1. Progettazione di Materiali e Processi
Modulo 1 – Lezione 3
Progettazione e selezione di materiali e processi
A.A – 2016
Vanni Lughi

2. In the previous lecture…

3. Materials Data
Example of material property table
See CES

4. Materials Data
Example of comparison table
See CES

5. Materials Data
Example of single property graph
See CES

6. Materials Data
Example of two-property graph
See CES

7. The selection process All materials Screening: apply property limits
Innovative choices
Ranking: apply material performance indices
Subset of materials
Shortlisting: apply supporting information
Prime candidates
Final selection: apply local conditions
Final material choice

8. Function – Objectives - Constraints
What does the component do?
e.g.: support load, seal, transmit heat, bycicle fork, etc.
Objective
What do we want to maximize (minimize)?
e.g.: minimize cost, maximize energy storage, minimize weight, etc.
Constraints
What conditions must be met? (non-negotiable or negotiable)
e.g. geometry, resist a certain load, resist a certain environment, etc.
Implicit functions (e.g. tie, beam, shaft, column)
Constraints often translate to property limits (temperature, conductivity, cost, …)
Some constraints are more complex (e.g. stiffness, strength, etc.) as they are coupled with geometry -> need of a specific objective
Material indices help unravel such complexity

9. Functional requirements
Material indices
Performance = f (F, G, M)
Functional requirements
Material properties
Geometry
If separable:
Performance = f1(F) f2(G) f3(M)
Material index

10. Min. environmental impact
Material indices
Material index:
E/
Material index:
E0.5/
Function
Objective
Constraint
Tie
Beam
Shaft
Column
…..
Minimum cost
Max energy storage
Minimum weight
Min. environmental impact ……
Stiffness
Strength
Fatigue resistance
Geometry
…..
Material index:
/

11. In this lecture:
Examples of materials indexes for ties and beams
Example of ranking
Selection stategy
Examples of screening
Tables of solved problems of elasticity etc.
Table of momentum of intertia

12. Minimum weight design Tensile ties Main spar - beam Compression strut
Undercarriage- compression
The marked components of this plane perform different functions. The ties carry tension, the struts carry compression (they act as columns) and the beams carry bending moments. They are chose to be as light as possible: thus the objective is to minimize mass.
The mass of a tensile tie of prescribed strength depends two material properties – yield strength and density – in the combination; it is the material index for this component.
The mass of a strut that must carry a compressive load without buckling elastically is proportional to the material group so this becomes the material index.
The mass of a beam, loaded in bending, that must not yield plastically is proportional to the combination so that it the index.
Thus the index depends on the mode of loading (tension, compression, bending) and on the requirement for stiffness or strength.
The marked components of this plane perform different functions. The ties carry tension, the struts carry compression (they act as columns) and the spars carry bending moments – they are beams. They are chose to be as light as possible: thus the objective is to minimize mass.
The mass of a tensile tie of prescribed strength depends two material properties – yield strength and density – in the combination ; it is the material index for this component.
The mass of a strut that must carry a compressive load without buckling elastically is proportional to the material group so this becomes the material index.
The mass of a beam, loaded in bending, with restriction on elastic deflection is also proportional to so the index here is the same as that for the strut.
Thus the index depends on the mode of loading (tension, compression, bending) and on the requirement for stiffness or strength.
E = Young’s modulus
= Density
= Yield strength

13. Minimum cost design Structural Structural panels beam Tensile ties
The marked components of this building, like those of the plane, perform different functions. The ties carry tension, the struts carry compression (they act as columns) and the beams carry bending moments. They are chose to be as cheap as possible: thus the objective is to minimize cost.
The cost of a tensile tie of prescribed strength depends three material properties – yield strength, material cost per kg, and density – in the combination shown here; it is the material index for this component.
The cost of a strut that must carry a compressive load without buckling elastically is proportional to the material group involving yield strength, material cost per kg, and density shown. This becomes the material index.
Similarly, the cost of a beam, loaded in bending, that must not yield plastically is proportional to the combination shown here. It is the index.
Thus the index depends on the mode of loading (tension, compression, bending) and on the requirement for stiffness or strength.
Compression
strut (column)
Cm = Material cost / kg
= Density
= Yield strength

