How does Intelligent Transportation systems work

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IP155_C001.fm Page 3 Monday, December 31, 2007 4:48 PM 1 Future Vehicles and Materials Technologies Kimihiro Shibata CONTENTS Introduction .............................................................................................................3 Environmental Issues.............................................................................................4 Safety.........................................................................................................................6 Intelligent Transportation Systems (ITS) ............................................................7 Market Trends .........................................................................................................8 Automotive Materials ........................................................................................... 9 Car Body Materials........................................................................................9 Materials for Engine Components............................................................10 Materials for Chassis and Powertrain Components..............................11 Future Direction of Automotive Materials..............................................11 Environmental Viewpoint ...................................................................................12 Safety Viewpoint...................................................................................................14 Summary ................................................................................................................16 References...............................................................................................................17 Introduction In the twenty-first century, cars should be designed and engineered to be in harmony with people and nature. Environmental and safety issues today call for technological improvements. Reduction of CO emissions and improvement 2 of fuel economy can be achieved together with crashworthiness through con- tributions made by material technologies. Besides improving mechanical prop- erties and cost competitiveness, peripheral technical issues, such as forming and joining technologies, and environmental performance, should be addressed prior to the deployment of a new material. Cooperation among material sup- pliers, parts suppliers and carmakers, or among carmakers themselves, in a simultaneous or concurrent manner, is becoming more important than ever. 3 IP155_C001.fm Page 4 Monday, December 31, 2007 4:48 PM 4 Automotive Engineering: Lightweight, Functional, and Novel Materials Concept of car manufacturing: Harmony of human beings, nature, and vehicles Human beings Harmonious coexistence Vehicles Nature • Environment Important technical fields • Safety • ITS FIGURE 1.1 Concept of harmonization. More than a century has passed since the automobile was invented, and the environment surrounding the automotive industry has undergone a lot of changes on countless occasions in the intervening years. Notable changes started with the introduction of mass production technology that was established for the Ford Model T series in the 1910s. After World War II, Japanese carmakers resumed passenger vehicle production and began to pursue quality improve- ments. The two oil crises in the 1970s promoted the development of low fuel consumption technologies. Following the two oil crises, stricter exhaust emis- sion regulations were enforced and intense competition to secure higher levels of performance unfolded in the early 1990s. Since the latter half of the 1990s, the focus has been on safety and environmental issues. In line with this pro- gression, the concept of harmonious coexistence, which is striking a balance among human beings, nature and vehicles, is expected to increase in importance in vehicle manufacturing in the twenty-first century. Important technology fields for achieving this harmonization are the environment, safety, and intelli- gent transportation systems (ITS), as indicated schematically in Figure 1.1. This chapter surveys the social conditions surrounding the automotive indus- try. An overview of the history of automotive materials will then be given, followed by a discussion of projected future trends in material technologies. Environmental Issues Protection of the global environment, which includes conservation of resources, is a pressing issue. Figure 1.2 shows the increase over the last 50 years in the 1 global number of