proceedings of the first annual symposium for
TRANSCRIPT
NASA/CP-1999-209137
Proceedings of the First Annual
Symposium for Nondestructive Evaluation
of Bond Strength
Compiled by
Mark J. Roberts
U.S. Army Research Laboratory
Vehicle Technology Directorate
Langley Research Center, Hampton, Virginia
Proceedings of a symposium sponsored by the
National Aeronautics and Space Administration,
Washington, D.C., and held at
Langley Research Center, Hampton, Virginia,
November 4, 1997
National Aeronautics and
Space Administration
Langley Research CenterHampton, Virginia 23681-2199
May 1999
Available from:
NASA Center for AeroSpace Information (CASI)7121 Standard Drive
Hanover, MD 21076-1320
(301) 621-0390
National Technical Information Service (NTIS)5285 Port Royal RoadSpringfield, VA 22161-2171
(703) 605-6000
PREFACE
Thirteen nondestructive evaluation (NDE) experts met for the First Annual Review ofNASA's NDE of Bond Strength Program at LaRC, NDE Sciences Branch on November 4,
1997. The goal of this research is to nondestructively determine quantitative strength levelsin structural bonds. The Symposium was held to review both "in house" NDE research and
work performed by sponsored university grantees. The grants reviewed were:"Nondestructive Determination of Bond Strength", The Johns Hopkins University (Dr.Robert E. Green and Mr. Tobias P. Berndt); "An Ultrasonic Technique to Determine the
Residual Strength of Adhesive Bonds", Northwestern University (Dr. Jan D. Achenbachand Mr. Zhenzeng Tang); "Ultrasonic Nondestructive Characterization of AdhesiveBonds", The Georgia Institute of Technology (Dr. Jianmin Qu and Mr. Larry Jacobs). Aninvited presentation, "Preliminary Attempts to Detect Weakness of Adhesive Bonds", wasgiven by Dr. Donald Price of the Computational Industrial Research Organization (CSIRO,Sydney, Australia). Several technologies and approaches were presented including"Adhesive Model with Varying Interfacial Layers Using Longitudinal Ultrasound", by Mr.Robert Anastasi and Dr. Mark J. Roberts, ARMY-VTC, "Surface Contamination
Monitoring using Optically Simulated Electron Emission (OSEE)", Dr. Christopher S.Welch, College of William and Mary. Nonlinear ultrasonics is being investigated as a
possible lead technology for nondestructively detemining bond strength. The Symposiumproceedings are published in this NASA Conference Publication.
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In House Research
Investigate a non-contacting approach.
- Laser Ultrasonic System
(Under construction.)
Introduce large amplitude strains
- Mechanically orThermally
Utilize Laser UT System to try to probe the
bonding layer while under stress to measurecomponents of the higher order elasticconstants.
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Table 2. CASE 2 - ANALYTICAL PARAMETER lIST
Ve_Jty (v) Oens#y (o) Impedance (z) Thickness (d)(m/s) (kg/m 3) (xl0 e kg/m 2 aec) (m)
k:ll_rend 6370 2710 17.25 Secr_nfinite
2100 1120 2.35 70.0 x 10"e
Inledace Laym:*
Mocllka 100% 2100 1120 2.35 7.0 x 104
Modll-b 50% 2100 560 1.18 7.0 x 104
Model-c 20% 2100 220 0.47 7.0 x 104
Model-d 10% 2100 110 0.23 7.0x 104
*P_ of _ dens#y, cotrll_oondlng impedance calculated using z = p v
Table3.CASE1-NUME_CALPARAMETERLIST
ThCkne_ V, Vs _U8 ._/8 ZU Z_Z(m) (m/s) (m/s) #Z Elements (m) (m) (ns¢) (m) AYIAZ
3.17x 10"a 6370 3110 • 123 5.3 x 10"5 2.._ x 10"s 2.861 2.59x 10_ O.B
7.00 x 104 6370 3110 1 5.3 x 10"s 2.59 x 10"s 1.060 7.00 x 104 3.68
7.00 x 10"s 2100 1050 9 1.75 x 10"s 8.75 x 104 3.542 7.77 x 104 3.31
7.00 x 104 6370 3110 1 5.3 x 10"s 2.59 x 10"s 1.060 7.00 x 10"e 3.68
4.77x 104 6370 3110 185 5.3 x 10"s 2.59x 10 "s 2.861 2.58 x 10"s 0.998
_q:)OF = 316160 nz = 320 ny -- 494 At =f 1.060 nmec
Table 4. CASE 2 - NUMERICJ_ PARAMETER LIST
Thickness VL Vs ,tUB _s/8 Z_r _7.(m) (m/s) (m/s) #z IEk._x_s (m) (m) (nsec) (m) AYIZLZ
3.17 x 10"_ 6370 3110 82 7.96x 10"s 3.88x 10"s 4.296 3.87x 10"s 1,000
7.00 x 10"e 2100 1050 1 2.625 x 10.5 1.313 x 10"s 3.280 7.00 x 10"e 5,531
7.00 x 10"5 2100 1050 6 2.625 x 10"s 1.313 x 10"e 5.316 1.166 x 104 3.319
7.00 x 10"s 2100 1050 1 2.625 x 10-5 1.313 x 10"s 3.280 7.00 x 104 5.531
4.77 x 10.= 6370 3110 123 7.96 x I0 "s 3.88 x 10"s 4.304 3.882 x 10"s 0.9074
#DOF = 140812 nz = 241 ny -- 329 _1 :l 3.280 nsec
21
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22
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Figure 3. AdhesivelyI_xleclslmcSumgeorneay wl_ tk_leapectumtrareduce¢p,ds_ ec,_on (acmerm_ are alumkx_).
