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Volume 29, No. 3 A DTIC-Sponsored, Department of Defense Information Analysis Center October 2004
NONDESTRUCTIVE TESTING INFORMATION ANALYSIS CENTER
Inside this Issue
Newslet terNewslet ter
Feature Article ............................ 1News From NTIAC ...................... 1NDE Bookshelf ............................ 2Sepcial Team Searches forAircraft Cracks............................. 3
Federal Agency Fields Problems Cont'd on Page 2
NDE Industry News ..................... 52004 USAF ASIP Conference ..... 6Calendar ...................................... 7Call for Papers ............................ 8
DC Yokes and Penetration Depth
δπ µσ
≡1
f
NEWS FROM NTIACNEWS FROM NTIACRFI: COPV Failures
NTIAC is initiating a new study into the
failure of composite overwrapped pressure
vessels (COPVs), and would like to gather
more information on available COPV failure
data from the NDE community. For the
purposes of this study, we would like to
obtain more information on
• Related research studies;
• Existing COPV failure databases;
• Recommended COPV inspection and
certification procedures; and
• Data on the failure modes and their
relative frequencies in COPVs.
Points of contact, suggestions, and
comments are welcome. Interested parties
in industry or in particular the government
are asked to contact George Matzkanin or
Thomas Yolken of NTIAC:
George Matzkanin, Director
Nondestructive Testing Information
Analysis Center (NTIAC)
415 Crystal Creek Drive
Austin, Texas USA 78746
1-800-NTIAC39 (1-800-684-2239) or
1-512-263-2106 Fax: 1-512-263-3530
Email: [email protected]
Thomas Yolken, Associate Director
Washington D.C. Technical Representative
NTIAC
15400 Edward’s Ferry Rd.
Poolesville, MD 20837
Tel: (301)605-0522 Fax: (301)605-0524
In August NTIAC was requested to survey our readership concerning the use
of battery-powered Direct Current (DC) and Half-Wave Rectified Alternating
Current (HWDC) magnetic particle inspections. Specifically, potential
issues have surfaced concerning MT of thick parts of an inch or more in
thickness but potentially anything over 3/8 inch thick with this particular type
of magnetizer.
The issues are believed to stem from the fundamental nature of electromagnetic
fields. The depth of penetration of an electromagnetic field is governed by
several key factors, including the electrical conductivity σ and magnetic
permeability µ of the part being inspected, but also the frequency (cycles per
second) f of the electromagnetic field. Generally speaking, all else being
equal, the lower the field’s frequency the greater its depth of penetration,
although this relationship is mitigated somewhat for many ferromagnetic
materials as the relative magnetic permeability tends to decrease with increasing
frequency. This relationship is often expressed as the “skin depth” δ of the
field:
As a result, a DC or quasi-DC field, with a frequency at or near zero, will
penetrate farther into a sample than will an AC field with a higher frequency.
Based on the skin depth equation, for example, a 10 Hz field will penetrate
nearly two and a half times deeper into a metal structure than a 60 Hz field
before significant attenuation occurs, assuming that the ferromagnetic
material’s relative magnetic permeability does not dramatically change with
the increase in frequency. Although this means that a DC field can in fact be
used to inspect thicker structures and locate sub-surface flaws, it may also be
less able to detect surface-breaking flaws as less of the field is at or near the
Page 2
This document was prepared under the sponsorship of the U.S. Department of Defense, the Defense TechnicalInformation Center, Fort Belvoir, Virginia, under Contract #SPO700-97-D-4003.
To register with NTIAC for a free Newsletter, or to obtain information on material appearing in the Newsletter, contact theNTIAC office at:
Texas Research Institute Austin, Inc.415 Crystal Creek Drive • Austin, TX 78746
We welcome your input. To submit your related articles, photos, notices, or ideas for future issues, please contact:Attn: Chris Coughlin, Editor, [email protected], or use NTIAC's online submission form at http://www.ntiac.com/submit.htm
Approved for Public Release, Distribution UnlimitedAll rights reserved. This document, or parts thereof, may not be reproduced in any form without written permission of the
Nondestructive Testing Information Analysis Center.
