Researching properties of metals and choosing the best metal for a product.

1. COLLAPSIBLE BIKE FRAME
MATL 341
Bo Cook, Suhrob Shirinov
SPRING 2015

2. Product:
 Collapsible Bike Frame
Target Consumer:
 We’re expecting a wide age range for this product, from high school students to middle-aged
people. We believe the high school students will like being able to bring this product with them
into school or to a friend’s house. College students would most likely appreciate being able to
easily bring this product into their dorms or apartments so it could avoid certain weather and be
difficult to have their product stolen. The middle-aged people would like it for its light weight
and protection from possible theft. All of them would share other similar interests with it such
as the product being able to fit into vehicles, not taking up a lot of storage space, and being easy
to take when traveling or on trips. We are aiming for this frame to be low cost, in the $100 to
$200 range.
Product Description:
 This product is meant to be a means of transportation with the ability to collapse to make it
easier to bring along with the user wherever they go. The frame itself will consist of telescoping
assemblies and hinge action to create the collapsibility desired.
Manufacturing Methods:
 Tube Components:
o Extrusion
o Drawn Over Mandrel
o Butt-Weld Process
 Extra Components (U-shaped pieces for the end of tubes, housings, bolts or rods, seat holder):
o Casting
o Machining
o Bending
o Extrusion
 Assembly Processes:
o Welding
o Brazing
o Gluing
Types of Stresses:
 *The weight of the rider for this product is set at a max or 300 lbs.
 Shear Stress
o With hinge action, the bolts or rods used in the expanded phase of the bike will
experience shear stress.
 Flexural Stress
o Depending on the shape of the frame, the rider could be applying a downward force on
horizontal or near horizontal frame pieces.
 Compression

3. o When the bike is in the expanded phase and being used, there is an amount of
compressive stresses being applied on the part of the frame pointing towards the
ground (basically anything parallel or close to that or the riders down force).
 Impact
o With the bike being used in a variety of environments, it could come into contact with
potholes or hit elevated spots such as curbs.
 Fatigue
o Depending on the type of rider, the bike could undergo various amount of cyclic loading
for long periods of time such as riding through pothole filled streets or on rough terrain
trails.
Operational Conditions:
 This product is meant to be used in basically any kind of environment. Our temperature
range will be from -60 °F to 150 °F. We also know that this product will come into
contact with the following:
o Water
o Salt from the roads or sweat
o Gravel
o Lubricants
o Food/Drinks
o Dirt
o Mud
o Sand
o Various cleaners/polishes
Failure Modes:
 This product could fail due to any of the stresses described before. Shear, flexural, and
impact failure would be the 3 most common types of failure with fatigue and
compressive failure being the next most common.
 The frame could also be weakened by the environmental impact on it. Corrosion from
any of the fluids mentioned before and abrasive wear from any of the solids mentioned
before.
Prototype Testing:
 We would first create a physical prototype of each frame with the quickest and simplest means
of manufacturing such as machining and using stock tube sizes. After completing the frame, we
would use a variety of methods to test them such as:
o Putting a pole in the seat holder, adding the max weight of our target rider (300 lbs.),
and bounce it in various directions.
 One would be leaning it back and dropping it on its front fork continuously over
a certain amount of time.
 Another would be the same way except leaning it forward and continuously
dropping it on the back portion of the frame.
 Another way would include just dropping it from a certain height continuously.

