amif2014 – [automotive] pankaj mallick, materiali attuali e futuri per automobili leggere
DESCRIPTION
Advanced Materials International Forum, Bari 18-19 settembre, conferenza internazionale dedicata ai materiali avanzati e alle loro possibili applicazioni nei settori industriali, con un focus particolare sui trasporti (aerospazio, automotive, navale e cantieristico).TRANSCRIPT
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Current and Future Materials for Lightweight Automobiles
Dr. P.K. MallickWilliam E. Stirton Professor of Mechanical EngineeringDirector, Center for Lighweighting Automotive Materials and Processing
University of Michigan-DearbornDearborn, MI 48128
Challenges for the Automotive Industry
Fuel Consumption Greenhouse Gas (GHG) Emission Safety Performance
Power (Acceleration) Comfort (Size, NVH, Ride Quality, etc.) Functionality Entertainment
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CAFE
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• CAFE standards for passenger cars:• Started with 18 mpg in 1978• 33.5 mpg in 2013• 35.5 mpg by 2016• 54.5 mpg by 2025
• Corporate Average Fuel Economy (CAFE) – mandatory minimum fuel economy standards for all cars and light trucks manufactured in USA
• Automobile companies pay penalty if they do not meet the fleet average CAFÉ standard.
CAFE Standard
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CAFE – Fleet Performance
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Global CO2 Emission (1900-2010)
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Sources of CO2 Emission (2010)
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Technological Trends for Future Automobiles Green Automobiles
Increase fuel economy Reduce pollution Reduce greenhouse gas effect Improve life-cycle value
Design Challenges Improved powertrain design Energy alternatives (EV, Hybrids, Fuel Cell, etc.) Vehicle weight reduction Reduce frictional and other losses Improved aerodynamic design Reduced tire rolling resistance
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Role of Advanced Materials
Provide required performance, safety and comfort
Reduce vehicle weight Reduce energy consumption in
production and manufacturing Reduce resource depletion Reduce effect on environmental
emissions
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Materials Scenario Steels
Mild Steels, High Strength Steels, Advanced High Strength Steels
Aluminum Alloys Magnesium Alloys Composites
CFRP, GFRP
Materials in US Automobiles
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Materials
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Materials
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Material % of Vehicle Weight
Major Application Areas
Steel 55 Body structure, body panels, engine and transmission components, suspension components, driveline components
Cast Iron 9 Engine components, brakes, suspension components
Aluminum Alloys 8.5 Engine block, wheels, radiator
Copper Alloys 1.5 Wiring, electrical components, radiator
Polymers (Plastics ) and Polymer Matrix Composites
9 Interior components, electrical and electronic components, fuel line components
Elastomers 4 Tires, trims, gaskets
Glass 3 Windshield, windows
Others 10 Fluids, lubricants, etc.
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Steels Advantages
High modulus (207 GPa) Wide range of strength depending on the type of
steel (up to 1500 MPa) High to excellent formability Good to excellent weldability Highly recyclable Low cost
Disadvantages High density (7.87 g/cm3)
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Steels Mild Steels (MS)
Plain carbon steels Interstitial free steels
High Strength Steels (HSS) Bake-hardenable (BH) steels Solution strengthened steels (SSS) High strength low alloy (HSLA) steels
Advanced High Strength Steels (AHSS) Dual phase (DP) steels Transformation-induced plasticity (TRIP) steels Martensitic steels Boron steels
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Steels
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Steels
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Distribution of MS, HSS and AHSS
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Applications of AHSS
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Applications of AHSS
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2011 Honda CR-Z
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Applications of AHSS
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Challenges for AHSS
Formability Springback
Edge Cracks
Joining – Spot welding is possible with proper adjustments in process parameters
Uniformity in Properties
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Aluminum Alloys
Advantages Low density (2.7 g/cm3 vs. 7.87 g/cm3 for steel) High strength-to-density ratio High thermal conductivity Both casting and wrought alloys are available Highly recyclable, but requires separation by alloy type
Disadvantages Lower modulus than steel’s Lower formability More difficult to weld compared to steel Comparatively higher cost
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Aluminum Alloys
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Aluminum Alloys
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Aluminum Spaceframe
Audi A8 First all aluminum
spaceframe in a production vehicle (1994)
Aluminum extrusions in the spaceframe and aluminum body panels
Self-piercing riveting, spot welding and weld bonding
40% weight saving
Aluminum Spaceframe
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Aluminum Spaceframe
Ford GT (2005) Aluminum Space- frame
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Aluminum Body
2015 Ford F-150 Pickup Truck (in production)
• 6000-series Aluminum Alloy for Body Panels
• Self-Piercing Riveted Joints with and without Adhesives
• Weight Reduction 700 lbs. (1,545 kg)
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Magnesium Alloys
Advantages Low density (1.74 g/cm3 vs. 7.87 g/cm3 for steel) High strength-to-density ratio High damping Casting alloys are highly castable
Disadvantages Comparatively low modulus Corrosion problems Wrought alloys have poor formability at room temperature Difficult to weld High cost
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Magnesium Alloys Front Crossmember
