Assignment 2 1. Given that atomic radius is 0.143 nm and crystal structure BCC, calculate the APF. Show all works step by step 2. Given that atomic radius is 0.143 nm and crystal structure CPH, calculate the APF. Show all works step by step. 3. Why single unit cell of material (or single grain) is anisotropy but bulk material is isotropy. Explain 4. Describe main differences between ionic and covalent bonding. Give specific examples of materials that demonstrate these types of bonds. 5. Research and describe different types of selective laser sintering technologies for polymer and metal. 6. Research and describe metal power injection molding technology and process. 7. You are asked to design a fuel-saving cooking pan with the goal of wasting as little heat as possible while cooking. What objective would you choose, and what constraints would you think must be met? 8. A volume fraction f = 0.2 of silicon carbide (SiC) particles is combined with an aluminum matrix to make a metal matrix composite. The modulus and density of the two materials are listed below. Determine density and modulus of hybrid material. Aluminum: Density: 2.70 Mg/m3, Modulus: 70 GPa Silicon Carbide Density: 3.15 Mg/m3, Modulus: 420 GPa 9. Use CES EduPack Level 2 to find top three materials for disposable cutlery (single use fork, knife and spoon). Follow 4 step selection strategy and document properly 10. Use CES EduPack Level 2 to find top three materials for disposable coffee lid. Follow 4 step selection strategy and document properly. EduPack 2012 Class Exercises Exercises 1 -3 : Browsing and Searching Exercise 4: Property Charts Exercise 5:Using a Limit Stage Exercise 6: Graph Selection Exercise 7: Tree Selection Exercises 8, 9: Getting it all Together Exercise 10: Process Selection Exercises 11, 12 : saving, Copying, Report Writing Toolbars in EduPack The Chart-Management Tool Bar Line selection tool Box selection tool Cancel selection Add text Zoom Add envelopes Un-zoom Black and white chart Hide failed materials Grey failed materials Add grid Exercise 13, 14 • What is Goretex made of? • Find what the process SLS is all about by searching on SLS. Since it is a process, not a material, you will have to change the table in which you search from Materials Universe to Process Universe, in the box immediately below the search box. Exercise 15, 16 • Find materials that cost less than $1/kg and are good electrical conductors. Enter the upper limit on price and the constraint that the material must be a good conductor. Then click APPLY at the top of the screen. The materials that do not meet the constraints are deleted from the RESULTS window on the lower left, leaving those that do meet the requirements. (ductile CI, grey CI, high C steel, low alloy steel, low C steel, medium C steel) • The property Fracture toughness is a measure of how well ...

1. Assignment 2
1. Given that atomic radius is 0.143 nm and crystal structure
BCC, calculate the APF. Show all works step by step
2. Given that atomic radius is 0.143 nm and crystal structure
CPH, calculate the APF. Show all works step by step.
3. Why single unit cell of material (or single grain) is
anisotropy but bulk material is isotropy. Explain
4. Describe main differences between ionic and covalent
bonding. Give specific examples of materials that demonstrate
these types of bonds.
5. Research and describe different types of selective laser
sintering technologies for polymer and metal.
6. Research and describe metal power injection molding
technology and process.
7. You are asked to design a fuel-saving cooking pan with the
goal of wasting as little heat as possible while cooking. What
objective would you choose, and what constraints would you
think must be met?
8. A volume fraction f = 0.2 of silicon carbide (SiC) particles is
combined with an aluminum matrix to make a metal matrix

2. composite. The modulus and density of the two materials are
listed below. Determine density and modulus of hybrid material.
Aluminum: Density: 2.70 Mg/m3, Modulus: 70 GPa
Silicon Carbide Density: 3.15 Mg/m3, Modulus: 420 GPa
9. Use CES EduPack Level 2 to find top three materials for
disposable cutlery (single use fork, knife and spoon). Follow 4
step selection strategy and document properly
10. Use CES EduPack Level 2 to find top three materials for
disposable coffee lid. Follow 4 step selection strategy and
document properly.
EduPack 2012
Class Exercises
Exercises 1 -3 : Browsing and Searching
Exercise 4: Property Charts
Exercise 5:Using a Limit Stage

3. Exercise 6: Graph Selection
Exercise 7: Tree Selection
Exercises 8, 9: Getting it all Together
Exercise 10: Process Selection
Exercises 11, 12 : saving, Copying, Report Writing
Toolbars in EduPack
The Chart-Management Tool Bar
Line selection
tool
Box selection
tool
Cancel selection
Add text

4. Zoom
Add
envelopes
Un-zoom
Black and white
chart
Hide failed
materials
Grey failed
materials
Add
grid
Exercise 13, 14
• What is Goretex made of?
• Find what the process SLS is all about by
searching on SLS. Since it is a process, not a
material, you will have to change the table in
which you search from Materials Universe to
Process Universe, in the box immediately
below the search box.