23
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24
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27
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15
28
Optically Stimulated Electron Emission (OSEE) for Bond Inspection
Christopher S. Welch
Applied Science Department
College of William and Mary
i. Description of OSEE
Optically Stimulated Electron Emission (OSEE) is a
non-destructive inspection technique which has been developed by
NASA and its contractors to verify the cleanliness of bonding
surfaces. With OSEE, verification occurs immediately prior to
applying adhesive and forming the bond. OSEE was developed to
address the realization that a major cause of failure in bonded
joints is contamination of the bonding surfaces prior to bond
formation.
The technical basis for OSEE is that the efficiency of the
process of photoelectron production by ultraviolet light is highly
sensitive to the state of the emitting surface, so that small
amounts of contamination can greatly change the photocurrent
produced by a given amount of light. It was found that the charges
corresponding to the emitted photoelectrons could be attracted to
a positively charged anode, eventhrough a considerable amount of
ambient air. This discovery permitted design of non-destructive
instrument (shown schematically in Fig. I) to inspect bonding
surfaces in the manufacturing setting. In Fig. i, an anode,
biasing battery, ammeter and circuit ground connection are added
to the photoelectron-emitting surface. The resulting complete
circuit is the basis of the measuring instrument, with the current
measured by the ammeter becoming the measurement.
2. OSEE and Bonds - A Brief History at NASA
In the early days of the NASA Space Shuttle, it was
recognized that the bond between the solid rocket booster case and
its insulation/fuel package was critical to the operation of the
motor, and that a failure in this bond during operation could
easily lead to a burn through the case and a possible mission
failure. This realization drove a need to inspect the bonding
surfaces prior to the application of the first layer of insulating
material to the steel of the case. This need was particularly
urgent with refurbished motors. Small residual amounts of the
rust-preventative used on the motors following recovery from the
ocean were shown to weaken the bondline, if they remained after
cleaning (Gause, 1989). Inspection of the bonding surface, which
was grit-blasted after degreasing, was difficult, and optical
methods of inspection designed for smooth surfaces were not
applicable, because the surface was not smooth, but grit-blasted.
A scientist working in the research laboratory of the prime
contractor (Smith, 1979) recognized the potential for OSEE to
address the inspection, and the idea was put into development
(Smith, 1986) and deployment, with a commercial firm coming
29
forward to build and supply the equipment. In rapid order, aninstrument was designed, configured, and put into service
inspecting Shuttle solid rocket motor casings.
After some time, field experience with the OSEE instrument
brought out a need for some improvements. It became evident that
the commercial firm which was supplying the instruments, a small
business with little other commercial base, lacked the research
infrastructure to undertake an extensive investigation into the
factors which produced variations in the OSEE readings. The
instrument was important to the NASA mission, so the task of
investigating the factors was assigned to the NDE laboratory at
NASA Langley Research Center. This investigation became known as
the OSEE science base study.
3. Findings of the science base study
The science base study identified several factors which
affect OSEE readings as well as putting into perspective the
factors governing OSEE operations. To show that variability is not
an intrinsic part of OSEE measurements, an effort was made to
reduce variability. This effort eventually achieved
reproducibility within 1 percent of the OSEE current in two
measurements on a clean surface over time (Fig. 2). The biggest
factor in attainingreproducibility was the use of an argon purge
to reduce photochemistry in the measurement region (Welch, et al.,
1992). Reproducibility led to the ability to perform comparative
experiments for factors which might produce variability. These
comparative experiments produced several findings of significance.
It was determined that the only portions of the lamp spectrum (a
low-pressure mercury lamp) which produced significant photocurrent
were the 185 nm line and the 254 nm line, the 185 nm line
producing about 95% of the total current. OSEE variations on clean
surfaces were found to be sensitive to variations in the work
function of the surface. Sensitivity was found to even trace
amounts of humidity in the atmosphere surrounding the measurement,
and to small variations in the temperature of the lamp envelope.
Also, the voltage-current characteristic of the OSEE process was
found and related to early work in gaseous electronics. A
verification of the sensitivity to contamination was done, and a
sample cleaning technique developed (Abedin, et al., 1992).
4. Dielectric substrates
In a follow-on to the science base study, a procedure was
developed which achieved reproducible OSEE data on a nonconducting
substrate. This procedure, named charge replacement, led in part
to a patent (Yost, et al, 1995), because it opened the opportunity
for OSEE to inspect all surfaces, not just metal surfaces (Welch
and Yost, 1995). This ability permitted performance of a study of
the applicability of OSEE to inspect surfaces of electronic
assemblies for residual solder flux in various assembly processes
under study by the electronics production industry (Welch, 1995).
3O
5. OSEE Instrumentation Development
With the improved understanding of the operation of OSEE,
authority was extended to design and build an improved OSEE
instrument which would incorporate the new understanding into its
design. The instrument first authorized was a scanning instrument
which would be suitable for examining an entire solid rocket motor
case segment (about 800 square feet of area) with a resolution of
1 inch in a time of 20 minutes. This procedure was chosen for
compatibility with the existing inspection, which is done with a
resolution of 6 inches. The linear speed of this inspection is 75
feet/minute. The scanning instrument consisted of a six-channel
linear array of OSEE sensors arranged with a single lamp and
suitable for mounting on a robotic arm (Welch, et ai.,1993; Perey,
1995). Figure 3 shows some data from tests of the demonstration
unit on a test bed with a test sample made from three plates of
two-inch width, the center plate of which was cleaned. The figureshows the first scan of 60SEE channels and the difference between
the first and second scans, again for 6 channels. The
responsiveness, reproducibility and dynamic range of the
measurement are clearly indicated in the figure. Figure 4 shows
the response values inferred from a stepped contamination sample
with steps at a 1 inch spacing. Following the successful
demonstration, the six-inch probe was placed in the development
queue in other facilities, with the NDE Laboratory at NASA Langley
Research Center assuming a supporting and consulting role.