4. o Using excessive weight that’s over our intended limit and repeating those impact tests.
o We can ram the frames into walls or curbs either from the front, back, or sides, to
simulate aggressive impacts the bike could encounter.
o Putting the frame into a highly corrosive environment and repeating the above tests.
o Using some of the solid materials the frame could encounter such as sand and gravel,
continuously put it on the frame, in the crevices, hinges, and telescoping assemblies,
and rub it against the frame and also use the collapsible actions such as telescoping and
folding to see how it reacts with those materials present. We can also repeat the above
tests with the solid materials having been applied for a certain period of time.
Material Properties:
Operational Conditions Potential Failures Rating Target Values
Density (g/cc) Must be lightweight Too heavy or not
dense enough
Desired Maximum 4
g/cc
Elongation (%) Cannot plastically deform
under certain loads
Crack, complete
failure, or plastically
deform
Desired Minimum 15 %
Fatigue
Strength
(psi/# of
cycles)
Must withstand certain
stresses after a certain
amount of cycles
Crack, complete
failure, or plastically
deform
Desired 15000 psi
Hardness
(Brinell)
Must have high wear
resistance and resist
scratching
Wears or scratches
easily
Desired Minimum 90
Modulus of
Elasticity (ksi)
Must be moderate stiffness
with some good toughness
Crack, complete
failure, or plastically
deform
Required Minimum 9000
ksi
Shear Strength
(psi)
Must resist stresses in
opposing directions
Crack or complete
failure
Required Minimum
35000 psi
Toughness
(ksi/in^1/2)
Must have some give
(elasticity) under certain
stresses
Crack, complete
failure, or plastically
deform
Required 20 ksi/in^1/2
Flexural
Strength (psi)
Must resist stresses
perpendicular to certain
components
Crack, complete
failure, or plastically
deform
Required Minimum
25000 psi
Compressive
Strength (psi)
Must resist stresses pushing
down on vertical or near
vertical components
Crack, complete
failure, or plastically
deform
Desired Minimum
27500 psi
Corrosion
Resistance
Must resist various types of
corrosion & chemicals
Cannot withstand
certain corrosion or
chemicals
Desired Most types of
corrosion and
chemicals
Cost ($/lbs) Must be relatively low cost Too expensive Required Maximum 2
$/lbs

5.  *Most of the target values used were based off of Aluminum properties with some variation to
allow a greater variation of possible alloys that can be used.
Decision Matrix:
 We decided to just use Aluminum and Steel for our decision matrix since Titanium is too
expensive and magnesium would be able to handle the stresses required.
Conclusion:
After completing this matrix, we decided to select steel as our main choice since it has a greater
overall score. Even though it is heavier and more corrosive, we believe that its other properties
outweigh those two bad properties. Weight may be relatively important but since it’s meant to
be a low cost bike frame, we assume the user would rather have a lower costing bike that’s a
little heavier instead of one that more expensive with a little weight reduction. As for corrosion
resistance, we will add a coating to help protect it from certain environmental corrosion.
Importance
Desired
Values
Values Rank Score Values Rank Score
1 Density 10 <4 g/cc 2.7 g/cc 1.48 14.81 7.85 g/cc 0.34 3.44
2 Elongation 5 >15 % 17 % 1.13 5.67 25 % 1.73 8.67
3 Fatigue Strength 8 15 ksi 14 ksi 0.93 7.47 N/A 1.00 8.00
4 Hardness 5 >90 Brinell 95 Brinell 1.06 5.28 197 Brinell 2.19 10.94
5 Modulus of Elasticity 7 >9000 ksi 10000 ksi 1.11 7.78 29700 ksi 3.30 23.10
6 Shear Strength 5 >35 ksi 30 ksi 0.86 4.29 N/A 1.00 5.00
7 Toughness 8 20 ksi-in^1/2 26.4 ksi-in^1/2 1.32 10.56 N/A 1.00 8.00
8 Yield Strength 10 >30 ksi 40 ksi 1.33 13.33 63.1 ksi 2.10 21.03
10 Corrosion Resistance 9 Good/Bad Good Good 1.00 Bad 0.00 0.00
11 Cost 10 < 2$/lbs 8$/lbs 0.25 2.50 4.18 0.48 4.79
Total: 72.68 Total: 92.97
6061 T-6 4130 Steel
Decision Matrix

6. References:
 http://asm.matweb.com/search/SpecificMaterial.asp?bassnum=MA6061t6
 https://www.midweststeelsupply.com/store/6061aluminumsheet
 http://www.ibiscycles.com/support/technical_articles/metallurgy_for_cyclists/steel_is_real/
 http://asm.matweb.com/search/SpecificMaterial.asp?bassnum=m4130r
 https://www.onlinemetals.com/merchant.cfm?pid=7368&step=4&showunits=inches&id=254&top_cat=0