A brief description of facility design and equipment, facility usage, and typical investigations are presented for the following: Surface Inspection Facility; Advanced Computer Tomography Inspection Station (ACTIS); NDE Data Evaluation Facility; Thermographic Test Development Facility; Radiographic Test Facility; Realtime Radiographic Test Facility; Eddy Current Research Facility; Acoustic Emission Monitoring System; Advanced Ultrasonic Test Station (AUTS); Ultrasonic Test Facility; and Computer Controlled Scanning (CONSCAN) System

Whitaker, Ann F.

English

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DEVELOPMENT AND APPLICATIONS OF NONDESTRUCTIVE
EVALUATION AT MARSHALL SPACE FLIGHT CENTER
SURFACE _NSPECTION FACILITY:
The Surface Inspection Facility provides magnetic particle,
penetrant, and remote visual inspection capabilities. Both in-
plant and field inspection capabilities exist for all three
techniques. The permanent lab facilities include a large fixed
magnetization station for magnetic particle inspection, a well-
ventilated penetrant inspection station with dark room and
microscopic viewing capability, and a photographic laboratory to
provide documentation of any surface inspection performed. A
wide variety of portable equipment is available for field
inspections. These include: both stiff and flexible-leg
magnetizing yokes and field strength instruments for magnetic
particle inspection, portable penetrant systems, and more than
two dozen flexible/rigid borescopes and fiberscopes.
TYPICAL INVESTIGATIONS:
* Detection of surface and near-surface cracks in weldments
* Detection of seams and foldovers in castings
* Monitoring of bearing wear during SSME operations
* Detection of structural failure in tie-down hardware
ADVANCED COMPUTED TOMOGRAPHY INSPECTION STATION (ACTIS) :
ACTIS is a state-of-the-art computed tomography facility which
uses digital x-ray technology to produce cross-sectional images
of space components nondestructively. ACTIS utilizes four x-ray
sources, a high-speed array processing computer, and variable
system geometry to allow optimization for virtually any test
object up to 4 feet in diameter. Image processing capabilities
include: solids modelling, multiplanar reconstruction, and a
wide variety of statistical and data display options. Images may
be archived to either 1600 bpi magnetic tape or 2 gigabyte
optical disk as desired. Raw scan data may be archived to
optical disk for later recall.
TYPICAL INVESTIGATIONS:
* Characterization of flaws in composite materials
* Detection of inhomogeneities in metal castings
* Verification of internal geometry
* Development of acceptance criteria for SRM nozzle
NDE DATA EVALUATION FACILITY:
The NDE Data Evaluation Facility provides the capability for
mapping NDE data from any source (within or outside MSFC) and
mapping it into a common frame of reference. The data may then
be directly compared to each other or to other data sets, such as
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MSFC COMPUTED TOMOGRAPHY SYSTEM
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mechanical test data. Additional capabilities such as mechanical
test cutting plan development, statistical analyses, and the
correlation of NDE to materials properties are also provided.
These capabilities are provided primarily by the Integrated NDE
Data Reduction System (INDERS), a network of three digital
computers and specialized software. The center of the network is
the MicroVAX II computer, which is capable of handling large data
sets with relative speed. One IBM AT and one Tektronix 2330
Workstation allow some off-line processing of smaller data sets.
TYPICAL INVESTIGATIONS:
* Inspection of SSMEturbine blades for microporosity
* Post-fire evaluation of PAM nozzles
* Development of acceptance criteria for SRMnozzle
* Development of materials properties for carbon-carbon
THERMOGRAPHIC TEST DEVELOPMENT FACILITY
Thermography is and NDE technique which makes use of an infrared
camera system and digital image processor to monitor the infrared
energy emission from the surface of a part under investigation.
The system is capable of resolving minute temperature variations,
of as little as 0.i degrees C. The image processor utilizes a
number of image enhancement techniques to increase temperature
difference resolution.
TYPICAL INVESTIGATIONS:
* Detection of subsurface disbond conditions in samples
representative of the SRM
* Detection of ice formation on the surface of the ET
* Detection of ice during warm up of cryo-cooled SSME
turbopump shafts
RADIOGRAPHIC TEST FACILITY
The Radiographic Test Facility, comprised of a radiation-shielded
cell and adjacent control room, film processing rooms, and a film
reading area, provides the capability of radiographic evaluation
of hardware. Portable lower energy x-ray generating units are
located in the facility, as well as permanently mounted units
capable of producing 150 kev and 320 kev x-rays. Processed film
radiographs are analyzed in the film reading area to detect
possible defects in the parts under investigation.
TYPICAL INVESTIGATIONS:
* Evaluation of welding processes
* Assessment of internal configuration
* Detection of materials anomalies
* Determination of structural integrity
REALTIME RADIOGRAPHIC TEST FACILITY
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Realtime radiography (RTR) eliminates the use of film by
replacing it with an image intensifying unit and video system,
allowing viewing of a radiographic image on a video monitor while
x-rays are passing through the test specimen. The specimen is
placed within a radiation-shielded cabinet, and x-rays are
generated by a microfocus x-ray tube with a maximum energy of 160
kev. The microfocus tube can be used to produce magnified images
of up to 80X. A computer is also an integral part of the system
and equips it with the capability of digitizing and enhancing
images received from video.
TYPICAL INVESTIGATIONS:
* Detection of flaws in composite parts
* Examination of electrical components
* Determination of internal dimensions
* Failure analyses support
EDDY CURRENT _ESEARCH FACILITY
The Eddy Current Research Facility provides the capability to
perform critical development of eddy current applications for
various aerospace components. Specific capabilities include:
measurement of materials surface conductivity, determination of
thickness of films and coatings, interrogation of material
inhomogeneity, and detection of surface or near-surface crack-
