The document discusses reducing the weight and cost of vehicle suspensions through the use of advanced materials. It analyzes several material options for replacing traditional steel, including carbon fiber composites, aluminum, magnesium, and titanium alloys. These materials can significantly reduce vehicle weight but also have drawbacks like higher costs, joining challenges, and limited availability. The document also examines the development of advanced high-strength steels, including dual-phase steels that offer improved strength and ductility over conventional steels. Overall, using lightweight materials allows vehicles to carry additional safety and emissions equipment without increasing overall weight.

1. WEIGHT&COST REDUCTION OF
SUSPENSION VEHICLE
AIM : to decrease the weight and cost of a suspension vehicle by the materials
being used in it.
Materials used : carbon-fiber reinforced plastics(CFRP), glassreinforced plastics
(GRP), high performanceplastics, high strength steels, aluminuium, magnesium,
advanced composite materials,
Description : Reducing weight has become one of the hottest topics in the
automotivemanufacturing sector, driven largelybytheneed to reduceemissions to
suit ever-decreasing targets. Body and drivetrain have come under intense scrutiny
in the endeavour to save weight and an array of innovative concepts have been
developed over recent years to achieve it.
Advanced materials are essential for boosting the fuel economy of modern
automobileswhile maintainingsafetyand performance.Becauseit takes less energy
to accelerate a lighter object than a heavier one, lightweight materials offer great
potential for increasing vehicle efficiency. A 10% reduction in vehicle weight can
result in a 6 to 8 percent fuel economy improvement. Replacing traditional steel
componentswith lightweightmaterialssuch ashigh-strengthsteel, magnesium (Mg)
alloys, aluminum (Al) alloys, carbon fiber, and polymer composites can directly
reducethe weightof a vehicle’s bodyand chassisby up to 50percent, and therefore
reduce a vehicle’s fuel consumption. Using lightweight components and high-
efficiency engines enabled by advanced materials
By using lightweightstructuralmaterials, automobilescancarryadditionaladvanced
emission controlsystems, safety devices, and integrated electronic systems without
increasing the overall weight of the vehicle. While any vehicle can use lightweight
materials, they are especially important for hybrid electric, plug-in hybrid electric,
and electric vehicles. Using lightweight materials in these vehicles can offset the
weight of power systems such as batteries and electric motors, improving the
efficiencyand increasing their all-electric range. Alternatively, the useof lightweight

2. materialscould resultin needing a smaller and lower-costbatterywhile keeping the
all-electric range of plug-in vehicles constant.
Pros and cons of materials for weight and cost
reduction
ADVANCED HIGH-STRENGTH STEEL
Stronger and moreductile than typical steel, advanced high-strength steel could
reducecomponentweight by up to 25 percent, particularlyin strength-limited
designs such as pillars and door rings. It is generally compatiblewith existing
manufacturing and materialscurrentlyused in vehicles.
Pros: High strength, stiffness, formability, and corrosion performance, aswell as
low cost.
Cons: High cost, and wears out stamping moldsfaster than for lesser grades.
Ductility decreases as strength increases, adding issues in forming and joining.
Challenges also include design, componentprocessing, and behavior in harsh
environments.
ALUMINUM
Because of aluminum’suse in aerospaceand construction, scientists have a good
understanding of its characteristics and processing. Manufacturerscurrentlyuseit
in vehicle hoods, panels, and powertrain components, butfacebarriersin cost and
manufacturing. Manufacturersalso faceissues with joining, corrosion, repair, and
recycling when they combine aluminum with other materials. A lighter, more
expensive alternative to steel, aluminum is increasingly being utilized for hoods,
trunklids, and doors, and has the potential to reduce weight by up to 60 percent.
Pros: Technologyisfairly mature; good stiffness, strength, and energyabsorption.
Cons: Higher costthan steel, joining to other materials, and limited formability
issues.

