H82ENM Group Coursework
Title 1- Lightweight Vehicle
1
TABLE CONTENT
INTRODUCTION...................................................................................................... 3
DESIGN CONSIDERATIONS .................................................................................... 4
MATERIAL SELECTION ............................................................................................ 6
A. ADVANCED HIGH STRENGTH STEEL (AHSS) .............................................................. 6
B. MAGNESIUM ALLOY............................................................................................ 9
C. ALUMINUM FOAM ............................................................................................ 12
D. PLASTIC ....................................................................................................... 13
E. CARBON FIBER ............................................................................................... 15
F. COMPARISON................................................................................................. 16
CONCLUSION........................................................................................................ 18
APPENDIX ............................................................................................................ 19
NOTATION ............................................................................................................ 20
REFERENCE .......................................................................................................... 21
2
Introduction
As gas prices continue increasing, the social demand for more fuel-efficient vehicles become
higher.
For automotive industry, designing and manufacturing lightweight vehicle while maintain
the performance of the vehicle is still a major challenge. Besides, challenges remain in
process ability, reducing the cost of sourcing, vehicle structural integrity issues,
manufacturing, transitioning infrastructure to allow for high-scale production of lightweight
vehicles and, increasingly, reassurance about environmental impact.
In order to achieve the highest cost benefits and performance of vehicles, the combination
of materials and the design of vehicle should be taken into main considerations. It requires
never-ending research and improvement.
In this assignment, design consideration and material selection will be further discussed in
order to design a lightweight vehicle while maintain the performance of the material.
3
Design Considerations
In order to manufacture a lightweight vehicle with high fuel efficiency, there are few
significant factors that should be considered, such as materials selection, design of vehicle,
safety purposes, durability, cost, impacts to environment, and also car performance.
In automotive industry, mild-steel is still widely used in a typical five passenger vehicle
(62%) for a range of parts from simple small brackets to complicated shapes like
wheelhouses and floor-pans because of their excellent formability (Mild Steels, 2009). The
low-carbon content found in these mild steels will perform well with typical automotive
welding techniques, but the relatively low yield strength, as compared to other steels, may
limit its usefulness where dent resistance is important. Hence, high-strength steels (HSS)
and advanced high-strength steels (AHSS) should be considered for crash-sensitive parts
because they perform better with respect to crash energy management. Due to its
versatility and low cost, low-carbon steel is an effective material for most automotive
applications (Ussteel.com, 2012).
Besides, steels in the HSLA (High Strength Low Alloy) also widely used in automotive
industry (34%) (Horvath, 2004). The steels in the HSLA range are suitable for structural
parts such as suspension systems, reinforcements, cross members, longitudinal beams,
chassis components, etc. The mechanical properties of hot rolled HSLA steels and their
excellent cold forming performance and low-temperature brittle fracture resistance support
cost-effective solutions for many parts and sub-assemblies for which weight, thickness and
size reduction are sought, such as chassis components, wheels, slide rails and cross
members. (Automotive.arcelormittal.com, 2010)
For safety purposes, Krupitzer admitted lightweight cars could have safety risks in crash
scenarios but the steel industry has been able to engineer solutions that pass all the
existing tests. High strength steel (HSS) is the material that used to manufacture a vehicle
due to its good performance in side-impact and rollover situations. However, different
assertions had been made by aluminum industry. Aluminum industry claims that the size
and strength of a vehicle’s front and back end crumple zone can be increased by using
automotive aluminum. Aluminum has the potential to absorb the kinetic energy which is
caused by crash impact without increasing the overall vehicle’s weight.
4
Durability and stiffness of a vehicle can be enhanced by an automotive metal bonding
applications. Structural bonding signifies permanent and stable bonding which increase the
overall efficiency of a joined structure. The materials which are being used for current
automotive metal bonding application are epoxy adhesives due to its various advantageous
characteristics such as durability and outstanding mechanical characteristics. Structural
bonding has advantages such as joining non-weldable components and materials, joins
metallic and non-metallic substrates to avoid galvanic corrosion. The general performance
which caused by structural bonding are increasing the static stiffness by 8-15% or 2-3 Hz
and increase the joint durability of a vehicle.
