april 13, 2004 edward barnard elizabeth hager kevin mccomber jenny lichter
TRANSCRIPT
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April 13, 2004
Edward BarnardElizabeth HagerKevin McComberJenny Lichter
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Outline
Goal Aluminum and Silicone Molds Ceramic Preform and Binders Pressure Vessel and Infiltration Time Calculations Characterization Initial Part Production Challenges and Solutions INITIAL PROTOTYPE ! Future Work Schedule
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Goal
The goal of our project is to design a manufacturing process to create a selectively reinforced metal matrix composite.
This project will take the theory developed in Jess Wannasin’s thesis work and scale up to part production.
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Our Process
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Aluminum Mold
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Centrifuge Setup
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Silicone Mold
Polytek PLATSIL RTV Silicone Rubber 71-10
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Ceramic Preform
SiC 120 Grit(100 µm particles)
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Wannasin
Binder
REMET R-25 binder (Prehydrolyzed Ethyl Silicate)
Sintered a SiC preform at 1500°C for 1hr Cut sintered alumina into preform shape
0.00
400.00
800.00
1200.00
10 15 20 25
Binder Concentration (%)
Compressive Strength (psi)
No Sintering
Sintering for 1 hourSilica
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http://cyberbuzz.gatech.edu/asm_tms/phase_diagrams/pd/sn_pb.gif
Pressure Vessel Calculations
1.5 2.0
0.125
0.50
But…. there’s a catch:
as the processing temperature increases, σUTS decreases
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Swagelok Catalog
New Safety Factors
High Temp = 250 - 300°C
σUTS, High Temp = [0.2 – 0.3] * σUTS, Room Temp
σUTS safety factor
Safety factors sufficient
rinner S. F.
0.75 50.062
515
⎟⎟⎠
⎞⎜⎜⎝
⎛
+−
=22
22
max .. io
ioUTS
rr
rr
FSP
σ Pmax = 730 psi = 50 atm
S. F. : safety factor = 2
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Infiltration Time Calculations
Values: = 2* water, L = 4 inches, DP = 100m
P >> Pthreshold and infiltration times << 5 mins
VP = 0.5 VP = 0.7
Threshold pressures 1.5 atm 3.5 atm
Infiltration times <<1 sec <<1 sec
220
3
2.4
)1(
P
P
VS
Vk
••−
=PV
ktL
P
Δ−
=)1(
22
Darcy’s Law: pressure driven flow Blake-Kozeny equation
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Hardness Tests
Preparation Cut samples with low-speed saw to obtain smooth
surface blade is material specific part is a combination of materials of very different materials
Polished with 5-micron polishing paper
Results: used Rockwell B and H (low hardness) Pure tin-lead: off-the-scale on the low end hardness MMC: on-scale but low MMC is harder than plain tin-lead
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SEM (Scanning Electron Microscopy) Images
SiC particles: 500-600 microns
Fracture behavior
Etchers may be necessary2mm
1mm
100m
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Initial Spin tests
Small amount of Tin-Lead Completed cleared out of runner
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First Try: Incomplete Infiltration
SiC, 120 grit non-sintered preforms 500 rpm Preform floated Not enough metal or pressure
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Challenges and Solutions
Insufficient seal and metal leakage But still safe! Solution: graphite o-ring
Before… After…
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Challenges and Solutions, ct’d
Imbalanced centrifuge Prevents centrifuge from reaching high
rpm, reducing volume fraction of ceramic – high Vceramic is the goal
Solution: add weights to either side
However…. still imbalanced
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Challenges and Solutions, ct’d
Removing part from mold Graphite o-ring stuck to mold interface Long-term Solution: on future production
runs, spray interface with Boron Nitride Short-term Solution: hit part out with
hammer
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INITIAL PROTOTYPE !!!!
Tin Lead, R-25 Binder, 700 RPM = 6 atm Preforms:
sintered SiC, 120 gritsintered alumina
One on left: not full shape because of imbalanced metal distribution (metal left in runner)
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Future Work
Make more parts! Try different ceramics Try different binder concentrations Alter shape of part SEM
Volume fraction of particles Fracture characteristics
Hardness tests
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Projected Work Schedule
2/5 2/12 2/19 2/26 3/4 3/11 3/18 3/25 4/1 4/8 4/15 4/22 4/29 5/6 5/13
MaterialsMetal choiceCeramics choice
Part productionCADAlum. machined mold
Ceramic preform
Volume fraction Time PermittingSize distribution "
Final testing
CODE:Task Sub-task Gradation Testing