Ground Vibration Testing of Airplane Pylon-Store Dynamics using Laser Doppler Vibrometer and ...

82 Pages·2006·1.07 MB·English

by  Joseph Dupuis

GROUND VIBRATION TESTING OF AIRPLANE PYLON-STORE DYNAMICS
USING LASER DOPPLER VIBROMETER AND ACCELEROMETER
TECHNIQUES
By
JOSEPH DUPUIS
A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE
UNIVERSITY OF FLORIDA
2003
ACKNOWLEDGMENTS
I would like express my sincere gratitude to all of my committee members for
their support on this project. In particular I would like to thank Dr. Richard Lind
for providing daily guidance throughout the course of the entire project without
which success would never have been realized. I would like to thank Dr. Andrew
Kurdila and Roque Salas from SEEK EAGLE for arranging the project and providing
logistic support. I would also like to thank Dr. Christopher Niezrecki for offering his
suggestions for improving the quality of the work presented.
I offer special thanks to the technicians at the STEM facility at Eglin Air Force
Base for their assistance in implementing the test.
Finally I would like to thank all my friends, family and coworkers for their
support in various ways throughout the years.
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TABLE OF CONTENTS
page
ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii
LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v
LIST OF FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi
ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x
1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Test Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2 TEST HARDWARE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1 Test Article . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.2 Excitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.3 Accelerometers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.4 Laser Doppler Vibrometer . . . . . . . . . . . . . . . . . . . . . . . . 14
2.5 Data Acquisition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.6 Facility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3 DATA ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.1 Modal Analysis Software . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.2 Using Laser and Accelerometer Data Cooperatively: Method 1 . . . . 20
3.3 Using Laser and Accelerometer Data Cooperatively: Method 2 . . . . 25
4 GVT ON PIDS-3 AND MK-84 . . . . . . . . . . . . . . . . . . . . . . . . . 28
4.1 Test Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
4.2 Consideration of Excitation Signals . . . . . . . . . . . . . . . . . . . 30
4.3 Accelerometer Response to Vertical Excitation . . . . . . . . . . . . . 32
4.4 Accelerometer Response to Lateral Excitation . . . . . . . . . . . . . . 40
4.5 Laser Response to Lateral Excitation . . . . . . . . . . . . . . . . . . 46
4.6 Scan Response to Lateral Excitation . . . . . . . . . . . . . . . . . . . 50
5 GVT ON PIDS-3 AND GBU-10 . . . . . . . . . . . . . . . . . . . . . . . . . 55
5.1 Test Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
5.2 Accelerometer Response to Lateral Excitation . . . . . . . . . . . . . . 56
iii
6 SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
BIOGRAPHICAL SKETCH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
iv
LIST OF TABLES
Table page
2–1 Dimensions for the MK-84 and GBU-10 Munitions . . . . . . . . . . . . . 9
3–1 Effect of FFT Size on Modal Parameters . . . . . . . . . . . . . . . . . . . 24
4–1 Modes Measured by Accelerometers for Vertical Excitation to MK-84 . . . 33
4–2 AutoMAC of Accelerometer Response for Vertical Excitation to MK-84 . . 34
4–3 Modes Measured by Accelerometers for Lateral Excitation to MK-84 . . . 41
4–4 AutoMAC of Accelerometer Response for Lateral Excitation to MK-84 . . 42
4–5 Modes Measured by Laser for Lateral Excitation to MK-84 . . . . . . . . . 47
4–6 AutoMAC of Laser Response for Lateral Excitation to MK-84 . . . . . . . 48
5–1 Modes Measured for Lateral Excitation to GBU-10 . . . . . . . . . . . . . 57
