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

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T.M.F.T Thermal Mechanical Fatigue Testing


Sponsored by Cummins
Group Members

• Wale Adewole
• Siyé Baker
• Heriberto Cortes
• Wesley Hawk
• Ashley McKnight

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Outline

• Project Scope
• Abstract
• Background Research
• Design
• Design Analysis
• Testing Procedure/Setup
• Results
• Future Changes
• Conclusion
• Special Thanks

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Project Scope

• Locate and identify standards for thermal
  mechanical fatigue failure.
• Create a testing rig and a
• sample.
• Create Testing Procedure
• Test aluminum specimens
• and accurately identify the necessary
• properties that affect thermal fatigue
  failure.

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Abstract

• Final design consist of modifications to an
  existing machine.
• Machine shown is the ATS 1600.
• ATS 1600 is equipped with furnace and 50,000 lb
  load cell.
• Computer controlled oven cycles and data
  acquisition.

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Research

• American Society for Testing and Materials(ASTM)
  definition of fatigue.
• The process of progressive localized permanent
  structure change, occurring in a material
  subjected to fluctuating stresses and
  strainswhich may culminate in cracks or complete
  fracture after sufficient number of
  fluctuations.
• Constrained thermal fatigue is the result of a
  material being restricted from expansion caused
  by rising temperature.
• This constraint places the material under
  compressive forces with rising temperature and
  tensile forces during cooling.

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Initial Design Ideas

• Idea 1
• Electric heating and cooling.
• Idea 2
• Oil bath heating.
• Water cooling.
• Mechanical transfer.
• Idea 3
• Electric heating.
• Water cooling of clamps.

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Fall Design

• Independent clamps
• Water cooling over clamps to protect load cell.
• Measurement capabilities
• Load Cell for force measurements.
• Thermal couple for temperature measurements.
• Cycle is automated

Load Cell
Aluminum Specimen
Holding Clamps
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Initial FEM Analysis

• Displacement and reaction forces of constrained
  aluminum sample.

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Time for a Change

• Forces produced by the aluminum expansion
  exceeded anything that could be built within our
  budget.
• Very large load cell would be needed which would
  also exceed our budget.
• Cooling system would be inadequate.
• Heating system would also exceed budget.

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Final Design Outline

• ATS background information.
• Attachment to ATS.
• Materials that will be used.
• F.E.M. Analysis.
• Timing Calculations.

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ATS-1600

• Rigid test frame that contains load cell capable
  of 50,000 lbs of force.
• Load cell has been calibrated to work with
  testing software.
• Contains clamping furnace that will reach
  temperatures of 1100C

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ATS-Sample Holder

• Threaded attachment to ATS base and load cell.
• Macor used for thermal isolation to ensure load
  cell will not be damaged.
• Ability to hold sample centered so that only
  axial forces will be produced.

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Materials
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FEM Sample

• The aluminum sample is exposed entirely to the
  heat source.
• As expected the entire sample reaches 800F at
  steady state.

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FEM Steel Sleeve

• Since the entire sleeve is in the oven, all
  exposed surfaces where given an applied
  temperature of 800F.
• At steady state the entire steel sleeve reaches
  800 F

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FEM Macor

• From the FEA of the steel sleeve, a temperature
  of 800?F was applied to the top of the macor.
• The bottom only reaches bout 400 ?F, roughly half
  the applied temperature.

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FEM Steel Rod

• From the FEA of macor, a temperature of 412F was
  applied at the contact surface.
• A temperature of 69 F was applied half way on
  the rod to simulate the water cooling.
• All other surface exposed to natural convection
  with the air at 74 F

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Estimated Time

• Heating through natural convection and radiation.
• Approximately 6 min.
• Cooling through natural convection and
  conduction.
• Approximately 5.5 min.
• 10 minute oven heat up time.
• Forced convection will be induced to aid in
  cooling.

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ProcedurePart 1 TestVue32

• Log into the computer and open the TestVue32
  program.
• Complete initial setup(jog pot, load cell, etc..)
• Create test program to run experiment.

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ProcedurePart 2 Oven Setup

• Flip both power switches.(main controller)
• Set emergency stop temperature.
• Use oven controller to create custom heating
  cycle for test.

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Procedure Part 3 Equipment Setup-Sample Holder
Steel Sleeve

• The sample holder consist of three parts.
• Steel Rod, Macor, Steel Sleeve.
• All pieces screw together Steel RodMacorSteel
  Sleeve.

Macor
Steel Rod
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Completed Sample Holder
Macor
Steel Sleeve
Steel Rod
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Procedure Part 3 Equipment Setup-Sample

• Screw both sample holders into test rig.
• Adjust crosshead height so sample can be placed
  in.
• Place sample in bottom holder and lower crosshead
  until sample is secure.

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ProcedurePart 3 Equipment Setup

• Oven height must be adjusted to enclose the
  sample.
• Loosen hex nut on oven holder.
• Adjust so that oven completely closes sample.

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Procedure Part 3Equipment Setup-Cooling

• Connect main tubes from the source of the water
  and air.
• Place copper on sample holders.(wrap, bend, etc.)
• Connect copper tubing to tubes coming from the
  sources.

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Results

• Pros
• Test produced load variation with temperature
  change.
• Load cell successfully isolated from temperature
  changes.

• Cons
• Samples bent from thermal expansion loads
  produced.
• Testing cycle not automated.
• Cycle length too long.

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Aluminum 6063 Results
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Aluminum 6061 Results
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Temperatures and Times
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Expenses
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Future Changes

• Most Feasible Changes
• Reduce Sample Length.
• Clamp sample at ends.
• Automation of entire cycle.
• Encase sample in quartz tube.
• New sample shape.
• Heat only small section of sample.
• Increase cooling effectiveness.

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Conclusion

• Principle material properties that effect thermal
  fatigue
• Thermal Expansion Coefficient.
• Sample Length
• Compressive Strength
• Testing inconclusive due to
• Euler bending
• Cycle Length
• Sample Length
• Unbroken Sample

• Maximum load from thermal expansion
• Al-6063 2,257 lb
• Al-6061 2,278 lb
• Euler bending 4,200 lb.
• Since actual load was roughly half, the fatigue
  on the aluminum caused the sample to get weaker
  as cycles progressed.

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Special Thanks

• Sponsor Cummins
• Dr. Loungo
• Bob Walsh
• N.H.M.F.L. Machine Shop

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The End