Phone: (800) NTIAC-39/(800) 684-2239(512) 263-2106
Fax: (512) 263-3530Email: [email protected]: http://www.ntiac.com
NTIAC Director:
George A. Matzkanin
Editor:Chris R. Coughlin
Design/Production:
Annette M. Pizzini
DC Yokes and Penetration Depth Cont'dDC Yokes and Penetration Depth Cont'd on Page 2
NDE Bookshelf
ASNT Announces 3rd Edition Electromagnetic
Testing
ASNT recently released Volume 5: Electromagnetic Testing of the
Third Edition of their Nondestructive Testing Handbook.
From their website: “The third edition of the NDT Handbook on
ET covers the latest developments in electromagnetic testing, with
emphasis on digital technologies. Principles of theory, application
and instrumentation are presented. Applications chapters for
industrial sectors (primary metals, chemical/petroleum, electric
power, infrastructure and aerospace) are included. Theoretical
chapters explain that all electromagnetic techniques share the same
physical principles. This volume is a must-have for Level II and III
ET inspectors, inspection and quality personnel, those who evaluate
or specify electromagnetic tests, researchers, students, trainers and
teachers.”
surface: a DC field can be thought of as “diluting” or “diving” into
a thick part.
Magnetic particle inspection (and other magnetic inspection
techniques such as magnetic flux leakage) depends on a near
magnetic saturation of the inspected part, in which the part cannot
hold additional magnetic field (at least near the inspected region).
In the presence of a flaw, the part’s ability to hold a magnetic field
decreases slightly, and part of the magnetic field escapes (“leaks”)
into the surrounding environment. This leakage field is detected as
a flaw signal-in the case of magnetic particle inspection, by the
action of the magnetic particles in the presence of the field.
The concern raised about DC and HWDC yokes is a thick steel part
may not be magnetically saturated by a DC field. In the presence
of a flaw, the steel part is still able to accommodate the field even
with the loss of magnetic permeability. In effect, the field is able
to travel below and around the flaw and remain in the part, rather
than leak into the environment where it can be detected. An AC
field doesn’t saturate the part either, but because it isn’t able to
travel below the flaw to the same extent as a DC field, the leakage
field is still detectable.
The problem could potentially be exacerbated by surface conditions;
a part that has been heat-treated, shot peened, or one with advanced
corrosion, for example, may have a lower magnetic permeability
in the surface layer than in the bulk of the part. A DC magnetic field
may then preferentially seek out the deeper parts of the structure,
further reducing the available field at the surface. The same
condition might also occur in the presence of welds, which also
tend to have lower magnetic permeabilities than the surrounding
metal.
As mentioned above, DC yokes do find their uses, being particularly
suited to detecting sub-surface flaws in thinner materials. DC
magnetization is used in other magnetic inspection techniques with
tremendous success. Tank floor scanners and pipeline pigs, for
example, frequently use permanent magnets because DC fields can
better penetrate through cladding, layers of corrosion, and the like.
Another concern is the use of permanent magnets on thicker
materials. Although permanent magnets were not evaluated during
this study, the field that they generate is identical to that of battery-
powered DC yokes; therefore there is a high probability that they
would have the same sensitivity issues on thicker materials.
In and of itself, the phenomenon has long been known-ASNT’s
Nondestructive Testing Handbook, for example, explicitly states
“Alternating current magnetization is more suitable for
detection of outer surface discontinuities because it
concentrates the magnetic flux at the surface. For equal
magnetizing forces, an alternating current field is better
for detecting outside surface imperfections but a direct
current field is better for detecting imperfections below
the surface.”
—ASNT NDT Handbook, Volume 5: Electromagnetic
Testing, p. 241
What is new is the growing use of battery-powered DC yokes in the
field - the portability and convenience of that type of equipment is
clear. What isn’t clear is what effect this growing interest in DC
yokes has on flaw detection. Please contact NTIAC to share your
insights and comments.
NDE Bookshelf Cont'd on Page 3
Page 3
October 2004
Special Team Searches For
Aircraft CracksMaster Sgt. Andrew Gates
455th Expeditionary Operations Group Public Affairs
Editor’s Note: The following article originally appeared on the Air
Force Link website, and illustrates not only how critical NDT is to
the military’s mission, but also offers a glimpse into the trade-offs
made when NDT is moved from the shop to the field.
BAGRAM AIR BASE, Afghanistan (AFPN) — All combat
aircraft go through extreme stresses when completing their
missions. Those stresses can cause metal fatigue — tiny cracks
in the joints and welds of the frame or invisible fractures in the
metal.
