4301 l 1_2006
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1
MECH4301 2006
Materials Selection in Mechanical Design
Lecture 1
Materials Selection:Exploring the world of materials
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The evolution of materials (Ashby, 2005)
Unit 1, Frame 1.2
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The World of Engineering Materials
Composites
Sandwiches
HybridsLattices
Segmented
PE, PP, PCPS, PET, PVC
PA (Nylon)
PolymersPolyester
PhenolicEpoxy
Soda glassBorosilicate
GlassesSilica glass
Glass ceramic
IsopreneButyl rubber
ElastomersNatural rubber
SiliconesEVA
AluminaSi-carbide
CeramicsSi-nitrideZiconia
SteelsCast ironsAl-alloys
Metals, alloysCu-alloysNi-alloys
Ti-alloys
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Materials and design (Ashby, 2005)
The goal of design: To create products that perform their function effectively, safely,at acceptable cost and environmentally sound. What do we need to know to do this?More than just test data.
DATA
Test Test data
Data
capture
Statistical
analysis
Allowables
Mechanical PropertiesBulk Modulus 4.1 - 4.6 GPaCompressive Strength 55 - 60 MPaDuctility 0.06 - 0.07Elastic Limit 40 - 45 MPaEndurance Limit 24 - 27 MPaFracture Toughness 2.3 - 2.6 MPa.m1/2
Hardness 100 - 140 MPaLoss Coefficient 0.009- 0.026Modulus of Rupture 50 - 55 MPaPoisson's Ratio 0.38 - 0.42Shear Modulus 0.85 - 0.95 GPa
Tensile Strength 45 - 48 MPaYoung's Modulus 2.5 - 2.8 GPa
Successfulapplications
$
Economic , environmental and
business caseSelection of
material and process
Potentialapplications
Characterisation Selection and implementation
INFORMATION KNOWLEDGE
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Mechanical properties illustrated (Ashby, 2005)
StiffStrong
Tough
Light
Not stiff enough (need bigger E)
Not strong enough (need biggery
)
Not tough enough (need bigger Kic)
Too heavy (need lower )
All OK !
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Intro to the courses main tool:
CES Selector software package
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Structured information for ABS*
Acrylonitrile-butadiene-styrene (ABS) - (CH2-CH-C6H4)n
General PropertiesDensity 1.05 - 1.07 Mg/m^3
Price 2.1 - 2.3 US $/kg
Mechanical PropertiesYoung's Modulus 1.1 - 2.9 GPa
Elastic Limit 18 - 50 MPa
Tensile Strength 27 - 55 MPa
Elongation 6 - 8 %
Hardness - Vickers6 - 15 HV
Endurance Limit 11 - 22 MPa
Fracture Toughness 1.2 - 4.2 MPa.m1/2
Thermal PropertiesMax Service Temp 350 - 370 K
Thermal Expansion 70 - 75 10-6/K
Specific Heat 1500 - 1510 J/kg.K
Thermal Conductivity 0.17 - 0.24 W/m.K
Electrical PropertiesConductor or insulator? Good insulator
Optical PropertiesTransparent or opaque? Opaque
Corrosion and Wear Resistance
Flammability AverageFresh Water Good
Organic Solvents Average
Oxidation at 500C Very Poor
Sea Water Good
Strong Acid Good
Strong Alkalis Good
UV Good
Wear Poor
+ links to processes
*Using the CES Level 2 DB
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Unstructured information for ABS*What is it?ABS (Acrylonitrile-butadiene-styrene ) is tough, resilient, and easily molded. It isusually opaque, although some grades can now be transparent, and it can be given vivid colors.ABS-PVC alloys are tougher than standard ABS and, in self-extinguishing grades, are used for the
casings of power tools.
Design guidelines. ABS has the highest impact resistance of all polymers. It takes colorwell. Integral metallics are possible (as in GE Plastics' Magix.) ABS is UV resistant for outdoorapplication if stabilizers are added. It is hygroscopic (may need to be oven dried beforethermoforming) and can be damaged by petroleum-based machining oils.
ABS can be extruded, compression moulded or formed to sheet that is then vacuum thermo-formed. It can be joined by ultrasonic or hot-plate welding, or bonded with polyester, epoxy,isocyanate or nitrile-phenolic adhesives.