vehicles. In 1950, 70 million vehicles were on the road in relation to a world population of 2.4 billion people. By 2000, the number of IP155_C001.fm Page 5 Monday, December 31, 2007 4:48 PM Future Vehicles and Materials Technologies 5 8.4 billion Global population 6.0 billion 1.4 billion Vehicles 700 million (2.4 billion) (70 million) 1950 2000 2025 FIGURE 1.2 Number of vehicles and global population. vehicles had increased to 700 million, while the world population had grown to 6 billion. In other words, the number of vehicles increased tenfold over the last 50 years of the twentieth century: It is estimated to double to 1.4 billion by 2025. With this increase in the number of vehicles, oil consumption has continued to rise, and environmental issues have become more serious. The possibility has been pointed out that global oil production might peak 2 in the year 2015 and begin to decline after that. Therefore, there are strong demands for the conservation of oil resources. Countries around the world have adopted standards that regulate the allowable levels of hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NO ) in vehicle exhaust x gas. These exhaust emission regulations will be further tightened in the future. Furthermore, carbon dioxide (CO ) in exhaust emissions has been singled out 2 as one of the causes of global warming. The Kyoto Protocol set targets for reducing CO emissions. To achieve the targets set for Europe, the United 2 States, and Japan in 2010, the CO emission level of cars with a gasoline engine 2 needs to be reduced by 6%–8% compared with 1995 models. This means that 3 their average fuel economy must be improved by 25%, as shown in Table 1.1. TABLE 1.1 3 COP3 Targets for Reducing CO Emissions and Improving Fuel Economy 2 CO Reduction 2 1 (vs. 1990) Fuel Economy Passenger car with gasoline engine: improved by 23% (by 2010 vs. 1995) 15 km/L Japan 6% Passenger car with diesel engine: improved by 15% (by 2005 vs. 1995) 12 km/L Passenger vehicle: improved by 25% Europe 8% (by 2008 vs. 1995) CO :140 g/km 2 Passenger car CAFE target: 27.5 mpg USA 7% (after 1990) (PNGP project is under way.) 1 Period: 2008–2012. IP155_C001.fm Page 6 Monday, December 31, 2007 4:48 PM 6 Automotive Engineering: Lightweight, Functional, and Novel Materials These targets were ratified in 2002, with the exception of the United States, and vigorous steps are being taken to improve vehicle fuel economy. Safety In order to improve the safety of vehicles, information safety for preventing accidents in addition to crash safety is becoming more important, as shown in Figure 1.3. In the course of developing technologies for improving crash safety, traffic accidents are reproduced and analyzed. The results of these analyses have been applied to develop new crash safety technologies, such as an automatic braking system for reducing the collision speed, and an emergency stopping system. In the area of information safety, advanced safety vehicles and advanced highway systems are being developed using sophisticated technologies like intelligent vision-sensing and car-to-car com- munication systems. In recent years, the results of car crash tests conducted under a new car assessment program (NCAP) in various countries, as well as the accident rates of individual car models, have been disclosed. Such data are usually considered in the determination of car insurance premiums. Due to stricter safety regulations and the disclosure of information regarding safety, consumers are more concerned about safety today than ever before. Based on analyses of traffic accidents, the new car assessment program will continue to adopt more precise and sophisticated collision tests. Various new car assessment tests and regulations concerning crash safety are being prepared for implementation in the coming years, as shown in Figure 1.4. Use of high technology Regulations • Intelligent vision-sensing system • Car-to-car communication Information disclosure • Use of infrastructure (NCAP, accident rates, Information insurance premium rates) safety • Advanced safety vehicles Accident Crash • Advanced highway systems safety New crash safety technologies Accident analysis & • Automatic braking system for reducing collision speed accident reproduction • Emergency stopping system FIGURE 1.3 Vehicle crash safety and information safety. IP155_C001.fm Page 7 Monday, December 31, 2007 4:48 PM Future Vehicles and Materials Technologies 7 (NCAP : New Car Assessment Program) 2000 2005 Full overlap frontal Offset frontal Pedestrian protection