[email protected] ENGR-11_Lec-08_Chp5_Materials_Selection.ppt 1 Bruce Mayer, PE...

[email protected] • ENGR-11_Lec-08_Chp5_Materials_Selection.ppt1

Bruce Mayer, PE Engineering-11: Engineering Design

Bruce Mayer, PELicensed Electrical & Mechanical Engineer

[email protected]

Engineering 11

Materials

Selection



Materials Selection at Config

?

FormulationFormulation

Customer Needs

Customer requirementsImportance weightsEng. characteristicsHouse of QualityEng. Design Spec’s

Concept DesignConcept Design

Abstract embodiment Physical principlesMaterialGeometry Configurati

on DesignConfiguration Design



Matls & Manuf Closely Linked

Problem Formulation

Detail Design

Parametric Design

Configuration Design

Concept Designmaterials manufacturing

processes




Material Properties

ManufacturingProcesses

COMPATIBLEmaterials & processes

e.g.; Ceramics can NOT be WELDED




e.g.; CAST Parts can NOT have SHARP Corners


ProductGeometry

CAPABLE Processesfor the geometry



Matl↔Manf↔Geom Function

Material Properties


ProductGeometry

ProductFunction



Properties of Solid Materials

Mechanical: Characteristics of materials displayed when Forces or Moments are applied to them.

Physical: Characteristics of materials that relate to the interaction of materials with various forms of energy.

Chemical: Material characteristics that relate to the Material’s electron structure.

Dimensional: Size, shape, and finish



Material Properties Chemical Physical Mechanical Dimensional

Composition Melting Point Tensile properties Standard Shapes

Microstructure Thermal Toughness Standard Sizes

Phases Magnetic Ductility Surface Texture

Grain Size Electrical Fatigue Stability

Corrosion Optical Hardness Mfg. Tolerances

Crystallinity Acoustic Creep

Molecular Weight Gravimetric Compression

Flammability One More ≡ $COST, $COST, $COST



Solid-Materials Family Tree

CeramicsMetals Plastics Composites

Materials

Elastomers

Thermosets

Thermoplastics

Non-ferrous

Ferrous

Sub-family

See Also ENGR45



Solid-Materials Taxonomy

Metals

Materials

Ferrous Sub-family

Family

Classes

Cast ironCarbon steelAlloy steelStainless steel



Metals Family Tree

Non-ferrousFerrous (Mostly Iron)

Metals

aluminum brass bronze copper lead magnesium nickeltin titanium tungstenzinc

cast ironcarbon steelalloy steelstainless steel



Polymer (Plastics) Family Tree

ElastomersThermosetsThermoplastics

Polymers

butylfluorocarbonneoprenenitrilepolysulfiderubbersilicone

alkydepoxymelaminephenolicpolyesterurethane

ABSacetalacrylicnylonpolycarbonatepolyethylenepolypropylenepolystyrenevinyl



Ceramics & Composites Trees

CeramicsaluminaberylliadiamondmagnesiaSilicatesSilica carbideNitrideOxidezirconia

carbon fiberceramic matrixglass fiberKevlar fibermetal matrixpolymer matrix

Composites



Material Family ComparisonTable 1

Characteristics Metals Ceramics Polymers

strength strong strong –C weak – T

weak

elastic strength very some some

stiffness very very flexible

ductility ductile brittle ---

hardness medium hard soft

corrosion resistance poor good excellent

fatigue resistance good --- ---

conductivity (heat/electric) conductor insulator insulator

creep resistance good --- poor

impact resistance good poor good

density heavy medium light

temperature tolerance good super poor



Materials Selection Strategyprospective

materials and processes

screening

rating

rejected materials and

processes

best material(s) and

processes

functional?manufacturable?

relativeperformance?

feasiblematerials and

processes



Materials Selection The designer of any product, other than

software, must be part of the material selection process.

Only occasionally will the exact grade of material be specified by the customer.• Even then the designer

must UNDERSTAND the material to be able to design the product.



Decisions, Decisions!

So many materials, so much information.• How do we decide? • How do we even begin to choose?

– Metals are the DEFAULT as they have the widest variety of Manufacturing Processes

First we need to look at the function of the product • Use PRODUCT ANALYSIS



Product Analysis

Just what it says – analyze the product!• What does it do?• How does it do it?• Where does it do it?• Who uses it?• What should it cost?



