© MFA and DC 2007
New approaches to Materials Education - a course authored by Mike Ashby and David Cebon, Cambridge, UK, 2007
Unit 3. Translation, Screening,
Documentation:
the first steps of optimised
selection
© MFA and DC 2007
This Unit
Unit 4
This Unit
Outline
Step 2 Screening: eliminate materials that cannot do the job
Step 3 Ranking: find the materials that do the job best
Step 4 Documentation: explore pedigrees of top-ranked candidates
Step 1 Translation: express design requirements as constraints and objectives
Selection has 4 basic steps
More info:
• “Materials: engineering, science, processing and design”, Chapter 3
• “Materials Selection in Mechanical Design”, Chapters 5 and 6
The design process
• Exercises
© MFA and DC 2007
The design process and material search space
Product specification
Concept
Embodiment
Detail
Market need
Problem statement
Final choice
Material search space
Screen
Screen
Rank
All materials
Increasingconstraints
Material & process needs
Choice of material family(metals, ceramics, polymers..)
Choice of material class(Steel, Al-alloy, Ni-alloy…..)
Choice of single material (Al-2040, Al-6061, Al-7075…..)
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Need – Concept -- Embodiment
ConceptsNeed
Embodiments
Direct pull Levered pull Spring assisted pullGeared pull
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Embodiment -- Detail
© MFA and DC 2007
The decision-making strategy
Design requirements
expressed as
Constraints and
Objectives
Normative information
Material attributes
Process attributes including prompts for
Intuitive estimation
Factual information
Final selection
Comparison engine
Screening
Ranking
Documentation
Methodic information
© MFA and DC 2007
The decision-making strategy
Desired features
expressed as
Constraints and
Objectives
Normative information
Automobile
attributes including prompts for
Intuitive estimation
Factual information
Final selection
Comparison engine
Screening
Ranking
Documentation
Methodic information
© MFA and DC 2007
Translation to create Normative information
Translation: “express design requirements as constraints”
Constraints What essential conditions must it meet ?
Free variables Which design variables are free ?
Design requirements
ObjectivesWhat measure of performance is to be maximized or minimized ?
Choice of material
Be strong enough Conduct electricity Tolerate 250 C Be able to be cast
Cost Weight Volume Eco-impact
Function What does the component do ?
A label
© MFA and DC 2007
Translation: a heat sink for power electronics
Power micro-chips get hot. They have to be cooled to prevent damage.
Free variable Choice of material
Constraints 1. Max service temp > 200 C
2. “Good electrical insulator”
3. “Good thermal conductor”
(or T-conduction > 25 W/m.K)
Translation
Function Heat sinkKeep chips below 200 C without any electrical coupling.
Design requirements
© MFA and DC 2007
A Limit stage
Thermal properties Min. Max
Mechanical properties
Maximum service temperature C
Thermal conductivity W/m.K
Specific heat J/kg.K
Electrical properties
Electrical conductor or insulator?
Good conductor
Poor conductor
Semiconductor
Poor insulator
Good insulator
Thermal properties Min. Max
Mechanical properties
Maximum service temperature C
Thermal conductivity W/m.K
Specific heat J/kg.K
Electrical properties
Electrical conductor or insulator?
Good conductor
Poor conductor
Semiconductor
Poor insulator
Good insulator
Screening using a LIMIT STAGE
Browse Select Search Print Search web
Screening: “Eliminate materials that can’t do the job”
2. Selection Stages
Graph Limit Tree
1. Selection data
Edu Level 2: MaterialsEdu Level 2: Materials
Results X out of 95 pass
Material 1 2230 113
Material 2 2100 300
Material 3 1950 5.6
Material 4 1876 47
etc...
Ranking Prop 1 Prop 2
200
25
© MFA and DC 2007
2000C
Screening using a GRAPH STAGE
Browse Select Search Print Search web
File Edit View Select Tools
Don’t need numbers!
1. Selection data
Edu Level 2: MaterialsEdu Level 2: Materials
Results X out of 95 pass
Material 1 2230 113
Material 2 2100 300
Material 3 1950 5.6
Material 4 1876 47
etc...