The sooner these invisible cracks are found, the safer the aircraft
will be.
Finding those cracks in a deployed environment, where every
aircraft is critical and ensuring they are fully operational is of
premium importance, and is the mission for three Airmen here.
The nondestructive inspection team is part of the fabrication
flight and uses various techniques to find cracks in the metal on
aircraft here, said Senior Airman Ryan Michalec, of the 354th
Expeditionary Aircraft Maintenance Squadron.
”We use different scientific methods to find those cracks that
can’t be seen by the unaided eye, as well as those which can,”
he said.
The tools the team uses are fairly similar to those they use at
home; however, the tools here are portable.
”We had an X-ray machine that we couldn’t bring because of its
size,” said Staff Sgt. Brooke Wilke, a team member. “The
portable equipment takes a little more time, on occasion. For
example, inspecting the A-10 (Thunderbolt II) main landing
gear wheel bolts (takes) a little more time with the magnetic
particle unit we have here instead of the equipment we would
use at home.”
This gives team members experience with many different pieces
of equipment.
”I’ve gotten a lot of training [that] I wouldn’t have at home,”
said team member Airman 1st Class Kevin Louie. “I have
gotten the chance to work with other services and on other air
frames, [too].”
Special Team Cont'd on Page 4
Nondestructive Testing Handbook, Third Edition:
Volume 5, Electromagnetic Testing
Author(s): Udpa, Satish S. (technical editor); Moore, Patrick O.
(editor)
Publisher: ASNT
Year: 2004
Pages: 536 (hardcover)
ISBN: 1-57117-046-4
Available as hardcopy, CD, or bundled hardcopy and CD.
Springer-Verlag Publishes
Aerospace Materials Book
As part of their Springer Series in Materials Science, Springer-
Verlag has a new book available on the nondestructive
characterization of materials with a focus on aerospace. From
Springer’s description:
“With an emphasis on aircraft materials, this book describes
techniques for the material characterization to detect and quantify
degradation processes such as corrosion and fatigue. It introduces
readers to these techniques based on x-ray, ultrasonic, optical and
thermal principles and demonstrates the potential of the techniques
for a wide variety of applications concerning aircraft materials,
especially aluminum and titanium alloys. The advantages and
disadvantages of various techniques are evaluated. An introductory
chapter describes the typical degradation mechanisms that must be
considered and the microstructure features that have to be detected
by NDE methods. Finally, some approaches for making lifetime
predictions are discussed. It is suitable as a textbook in special
training courses in advanced NDE and aircraft materials
characterization.”
Nondestructive Materials Characterization: With
Applications to Aerospace Materials (Springer Series in
Materials Science, V. 67)
Author(s): Norbert G. H. Meyendorf, Peter B. Nagy, Stanislav I.
Rokhlin, Stanislav L. Rokhlin
Publisher: Springer-Verlag
Year: 2003
Pages: 416 (hardcover)
ISBN: 3540405178
Available as hardcopy.
NDE Bookshelf Cont'd from Page 2
Page 4
NDE Industry News Cont'd on Page 5
Special Team Cont'd
Airman 1st Class Kevin Louie uses a special light to monitor a
crack on an A-10 Thunderbolt II frame here. Airman Louie is a
nondestructive inspection technician assigned to the 354th
Expeditionary Aircraft Maintenance Squadron. (U.S. Air Force
photo by Master Sgt. Andrew Gates)
The goal for the team is to avert
catastrophic problems without
tearing up the airplane to find
them.
”It takes us a few minutes to find
cracks; it may take some time for
a maintenance crew to get to and
repair,” said Sergeant Wilke.
The team uses many different processes to find metal fatigue.
For instance, with one technique, the technician places a long,
thin probe on the aircraft part.
”The probe creates a magnetic current in the metal. We can read
changes in that current [called an eddy current] to determine
where the cracks are,” Airman Michalec said.
He explained the process by using the analogy of throwing a
stone into still water. The stone causes eddies in the water, and
any obstruction in the water will cause a disruption in the
smooth progression of the eddies.
Another technique uses ultrasonic sound waves to locate cracks.
”If there’s a crack in a part, you get a signal loss or a reduced
signal from the ultrasound, if you use this technique,” Airman
Louie said.
