Lightweight technology and application of the hott

Automobile lightweight technology and application

automobile lightweight plays a vital role in reducing fuel consumption and emissions, and has become a research hotspot in the automotive industry at home and abroad. Automobile lightweight mainly adopts the combination of material lightweight and structure lightweight, and various advanced forming technologies of automobile parts are also one of the core contents of lightweight

the concept of automobile lightweight

automobile lightweight is a complete concept, which means that the weight of the automobile is purposefully reduced on the premise that the original driving safety, crashworthiness, seismic resistance and comfort are not reduced, and the cost of the automobile is not increased. Automobile lightweight is the integration of advantages of design, materials and advanced processing and forming technology, as shown in Figure 1. It can be seen that the automobile lightweight is actually a system engineering combining the four aspects of automobile performance improvement, weight reduction, structure optimization and reasonable price

Figure 1 Schematic diagram of automobile lightweight structure

the test shows that for every 10% reduction in vehicle mass, the fuel consumption decreases by 6%~8% and the emission decreases by 4%. At the same time, there are some small problems in the use of automobile lightweight. You can directly improve the specific power of the automobile through self inspection and maintenance, so as to improve the dynamic performance of the automobile. Therefore, automobile lightweight technology is one of the important technical measures to effectively reduce fuel consumption, reduce emissions and improve safety

the core content of automobile lightweight

at present, the main content of automobile lightweight includes the combination of material lightweight, design lightweight and structure lightweight

material lightweight

(1) that is, the vehicle body is lightweight through the replacement materials of steel plate or light metal materials. The replacement materials are high-strength steel plate instead of ordinary low-carbon cold-rolled steel plate to improve the strength and stiffness of parts and reduce the thickness or section size of steel plate to reduce the weight. High strength steel plate is superior to ordinary low-carbon cold rolled steel plate in terms of basic mechanical properties, cold stamping into shape, bake hardening, dent resistance, welding, fatigue strength, corrosion resistance and appearance quality. At present, figure 2 shows the use of high-strength steel plates in the body of the new generation of Suzuki Alto mini cars in China.

the proportion of high-strength steel in the body of international mainstream models has generally reached more than 70%. Figure 2 shows the use of high-strength steel plates in the body of the new generation of Suzuki Alto mini cars in Japan. In recent years, domestic automobile manufacturers have gradually adopted high-strength steel. For example, Chery has used dp340 high-strength steel in 45% of its newly developed models, and 50% of some models. Dongfeng Motor Corporation adopted 700 MPa high-strength steel with yield strength to replace 510 MPa material on the commercial vehicle frame. Through structural optimization, the weight of the main beam was reduced by 38kg, the weight of the reinforced beam was reduced by 170kg, the total weight was reduced by 208kg, and the cost was reduced by more than 600 yuan. In terms of the lightweight of the car body, 700MPa high-strength steel plate was used to replace Q235 to produce the standard car body, achieving a weight reduction of 20%~37%. The BIW of Geely's nl-1 model adopts high-strength steel plate, ultra-high-strength steel plate and other materials, and the weight is reduced by 36kg

Figure 2 the use of high-strength steel plates in the body of the new generation Suzuki Alto mini car in Japan

(2) light metal materials are light materials with low density and high strength, such as aluminum alloy, magnesium alloy, titanium alloy, etc. Because light metal can directly reduce the weight of parts, it has become the most direct and effective lightweight measure. Figure 3 shows the practical application of magnesium alloy parts in Dongfeng Motor. In addition, SAIC Automobile Group has lightened the weight of light metal materials for the instrument panel framework of a new model developed by SAIC. The weight of the original steel instrument panel framework is 5.545kg, and the new magnesium alloy product is 1.895kg in combination with the advanced manufacturing process, achieving a mass reduction of 65%. For the 4g18 engine developed by Geely Automobile Company, the weight of the cylinder block crankcase was reduced by 26.2kg after the original alloy cast iron was changed to aluminum alloy, the weight of the intake manifold was reduced by 2.76kg after the aluminum alloy was changed to PA66, and the materials such as exhaust manifold, cylinder head cover, timing chain cover, crankshaft and mounting bracket were improved, which reduced the weight of the whole engine assembly by 56kg

Figure 3 application of magnesium alloy parts in Dongfeng engine

(3) plastic parts replacing steel with plastics can reduce the weight of the whole vehicle and are important lightweight materials for automobile lightweight. 75% of the plastics can also be recycled, which can greatly reduce energy consumption and promote the process of environmental protection. Chery automobile uses a large number of aluminum magnesium alloys and plastic materials in the chassis system, and uses plastic materials for the pedal support, gear shifting mechanism, etc. the optimized stabilizer bar and hand brake support make the weight reduction effect reach more than 50%

structure lightweight

body structure lightweight is also called structural optimization design, that is, by adopting advanced optimization design methods and technical means, under the premise of meeting the performance requirements of body strength, stiffness, mode, crash safety, fatigue life, NVH (vibration noise), body structure manufacturability, production cost and other aspects, as well as relevant laws, regulations and standards, by optimizing body structure parameters, Improve the utilization rate of materials, remove redundant parts of components, and make components thin-walled, hollow, miniaturized and composite to reduce weight and realize lightweight. As shown in Figure 4, the new "Wulingzhiguang" series minibus jointly developed by SAIC GM Wuling and Hunan University uses advanced finite element analysis to realize the lightweight structural optimization design by changing the part thickness and structure without reducing the stiffness, strength, mode, collision, NVH and other performance indicators of the whole vehicle. The total weight is reduced by 16.71kg, saving costs and reducing fuel consumption. The lightweight design and optimization of automobile structure mainly includes:

