Almost all cars have lines on the hood, the lowest two start, and some cars even have many lines. The function of these lines is not so mysterious. Basically, they have two purposes: shaping and strengthening. It is said that curves are the soul of painting and photography. Many things have curves, and the overall effect comes out. Without curves, it's bland. The same is true of cars, such as the one above. From the current aesthetic point of view, the front of the car is simply ugly, and the whole hood is unremarkable. At first glance, only the joints between various plates can be seen. After adding lines, the front of the car looks fuller, three-dimensional and layered. And the family-style front face design of many models echoes the hood line. For example, Lexus's big mouth net can extend up to the windshield along the hood line, which looks more atmospheric. And this BMW, the hood line echoes the iconic air intake grille. They are all optimized designs in appearance to make the car more beautiful. Just as men have muscles and women have hips, they are more attractive. The reinforcement here is not simply to increase the strength of the hood, because the hood itself does not bear any stress, so it can cover the cabin. And from a safety point of view, the engine cover should not be too hard. There are several main reasons. 1. Pedestrian protection. When a car hits a pedestrian, the upper body of the person will fall to the hood under the action of inertia. If the hood is too hard, it will cause serious harm to the human body. 2. In-vehicle occupant protection. If we pay attention, we will find that the hood of many cars with serious rear-end collisions will bend. In fact, this is also a kind of protection. There is a folding guide design in the hood, which can make the hood fold according to the pre-designed shape in case of collision, so as to prevent the hood from being inserted into the cockpit and threatening the safety of passengers. 3. Lose weight and be light. In the first sentence of the movie, D, Li Tuohai and Jing Yi, 86 went to the explosion. Tofu dad changed the engine and put on a black hood. At that time, many people wondered: how did you get a black hood? In fact, it is a carbon fiber hood to reduce reuse. Not only racing cars, all cars are trying to reduce the weight as much as possible without affecting performance and cost. Therefore, for safety and weight reduction, the hood cannot and does not need to be made so hard. After all, it is not a bulldozer. Generally, the automobile hood is a double-layer structure, the inner layer is a skeleton and collapse-oriented design (the design at the red circle in the figure, the hood will bend from here when it is hit), and the outer layer is a steel plate skin. Due to the limitation of weight and safety, the skin steel plate is very thin and the surface area of the hood is very large. If the whole steel plate is directly applied, it will inevitably bend in the middle due to gravity. Laying the wire on the steel plate and bending it at the wire can strengthen it, so that the engine cover will not be soft. This is the original intention of hood line design, do you understand?