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NDT TESTING TIPS FROM
NDTECH - NEWSLETTER #14 - January 2000


This issue of the Newsletter includes:


1. New IR Camera from Inframetrics

2. Acoustic-Emission Bearing-Fault Diagnostics System

3. Finding Only the Data You Need

4. Pulse-Echo Ultrasonic Imaging Method for Eliminating Sample
Thickness =20

Variation Effects

5. Machine-Vision System Maps Surface Flaws


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The NDTech Newsletter is published periodically by NDTech, a consulting
firm offering nondestructive testing, services, and instruments. This
newsletter is distributed by email and covers brief descriptions of
some useful but less publicized radiographic, ultrasonic, penetrant,
magnetic particle, and other NDT methods. You will automatically
receive the newsletter, at no cost. If you wish to be removed from the
NDTech Newsletter, simply reply with "Remove" as the subject.


To find out more about NDTech and its nondestructive testing consulting
services and instrumentation, visit the NDTech website at
http://www.ndtech.net/

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1. New IR Camera from Inframetrics


An innovative product from Inframetrics of North Billerica, MA is the
SC1000 ThermaCAM=81 handheld infrared camera. This camera can operate as
a standalone camera or as a dedicated real-time digitial system when
interfaced with the company's ThermaGRAM Pro 95 real-time digital image
processing system for Windows 95.

The SC1000 was developed for users in the scientific market who
require high sensitivity and advanced image processing capabilities to
support their infrared imaging and temperature analysis applications.
The unit can provide screen temperature measurement accuracy of better
than +2% or 2 degrees Celsius. It can operate continuously from a
single standard camcorder battery for more than two hours, and an
optional battery belt will run the camera for 12 hours.=20

The focal plane array radiometer weighs six pounds with the power
source and has FLASH PCMCIA compatibility for storage of up to 256
images on a single card. Remote control and focus from a PC or
handheld controller is possible via a serial remote control port.

Inframetrics, established 1975, supplies other thermal imaging and
temperature measurement systems, components, and accessories to
scientific, industrial, aerospace, law enforcement, and military
markets.=20

For more information on Inframetrics, contact the company at:

16 Esquire Rd., North Billerica, MA 01862-2598

Telephone: 508-670-5555

=46ax: 508-667-2702

Website: http://www.inframetrics.com


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2. Acoustic-Emission Bearing-Fault Diagnostics System


A new hardware and software system that uses a sate-of-the-art,
high-frequency Acoustic Emissions (AE) sensore and an innovative AE
signal-processing technique, called Point Process Spectral Analysis
(PPSA), has been developed to help prevent catastrophic failures and
costly down time due to false alarms during bearing testing. In the
past, bearing health monitoring and fault diagnosis within
turbomachinery and drive-train systems have been a significant
technical challenge for the aeronautics and transportation industries.=20
=20

Previous techniques to detect bearing faults could not distinguish
between transientevents related to shaft rotational processes and the
signatures associated with defective bearings. Also, these techniques
did not involve high-frequency, real-time analysis. To overcome these
unique problems, PPSA was developed to meet the high-frequency AE
signal processing and fault detection requirements.=20

Conventional time series representation of an ultra-high frequency AE
signal requires all data to be sampled over the entire waveform at a
high sampling rate. However, PPSA only uses the times occurence of the
transient events, along with their strengths, since these transient
events contain the major dynamic information needed for bearing fault
detection. As a result, PPSA requires much less data to analyze the
frequency-domain behavior than conventional time-series representation.
Additionally, PPSA overcomes the basic limitations of the
fast-Fourier-transform-based spectrum for detecting signal components,
such as widely spaced, narrow transient spike that cannot be
approximated effectively by a sum of sinusoids.=09

PPSA uses the first moment function of time to determine the rate of
transient impulse, threshholding the temporal AE waveforms for
structural failure detection. Next, a mean-lag-jump product,
representing the second moment of a point process, provides a
statistical estimation of the correlation between all pairs of event
occurrences with common time lags. The frequency-domain representation
of the second-moment mean-lag-jump product function is used to create a
spectrumlike function of the point-process. This point-process
spectrum provides a statistical estimation of the event occurrence rate
and intensity distribution as a function of frequency.

The superior detection capability of PPSA over conventional envelope
analysis in extracting bearing signatures from AE transient signal in a
noisy operational enviroment was demonstrated with two
computer-simulation examples and with NASA-providing test data from a
bearing test rig. Three test conditions were used: a good bearing, an
inner rade defect, and a roller defect. PPSA successfully analyzed the
data. The results of these proof-of-concept studies indicated that
PPSA can provide high computational efficiency in processing
ultrahigh-frequency AE signals and is highly suitable for real-time
implementtation. Using this analysis technique qould significantly
reduce the digital signal processor requirement in developing a
low-cost, commercially viable, on-line bearing-diagnostic system.

This work was done by Jen-Yi Jong of AI Signal Research, Inc., for
the Marshall Space Flight Center. For further information, access the
Technical Support Package (TSP) free on-line at http://www.nasatech.com
under the Machinery and Automation category.


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=20

3. Finding Only the Data You Need


If nothing else, the World Wide Web has provided everyone with almost
instantaneous access to a global information database. The problem is
that now there's so much information out there that it's become nearly
impossible to efficiently sort through all of it to find what you
really want and need. WWW-based search engines can help, but because
of the internet's broad appeal, most search engines developed for it
are too broad for the needs of scientists and engineers.