Vehicle performance such as acceleration, braking and handling system also included in
design considerations. Lightweight materials such as high strength steel, aluminum and
carbon fiber are used to maintain or even enhance the performance of vehicle. The noise,
vibration and handling characteristics of a vehicle can be significantly improved by weight
reduction of unsprung mass. Besides that, by lowering the weight of top part of vehicle, the
centre of gravity will be lowered which decrease the risk of rollover. Improved vehicle
performance provides a marketing point beyond fuel economy improvements.
Manufacturing cost is always the primary factor limiting the adoption of materials. Typically,
steel has the cheapest price compared to other lightweight materials. Although the cost of
carbon fiber used in manufacturing a vehicle results in 2 to 10 times compared to steel, but
it greatly reduced the weight of vehicle by 50 to 60% which significantly improved the fuel
efficiency.
5
Material Selection
In order to construct great exterior of a vehicle, five materials have been suggested and
further discussed. The materials include Advanced High Strength Steel (AHSS), Magnesium
alloy, Aluminum Foam, Plastic and Carbon Fiber.
Advanced High Strength Steel (AHSS)
Advanced High Strength Steel (AHSS) is a potential material for automotive industry
because it has characteristic which is lighter, strong, produced with light life cycle impact
and decrease a vehicle’s life-long carbon footprint. The weight reduction is about 50% when
compared to mild steel and the thickness is halved without sacrificing strength. Steel with
yield strength higher than 550Mpa are generally referred as Advanced High Strength Steel
(AHSS). AHSS is most suitable to use for structural parts of car body, safety components
and chassis. Figure 1 shows that most of the mild steel will be replaced by AHSS in
automotive industry in the future.
Figure 1: Metallic material types and their usage trend in vehicle body and closure, 2007 vs.
2015 comparison. (Necati Cora and Koç, 2014)
6
Iron, which is the main element in steel alloy, is one of the most plentiful elements on the
earth’s crust and it is most extracted element in the world. Table 2 shows the comparison of
AHSS with alternative materials in terms of cost, mass reduction and materials they
replaced. Although Al, Mg and Ti surpass the AHSS in term of mass saving, however, they
have either limited formability or insufficient mechanical property matters for widespread
implementation.
Table 1: Comparison of AHSS with alternative materials in term of cost, mass
reduction and materials replaced. (Necati Cora and Koç, 2014)
Materials
Material Replaced
Mass Reduction (%)
Relative Cost (per part)
AHSS
Mild Steel
10
1
Al
Steel, Cast Iron
40 - 60
1.3 - 2
Mg
Steel or Cast Iron
60 - 75
1.5 - 2.5
Mg
Aluminum
25 - 35
1 - 1.5
Ti
Alloy Steel
40 - 55
1.5 - 10 +
Figure 2 shows that AHSS is more environmental friendly because it emits the fewer
amounts of greenhouse gases to the environment. AHSS recycling rate is near 100% makes
it a very sustainable material. (Steel.org, 2015)
Figure 2: Material GHG emissions for typical functional unit. (WorldAutoSteel,
2014)
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Table 2: The product features of AHSS with different production methods.
Products type
Hot rolled
Properties of steel
High alloy content, low weldability
Low alloy content, good mechanical property,
excellent weldability
Continuous annealed
High alloy content
Relatively low alloy content, good weldability
High alloy content, low weldability， some problems
with the profile of the steel sheet
Low alloy content, good mechanical property,
excellent weldability
Lowest alloy content, good mechanical property,
excellent weldability
Hot dip galvanized DP
High alloy content, good corrosion resistance
8
Magnesium Alloy
Magnesium alloy is a potential material for automotive industry because of its light weight
(36% lighter than Aluminum and 78% lighter than iron which is the lightest of all structural
metals). Magnesium has the highest strength-to-weight ratio compare to all the other
structural metals and it can results in a 22%-70% weight reduction from conventional steel
car. Pure magnesium must be alloyed with some other elements such as aluminum and zinc
to improve its strength, creep resistant and heat resistance due to its low mechanical
strength. Magnesium is very reactive, therefore, coatings or simply allowed it to build up a
naturally occurring oxide is needed to protect it. Table 2 shows the comparison of properties
of three materials.