5–2 AutoMAC of Accelerometer Response for Lateral Excitation to GBU-10 . 57
v
LIST OF FIGURES
Figure page
2–1 MK-84 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2–2 GBU-10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2–3 PIDS-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2–4 Excitation System for GVT . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2–5 PCB Accelerometer Model 352C67 . . . . . . . . . . . . . . . . . . . . . 13
2–6 Accelerometer Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2–7 Polytec Scanning Laser Doppler Vibrometer . . . . . . . . . . . . . . . . . 14
2–8 IOtech Data Acquisition System . . . . . . . . . . . . . . . . . . . . . . . 15
2–9 STEM Facility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3–1 Laser and Accelerometer Frequency Response Functions . . . . . . . . . . 21
3–2 Beam Second-Bending Mode Shape . . . . . . . . . . . . . . . . . . . . . 22
3–3 Effect of FFT Size on FRF of Laser Data . . . . . . . . . . . . . . . . . . 22
3–4 Effect of FFT Size on Curve Fit . . . . . . . . . . . . . . . . . . . . . . . 23
3–5 Poorly Animated Mode Shape . . . . . . . . . . . . . . . . . . . . . . . . 24
3–6 Frequency Response Function at Various Locations . . . . . . . . . . . . . 25
3–7 Separate Subsection FRFs . . . . . . . . . . . . . . . . . . . . . . . . . . 26
4–1 Excitation Points for GVT of MK-84 . . . . . . . . . . . . . . . . . . . . 28
4–2 Measurement Points for GVT of MK-84 with Accelerometers . . . . . . . 29
4–3 Measurement Points for GVT of MK-84 with Accelerometers . . . . . . . 29
4–4 Measurement Points for GVT of MK-84 with Laser Vibrometer . . . . . . 30
4–5 Transfer Functions for Random Burst and Sine Sweep Excitation . . . . . 31
4–6 Transfer Functions for 10 and 35 lb Force Excitation . . . . . . . . . . . . 31
4–7 Transfer Functions for 1024 and 2048 Point Transforms . . . . . . . . . . 32
vi
4–8 Transfer Functions at Representative Locations . . . . . . . . . . . . . . . 33
4–9 Mode Shape at 46 Hz Measured by Accelerometer for Vertical Excita-
tion to MK-84 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
4–10 Mode Shape at 183 Hz Measured by Accelerometers for Vertical Excita-
tion to MK-84 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
4–11 Mode Shape at 312 Hz Measured by Accelerometers for Vertical Excita-
tion to MK-84 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
4–12 Mode Shape at 443 Hz Measured by Accelerometers for Vertical Excita-
tion to MK-84 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
4–13 Mode Shape at 507 Hz Measured by Accelerometers for Vertical Excita-
tion to MK-84 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
4–14 Mode Shape at 671 Hz Measured by Accelerometers for Vertical Excita-
tion to MK-84 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
4–15 Mode Shape at 831 Hz Measured by Accelerometers for Vertical Excita-
tion to MK-84 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
4–16 Mode Shape at 899 Hz Measured by Accelerometers for Vertical Excita-
tion to MK-84 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
4–17 Mode Shape at 946 Hz Measured by Accelerometers for Vertical Excita-
tion to MK-84 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
4–18 Transfer Functions at Representative Locations . . . . . . . . . . . . . . . 40
4–19 Mode Shape at 186.3 Hz Measured by Accelerometers for Lateral Exci-
tation to MK-84 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
4–20 Mode Shape at 296.9 Hz Measured by Accelerometers for Lateral Exci-
tation to MK-84 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4–21 Mode Shape at 356.59 Hz Measured by Accelerometers for Lateral Ex-
citation to MK-84 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4–22 Mode Shape at 548.51 Hz Measured by Accelerometers for Lateral Ex-
citation to MK-84 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
4–23 Mode Shape at 680.64 Hz Measured by Accelerometers for Lateral Ex-
citation to MK-84 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
