Chapter 9
Material Selection
(Review)
EIN 3390
Manufacturing Processes
Summer A, 2012
9.1 Introduction

Goal of manufacturing: to create products
and components that perform properly

Material selection processes should be
constantly reevaluated
Materials selection concerns are always
changing
◦ Environmental pollution
◦ Recycling
◦ Energy
◦ Health or safety constraints
◦ Geopolitical issues

9.2 Material Selection and
Manufacturing Processes
Material and
manufacturing
processes are extremely
interdependent
 Change in a material
will likely cause a
change in the
manufacturing process
needed
 A successful product has
gone through both
proper material
selection and
processing selection

Figure 9-4 Schematic showing the
interrelation among material, properties,
processing, and performance.
9.2 Material Selection and
Manufacturing Processes
Material and
manufacturing
processes are extremely
interdependent
 Change in a material
will likely cause a
change in the
manufacturing process
needed
 A successful product has
gone through both
proper material
selection and
processing selection

Figure 9-4 Schematic showing the
interrelation among material, properties,
processing, and performance.
9.3 The Design Process

Design is the first stage in
manufacturing processes
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What it is
What properties must it possess
What material
How to make it
How many to make
What conditions will it see during use
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
9.4 Procedures for Material
Selection

General sequence of product design
◦ design→material selection→process
selection→production→evaluation→redesign

Case-history method
◦ Evaluates what has been done in the past

Modification of an existing product
◦ Evaluates the current product and manufacturing
techniques
◦ Changes or improves upon features of the existing
product

Development of a new product
◦ Follows the full sequence of product design above
Factors for Materials Selections
Geometric
 Mechanical Properties
 Physical Properties (Electrical, Magnetic,
Thermal, and Optical)
 Environmental Considerations
 Manufacturing Concerns

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Quantity
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
9.5 Additional Factors to Consider

Cost is often one of the biggest additional
factors
◦ Often, compromises between material properties
and cost must be made

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Material availability
Are there any possible misuses on the part
of the consumer?
Have there been failures for similar
products?
Material’s usage history
Material standardization
9.6 Consideration of the
Manufacturing Process

Overall attractiveness
◦ Physical properties
◦ Mechanical properties
◦ Formability
Economical concerns
 All processes are not compatible with all
materials

9.7 Ultimate Objective
Develop a combination of material and
processes that is the best solution
 Material or manufacturing selection
normally imposes restrictions or
limitations on the other
 Economics, environment, energy,
efficiency, recycling, inspection, and
serviceability are important deciding
factors

Decision Models
Figure 9-5 Sequential flow chart showing activities
leading to the production of a part or product.
Figure 9-6 Alternative flow chart showing
parallel selection of material and process.
Decision Models
Figure 9-5 Sequential flow chart showing activities
leading to the production of a part or product.
Figure 9-6 Alternative flow chart showing
parallel selection of material and process.
Compatibility
Figure 9-7 Compatibility
chart of materials and
processes. Selection of a
material may restrict
possible processes.
Selection of a process may
restrict possible materials.
Material Substitutions
Material Substitutions

Causes of product failure
◦ Failure to know and use the best materials
information
◦ Failure to account for all reasonable material
uses
◦ Use of materials with insufficient data
◦ Inadequate quality control
◦ Material selection made by unqualified people
Select a Material with Rating Chart
1.
2.
3.
4.
5.
6.
List all required material properties for a product to be
designed.
Screen all required properties and identify those absolute
properties that must be considered for the product as
“Go-No-Go” properties.
Rate each candidate material on a scale such as 1
to 5 or 1 to 10 for each required property.
Define weighted factor for each required property
based on its significance.
Multiply property rating by its weighted factor and
sum the results for each materials
Select the material that satisfies the “Go-No-Go”
screen and has the highest sum of the relative rating
numbers.
Select a Material with Rating Chart
Material
Go-No-Go
Weldability
Relative rating number - R
(=rating number x weighting factor)
Stiffness
Stability
Fatigue
Tensile
1
4
5
4
SR
Sr
14
A
14
B
14
C
14
SR/r
Select a Material with Rating Chart
Advantages:
 Potential materials can be compared in
a uniform, unbiased manner
 The best candidate can often be
selected
 There is less chance to overlook a
major requirement by placing all the
requirement on a single sheet.
Example: Selection of a Material:
Solution:
•
Finding “Go-No-Go” property: weldability
•
•
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- S: satisfactory
- U: unsatisfactory
Calculating: R = Relative rating number, and r =
weighting factor.
Relative rating number R = property rating number x
weighting factor
•
•
Set material’s property rating number (1 – 5):
excellent = 5, very good = 4, good = 3, fair = 2,
poor = 1
weighted factor for each material’s property:
•
•
•
•
-
Stiffness :
Stability:
Fatigue:
Tensile strength:
1
4
5
4
Solution (cont.)
Rating chart for selecting material
Weldability Stiffness Stability Fatigue
Tensile
Strength
SR
Sr
SR/Sr
(1)
(4)
(5)
(4)
X
Go-No-Go
screening
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
Conclusion:
Based on the chart below, material Y has the
highest rating number. However, because it
does not have satisfactory weldability and this is
an "absolute" requirement, it should not be
selected. Material Z should be used.