The next demonstration project authorized was an inspection
instrument which could be used for spot inspections over a 1 inch
diameter area which might well be in a difficult-to-access area ofthe motor. It was to be an instrument which could be used
practically by a single operator with access to the motor on a
series of catwalks or a scaffolding used in production settings.
While the intercalibration issues of the earlier instrument were
avoided in the new instrument configuration, other issues were
addressed associated with weight, portability, manipulability,
establishingthe purge, confirming measurement geometry prior to a
measurement, event timing for a single measurement and operator
feedback (Perey, 1997). This instrument is configured as a small
base unit, a small tank of argon and an inspection _gun" (Figure
5) at the end of an umbilical. It has several modes of operation,
including a single spot measurement, a continuous measurement
mode, in which the position can be varied, and an automatic mode
appropriate for robotic inspections. This instrument is expected
to be operational as a demonstration unit late this summer.
6. 0SEE application tests.
At the present level of development, OSEE has been found to
be very sensitive to certain kinds of contamination. As a rule, it
seems from several studies of substrate-contaminant pairs that
greases and hydrocarbon films on metal substrates are good
31
candidates for OSEE inspection. In the studies, when OSEE issensitive to contamination, the level of sensitivity has been
found to be less than 1 _g/cm 2 (the limit of our ability to control
contaminant thickness on samples) or on the order of _g/cm 2.
However, OSEE has also been found to be relatively insensitive or
even confusing with some contaminant-substrate pairs. In view of
the variability in sensitivity and lacking a complete physico-
chemical model of OSEE response to contaminants, it is appropriate
to perform a responsiveness study to likely contaminants in each
inspection setting for which OSEE inspection is being considered.
Several such studies have been done to date, and the beginning of
an OSEE sensitivity library could be formed. The OSEE measurement
portion of these studies is anticipated to become substantially
faster, cheaper and more convenient with the completion of the
instrument under development at NASA Langley Research Center.
7. Future research and development
The virtues of OSEE for surface inspection are that no
mechanical contact with the surface is required, that its reading
is immediate on inspection and that it can be performed in factory
environments. This makes OSEE very attractive for production
settings.
With even a simple low pressure mercury lamp, OSEE response
comes from two widely separated spectral lines. These may be
called high energy (for the 185 nm line) and low energy (for the
254 nm line) OSEE. From some experimental observations and
theoretical considerations, it is reasonable to suppose that the
two responses indicate different surface properties. For example,
the high energy response may be more sensitive to contamination
film thickness while the low energy response may be more sensitive
to the work function of the substrate. Exploring the spectral
response of OSEE has the potential to broaden the surface
characterizations which can be addressed with OSEE inspections.
Surface science has developed a host of techniques which can
describe surface films and particulate contamination, in many
cases, to the level of a few atoms. Some of these techniques use
the same photoelectrons that OSEE uses, but have the additional
ability to describe the energy and polarization of the emitted
electrons. These techniques generally require substantial care in
sample preparation, and samples have to be extracted which can be
placed in high vacuum chambers. It would make sense to use the
power of surface science techniques to verify hypotheses about the
operation of OSEE, so that a theory of its sensitivity can be
developed and refined.
One surface science method, with commercially available
equipment called PEEM, produces data related to OSEE, using
ultraviolet light and collecting photoelectrons. This came from
earlier work, such as that of Baxter and Rouze (1973), on an
instrument called a photoemission electron microscope. This
delelopment shows clearly that microscopic features of interest
are visible with variability in photoelectron emission. Some
correlation has been found with fatigue processes and the
32
formation of slip lines, attributed to fractures of oxide layers.Most of this work uses electron imaging lenses to obtain theimages of photoelectron emission variations, and so these methodsmust be used in a high vacuum environment, to permit undisturbedelectron trajectories. To develop comparable data in the ambientpressure environment of nondestructive testing, a scanning OSEEsystem similar to those in the new instruments is an appropriatedevelopment goal.
8. Summary
Optically Stimulated Electron Emission (OSEE), a surfaceinspection technique introduced by NASA and its contractors toaddress immediate problems in the manufacture of the SpaceShuttle, seems to have untapped potential as an inspection devicefor many production settings, where surfaces have just beenprepared prior to forming bonds. The failure of such bonds hasbeen shown in many cases to be due to surface contamination, andOSEEprovides a rapid, non-contact method of assessing thesurface. To tap the potential, application studies are needed,These studies can be greatly facilitated by a new instrument which
incorporates what has been learned in recent studies of OSEE
operation.
References:
Abedin, M. N., C. S. Welch and W. T. Yost, _OSEE Responses on D6AC
Steel due to Sample Preparation," Review of Progress in
Quantitative Nondestructive Evaluation, Vol II, D. O, Thompson
and D. E. Chimenti, eds, Plenum Press, New York, 1992, pp.
1799-1805.
