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MecE 360: Engineering Design II
Section 3: Materials
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Class Notifications
Jason Carey will be providing information about graduateopportunities
B and A group meeting sign-up outside of 10-227
Quiz 1: early Feb
I posted: old A3 and soln online Class notes purchased through MECE club for $20
Many extra examples, detailed notes
Teams are notified of projects
Relaxed design specifications as long as explained
5 pages of writing: figure out story, and write
Keys success : bearing, connections, fatigue, creativity
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Objectives
Initial considerations Materials, loading, failure
Presentation on designing materials
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Material Considerations (p.3-2)
1. Availability and cost
It is very possible that the perfect material existsfor you design - but at what cost.
Titanium: high specific strength (strength/density).But costs $8.20/ kg vs. $1.50/kg for Al.
2. Strength
Critical for stress related failure (Section 5).
n
TCy
applied
,,
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3. Rigidity/stiffness
Designs are often limited by the amount of deflectionbetween mating components for alignment and propermating.
Deflection is dependent on elastic modulus (E) andgeometry.
4. Hardness and ductility
Is scratch resistance or large deformation important? Contact problems: wear
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5. Resistance to fatigue
Steel and aluminium have different fatigue behaviour.
6. Manufacturability and machinability
How easy is it to build?
3D printing: only certain materials
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7. Resilience
The energy before yielding is important for combinedloading, temperature effects.
8. Friction coefficient Different applications require different surfaces or
mediums for proper functions, e.g. bearings low, andclutches high
9. Weight
Some designs are weight critical: consider polymers,wood, foams, aluminium or titanium.
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Uncertainty (p.3-3)
Uncertainty and variability in material properties areinherent due to microstructure variability
Assessed through experimental testing.
0
20
40
60
80
100
120
140
40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61
Sy (kpsi)
Numberoftes
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Engineering Materials
Metals: Magnesium
Ceramic: alumina
Polymer: electrospun polyethylene oxide-Garcia and Hernandez 2014
Carbon-reinforced-composite
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Metals (p.3-6)Produced with a Trial Version of PDF Annotator - www.PDFAnnotator.com
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Polymers (p.3-7)
Different behaviour based on microstructure/chain linking
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Polymers
Properties change
significantly withincreasing temperature
Modulus drops
Should not used above
glass transitiontemperature
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Composite Materials (p.3-9)
In general, composites consistof two or more materials
Fiber-reinforced polymers (FRP)
long fibers in resin matrix
fibers strength, brittle
resin toughness,rigidity, protection offibers
Lamina is transverse isotropic material
Properties proportional to fiber volume fraction
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Composite Materials
Several laminae combined form a laminate
Laminates can be quasi-isotropic
Laminate layup canbe tailored to meetspecific strength andstiffness requirements
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Ceramics (p.3-8)
Only for compressiveloading
Poor in tension,cracks propagate
catastrophically Reinforced with steel,
or fibre reinforcedpolymers
Good thermal andelectrical insulators
More later
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Comparison (p.3-10)
Material Advantages Disadvantages
SteelStrength, stiffness, ductility, strength and corrosionresistance adjustable with alloying elements
Heavy
Aluminum Lightweight, high ductility, corrosion resistant Low strength and stiffness
Brass Corrosion resistant, good wear properties Heavy, cost
TitaniumGood strength over wide temperature range,corrosion resistant, lightweight
Poor machinability, cost
Polymers
Lightweight, corrosion resistant, easy to form andmanufacture, versatile, impact resistance, shockand vibration absorbance, low friction and wear,recyclable (thermoplastics)
Low strength and stiffness, smalltemperature changes causelarge change in properties, poorrecyclability (thermosets)
FRPComposites
Lightweight, high specific strength and stiffness,corrosion resistant, flexible design and versatility
Brittle, expensive, poorlycharacterized (codes/standards),quality strongly affected by
manufacturing, poor recyclability
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Material Selection (p.3-16)
1. Decision matrix
Simple, basic design
Need specifications/requirements
Select material that best meets the specs
See previous sections for example2. Ashby charts
Advanced methodology
Allows for optimization
Need information on function, objective, constraints
examples will be presented in Seminar #3 Ive never seen this in a 460 report, attempt to incorporate here
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Material Selection:Ashby Charts
Used with permission:Materials Selection in Mechanical Design, 2nd Edition, M.F. Ashby, Elsevier, 2011.