Side impact Overall evaluation Japan Brake performance CRS evaluation Head rest (dynamic) Roll-over avoidance Offset frontal Full overlap frontal Whiplash evaluation (dynamic) Side impact USA Enforced side impact (Offset frontal (IIHS)) Brake performance (compatibility) Full overlap frontal Brake Full overlap frontal Side impact performance Frontal (compatibility) EU Pedestrian protection Whiplash evaluation (dynamic) CRS evaluation Advanced Pedestrian airbag protection (J, EU) Safety (USA) regulations Advanced headlamps (J, US, EU) International standardization FIGURE 1.4 Trends in NCAP tests and safety regulations in Japan, the United States, and the European Union. Intelligent Transportation Systems (ITS) Intelligent transportation systems (ITS) are highway traffic systems in which smart vehicles and smart roads are integrated. These systems are expected to improve transport efficiency and safety, make driving more enjoyable, and also contribute to environmental protection, as shown in Figure 1.5. For exam- ple, CO and NO levels would be markedly reduced if the average driving 2 x Information from road Communication Smart gateway Car Road ∗ HMI HMI Driver Smart car Smart road Communication Smart gateway Information from vehicle ∗ HMI : Human-Machine Interface FIGURE 1.5 Intelligent transport systems. NCAP IP155_C001.fm Page 8 Monday, December 31, 2007 4:48 PM 8 Automotive Engineering: Lightweight, Functional, and Novel Materials 600 500 (Example for a 2000 cc (Example for a 2-ton truck) 500 passenger car) 400 400 300 23% Reduction 300 200 38% Reductio n 200 100 Avg. speed 100 Avg. speed 10 → 20 km/h 10 → 20 km/h 0 0 0 20 40 60 80 100 0 20 40 60 80 100 Average vehicle speed (km/h) Average vehicle speed (km/h) FIGURE 1.6 4 Emission levels as a function of average vehicle speed. speed during traffic congestion could be increased from 10 to 20 km/h through 4 the use of an intelligent transportation system, as shown in Figure 1.6. More- over, the number of traffic accidents might also be reduced, for example, by applying an adaptive cruise control system together with intelligent transpor- tation system capabilities. Market Trends Customer needs are becoming greatly diversified, and the speed at which they are changing is accelerating. During Japan’s bubble economy in the late 1980s, customers preferred luxurious products of a uniform style, but vehi- cles having good cost performance and individuality have been well received in recent years. Car manufacturers also have to respond to social issues. A key question is how fast a car manufacturer can provide vehicles that firstly meet customers’ demands and social requirements, and secondly are avail- able at low prices. In order to satisfy market demands, vehicle manufacturing is changing as follows: Common use of low-cost materials procured globally Use of common platforms for increasing investment efficiency and reducing development costs Outsourcing for increasing development speed These changes in vehicle manufacturing are undermining the traditional “keiretsu” system of company groupings in Japan. Today, automobile parts are assembled into modules by suppliers and provided to car manufacturers, CO emission (g/km) 2 NO emission index X IP155_C001.fm Page 9 Monday, December 31, 2007 4:48 PM Future Vehicles and Materials Technologies 9 Supplier Carmaker Supplier Primary supplier Carmaker Supplier Secondary supplier Primary supplier Carmaker Secondary supplier Supplier Supplier Carmaker Supplier Primary supplier Carmaker Secondary supplier Supplier Vertical Integration Horizontal Integration FIGURE 1.7 Alternative types of company grouping. and it is not unusual nowadays for rival carmakers to purchase parts from the same parts supplier. The traditional vertical integration of companies is changing to more horizontal integration, as indicated in Figure 1.7. This horizontal integration is basically composed of “give & take” relationships. The idea that everything should be done in-house or by “keiretsu” compa- nies has vanished. In this new structure, global networks for information, cooperation, and human resources are becoming very important elements of corporate competitiveness. Automotive Materials Figure 1.8 shows a history of automotive, mainly metal, materials. Over the years, new materials have been developed along with changes in social conditions and market requirements. Car Body Materials New materials for the car body have been developed to improve corrosion resistance and to reduce vehicle weight. In the 1950s and 1960s, mass