Baxter, William J. and Stanley R. Rouze, "Photostimulated
exoelectron emission from slip lines: A new microscopy of metal
deformation," Journal of Applied Physics 44(10), October,
1973, pp. 4400-4404.
Gause, R. L., _A Noncontacting Scanning Photoelectron Emission
Technique for Bonding Surface Cleanliness Inspection," NASA
TM-100361, February, 1989.
Perey, D. F., "The Design and Development of a Third Generation
0SEE Instrument," Proceedings of the Ist Aerospace
Environmental Technology Conference, Huntsville, AL, 1994, pp.
533-540.,NASA Conf Publication 3298, March, 1995.
Perey, D. F., "An OSEE Based Portable Surface Contamination
Monitor, " Proceedings of the Second Aerospace Environmental
Technology Conference, A. F. Whitaker, M. Clark-Ingrain and S.
L. Hessler, eds., Huntsville, AL, 1996, pp. 533-540.,NASA Conf
Publication 3349, March, 1997.
33
Smith, T., "Quantitative Techniques for Monitoring SurfaceContamination", in Surface Contamination - Genesis, Detection
and Control, Plenum Press, New York, (1979) pp. 697-712.
Smith, Tennyson, Apparatus and Technique for Monitoring
Photoelectron Emission from Surfaces, U. S. Patent No.
4,590,376, May 20, 1986.
Welch, C. S., M. N. Abedin and W. T. Yost, _Optically Stimulated
Electron Emission: Current-Voltage Response and Spectral
Sensitivity," Review of Progress in uantitative Nondestructive
Evaluation, Vol ii, D. O, Thompson and D. E. Chimenti, eds,
Plenum Press, New York, 1992, pp. 2155-2162.
Welch, C. S. and W. T. Yost, "Enhancements and Extensions to OSEE
Contamination Inspection," Review of Progress in Quantitative
Nondestructive Evaluation, Vol 14, D. O. Thompson and D. E.
Chimenti, eds., Plenum Press, New York (1995), pp. 1641-1648.
Yost, W. T., C. S. Welch, E. J. Joe and B. B. Hefner, Quality
Monitor and Monitoring Technique EmployingOptically
Stimulatee Electron Emission, U. S. Patent No. 5,393,980,
February 28, 1995.
Welch, C. S., Feasibility Study of OSEE Inspection for Flux
Residue on Electronics Assemblies," Soldering & Surface Mount
Technology 19, February, 1995, pp. 8-11.
Welch, C., W. Yost, S. Gasser, E. Joe, D. Perey, E. Scales, J.
Bly, T. Goodman, W. Hefner, X. Pascual, F. Stone, C. Kennedy
and B. Batten, _OSEE Instrument: Design and Construction,"
Technical Interchange Meeting, Huntsville, AL, (1993,
unpublished).
34
ULTRAVIOLETLAMP
_LI
m
T
Figure i. Schematic circuit of an OSEE instrument (after Gause,
1989). Shown is a direct current circuit with a battery, a
means of measuring current and a surface illuminated with an
ultraviolet light. The circiut is completed by the
photoelectrons which cross the'gap to be collected at the
positively charged anode.
300
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50
0
0 100 200 300 400 500
Time (s)
Figure 2. Two superimposed curves of OSEE current vs time. These
data, from a copper sample in an argon atmosphere, show the
degree of reproducibility which can be obtained with OSEE in
favorable circumstances.
35
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a
b
I I I I i
0 50 100 150 200 250 300
Sample Number (Approx 46 Samples. per inch)
Figure 3. Results of two successive scans of the 6-channel OSEE
instrument over a test object consisting of three plates, the
central one being clean and the two outer plates being dirty.
The results in a are the data for all 6 parallel channels from
one of the scans, while those in b are the differences between
the two scans. The largest differences, in the high gradient
region of the data, are attributed to differences in scanner
position rather than differences in OSEE readings.
36
---- 250
t-
O 2000
150o')t-O
100_o
n-50
ILlI11CO 00 I I I I I
0 5 10 15 20 25 30
Contamination Level (lxg/cm 2)
Figure 4. Averaged OSEE data over a stepped sample of varying
contamination amounts. The dotted line between the clean area
and the nominal 5 _g/cm 2 indicates an increase in sensitivity
in that region.
Manual Trigger
(Momentary)
&Line DriverCkt,etc.
ShutterAssy.
Electrometer Assy.
Path
Pick-up Grid
Figure 5. Cross-section of the probe head in the first prototype
of the hand-held OSEE instrument. The light path is about 1
inch in diameter. (after Perey, 1997)
37
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67
AN ULTRASONIC TECHNIQUE TO DETERMINE TId_RESIDUAL STRENGTH OF ADHESIVE BONDS
J. D. ACHENBACHPRINCIPAL INVESTIGATOR
ZHENZENG TANGRESEARCH ASSISTANT
CENTER FOR QUALITY ENGINEERING ANDFAILURE PREVENTION
NORTHWESTERN UNIVERSITY
EVANSTON, IL 602,08-3020.
GENERAL OBJECTIVE
To develop an ultrasonic nondestructive technique to assess theadhesive bond strength of adhesive layers by analyzing the nonlinearbehavior that accompanies adhesive deterioration. The work on thisproject is both analytical and experimental in nature.
