Chapter 1: Introduction To Materials Selection
CHAPTER 1
INTRODUCTION TO MATERIALS SELECTION
1.1
Methods of Selection
There are three methods of materials selection: classical, imitative and
comparison.
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Classical Method
Selection is done through analysis of function and properties specification.
Characteristic – functional and requirement of component and materials
properties.
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Imitative Method
Selection is made by equality or similarity of function.
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Comparison Method
Assume the component is made from a normal & low cost material; the
material disability is then evaluated, if it is not suitable then the other
material is selected and evaluated – the process goes on until a suitable
material is obtained.
Classical method is more specified, more global, high cost, required longer
time to complete the selection and need to do a prototype test.
Imitative and Comparison method are faster and involve low cost, however
they are more suitable for an experience person or designer.
1.2
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Materials in Design
Design is a process of translating new idea or a market need into the
detailed information from which a product can be manufactured.
Normally, the choice of material is dictated by design.
However, the development of new product, or the evaluation of the
existing one, was suggested or made possible by the new material.
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What is the ROLE of material in design???
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At the beginning of the design process – all materials must be considered.
As the design becomes more focused and take shape – the shortlist of
materials are considered.
In the final stage of design, precise data are needed – few materials or
perhaps only one material is chosen.
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Figure 1.1 shows the relationship between materials, function, process and
shape in the design process.
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Chapter 1: Introduction To Materials Selection
FUNCTION
MATERIALS
SHAPE
PROCESS
Figure 1.1: Function, material, process and shape interact (M.F.Ashby, 1999).
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Design problem, almost always, are open-ended. They do not have a
unique or correct solution, although some solution will clearly be better
than others will.
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This module focuses on the materials aspects of the design process. It
provides a methodology which properly applied, gives guidance through
the forest of complex choices the designer faces.
1.3
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Evolution of Engineering Materials
The evolution of engineering material and its increasing pace are shown in
Figure 1.2.
It started with ceramics and glasses (>10 000BC, the Stone Age) and then
came to the Bronze Age and followed by Iron Age.
In 1620s, cast iron technology has been established. However, there were
also developments in the other classes of material.
The rapid rate of materials change offers opportunities which the designer
cannot afford to ignore.
The following case study (evolution of materials in vacuum cleaners) is an
example.
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The vacuum cleaners of 1900 and before were human-powered
(Figure 1.3(a)). It was largely made of wood and leather.
The electric vacuum cleaner first appeared around 1908. By 1950
the design had evolved into the cylinder cleaner shown in Figure 1.3
(b). This cleaner is almost entirely made of metal.
Developments have been rapidly driven by the innovative use of new
materials. The 1985 vacuum cleaner of Figure 1.3 (c) are now
available. The casing is entirely polymeric, no metal is visible
anywhere, metal in all earlier models is now substitute with
polypropylene.
Figure 1.3 (d) exploits a different concept, the product is larger,
noisier, heavier and much more expansive, yet it sells – a testament
to good industrial design and imaginative, aggressive marketing.
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Chapter 1: Introduction To Materials Selection
Figure 1.2: The evolution of engineering materials with time. The time scale is non-linear. The rate of
change is far faster today than at any previous time in history (M.F.Ashby, 1999).
Figure 1.3: The evolution of materials in vacuum cleaners (M.F.Ashby, 1999).
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Chapter 1: Introduction To Materials Selection
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All this has happened within one lifetime. Competitive design requires the
innovative use of new materials and the clever exploitation of their special
properties, both engineering and aesthetic.
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The same process happened to other product such as telephone, car, sport
equipments, aero plane etc.
1.4
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Source of Information
As an engineer or designer, he should have a sufficient knowledge and
information about materials and their properties.
This information can be obtained from :
Standard – ASTM (American Society Testing Methods), BS (British
Standard),
DIN, JIS, MS etc.
Software - CES, NOVA, PERITUS etc.
IDEA
Component
category
Complex solid, long, short, hollow
Concentric, non-hollow concentric,
Solid non concentric, cup, dish, cone,
Spirals, repititive, flat, bent, flanged
Low temp limit
High temp limit
Joining method
Shape
category
Operational
factors
Process characteristics
Quantity, Size,
Precision,
Complexity,Finish,
Cost
Housings, covers, gears, bolts,
Bearings, wear surfaces,
Electrostructural, thermostructural,
Insulators, conductors, large
Mechanical, springs, clips, force
Absobers, light transmitters
Environment resistance
Surface coating
Cost allowance
Materials characteristics
Candidate materials & processes
Stability, Stiffness,
Density, Max. Stress,
Toughness, Cost
Materials data & optimisation
Figure 1.4: The linkage of information in material selection (K.G.Budinski, 1997)
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The number of engineering materials is large, estimates more than
80 000.
Therefore, an engineer or designer must select from this vast menu the
material best suited to his task.
This, without guidance, can be a difficult and tedious business; so the
knowledge about material selection is very important in order to get the
opportunity for innovation.
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Chapter 1: Introduction To Materials Selection
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Engineering materials are evolving faster, and the choice is wide than ever
before.
As a result, it is important in the early stage of design, or of re-design, to
examine the full materials menu, not rejecting options merely because
they are unfamiliar.
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