Ranking Prop 1 Prop 2
1000
0.1
Metals
Polymers & elastomersComposites
Foams
1030 1 1010 1020
Ceramics
10
1
100
0.01
Electrical resistivity (.cm)
T-c
on
du
ctiv
ity
(W/m
.s)
PEEK
PP
PTFE
PEEK
PP
PTFE
WC
Alumina
Glass
WC
Alumina
Glass
CFRP
GFRP
Fibreboard
CFRP
GFRP
Fibreboard
Steel
Copper
Lead
Zinc
Aluminum
Steel
Copper
Lead
Steel
Copper
Lead
Zinc
Aluminum
Max
ser
vice
tem
p.
(K)
Metals Polymers Ceramics Composites
2. Selection Stages
Graph Limit Tree
© MFA and DC 2007
Translation: a CD case, an example of redesign
Free variable Choice of material
CD cases are made of polystyrene (PS). They crack and scratch the disks. Find a better material.
Injection-moldable
Contain and protect CD better than the PS case.
As transparent as PS
Recylable
Design requirements
Function CD enclosure
Translation
Constraints
1. Can be injection molded
2. Toughness K1c > that of PS
3. Optically clear
4. Can be recycled
© MFA and DC 2007
Screening using a TREE STAGE
Tree stage for material
Material
Ceramics Steels
Hybrids Al alloys
Metals Cu alloys
Polymers Ni alloys...
2. Selection Stages
Graph Limit Tree
Browse Select Search Print Search web
1. Selection data
Edu Level 2: MaterialsEdu Level 2: Materials
Process
Join
Shape
Surface
Cast
Deform
Mold
Composite
Powder
Prototype
Tree stage for processResults X out of 95 pass
Material 1
Material 2
Material 3
Material 4
etc...
© MFA and DC 2007
Stacking selection stages
Pro
per
ty
Stacked stages
Browse Select Search Print Search web
1. Selection data
Edu Level 2: MaterialsEdu Level 2: Materials
Density
Modulus
Strength
T-conduction
2
10010
200
Min Max
Process
Join
Shape
Surface
CastDeformMoldComposite PowderPrototype
2. Selection Stages
Graph Limit Tree
Results X out of 95 pass
Material 1 2230 113
Material 2 2100 300
Material 3 1950 5.6
Material 4 1876 47
etc...
Ranking Prop 1 Prop 2
© MFA and DC 2007
Optical properties
Transparency
Eco properties
Recycle
Optical quality
Transparent
Translucent
Opaque
3
Tree stage: injection mold1
Fra
ctur
e to
ughn
ess
Polystyrene
Keep these!
2
The CD case: the whole story
Select Level 2: Materials
Free variable Material
Function CD enclosure
Translation
Constraints
1. Can be injection molded
2. Toughness K1c > that of PS
3. Optically clear
4. Can be recycled
© MFA and DC 2007
Documentation: the pedigree
Granta’s Web Portal (http://matdata.net) gives indexed access to information providers’ web sites.
Documentation: “now that the number of candidates is small, explore their character in depth”
Suppliers’ data sheetsHandbooks
Material portals
Tradeassociations
Documentation:the “pedigree” of surviving candidates
© MFA and DC 2007
Documentation with CES
Browse Select Search Print
ResultsX out of 94 pass
Material 1
Material 2
Material 3
Material 4
Material 5
………..
Search web
Matdata.netSearches information sources
for selected record
1. Selection data
Edu Level 2: MaterialsEdu Level 2: Materials
2. Selection Stages
Graph Limit Tree
Open the record
Age hardening ALUMINUM ALLOYS The material The high-strength aluminum alloys rely on age-hardening: a sequence of heat treatment steps that causes the precipitation of a nano-scale dispersion of intermetallics that impede dislocation motion and impart strength. General properties Density 2500 - 2900 kg/m^3 Price 1.423 - 2.305 USD/kg Mechanical properties Young's modulus 68 - 80 GPa Elastic limit 95 - 610 MPa Tensile strength 180 - 620 MPa Elongation 1 - 20 % Hardness - Vickers 60 - 160 HV Fatigue strength at 107 cycles 57 - 210 MPa Fracture toughness 21 - 35 MPa.m^1/2 Thermal properties Thermal conductor or insulator? Good conductor Thermal conductivity 118 - 174 W/m.K
Age hardening ALUMINUM ALLOYS The material The high-strength aluminum alloys rely on age-hardening: a sequence of heat treatment steps that causes the precipitation of a nano-scale dispersion of intermetallics that impede dislocation motion and impart strength. General properties Density 2500 - 2900 kg/m^3 Price 1.423 - 2.305 USD/kg Mechanical properties Young's modulus 68 - 80 GPa Elastic limit 95 - 610 MPa Tensile strength 180 - 620 MPa Elongation 1 - 20 % Hardness - Vickers 60 - 160 HV Fatigue strength at 107 cycles 57 - 210 MPa Fracture toughness 21 - 35 MPa.m^1/2 Thermal properties Thermal conductor or insulator? Good conductor Thermal conductivity 118 - 174 W/m.K
© MFA and DC 2007
These areoften enough !