68
69
Reference:
M. Goland and E. Reissner, "The Stresses in Cemented Joints",J. Appl. Mech, March 1944, ppA17-A27.
Replace adhesive layer by distributions of springs
Mu "4---- {ix _'-
t_dx
t_ dx
M! _ _ "Cdx
VI _ dx
x= i_(u.- u_), (_=K(w- wl)
7O
0.10 , ,m
0.08
0.06
0.04
0.02
0.00
-0.02-1.00
Interface traction without cracks
I ' I " I ' I ' I ' I ' l "'
KcmI = Kjm_ : o.o25,vo = o, w=: o.1
-0.50 0.00 0.50 t .00
71
u_
c- 00 "-'
_,_ CD>
c- 0
- ,d ,_o
72
0
0
Center ;or Quality Engmeenng ant Failure Freventlon N or[nwes;ern Unlvers;t 2
THEORETICAL MODEL
f(t)
p(t)
pl.c!
pl, c!
f(t)
m
/
O'y ly=O- --
1
1-Jr- O'y=O- ]
(_ -- Z'/]y=O+ -- /"/ly=O-
+ _[_=o-] (1)
(2)
(3)
#-_5 (4)
,,3- "7,80 (5)
73
Center for Quality Engineering and Failure PreventionI I II
Northwestern UniversityI
v1 (y. t) = e i(''t-ky) (6)
(7)
(8)
where c_ --
R(w) =ic_ + 27 ic_ + 1
(9)
N
i---1
(10)
(11)
I II I I
74
Center for Quality Engineering and Failure PreventionI I
Northwestern UniversityII
EXPERIMENT SETUP
OscilliscopeTek TDS 520
Pulser ReceiverModel 5055PR
GPIB
Computer
S
Pe
c
i
m
.en
A
MTS Machine
Loading Direction
75
Center for Quality Engineering and Failure PreventionII I
Nortl_westem UniversityI
TYPICAL NONLINEAR ELASTIC _- -- /k RELATION
2 I I I I I I | I !
¢-
¢3
t=.
p-
1.8
1.6
1.4
1.2
1
0.8 L
0.6
0.4
0.2
00
fI I
0.2 0.4! J I ! I I I
0.6 0.8 1 1.2 1.4 1.6 1.8
Extension /_
2
I
76
I
(_,enter fcr Quality Englneenng and Failure Prevenr',crI
SPECIMEN
Northwestern Univers_[v
..... .
1. Adhesive (connection)2. adhesive (testing layer)3. AI block (adherend 2)4. AI Tube (w_er tank)5. Screw
6. AI block (adherend 1)
7. Transducer
I| I
77
1. Aluminum piece a2. Aluminum piece b3. Strip a4. Strip b5. Delay block6. Shear wave transducer
7. Adhesive layer a8. Adhesive layer b
78
Center for Quality Engineering and Failure Prevention Northwestern University
Methodology of Nonlinear Behavior Study
Use different fatigue cycles to generate different
severities of degradation.
By varying the static load, ultrasonic measurements
allow us to get the slope of the 7- -- /% curve at several
points.
dq- o"
dA 5
i|
0.1
0.I
jo,0.1
O_
0.1
+ I012 1114 I Olll I 1,2O.I 1.4
79
p_h
_L
_L
_h
L_
q_
C_
mmm
mmm
LLm
LL!
mJLu
O
80
!
c onter for Quafity Engineering and Failure F;eventionII I I II
Error Function Behavior
I
Northwestern UniversityI
2200Error Behavior for the 50-50 Epoxy Layer Simulation
20OO
1800
1600
E 1400E
= 1200
1O130
8OO
600
4000.008
..................!...................i....................i....................!.................
iiiiiiiiiiiiiiiiiiiiiilliiiiiiiiiiiiiiiiiiil.......•.......i.................i
, 1 ,, i I f
0.01 0.012 0.014 0.016 0.018Parameter Gamma
N
i=1
I I I I
81
Center for Quafity Engineering and Failure PreventionI I
Simulated Signal vs. Measured Signal
Northwestern Universlty
E
5O
40
30
2O
10
0
-10 ..........................
-20 ............. • ............
-30 ....................... _"
-..40 I I0 100 200
Simulated Signal vs. Measured Signal for 50-50 Epoxy Layer
I I ! _ !
. .: ............ ............. - ....................... ............
V ...... \° •
I
300
.. --.- Measured i
1 I , I
400 500 600 700
Data Points
8OO
I I I
82
Center for Quality Engineering and Failure PreventionI
Northwestern UniversityI I .....
Load vs. Effective Modulus for 50-50 Epoxy Layer
10
9
8
6¢/J
¢D_>"= 4
LU3
2
00
Load vs. Effective Modulus for 50-50 Epoxy Layer
I _ ! i J
........., ........ .,........_........, ........ _ ........_........x........_ ........_........
.........!........ it .......i......... i......... !o ......i....... !......... i...... i........
O
O
1 | ! ! I !
100 200 300 400 500 600.
Actual Load Applied (ibs)
•x..... o..cYc._;e............o 50Kcycles
.._.•. 1,00K.Cycles......
I " , I ......... ] ..
700 800 900 1000
I I I
83
Center for Quality Engineering and Failure PreventionI
Northwestern UniversityI
Reconstructed Stress-Strain Relation (50-50)
16
14
12
10
¢1rt
8¢/)a)
G)
6
Reconstructed Stress-Strain Relation for 50-50 Epoxy Layer
4
2
0
!
0.05 0.1 0.15 0.2 0.25
Strain (%)
I I I I III I I
84
Center for Quafity Engineering and Failure PreventionI I
Northwestern University
Load vs. Effective Modulus for 70-30 Epoxy Layer
7
Q.(.9"-" 6
"0o 5
= 4tot,=._
UJ
Load vs. Effective Modulus for 70-30 Epoxy Layer10
......... : ......... ,.......... ........... . .......... . .......... . .......................................
