T.M.F.T:
Thermal Mechanical Fatigue
Testing
Wale Adewole
Siyé Baker
Heriberto Cortes
Wesley Hawk
Ashley McKnight
Outline
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Project Scope
Background
Research
Design Ideas
Design Selection
Future Plans
Project Scope
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Locate and identify standards for thermal
mechanical fatigue failure.
Create a testing rig and a sample.
Test the aluminum specimens and accurately
identify the necessary properties.
Use these results to create a program that can
accurately predict if one aluminum sample will
be better suited for a thermal mechanical fatigue
application based on its mechanical properties.
Research
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American Society for testing and materials definition of
fatigue.
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“The process of progressive localized permanent structure change,
occurring in a material subjected to fluctuating stresses and
strains…which may culminate in cracks or complete fracture after
sufficient number of fluctuations.”
Constrained thermal fatigue is the result of a material not
being able to expand under rising temperature.
This constraint places the material under compressive
forces with rising temperature and tensile forces during
cooling.
Design Ideas
Manual Heating and Cooling
Heating is done by placing
specimen in a furnace.
 Cooling is done by placing the
specimen in a water bath.
 Specimen is manually moved from
the heat to the cooling chamber.
Pros.
 Inexpensive.
 Simple design.
Cons.
 Specimen holder is affected by
temperature change.
 Long, and tedious process.
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Design Ideas Continued
Resistance Heating and
Convective Cooling
Heating of the sample is done by a
resistance heater placed near the
sample.
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Cooling is done by convection with the
surrounding air.
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Heating and cooling are toggled via
electrical controls.
Pros.
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Electrical control of heating and cooling
cycles.
Cons.
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Specimen holder not isolated from
thermal effects.
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Long heating and cooling periods.
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Design Ideas Continued
Hot Oil Bath
Heating is done through placement in
a hot oil bath.
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Cooling is done through dipping in a
cooling bath.
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Specimen is mechanically moved from
one bath to the other.
Pros.
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Fast heating a cooling rates.
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Low amount of input from user.
Cons.
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Testing rig is exposed to thermal
fluctuation.
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Danger caused by splattering oil.
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Design Ideas Continued
Thermal Isolation Rig
Heating is done by electrical resistance
heating coil placed around a small
section of the center of the sample.
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Cooling is done by convection.
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Heating is turn off when sample reaches
desired temperature.
Pros.
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Thermal isolation of testing rig.
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Ability to measure sample temperature
and load.
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Electronic control requires minimum user
input.
Cons.
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Larger cost.
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Design Matrix
D1=Furnace/Water Bath
D2=Resistance Heater/Convection Cooling
Weight %
Design
D1
D2
D3
D4
D3=Hot Oil Bath
D4=Thermal Isolation Rig
Time/Length
0.2
Complexity
0.05
Effectiveness
0.4
Cost
0.2
Safety
0.15
Total Score
1
1
3
4
3
4
2
1
2
2
3
2
4
4
2
3
1
3
3
1
2
1.56
2.08
1.74
2.36
Final Design
Thermal Isolation Rig
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Has the ability to test tension and
compression of the specimen
during heating and cooling cycles.
Testing rig is isolated from the
thermal fluctuation due to the
cooling of the specimen holder
clamps.
Simple stationary design requires
on moving parts.
Pro-E Drawing
Load Cell
Aluminum
Specimen
Holding
Clamps
Clamp Design
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Clamp 1(left):
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Clamp 2(right):
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Load cell threaded
attachment point
Designed to connect load
cell to aluminum specimen.
Raised edges to direct
cooling water flow.
Stationary clamp attaches
specimen to base.
Hole for thermocouple wire
to pass through.
Raised edges to direct
water flow.
Thermocouple
wire hole
Raised Edge
Calculations
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Energy transfer through
Conduction.
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Energy loss due to natural
convection.
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130 Watts
8 Watts
Time required to cool
sample.
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37 seconds
Initial FEM Analysis
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Displacement and
reaction forces of
constrained
aluminum sample.
Initial FEM Analysis
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Initial stresses in the
clamp from thermal
expansion.
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Initial displacement
in the clamp from
thermal expansion.
Initial FEM Analysis
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The initial
temperature
distribution on the
clamp without
cooling of the clamp.
Entire clamp
reaches over 400°F.
Unacceptable
amount of heat from
sample.
Calculations Continued
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Water flow rate
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Laminar flow rate over
the clamp.
Water convection
coefficient over clamp.
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60 gal/hr
4.777E+3 W/(m^2*K)
Calculated energy loss
through clamp at max
temperature.
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180 Watts
Revised FEM Analysis
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Using new values for
convection coefficient.
Temperature distribution
not as dramatic with
combined convection
and water flow.
Max=450°F
Min=81°F
Estimated Cost
Description
Item
Water Pump
Small pump for water flow
Cast Iron
Material for test rig base
Aluminum
Material for test samples
Heating Wire
Coils used to heat sample
Heat Controller
Controller for heat source
Water Tubing*
tubing to faciliate water flow
Thermocoulple Accurately measure temp of sample
Thermocoulple* Accurately measure temp of sample
Load Cell
Misc
"
"
" " meaure load on sample
screws, tools, etc…..
Quanity
Price
Vendor
1
6 pc
3 pc
50 ft
1
10 ft.
1
1
$21.71
TBA
$0
$63
TBA
$1/ft
$71
$229
HOME DEPOT
TBA
Cummins
OMEGA.com
TBA
HOME DEPOT
Ambientweather.com
Ambientweather.com
1
…….
$575
$25
Total=$765.71
OMEGA.com
HOME DEPOT
Cut to order
LCM203
Series
Testing Procedure
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Sample is place in tester.
Water flow over clamps is initialized.
The sample is heated to 150°F and the load cell
is zeroed.
Sample will be cycled between maximum
temperature and minimum temperature until
failure occurs.
Data is collected from the sample at even
increments.
Data Acquisition
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The loads created by the thermal tension and
compression of the specimen will be acquired by using a
load cell that will be connected to a computer with lab
view or a similar program.
This data will be correlated with the temperature data
obtained from the thermocouple throughout the
experiment.
This acquired data will be used to analyze the effect of
thermal fatigue on different materials.
It will also be used to obtain a relationship between
material properties and thermal fatigue failure.
Future Plans
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Order Parts
Review design with sponsor.
Begin machining of testing rig.
Material analysis before and after testing.
Create Operations Manual
Questions?