West Virginia University
MAE 343
Intermediate Mechanics of Materials
Xingbo Liu
Office: ESB 509
Phone: 293-3339
Email: Xingbo.Liu@mail.wvu.edu
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What did you learn in MAE 241?
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What did you learn in MAE 243?
Compression Tension (stretched) Bending
Torsion (twisted)
Shearing
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What will you learn in MAE 343?
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Case I: Challenger Explosion
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Case I: Challenger Explosion
Crew Members of Challenger
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Case I: Challenger Explosion
Reason of the Tragedy
"January 28, 1986,11:38:00 a.m. EST. First Shuttle liftoff scheduled from
Pad B. Launch set for 3:43 p.m. EST, Jan. 22, slipped to Jan. 23, then
Jan. 24, due to delays in mission 61-C. Launch reset for Jan. 25 because
of bad weather at transoceanic abort landing (TAL) site in Dakar,
Senegal.... Explosion 73 seconds after liftoff claimed crew and vehicle.
Cause of explosion was an O-ring failure in right SRB. Cold weather
was a contributing factor."
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Case II: Aircraft Engines
GP7200 Engine (General Electric)
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Working Conditions for Aircraft Engines
•
•
•
•
High Temperature
High Pressure
Corrosive
Long-term
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Turbine Materials
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Case III: How to make perfect fried chicken?
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Case IV: Speedo Swim Suite
http://www.youtube.com/watch?v=5DdwgJ5qOzY&e
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Materials Science
Properties
Composition
Processing
Microstructure
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Classification of Materials
Metals
Ceramics
Polymers
Composites
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Classes of Materials
• Metals
–
–
–
–
–
Iron and Steels
Aluminum and Alloys
Copper and Alloys
Nickel and Alloys
Titanium and Alloys
• Ceramics and Glasses
–
–
–
–
–
–
Alumina
Magnesia
Silica
Silicon Carbide
Silicon Nitride
Cement and Concrete
• Polymers
–
–
–
–
–
–
–
–
–
–
PE
PMMA
Nylon (PA)
PS
PU
PVC
PET
PEEK
EP
NR
• Composites
– GFRP
– CFRP
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Classes of Property
Economic
Price and availability
Recyclability
General Physical
Density
Mechanical
Modulus
Yield and tensile strength
Hardness
Fracture toughness
Fatigue strength
Creep strength
Damping
Thermal
Thermal conductivity
Specific heat
Thermal expansion coefficient
Electrical and Magnetic
Resistivity
Dielectric constant
Magnetic permeability
Environmental Interaction
Oxidation
Corrosion
Wear
Production
Ease of Manufacture
Joining
Finishing
Aesthetic
Color
Texture
Feel
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Metals
• Metals are typically split into ferrous (iron
containing) and non-ferrous
• Most widely used metals are alloys except for
aluminum and precious metals
• Metals are in general are good thermal and electrical
conductors. Many metals are relatively strong and
ductile at room temperature, and many maintain
good strength even at high temperature.
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Iron
Iron was the third of the prehistoric
materials ages (stone, bronze, iron).
Iron began to be used once furnaces
could be made hot enough to melt iron.
Iron quickly became the metal of
choice because of its abundance in the
earth’s crust.
Iron however has two major problems:
1) Corrosion
2) Brittleness
These problems are partially overcome
by alloying iron to make steel
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Steel
Steel is an alloy consisting mostly of iron, with a
carbon content between 0.02% and 1.7 or 2.04%
by weight (C:1000–10,8.67Fe), depending on
grade. Carbon is the most cost-effective alloying
material for iron, but various other alloying
elements are used such as manganese and
tungsten.[1] Carbon and other elements act as a
hardening agent, preventing dislocations in the
iron atom crystal lattice from sliding past one
another. Varying the amount of alloying elements
and form of their presence in the steel (solute
elements, precipitated phase) controls qualities
such as the hardness, ductility, and tensile
strength of the resulting steel. Steel with
increased carbon content can be made harder
and stronger than iron, but is also more brittle.
The maximum solubility of carbon in iron (in
austenite region) is 2.14% by weight, occurring
at 1149 °C; higher concentrations of carbon or
lower temperatures will produce cementite.
Alloys with higher carbon content than this are
known as cast iron because of their lower
melting point.[1]
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Steel
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Aluminum (Aluminium)
•
•
Aluminium or aluminum is a silvery and ductile member of the poor metal group of chemical elements. It has the symbol Al; its
atomic number is 13.
Aluminium is found primarily in bauxite ore and is remarkable for its ability to resist corrosion (due to the phenomenon of
passivation) and its light weight. Structural components made from aluminium and its alloys are vital to the aerospace industry
and very important in other areas of transportation and building.
Although aluminium is the most
abundant metallic element in Earth's
crust (believed to be 7.5% to 8.1%), it
is very rare in its free form, occurring in
oxygen-deficient environments such as
volcanic mud, and it was once
considered a precious metal more
valuable than gold. Napoleon III,
Emperor of France, is reputed to have
given a banquet where the most
honoured guests were given aluminium
utensils, while the other guests had to
make do with gold ones.
20th century metallurgists developed
improved processes for extraction.