....... t ........ l ........ I ...... m ...... ® ....... ® ........ ® ........ 0 ........ X
. 0
- 0
_'= "0 ......... ,,,-.4
.......... - ,,,-.4
......... : ......... ........... . .....................................................................
2 ............................ .......... "........................ x : ocycle ................
• . o- 50K c),cles
1 ............................. i.......... :...... ............... !....... _ 'i00K_yci_ !........
0 I ! v v v v0 100 200 300 400 500 600 700 800 900 1000
Actual Load Applied (Ibs)
85
Center for Quafity Engineering and FailurePreventionI
Northwestern University!
Reconstructed Stress-Strain Relation (70-30)
Q.
v
tD
u_
16
14
12
10
8
6
4
2
C0
Reconstructed Stress-Strain Relation for 70-30 Epoxy Layer
! |
i /
: : -
0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2
Strain (%)
IIII I I II
86
0
0
Qu
tj
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m qll_n
0
0
F:m
toim
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t" "0
e- c-
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87
' O
"_ ._
°i.1_
_ CJ
88
CURRENT WORK (2nd year)
1. Load adhesive bond in shear in MTS machine.
2. Ultrasonic test with shear waves.
3. Shear-fatigue adhesive bond.
4. Use ultrasound to detect onset of nonlinearity.
FUTURE WORK (3rd year)
Apply shear load using low-frequency ultrasound, orlow-frequency electromagneUc transducer.
89
Nondestructive Determination
of
Bond Strength
Tobias P. Berndt and Robert E. Green, Jr.
Center for Nondestructive Evaluation
The Johns Hopkins University
Department of Materials Science and Engineering
Acknowledgments."
Funding by NASA Langley and CNDE
Samples provided by BOEING
November 4, 1997
9O
ellU
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I il.
("'i:LLIr_Z 14-0rn
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91
Proposed Techniques
Linear Ultrasonic Waves
)_ Nonlinear Ultrasonic Waves
Acoustic Emission
Acousto-Ultrasonics
Non-Contact Ultrasonics
Tap Testing
Vibrational Techniques
92
i
Im
X,
i i
i
1I
I
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XU,J
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f2
MASTER
m 1
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SAMPLE
f_
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f3
f3
m
m
m
m
m
m
m
m
N _fl
fl " f2
EXPSET04.CDR
94
Single Beam Interaction
a) - Longitudinal Transmission
RECEIVER
:.. \/
; \+'
TRANSMITTER
SFLTT_3.CDR
95
Nonlinear Parameter of Bond Sample #10 C-Scan
96
Surface Displacement as a Function of Input Powe_
I
' AII
I
_ T ,_: : i
I | , I * ;i i : i _ !I I I I , I
! • i , I I
I i : I i |-" I * * I I
I : s I I • II I I I • II : I : ] i I : I
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I I i i I
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1 ! : I : : I
I : I : • : ,I I : 'I I ! ,
I _ I _ ; ' - _- _ .....
_;_L__ I i _5 ] ' - ] C_0 _
0 20 40 60 80 100
Transmitter Drive Voltage (Vpp)
97
Single Beam Interaction
b)- Mode Converted Shear Transmission
RECEIVER
\\
TRANSMITTER
,,.30deg > ANGLE > ,,, 13.5 deg
c) - Mode Converted Shear Reflection
RECEIVER TRANSMITTER
.,,30deg > ANGLE > ,-.13.5 deg
SFSREFL2.CDR
98
Displacement behind tilted (17.5 °) Al-plate
• i
7 i ' i t ' i !" , ...... { /L,_
• t • I : 6 : -" I
t . I: i : i : i a : i
. I ; I : I I . i
. t . I : _ : I . i
............ _ ............ I................... _ ............. t .............. - ............
: I ; I : : ! : o: I , I • t , I : i: i } _. L - 4 , - i . J • t4 , I , _ J ,; : i _ : i . i: _ _ I _ , : I - ,
-- : , , -- ir _ "-_'.. _ ...... , _ : ,
, I
3 'S : ' _............... _ ......... t ............ .._ ....... ,I ......... _ .................. _" ................. -." .......... _- ................... "t-- ................. * ........
I I : I I I
T:_.2 : : _K]'K: i , ! _ : I "• ! " : I '
: : I : I : I : I.................. -. ...................... ;. .............. I. ............ ; ............... I ................................. 4 .................... _ ............... .L ........
; I : I : I : i
: _ I I : I : i
: I : I : I "
0 20 40 60 80 100
Transmitter Drive Voltage (Vpp)
DISPCAL2PGW
99
°%
b0
(mu) _Pm!ldm V _u_tu_3elds!c I
100
i
m,.,
lllU
,(/)
Q,,
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101
Comparison of all BOEING Samples
_" 35 L I
._ 3.0 .................................
" l | i --2 5 I-- .............. ,_.............. ,:............ ---_,__ .............