5. Exercise 15, 16
• Find materials that cost less than $1/kg and are good electrical
conductors. Enter the upper limit on price and the constraint
that
the material must be a good conductor. Then click APPLY at the
top
of the screen. The materials that do not meet the constraints are
deleted from the RESULTS window on the lower left, leaving
those
that do meet the requirements.
(ductile CI, grey CI, high C steel, low alloy steel, low C steel,
medium C steel)
• The property Fracture toughness is a measure of how well a
material resists fracture. A brittle material like glass has a low
value
of fracture toughness – around 1 in the units you will use
(MPa.m1/2) Steel used for armor has a very high value – over
100, in
the same units. Many engineers, when designing with metals,
avoid
material with toughness less than 15. Use a Limit stage to find
materials with Fracture toughness greater than 15 and that are
good electrical insulators. (GFRP)
Exercise 17
• If you want to make a high quality cooking pan to go on the
top of a gas
stove, you need a material with a high thermal conductivity.
The high

6. conductivity is to spread the heat, preventing hot-spots where
the flame
hits the pan.
• The material must have enough elongation to be shaped to a
pan
(requiring elongation > 15%), and a maximum use temperature
of at least
150 oC.
• First make a limit stage and put these (lower) limits on
elongation and
maximum use temperature. Then make a graph with thermal
conductivity
on the Y-axis. To do this first click on Select, then on New and
then on
Graph stage. Select the Y-axis tab and find Thermal
conductivity in the
Attribute list and double click to select it. When you click OK
you get the
graph shown above. To make the materials that fail the limits
grey out,
click on the little icon like two intersecting circles in the icon
bar just above
the graph. Use a box selection (the little box icon in the same
icon bar) to
select the materials with the highest thermal conductivities.
Exercise 18
• You want to make a casing for a mobile phone, exotic in color
and design. It snaps
onto the front of the phone, transforming it from a drab object

7. to one of glamour.
Research reveals that the shape is best made by Thermoforming
(a very cheap
process for shaping polymer sheet into dished and curved
shapes) and that the
decoration is best applied by In-mold decoration that can be
done at the same
time as the thermoforming. Find materials that can be processed
in this way. To do
this, make two Tree-selection stages. Select -> New -> Tree:
Under the word Trees,
half-way down the box, it says Material Universe. We want to
impose constraints
on Processes, so first click on the down-arrow and change the
Tree to Process
Universe. Open Shaping and find Molding – Thermoforming and
double click to
make it appear in the box above. The wizard window now looks
like the one above
(we have closed Shaping again for clarity). Click OK and the
number of materials in
the Results window drops to 18 – these are materials that can be
thermoformed.
Repeat the job with a second, new, Tree stage, this time opening
Surface
treatment and choosing Painting and Printing – In mold
decorating. The results
window now lists materials that can both be thermo-molded and
in-mold
decorated (10 materials).
Exercise 19
• Problem 1: Select material for bulb filament for an automobile

8. headlight.
• A headlight is an essential part of an automobile. Headlights
differ in detail, but all
have a bulb containing a filament enclosed in a transparent
envelope. The filament
is exposed to harsh conditions: very high temperature, vibration
and a risk of
oxidation. The goal of the project is to use CES to select a
material for the filament.
• Requirements:
– Must be an electrical conductor
– Must resist oxidation
– Must have the highest possible melting point
• Procedure:
Exercise 20
• Problem 2: Select material for the lens of an automobile
headlamp.
Headlamp lens protects the bulb and reflector and focuses the
light where it is
most needed. The
project is to use CES to select materials for the lens.
• Requirements:
– Must be transparent with optical quality.
– Must be able to be molded easily.
– Must have very good resistance to fresh and salt water
– Must have very good resistance to UV light
– Good abrasion resistance, meaning a high hardness
– Low cost Price (USD/kg)

9. • Procedure:
Exercise 21
• Problem 3: Select material for Disposable Cutlery.
• If you eat at an expensive restaurant, the knives may have
steel blades and ivory handles, and the
forks and spoons could be made of silver. But if you eat at a
local fast food joint or on an airplane,
the same function is fulfilled by disposable plastic cutlery. The
function is unchanged; but the
objectives, clearly, are different: minimizing cost and – you
might hope – maximizing recyclability or
renewability. Filling the function imposes constraints on
material and shape: the plastic fork that
snaps in half the first time you use it is only too familiar.
Minimizing cost makes choice of process
critical, and the material itself must also be cheap
• Requirements:
– Young’s Modulus > 1.7 GPa
– Tensile Strength > 24 MPa
– Cost < $1.8/kg
– Manufacturing process: economical for batch sizes >=
100,000 pieces
– Recyclable
– Bio-safe
– Corrosion resistant
– …
• Procedure:
– Up to you now!

