1. Advanced Machining of Alternative Materials-Part A: Cutting Mechanics
John Patten-Director/Chair/Professor
Manufacturing Research Center
Manufacturing Engineering Dept.
Western Michigan University
9/17/2018

2. Project Goals Machining Alternative Materials Tech Group
Machining and Material Removal Tech Comm.
Paper and Presentation by Tech Group
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3. Description
Summarize work on cutting mechanics (A) and tool geometry (B)
Alternative (Advanced) materials
Semiconductors
Silicon, Single Crystal SiC
Ceramics (fully sintered)
Silicon Nitride, Silicon Carbide
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4. Competitive Analysis Competitors Strengths Weaknesses
Machining: Single point processes (SPDT)
Grinding, Lapping, polishing
Strengths
Precise form accuracy, ductile material removal
Weaknesses
Tool Wear
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5. Competitive Analysis, Cont.
Single point machining
Rough Finishing: Brittle Material Removal
Finish Machining: Ductile Cutting
Augmentation and Enhancements
Cutting Mechanics
Cutting fluids and heat assisted machining
Tool Geometry
Negative rake angle
Sharp cutting edges (small cutting edge radii)
FOR MORE INFO...
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6. Technology Nano to micron level cutting conditions (feed and depth)
Significant finding:
Cutting force<Thrust force
Analysis includes:
Chip formation
Friction
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7. Team/Resources Ductile Regime Ceramic Machining
Diamond Turning Machines (DTM)
UNCC, Tohoku Univ., ORNL, PSU
NSF, TWS (DOD)
Structural ceramics, semiconductors and optics
9/17/2018

8. Figure 2 Schematic of the the nano-probe with the serial-structure
Schematic of DTM with Force/Displacement
Impact cap
PZT
PZT fixture
Diamond tool
Force sensor Y X Z
Leaf-type linear spring t L
Figure 2 Schematic of the the nano-probe with the serial-structure
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9. DTM Spindle (Air Bearing)
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10. Ductile-Brittle Transition: Si3N4
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11. Ductile Machining: Si3N4
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12. Ductile – Brittle Chips
The relative amount of ductile chips increases (as a % of total debris) as:
A more negative rake angle is used
A smaller depth of cut
The size (length) of the ductile chips increases as:
The depth of cut increases
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13. Origin of ductile response
High Pressure Phase Transformation could generate the ductile response
Cutting speeds can be quite quite low,
Temp. corresponding low (< 500°C) based upon simulation results
Dislocation based plasticity not active at such low temperatures
Shear significantly contributes to observed ductility
Shear reduces the phase transformation pressure threshold
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14. Machining forces: 6 fold Coordination Pattern
SC SiC
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15. Current Status
High Pressure/Chip Formation Zone
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16. Amorphous Layer: Machined Si
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17. Raman of Machined SiN Peak Broadening Indicates Amorphous Remnant
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18. Raman of Chips (debris)
Peak broadening indicates amorphous remnant
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19. High Pressure Phase
The high pressure phase (Pressure=Hardness) for semiconductors and ceramics is metallic, i.e. a metal!
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20. Possible explanation of amorphous zone
Figure-11
A metallic phase area is generated under the pressure of the tool. As the diamond tool going forward, metallic phase changes to amorphous phase.
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21. Machining Analysis Forces, Temperatures, Pressures
Uncut Chip Thickness (feed and depth)
Speed
Experiments and Simulations
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22. Experimental Machining Forces Silicon Nitride GS 44
Uncut Chip Thickness
Thrust Force > Cutting Force
Mostly Brittle Material Removal
at larger depths of cut
(> 1 micron)
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23. Forces and Depth of Cut
Simulation Results: 25 m/min, -5 degree rake angle,
Tool Tip 10 microns (completely ductile deformation)
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24. Forces and Feed - Simulations
Force ratio changes with uncut chip thickness
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25. Experimental Results Mostly brittle material removal
Thrust Force > Cutting Force
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26. Cutting Force/Chip area (GPa) Cutting Force/Chip area (GPa)
Comparison of Results
Experiments
Depth of cut (m)
Cutting Force (N)
chip area×10-12 (m2)
Cutting Force/Chip area (GPa) 10
4.61
92.86
49.64 5
1.27
34.56
36.75 1
0.29
4.63
62.18
Simulations
Depth of cut (m)
Cutting force (N)
chip area×10-12 (m2)
Cutting Force/Chip area (GPa) 10
100
2820
35.46 5 70
1410
49.65 1
13.62
282
48.30
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27. Forces and Cutting Speeds Simulations
Feed 20 microns, Zero Degree Rake, Tool Tip Radius 10 microns
Some thermal softening effects
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28. Temp. and Speed
High temp. not required for ductile behavior
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29. Pressures in the Chip Formation Zone
High Pressures required for ductile behavior
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30. Temp., Press., Feed Cutting Speed 6 m/min, Tool Tip Radius 10 microns,
Zero Degree Rake Angle
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31. Pressure and Depth of Cut
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32. Future Work
Apply a powerful laser to generate considerable heat and thus soften metallic phase.
If desired result obtained, try to apply to real machining process.
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33. Acknowledgement NSF Award Abstract – DMR #0203552
FRG: High Pressure Phase Transformations of
Silicon, Germanium and Silicon Nitride
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