Window 4 Test Headlines

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Window 4 Test Headlines

• Low pressure behavior of Window 3 and Window 4
  are very similar!
• Window 4 broke at 151.17psi!

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Low pressure behavior of Window 3 and Window 4
are very similar!
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Window 4 broke at 151.17psi!
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Recent goals addressed by photogrammetry

• Window 3
• Develop a more useful way to view the
  deformation of the window.
• Window 4
• Determine how well the window compares to design
• Compare window shape determined by
  photogrammetry to CMM measurements

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Recent goals addressed by photogrammetry

• Window 3
• Develop a more useful way to view the
  deformation of the window.
• Window 4
• Determine how well the window compares to design
• Compare window shape determined by
  photogrammetry to CMM measurements

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Create whisker plots

• Display the change in the surface from the
  initial, unstressed shape

Window 3
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Pressure
Delta z (mm)
filename

• Whisker length
• z(95psi) - z(0psi)

Window 3
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Animate deformation of the window ...
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Window 3

• By plotting deltas
• (change from initial shape),
• any pattern and window eccentricity is removed.
• Whats left is f(pressure).

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Window 3

• Look for any asymmetry of deformation
• Note
• The scales are different for each of the
  following plots!

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Recent goals addressed by photogrammetry

• Window 3
• Develop a more useful way to view the
  deformation of the window.
• Window 4
• Determine how well the window compares to design
• Compare window shape determined by
  photogrammetry to CMM measurements

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Setup to measure window shape

• Measure the concave and convex sides in same
  coordinate system, moving projector and camera
  from one side to the other

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Difference between measured shape and design
Convex
Concave
Whisker z(measured)-z(design)
Given the design radius of curvature of the
concave and convex surfaces, z(design) was
calculated for the (x,y) position of each target
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Coordinate system
Reference is determined by flange face. This is
the z-plane
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Coordinate system
This is advantageous, because many projected
targets fall on the flange
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Coordinate system
0,0,z is the center of the circle described by
the 6 button targets in the flange
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Problem of convex and concave alignment
convex
concave
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Problem of alignment
convex concave
This makes it difficult to determine the window
thickness
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Solution

• Use VANGO to create a surface model
• VANGO is CADD software for land development civil
  engineering and surveying
• VANGO evolved from Van Dell CO GO
• CO GO coordinate geometry

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Solution

• VANGO uses a TIN (Triangular Irregular Network)
  to create a surface model.

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Solution

• VANGO uses a TIN to approximate the surface
  between measured points.

6mm
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Solution

• Once the surface is modeled, the z coordinate for
  any x,y is available.
• Therefore, the same set of x,y coordinates can be
  used for both sides of the window.
• This facilitates comparing the windows
  dimensions to the design.

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Solution

• Point on triangle is always lt true point.
• This is important to interpret any periodicities
  seen in the data
• period of an oscillation caused by the TIN would
  be 6mm

6mm
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Error calculation
d f(radius of curvature, size of triangle)
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Errors in thickness due to TINworst case(s)
D
D
D
DD-14.6um
DD15um
IDEAL
assumes 6mm chord, so r3mm Rconvex308.44mm
Rconcave300.00mm
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Errors in thickness due to TINintermediate and
best case
D
D
D
DD-0.4um
DD
IDEAL
assumes 6mm chord, so r3mm Rconvex308.44mm
Rconcave300.00mm
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Error bars

• Each point requires a unique error bar
• The error is f(phase between concave and convex
  triangles)

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Error bars

• Error for North and South is greater for large
  radii due to location of alignment slots.
• Here a typical triangle has sides of 6x20x20 mm

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Note that North convex North concave, etc.,
parallel each other
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Results

• The dome is not in the same location wrt flange
  as the design.
• The dome only approximates a sphere.
• The thickness is preserved

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Is the measurement repeatable?Yes.

• Measurements were repeated 3 times.
• Two of those times the MET-L-CHEK was very thin
  and some points were rejected.
• HOWEVER, those points that were measured agreed
  well
• For only one of the three was the TIN created.
• (the one without rejected points - Sashas
  MET-L-CHEK)

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Recent goals addressed by photogrammetry

• Window 3
• Develop a more useful way to view the
  deformation of the window.
• Window 4
• Determine how well the window compares to design
• Compare window shape determined by
  photogrammetry to CMM measurements

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Compare window shape determined by photogrammetry
to CMM measurements

• The two measurement techniques agree to within
  20um for each point.
• This is especially good, considering the window
  was likely not in the same position,
  rotationally, for each test.

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New idea to determine thickness

• Small patch sphere fit
• Fit a sphere to the points near the point in
  question.
• The sphere fit gives the equation of the sphere

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Center thickness with new method

• Result for the center
• z_concave 50.5889mm
• z_convex50.9205mm
• thickness 331.6um

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New idea to determine thickness

• Could do this for any point.
• Chose x,y to be the point in question

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Advantages of CMM over photogrammetry

• Less complicated analysis?

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Advantages of photogrammetry over CMM

• Non-contact
• More information due to greater surface coverage?

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Non-contact
Photogrammetry
CMM
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Greater coverage
Photogrammetry 1000 points
CMM 30 points
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Does the thickness of the MET-L-CHEK affect the
measurements?

• MET-L-CHEK Fluorescent and Visible Dye
  Penetrant Inspection Materials
• MET-L-CHEK beads in matrix of isopropyl alcohol
• Recently learned beads can be as large as 15um
  (previously thought beads were sub-micron)
• Measured effect of thickness of MET-L-CHEK

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MET-L-CHEK

• The only effect is that there are a few more
  rejected points due to insufficient reflection
  when the MET-L-CHEK is applied too thinly.
• The resultant window shape was not affected

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• Note to myself
• R 308.44 and 300.00mm
• window 3 had second transformation for 0.0 per
  circle fit
• Windwo 4 did nto have second transformation