"_ 2.o ....:...... , - --.........Ply :Samples.._ ... [--- . _, ,, _ P__tU-_ ,, ,_ I
° ! --I"_ I. ; : -__ ---r-,-_----I
I
• __ _ , , ___0.5 - _-7-.............[_lr_ .... i Mode Convert. Shear Wave Transmission I
< I I i f !00 r I 1 i I I
0.0 2.5 5.0 7.5 10.0 12.5 I5.0
[Amplitude of Fundamental] 2 (V 2)
1.25 -) -,_Peel =
-_-_ 0.75 _______ _ __i i T0.25 [
0.000 20 40 60 80 100
Transmitter Drive Voltage (Vpp)
BOE_NLPc.PC;W
102
B-Scan of Receiver at 17.5 ° behind BOEING Sample #19 (good Bond)
Mode Convert Shettr Wuve Tranxmi.cxitm
3.5[_ .....Z>--.3.0k 12.5 _-rl ....... _-T .... _-"k ...... i.... I
_ 2.o ' l
_1.0< 0.5
0.0 .......
0.5
0.40.3
0.2
0.1
0.0
I i i ii i i !I i i i i! , , , t Li
i ..... | " " J i, , , I1 _I__|...., ilr -'V| i I !i i i l i wi , ....... i i • _ f!I i i l.... .f_S" I
I l I I I r I
I i i ii • • i _ i
i i I _ i :
I I I $ I
m t _ i i ii i i i i
i i I i
I I I I l'_l I l I I I I I I I I
-0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2BOE 1902C.I[_GW
B-Scan of Receiver at 17.5 ° behind BOEING Sample #22 (with Peel Ply)
Mode Convert. Shear Wave Tranamission
2.0
1.5 -:- -- ' -I I I I
i i t ii ' i1.0 F1 ..... , i i
I I
0.5 . , ,i I i
I i II I
i i i
0.0
3.0
,-, 2.5>
2.0
1.5<
1.0< 0.5
-0.3 -0.2 -0. I 0.0 O. 1 0.2IIC')1"22¢12C I'_W
Scan Position (in)
BOEI922CpGW
103
I I I
IF
Scan Position (in)
-0.I
i e!
i '2F J
0.0
I
0.1
i >
tl.
"0
_2
0..
E<
\
MCSW D I PGW
104
o,_ _ 0 _ oo _ _ c_l 0-- o o o o o
(A) _'v' _ I V(ATI) zlV / EV
) I |
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I 1 ....l i i I' :
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..... ) i o
I -I I I I I I l I
-- c5 o o c5 d
(A) zv _gIV(A/I) :IV / ZV
L_
105
(All) zl V / _:'v'
106
Comparison of all "CURE" SamplesMode Convert. Shear Wave Transmission
1.0
0.2
0.0
.0.4 0.8 1.2 1.6
[Amplitude of Fundamental] 2 (V 2)
_ 5x<> [
i
- ,0 2O
m i |_
t
>00 <_O <X_© O :' I
40 60 80 100
Transmitter Drive Voltage (Vpp)
C_GAV7C I PGW
107
Summary
It has been shown that Measurements of SampleNonlinearities in Water Immersion are possible if the
Power of the injected Ftmdamental Wave is limited to
prevent Interference due to excessive NonlinearBehavior of the Water.
Nonlinear Ultrasonic Studies on Adhesive Lap Joint
Samples have been performed using Water coupling.
Lap Joints containing Polyester Peel Plies show
Nonlinearities up to four times higher than Ordinary
Samples.
First tests on Samples containing Bond Degradationsdue to Variations in the Cure Cycle of the Adhesive
appear to be more difficult.
108
Preliminary Attempts to Detect Weaknessof Adhesive Bonds
Acousto-elastic Measurements Using Plate. Waves
Don Price
CSIRO Telecommunications & Industrial PhysicsSydney, NSW, Australia
109
Boeing/CSIRO Joint Research Program
NDT of Bonded Structures
Previous work:
s Delamination of AI,AI bonded joints
(and detection of hidden corrosion).
• Detection of foreign material inclusions in
composite laminates.
• Measurement of elastic constants of composite
laminates (high temperature agei_).
• Measurement of bond strength.
People involved:
• Barry Martin
• Jill Ogilvy• Don Price
• Wayne Woodmansee
110
\
\
\
\
\
f
/
/
/
/
/
0
111
,.-., t::u_E_3
w
0E_
0
_'_ .
°_ ,_
E _e-.
o°
o_
112
ij".
113
114
Q
115
116
(D"(D::3
°mm
Q.E
¢.-
03
0
AI base plate
f_
Shffen
i
Stiffen
, I L I I I i I i
5 10 15 20 25
e (degrees)
117
Am
v
m
E
¢-
°_
O0
5
1.050 MHz
F=0
F=4kN
F=8kN
F= 12kN
....... F= 16kN
............ F=24kN
1.045 MHz
1.040 MHz
1.035 MHz
1.030 MHz,,;
1.025 MHz
1.020 MHz
".oo
I , !
10 15
Incident angle _) (degrees)118
I
20
(2)
--'i°_
E
c-
CO
5
1.050 MHz
1.045 MHz
1.040 MHz
1.035 MHz
o
1.030 MHz
1.025 MHz
1.020 MHz
'oO
! t I
10 15
Incident ancjle (-) (degrees)119
F=0
F=4kN
F=8kN
F= 12kN
....... F= 16kN
............ F=24kN
L I
2O
(I)
o_
E
°_
Or)
15
AI base plate
F=0
F=4kN
F=8kN
F= 12kN
- F 24 kN
F 32 kN
Stiffener #5 (Peel ply).