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Aluminum
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SuperAlloys
•
•
A superalloy, or high-performance alloy, is
an alloy able to withstand extreme
temperatures that would destroy
conventional metals like steel and
aluminum. Superalloys exhibit excellent
mechanical strength and creep resistance
at high temperatures, good surface
stability, and corrosion and oxidation
resistance. Superalloys typically have an
austenitic face-centered cubic crystal
structure. A superalloy's base alloying
element is usually nickel, cobalt, or
nickel-iron. Superalloy development has
relied heavily on both chemical and
process innovations and has been driven
primarily by the aerospace and power
industries. Typical applications are in the
aerospace industry, eg. for turbine blades
for jet engines.
Examples of superalloys are Hastelloy,
Inconel, Haynes alloys, Incoloy, MP98T,
TMS alloys, and CMSX single crystal
alloys.
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Variety of ceramic applications
• Furnace linings, heat sinks, capacitors, fuel cells,
magnets (hard and soft), superconductors,
windows, optical fibers, nuclear fuel, artificial hip
joints, cutting tools, turbine blades, bearings
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What is a Ceramic?
• Solid compounds formed by heat or heat and
pressure that contain
– At least one metal and one non-metal or one non-metal elemental
solid (NMES) [MgO, Al2O3, YBa2Cu3O7]
– At least two NMES [SiC]
– At least two NMES and a non-metal
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My name is Bond…..
• In ceramics bonding is a mixture of ionic and
covalent
• If ionic bonding dominates crystal structures occur
that are typically based on FCC and HCP
• If covalent bonding dominates rings and tetrahedral
units are often seen
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Ceramics: crystalline and glassy
Continuous random
network oxide glass
Zinc blende (ZnS)
structure
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Repeat units of some common polymers
CH2CH2
• Poly(ethylene)
n
• Poly(propylene)
CHCH2
n
CH3
• Poly(styrene)
CHCH2
n
• Poly(ethylene-terephtalate)
CO
COO(CH2)2O
n
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Conformation of Polymers
Amorphous thermoplastic
Semi-crystalline thermoplastic
Crosslinked thermoset
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Plastics use in BMW 5 Series
PA
PBT+PC
PBT
PMMA
PE
PVC
ABS+PC
PUR
PP
ABS
POM
UP-GF
PPO
OTHERS
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Elastomers
(a)
(c)
(b)
• Entropy springs
• Lightly crosslinked
• Typically non-linear elastic
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Polyethylene
Polyethylene is classified into several different categories based mostly
on its density and branching. The mechanical properties of PE depend
significantly on variables such as the extent and type of branching, the
crystal structure, and the molecular weight.
Ultra high molecular weight polyethylene (UHMWPE)
Ultra low molecular weight polyethylene (ULMWPE - PE-WAX)
High molecular weight polyethylene (HMWPE)
High density polyethylene (HDPE)
High density cross-linked polyethylene (HDXLPE)
Cross-linked polyethylene (PEX)
Medium density polyethylene (MDPE)
Low density polyethylene (LDPE)
Linear low density polyethylene (LLDPE)
Very low density polyethylene (VLDPE
Polyethylene is one of the most widely used polymers because of its cost and
versatility.
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Spectra® fiber is one of the world’s strongest and lightest fibers.
A bright white polyethylene, it is, pound-for-pound, ten times
stronger than steel, more durable than polyester and has a
specific strength that is 40 percent greater than aramid fiber.
Spectra® fiber is made from ultra-high molecular weight
polyethylene that is used in a patented gel-spinning process.
Polyethylene is a remarkably durable plastic, and scientists at
Spectra Technologies have captured the tremendous natural
strength in the molecular backbone of this everyday plastic to
create one of the world’s strongest and lightest fibers. The gelspinning process and subsequent drawing steps allow Spectra®
fiber to have a much higher melting temperature (150°C or
300°F) than standard polyethylene.
With outstanding toughness and extraordinary visco-elactic
properties, Spectra® fiber can withstand high-load strain-rate
velocities. Light enough to float, it also exhibits high resistance
to chemicals, water, and ultraviolet light. It has excellent
vibration damping, flex fatigue and internal fiber-friction
characteristics, and Spectra® fiber’s low dielectric constant
makes it virtually transparent to radar.
Spectra® fiber is used in numerous high-performance
applications, including police and military ballistic-resistant
vests, helmets and armored vehicles, as well as sailcloth,
fishing lines, marine cordage, lifting slings, and cut-resistant
gloves and apparel. Honeywell also converts Spectra® fiber into
the Spectra Shield® family of specialty composites for armor
and other applications.
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Composite Materials
Polymer matrix
composite (PMC)
Carbon fiber
reinforced epoxy
crossply laminate
Metal matrix
composite (MMC)
Silicon carbide
particulate
reinforced
aluminum
Ceramic matrix
composite (CMC)
Silicon carbide
monofilament
reinforced glass
ceramic
After D. Hull and T. W. Clyne, “An introduction to composite materials”, 2nd Edition, Cambridge University
Press, Cambridge, (1996)
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Homework
http://www.wvusoftmatter.blogspot.com/
http://www.whystudymaterials.ac.uk/students/fun/cardgame/cardgame.asp
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