T.M.F.T: Thermal Mechanical Fatigue Testing

1. Wale Adewole Siyé Baker Heriberto Cortes Wesley Hawk Ashley McKnight T.M.F.T: Thermal Mechanical Fatigue Testing

2. Outline • Project Scope • Background Research • Design Ideas • Design Selection • Future Plans

3. 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.

4. 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.

5. 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.

6. 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.

7. 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.

8. 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.

9. Design Matrix

10. 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.

11. Pro-E Drawing Load Cell Aluminum Specimen Holding Clamps

12. 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. Thermocouple wire hole Load cell threaded attachment point Raised Edge

13. Calculations • Energy transfer through Conduction. • 130 Watts • Energy loss due to natural convection. • 8 Watts • Time required to cool sample. • 37 seconds

14. Initial FEM Analysis • Displacement and reaction forces of constrained aluminum sample.

15. Initial FEM Analysis • Initial stresses in the clamp from thermal expansion. • Initial displacement in the clamp from thermal expansion.

16. 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.

17. 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 throughclamp at max temperature. • 180 Watts

18. 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

19. Estimated Cost

20. 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.

21. 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.

22. Future Plans • Order Parts • Review design with sponsor. • Begin machining of testing rig. • Material analysis before and after testing. • Create Operations Manual

23. Questions?