the accelerator pedal breaks during normal driving, the upper limit of the force when it breaks must be reasonably designed, and the country also recommends corresponding industry standards in this regard.
In addition to seat belts and airbags, a large part of the passive safety design is actually due to the collapse and breaking of the body structure, such as the anti-collision beams, energy-absorbing boxes, engine compartment covers, and central drive shafts we mentioned. And so on all reflect this design concept. Almost all of these typical energy-absorbing designs are available in most current automobiles. Of course, with the development of material science, I believe we can find more energy-absorbing parts in automobiles in the future. This is just like the Chinese martial arts philosophy of “Using softness to overcome rigidity” since ancient times. The automobile also uses its own “softness” to make the body structure reasonably induce deformation and fracture under the action of impact force. It is precisely because of this “softness” that it can be in a collision. Better protect the drivers and passengers in the car. Therefore, I believe that when we refer to the harder and safer topics in the future, we will have our own correct judgments in our hearts. (Car home text/picture Xia Zhimeng, some pictures are from the Internet)