pro- duction technologies were developed because of higher vehicle demand. High performance and reliability were also the market trends at that time. Deep drawing steel sheets with good formability were developed in the 1950s, followed by the development of anti-corrosive steel sheets in the 1960s. In the 1970s and 1980s, low fuel consumption was a keen issue because of the IP155_C001.fm Page 10 Monday, December 31, 2007 4:48 PM 10 Automotive Engineering: Lightweight, Functional, and Novel Materials Local Ozone layer MITI National Exhaust gas production protection law Oil crisis vehicle project regulation in USA/EU Recycle law 1940 1960 1970 1980 1990 Localization, High speed, Emissions, Energy High Safety, environment, Social conditions Market trends reliability mass production safety, noise savings performance diverse needs 2-layer galvanized High lubrication Deep drawing steel HSS steel sheet coated steel sheet Anti-corrosion steel Galvanized steel FRP-roof panel Urethane bumper Plastic fuel tank Body PP bumper Super olefin elastomer bumper Reinforced glass Plastic headlamp Laminated glass Al outer panel UV blocking glass Ductile iron crankshaft Oxidation catalysis Micro-alloyed steel NO storage reduction catalyst X crankshaft Metal honeycomb catalyst 3-way catalyst Al cylinder head Free cutting steel crankshaft Sinter-forged con’rod O sensor Mg head cover 2 Al cylinder block Engine Plastic intake manifold Sintered alloy valve Dumper steel Al piston Stainless steel exhaust manifold FRP head cover seat oil pan Laser clad valve seat High Si DCI Plastic air cleaner case Ceramic turbocharger exhaust manifold Plastic cylinderhead cover Al differential gear case Al wheel Micro-alloyed beam, knuckle, arm HSS suspension member Mg steering bracket Chassis Induction hardened Al steering gear Al forged upper arm knuckle arm housing Non-asbestos brake pad Al transmission case Non-asbestos clutch facing Mg transmission case Drive- Pb added free S added free Non-asbestos Anti-slip lining train cutting steel gear cutting steel gear A/T lining Composite drive shaft FIGURE 1.8 New materials used in vehicles. two oil crises. High-strength steel sheets were developed in response to this issue and have contributed to lightening vehicles by reducing sheet thick- ness. In the 1990s, safety and environmental issues became primary concerns in the automotive industry, and further work was done on developing tech- nologies for weight reductions. Aluminum alloy sheets were developed in this connection and applied to various body panels such as the engine hood, and have contributed to achieving lighter vehicles. Materials for Engine Components New materials for engines have been developed to improve engine durabil- ity and performance as well as to reduce the weight of components. In the 1950s, ductile cast iron suitable for volume production was developed and applied to crankshafts. In the 1980s, micro-alloyed steels were developed and applied to crankshafts and connecting rods. Sinter-forged connecting rods were also developed. For the sake of weight reductions, aluminum alloys were used for cylinder heads, and stainless steels for exhaust mani- folds. In the 1990s, aluminum alloys were applied to cylinder blocks, and magnesium alloys to cylinder head covers. IP155_C001.fm Page 11 Monday, December 31, 2007 4:48 PM Future Vehicles and Materials Technologies 11 90 Iron & Steel 80 70 10 9 8 7 Plastics Environmental, 6 safety Aluminum 5 considerations 4 Rubber 3 Glass 2 1 0 ’73 ’77 ’80 ’83 ’86 ’89 ’92 ’97 ’00 ’10 FIGURE 1.9 Material composition of a typical passenger vehicle. Materials for Chassis and Powertrain Components New materials for chassis and powertrain components have been developed mainly to improve durability and reduce weight. High-strength steel sheets were applied for suspension members and aluminum alloys for wheels. Knuckles, arms, and I-beams made of micro-alloyed steels were developed. Aluminum alloys are now being used for transmission cases. Gears are made of free-cutting steels. In recent years, magnesium alloys have been applied to steering system components and transmission cases. Carbon composites with fiber-reinforcement have begun to be used for propeller shafts. 