This has become especially important for researchers who need to
quickly find data for their new-product and process-development
efforts or who want to build upon the results made by other
researchers.

Enter scientific on-line resources, such as the recently announced
ScienceBase from Knight-Ridder Information, Mountain View, Calif.=20
ScienceBase is a World Wide Web application designed to give
researchers easy and intelligent access to published scientific
literature. While ScienceBase doesn't search the Web, users can search
through industry periodicals, patent documents, conference papers,
scientific journals, supplier and buyer listings, and a number of
scientific databases.

While this may not sound much different than other database search
engines other than having a broader number of available resources,
ScienceBase's main advantage lies in a built-in search intelligence
that executes expert search commands behind the scenes to retrieve the
desired information. You don't need to be a search expert or take any
training courses as you do for other sophisticated database search
resources. ScienceBase automatically selects the appropriate
databases, looks for related items, refines your search according to
your selection criteria, and then presents the data in a logical
format. To speed things along, it even searches multiple databases
simultaneously.

"We worked with our information-technology professionals to get
around the database vagaries that exist from one database to another,"
says Larry French, director of product development at Knight-Ridder.=20
Since the indexing conventions used by each of the 90 databases
available to ScienceBase could be different from one to the other, the
search engine developers found they had to modify the queries posed to
each database to optimize the user's specific search. The developers
also had to establish an intelligent way to automatically select the
best databases to search for each query.

To provide its users with the best value, ScienceBase only draws from
established reputable databases, including Elsevier Science Publishers,
Derwent, Merck, NTIS, Business Wire, CAS, USPTO, The Royal Society of
Chemistry, and 82 others.

Database queries are easily accomplished. The searcher starts by
selecting a category of interest, then clicks on a hotlink to see the
topics available. Subject categories contain intelligent query
templatesthat you customize; they also perform quick search survey
options that you define.

After you enter your topic interest, you can make additional
refinements from a pull-down menu and determine the number of items you
want to view. You click on the "Submit Query" button and let
ScienceBase do the rest. Cost of each article or record is displayed
on each abstract-no charges are incurred until you make a selection.

"We wanted to minimize the amount of unnecesary information or false
hits that a user would get in a search," says French. "Everything a
user gets should be right on."

For more information:

Telephone: 415-254-7000

Website: http://krscience.dialog.com


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4. Pulse-Echo Ultrasonic Imaging Method for Eliminating Sample
Thickness

Variation Effects (U.S. Patent No. 5,629,865) Inventor: Don J. Roth,
Lewis Research Center


This method for nondestructive ultra-sonic evaluation of materials
measure velocity using a single transducer pulse-echo immersion
systems, automatic scanning, and digital imaging, providing a video
image of the sample in color or gray scale that is a map of a material
property such as porosity fraction. In the immersion method, the
material to be evaluated is surrounded by a liquid and positioned over
an acoustic reflector that is also immersed in the liquid An ultrasonic
wave of a known frequency is transmitted through the liquid and four
separate echoes are recorded and evaluated at each scan point. Each
echo is recieved as an analog waveform that is digitized and stored in
a computer. Before the evaluation scans, nonlevelness and sample
thickness variations are accounted for and eliminated by pre-scans to
insure that the recieved reflections or echoes are within their set
time windows to provide a complete waveform for evaluation and
cross-correlation to acurrately obtain the time-delay data used in
calculating the velocity values.


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5. Machine-Vision System Maps Surface Flaws


A machine-vision system maps surface flaws generated in fretting of a
metal panel or other structural components. The flaws include pits,
gouges, scratches, small protuberances and other features that deviate
from the otherwise smooth or planar surfaces. The machine-vision
system should be useful in many mass-production situations in which
there is a need for quick and accurate detections of flaws on machined,
polished and otherwise smooth surfaces.

The machine-vision system includes a black-and-white video camera
aimed perpendicularly to the surface to be inspected. The surface is
illuminated, from opposite sides of the line of sight of the camera, by
two rectangular, woven fiber-optic panels that provide evenly
distributed light that is semicollimated and incident in two planes at
acute angles (typically 50 degrees )from the surface. The
camera and the sources of light are mounted on a robotic manipulator
that scans them across the surface, stopping at inspection locations
that are selected consistently with inspection requirements and with
the dimensions of the field of view of the camera. The image data
acquired by the camera and the position data generated by the robotic
manipulator are digitized and sent to a desktop computer for
processing.(see Attachement for a diagram of this process)=20

The relatively smooth unflawed portion of the inspected surface
reflects the illumination away from the line of sight of the camera.=20
Because flaws reflect and diffract the illumination, they appear as
bright spots in the video image. The brightness of a pixel is
digitized on a gray scale of 0 (black) to 255 (white). In processing,
the image data are first Fourier-transformed to filter out background
information. Next, each pixel is binarized by setting its value equal
to 0 if its gray level is =BE32 or 1 if its gray level is =8432. The
binarized pixel values, taken together with the pixel-coordinate
information, and the position data from the manipulator, constitute the
data for a primitive binary map of flaws on the surface.

This work was done by Mark Mueller of Thiokol Corp. Inquiries
concerning rights for the commercial use of this invention should be
addressed to the Patent Counsel, Marshall Space Flight Center;
(205)544-0021.=20

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_______________________________________________________________________

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constitute endorsement or approval of any product.

Copyright 2000 NDTech.




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