10. Physical Constants and Unit Conversion Tables
Exercise 22: Eco Audit
22
Exercise 22: Eco Audit (contd.)
Exercise 23: Compare Eco Audits
23
Class Exercise 24, 25: Saving Eco Audit Product Definition
25
24
Summary: EduPack
By now you should feel comfortable with doing the following
actions
using CES EduPack materials engineering software

11. • Selecting appropriate databases (mainly Level 2)
• Understand the structure of materials and processes databases
and their linkages with each other and with manufacturers and
resources databases
• Browsing, searching, selecting
• Using graph, limit and tree stages in selecting
• Creating material property charts – bar charts and bubble
charts
• Conduct materials design projects
• Conduct materials selection process
• Conduct EcoAudit for a product
• Saving, editing, importing and report writing
1

12. 1
Strength and Stiffness
Stress is applied to a material by loading it
Strain – a change of shape – is its response
Stiffness is the resistance to change of shape that is elastic – the
material will return to its original shape when unloaded
Strength is the resistance to permanent distortion or total failure
2
2
Material Properties
Stress and strain are not material properties – they
describe a stimulus and a response
Stiffness and strength are material properties which are
measured by the elastic modulus (E), elastic
limit (σy), and tensile strength (σts)
Stiffness, strength, and density are three material

13. properties central to mechanical design
3
3
Density
Figure 4.1
Mass per unit volume – kg/m3 or lb/in3
Double-weighing method for calculating density
4
4
Modes of Loading
(a) – axial tension
(b) – compression
(c) – axial tension on one

14. side and compression
on the opposite side
(d) – torsion
(e) – bi-axial tension or
compression
Figure 4.2
5
5
Stress
Figure 4.3
(a)
Force applied normal to surface
Positive F indicates tension
Negative F indicates compression
(b)
Force applied parallel to surface
Shaded plane carries the shear stress
(c)
Equally applied tensile and compressive forces on all six sides
of a cubic element
Hydrostatic pressure

15. 1 N/m2 = 1 Pascal (Pa)
106 Pa = 1 MPa
1 lb/in2 = 1 psi
103 psi = 1 ksi
6
6
Class Exercise
A cylindrical brick chimney is 50 feet tall. The bricks have a
density of 1800 kg/m3. What is the axial compressive stress at
the base? Does the shape and size of the cross-section matter?
Will the bricks at the base support the pressure?
7

16. Class Exercise:
Solution
Force = weight of chimney = mass x acceleration due to gravity
Stress = -Force /Area = - -15.24 x 1800 x 10 = 269,000
Pa = -0.269 MPa (‘-’ indicates compression)
The stress is independent of the shape or size of the cross-
section
Will the brick at base hold? Yes – compressive strength of
bricks is 10 – 70 MPa
8

17. Strain
Figure 4.3
(a)
Tensile stress lengthens the element causing a tensile strain (+)
Compressive stress shortens the element causing a compressive
strain (-)
Strain is the ratio of two lengths
and is therefore
dimensionless
9
Hooke’s Law: within elastic regime, strain is proportional to
stress:

18. 9
Stress-Strain Curves
Figure 4.4
Initial portion of curve is approximately
linear and is elastic – the material
returns to its original shape once the
stress is removed
Within the linear elastic region, strain is
proportional to stress
E: Young’s modulus
G: shear modulus
K: bulk modulus
10

19. 10
Stress-Strain Curve –
Brittle Response
Entire response is elastic –
no plastic deformation
Yield strength not reached
before failure
Young’s modulus determined
by calculating the slope of
this region
11

20. 11
Ductile Response
Permanent deformation occurs at stresses beyond the yield
strength – material will not return to its original shape past this
point
Tensile strength is maximum
stress on the curve
Yield strength determined by
standard offset methods
12

21. 12
Poisson’s Ratio
Relates the Young’s modulus, shear modulus, and
bulk modulus to one another
Negative of the ratio of transverse strain
to axial strain in tensile loading
13

22. 13
Class Exercise
In reference to chimney example, given that Young’s modulus
of the bricks is 25 GPa and Poisson’s ratio is 0.2, what is the
axial and transverse strain at the bottom of the chimney?
14
Class Exercise -