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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
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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.
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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.
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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
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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
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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
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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.
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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
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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.
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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, %
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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
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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
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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, %
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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).
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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
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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
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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
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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.
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