-
8/10/2019 EIN 3390 Chap 9 Spring_2012
1/35
Chapter 9Material Selection
EIN 3390 Manufacturing ProcessesSpring, 2012
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
2/35
9.1 Introduction
Goal of manufacturing: to create products andcomponents that
perform properly.
Due to advances in materials science, there is awide array of
available materials
The increase in the number of choices hasoften led to improper
or poor materialsselection
Sometimes, a more expensive alloy is chosenwhen a cheaper alloy
would have been
sufficient
Design and material engineers have theresponsibilityof proper
materials selection.
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
3/35
Introduction
Material selection processes should beconstantly reevaluated
Materials selection concerns are always
changing Environmental pollution
Recycling
Energy
Health or safety constraints Geopolitical issues
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
4/35
Introduction
Materials in manyproducts havechanged over the
years
Figure 9-2a) (Left) A traditional two-wheel bicycleframe (1970s
vintage) made from joined segments
of metal tubing,
b) (Right) a top-of-the-line (Tour de France or
triathlon-type) bicycle with one-piece frame, made
from fiber-reinforced polymer-matrix composite.
(Courtesy of Trek Bicycle Corporation, Waterloo,
WI.)
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
5/35
9.2 Material Selection andManufacturing Processes Material
and
manufacturingprocesses are extremelyinterdependent
Changein a materialwill likely cause achange in themanufacturing
processneeded
A successful product hasgone through bothproper
materialselectionandprocessing selection
Figure 9-4Schematic showing theinterrelation among material,
properties,
processing, and performance.
(Material)
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
6/35
9.2 Material Selection andManufacturing Processes Material
and
manufacturingprocesses are extremelyinterdependent
Changein a materialwill likely cause achange in themanufacturing
processneeded
A successful product hasgone through bothproper
materialselectionandprocessing selection
Figure 9-4Schematic showing theinterrelation among material,
properties,
processing, and performance.
(Material)
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
7/35
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
8/35
Steps for Design
1. Conceptual Several concepts may be considered
2. Functional
Workable designs are developed Detailed plan for
manufacturing
Prototyping
3. Production
Full production Production speeds and quantities
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
9/35
9.4 Procedures for Material Selection
Generalsequence of product design designmaterial
selectionprocess
selectionproductionevaluationredesign
Case-history method
Evaluates what has been done in the past Modification of an
existing product
Evaluates the current product and manufacturingtechniques
Changes or improves upon features of the existing
product Development of a new product
Follows the full sequence of product design above
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
10/35
Geometric Considerations
Relative size Shape complexity Specified dimensions Precision
Component interaction Surface-finishes Tolerances
Tolerances due to environmental or usage concerns
Minor changes to improve manufacture orperformance
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
11/35
Mechanical Properties
Static strength Brittle fracture
Plastic deformation
Allowable bend, stretch, twist, orcompress
Impact loadings
Vibrations or cyclic loadings
Wear resistance Operating temperatures
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
12/35
Example: Cantilever Beam Design
design: equal strength
design: equal cross section
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
13/35
Physical Properties (Electrical,Magnetic, Thermal, and
Optical)
Electrical requirements Conductivity, resistivity
Magnetic
Thermal conductivity Thermal expansion
Optical requirements
Weight Appearance (color, texture, feel)
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
14/35
Environmental Considerations
Operating temperatures Corrosion Erosion
Lifetime Fatigue Expected level of maintenance Disassembly
Repairability Recyclability
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
15/35
Manufacturing Concerns
Quantity Production rate Level of quality
Quality control and inspection Assembly concerns Section
thickness Standard sizes and shapes Liability if product failure
occurs End-of-use disposal
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
16/35
Proper Materials Selection
All factors and service conditions must bemet
Absolute requirements
No compromise possible Relative requirements
Compromises can be made
Good, better, best are all acceptable
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
17/35
9.5 Additional Factors to Consider
Handbook data is valuable in determiningmaterials
Note the conditions under which values formaterials were
obtained
Costis often one of the biggest additional
factors Often, compromises between material propertiesand cost
must be made
Material availability Are there any possible misuses on the part
of
the consumer? Have there been failuresfor similar
products? Materials usage history Material standardization
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
18/35
9.6 Consideration of theManufacturing Process Overall
attractiveness
Physical properties
Mechanical properties
Formability
Economical concerns
All processes are not compatible with allmaterials
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
19/35
9.7 Ultimate Objective
Develop a combination of material andprocessesthat is the best
solution
Material or manufacturing selection
normally imposes restrictionsorlimitationson the other
Economics, environment, energy,efficiency, recycling,
inspection, and
serviceability are important decidingfactors
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
20/35
Decision Models
Figure 9-5Sequential flow chart showing activities
leading to the production of a part or product.