Table 2: Comparison of Material Properties. (Gaines, 1996)
Properties
Magnesium
Aluminum
Iron
Crystal Structure
HCP
FCC
BCC
Density at 20oC (g/cm3)
1.74
2.70
7.86
25.20
23.60
11.70
Elastic Modulus (106 psi)
6.4
10
30
Melting Point (oC)
650
660
1536
Ultimate Tensile Strength
250
483
350
160
414
90
Coefficient of Thermal
Expansion 20-100oC (x106/oC)
(Mpa)
Yield Strength (Mpa)
Figure 3 shows the specific strength and specific stiffness of magnesium compared with
aluminum and iron. The specific stiffness of aluminum and iron is a little bit higher than
magnesium which is negligible. Besides, the specific strength of magnesium is much more
higher than iron and aluminum.
9
Figure 3:
Comparison of
basic structural properties of magnesium with aluminum and iron. (Mustafa, 2008)
Magnesium is the 8th most abundant element in the earth’s surface. Seawater is the main
supply of magnesium as it contains 0.13% Magnesium. (Gaines, 1996) The availability of
primary magnesium in combination with its recyclability makes it a very sustainable
material.
In addition, the world magnesium production is about 800,000 tons per year. Magnesium
alloy is recyclable and the energy required to melt and recycle is only about 5% of the
energy to produce same quantity of primary material. (Wang, 2010)
Figure 3: Comparison price between magnesium and aluminum price. (A.H and
A.G, 2012)
10
From figure 3, magnesium price is observed to be lower than aluminium price since 2005.
The reasonable price of magnesium will trigger the extensive use of magnesium in
automotive industry.
Magnesium alloy can be produced by several traditional methods such as forging, casting,
rolling and extruding. However, the High Pressure Die Casting (HPDC) is the most common
Magnesium alloy production method.
Table 3: Properties between different chambers in HPDC (MAGNESIUM: THE
WEIGHT SAVING OPTION, n.d.)
Hot Chamber (H.C)
Cold Chamber (C.C)
The injection system is dipped in molten
Speeds and pressures are higher can be
metal
obtained majors.
Short cycles
Prices are more compact
Necessity to fuse fine thicknesses
Huge investment
Design of pieces bounded by high
Chance of materials oxidation is high
limitations
Process is limited to a few magnesium
There are only alloys that can be injected in
alloys only
C.C.
Designing pieces with greater possibilities
11
Aluminum Foam
Metallic foams are recently being considered at as a new material for automobiles,
especially aluminium foam. Aluminium foam is a sandwich of sheet aluminium with a core of
aluminium foam. It stamped like sheet metal but is up to 50% lighter and 10 times stiffer
than steel. (Ott, 1998) The key objective of the use of metallic foams in automotive is to
increase sound dampening while decreasing the overall weight of the automobile. It also
aids to increase energy absorption in case of crashes.
In comparison to polymer foams used in automobiles, aluminium foams are stiffer, stronger,
and more energy absorbent. (Sivertsen, 2007) They are more fire resistant, and have better
weathering properties when considering UV light, humidity, and temperature. Nevertheless,
they are non-flexible and non-insulating.
Aluminum foam has cheaper cost of production if compare to conventional technology and
improved properties. Metallic foam has the remarkable potential of being a cost-effective
engineered material with improved properties. One concern during processing has been the
stability of the cell structure in terms of having uniform mechanical strength to maintain the
network of porous structure. (Laughlin and Hōno, 2014)
From environmental aspect, aluminum foam is considered more environmental friendly
since it can be remolded and reshaped for other usages. From manufacture aspect, polymer
foam is easier to produce if compare to aluminum foam. Firstly, it’s still rather difficult to
fully control the foaming process, which results in lack of uniformity of the pore structure.
Next, the manufacture of large volume foam parts is still difficult and challenging. Besides,
the manufacture cost is high mainly because of the powder prices (aluminium or aluminium
alloy powder). (Duarte and Oliveira, 2012) However, aluminium foam is still attractive to
automaker due to its high potential in reducing the weight of automotive and its high energy
absorbance.
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Plastic
The demand for plastics becomes higher in automotive industry recently because of their
good mechanical properties with excellent appearance. Plastics are considered have a high
potential in manufacturing cars more energy efficient by reducing weight, together with
providing durability, toughness, design flexibility, corrosion resistance, resiliency and high
performance at lower cost. (Szeteiová, 2008)
Plastics are used in body and exterior of vehicle from bumpers to body panels, laminated
safety glass to rear parking assists. Among plastics, polycarbonate (PC), polypropylene
(PP), acrylonitrile-butadiene-styrene (ABS) and polyethylene (PE) are commonly applied in
exterior of automotive.
