4-Materials Selection Basics (1)

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New approaches to Materials Education- a course authored byMike Ashby and David Cebon, Cambridge, UK, 2005

The CESEduPackThe CESEduPackUniversity ofCambridge

Unit 1. Materials Selection:

exploring the world of materials


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Outline

Resources:

Materials Selection in Mechanical Design, 3rd edition (The Text) by M.F. Ashby,

Butterworth Heinemann, Oxford, 2005, Chapters 1 - 4.

CESEduPack 2009 software (www.grantadesign.com).

Background: the motivation

History -- the evolution of materials

Materials and their attributes

The nature of materials data

Exploring relationships: material property charts


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Teaching materials to engineering students

Engineers make things. They make them out of materials.

The philosophy

The CES EduPack provides the resources to achieve this. It introduces

students to a resource they can use in their later profession (like CAD or FEtools)

What do they need to know to do this successfully?

A perspective of the world of materials and processes (understanding)

An ability to select those that best meet requirements of a design (methods)

Access to information and tools to facilitate selection


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History the evolution of materials


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The world of materials

CompositesSandwiches

HybridsLattices

Segmented

PE, PP, PCPS, PET, PVC

PA (Nylon)

PolymersPolyesterPhenolic

Epoxy

Soda glass

Borosilicate

GlassesSilica glass

Glass ceramic

IsopreneButyl rubber

ElastomersNatural rubber

SiliconesEVA

Alumina

Si-carbide

CeramicsSi-nitrideZiconia

Steels

Cast ironsAl-alloys

Metals, alloysCu-alloysNi-alloys

Ti-alloys

100,000 -150,000 commercial materials!



Organising information: the MATERIALS TREE

Kingdom

Materials

Family

Ceramics& glasses

Metals& alloys

Polymers& elastomers

Hybrids

Class

Steels

Cu-alloys

Al-alloys

Ti-alloys

Ni-alloys

Zn-alloys

Member

1000

2000

3000

4000

50006000

7000

8000

A material record

Attributes

Density

Mechanical props.

Thermal props.

Electrical props.

Optical props.

Corrosion props.

Supporting information

-- specific

-- general

Structured

information

Unstructured

information



Structured information for ABS*

General PropertiesDensity 1.05 - 1.07 Mg/m^3

Price 2.1 - 2.3 US $/kg

Mechanical PropertiesYoung's Modulus 1.1 - 2.9 GPa

Elastic Limit 18 - 50 MPa

Tensile Strength 27 - 55 MPa

Elongation 6 - 8 %

Hardness - Vickers 6 - 15 HV

Endurance Limit 11 - 22 MPa

Fracture Toughness 1.2 - 4.2 MPa.m1/2

Thermal Properties

Max Service Temp 350 - 370 KThermal Expansion 70 - 75 10-6/K

Specific Heat 1500 - 1510 J/kg.K

Thermal Conductivity 0.17 - 0.24 W/m.K

Acrylonitrile-butadiene-styrene (ABS) - (CH2-CH-C6H4)nElectrical PropertiesConductor or insulator? Good insulator

Optical PropertiesTransparent or opaque? Opaque

Corrosion and Wear ResistanceFlammability AverageFresh Water Good

Organic Solvents Average

Oxidation at 500C Very Poor

Sea Water Good

Strong Acid Good

Strong Alkalis Good

UV Good

Wear Poor

*Using the CESLevel 2 DB

+ links to processes



Unstructured information for ABS*

What is it? ABS (Acrylonitrile-butadiene-styrene ) is tough, resilient, and easily molded. Itis usually opaque, although some grades can now be transparent, and it can be given vividcolors. ABS-PVC alloys are tougher than standard ABS and, in self-extinguishing grades, are

used for the casings of power tools.Design guidelines. ABS has the highest impact resistance of all polymers. It takes colorwell. Integral metallics are possible (as in GE Plastics' Magix.) ABS is UV resistant foroutdoor application if stabilizers are added. It is hygroscopic (may need to be oven driedbefore thermoforming) and can be damaged by petroleum-based machining oils.

ABS can be extruded, compression moulded or formed to sheet that is then vacuum thermo-formed. It can be joined by ultrasonic or hot-plate welding, or bonded with polyester, epoxy,isocyanate or nitrile-phenolic adhesives.

Technical notes. ABS is a terpolymer - one made by copolymerising 3 monomers: acrylonitrile, butadiene and syrene. Theacrylonitrile gives thermal and chemical resistance, rubber-like butadiene gives ductility and strength, the styrene gives a glossy surface,ease of machining and a lower cost. In ASA, the butadiene component (which gives poor UV resistance) is replaced by an acrylic ester.Without the addition of butyl, ABS becomes, SAN - a similar material with lower impact resistance or toughness. It is the stiffest of thethermoplastics and has excellent resistance to acids, alkalis, salts and many solvents.

Typical Uses. Safety helmets; camper tops; automotive instrument panels and other interior components; pipe fittings; home-securitydevices and housings for small appliances; communications equipment; business machines; plumbing hardware; automobile grilles;

wheel covers; mirror housings; refrigerator liners; luggage shells; tote trays; mower shrouds; boat hulls; large components for recreationalvehicles; weather seals; glass beading; refrigerator breaker strips; conduit; pipe for drain-waste-vent (DWV) systems.

The environment. The acrylonitrile monomer is nasty stuff, almost as poisonous as cyanide. Once polymerized with styrene it

becomes harmless. ABS is FDA compliant, can be recycled, and can be incinerated to recover the energy it contains.

