Looking at the lightweight design of the car from the Audi A8 "contrast weight gain"

As the luxury flagship sedan of Audi, the Audi A8 has been brought to the world with its all-aluminum space frame structure (ASF), permanent full-time four-wheel drive quattro and low-key luxury appearance since its inception in 1994. Surprise. The Audi A8 is now available in 2009. After the competitors Mercedes-Benz S-Class and BMW 7-Series launched a new generation of models, Audi officially announced that the new Audi A8 will be held on July 11th in Barcelona, ​​Spain. Officially released at the summit, it will be equipped with a new automatic driving assistance system. The new A8 is also expected to be unveiled at the Frankfurt Motor Show in September and will be available for sale at the end of the year. What kind of surprise will the new Audi A8 bring this time?

The information that Audi has revealed recently has brought us more surprises and surprises than surprises. It is understood that the new Audi A8 has revolutionized and upgraded Audi's all-aluminum space frame structure (ASF) technology, abandoning the all-aluminum body that Audi has always been proud of. The proportion of aluminum alloy is reduced to 58%, but the body is Compared with the current model, the weight gain is nearly 51 kg, which is increased from 236 kg of the current A8 model to 282 kg. It is understood that the new Audi A8 pays more attention to the hybrid application of lightweight materials. The core of its research and development is no longer only concerned with the proportion of aluminum profiles, but about how to mix and match a variety of materials. Under the current development trend of automobile lightweighting, what inspiration does the Audi A8 “thickening weight gain” bring to the lightweight design of automobiles?

Bionics combination of various lightweight materials in body structure

Audi's all-aluminum space frame-type body structure (ASF) technology follows the principle of bionics and is inspired by natural animals. By optimizing the frame structure, it applies ultra-high-strength materials and non-load-bearing parts to light-weight materials in key parts. To achieve the goal of lightweighting the entire vehicle. As a pioneer in the field of lightweight body, Audi has been researching lightweight technology since the late 1980s. The Audi V8 was the prototype of the Audi body lightweight application. With the further improvement in the requirements for rigidity and collision safety of the car body, the Audi A8 series has developed from the all-aluminum body of the first generation Audi A8 in 1994 to the design of 8% steel in the body material. This time, the application of the new Audi A8 aluminum alloy was further reduced to 58%. In addition to high-strength steel, more composite materials were added to the body materials.

Schematic diagram of the new generation Audi A8 body structure material

The new Audi A8 is constructed of aluminum alloy material to ensure the structural strength. Aluminum castings are used at key joints, and aluminum sheet metal parts are used on the body surface. In the body cockpit cage structure, a large number of thermoformed ultra-high-strength alloy steels are used, far more than the application of the A8 high-strength steel on the B-pillar. The high-strength steel material has an increased rigidity compared with the steel 20 years ago. Double, the weight is reduced by 40%. Magnesium alloy is added to the body structure, and CFRP carbon fiber composite material is used at the rear of the car to reduce the weight of the car body from the rear wall and other details.

It is worth mentioning that in the BMW i3 and BMW 7 Series, the carbon fiber composite material is mainly used for the frame unit or the frame core, while the new generation Audi A8 mainly uses the carbon fiber composite material in the rear and tail boxes of the vehicle. Partition. The carbon fiber separator is composed of 6 to 19 layers of carbon fiber cloth stacked in a criss-cross manner according to the texture of the carbon fiber, and is used to respectively correspond to stresses in different directions at the rear of the vehicle body. The advanced point is that the carbon fiber cloth is not required to be impregnated with epoxy resin. , the finished carbon fiber parts can be cured within a few minutes. Audi said that only this very light carbon fiber component has contributed a 33% share of the A8's increased torsional rigidity. The importance is self-evident. Another highlight is the use of magnesium alloys. The magnesium alloy is used on the triangular reinforcing frame connecting the top of the suspension in the engine compartment, and is fixed on the top of the pillar by aluminum alloy bolts, which plays the role of "top bar". Audi engineers said that the magnesium alloy support rod can reduce the weight by 28%, and the weight reduction effect is also very magical.