Table 4: Characteristics and Applications of PC, PP, ABS and PE (Szeteiová, 2008)
Plastics
Description
Polycarbonate
PC has good weather and UV resistance, with transparency levels
(PC)
almost good as acrylic.
Applications: security screens, aircraft panels, bumpers, spectacle
lenses, headlamp lenses
Polypropylene
PP is extremely chemically resistant and almost completely impervious
(PP)
to water.
Application: automotive bumpers
Acrylonitrile-
ABS - resistant to weather. It is a rigid plastic with rubber like
butadiene-
characteristics, which gives it good impact resistance.
styrene (ABS)
Application: car dashboards, covers
Polyethylene
PE has good chemical resistance. Two types of PE are commonly used,
(PE)
low density polyethylene (LDPE) and high density polyethylene
(HDPE) can be manufactured in a range 30 of densities.
13
Application: glass reinforced for car bodies, packaging, where
strength and aesthetics are important
Even though their widespread use, the natural resources needed to produce automotive
plastics represent just 0.3% of global oil consumption. At the same time, the weight savings
in automotive are significant – approximately 100kg of plastics in a modern car replaces
200 to 300kg of traditional materials. While all other factors are being equal, the fuel
consumption in the average car is decreasing by 750 litres over a life span of 150 000km.
Additional calculations represent the reduction of oil consumption by 12 million tonnes and
thus CO2 by 30 million tonnes per year in Western Europe. (ASSOCIATION OF PLASTICS
MANUFACTURERS IN EUROPE, 1999)
14
Carbon Fiber
Carbon fiber is basically very thin strands of carbon -- even thinner than human hair which
contains 80% to 95% of carbon. To permanent shape carbon fiber, it should be undergoes
molding and coating with plastic to form carbon-fiber reinforced plastic (CFRP). (Deaton,
2010)
Carbon fiber is a super strong material which having extremely lightweight. It is attractive
to automotive industry because it's 5 times as strong as steel, 2 times as stiff, and would
reduce the weight of most cars by 60% if replacing steel components with carbon fiber (USA
TODAY, 2005). That 60% drop in weight would reduce car's fuel consumption by 30% and
cut greenhouse gas and other emissions by 10 to 20% (Web.ornl.gov, 2000) even without
changing the car's engine. On the safety issue, computer crash simulations show that
carbon fiber cars perform just as well as steel cars (Deaton, 2010). With a lighter carbon
fiber body, automakers could build cars with smaller, more efficient engines, or replacing
with electric engines, resulting in even more fuel savings.
The problem is that carbon-fiber composites cost at least 20 times as much as steel, and
the automobile industry is not interested in using them until the price of carbon fiber drops
from $8 to $5 (and preferably $3) a pound (Web.ornl.gov, 2000). Production of carbon
fibers is too expensive and slow due to the high energy needed in thermal pyrolysis to
convert polyacrylonitrile (PAN) precursor to carbon fibers. Besides, large ovens and other
capital equipment required in the process also contribute to the high cost. In the auto
industry, the use of carbon composites has been limited to racecars, high-end performance
vehicles and some high-end luxury vehicles. As a result, carbon-fiber composites cannot
compete economically with steel in the auto industry. (Deaton, 2010)
The second barrier is waste disposal. Steel can be melted and used for another construction
usage when a car breaks down. Carbon fiber can't be melted down and it's hard to recycle.
Furthermore, the recycled carbon fiber isn't as strong as it was before recycling and even
not strong enough to be used in building another car. Hence, although the used of carbon
fiber in automotive industry would save fuel, but it could also generate a lot of waste.
(Deaton, 2010)
15
Comparison
In order to select the most suitable material in the manufacturing of lightweight vehicle, comparison between the 5 selected
materials had been done in term of specific modulus, ultimate tensile strength, yield strength and cost.