Not everything is as technically complex. One of the techniques
used most often by the team is oil analysis, where the technician
checks how much worn metal is in the engine oil by burning a
sample in a special machine.
Staff Sgt. Brooke Wilke reviews results from an oil sample
analysis. She is a nondestructive inspection technician
assigned to the 354th Expeditionary Aircraft Maintenance
Squadron. Technicians test oil samples from each aircraft
engine daily to help determine its mechanical condition. (U.S.
Air Force photo by Master Sgt. Andrew Gates)
”We can determine if an engine is
starting to go bad by examining the
oil,” Sergeant Wilke said.
“Sometimes you can go a long time
before getting a ‘hit’ indicating a
deteriorating engine, and then you
might have one or two in a few
weeks.”
So far, in the four months the team has been deployed to
Afghanistan, it has had two “hits” on A-10 engines and one on
an MH-47 helicopter transmission, Sergeant Wilke said.
"The level of flying hours here (generates) a lot more activity
on the aircraft [because] each plane flies regularly,” she said.
“That makes a lot more oil samples for us to check.”
Keeping the aircraft safe is extremely important to the team.
”I want to do anything I can to prevent a show-stopper —
something that will keep the aircraft from doing its mission,”
Airman Michalec said. “If no one was checking, we might have
more mishaps. This job is really important. It makes me feel
good to know I have such a vast impact in keeping the plane
operational.”
“If no one was checking, we might have
more mishaps. This job is really
important. It makes me feel good to
know I have such a vast impact in
keeping the plane operational.”
Special Team Cont'd on Page 4
Page 5
October 2004
Industry News Cont'dSpecial Team Cont'd from Page 4
Industry News Cont'd on Page 6
The focus on nondestructive inspections sets the team apart
from other services as well.
”In most of the other services, this job is in addition to the
maintainers’ normal job,” Airman Michalec said. “We are
dedicated to this mission and are specifically trained to do it.”
NDE INDUSTRY NEWSNDE INDUSTRY NEWS
GE Inspection Technologies Completes
Acquisition of Hocking NDT
General Electric Inspection Technologies announced in early
August that they had completed their acquisition of Hocking NDT,
an English eddy current OEM. Their press release follows.
GE Inspection Technologies, a division of GE Transportation, has
completed its acquisition of Hocking NDT Limited (Hocking),
after receipt of all required regulatory approvals. The transaction,
terms of which were not disclosed, was completed on July 31,
2004.
Hocking, located in St. Albans, England, is recognized
internationally as an innovative designer of high-quality eddy
current products, ranging from hand-held instruments and probes
to small systems. Its products are used in the aerospace, rail, oil and
gas, automotive and metal manufacturing industries. Additional
information about Hocking can be found at http://
www.hocking.com.
“We are very excited about this opportunity,” said Chris Hocking,
Managing Director of Hocking. “The acquisition of Hocking by
GE Inspection Technologies brings together two companies focused
on improving the businesses of our customers. Hocking’s eddy
current products complement GE Inspection Technologies’
industrial radiography and ultrasound capabilities. Hocking and
its eddy current expertise allow GE Inspection Technologies to
quickly solve its customers’ NDT application problems.”
“The acquisition of Hocking is strategic to GE Inspection
Technologies,” said Jeff Nagel, President of GE Inspection
Technologies. “It allows us to offer our customers additional
inspection technologies and equipment to help them improve their
manufacturing and repair productivity as well as the predictive
maintenance capabilities of their field assets. GE has a strong
history in the development and application of eddy current and
other non-destructive testing technology and equipment to support
its businesses. The purchase of Hocking provides GE with an eddy
current platform from which to bring this eddy current array,
pulsed eddy current and other NDT technology to customers
worldwide.”
GE Inspection Technologies is a global leader in technology driven
inspection solutions that deliver customer productivity, quality,
and safety. The company designs, manufactures and services
radiographic, ultrasound and eddy current equipment to test
materials without deforming or damaging them. Its products are
used in a wide range of industries, including aerospace, energy,
chemical/petrochemical and automotive. GE Inspection
Technologies is headquartered in Huerth, Germany. More
information can be found at http://www.GEInspection
Technologies.com.