3 A breakdown of the materials used in a typical passenger vehicle for the Japanese market is shown in Figure 1.9. Iron and steel still account for the largest proportion, although their percentages have been decreasing over the past 25 years. However, the volume of high-grade steel sheets, such as high-strength steels with excellent crashworthiness, and coated steel sheets with excellent anti-corrosion performance is increasing. Iron and steel are expected to remain in first place for some time to come. On the other hand, the use of aluminum alloys to make cylinder blocks, wheels, and other parts is rapidly increasing due to the demand for lighter vehicles. Aluminum alloy sheets have been applied to panels like the engine hood in recent years. This trend is expected to continue in the future. Future Direction of Automotive Materials Materials have contributed to meeting the changing requirements for vehi- cles over the years. In the future, contributions of material technologies will continue to be needed in two principal fields, the environment and safety. Proportion of materials, wt%/vehicle Proportion of iron & steel wt%/vehicle IP155_C001.fm Page 12 Monday, December 31, 2007 4:48 PM 12 Automotive Engineering: Lightweight, Functional, and Novel Materials The projected future direction of related technologies in each field is dis- cussed in the following sections. Environmental Viewpoint Issues that are important for environmental protection include reducing exhaust emissions, using clean energy, reducing pollutants, improving fuel economy, and recycling, among others. New material technologies are needed to address these issues, as shown in Figure 1.10. A diesel engine achieves better fuel economy than a gasoline engine. A direct-injection engine makes it possible to improve fuel economy further by means of lean burning. However, these two types of engine need an after- treatment system for the emission gas. A particulate filter is needed for diesel engines and an NO catalyst for direct-injection engines. There are strong x needs for the development of high-power batteries and high-performance magnets for electric motors, which will be used on vehicles equipped with a hybrid engine or with a fuel cell that is expected to be the ultimate vehicle power source with no harmful exhaust gas. Moreover, development of new materials for fuel cells is also needed. Vehicle weight savings are very effective in improving fuel economy, because the vehicle weight accounts for 30% of the total fuel consumption loss. Applying higher strength steels to body structural parts and aluminum alloys and/or plastics to body panels will make a large contribution to reducing vehicle weight. Moreover, applying higher strength materials to powertrain components will also make a large contribution to reducing the size and weight of these parts. Reducing exhaust emissions Improving fuel economy • Weight savings • Catalyst materials – HSS, Al, Mg, • Carrier materials – Plastics • Improving efficiency Using clean energy – Engine Addressing – Drivetrain • Batteries – Reduction of • Fuel cells environmental issues driving resistance Reducing pollutants Recycling • Pb, Hg-free • Reduction & consolidation of material variations • High durability FIGURE 1.10 Important issues for environmental protection. IP155_C001.fm Page 13 Monday, December 31, 2007 4:48 PM Future Vehicles and Materials Technologies 13 5000 series Al or 55 conventional 6000 series Al Property requiring consideration . 2 Dent resistance (σ t ) 0.2 50 350 MPa steel 0 150 190 260 Yield stress or 0.2% proof stress, MPa FIGURE 1.11 Reduction of outer panel weight by substituting aluminum for steel sheet. Figure 1.11 shows an example of the use of aluminum sheet for outer body panels. Dent resistance is one property that must be taken into consideration when lightening outer panels. Substituting aluminum for steel sheet would make it possible to reduce the panel weight by more than 50%. However, formability is an important factor in the extensive application of aluminum sheets to body panels. The property of dent resistance, needed for outer panels, is determined by 0.2% yield strength, as shown by the following relationship: 2 Dent resistance ∝ (σ × t ) (1.1) 0.2 where σ = 0.2% yield strength 0.2 t = sheet thickness 6000 series aluminum alloys have higher yield strengths than 5000 series alloys, and 6000 series sheet provides correspondingly larger weight savings. However, 6000 series aluminum alloys have poorer formability than 5000 series alloys, which limits the application of 6000 series alloys to body panels. The trunk lid requires a sheet with good formability, so 5000 series alloys are generally used. However, newly developed 6000 series aluminum alloys could be applied to the trunk lid, because, although yield strength is lower during the forming process, it increases