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?