Recently, a hot topic without nutrition has caused heated discussions among car enthusiasts, and there is no need to talk about it if you want to see the title; Now let's popularize a knowledge point, that is, the type and strength of "body covering".
According to the "whether to load", the body structure can be roughly divided into two categories, specifically:
Load-bearing, the corresponding model is a narrow passenger car.
Non-load-bearing, the corresponding models are generalized passenger cars and various types of commercial vehicles.
Passenger cars in the narrow sense refer to sedans, SUVs and MPVs, and strictly speaking, they do not include off-road vehicles; Because the abbreviation of off-road vehicle is ORV, which refers to off-road vehicle, which is different from the concept of sport utility vehicle (SUV), which is a sport utility vehicle. In a broad sense, passenger cars have cross-type passenger cars, which can be understood as dual-use passenger and cargo vehicles, such as mini-faces and light buses, and may also include pickup truck models in the future. Commercial vehicles refer to all kinds of trucks and medium and large buses, such models, some light buses and all off-road vehicles use non-load-bearing bodies, and vice versa.
Let's talk about the non-load-bearing architecture first, which has six major assemblies.
Chassis. Bodywork.
Motor. Transmission.
Steering machine. Suspension system.
The so-called chassis here refers to a complete and independent chassis, which is a set of frame chassis made of a combination of ordinary strength, high strength and some ultra-high strength steel, with high overall torsional strength and strong bearing capacity; The remaining five assemblies are fixed on the chassis, so the chassis is the "bone" of the non-load-bearing body, the engine is equivalent to the heart, the transmission is equivalent to the neural network, the steering is equivalent to the sensory system, the suspension system is equivalent to the limbs, and the body is only equivalent to the muscles and **.
The reason why off-road vehicles use non-load-bearing architecture is that the high-strength chassis will not be easily deformed, and the body frame will not be easily deformed. The reason why commercial vehicles use the same type of architecture is because of the strong load-bearing capacity of the independent chassis.
There are only five major assemblies in the load-bearing body, and there is no "independent chassis".
This architecture only retains the body, engine, transmission, steering and suspension system, so what about the chassis? Don't worry, the load-bearing chassis is the steel plate under the body frame, and the horizontal and longitudinal convex parts are the reinforced structure.
Obviously, without the load-bearing structure of the high-strength chassis, its torsional strength is obviously not high enough.
But fortunately, cars, SUVs and MPVs will not be taken off-road, nor will they be heavy-loaded, so even if the strength is not high, they can meet the normal use; However, this knowledge point is not the focus of the matter, the point is that you need to know that the remaining four assemblies have no place to fix, so they can only be fixed on the body - so the body of the load-bearing body should have higher strength, and the body plays a role in the non-load-bearing structure on the basis of muscles and **, and it must play the role of bones on the basis of the load-bearing structure.
The body includes: the internal frame.
Covers. The load-bearing body is like a birdcage, a b c d column, top beam, side beam, main and auxiliary frames, these structures are equivalent to bones and muscles, but it will be ugly without **, so it is necessary to "cover parts".
The so-called covering parts are actually exterior parts or decorative parts, which are to make the body look good and reduce the existence of the vehicle's drag coefficient; Therefore, the covering does not need to be very strong, and the standard of the materials used does not need to be very high. At the same time, automobiles also need to be lightweight to reduce fuel or electricity consumption, and covering parts are an important part of lightweighting.
Types of overlays include:
Armor plate. Engineering plastics.
FRP. The main body parts of most cars, such as the hood, doors, roof, and tail box covers, are steel plates, but the thickness is only about 1mm (mm); One millimeter is the thickness of the nail cover, so the covering is actually very fragile, and a slight scratch may also touch it! And because the area of the cover is too large, it can be easily pressed and deformed. In order to prevent large areas of covering pieces from being easily deformed, vehicles are often designed with "stiffeners", that is, various raised lines; However, it is not surprising that the area without stiffeners can still be crushed or smashed to deform, any car can be used.
The front and rear bumpers of the car must not be made of metal, and the material used must be engineering plastics, unless it is a supercar, which may use carbon fiber; Engineering plastics are used to reduce the weight of the car body, but also to take into account the pedestrian collision protection factor. The strength of engineering plastics is very low, and the toughness is also average, so they can be easily pulled or compressed, and it may crack when kicked at low temperatures.
The last material is fiberglass, with "steel" in the name, but it is not steel.
The full name of FRP is "glass fiber reinforced plastic", which is also a plastic material, and its strength is slightly higher than that of engineering plastics used in bumpers; Its use in automobiles is generally used as a body covering, and individual car companies will build anti-collision beams, but the role is almost none.
FRP is basically broken when touched on the car, so why use FRP?
The reason is that it can further strengthen the weight reduction, and the second is to reduce the maintenance cost! Individual off-road vehicles will use FRP as a covering part or all of the body, and a small number of micro electric vehicles are also used. Take off-road vehicles as an example, they need to work outdoors for a long time, and bumps and bumps are commonplace. If the body is damaged, it will have to be painted in sheet metal, and the cost of its maintenance cycle will be relatively high; If it encounters the degree that it cannot be repaired, the only way to replace the assembly is relatively high, and even the welding position of the covering and the body has to be cut.
On the contrary, the use of FRP is directly replaced when it is damaged, the material cost is low, and the labor cost is also low, so there will be off-road vehicles using FRP.
Conclusion: The body cover of the car is always very fragile, even the steel plate only plays a role in diversion and beauty, so don't try to smash the cover, some naughty children like to stand on other people's cars, but I don't know how distressed the owner will be. Although the engineering plastic of the bumper is fragile but will not shatter in a slight collision, the FRP material is the opposite, so it is necessary to be cautious in the process of using the car and try to avoid bumps.
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