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Material Selection:Ashby Charts
Three basic elements are required for the selection charts:
Materials Selection in Mechanical Design, 2nd Edition, M.F. Ashby, Elsevier, 2011.
P d d ith T i l V i f PDF A t t PDFA t t
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Performance (p) of a component based on the requirements of the design
Designs will have three requirements:
1. functional
2. geometric3. materials property
These are associated to a function (equation)(which are assumed be independent of each other)
MGFfp ,
properties
Material,
parameters
Geometric,
tsrequiremen
Functional,,
MfGfFfp321
Material Selection:Ashby Charts
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P d d ith T i l V i f PDF A t t PDFA t t
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Comments
Example: All the materialslying on a line of constantE1/2/rperform equally wellas a light stiff beam.
Those above the line are
better, those below, worse. A material withM= 8 in
these units gives a beamwhich has one quarter theweight of one withM= 2.
Example in seminar
Materials Selection in Mechanical Design, 2nd Edition, M.F. Ashby, Elsevier, 2011.
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38
Designing Next Generation
Protection Materials
Jamie HoganAssistant ProfessorMechanical EngineeringUniversity of Alberta
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Take Away
Exposure to brittle materials
Failure depends on microstructure, stress-state and strain-rate
Talk about how to design microstructures to control failure
Example: fragmentation for body armor applications
50 um
PADB4C-Microstructure300 um
PADB4C- Fragments
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Materials in Defense Applications
bankspower.com
www.galls.com
Big question: Why is one system better than the other?
1. Requires fundamental understanding of material failure (experiments and models)
2. Manufacturing processes to produce tailored microstructures (processing)
http://bankspower.com/fridaynightnews/show/94-Hot-Rod-Humveehttp://www.galls.com/http://www.galls.com/http://bankspower.com/fridaynightnews/show/94-Hot-Rod-Humvee7/25/2019 Fatigue Design Notes
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Approaches to Materials Design
Microstructures and material properties (K1c, , E, ) + identification of failure mechanisms
Material Science: alter microstructure property performance (test, test, test)
Mechanics: microstructure/properties mechanisms (models) performance
Philosophy: see it (experiments), understand it (models), control it (processing)
Twinning in Mg (Dixit)
10 um
Boron Carbide Microstructure
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Failure Mechanisms in Brittle Materials
Failure: Defects nucleate mechanisms, which lead to macro-cracks, and often to catastrophic failure
Defects: grain boundaries, secondary phases, initial cracks (we want to identify key defects)
Objective: Control failure mechanisms by designing the defect populations (microstructure design)
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Impact Failure of Brittle Materials
Failure Processes (time and space):
1. Fracture
2. Granular flow
3. Plasticity
4. Phase transformations (amorphization)
Manifest in fragmentation
Hypothesis: controlling fragmentation willlead to improved performance
Material: boron carbide
Fig. Impact into PAD B4C at 930 m/s
500 microns
Fig. Ballistic fragments for PAD B4C at 930 m/s
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1. See it:
Microstructure Characterizationand Experimentation
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Boron Carbide Material Composition: B4C (or B12C3): rhombohedral (bucky balls)
High hardness (Mohs 9.5) and low density (2.5 g/cm3)
Silicon carbide (SiC): 3.2 g/cm3
Manufacturing: grow boron crystal, ball milled, hot-presswith carbon and aluminum nitride additives
Yields defects (serve as fracture sites).
Not all defects are bad
10 um
PADB4C- Microstructure
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Boron Carbide Defect Microstructure*
Globules (ellipsoids): graphitic disks Spherical features: graphite/pores
Bright phases: aluminum nitride
Q: What processing defects initiate failure?