14. Criteria of excellence: material indices
Material index = combination of material properties that limit performance
Sometimes a single property
Sometimes a combination
Either is a material index
Stiffness Strength
Constraints
Objective
minimise mass
Explore these!
The material properties listed in handbooks – density, modulus and so on – are those that are measured to characterize the fundamental properties of materials – the physicists’ view of materials, one might say. The performance of an engineering component depends on the values of these, butit usually depends not on one property but on a combination of two or more – it is these that we call material indices. They, too, are material properties; they are the ones that characterize engineering performance – the engineers’ view of materials, so to speak. The ones highlighted in the red box of this frame all depend on density ρ and modulus E. They provide criteria of merit that allow the merit of a new hybrid to be assessed and compared with existing materials.
Remember this
one too! 14

15. Criteria of excellence: material indices
Material index = combination of material properties that limit performance
Sometimes a single property
Sometimes a combination
Either is a material index
Stiffness Strength
Constraints
Objective
minimise cost
Material cost/kg
The material properties listed in handbooks – density, modulus and so on – are those that are measured to characterize the fundamental properties of materials – the physicists’ view of materials, one might say. The performance of an engineering component depends on the values of these, butit usually depends not on one property but on a combination of two or more – it is these that we call material indices. They, too, are material properties; they are the ones that characterize engineering performance – the engineers’ view of materials, so to speak. The ones highlighted in the red box of this frame all depend on density ρ and modulus E. They provide criteria of merit that allow the merit of a new hybrid to be assessed and compared with existing materials. 15

16. Tables

17. Tables

18. Tables

19. Tables

20. Tables

21. Tables

22. Tables

23. Tables

25. Tables

26. Ranking, using charts Light stiff beam: Ceramics Composites E = ρ2 M2
0.1 10 1
100
Metals
Polymers
Elastomers
Woods
Composites
Foams
0.01
1000
100,000
10,000
Density ρ (kg/m3)
Young’s modulus E, (GPa)
Ceramics
Increasing M 2
Index
Rearrange:
E = ρ2 M2
Log E = 2 log  + 2 log M
Take logs:
We take the index M = E1/2/ρ as an example (E is modulus and ρ is density ). Rearranging and taking logs gives
Log(E) = 2Log(ρ) Log(M)
The schematic shows the chart used in Unit 2; its axes are Log(E) and Log(ρ). The equation describes a family of lines of slope 2, each corresponding to a value of M. Materials above the line have higher values of M than those below it; the ones above are the best choice. By moving the line upwards the number of materials above it decreases, narrowing the list of those that maximize performance. The other indices involving E and ρ can be shown on the same chart. The index M = E/ρ appears as a line of slope 1; that for M = E1/3/ ρ as a line of slope 3. They are used in the same way.
Function Index Slope
Tie
Beam
Panel

27. The chart-management tool bar
Box selection
tool
Cancel selection
Add text
Zoom
Add envelopes
Un-zoom
Black and white chart
Hide failed materials
Grey failed materials
Line selection
tool
Enter slope 1
Cancel OK
The chart management tool bar provides tools for
Exploring the chart by zooming into selected areas of it
Selection – applying a box or line selection, and removing it again
Customizing the chart – adding text labels, adding envelopes round the families of materials, making materials that have failed other selection stages appear in grey or disappear altogether.