*Using the CESLevel 2 DB



Organising information: the PROCESS TREE

Kingdom

Processes

Family

Joining

Shaping

Surfacing

Class

Casting

Deformation

Moulding

Composite

Powder

Rapid prototyping

Member

Compression

Rotation

Injection

RTM

Blow

Attributes

A process record

Material

Shape

Size Range

Min. section

Tolerance

Roughness

Economic batch

Supporting information

-- specific

-- general

Structured

information

Unstructured

information


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The EduPack

Engineering textSoftware Industrial design text

Resource books, exercisesand worked solutions

PowerPoint lectures


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The CES Software

Level 1

1st year students:Engineering,Materials Science,Design

64 materials

75 processes

Level 2

2nd - 4th year studentsof Engineering andMaterials Science andDesign.

91 materials

107 processes

Level 3

4th year, masters andresearch students ofEngineering Materialsand Design.

2916 materials

233 processes

Specialist DBs

Eco design

Mil handbook 5 and 17

Campus and IDES.


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Finding information with CES

Choose what you want to explore(materials, processes..)

Find what?

Which table?

Processes

Casting

Moulding

Powder

etc

Data

tableMaterials

Metals

Polymers

Ceramics

etc

Data

table

Browse Select SearchToolbar Print Search web

Links


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Property

Demo -- creating charts

New

Graph stage

Limit stage

Tree stage

Browse Select Search Print Search webToolbar

Prop

erty

2

Property 1

Select what? Materials, Level 1


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Relationships, perspective and comparisons

Metals Polymers Ceramics Hybrids

PEEK

PP

PTFE

WC

Alumina

Glass

CFRP

GFRP

Fibreboard

Steel

Copper

Lead

Zinc

Aluminum

Material bar-charts

Material property charts

Data sheets do not allow comparison,

perspective. For these we need


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Material property- charts: modulus - density

0.1

10

1

100

Metals

Polymers

Elastomers

Ceramics

Woods

Composites

Foams

0.01

1000

1000.1 1 10

Density (Mg/m3)

Youngsmodu

lusE,

(GPa)


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Mechanical properties

Why the differences?

Atom size and weight

Bonds as (linear) springs

Spring constant for variousbond types.

Manipulating properties

Making composites

Making foams


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Thermal properties

Why the differences?

Bonds as non-linear springs

10% expansion at meltingpoint, so expansion goesinversely as Tm

Thermal energy as atomvibration, propagates aswaves, scattered by obstacles

Manipulating properties

High conductivity: purity

Low conductivity, obstaclesand foams

P idi h d d l


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Materials that are light and stiff?

Providing methods and tools

At this stage students have a tool.

Materials with low expansion?

Develops a perspective

with high conductivity?

D R t iti


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Demo -- Report writing

Open project

Save project

Print .

File

Copy

Paste.

Edit

What is it? ABS (Acrylonitrile-butadiene-styrene ) is tough, resilient, and easilymolded. It is usually opaque, although some grades can now be transparent, and itcan be given vivid colors. ABS-PVC alloys are tougher than standard ABS and, inself-extinguishing grades, are used for the casings of power tools.

Design guidelines. ABS has the highest impact resistance of all polymers. Ittakes color well. Integral metallics are possible (as in GE Plastics' Magix.) ABS is UVresistant for outdoor application if stabilizers are added. It is hygroscopic (may needto be oven dried before thermoforming) and can be damaged by petroleum-basedmachining oils.

ABS can be extruded, compression moulded or formed to sheet that is then vacuumthermo-formed. It can be joined by ultrasonic or hot-plate welding, or bonded withpolyester, epoxy, isocyanate or nitrile-phenolic adhesives.

Technical notes. ABS is a terpolymer - one made by copolymerising 3 monomers: acrylonitrile, butadiene and syrene. Theacrylonitrile gives thermal and chemical resistance, rubber-like butadiene gives ductility and strength, the styrene gives aglossy surface , ease of machining and a lower cost. In ASA, the butadiene component (which gives poor UV resistance) isreplaced by an acrylic ester. Without the addition of butyl, ABS becomes, SAN - a similar material with lower impactresistance or toughness. It is the stiffest of the thermoplastics and has excellent resistance to acids, alkalis, salts and many

solvents.Typical Uses. Safety helmets; camper tops; automotive instrument panels and other interior components; pipe fittings;home-security devices and housings for small appliances; communications equipment; business machines; plumbinghardware; automobile grilles; wheel covers; mirror housings; refrigerator liners; luggage shells; tote trays; mower shrouds; boathulls; large components for recreational vehicles; weather seals; glass beading; refrigerator breaker strips; conduit; pipe fordrain-waste-vent (DWV) systems.

The environment. The acrylonitrile monomer is nasty stuff, almost as poisonous as cyanide. Once polymerized withstyrene it becomes harmless. ABS is FDA compliant, can be recycled, and can be incinerated to recover the energy itcontains.

Th i i t


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The main points

The data take two broad forms:

(a) numeric, non-numeric data that can be structured in a uniformway for all materials

(b) supporting information, best stored as text and images

Classification allows materials data to be organized and retrieved

Visual presentation of data as bar-charts and property (bubble) chartsreveals relationships and allows comparisons

The CES EduPack allows rapid access to information, and ability tomake charts


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Documents

4-Materials Selection Basics (1)