1. © 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

2. © MFA and DC 2007 This Unit Unit 4 This Unit Outline Step 2Screening: eliminate materials that cannot do the job Step 3Ranking: find the materials that do the job best Step 4Documentation: explore pedigrees of top-ranked candidates Step 1Translation: 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

3. © 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 Rank All materials Increasing constraints 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…..)

4. © MFA and DC 2007 Need – Concept -- Embodiment Concepts Need Embodiments Direct pull Levered pull Spring assisted pull Geared pull

5. © MFA and DC 2007 Embodiment -- Detail

6. © 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

7. © 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

8. © 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 Objectives What 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

9. © 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 sink Keep chips below 200 C without any electrical coupling. Design requirements

10. © MFA and DC 2007 A Limit stage Screening using a LIMIT STAGE Browse SelectSearch PrintSearch web Screening: “Eliminate materials that can’t do the job” 2. Selection Stages Graph Limit Tree 1. Selection data Edu 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

11. © MFA and DC 2007 200 0 C Screening using a GRAPH STAGE Browse SelectSearch PrintSearch web File Edit View Select Tools Don’t need numbers! 1. Selection data Edu 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 & elastomers Composites Foams 10 30 1 10 10 20 Ceramics 10 1 100 0.01 Electrical resistivity ( .cm) T-conductivity (W/m.s) Max service temp. (K) Metals Polymers Ceramics Composites 2. Selection Stages Graph Limit Tree

12. © 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 K 1c > that of PS 3. Optically clear 4. Can be recycled

13. © 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 SelectSearch PrintSearch web 1. Selection data Edu Level 2: Materials Process Join Shape Surface Cast Deform Mold Composite Powder Prototype Tree stage for process Results X out of 95 pass Material 1 Material 2 Material 3 Material 4 etc...

14. © MFA and DC 2007 Stacking selection stages Property Stacked stages Browse SelectSearch PrintSearch web 1. Selection data Edu Level 2: Materials Density Modulus Strength T-conduction 2 100 10 200 Min Max Process Join Shape Surface Cast Deform Mold Composite Powder Prototype 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

15. © MFA and DC 2007 Optical properties Transparency Eco properties Recycle Optical quality Transparent Translucent Opaque 3 Tree stage: injection mold 1 Fracture toughness 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 K 1c > that of PS 3. Optically clear 4. Can be recycled

16. © 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 sheets Handbooks Material portals Trade associations Documentation: the “pedigree” of surviving candidates

17. © MFA and DC 2007 Documentation with CES Browse SelectSearch Print Results X out of 94 pass Material 1 Material 2 Material 3 Material 4 Material 5 ……….. Search web Matdata.net Searches information sources for selected record 1. Selection data Edu Level 2: Materials 2. Selection Stages Graph Limit Tree Open the record

18. © MFA and DC 2007 These are often 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

19. © MFA and DC 2007 Pause for demo

20. © 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

21. © 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 Now add Stage 3 – next page

22. © 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 3. Results: 15 of 95 pass Name Price (USD/kg) Polypropylene (PP)1.41 - 1.62 Soda-lime glass1.41 - 1.659 Polystyrene (PS)1.476 - 1.574 Polyvinylchloride (tpPVC)1.6 - 2.2 Polyethylene terephthalate (PET)1.608 - 1.769 Polyethylene (PE)1.718 - 1.89 Polyoxymethylene (Acetal, POM) 2.203 - 2.732 Polymethyl methacrylate 2.335 - 2.569 Acrylonitrile butadiene styrene (ABS)2.511 - 2.952 Polyamides (Nylons, PA)3.194 - 3.569 Polycarbonate (PC)3.6 - 4.47 Polylactide (PLA)3.667 - 4.584 Polyurethane (tpPUR)3.723 - 4.45 Cellulose polymers (CA)3.921 - 4.313 Polyetheretherketone (PEEK) 99.14 - 109

23. © MFA and DC 2007 End of Unit 3