after paint baking, as shown in Figure 1.12. Developments in aluminum alloy body panels and sheet are discussed in more detail by Takashi Inaba in Chapter 2. Meanwhile, different approaches are being taken to lighten vehicles through efforts to redesign the frame structure and panel parts. Audi is producing a vehicle with an all-aluminum body-in-white. In addition to changing the traditional monocoque body structure to a space frame con- struction, Audi switched the body material from steel to an aluminum alloy. This aluminum space frame structure deserves attention because of its cost- saving potential, depending on the vehicle production volume. Weight reduction, % IP155_C001.fm Page 14 Monday, December 31, 2007 4:48 PM 14 Automotive Engineering: Lightweight, Functional, and Novel Materials Conventional Newly developed 6000 series 6000 series 200 10 0.9 Conventional High- 5000 series 150 formability 0 1.0 5000 series Hood Trunk lid Better Front fenders formability required FIGURE 1.12 Trends in aluminum sheet usage for outer panels. On the other hand, magnesium alloys are being used only in small quan- tities in the automobile today. However, magnesium alloys could have a large effect on reducing vehicle weight due to their low density. Therefore, it is hoped that technologies will be developed for applying magnesium alloys to automotive components. Friction in an engine accounts for 40% of all the fuel consumption loss. There is a need to develop technologies for reducing the friction coefficient and weight of engine components, in particular the valve train and piston- crank systems, in order to contribute to improving fuel economy. Higher wear-resistant materials and surface treatments are needed for reducing load stress by lightening the weight of components and reducing the contact area. Safety Viewpoint Material technologies are also expected to contribute to improving crash- worthiness. In order to achieve a safe car body in the event of a collision, deformation of the cabin structure should be minimized to protect the occu- pants, and the collision energy should be absorbed in a short deformation length within the crushable zones, as shown in Figure 1.13. However, the reaction force generally exceeds an appropriate level when a material with higher strength is applied to an energy-absorbing location. Future trend Weight reduction rate, % Sheet thickness, mm 0.2% Proof stress after bake-hardening, MPa IP155_C001.fm Page 15 Monday, December 31, 2007 4:48 PM Future Vehicles and Materials Technologies 15 Cabin deforms significantly because crushable zone is too weak to function well as a collision energy absorber. Collision energy is not absorbed by car because crushable zone is too strong. The occupant is injured. Collision energy is well absorbed by crushable zone without any cabin deformation. The occupant is safe. FIGURE 1.13 Concept of crash safety. Consequently, new structures and materials are required for building the ideal car body that can absorb the collision energy in a short span and with a constant reaction force. To meet the requirements for improved safety, thicker steel sheets or additional reinforcements are usually applied, which leads to a heavier body-in-white. Therefore, it is necessary to improve crash safety while at the same time lightening vehicles for better environmental performance. From the viewpoint of materials, both dynamic strength and static strength are important in designing parts for greater crash safety. As defined in High dynamic/static strength ratio material Conventional material Static stress (σ ) y FIGURE 1.14 Relationship between static strength and dynamic strength. k = 1.0 Dynamic stress (kσ ) y IP155_C001.fm Page 16 Monday, December 31, 2007 4:48 PM 16 Automotive Engineering: Lightweight, Functional, and Novel Materials Average reactive force in crash deformation 3/2 . 