3. MAGNESIUM
With the lowest density of all structuralmetals, magnesium alloys have the
potential to reducecomponentby weight up to 70 percent. Magnesium is
presently used in castings for power-trainsor sub-assembly closures. The increased
use of magnesium for automotive applicationsis limited by several technical
challenges. Even though magnesium (Mg) can reducecomponentweight by more
than 60 percent, its use is currentlylimited to less than 1 percent of the average
vehicle by weight. Although incorporation of multiple, individuallycast, or wrought
Mg componentsinto articulated sub-assemblies appearsunlikely in the near-term,
Mg will continue to have a role in vehicle light weighting, predicated on its
attractive features of low density, high specific stiffness, and amenability to thin-
wall die casting and componentintegration.
Pros: High stiffnessand strength, compatible with existing infrastructurefor
stamping.
Cons: Expensive, lackof availability from U.S. manufacturersin largequantities to
meet automotiveneeds. Other challenges include ductility, joining, repair,
recycling, and corrosion. Rareearth additives may also be needed to improve
energy absorption to meet crash requirements.
CARBON FIBER COMPOSITES
While manufacturersusecarbon fiber in high-performancevehicles, the expense
of the inputmaterial and process to develop it are generallytoo high for use in
popular models. Despite being half the weight of steel, carbon fiber composites
are four times stronger and have the potential to reducevehicle weight by up to
70 percent.
Pros: High stiffness, high strength, enables the manufactureof highlycomplex
shapes, and offerstremendous weight savings.
Cons: High production costof carbon fiber and difficultyjoining into vehicles, along
with associated challenges in modeling performance, infrastructure, and sufficient
amountsof fiber to meet automotive needs.

4. TITANIUM
This high-temperaturemetal is used in powertrain systems to reduce weight by up
to 55 percent. Titanium is also used in valves, springs, suspensions, wheels, and
gearbox housings.
Pros: High strength-to-weightratio, can withstand high temperatures.
Cons: High costof materials, and formabilitychallenges.
Development of AHSS

5. Steels of currentinterest involve novel alloying and processing combinationsto
produceuniquemicrostructuralcombinationsand havebeen referred to by a
variety of identifiers, including dual-phase(DP), transformation-induced plasticity
(TRIP), high-strength low-alloy(HSLA), complex-phase(CP), twinning-induced
plasticity (TWIP), and martensitic steels. The propertiesof these multiphase steels
are derived from appropriatecombinationsof strengthening mechanisms
HistoricalAHSS developments
effects on the mechanical properties of a conventional HSLA steel of inter critical
annealing (where the metal is heated to between its lower and upper critical
temperatures to allow partial transformation of the matrix into austenite) followed
byquenching.Thedata shown arefora plain-carbonsteel, an HSLAsteel (SAE980X),
and the same HSLA steel after inter critical annealing and quenching to produce a
DPsteel (referredto asGM 980X).In contrastto theHSLA steel, theDP steelexhibits
continuousyielding and a significantincreasein elongationwith essentially thesame
ultimate tensile strength.
The combination of continuousyielding with maintained or improved ductility
generated significant interest and extensive research on DP steels. One important
finding was the contribution of retained austenite to the deformation behavior of
DP steels. Specifically, it was observed that DP steels contain retained austenite
and the ductility of DP steels increases with increasing content of retained
austenite. These findingsform the basis on which new developments in AHSS for
automotive applications, particularlyTRIP steels, arebased.
The first-generation AHSS conceptswere developed in fairlydilute compositions
and are primarilyferritic-based multiphasemicrostructures. DP steels arecurrently
the most applied AHSS gradesin the automotive industry. Interest in DP steels
results from improved strength and formability, good weldability, relative ease of
processing, and availability.
Enhanced-strength/enhanced-elongationcombinationsareclearlyobtained for
TRIP steel grades, where strain-induced transformation of retained austenite into
martensite results in increased strain hardening. The second-generation advanced
high-strength steels clearly exhibit superior mechanical properties, but these
austenitic grades are highly alloyed, resulting in a significant cost increase. In

6. addition, industrial processing of these alloys, specifically the TWIP steels with high
manganesecontents, has proven to be extremely challenging, and the TWIP grades
have also been shown to be prone to delayed cracking.
Recent research indicates that the embrittlement susceptibility can be reduced
by aluminum alloying, although the exact mechanism involved is still under
investigation. From it is clear that a property gap exists between the currently
available AHSS grades of the first and second generations and defines a property
band for future third-generation AHSS. Currentresearch is hence focused on filling
this property window using modified or novel processing routes where special
attention should naturally also be given to industrial feasibility and cost
effectiveness.