Overall, the new Audi A8 has a weight of 282Kg, which is much more than the 231Kg of the fourth-generation model. However, the body has been strengthened a lot, and the high-strength steel content in key structural parts has been further increased, making the body resistant. The torsional strength is 24% higher than the current A8, meeting the more stringent emission regulations, electrification, comfort, noise and crash testing requirements, and the safety and handling of the vehicle has been greatly improved. The content of aluminum alloy material reached 58%, and it still won in terms of weight reduction compared with the BMW 7 series with carbon fiber material. Comprehensive comparison, the new Audi A8's lightweight level is actually a substantial improvement.

Aluminum alloy dominated body structure has become a trend in lightweight technology

Similar to the Audi A8 aluminum alloy vehicle architecture, the ModelS, developed and manufactured by Tesla, a globally pure electric vehicle manufacturer in the world, also uses an all-aluminum body. In addition to the body, most of the Tesla front and rear suspensions are made of aluminum. Because the battery capacity and weight of the electric car are almost proportional, in order to ensure the battery life, the weight of the battery accounts for a large part of the weight of the whole vehicle, so it is very important to effectively reduce the weight of the car body. Tesla's battery is very heavy, and it must compensate for the shortage of heavy batteries by reducing the weight of the body. The all-aluminum body has both lightweight and high-strength characteristics, which makes up for this demand. It can also be seen that exploring the application of weight reduction technology in the field of electric vehicles is also an important direction for the development of lightweight vehicles in the future.

Tesla electric car with all-aluminum body

Similar all-aluminum body structure design, also appeared in the new generation of Rolls-Royce Phantom models that will be unveiled at the end of this year. This model is based on the BMW Group's new aluminum body platform, and the quality of the kerb will be greatly reduced. The new Land Rover Range Rover, which will be launched in the third quarter of this year, has a new car body with an aluminum content of 81%. The recently launched Lincoln Navigator has also adopted an all-aluminum body. The rigidity of the vehicle has been improved while significantly reducing the total weight of the vehicle. The vehicle's power and fuel economy have been effectively improved.

All-aluminum technology is mainly used in luxury brands due to its high cost, and is rarely seen among joint venture brands and independent brands. In addition to the above mentioned Audi A8, Tesla, Land Rover Range Rover and other models, from the global perspective, the most thorough application of all-aluminum technology is the Jaguar brand from the United Kingdom, the most mature technology, aluminum The output of alloy cars is also the largest. In April 2016, the Chery Jaguar Land Rover all-aluminum body production line in Changshu, Jiangsu Province was officially put into operation, becoming the first domestic auto industry to be able to manufacture all-aluminum body, the first domestically produced car known for its 75% aluminum alloy application ratio. The new Jaguar XFL is off the assembly line.

Compared with the models that only fully aluminize the body panels, the weight reduction effect of the all-aluminum body-in-white is more obvious, but due to its difficulty in manufacturing and higher cost, the body-in-white of most medium and large luxury cars on the market. The material is mainly made of steel-based aluminum alloy, and Jaguar XFL has always insisted on using aluminum alloy as the main material.

It is understood that the Jaguar XFL all-aluminum body solution comes from the local supplier Novelis Changzhou factory. The RC5754 high-strength aluminum alloy developed by Novelis has a yield of 105-145 Mpa and a tensile strength of 220 Mpa. It has excellent properties in terms of strength, corrosion resistance, jointability and formability. It is used in Jaguar XFL. Multiple body structure parts. For example, AC600 aluminum alloy is applied to the body reinforcement, AC300 aluminum alloy is applied to the anti-collision beam structure, AC170 aluminum alloy is applied to the outer plate edge and side cover, etc., which helps the Jaguar XFL achieve high strength, high torsion resistance and lightness. Quantitative superior performance.

Compared with the traditional body, the all-aluminum body structure is lighter and more sturdy, which is convenient for modular design. The body has more space to configure complex technology and the products are more diversified. In addition to the Jaguar XFL, the proportion of aluminum for the body-in-white of the Cadillac CT6 produced by SAIC Motor has reached 62%. At the same time, many independent brands such as SAIC, BAIC and BYD are also increasingly using aluminum panels. It can be speculated that with the development of the domestic automobile manufacturing industry, the future vehicle structure will be dominated by aluminum alloys, supplemented by high-strength steel, magnesium alloy and carbon fiber composite materials, which will become the most important solution for automobile lightweighting.

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(Editor: HN666)