Hogan et al. JACS 2014
Hot Pressing Direction
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Strength and Failure
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Dynamic Compressive Failure
2.5 mm2 Mfps, exposure= 500 ns
2.5 mm5 Mfps, exposure= 110 ns
Unconfined Configuration Bi-Axial Confined Configuration
Strain rates: ~10-3 (MTS) and ~10+3 s-1 (Kolsky bar) and Stress-states: compression, confined, tension (BD)
Crack speeds set deformation time scales: 2,000 +/- 300 m/s (left) vs. 510 +/- 130 m/s (right)
Deformation mode changes with confinement: need to understand this
Hogan et al. JACS 2014
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Strength: Confinement Effects
Confined Configuration
Unconfined Configuration
HotPressingAxis
HotPressingAxis
We can use strength measurements to guide us on package design
Hogan et al. Acta 2015
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Rate-Dependent Strength
Kimberley et al. 2013 scaling relation forstrength as a function of strain rate*
Dynamic strength of brittle materialsis controlled by fracture
Governed by microstructure featuresandproperties
This example: can control strength bycontrolling fracture through design ofdefect populations
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Fractography: Failure Mechanisms
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2. Understand it:
Compressive BrittleFragmentation Model
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2. Understand It: Theoretical andComputational Modeling
Brittle Failure Model Crack Growth
Anisotropic Damage
Initial Damage
Flaw Size distribution
Flaw Orientation distribution
Flaw Density
Damage Evolution
Crack growth Kinetics
Micromechanics
Self-ConsistantScheme
IrreversibleDamage Strain
StiffnessDefinition
Evolution as afunction of Damage
Influence of BulkingFlow Behavior
Granular Flow
EOS
Visco-Plastic Flow
Porosity
Crack Coalescence
Crack Nucleation
Inputs From Experiments
Figure 9. Inclusion number/area fraction vs.inclusion size distribution.
Figure 11. Orientation of inclusions in relation tothe hot pressing axis (AR is the aspect ratio).
Flaw Density (#/m2)
and Spacing
Incorporate the physics in the model: properties and microstructure
Fig. Mind-map for brittle failure
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2. Strength and FragmentationMicro-Mechanical Models
0
0.5
1
1.5
2
2.5
0
0.5
1
1.5
2
2.5
3
0 0.002 0.004 0.006 0.008
Tr(Damage)
Stress(GPa)
Strain
Flaw Size Dependence
6 m
10 m
20 m
40 m
1000 s-1
We can use simple models to inform about materials design
10-4
10-3
10-2
10-1
100
101
102
10-2
10-1
100
101
102
103
Normalized Strain Rate
N
ormalizedSize
Grady 2006
Glenn and Chudnovsky 1986
Zhou et al. 2006
Levy and Molinari 2010
Mod. Grady (vcc)
Spinel
PAD SiC-N
PAD B4C
BasaltStony meteorite
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3. Control it:Materials Design
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Ballistic Performance Curve
Highlights power of simple model to inform design decisions
Remember: consider physics of problems (whats importantand what isnt)
Normalized Velocity
0.7 0.75 0.8 0.85 0.9 0.95 1 1.05
Pr
obability
of
Penetration
0
0.2
0.4
0.6
0.8
1PS B4C
HP B4C
Hot-pressed (PAD-B4C)
Pressureless sintered (PS)
We designed microstructures for controlled strength andfragmentation outcomes
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5. Summary
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Take Away
Exposure to brittle materials
Failure depends on microstructure, stress-state and strain-rate
Talk about how to design microstructures to control failure
Example: fragmentation for body armor applications
Fig. Impact into PAD B4C at 1000 m/sCompressive failure of boron carbide
Length: 5 mm
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Acknowledgements
Support of the Materials in Extreme Dynamic EnvironmentsCollaborative Research Alliance through Cooperative AgreementNumber W911NF-12-2-0022.
Support from ARL (ITOL 2015-2443) NSERC Engage
CFI for ultra-high-speed camera
Lukasz Farbaniec, Debjoy Mallick, Matt Shaeffer, NitinDaphalapurkar, Ravi Sastri, Jim McCauley, KT Ramesh
Undergraduate support: Will Wagers, Erez Krimsky
James Hogan email:[email protected]
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Bonus Work for ME 360
Assigned as 5%+ on quiz #1
Develop 1 ppt slide:
Choose an industrial application that interests you
Select a material within that application
Show its microstructure, material properties
Address why it is used in this application
Be creative
Due before Quiz 1- assignment box will be created
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Next Topic
Unit # 2: Initial Considerations
Section 4: Loading and deflections
Static Cyclic
Impact
Beam deflection Section 5: Failure criteria
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