1. Strategic Thinking: Matching Material to Design
2/24/2019 2/24/2019
Strategic Thinking: Matching Material to Design
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2. Selection of materials and processes runs parallel with design process

3. New idea or working principle
New material may suggest a new product
New product may require a new material
Market need is put in terms of a need statement – “Devices is required to perform task X”
Product specification – detailed plan for new design

4. Three design stages between identifying the market need and developing a product specification
Information about materials is needed at each stage, but at very different levels of breadth and precision

5. Improving a current design while keeping the working principle on which it operates and many of its components
Why?
Product recall
Poor value for money
Inadequate profit margin
Stay ahead of competition

6. Three Concepts: Removal by axial traction (a)
Need Statement: A device is required to allow access to wine in a corked bottle with convenience, at modest cost, and without contaminating the wine
Three Concepts:
Removal by axial traction (a)
Removal by torsional traction (b)
Push it out from below (c)

7. Detailed drawings of the lever mechanism of (b) shown
– part dimensioned and the surface finish
- material and manufacturing route defined
– (d) show sketches based on concept of removal by axial tractions – shows the layout, mechanism and scale

8. The selection of a material begins with a catalog of all materials, which is narrowed by screening out those that fail to meet the design requirements
Concept stage
Designer requires only approximate property values, but for widest range of material
Embodiment stage
Data needed for a subset of materials, but at a higher level of detail and precision
Detail stage
Even higher level of detail and precision, but for few materials

9. To make a shape, a material is subjected to processes that, together, are called manufacture
Process selection is influenced by the material – its formability, its machinability, its weldability, its capacity for heat treatment, etc.
Process selection is influenced by the requirement for shape – the process determines the shape, size, precision, and greatly contributes to the cost

10. Two-Way Interactions:
Specification of shape restricts the choice of material and process
Specification of process limits the materials you can use and the shape they can take

11. Select the best match between the attribute profiles of the materials and processes and those required by the design
4 Step Process
Translation
Screening
Ranking
Documentation

12. This is accomplished by identifying the following:
Converting the design requirements into a prescription for selecting a material
This is accomplished by identifying the following:
Function
What does the component do?
Constraints
What non-negotiable conditions must the material meet?
Objectives
What aspects of performance must be maximised or minimised
Free Variables
What parameters of the problem is the designer free to change?

13. Constraint Objective Common Constraints Common Objectives
Essential condition that must be met, usually expressed as a limit on a material or process attribute
Objective
Quantity for which an extreme value is sought
Common Constraints
Common Objectives
Meet a target value of:
Minimise:
Stiffness
Cost
Strength
Mass
Fracture toughness
Volume
Thermal conductivity
Impact on Environment
Electrical resistivity
Heat loss
Magnetic permanence
Optical transparency
Maximise:
Energy storage
Heat flow

14. Example
The figure shows the level for a corkscrew. It is loaded in bending. It must be used without deflecting to a noticeable amount which means it must have a high modulus E. It must not bend permanently which means a high yield strength σy. And it must not snap off, which means it must have enough fracture toughness K1c. Finally, it must not corrode in wine or water.
Given the above, the lever should be as cheap as possible.
Formulate the translation.

15. Answer: Translation for corkscrew lever
Function
Lever (beam loaded in bending)
Constraint type
Constraints
Stiff enough
Functional
Strong enough
Some toughness
Resist corrosion in wine and water
Length L given
Geometric
Objective
Minimise cost
Free Variable
Choice of material
Choice of cross-section area