Table 5: Comparison between the five selected materials (Matweb.com)
AHSS
Magnesium Alloy
Aluminum Foam
Plastic
Carbon Fiber
Crystal Structure
BCC
HCP
FCC
-
-
Density at 25oC (kg/m3)
7800
1810
400
950-1650
1790
Elastic Modulus (Gpa)
190 - 210
44.8
1.3
2.3-4.8
241
Ultimate Tensile Strength (Mpa)
550 - 1882
250
483
44-64
4280
550
160
414
23.4-69.7
200
2.44-2.69*107
2.48*104
3.25*106
1.39-5.05*106
1.35*108
$0.35-$0.40
$1.70-$2.00
$0.90-$1.00
$1.20-1.40
$5.00-$8.00
Properties
Yield Strength (Mpa)
Specific Modulus
Cost ($/pound)
16
From the result from Table 5, Advanced High Strength Steel (AHSS) and carbon fiber are
the most potential materials in the future automotive industry in order to manufacture
lightweight vehicle. Both of the AHSS car and Carbon Fiber car have the excellent result in
terms of safety, weight reduction, fuel efficiency and also car performance. In order to
choose the most suitable material, a further comparison in term of durability, cost and
impacts to environment had been discussed.
Carbon fiber has the highest specific modulus among the five, which means that carbon
fiber is the strongest materials. However, carbon fiber is relatively expensive if compare to
other materials and it’s hard to recycle which may induce to large amount of waste disposal.
On the other hand, AHSS is the second strongest material among the five while the cost is
about 10 times lower if compare to carbon fiber. When a vehicle breaks down, the AHSS
part can be remolded, reshaped and reused in another construction project.
Hence, Advanced High Strength Steel is the most potential material in the future lightweight
automotive industry.
17
Conclusion
The materials proposed are some of the potential materials for the production of future
lightweight vehicles after some research has been done. The usage of lightweight materials
is only acceptable when their mechanical characteristics such as stiffness, stability and
temperature resistance are much better than the conventional steel. Therefore, continuous
efforts on design consideration and materials selection are crucial to achieve the increasing
safety regulations, mass reduction and fuel economy targets. Further research and
development on these materials are very important for the future automotive industry to
replace the conventional steel material with higher strength materials without increasing the
weight of the vehicle. Most importantly, the right materials need to be used at the right
place of the car body. Aside from physical and chemical properties like weight and cost, the
availability, quality, recyclability and sustainability of the materials are also important to
ensure bright future of future automotive industry.
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Appendix
Specific Modulus =
Young Modulus
Density
AHSS:
Specific Modulus =
190000000000
= 2.44 ∗ 107
7800
Specific Modulus =
210000000000
= 2.69 ∗ 107
7800
Specific Modulus =
44800000000
= 2.48 ∗ 104
1810
Specific Modulus =
1300000000
= 3.25 ∗ 106
400
Specific Modulus =
4800000000
= 5.05 ∗ 106
950
Specific Modulus =
2300000000
= 1.39 ∗ 106
1650
Magnesium:
Aluminum Foam:
Plastic:
Carbon Fiber:
Specific Modulus =
241000000000
= 1.35 ∗ 108
1790
19
Notation
AHSS - Advanced High Strength Steel
HSS – High Strength Steel
HSLA - High Strength Low Alloy
CFRP – Carbon Fiber Reinforced Plastic
HPDC - High Pressure Die Casting
BCC – Body Centered Cubic
FCC – Face Centered Cubic
HCP - Hexagonal Close Packed
PC - Polycarbonate
PP - Polypropylene
ABS - Acrylonitrile-butadiene-styrene
PE - Polyethylene
Mg - Magnesium
Al - Aluminum
Ti - Titanium
CO2 – Carbon Dioxide
20
Reference
1. A.H, M. and A.G, J. (2012). Magnesium and Aluminum Alloys in Automotive Industry.
Bangi: Universiti Kebangsaan Malaysia.
2. Automotive.arcelormittal.com, (2010). ArcelorMittal Automotive Worldwide. [online]
Available at: http://automotive.arcelormittal.com/europe/products/HYTSS/HSLA/EN
[Accessed 17 Apr. 2015].
3. Deaton, J. (2010). What Is Carbon Fiber? - HowStuffWorks. [online] HowStuffWorks.
Available at: http://auto.howstuffworks.com/fuel-efficiency/fuel-economy/carbonfiber-oil-crisis1.htm [Accessed 17 Apr. 2015].
4. Efunda.com, (2015). eFunda: Typical Properties of Steels. [online] Available at:
http://www.efunda.com/materials/alloys/alloy_home/steels_properties.cfm
[Accessed 12 Apr. 2015].
