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Automotive lightweighting is not merely about reducing the weight of a car; rather, it constitutes a comprehensive systems engineering approach. It involves, under the premise of ensuring the strength and safety performance of the vehicle, minimizing the curb weight as much as possible. This, in turn, enhances the vehicle’s range, energy efficiency, performance, and safety, while simultaneously reducing air pollution and contributing to the achievement of “carbon neutrality.”
Range Capability: Although electric vehicles lack an engine and gearbox, the current weight of the battery pack exceeds that of the engine and gearbox. The range of an electric vehicle is directly influenced by the weight of the vehicle. Through lightweighting design, automakers can optimize the layout of power battery modules, thereby reducing the overall vehicle weight, extending the battery range, and further enhancing the competitiveness of electric vehicles.
Energy Efficiency: A lighter vehicle weight translates to reduced energy consumption. Lightweighting electric vehicles helps improve energy utilization efficiency, lower operating costs, and further decrease dependence on finite resources.
Performance and Safety: Electric vehicle lightweighting not only enhances the acceleration performance but also contributes to improved braking efficiency and handling stability. Additionally, a lightweight structure aids in reducing collision energy absorption, lowering the risk of injury to both the vehicle and passengers.
Reducing Air Pollution: Carbon emissions from cars are typically influenced by factors such as the overall vehicle weight, fuel economy, and regional policies. Therefore, lightweighting electric vehicles is a crucial means of reducing carbon dioxide emissions. As automotive lightweighting, electrification, and intelligent technologies advance in the future, the overall carbon emissions throughout the lifecycle of a car will decrease.
1. Lightweight Application of Materials
1. Lightweight Application of Materials
Traditionally, automobiles predominantly use steel as the primary raw material, accounting for approximately 70% of the composition. Optimizing the performance of steel, enhancing its strength, and judiciously reducing thickness can effectively reduce vehicle weight. Currently, the use of high-strength steel significantly improves the durability, deformation impact resistance, and passive safety performance of automobiles. In addition to this, the market has seen the development of alternative materials such as aluminium alloys, magnesium alloys, carbon fibre composite materials, and plastics, all of which are ideal for lightweighting.
Aluminium Alloys and Magnesium Alloys: Compared to traditional steel, aluminium alloys and magnesium alloys offer lighter weight with considerable strength. Aluminium alloys, with exceptional ductility and tensile strength, can be used for complex cross-sectional components, exhibiting lower consumption rates even in the event of collisions. Magnesium, with a density of 2/9 of steel and 2/3 of aluminium alloys, further reduces weight by 15%-20% on an aluminium lightweighting basis, making it the lightest metal structural material currently available. Due to their material characteristics (high strength, large stiffness, impact resistance, high recyclability, and good processing and casting performance), these alloys are commonly used in the production of body and chassis components.
Carbon Fibre Composite Materials: Reinforced plastics generally outperform fibreglass, and carbon fibre, known for its high strength and low density, significantly reduces the overall weight of the vehicle when used in the body and structure of electric cars. For instance, when applied to the engine hood, it can reduce the weight by more than 6 kg.
Plastics: Plastics, with a relatively low density, light weight, good strength, and diverse appearances, are widely used in both interior and exterior automotive components, such as interior decorations, bumpers, and engine cooling fans. They play a crucial role in reducing body weight and lowering costs.
2. Lightweight Structural Design
The structure of electric vehicles is complex and diverse. To achieve lightweight structural design, industry engineers conduct optimization studies on various aspects, including body, chassis, battery pack casing, pedals, seats, and more. Different optimization methods are employed for different components, with mainstream approaches including size optimization, shape optimization, topology optimization, and integration optimization.
Size Optimization: Size optimization involves optimizing cross-sectional areas and thickness while ensuring the overall performance of structural components.
Shape Optimization: This refers to optimizing the shape of structural components and holes to achieve better material efficiency and reduce uneven force distribution.
Topology Optimization: Topology optimization divides the design area based on the orientation relationship between structural components and adjacent components. Without causing interference with other parts, it establishes a target function based on mechanical performance parameters under constraint conditions. Ultimately, it provides the optimal distribution of materials and the best transmission pathways, making it one of the most promising methods for lightweighting.
Integration Optimization: By integrating different functions into a single component, it is possible to reduce connection points and the number of components, thereby lowering the overall vehicle weight.
In the battery pack casing, corresponding thickness reductions can be made to the stamped materials used in the structure. When combined with external ribs for assembly, this simplifies the structural characteristics of the battery pack, reduces weight, and enhances the sealing and reliability of the battery pack. However, this battery assembly lacks an effective battery thermal management system, which may compromise performance in extreme environmental conditions. The “skateboard” battery pack design is a classic example, where the battery pack integrates seamlessly with the vehicle’s underbody, significantly saving space. Additionally, the vehicle’s frame provides protection for the battery pack, making this design structure a primary trend in electric vehicle battery pack design.
3. Lightweight Manufacturing Processes
Utilizing advanced manufacturing processes such as laser welding, hydraulic forming, hot stamping, and integrated die-casting can produce lighter and higher-strength components.
Laser Welding: Laser welding is a highly precise method capable of achieving high-quality welding on small-sized and intricately shaped components. This high precision aids in manufacturing lighter and more compact components, thereby enhancing the overall lightweighting of the vehicle. Additionally, the generated heat is relatively small, reducing the thermal impact on the surrounding areas. This helps minimize thermal deformation in the welding region, especially for components manufactured using lightweight materials like aluminium alloys, reducing the adverse effects of deformation on the overall structure.
Hydraulic Forming: Hydraulic systems, compared to traditional mechanical transmission systems, are more compact, reducing the number and weight of components. This helps lower the overall vehicle weight, improve the energy efficiency, and extend the range of electric vehicles. Hydraulic systems also possess higher power density, providing more power within a relatively small volume. This enables hydraulic systems to deliver robust driving force in electric vehicles while reducing the burden on the electric motor, contributing to lightweight design.
Hot Stamping: Hot stamping is a process of shaping metal sheets at high temperatures. This technique enables more precise shaping of metal sheets, reducing the use of excess material and aiding in the reduction of the overall vehicle weight. Additionally, it increases the formability of metal sheets, enhancing the forming limit. This allows manufacturers to design thinner and lighter components while maintaining the required strength and rigidity.
4. Battery Technology Innovation for Lightweighting
High-Energy-Density Batteries: Continuous research and development aim to create batteries with higher energy density, such as lithium-sulfur batteries and solid-state batteries, to reduce the overall weight of the battery system.
Smart Battery Management Systems: Adopting advanced battery management systems enables more precise control of the charging and discharging processes, improving battery efficiency and extending its lifespan.
In the flourishing development of the electric vehicle industry, lightweighting technologies undeniably play a key role in driving clean and efficient transportation. Through material innovation, structural optimization, advanced manufacturing processes, and battery technology innovation, electric vehicles have achieved lighter and more efficient performance, enhancing range and overall efficiency. This series of innovations not only improves the performance of electric vehicles but also lays the foundation for the future development of environmentally sustainable transportation.
