a)
b)
Blade 1 Hub Blade 2
Rotor
1
2 4
3
7
5 6 8
9 11
10 12
13
14 16
15 17
18 20
19 21 22
1
2 4
3
7
5 6 8
9 11
10 12
13
14 16
15 17
18 20
19 21 22
Bolt Loosening easily seen with DIC The progression of bolt loosening can be seen. The relative displacement due to the loosening of individual bolts can be tracked and displacement monitored. And rotating equipment can be monitored using these image correlation techniques to provide vivid representations of systems in operation with better understanding of response nature.
OPTICAL AND DIGITAL IMAGE CORRELATION TECHNIQUES APPLIED TO
STUCTURAL DYNAMIC AND STRUCTURAL HEALTH MONITORING APPLICATIONS Mark Helfrick, Chris Warren, Pawan Pingle, Chris Niezrecki, Peter Avitabile
DIGITAL IMAGE CORRELATION - DIC Using a pair of calibrated cameras (that are cognizant of each other’s position), a speckled pattern on a structure can be monitored over time to observe changes in the correlation of the pattern as a function of structure deformation.
Changes in the pattern can be monitored and processed to determine deformations that result.
Projectile impact on sheet metal plate is easily detected with DIC
Composite plate damage is easily recognized even though the visual appearance is not obvious.
S t r u c t u r a l D y n a m i c s a n d A c o u s t i c S y s t e m s L a b o r a t o r y
Dr. Peter Avitabile 978-934-3176 [email protected] http://sdasl.uml.edu/ Dr. Chris Niezrecki 978-934-2963 [email protected]
Structural Dynamics and Acoustic Systems Laboratory University of Massachusetts Lowell
ARMY Missile Firing Applications Optical, DIC, Laser methods used along with new approaches for real time operating data expansion techniques
Preliminary feasibility and proof-of-concept tests underway to prepare for actual firing of missile system
3D Laser Vibrometer measurements used for comparison with Digital Image Correlation and RTO Expansion Results
Correlation of Modal Data to FEM is Enhanced with Availability of Abundant Optical Data DIC techniques allows significant number of test data points to be obtained. Correlation to the FEM is greatly enhanced.
Optical test data is plentiful !!!
As many DOF as the finite element model !!!
Right pinhole aperture or
perspective center
Camera
distance
Image points
Object point
Object surface
Right image
plane Left image
plane
Left pinhole aperture or
perspective center
Simplified rendition of the correlation process
Pixel array with intensity values
Image on computer screen
Location of impact
Experimental Setup
Aluminum Beam Connection Pieces
0 1 2
3 4 5
Loosened bolt Nothing Loosened Reference
1st 2nd 3rd 4th
none
1st 2nd
3rd
4th
Bolt Loosened Displacement of Top Edge of Beam
DIC & DP provides abundance of information – systems in operating condition can easily be evaluated
Measured response while rotating can be measured with actual data and removal of rigid body motion
Testing Operating Systems
0 100 200 300 400 500 600 700 800 900 1000-0.025
-0.02
-0.015
-0.01
-0.005
0
0.005
0.01
0.015
0.02
0 100 200 300 400 500 600 700 800 900 1000-0.025
-0.02
-0.015
-0.01
-0.005
0
0.005
0.01
0.015
0.02
nset - 302
aset - 29
Army Helicopter Wing Test Nodes – Curved Side (Laser)
101
102
103104
105
106
107108
109
110111
112
113
114115
116
117
118
119120
122
121
123
124125
126127
128
129
a)
b)
-400
-300
-200
-100
0
100
200
300
400
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4
Dis
pla
cem
ent (
mm
)
Time (sec)
Point 1
Point 22
-6
-4
-2
0
2
4
6
8
10
12
14
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4
Dis
pla
cem
ent (
mm
)
Time (sec)
Point 1
Point 22
a)
b)
-400
-300
-200
-100
0
100
200
300
400
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4
Dis
pla
cem
ent (
mm
)
Time (sec)
Point 1
Point 22
-6
-4
-2
0
2
4
6
8
10
12
14
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4
Dis
pla
cem
ent (
mm
)
Time (sec)
Point 1
Point 22