MECH4301 2008 Lecture 1 The Basics 1/22 MECH4301 2008 Materials Selection in Mechanical...

MECH4301 2008 Lecture 1 The

Basics 1/22

MECH4301 2008 Materials Selection in Mechanical (Engineering) Design

Lecture 1 Materials Selection:

Exploring the World of Materials


Basics 2/22

The evolution of Engineering Materials (Ashby, 2005)

Unit 1, Frame 1.2


Basics 3/22

The World of Engineering Materials

CompositesSandwiches

HybridsLattices

Segmented

PE, PP, PCPS, PET, PVC

PA (Nylon)

PolymersPolyesterPhenolic

Epoxy

Soda glassBorosilicate

GlassesSilica glass

Glass ceramic

IsopreneButyl rubber

ElastomersNatural rubber

SiliconesEVA

AluminaSi-carbide

CeramicsSi-nitrideZiconia

SteelsCast ironsAl-alloys

Metals, alloysCu-alloysNi-alloysTi-alloys

Materials: not just monolithic or simple

fibre composites!

Many additional issues : shape, cost, machinability,

environmental impact vs mechanical performance,

etc.


Basics 4/22

Mechanical properties illustrated (Ashby, 2005) Stiff

StrongToughLight

Not stiff enough (need bigger E)

Not strong enough (need bigger y )

Not tough enough (need bigger Kic)

Too heavy (need lower )

All OK !

Need to improve on the selection of

materials


Basics 5/22

Intro to the course’s main tool: CES Selector software package


Basics 6/22

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

2000300040005000600070008000

A material record

Attributes

Density

Mechanical props.

Thermal props.

Electrical props.

Optical props.

Corrosion props.

Supporting information

-- specific

-- general

Density

Mechanical props.

Thermal props.

Electrical props.

Optical props.

Corrosion props.

Supporting information

-- specific

-- general

Structured

information

Unstructured

information


Basics 7/22

Example of material record: Structured information for ABS*

General PropertiesDensity 1.05 - 1.07 Mg/m^3Price 2.1 - 2.3 US $/kg

Mechanical PropertiesYoung's Modulus 1.1 - 2.9 GPaElastic Limit 18 - 50 MPaTensile Strength 27 - 55 MPaElongation 6 - 8 %Hardness - Vickers6 - 15 HVEndurance Limit 11 - 22 MPaFracture Toughness 1.2 - 4.2 MPa.m1/2

Thermal PropertiesMax Service Temp 350 - 370 KThermal Expansion 70 - 75 10-6/KSpecific Heat 1500 - 1510 J/kg.KThermal Conductivity 0.17 - 0.24 W/m.K

Acrylonitrile-butadiene-styrene (ABS) - (CH2-CH-C6H4)n

Electrical PropertiesConductor or insulator? Good insulator

Optical PropertiesTransparent or opaque? Opaque

Corrosion and Wear ResistanceFlammability AverageFresh Water GoodOrganic Solvents AverageOxidation at 500C Very PoorSea Water GoodStrong Acid GoodStrong Alkalis GoodUV GoodWear Poor

*Using the CES Level 2 DB

+ links to processes


Basics 8/22

Example of material record: Unstructured information for ABS*What is it? ABS (Acrylonitrile-butadiene-styrene ) is tough, resilient,

and easily molded. It is usually opaque, although some grades can now be transparent, and it can be given vivid colors. 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 color well. Integral metallics are possible (as in GE Plastics' Magix.) ABS is UV resistant for outdoor application if stabilizers are added. It is hygroscopic (may need to be oven dried before 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. The acrylonitrile 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 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; plumbing hardware; automobile grilles; wheel covers; mirror housings; refrigerator liners; luggage shells; tote trays; mower shrouds; boat hulls; large components for recreational vehicles; 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 CES Level 2 DB


Basics 9/22

CES : the 3 levels

Level 1 1st year students: Engineering and Materials Science.

64 materials, 60 processes

Who is it for?

Level 2 2nd - 4th year students of Engineering and Materials Science and Design.

91 materials, 68 processes

Level 3 4th year, masters and research students of Engineering Materials and Design.

Technical data for 3000 materials and 200 processes.

Level 2 enough for most exercises


Basics 10/22

ABS: General PropertiesDensity 1.05 - 1.07 Mg/m^3Price 2.1 - 2.3 US $/kg

Mechanical PropertiesYoung's Modulus 1.1 - 2.9 GPaElastic Limit 18 - 50 MPaTensile Strength 27 - 55 MPaElongation 6 - 8 %Hardness - Vickers 6 - 15 HVEndurance Limit 11 - 22 MPaFracture Toughness 1.2 - 4.2 MPa.m1/2

Thermal PropertiesMax Service Temp 350 - 370 KThermal Expansion 70- 75 10-6/KSpecific Heat 1500 - 1510 J/kg.KThermal Conductivity 0.17 - 0.24 W/m.K

Charts: Relationships, perspective and comparisons

Metals Polymers Ceramics Hybrids

PEEK

PP

PTFE

WC

Alumina

Glass

CFRP

GFRP

Fibreboard

Yo

un

g’ s

mo

du

lus,

GP

a

Steel

Copper

Lead

Zinc

Aluminum

For these we need

Material bar-charts

Material property charts

Data sheets do not allow comparison,

perspective.