28. Optimized selection using charts2 3 1
Search
area
This frame show index-based selection on a real property chart. The selection can be done using a hard copy chart, as illustrated here. The EduPack software gives greater flexibility, allowing the selection line to be moved and additional constraints to be applied. It lists, in the Results window, the materials that meet all the constraints and makes records for them immediately accessible. The list can be ranked by the value of any property used as a constraint or by the value of the index.
Here it is interesting to point out an interesting fact brought out by the method. Many components of aircraft are stiffness-limited – the wing spar is an example – and the objective here is to minimize mass. Materials texts often assert that, for aerospace, material with high specific modulus E/ρ are the best choice when stiffness is important. But aluminum and steel have the same value of specific stiffness, and steel is much cheaper that aluminum – so why are wing spars not made of steel? The answer is that they are loaded in bending, and then the correct criterion of choice is not E/ρ but E1/2/ρ . By that criterion aluminum is much better than steel, as the chart shows.
Results
22 pass
Material
Material
Material
etc...
Ranked
by Index

29. Plotting indices as bar charts
Browse
Search
Select
Tools
Bar chart of index
1. Selection data
Edu Level 2: Materials
List of properties
Density
Modulus
Yield strength
etc + - * / ^ ( ) (
Modulus ^
0.5 ) /
Density
X-axis
Y-axis
2. Selection Stages
Graph Limit Tree
Advanced
List of properties
Density
Modulus
Yield strength
etc
Indices can be plotted as bar-charts. Functions of properties, such as Young’s modulus / Density, E/ρ ,are plotted by selecting the axis (x or y) for the function and using the Advanced option in the Graph stage dialog box to create it, as shown here. On closing the dialog boxes, the function of properties is plotted on the chosen axis.
Results
22 pass
Material
Material
Material
etc...
Ranked
by Index

30. Plotting indices as functions
Index
This is a CES plot of the index E1/2/ρ. The materials captured in the red box have the highest values: magnesium alloys, aluminum alloys, CFRP and certain woods – the materials of aerospace, past and present.
Results
22 pass
Material
Material
Material
etc...
Ranked
by Index

31. Function – Objectives - Constraints
What does the component do?
e.g.: support load, seal, transmit heat, bycicle fork, etc.
Objective
What do we want to maximize (minimize)?
e.g.: minimize cost, maximize energy storage, minimize weight, etc.
Constraints
What conditions must be met? (non-negotiable or negotiable)
e.g. geometry, resist a certain load, resist a certain environment, etc.
Implicit functions (e.g. tie, beam, shaft, column)
Constraints often translate to property limits (temperature, conductivity, cost, …)
Some constraints are more complex (e.g. stiffness, strength, etc.) as they are coupled with geometry -> need of a specific objective
Material indices help unravel such complexity

32. CES Selection Toolbox Browse Select Search Tools 1. Selection data
Choice…
Select from
2. Selection Stages
Graph Limit Tree
Level 2: Materials
Custom
Define your own subset
Edu Level 1
Materials
Processes …..
Edu Level 2
Materials with Durability props
Materials with Eco properties
Plotting and selection tools
The CES Selection Toolbox is accessed as shown here. Clicking on the Select button in the toolbar activates a dialog box asking you to choose what Level (1, 2 or 3) and which Universe (Materials or Processes) you want to plot. This brings up the three selection tool:
Graph, allowing graphical selection
Limit, allowing selection by setting limits for material properties
Tree, allowing material selection to meet processing constraints.
The use of each tool is illustrated in the next three overheads, starting with a Limit stage.

33. Screening with a LIMIT STAGE
Young’s modulus GPa
Yield strength MPa
Hardness Vickers
Fracture toughness MPa.m1/2
Mechanical properties Min Max.
General properties
Thermal properties Min. Max.
Max service temp C
T-conductivity W/m.K
T-expansion /C
Specific heat J/kg.K
Electrical properties
Eco properties
Limit
200 1 10
1600
100 50 70 16
Ceramics
Metals
Foams
Polymers
Glasses
Insulator Thermal conductivity (W/m.K) Conductor
The frame illustrates screening using a Limit stage. A Limit stage applies numeric and discrete constraints. Required lower or upper limits for material properties are entered into the Limit stage property boxes. If a constraint is entered in the Minimum box, only materials with values greater than the constraint are retained. If it is entered in the Maximum box, only materials with smaller values are retained. The Results window at the lower left then lists the selection. The list can be ranked by the value of any one of the selected properties.
It is helpful, in setting the upper or lower limits for a property to know the range that the property spans for each material family. Clicking on the icon to the left of the Min. box generates a bar chart showing the property ranges.
Results
X out of 100 pass
Material
Material
Material
etc...
Ranking
Prop 1 Prop 2