The four steps of selection:
1. Translation, giving constraints and objectives
2. Screening , using constraints
3. Ranking, using objectives
4. Documentation in CES, and http://matdata.net
The main points
CES allows Screening using
• Limit stages,
• Graph stages
• Tree stages and
• All three in any number and sequence
© MFA and DC 2007
Pause for demo
© MFA and DC 2007
Exercise: Stage 1, a tree stage
3.1 A material is required for a molded electrical enclosure that may be used outdoors. There are requirements on
Processing (this Stage) Properties (Stage 2) Price (Stage 3)
Apply Stage 1 – a Tree Stage Tree stage ProcessUniverse Shaping Molding -- Insert OK
Now add Stage 2 – next page
Browse Select SearchBrowse Select Search
Select from materials or process tree
1. Selection data
Edu Level 2: MaterialsEdu Level 2: MaterialsEdu Level 2: MaterialsEdu Level 2: Materials
2. Selection Stages
Graph Limit Tree
2. Selection Stages
Graph Limit Tree
© MFA and DC 2007
Exercise: Stage 2, a limit stage
3.2 The material of the enclosure must have
Hardness - Vickers > 8 HV
Be a good electrical insulator
Have dielectric strength > 10 MV/m
Be able to be recycled
Mechanical properties
Electrical properties
Eco propertiesRecycle
Good conductor
Poor conductor
Poor insulator
Good insulator
Hardness - Vickers 8 HV
Conductor or insulator?
Dielectric strength 10 MV/m
Mechanical properties
Electrical properties
Eco propertiesRecycle
Good conductor
Poor conductor
Poor insulator
Good insulator
Good conductor
Poor conductor
Poor insulator
Good insulator
Hardness - Vickers 8 HV
Conductor or insulator?
Dielectric strength 10 MV/m
Now add Stage 3 – next page
Browse Select SearchBrowse Select Search
1. Selection data
Edu Level 2: MaterialsEdu Level 2: MaterialsEdu Level 2: MaterialsEdu Level 2: Materials
2. Selection Stages
Graph Limit Tree
2. Selection Stages
Graph Limit Tree
Enterlimits
© MFA and DC 2007
Exercise: Stage 3, a graph stage
3.3 The material of the enclosure should be as cheap as possible. Find the four materials meeting all the previous constraints that have the lowest price per kg.
Graph stage – Y-axis – Price
Hide all materials failing previous stages
Rank the final Results list by Price
Browse Select SearchBrowse Select Search
1. Selection data
Edu Level 2: MaterialsEdu Level 2: MaterialsEdu Level 2: MaterialsEdu Level 2: Materials
2. Selection Stages
Graph Limit Tree
2. Selection Stages
Graph Limit Tree
ChooseY-axis
3. Results: 15 of 95 passName Price (USD/kg)Polypropylene (PP) 1.41 - 1.62Soda-lime glass 1.41 - 1.659Polystyrene (PS) 1.476 - 1.574Polyvinylchloride (tpPVC) 1.6 - 2.2Polyethylene terephthalate (PET) 1.608 - 1.769Polyethylene (PE) 1.718 - 1.89Polyoxymethylene (Acetal, POM) 2.203 - 2.732Polymethyl methacrylate 2.335 - 2.569Acrylonitrile butadiene styrene (ABS) 2.511 - 2.952Polyamides (Nylons, PA) 3.194 - 3.569Polycarbonate (PC) 3.6 - 4.47Polylactide (PLA) 3.667 - 4.584Polyurethane (tpPUR) 3.723 - 4.45Cellulose polymers (CA) 3.921 - 4.313Polyetheretherketone (PEEK) 99.14 - 109
© MFA and DC 2007
End of Unit 3