(1) optimize the design of automobile structure through CAD, reduce the body weight and steel plate thickness, make the components thin-walled, hollow, miniaturized and composite to achieve the purpose of lightweight, and use CAE technology to calculate the automobile strength and stiffness, so as to ensure the performance of the reduced weight vehicle

(2) develop and design hollow structure with more rationalization of vehicle body and components. The main approach is to use "empty instead of solid" in the structure, that is, for the components bearing bending or torsional loads, hollow structure is used to replace solid structure, and the structural layout is optimized to make it more compact. This can not only reduce the weight, save materials, but also make full use of the strength and stiffness of materials

(3) find the best combination point between lightweight and material characteristics, processability, production batch, cost and other constraints, realize the lightweight structure of multi material combination, and emphasize that appropriate materials are used in appropriate parts. With CAD/CAE computer-aided technology, the lightweight design and optimization of structure are integrated into the early stage of development, shorten the development cycle, reduce costs, and ensure the efficiency and quality of automobile lightweight

Figure 4 Wuling Zhiguang series minibus with lightweight optimized structure

lightweight advanced forming technology

(1) at present, the main advanced forming and manufacturing technologies for high-strength steel plate include hot stamping forming, hydraulic forming, laser welding forming, high-pressure forming in pipe, etc. Thermoforming technology is widely used in the reinforcement of various automobile front and rear bumpers, security parts and collision parts with strength up to 1500MPa on foreign automobiles, making outstanding contributions to automobile lightweight and improving safety. According to relevant data, Volkswagen AG has adopted hot stamping technology for most body parts in its passatb6 model. Its typical applications are side impact bar, front and rear bumper crash beam, cross beam and side beam, a, B, C pillar reinforcement and lumbar guide rail reinforcement

in recent years, hot formed steel has also been used to varying degrees in newly developed cars in China. The number of hot formed parts used in single cars has reached more than 10, which has basically reached the international advanced level. For example, Chery's newly developed hot stamping parts include B-pillar reinforcing plate, front bumper cross beam, A-pillar reinforcing tube, door anti-collision beam, etc., which significantly improves the safety of the whole vehicle. However, due to the cost problem in the application of hot formed parts, there are still some difficulties in the application of low-end economical cars

(2) advanced forming and manufacturing technologies for light metal materials such as aluminum and magnesium alloys mainly include semi-solid forming, high vacuum die casting, isothermal extrusion, isothermal forging, etc. each forming and manufacturing technology also supplies PVC and nylon for the automotive market. Through computer simulation design, the precise and efficient forming performance of light alloys can be greatly improved, high-precision and efficient precise forming and manufacturing can be realized, and the expected material microstructure, properties and forming quality can be obtained

technical path of automobile lightweight

the implementation of automobile lightweight technology is to set engineering goals: minimum mass of automobile, axle load distribution, dynamic and static stiffness, acoustic characteristics and comfort, passive safety and compliance with regulatory objectives, service life and life cycle, etc. Based on these objectives, the following measures are adopted in the implementation of lightweight engineering:

(1) the optimal design of components mainly includes the optimal bearing path, uniform structure and optimized geometry

(2) in terms of manufacturing process, it mainly adopts laser tailor welded blanks, deep drawing parts, hydroforming and lightweight castings, advanced connection technologies such as spot welding and laser tailor welding, as well as self riveting technology and flanging connection technology of aluminum alloy plates, hot forming and hydroforming technology and rolling forming technology; Solve the forming of high-strength parts, reduce the number of parts, reduce the structural solder joints, and improve the performance of parts

(3) in terms of material technology, high-strength steel and advanced high-strength steel, aluminum alloy and magnesium alloy, composite application technology of different materials, application of fiber-reinforced composites, etc. are adopted to finally achieve the goal of the shortest development time, the lowest cost and the best cost performance of BIW

in the implementation of lightweight engineering, computer simulation is an effective means to optimize the design, which can be used to optimize the geometry and loading path to predict the formability and fatigue life, so as to reduce the trial production time and reduce the number of experiments; It can also simulate the passive safety, load path and deformation during impact, so as to optimize material selection, manufacturing process and use advanced forming technology

conclusion

automobile lightweight is of great significance to automobile fuel saving, emission reduction, performance improvement and healthy development of automobile industry. It is the development direction of modern automobile industry technology. In the lightweight design of the whole vehicle, high power output, low noise, low vibration, good handling and high reliability shall be comprehensively considered. Through the design optimization of automobile structure and shape, advanced processing technology and lightweight materials are applied to realize the weight reduction of the whole vehicle. Automobile lightweight must realize the overall design requirements on the premise of controlling the cost. Only by realizing large-scale production, the production cost of these new lightweight materials and their processing technology can meet the benefit requirements of material production enterprises

in order to improve China's automobile lightweight technology, the urgent task is to integrate the national lightweight technology advantages and carry out a large-scale combination of production, learning, research and application. Starting from the strategic height of the development of automobile lightweight technology, establish a resource sharing scientific and technological innovation platform for automobile lightweight technology, and promote the cooperation among production, learning, research and Application