(Z06 Corvette) Engine Block
(Ford Duratec)
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Developments in New Manufacturing and Joining Technologies Tube and Sheet Hydroforming Superplastic Forming Tailor-Welded Blanking High Pressure Die Casting Semi-Solid Casting Laser Welding Friction Stir Welding Friction Stir Spot Welding Self-Piercing Riveting Weld Bonding/Rivet Bonding
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Polymer Matrix Composites
Advantages Very low density (1.2 – 1.6 g/cm3 vs. 7.87 g/cm3 for steel) High strength-to-density ratio High modulus-to-density ratio Design flexibility – can be tailor made per requirement High damping No corrosion
Disadvantages Can be moisture and temperature sensitive Moderate to high cost
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Polymer Matrix Composites
Many options: Fiber
Glass or Carbon Fibers Short or Continuous Fibers Unidirectional, Multi-directional or Random
Matrix Thermoset Polymer (epoxies, polyesters, vinyl
esters) Thermoplastic Polymer (polypropylenes,
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Polymer Matrix Composites (PMC)
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Current PMC used in high volume production automobiles use Glass fibers, not carbon fibers Short or long, not continuous Random, not uni- or multi-directional Thermoset polymers (either polyesters or vinyl
esters) for body panels and components Thermoplastic polymers for semi-structural and
functional components
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Current Use of Polymer Matrix Composites (PMC)
All PMC in current automobiles use E-glass fibers Short Fiber Thermoplastics (SFT)
Interior components, such as instrument panels Functional components, such as gears, switches
Long Fiber Thermoplastics (LFT) Interior components, such as interior door panels
Glass Mat Thermoplastics (GMT) Interior components, such as interior door panels Exterior components, such as bumper beams
Sheet Molding Compounds (SMC) Body panels, both exterior and interior Body components, such as bumper beams
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Potential Applications of PMC in Lightweight Automotive Structure
Body Panels Body Structural Components
Door intrusion beams, Roof rail sections, Cross beams, etc.
Frame and Sub-frame Sections Chassis Components
Control arms, Struts, etc.
Body-in-White Structure
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Carbon Fiber Composites (CFRP)
CFRP has a higher weight saving potential than GFRP.
Status of CFRP in the Auto Industry Has found niche and limited applications in high
performance, low production volume cars Used extensively in motor sports (Formula 1) Currently, there are no applications in high
production volume cars due to High price ($16/kg or higher) Limited availability
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Carbon Fiber Composite Applications:A Few Examples (2004 Model Year)
Vehicle Production Volume
Component
Porsche Carrera GT
1,500 in 3 years
Body panels, structure, engine subframe
BMW M3 CSL 1,000/yr. Roof, front air dam, rear spoiler
Mercedes SLR 500/yr. Body panels and structure
Acura NSX-R <200/yr. Hood, rear spoiler
Corvette Z06 3,000/yr. Hood
Dodge Viper 2,500/yr. Windshield frame, front end structure, door panels
Mazda RX-8 60,000/yr. Driveshaft
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CFRP Applications
BMW M6 Roof Panel
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CFRP Applications Wheel Carrier and Strut
Seat Structure
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CFRP Applications
Front Crush Members (SLR McLaren)
CFRP Applications
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Front Crash Box in Audi
Crushed Crash Box
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Developments Needed for PMC
Develop processing technology for thermoplastic matrix composites
Develop low cost carbon fibers Develop faster curing thermoset resins Develop long-term durability and design
data Develop more accurate design and
processing simulation techniques
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Nanocomposites Reinforcement types
Nanoclay Carbon Nanofibers Carbon Nanotubes
Their modulus and strength are much higher than that of glass and carbon fibers. For example: Modulus of crabon nanotubes is 1,100 GPa compared to 230 GPa for high strength carbon fibers
Only 3-5% (by volume) of nano-reinforcements can produce properties comparable to the ones produced by 30-40% (by volume) of glass or carbon fibers.
Electrical, optical, thermal and diffusion properties are also improved by significant amounts.
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Nanocomposites Examples of Nanoclay composites automotive
applications The first application was the Timing Belt Cover
(Toyota) using 4.2 wt.% nanoclay in nylon6 Engine covers, body side moldings, cargo floors, seat
backs, fuel lines Carbon nanofiber or carbon nanotube
composites are yet to be used in production vehicles Cost Manufacturing issues
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Mass Reduction/Cost Penalty
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SEA and Environmental Factors (Relative Values)
Material Specific Energy Absorption(kJ/kg)
Production Energy (kJ/kg)
CO2
Emission (kg/kg)
DQ 1 1 1
DP 1.25 1.4 1
AA 1.6 8.2 6
CFRP 4 11.5 10
GFRP 2.75 4.8 4
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Concluding Remarks Future lightweight vehicles will contain multiple
structural materials. Steels, especially advanced high strength steels (AHSS),
will continue to be used in safety-related structures Aluminum and CFRP may find greater use in body panels,
body components and chassis components. Cast magnesium and titanium may find increasing use in
engine and powertrain components.
Joining, repair and recycling are the three major issues to overcome in a multi-material vehicle.
Cost and customer acceptance are another major concerns.
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Reference Book Title: “Materials, design and
manufacturing for lightweight vehicles”
Editor: Prof. P. K. Mallick
Publisher: Woodhead Publishing UK
Year: 2010
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Thank you.