5/3 ∝ (kσy) t 20 σ = Static yield stress y Steels with higher k-value Dynamic strength k = 15 Static strength t = Sheet thickness 10 5 Standard Conventional 0 440 590 780 Yield stress, MPa FIGURE 1.15 Part weight reductions achieved by using high-strength steel with a higher k-value. Equation 1.2, the average reactive force of a rectangular tube with a hat- shaped cross section is related to the k-value, i.e., the dynamic/static ratio 5 of yield strength : 3/2 5/3 Average reactive force in crash deformation ∝ (kσ ) × t (1.2) y where k = dynamic yield strength/static yield strength σ = static yield strength y t = sheet thickness In general, the k-value decreases with increasing strength, as shown in Figure 1.14. To reduce vehicle weight effectively while improving safety, new materials with a higher k-value are needed. For example, substituting higher strength steel for parts made of 440-MPa steel sheet can reduce the weight, but a much larger weight saving would be possible by applying steels having higher k-values, as shown in Figure 1.15. Summary This chapter has surveyed the situation surrounding the automotive indus- try, including the requirements for environmental friendliness and crash safety, from the viewpoint of the harmonious coexistence of human beings, nature, and vehicles. The discussion of the future direction of material tech- nologies has shown that various improvements can be attained by improving material characteristics. Weight saving ratio, % IP155_C001.fm Page 17 Monday, December 31, 2007 4:48 PM Future Vehicles and Materials Technologies 17 However, in order to apply a new material to a vehicle, cost competitive- ness and the availability of a global supply both need to be ensured. At the same time, peripheral technical issues such as forming and joining technolo- gies and environmental performance should also be addressed. Regarding the cost of materials, one guideline for future material selection is likely to be a specified level of cost performance from the customer’s viewpoint. Moreover, in order to overcome these technical issues, simultaneous or con- current engineering by materials suppliers, parts suppliers, and car manu- facturers, or among car manufacturers, is becoming more important than ever before. References 1. Japan Automobile Manufacturers Association, Inc. (JAMA): Japanese Automo- tive Industry, 2001 (in Japanese). 2. IEA/OECD: World Energy Outlook, 1998. 3. JAMA Web site: http://www.jama.or.jp. 4. Source: Japan Automobile Research Institute, Inc. 5. Aya, N., and K. Takahashi, Energy Absorbing Characteristics of Body Structures (Part 1), JSAE, Vol. 7, 60, 1974 (in Japanese). IP155_C001.fm Page 18 Monday, December 31, 2007 4:48 PM IP155_C002.fm Page 19 Monday, December 31, 2007 4:49 PM 2 Automobile Aluminum Sheet Takashi Inaba CONTENTS Introduction ...........................................................................................................19 Aluminum Body Panel Usage............................................................................20 Europe and North America .......................................................................20 Japan ..............................................................................................................21 Aluminum Alloys for Body Panels....................................................................22 Increasing Aluminum Body Panel Usage.........................................................24 Aluminum Alloys ........................................................................................24 Forming Technology ...................................................................................25 Recycling .......................................................................................................26 Summary ................................................................................................................27 References...............................................................................................................27 Introduction In recent years, environmental improvement and safety have become very important for the automobile industry. Environmental improvement and safety features lead to increases in car body weight. To reduce weight, there- fore, it is necessary to select optimum materials such as aluminum alloys. 1 Figure 2.1 shows the plan to reduce CO emissions in Europe. European 2 automobile manufacturers have to achieve an average CO emission target 2 2,3 of 140 g/km for their fleet of new cars to be sold in 2008. Japanese auto- mobile manufacturers have to achieve the same target by 2009. In North 1 America and Japan, automobile manufacturers also have to achieve fuel consumption regulation targets. For these reasons, aluminum alloys are essential to reduce the weight of car bodies. This chapter provides general information on how aluminum body panels are used in Europe, North America, and Japan. The promotion of increased 19 IP155_C002.fm Page 20 Monday, December 31, 2007 4:49 PM 20 Automotive Engineering: Lightweight, Functional, and Novel Materials 200 Average CO emission 2 of Japanese car in the EU Japanese car: 180 Achieve 165175 g/km 160 Japanese car: ACEA Average CO 2 Average 140 g/km 140 emission in the EU ACEA: 140 g/km (Average) 120 EU committee: 120 g/km (Target) 100 ACEA, Japanese car: 120 g/km model on EU committee: the EU market 90 g/km (Target 20152020) 80 1995 2000 2005 2010 2015 2020 Year FIGURE 2.1 Plan to reduce CO emissions in Europe. 