Basics 11/22

UntitledMaterials:\MET ALS Materials:\POLYMERS Materials:\CERAMICS and GLASSES Materials:\COMPOSIT ES

Yo

un

g's

Mo

du

lus

(GP

a)

1e-004

1e-003

0.01

0.1

1

10

100

1000

Low alloy steel

Mg-alloys

Al-alloysZn-alloys

Ti-alloys

Cu-alloys

Stainless steelHigh carbon steel

Acetal, POM

Polyurethane

EVA

Ionomer

PTFE

WC

Alumina

Glass Ceramic

Silica glass

Soda-Lime glassPolyester, rigid

PC

PS

PUR

PE

ABS

PP

BCSiC

Al-SiC Composite

CFRP

KFRP

GFRP

Plywood

Neoprene

Natural Rubber (NR)

CompositesPolymersMetals Ceramics & glass

You

n g’s

mo d

u lu s

(G

Pa )

Metals Polymers Ceramics Hybrids

Bar- chart created with CES (Level 1)

Bar Charts allow exploring relationships

Bar Charts allow selection and sorting

Materials with E > 100 GPa


Basics 12/22

Material Property Chart from pdf file (available from Bb)

E

density

Questions:

Why the enormous differences?

Why are metals here and polymers here?

Bonding, packing.


Basics 13/22

Chart created with the CES software (level 1, 60 materials)

Density (kg/m^3)100 1000 10000

Youn

g's

mod

ulus

(G

Pa)

1e-3

0.01

0.1

1

10

100

Rigid Polymer Foam (HD)

Flexible Polymer Foam (VLD)

Silicone elastomers

Polyvinylchloride (tpPVC)

Wood, typical along grain

Tungsten carbidesAlumina

Silicon

Zinc alloys

Lead alloys

Tungsten alloys

Concrete

Brick

CFRP, epoxy matrix (isotropic)

Rigid Polymer Foam (MD)

Rigid Polymer Foam (LD)

Cork

Polychloroprene (Neoprene, CR)

Leather

Wood, typical across grain

E

density


Basics 14/22

Chart created with the CES software (level 3, ~3400 materials)

Density (kg/m^3)10 100 1000 10000

Youn

g's

mod

ulus

(G

Pa)

1e-5

1e-4

1e-3

0.01

0.1

1

10

100

1000

Melamine Foam

Ethylene-Propylene Rubber (EPM)

Silicone elastomer (Shore A40)

Diamond

Balsa (l) (ld)

Leather

Tin-Lead 63-37 Solder

Metal Impregnated Carbon

Silicone elastomer

Polyurethane Foam

Polymethacrylimide Foam:

Palm (0.35)

E

density


Basics 15/22

Chart created with the CES software (level 3, Material Families)

Density (kg/m^3)10 100 1000 10000

Youn

g's

mod

ulus

(G

Pa)

1e-5

1e-4

1e-3

0.01

0.1

1

10

100

1000

Melamine Foam

Ethylene-Propylene Rubber (EPM)

Silicone elastomer (Shore A40)

Diamond

Balsa (l) (ld)

Leather

Tin-Lead 63-37 Solder

Metal Impregnated Carbon

Silicone elastomer

Polyurethane Foam

Polymethacrylimide Foam:

Palm (0.35)

Epoxy Resin (Flexibilized)

E

density


Basics 16/22

Materials that are stiff?

Charts offer both Methods and ToolsAt this stage you have a selection tool.

Charts help developing a perspective

• Materials that are light and compliant?

• Materials that are light and stiff?

=> There is more to them : Charts enable quantitative sorting and selection


Basics 17/22

Example Q 3.4 Tute 1

Minimun specific stiffness


Basics 18/22

Modulus - density chartE/ = 23 => = 1 =>

E =23

Metals with E >100 GPaE/ > 23 GPa/(Mg m-3)

Search area: Steels, Nickel alloys, Titanium

alloys


Basics 19/22

Example Q 3.4 Tute 1, solution:


Basics 20/22

Example Q 3.5 Tute 1

E1/3/ >3 => E = 33 3 => Log (E) = 3 Log () + 3 Log (3)

then Log (E) = 0 + 3 Log (3)

=> E = 33 = 27

Selection line (slope 3) runs through point:

( = 1; E = 27 GPa)

set = 1 => Log(1) =0


Basics 21/22

Selection line (slope 3) runs through point ( = 1; E = 27 GPa)

Search area: CFRP

BoronCarbide (B4C)


Basics 22/22

Example Q 3.5 Tute 1: solution


Basics 23/22

The End


Basics 24/22

Modulus - density chartE

E

CR

Modulus- relative cost chart (relative to iron)

Why do we

plot CR

instead of

just CR?


Basics 25/22

Modulus- production energy chart ( embodied energy)

Why do we plot

Hq instead of

just Hq ?

E

Hq


Basics 26/22

Mass m (kg) proportional to density, (kg/m-3) COST: Cost per unit mass c ($/kg) Total cost, C ($), for mass m The Total Cost C is proportional to c ($/m3)

( c = “cost” density)

Hq = production energy per unit mass (MJ/kg)

The total production energy Q

The total Q is proportional to Hq (MJ/ m3)

( Hq = density of “production energy”)

ccVcmC

Vm

q HHVHmQ

qq

Tute 1, Exercises 19 and 21)

Why do we plot CR and Hq instead of just

CR or Hq ?

MECH4301 2008 Lecture 1 The Basics 1/22 MECH4301 2008 Materials Selection in Mechanical...

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