1. „Software-based systematic approaches to material
selection and lightweighting‟
Sirris Materials Day
4th October 2011 - Ghent
Dr Charles Bream
www.grantadesign.com

2. Granta Design - Introduction
Granta Design – history
• Founded in 1994 from the University of Cambridge
 Professors Mike Ashby & David Cebon
 Owners: Cambridge Univ, ASM International, Founders, Employees
• Technology firsts include:
 Materials selection (Ashby charts, performance indices…)
 Integrated materials data management
 Software-based teaching of materials engineering
The materials information technology experts
• Software – manage materials information, selection…
• Data products – specialist materials data libraries
• Services – implement, configure, apply…
Customers
• Airbus, Arcelor, Aubert & Duval, Boeing, Dow, Emerson, EADS
Astrium, Ferrari, GE, Honeywell, IHI, J&J, Moen, NASA…
• 800+ universities worldwide

3. Selection of Materials
When? How?
 Use previous or familiar material
Design brief / requirements  Ask material supplier
 Ask colleague or consultant
 Development trials
Preliminary design concept CAD
CAD, CAE
Detailed design Optimisation packages
Implication of using wrong material:
Prototype & testing
 Suboptimal design
Increasing:
 Non-competitive
Time
Effort Final design LCA  Extended development cycle
Cost  Product recall

4. Systematic Material Selection
All materials
Breakdown design requirements into:
Function – What does the component do?
Constraints – What essential conditions must be met?
Objectives – What is to be maximized or minimized?
Free variable – What am I free to change?
Screen on constraints - ‘Go’ / ‘no-go’ criteria (usually many)
Rank on objectives - Ordering of materials that ‘go’
Top candidate materials
Supporting information – Specialist databases, contact suppliers
Local conditions – Preferred suppliers, process capability, location
Final Selection

5. Train Floor Example
Design Requirements:
Function:
Self-supporting „Intermediate‟ floor for train carriage
 Panel loaded in bending
 Stiffness-limited design
 Length, width specified
 Thickness free
Screen on Constraints:
• Temperature resistance (-40°C to +85°C)
• Adequate toughness & strength
• Durable to rain and salt water
• Manufacture from flat sheet/profile
Rank on Objectives:
• Minimize mass
• Minimize cost

6. Ranking on Objectives
• Minimize mass, cost… Minimize mass, cost…
• Maximise performance per unit of performance
Function & Each combination of:
Loading
Function
Tie in tension
Limiting Constraint
Constraint Objective
Panel in bending has a characteristic index
Stiffness specified Objective
Shaft in torsion Strength specified Minimum cost
 
M1   
Fatigue limit Minimum weight E
Column in compression
Geometry Max energy storage   
………. M2   1 3 
E 
………. Minimum
Mechanical, environmental impact
Thermal,
Electrical...
……….

7. Influence of Application on Material Choice
Low weight
Tensile Strut
 
Index (m)   
E 
Low alloy steel = 1
COMPOSITES METALS PLASTICS

8. Influence of Application on Material Choice
Low weight
Panel in Bending
  
Index (m)   1 3 
E 
Low alloy steel = 1
COMPOSITES METALS PLASTICS

9. Mass vs Cost trade-off
Low weight
Panel in Bending
  
Index (m)   1 3 
E 
Low alloy steel = 1
 .C m 
Index (c)   1 3 
E 

10. Hybrid Materials & Structures?
“A hybrid material is a combination of two or more materials in a pre-determined
configuration and scale, optimally serving a specific engineering purpose”
Kromm et al, 2002
Design variables:
 Choice of materials
 Volume fractions
 Configuration
 Connectivity
 Scale

11. Optimization of Hybrid Materials
All materials along
line exhibit same
value of the index:
1
E 3

quasi-
Materials with the
isotropic
highest value are
composite
optimal for the
application
Influence of adding different reinforcement types and loading levels to a magnesium alloy
Application = Lightweight stiff panel loaded in bending

12. Optimization of Hybrid Structures
All materials along
line exhibit same
value of the index:
1
E 3

Materials with the
highest value are
optimal for the
application
Orange: Sandwich panel, Mg-50% carbon fibre skins & 50kg/m3Mg octet lattice core
(Core thickness = 20mm, face sheet thickness = 0.05 – 5mm)
Yellow: Predicted performance of core & skin materials

13. Summary
Integration of material selection tools into typical design workflow
CES Selector
Design brief / requirements
Eco Audit
Tool
Material
Preliminary design concept CAD
Selection
Hybrid
Synthesizer
CAD, CAE
Detailed design Optimisation packages
• Evaluate different materials and
Prototype & testing
design concepts before committing
Increasing: expenditure
Time
Effort Final design LCA • Avoid problems associated with
Cost incorrect material choice
• Reduce development time

14. Thank You!