2 aluminum body panel use and possible recycling opportunities are also discussed. Aluminum Body Panel Usage Europe and North America Aluminum body panels are used for luxury cars, popular cars, and full-size cars in Europe and North America, as shown in Table 2.1. The automobile manufacturers are mainly using only aluminum hoods except for special cases where they are making all-aluminum cars. The use of aluminum hoods is effective for both weight reduction and improved function as a hang-on part. The adoption of aluminum panels is limited at present by the complex- ity of the panel shapes, but the use of aluminum panels will increase sub- stantially in the future as automobile manufacturers strive to achieve the CO emission targets in Europe, and the fuel consumption regulation targets 2 in North America. CO Emission (g/km) 2 IP155_C002.fm Page 21 Monday, December 31, 2007 4:49 PM Automobile Aluminum Sheet 21 TABLE 2.1 Examples of Adoption of Aluminum Panels in Europe and North America Europe Benz S-class Hood Benz E-class Hood, fender, deck-lid Audi A8,A2 All-aluminum car Audi A6 Hood Volvo S60 Hood Volvo S70 Backdoor VW Lupo All-aluminum car Renault Laguna Hood Peugeot 307 Hood Citroen C5 Hood North America GM Cadillac Seville Hood GM C/K Truck Hood Ford Lincoln Hood Ford Ranger Hood Ford F150 Hood Chrysler Prowler All-aluminum car Chrysler Jeep Hood Japan The use of aluminum body parts started with the hood of the Mazda RX-7 in 1985. The Honda NSX all-aluminum car followed in 1990. At first, alu- minum body panels were adopted for parts of sport cars in Japan, but recently they have been used for mass-produced cars such as the Nissan and Subaru cars shown in Table 2.2. Aluminum body panels are also used for the compact Copen car produced by Daihatsu. TABLE 2.2 Examples of Adoption of Aluminum Panels in Japan Toyota Soarer Hood, roof, deck-lid Toyota Altezza Gita Backdoor Nissan Cedric Hood Nissan Cima Hood, deck-lid Japan Nissan Skyline Hood Honda S2000 Hood Honda Insight All-aluminum car Mazda RX7 Hood Mazda Roadster Hood Mitsubishi Lancer Evo Hood, fender Subaru Legacy Hood Subaru Imprezza Hood Daihatsu Copen Hood, roof, deck-lid IP155_C002.fm Page 22 Monday, December 31, 2007 4:49 PM 22 Automotive Engineering: Lightweight, Functional, and Novel Materials TABLE 2.3 Important Properties Required for Body Panels Panel Main Properties • High strength after paint baking (YS: 200 MPa at 170°C for 20 min after 2% strain) Outer • Flat hemming property • Surface condition (SS-mark free, anti-orange peel) • Anti-corrosion (anti-filiform corrosion) Inner • Deep drawing property • Joining properties (welding, adhesion) Aluminum Alloys for Body Panels Automobile body panels consist of a double structure with an outer panel and an inner panel. For the outer panels, higher strength materials are especially required to provide sufficient denting resistance. For the inner panels, higher deep drawing capacity materials are especially required to allow the manufacture of more complex shapes. In other words, different properties are required for the outer and inner panels, as shown in Table 2.3. Research and development of aluminum body panels began in the 1970s. Aluminum alloys for body panels developed in different ways in Europe, North America, and Japan because of the different requirements of the automobile manufacturers. In Japan, higher formability alloys were required from the automobile manufacturers. Therefore, special 5xxx series Al-Mg alloys, such as AA5022 and AA5023, were developed first. On the other hand, high strength alloys after paint baking were required in Europe and North America. Consequently, 2xxx series Al-Cu-Mg alloys, such as AA2036, and 6xxx series Al-Mg-Si-(Cu) alloys, such as AA6016, AA6111, and AA6022, were developed. The mechanism of paint bake-hardening of 6xxx series alloys is due to precipitation hardening of Mg Si or a Cu-containing deriv- 2 ative. Figure 2.2 shows the transition of aluminum alloys for body panels. Past Present and Future • Japan 5xxx 6xxx Alloy (outer/inner) (Special) 5xxx Alloy (outer/inner) (special, conventional) 6xxx 6xxx alloy • EU (Outer/inner) (Conventional) 5xxx Alloy (inner) 6xxx Alloy (outer/inner) • N.A. 6xxx FIGURE 2.2 Transition of aluminum alloys for body panels.