Photogrammetric Deformation Analysis of the H.L Hunley Submarine.

Photogrammetric Deformation Analysis of the
H.L Hunley Submarine.
Benjamin Rennison
Clemson University
H.L Hunley
• Built in Mobile, Alabama
• Weapon of Stealth
• Proof of Concept
• Sank USS Housatonic
• Disappeared just off Charleston Harbor
February 17th, 1864
H.L Hunley – Recovery August 8th 2000
H.L Hunley – Recovery August 8th 2000
H.L Hunley at Warren Lasch Conservation Center,
Charleston, SC.
Construction
Construction
•
•
•
•
•
•
Cast Iron
Wrought Iron
Hot riveted
28 Semi-hemispherical Plates
Port and Starboard Expansion Strake
Weight: 14000 lbs
Site Formation/Structural Integrity
Starboard
Structural Health Assessment
The structural health of the submarine during its rotation was
conducted as follows.
1. Conduct initial structural information research (collect shape and
dimensions).
2. Identify potential areas for structural degradation during rotation.
3. Create FEA model to assess current structural degradation during
rotation.
4. Begin rotation project, perform initial monitoring projects to
establish a baseline.
5. Continue survey’s at every 10 degrees and compare transformation
of points during each survey.
Is it better for the sub to upright?
Are 14 slings be adequate support?
Can we rotate it the sub without structural failure?
THE FINITE ELEMENT MODEL
Simplifying complex geometry
Local Model (Rivet Connection)
•CAD model
•Physical properties are applied to the model
(density, modulus of elasticity, strength, thickness)
•Interactions between the elements is quantified
•MATlab and Abaqus software
Global Model (Overall sub shape)
Predictive Results from Finite Element Analysis
1. The sub would be better supported upright
Compared maximum modeled internal
stresses of the Hunley in slings at a 45⁰ angle
to upright
2. The rotation could be done without breaking
Compared yield strength of known reference
material to modeled internal stresses in a best
case scenario
3. The rotation could break it
Compared yield strength of known reference
material to modeled internal stresses in a worst
case scenario
y
z
y
x
z
COMPUTER MODELING AIDED ROTATION PLANNING
More questions....
YouTube Video Link: http://youtu.be/nZmk4TPDcM8
1. Will the forward conning tower clear the
truss cross brace during rotation?
4. How will the sub move and what will the
stress distributions be like?
2. What density foam is needed?
5. Estimate the pull and release of each
3. What will be the vertical and horizontal
sling?
displacement?
Theoretical turned practical with
test rig and load cell system
θ
O1
y
G
Ts
Tp
x
Vertical and horizontal loads
were calculated from load
cells tension readings
S-beam
Load
Cell
This full scale sectional mockup was made to refine the
computer model
Stern
15
14
y
13
12
z
11
x
9
7
Bow
10
8
6
5
4
2
3
1
Rotation of profile from 45⁰ roll angle to upright position in forty-five 1⁰ increments
(releasing port side only )
Each sling position was modeled separately according to its
profile along the hull
Rotation Plan
Survey Plan
1. Conduct periodic surveys at every 15 degrees and
compare transformation of points during each
survey.
2. Collect initial survey data quickly and respond with
transformation information to the lead engineer.
3. Collect information from visible surfaces.
4. Allow for a maximum of 5mm movement r xyz
• We expect her to move!
5. Will the submarine move into her ‘original’ build
position?
Advantages of Photogrammetry
• The advantages of photogrammetry
for the monitoring project were:
• Safe and non-contact
measuring system, once
targets are in place.
• Short time to data ratio.
• Accurate data collection.
• Able to process results quickly
to advise the rotation
engineers.
• Effective in Hostile and
Unstable Environments.
Aicon DPA Pro
Digital camera
Camera resolution
Data transmission
Measurement accuracy
Picture angle
Illumination
Storage time
Processing unit
Operating system
Accessories
DPA
(Digital
Photogrammetric Analysis)
Nikon D3x with Nikkor 28mm
6048 x 4032 pixels (24.5 mega
pixels)
W-LAN or removable storage
device
2 µm + 5 µm/m (RMS)
3 µm + 7 µm/m (3 Sigma)
74°
White light ring flash
5 images per sec.
high end notebook
Microsoft® Windows® 7
scale
bars,
coded
targets,
standard targets, adapters
Camera Positions Constraints and Survey Set Up
Targets
• All retro targets
• Snap in permanent datum's - Hubbs
Machine
• 14bit reusable coded targets - Aicon
• 14bit disposable targets
Rotation Day
Survey Issues
• Limited constantly visual
surfaces to record
• Targets
• The submarine had to be kept wet
constantly
• This caused our first survey to fail
due to water on the targets.
F3 30°
F4 15°
F4 0°
F5 0°
z
2
11
14
18
22
24
34
40
49
103
104
109
112
121
126
137
146
148
149
1028
1031
1032
1106
y
y
x
z
1.6
1.4
1.2
1
0.8
F3/20°
0.6
F4/10°
0.4
F5/0°
0.2
0
The next time
we find a Civil War Submarine5
• More points
• Better communication with
conservation staff
• Better control of the moisture
on target surfaces
• FEA
• 2.31mm max movement r xyz
y
z
y
x
z
YouTube Video Link: http://youtu.be/4JFOscSYqiY