34. Screening with a GRAPH STAGE
Line/gradient selection tool
Line selection
Enter slope 1
Cancel OK
Box selection tool
Property
Bar chart
Property 2
Property 1
Bubble chart
Graph 1
The use of the Graph facility to create bar charts and bubble charts was described in Unit 2. The tool bar that appears above a chart contains selection tools. Two are illustrated here.
A box selection isolates a chosen part of a chart. Any material bar or bubble lying in, or overlapping the box is selected; all others are rejected. The selected materials appear in the Results window, where they can be ranked by the value of the property.
A line selection divides a bubble chart into two regions. The user is free to choose the slope of the line, and to select the side on which materials are to be chosen. This allows selection of materials with given values of combinations of material properties such as E/ρ, where E is Young’s modulus and ρ is density. This is explained more fully in Unit 5. As before, the selected materials appear in the Results window where they can be ranked by either property or by the combination.
Graph stages can be combined with Limit stages (and with Tree stages, coming next) in any combination and any order. The Results window lists the materials that meet all the constraints, regardless of the way they are applied.
Results
X out of 100 pass
Material
Material
Material
etc...
Ranking
Prop 1 Prop 2

35. Screening with a TREE STAGE
Materials Universe
Ceramics and glasses
Hybrids: composites
Metals and alloys
Polymers and elastomers
Material Universe +
Trees
Selected records
Tree
Joining
Shaping
Surface treatment
Process Universe +
- Die casting
Shaping – Die casting
Results
X out of 100 pass
Material 1
Material 2
Material 3
etc...
Materials that
can be die-cast
A Tree stage allows the search to be limited to either:
a subset of materials, or
materials that can be processed in chosen ways.
Opening a Tree stage gives access to the tree-like hierarchical classification of materials (exactly as in the Browse window), or to the of processes. If any part of either tree is selected, only materials that belong to that subset of materials, or that can be processed in the chosen way, are retained.
A Tree stage can be combined with Limit stages and Graph stages in any combination and any order. The Results window lists the materials that meet all the constraints, regardless of the way they are applied.

36. Organizing information: the CES Edu database
Suppliers
data-table
References
Materials
data-table
DATA FOR
Metals & alloys
Polymers
Ceramics & glasses
Hybrids
Processes
data-table
DATA FOR
Joining
Shaping
Surface treatment
Links
Select on links
This overhead shows the structure of the CES EduPack database. It contains 4 linked data-tables:
Materials: metal, polymers, ceramics and hybrids
Processes for shaping, joining and finishing materials
References to more information about any given record in the data-tables
Supplier information for materials or processes.
Each record in the Materials data-table contains data for material properties, and is linked to similar records for the processes that can shape, join and finish it. Each record in the Process data-table is similarly linked to the materials it can treat and to reference and supplier information. This allows selection of materials by specifying required properties, or by specifying how it can be processed.

37. Materials for riot shields
Protective visor for law enforcers
Design requirement
Translation
Constraints
Transparent - of optical quality
Tough – high fracture toughness
Able to be molded
Young’s modulus GPa
Yield strength MPa
Fracture toughness MPa.m1/2
Mech. properties Min. Max.
Optical properties.
Opaque
Translucent
Transparent
Optical quality
Transparency
Limit stage
Plus graph stage
Best choice: Polycarbonate ?
Here is an example of how limit and graph stages can be combined during screening.