4–24 Mode Shape at 858.42 Hz Measured by Accelerometers for Lateral Ex-
citation to MK-84 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
vii
4–25 Mode Shape at 969.66 Hz Measured by Accelerometers for Lateral Ex-
citation to MK-84 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
4–26 Transfer Functions at Representative Locations . . . . . . . . . . . . . . . 47
4–27 Mode Shape at 86.41 Hz Measured by Laser for Lateral Excitation to
MK-84 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
4–28 Mode Shape at 135.71 Hz Measured by Laser for Lateral Excitation to
MK-84 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
4–29 Mode Shape at 189.05 Hz Measured by Laser for Lateral Excitation to
MK-84 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
4–30 Mode Shape at 239.73 Hz Measured by Laser for Lateral Excitation to
MK-84 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
4–31 Mode Shape at 239.73 Hz Measured by Laser for Lateral Excitation to
MK-84 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
4–32 Mode Shape at 293.35 Hz Measured by Laser for Lateral Excitation to
MK-84 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
4–33 Mode Shape at 185 Hz Measured by Laser Scan on Fin of MK-84 . . . . 52
4–34 Mode Shape at 185 Hz Measured by Laser Scan on PIDS-3 Pylon . . . . 53
4–35 Mode Shape at 290 Hz Measured by Laser Scan on Fin of MK-84 . . . . 54
5–1 Measurement Points for GVT of GBU-10 . . . . . . . . . . . . . . . . . . 55
5–2 Measurement Points for GVT of GBU-10 . . . . . . . . . . . . . . . . . . 56
5–3 Transfer Functions at Representative Locations . . . . . . . . . . . . . . . 56
5–4 Mode Shape at 35.78 Hz Measured for Lateral Excitation to GBU-10 . . . 58
5–5 Mode Shape at 84.71 Hz Measured for Lateral Excitation to GBU-10 . . . 59
5–6 Mode Shape at 169.71 Hz Measured for Lateral Excitation to GBU-10 . . 59
5–7 Mode Shape at 275.53 Hz Measured for Lateral Excitation to GBU-10 . . 60
5–8 Mode Shape at 288.44 Hz Measured for Lateral Excitation to GBU-10 . . 61
5–9 Mode Shape at 358.7 Hz Measured for Lateral Excitation to GBU-10 . . . 61
5–10 Mode Shape at 535.62 Hz Measured for Lateral Excitation to GBU-10 . . 62
5–11 Mode Shape at 571.56 Hz Measured for Lateral Excitation to GBU-10 . . 63
5–12 Mode Shape at 650.52 Hz Measured for Lateral Excitation to GBU-10 . . 63
viii
5–13 Mode Shape at 719.88 Hz Measured for Lateral Excitation to GBU-10 . . 64
5–14 Mode Shape at 838.73 Hz Measured for Lateral Excitation to GBU-10 . . 64
5–15 Mode Shape at 882.25 Hz Measured for Lateral Excitation to GBU-10 . . 65
5–16 Mode Shape at 953.44 Hz Measured for Lateral Excitation to GBU-10 . . 66
ix
Abstract of Thesis Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Master of Science
GROUND VIBRATION TESTING OF AIRPLANE PYLON-STORE DYNAMICS
USING LASER DOPPLER VIBROMETER AND ACCELEROMETER
TECHNIQUES
By
Joseph Dupuis
May 2003
Chair: Dr. Richard C. Lind
Major Department: Mechanical and Aerospace Engineering
Ground vibration testing is the process of determining a structure’s dynamic re-
sponse to a force input. This information is useful for model development and stability
analysis. Modal analysis is performed to extract modal parameters, such as natural
frequencies, dampings and mode shapes, from measured responses. These responses
are typically measured using either a laser Doppler vibrometer or accelerometers.
The U.S. Air Force is interested in performing a ground vibration test or GVT
on F-16 wing stores. Two stores of particular concern are the the MK-84 and the
GBU-10 bombs when these munitions are attached to the wing with a Pylon Integrated
Dispenser, also known as a PIDS-3. During recent flight tests this configuration was
observed to sustain damage in the form of cracks in various places on the stores and
pylon. This thesis documents a ground vibration test performed on this coupled struc-
ture using laser and accelerometer measurements to determine the modal parameters
and underlying dynamics of the structure.
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