Technical notes.ABS is a terpolymer - one made by copolymerising 3 monomers: acrylonitrile, butadiene and syrene. The acrylonitrilegives thermal and chemical resistance, rubber-like butadiene gives ductility and strength, the styrene gives a glossy surface, ease of machiningand a lower cost. In ASA, the butadiene component (which gives poor UV resistance) is replaced by an acrylic ester. Without the addition ofbutyl, ABS becomes, SAN - a similar material with lower impact resistance or toughness. It is the stiffest of the thermoplastics and hasexcellent resistance to acids, alkalis, salts and many solvents.
Typical Uses. Safety helmets; camper tops; automotive instrument panels and other interior components; pipe fittings; home-securitydevices and housings for small appliances; communications equipment; business machines; plumbing hardware; automobile grilles; wheelcovers; mirror housings; refrigerator liners; luggage shells; tote trays; mower shrouds; boat hulls; large components for recreational vehicles;weather seals; glass beading; refrigerator breaker strips; conduit; pipe for drain-waste-vent (DWV) systems.
The environment. The acrylonitrile monomer is nasty stuff, almost as poisonous as cyanide. Once polymerized with styrene it becomes
harmless. ABS is FDA compliant, can be recycled, and can be incinerated to recover the energy it contains.
*Using the CES Level 2 DB
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CES : the 3 levels
Level 1 1st year students:Engineering andMaterials Science.
64 materials, 60processes
Who is it for?
Level 2 2nd - 4th yearstudents of Engineeringand Materials Science
and Design.
91 materials, 68processes
Level 3 4th year, masters andresearch students ofEngineering Materials
and Design.
Technical data for3000 materials and200 processes.
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Finding information with CES
Links
Data
tableProcessesMaterials
Data
table
Find what?
Which table?
Choose what you want toexplore (materials, processes..)
MaterialsMetals
Polymers
Ceramics
etc
ProcessesCasting
Moulding
Powder
etc
Browse Select SearchToolbar Print Search web
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Relationships, perspective and comparisons
Material bar-charts
Material property charts
Data sheets do not allow comparison,
perspective. For these we need
Metals Polymers Ceramics Hybrids
PEEK
PP
PTFE
WC
Alumina
Glass
CFRP
GFRP
Fibreboard
Young
sm
odul u
s,G
Pa
Steel
Copper
Lead
Zinc
Aluminum
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Creating charts
Property
New
Graph stage
Limit stage
Tree stage
Browse Select Search Print Search webToolbar
Property
2
Property 1
Select what? Materials, Level 1
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Bar- chart created with CES (Level1)
Bar Charts allow exploring relationships
Bar Charts allow selection and sorting
UntitledMaterials:\MET ALS Materials:\POLYMERS Materials:\CERAMICS and GLASSES Materials:\COMPOSIT ES
Young'sModulus(GPa)
1e-004
1e-003
0.01
0.1
1
10
10 0
1000
Low alloy steel
Mg-alloys
Al-alloys
Zn-alloys
Ti-alloys
Cu-alloys
Stainless steel
High carbon steel
Acetal, POM
Polyurethane
EVA
IonomerPTFE
WC
Alumina
Glass Ceramic
Silica glass
Soda-Lime glassPolyester, rigid
PC
PS
PUR
PE
ABS
PP
BC
SiCAl-SiC Com posite
CFRP
KFRP
GFRP
Plywood
Neoprene
Natural Rubber (NR)
CompositesPolymersMetals Ceramics & glass
Youngs
modulus
(G
Pa)
Metals Polymers Ceramics Hybrids
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Material property- charts: modulus - density
0.1
10
1
100
Metals
Polymers
Elastomers
Ceramics
Woods
Composites
Foams
0.01
1000
1000.1 1 10
Density (Mg/m3)
YoungsmodulusE,
(GPa
)
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Mechanical properties: modulus and density (CES chart)
Questions:
Why the enormousdifferences?
Why are metals hereand polymers here?
Bonding, packing.
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Thermal properties
Questions:
Why the enormousdifferences?
What determines expansionand conductivity?
Electronic and phonon
contributions to conductivity
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Charts offer both Methods and Tools
Materials that are stiff?
At this stage you have a selection tool.
Materials with low expansion?
Charts help developing a perspective
with high conductivity?
Materials that are light and compliant?
Materials that are light and stiff?
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