//
Stiffener #2 (Good bond)
2O
I . J
25 30 35
e (degrees)
120
"O
Q.E
a3¢.-
°_
r.f)
15
A! ba
n"_k J
Stiffener #5 (Peel ply) • "
jStiffener #2 (Good bond)
, I , I
20 25 30
e) (degrees)
F=0
F=4kN
F=8kN
F= 12kN
F= 16kN
F = 24 kN
F=32 kN
35
121
--1°_
c_E
cCl¢-c3r_
°_
O3
15
r%O. Z.,
/AI base plate
F=0
F=4kN\ .... F=8kN
F= 12kN
- F 24 kN
F 32 kN
F
Stiffener #5 (Peel ply)
\
Stiffener #2 (Good bond)
20 25
O (degrees)
3O
I
35
122
E
°_
6
m ° _ _ • .°o
0.990 MHz
0.985 MHz
0.980 MHz
0.975 MHz __,,
0.970 MHz __,
0.965 MHz f__
8 10 12 14 16
Incident angle [9
F=0F=4kNF=8kNF= 12kN
i !
18
123
# • ° ° o
0.990 MHz _ .......... "
F=0F=2kNF=4kNF=6kN
6 8 10 12 14 16
Incident angle e
i I
18
124
..-,,.,-_t_. ,,.o._. t_/c4_p
::3o_
t_
E
¢-
o_
03
F=0F=2kNF=4kN
AI base plate F = 6 kN..... F=8kN
12 kN
Stiffener #1 (Good
Stiffener # (Peel ply)
Stiffener #4 (Peel ply) ,,'.z';"
6 8 10 12 14 16
12_ hera
I
18
--5
E
¢t3¢.-
-- F=0---- F=2kN----F=4kN--° F=6kN
F 8 kNF 12 kN
I , I _ I , I , I , I .
18 20 22 24 26 28 30
e {degrees)
J
32
126
AI baseplate
\
F=0F=2kNF=4kNF=6kNF=8kNF= 12kN
E
c-
Stiffener #1 (Good bon
Stiffener #3 (Peel ply) /
Stiffener #4 (P'ee 7
, Ill 'i . . i
18 20 22 24 26 28 30
g (a_r_.es)
I
32
127
REPORT DOCUMENTATION PAGE _,m_RN,_ nma-Q I,,//_
_, m,m_,r_ ._a m_._.mr_ _rmaura neeaea, aria compmmg ano rm.mmng _-_eoo_ _ _. _ana comments mgardw_ thls burdan estima_ or any omer
_-aqxx'_, zla _ _ r._m, my, _u_te ]L-,u4, mlmglon, vA Z;_2-4302. and to me r.x.ce of Management _ Budget. Paperwork Reductkm Project (0704-0188),W=_n_ton, DC 20503.
4. TITLE AND SUB'.rLE 5. FUNDING NUMBERS
Proceedings of the First Annual Symposium for Nondestructive Evaluation
of Bond Strength 552-18-11-03
6. AUTHOR(S)
Mark J. Roberts, Compiler
7. PERFORMINGORGANIZATIONNAME(S)ANDADDRESS(ES)
NASA Langley Research CenterHampton, VA 23681-2199
9.SPONSGR;_3/MONITORINGAGENCYNAME(S)ANDADDRESS{ES)
National Aeronautics and Space AdministrationWashington, DC 20546-0001
11. SUPPLEMENTARYNOTES
8. PERFORMING ORGANIZATIONREPORT NUMBER
L-17857
10. SPONSORING/I_K)NITORINGAGENCY REPORT NUMBER
NASA/CP- 1999-209137
Roberts: U.S. Army Research Laboratory, Vehicle Technology Directorate, Langley Research Center,Hampton, VA Primarily Viewgraphs
12a. Oi_T_,-_UTION/AVAILABILITY STATEMENT
Unclassified-Unlimited
Subject Category 38 Distribution: NonstandardAvailability: NASA CASI (301) 621-0390
13. AB_)T-OtOT (Ma._mum 200 words)
121). DISTRIBUTION CODE
Quantitative adhesive bond strength measurement has been an issue for over thirty years. Utilization of nonlinearultrasonic nondestructive evaluation methods has shown more effectiveness than linear methods on adhesive
bond analysis, resulting in an increased sensitivity to changes in bondline conditions. Correlation to changes inhigher order material properties due to microstructural changes using nonlinear ultrasonics has been shown andcould relate to bond strength. Nonlinear ultrasonic energy is an order of magnitude more sensitive than linear
ultrasound to these material parameter changes and to acoustic velocity changes caused by the acoustoeleasticeffect when a bond is prestressed. This increased sensitivity will assist in getting closer to quantitativemeasurement of adhesive bond strength. Signal correlations between non-linear ultrasonic measurements and
initialization of bond failures have been successfully measured. This paper reviews nonlinear bond strengthresearch efforts presented by university and industry experts at the First Annual Symposium for Nondestructive
Evaluation of Bond Strength organized by the NDE Sciences Branch at NASA Langley in November 1997.
14. SUB.iE_ ¥_.MMS
Nonlinearity, ultrasonics, fatigue, residual bond strength, adhesive bond,
strength modulus, nonlinear parameter, WZT, harmonics, bond cure
17. _Uml • C_s_ATION 18. _:)il_;Ul'g I lr G_I'IIJA I IIt_N 1_. $_'(;4JINI I _ (_;_IPI(_ATI_NOF REPORT OF THIS PAGE OF ABSTRACT
Unclassified Unclassified Unclassified
15. NUMBER OF PAGES
13316. PRICE CODE
A07Z0. LLMIIAllI_N
OF ABSTRACT
UL
tall_ara POrto Z_8 |HOV. Z-89)red.bed by ANSI Std. Z-39-18
296-102
128