like flaws. Refinements in eddy current tooling and adapters
have led to improved detection of flaws in previously
inaccessible locations.
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TYPICAL INVESTIGATIONS
* Nickel/Hydrogen battery cell girth weld investigations
* Weld wire material sorting
* Advances in SSME heat exchanger weld inspection
* Improved detection of flaws in clevis pins
ACOUSTIC EMISSION MONITORING SYSTEM
The Acoustic Emission Monitoring System makes use of transient
electrical energy that is spontaneously released when materials
deform, fracture, or are subjected to stress. Sensors are placed
on the test object and are connected to an acoustic processor.
The processor monitors both the amplitude and number of events
(instances of energy releases) that occur during the test. The
amplitude and number of events are displayed on the Processors
CRT and also in hardcopy form through a strip chart recorder.
TYPICAL INVESTIGATIONS
* FWC Structural Test Article Hydrostatic Test Monitoring
* OMV Composite Tank Test Monitoring
* Carbon-Carbon Nozzle Hydroburst Monitoring
* Monitoring of Test Stand Pressure Vessels and High
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ADVANCED ULTRASONIC TEST STATION (AUTS_
AUTS was designed for ultrasonic inspection of composite material
symmetrical components, with an operational envelope of 8" to 48"
diameter and 2 to 15 foot length. Filament wound motor cases and
bottles, wound in the adjacent Productivity Enhancement Facility
and SRM sub-scale components were primary targets of capability
development. The AUTS employs a dual water squirter coupling
mode, as well as an air-coupling mode. The system has remote
manipulation capability for both transducers and can be operated
in the through-transmission or pulse-echo modes. Scan data is
displayed in color or gray scale at the control console.
Digital, amplitude, or time-of-flight information is displayed
and stored, along with C-scan and depth data. Flaw resolution is
0.250" diameter in 3" of graphite epoxy.
TYPICAL INVESTIGATIONS
* PAM-D Exit Cone Evaluation
* Composite Ballistic Environment Generator (BEG) Motor
Cases
* Solid Propulsion Processing Technology Investigations
* Materials Characterization Investigations
ULTRASONICS TEST FACILITY
The Ultrasonics Test Facility consists of both hand scan contact
and immersion noncontact ultrasonics used in the interrogation of
internal anomalies and bondline integrity. The immersion
capability is quite versatile, providing a capability to perform
either through-transmission or single-side pulse echo scanning of
flat panels or cylindrical and conical shaped objects. The
microprocessor controlled system produces hardcopy ultrasonic
data displays in flat X-Y or polar scans. Portable contact
ultrasonic inspection equipment provides a capability to
ultrasonically interrogate hardware too large for the immersion
tank, or materials that cannot be immersed.
TYPICAL INVESTIGATIONS
* Detection of cracks in weldments
* Characterization of anomalies
* Impact damage tolerance studies
* Internal characteristics of plates and castings
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MSFC AUTOMATED ULTRASONICS STATION
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COMPUTER CONTROLLED SCANNING/OPTICALLY STIMULATED
ELECTRON EMISSION SURFACE CONTAMINATION MEASUREMENTS
Computer controlled contamination scanning (CONSCAN) is a
system developed by MSFC utilizing the optically
stimulated electron emission (OSEE) technique for scanning
solid rocket motor (SRMj cases for surface contamination
prior to critical bonding operations.
The CONSCAN system has the principal advantages of
providing the sensitivity and spacial resolution necessary
when scanning large areas, to ensure that surfaces are
sufficiently free of contaminants that reduce bond
strength.
Scanning t_e surface with the CONSCAN provides a map of
surface contamination levels, which clearly identifies
those areas that require further cleaning; rescanning
after the additional cleaning operation provides results
of that recleaning. This data provides a permanent record
of surface cleanliness levels. This record may be used at
a later date to help identify the specific process during
which contamination occurred and to correlate surface
cleanliness levels with subsequent debond locations.
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Principle of opcration of the OSEEmay be briefly
described as follows. When a surface is exposed to
ultraviolet (UV) light of sufficient energy,
photoelectrons will be released from the surface.
Contaminants on the surface will normally reduce the
number of these photoelectrons which are emitted. The
OSEE sensor has two major components: the el_ctron UV
light source and the electron collector. The
photoelectron current emitted from the irradiated surface
is measured by the electron detector. This current can be
calibrated to the contaminant level on the surface.
The technique as applied to measuring contaminants on
surfaces was developed and reported by Tennyson Smith in
April 1975. He demonstrated both the sensitivity of the
technique t_ contaminant level and bond strength variation
due to contamination.
The technique with MSFC support was utilized on the
External Tank foam debond study in 1979. This technique
was instrumental in identifying the surface contaminant
causing debonds as being silicone which originated from
simultaneous processing of other hardware in the same
building.
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Since the original fnstrument configuration in 1979,
significant OSEE instrument improvements have been
implemented, including: increased signal amplification,
noise filtering, higher output UV light sources, compact
sensor configurations, and computer data analysis.
MSFC initiated a study of the SRM debonds associated with
propellant liner insulation to case, and the carbon and
glass phenolics used in the nozzle. Research studies
determined that the corrosion; protective HD-2 grease used
on the SRMcase has a significant effect on bond strength.
Quantitative levels that affect bond strength and
associated OSEE signal levels were determined by extensive
laboratory testing. This calibration data was
incorporated in the design, development, and
implementation of the CONSCANsystem.
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Development and applications of nondestructive evaluation at Marshall Space Flight Center

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