5. Gaines, L. (1996). Potential automotive uses of wrought magnesium alloys.
[Argonne, IL]: Argonne National Laboratory.
6. Horvath, C. (2004). The Future Revolution in Automotive High Strength Steel Usage.
1st ed. [ebook] General Motors Corporation. Available at:
https://www.steel.org/~/media/Files/Autosteel/Great%20Designs%20in%20Steel/G
DIS%202004/16%20%20The%20Future%20Revolution%20in%20Automotive%20AHSS%20Usage.pdf
[Accessed 18 Apr. 2015].
7. MAGNESIUM: THE WEIGHT SAVING OPTION. (n.d.). [online] 9(F2008SC031).
Available at: http://www.fisita.com/students/congress/sc08papers/f2008sc031.pdf
[Accessed 11 Apr. 2015].
8. Mild Steels. (2009). 1st ed. [ebook] Arcelor Mittal. Available at:
http://automotive.arcelormittal.com/repository/Automotive_Product%20offer/MildSt
eels.pdf [Accessed 17 Apr. 2015].
9. Necati Cora, Ö. and Koç, M. (2014). PROMISES AND PROBLEMS OF
ULTRA/ADVANCED HIGH STRENGTH STEEL (U/AHSS) UTILIZATION IN AUTOMOTIVE
INDUSTRY. [online] Available at: http://www.otekon.org/bildiriler/B238.pdf
[Accessed 12 Apr. 2015].
10. Plastic-A MATERIAL OF CHOICE FOR THE AUTOMOTIVE INDUSTRY. (1999). 1st ed.
[ebook] ASSOCIATION OF PLASTICS MANUFACTURERS IN EUROPE. Available at:
http://www.resol.com.br/textos/Plastics,%20a%20material%20of%20choice%20for
%20the%20automotive%20industry.pdf [Accessed 16 Apr. 2015].
11. Rmi.org, (2015). Comparison of carbon fiber vs steel manufacturing costs. [online]
Available at: http://www.rmi.org/RFGraph-carbonfiber_vs_steel_manufacturing
[Accessed 30 March. 2015].
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12. Steel.org, (2015). Sustainability: Life Cycle - Automobiles | AISI - American Iron &
Steel Institute. [online] Available at:
https://www.steel.org/Sustainability/Life%20Cycle%20Information/Automobiles.asp
x [Accessed 12 Apr. 2015].
13. Szeteiová, I. (2008). AUTOMOTIVE MATERIALS PLASTICS IN AUTOMOTIVE MARKETS
TODAY. 1st ed. [ebook] Slovak Republic. Available at:
http://www.mtf.stuba.sk/docs/internetovy_casopis/2010/3/szeteiova.pdf [Accessed
16 Apr. 2015].
14. USA TODAY, (2005). Carbon fiber sparkles with diamond like appeal. [online]
Available at: http://usatoday30.usatoday.com/money/autos/2005-07-25-carbonfiber-usat_x.htm [Accessed 17 Apr. 2015].
15. Ussteel.com, (2012). Low-Carbon. [online] Available at:
https://www.ussteel.com/uss/portal/home/markets/automotive/Low-Carbon /
[Accessed 17 Apr. 2015].
16. Wang, b. (2010). Next Big Future: Steel, Aluminum and Carbon Fiber. [online]
Nextbigfuture.com. Available at: http://nextbigfuture.com/2010/10/steel-aluminumand-carbon-fiber.html [Accessed 11 Apr. 2015].
17. Web.ornl.gov, (2000). ORNL Review: Carbon-Fiber Composites for Cars. [online]
Available at: http://web.ornl.gov/info/ornlreview/v33_3_00/carbon.htm [Accessed
17 Apr. 2015].
18. WorldAutoSteel, (2014). Advanced High-Strength Steels Application Guidelines
Version 5.0. [online] Available at:
http://www.worldautosteel.org/download_files/AHSS%20Guidelines%20V5/AHSS_G
uidelines_V5.0_20140514.pdf [Accessed 12 Apr. 2015].
19. Xiaodong, Z., Zhaohui, M. and Li, W. (n.d.). Current Status of Advanced High
Strength Steel for Auto-making and its Development in Baosteel. [online] Available
at: http://www.baosteel.com/english_n/e07technical_n/021702e.pdf [Accessed 12
Apr. 2015].
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