Figure 9-6Alternative flow chart showing
parallel selection of material and process.
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
21/35
Decision Models
Figure 9-5Sequential flow chart showing activities
leading to the production of a part or product.
Figure 9-6Alternative flow chart showing
parallel selection of material and process.
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
22/35
Compatibility
Figure 9-7Compatibilitychart of materials and
processes. Selection of a
material may restrict
possible processes.
Selection of a process may
restrict possible materials.
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
23/35
9.8 Materials Substitution
Care should be taken so that allrequirements are still met
The total picture should be considered so
that any possible compromises can bedetermined Aluminum sheets
have replaced steel forweight reduction, but vibration problems
require special design considerations
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
24/35
Material Substitutions
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
25/35
Material Substitutions
Causes of product failure Failure to know and use the best
materialsinformation
Failure to account for all reasonable materialuses
Use of materials with insufficient data
Inadequate quality control
Material selection made by unqualified people
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
26/35
9.10 Aids to Material Selection
There is an enormous amount of resourcesavailable for materials
selection Metals Handbook, published by ASM
InternationalASM Metals Reference Book Handbooks are available
for specific classes
of materials American Metal Market provides material
costs Materials Selection in Mechanical Designby
M. F. Ashby Computer software
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
27/35
Select a Material with Rating Chart
1. List all required material properties for a product to
bedesigned.
2. Screen all required properties and identify those
absoluteproperties that must be considered for the product
asGo-No-Go properties.
3. Rate each candidate material on a scale such as 1 to 5 or1 to
10 for each required property.
4. Define weighted factor for each required property basedon its
significance.
5. Multiply property rating by its weighted factor and sum
the results for each materials6. Select the material that
satisfies the Go-No-Go screen
and has the highest sum of the relative rating numbers.
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
28/35
Select a Material with Rating Chart
Material Go-No-Go Relative rating number - R(=rating number x
weighting factor)
R r R/r
Weldability Stiffness Stability Fatigue Tensile
1 4 5 4 14
A 14
B 14
C 14
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
29/35
Select a Material with Rating Chart
Advantages:
Potential materials can be compared ina uniform, unbiased
manner
The best candidate can often beselected
There is less chance to overlook amajor requirement by placing
all therequirement on a single sheet.
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
30/35
Example: Selection of a Material:
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
31/35
Solution: Finding Go-No-Go property: weldability
- S: satisfactory - U: unsatisfactory
Calculating: R = Relative rating number, and r =
weighting factor.
Relative rating number R = property rating number xweighting
factor
Set materials property rating number (1 5):
excellent = 5, very good = 4, good = 3, fair = 2,
poor = 1 weighted factor for each materials property:
- Stiffness : 1 - Stability: 4
- Fatigue: 5 - Tensile strength: 4
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
32/35
Solution (cont.)
Weldability Stiffness Stability Fatigue Tensile
Strength
SR Sr SR/Sr
Go-No-Go
screening
(1) (4) (5) (4)
X S 3x1 3x4 2x5 3x4 37 14 2.64
Y U 3x1 5x4 3x5 5x4 58 14 4.14
Z S 3x1 3x4 5x5 2x4 48 14 3.43
Rating chart for selecting material
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
33/35
Conclusion:
Based on the chart below, materialYhas the
highest rating number. However, because it
does not have satisfactory weldability and this is
an "absolute" requirement, it should not beselected. Material
Zshould be used.
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
34/35
Summary
Proper materials selection is vital to aproducts success
The design engineer and materials
engineer are responsible for materialsselection
Materials and process selection go hand-in-hand
Data should be used to validate materialsselection
-
8/10/2019 EIN 3390 Chap 9 Spring_2012
35/35
Homework:
Review questions: 7, 9, 12, 17
Problems: 1