Case Study BiCycle

What is the function of a bike – obvious? How does the function depend on the type

of bike?• Racing• Touring• Mountain • Commuter• Child’s



Case Study BiCycle (2)

How is it made to be easily maintained? What should it look like (colors etc.)? What should it cost?

• Child’s Bike VS. Professional Racing Bike

How has it been made comfortable to ride?

How do the mechanical parts work and interact?



Component or System?

1st problem is…….

Is a BiCycle one component or a system of components working together?

e.g.; a one-piece Bracket is a component, a Cordless Screwdriver is a system.



System Analysis

When we analyze a system we need to break the system down into individual components and then analyze each one for the best Matl.

CordLess ScrewDriver BreakDown

A Nice EXPLODED-View (Assembly) Drawing



System Analysis BiCycle

The bike breaks down (Not Literally, we hope) into various parts:• Frame & Forks• Wheels & Brakes• Seat & Peddles• Gears & Chain• Safety (reflectors)• etc.



System Analysis BiCycle

Now need to look at the following for each part:• Requirements (mechanical,

ergonomic, aesthetic etc.)• Function• How many are going to be made?• What manufacturing methods are we

going to use?



Manufacturing InterDependency

YES!...We have to actually MAKE it! This is a key question which has a

HUGE influence on materials selection.

e.g., what materials could we use for the FRAME?



Frame Material Candidates

Steel• Strong, stiff, HEAVY, Inexpensive,

Easy to Join

Aluminum• WEAKER, lighter, MORE EXPENSIVE

than steel, Hard to Join

Composite (CFRP) • strong, stiff, very light,

but MOST EXPENSIVE



Bike F

rame



Frame JointDetail

A Critical Manufacturing Process Detail• Weld?• Braze?• Shrink Fit?• Other?



Where do I find Materials data?

Textbooks Databooks Manufacturer’s

literature Internet Sites

• CurrentDefault– Most

DataBooksare OnLine



Textbooks

Good for general information Some have tables of properties Not good for detailed specifications

and properties. A useful starting

point



Databooks

One of the quickest sources of detailed information.

Usually contain grades and specifications as well as properties.

Small and perfectly formed – pocketbooks

Easy to navigate around



Manufacturer’s literature

Variable in quality and usefulness. Often only cover their products. Usually do not compare materials. Can be biased. Good for final selection before

ordering.



InterNet Sites

Can be a real minefield. Lots of poorly presented

information. Google searches bring up lots of

SuperFluous info. Hard to find technical information. Best to use non-commercial sites.



MatWeb.com is VERY Good for Props



Materials Selection Charts

Allow easy visualization of properties

Show lots of different materials Can be ‘drilled down’ to specifics Show balances of properties

e.g. strength vs cost Ideal for a first ‘rough cut’ selection



TradeOff Weight & Stiffness



Modulus - Density Chart

Modulus spans 5 orders of magnitude• 0.01 GPa for foams to 1000 GPa for

diamond

The charts therefore use logarithmic scales, where twice the distance means ten times the property value.

This makes it possible to show the full range on one chart,



TradeOff Weight & Strength



TradeOff Insulation & Expansion



Summary Matls Selection

1. Think about the design from ergonomic and functional viewpoint.

2. Decide on the materials to be used.

3. Choose suitable manufacturing processes that are also economic

Steps 2 & 3 may be iterative. Don’t forget the …………… NextSlide



Bigger Picture (don’t forget)

Is the product PERFORMANCE driven or COST driven?• This makes a

huge difference when choosing materials.– Kid’s bike vs.

Racing bike



Manufacturing Priority Although we usually choose

materials FIRST sometimes it is the SHAPE and PROCESS which is the limiting factor.• e.g.; Complex HiVacuum

Chambers almost always must be WELDED to form GasTight Seals– Limits Materials Selection

to METALS



Summary Materials Selection

Product function interdependence Mechanical properties Physical properties Families, sub, classes of materials TradeOff (Ashby) charts Materials first approach Process first approach



All Done for Today

AnotherAshbyChart



Bruce Mayer, PERegistered Electrical & Mechanical Engineer

[email protected]

Engineering 11

Appendix



What is an Ashby Chart? It’s a form of a picture that’s worth

well more than a 1000 words for any engineering designer. Named for Prof. M. F .Ashby, this is a tool that’s less widely used than it should be.

The chart involves plotting “clouds” on a 2-axis plot, with different variables on each axis. Sounds simple, but the impact doesn’t hit you till you actually see them, as in this example from Granta above:

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