Post on 30-Dec-2015
T.M.F.T: Thermal Mechanical Fatigue
Testing
Wale Adewole
Siyé Baker
Heriberto Cortes
Wesley Hawk
Ashley McKnight
Outline
Project Scope Background
Research Design Ideas Design Selection Future Plans
Project Scope
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
American Society for testing and materials definition of fatigue.
“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.
Design Ideas Continued
Resistance Heating and Convective Cooling
Heating of the sample is done by a resistance heater placed near the sample.
Cooling is done by convection with the surrounding air.
Heating and cooling are toggled via electrical controls.
Pros. Electrical control of heating and cooling
cycles.Cons. Specimen holder not isolated from
thermal effects. Long heating and cooling periods.
Design Ideas Continued
Hot Oil Bath Heating is done through placement in
a hot oil bath. Cooling is done through dipping in a
cooling bath. Specimen is mechanically moved from
one bath to the other.
Pros. Fast heating a cooling rates. Low amount of input from user.
Cons. Testing rig is exposed to thermal
fluctuation. Danger caused by splattering oil.
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.
Cooling is done by convection. Heating is turn off when sample reaches
desired temperature.
Pros. Thermal isolation of testing rig. Ability to measure sample temperature
and load. Electronic control requires minimum user
input.
Cons. Larger cost.
Design Matrix
D1=Furnace/Water Bath D3=Hot Oil BathD2=Resistance Heater/Convection Cooling D4=Thermal Isolation Rig
Time/Length Complexity Effectiveness Cost Safety Total ScoreWeight % 0.2 0.05 0.4 0.2 0.15 1
DesignD1 1 4 2 4 3 1.56D2 3 2 3 2 3 2.08D3 4 1 2 3 1 1.74D4 3 2 4 1 2 2.36
Final Design
Thermal Isolation Rig 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
Aluminum Specimen
Load Cell
Holding Clamps
Clamp Design
Clamp 1(left): Designed to connect load
cell to aluminum specimen. Raised edges to direct
cooling water flow.
Clamp 2(right): Stationary clamp attaches
specimen to base. Hole for thermocouple wire
to pass through. Raised edges to direct
water flow.
Raised Edge
Thermocouple wire hole
Load cell threaded attachment point
Calculations
Energy transfer through Conduction. 130 Watts
Energy loss due to natural convection. 8 Watts
Time required to cool sample. 37 seconds
Initial FEM Analysis
Displacement and reaction forces of constrained aluminum sample.
Initial FEM Analysis Initial stresses in the
clamp from thermal expansion.
Initial displacement in the clamp from thermal expansion.
Initial FEM Analysis
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
Water flow rate 60 gal/hr
Laminar flow rate over the clamp.
Water convection coefficient over clamp.
4.777E+3 W/(m^2*K)
Calculated energy loss through clamp at max temperature.
180 Watts
Revised FEM Analysis
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 Quanity Price VendorItem
Water Pump Small pump for water flow 1 $21.71 HOME DEPOTCast Iron Material for test rig base 6 pc TBA TBA
Aluminum Material for test samples 3 pc $0 CumminsHeating Wire Coils used to heat sample 50 ft $63 OMEGA.com
Heat Controller Controller for heat source 1 TBA TBAWater Tubing* tubing to faciliate water flow 10 ft. $1/ft HOME DEPOT Cut to orderThermocoulple Accurately measure temp of sample 1 $71 Ambientweather.comThermocoulple* Accurately measure temp of sample 1 $229 Ambientweather.com
Load Cell " " " " meaure load on sample 1 $575 OMEGA.comLCM203 Series
Misc screws, tools, etc….. ……. $25 HOME DEPOTTotal=$765.71
Testing Procedure
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
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
Order Parts Review design with sponsor. Begin machining of testing rig. Material analysis before and after testing. Create Operations Manual
Questions?