Contacts:
Dirk Snauwaert
Manager, Global Communications
GE Inspection Technologies, GmbH
Tel: +1.513.552.4683
Deborah Case
Media Relations
GE Transportation
+ 1.513.243.0094
Zetec Introduces ZR-1 Robot System
Editor’s Note: Zetec unveiled their new ZR-1 Robot System at the
23rd EPRI Steam Generator NDE Workshop in Chicago. Their
press release follows.
Zetec, Inc., a leading supplier of nondestructive test (NDT)
equipment introduces the ZR-1 Robot System for Inspection and
Repair of Steam Generators - a single robotic manipulator system
that is built to perform eddy current inspection and remain installed
for any needed follow-up maintenance or repair. By using only one
Page 6
For information about the U.S. Department of Defense Information Analysis Centers (IACs), visit the DoD IAC HUB page athttp://iac.dtic.mil/ . This directory outlines the IAC Program as a whole including its mission and examples of the types ofproducts and services the IACs provide. It also contains information about each individual IAC including contacts, areas of
expertise, and other pertinent information.
Industry News Cont'd from Page 5 Industry News Cont'd
manipulator the total inspection and repair time is significantly
reduced. Zetec’s ZR-1 is designed to support a wide variety of
third-party toolheads for tube plugging, welding, cleaning, and
tube end expansion. The wrist assembly has a built-in camera for
automatic tube positioning eliminating the need for cameras for
each toolhead. “Hot Shoe” connection technology provides fast
and easy toolhead change-out with automatic toolhead recognition,
minimizes cables, and reduces the time needed to complete the
change-out. Three-axis motion that precisely positions the toolhead
in the manway opening, along with easy toolhead change-out
reduces worker exposure to radiation and radioactive contamination.
When Zetec’s Machine Vision tools software is used with the ZR-
1, automatic tube location functions can be used for inspection,
maintenance, and repair while time-consuming manual jog
maneuvers are eliminated. The ZR-1 is comprised of three modular
components — the rail, mast, and arm – simplifying shipping,
storage, and assembly. Modular component construction makes
installation a one-person job while helping to avoid the possibility
straining injuries.
Contact:
Marga Baird
Zetec, Inc.
Marketing and Communications Specialist
E-mail: [email protected]
Web site: www.zetec.com
Telephone: 425-392-5316, ext. 3210
PQNDT Begins 2004 NDT Salary Survey
Personnel for Quality and Nondestructive Testing (PQNDT), Inc.
is in the process of conducting the 2004 edition of their annual NDT
Salary Survey. Each year PQNDT surveys thousands of NDT
Professionals and publishes the survey, which breaks down the
results not just by industry but also by location and by job title. The
survey also includes data from as far back as 1997 for comparison
purposes.
Last year’s Survey showed gains and losses for NDT. In general,
salaries were up in comparison to previous years, and yet at the
same time benefits were seen to be on the decline, which was
attributed to greater reliance on NDT contractors. Broken down by
industry, testing labs continued to post gains, again attributed to
increasing NDT outsourcing, while the results from the defense
sector continued to send mixed messages.
Interested NDT professionals can participate in the survey by
going to http://www.pqndt.com/survey2004 and filling out the
questionnaire. For more information, contact PQNDT, Inc. 135
Beaver Street, Suite 19, Waltham, MA 02452, Telephone: (800)
736-3841 Fax: (781) 894-1532, Email: [email protected].
The NTIAC Newsletter NDE Industry News section is based in
part on information supplied by manufacturers and service
providers as a service to our readers. NTIAC and the Department
Of Defense can assume no responsibility for its accuracy. Use of
trade names of manufacturers or service providers in this
publication does not constitute an official endorsement of such
products, services or manufacturers, whether expressed or implied
by the Department of Defense or NTIAC.
2004 USAF Aircraft Structural Integrity
Program (ASIP) Conference
This year’s ASIP Conference will be held November 30-Decem-
ber 2 at the Peabody Memphis in Memphis Tennessee. We present
here a brief introduction to the Conference.
This annual conference is sponsored by the Materials and Manu-
facturing Directorate and the Air Vehicles Directorate of the Air
Force Research Laboratory (AFRL), and the Deputy for Engineer-
ing and the Aeronautical Enterprise Program Office of the Aero-
nautical Systems Center (ASC) at Wright-Patterson Air Force
Base, Ohio. It is intended to bring together world leaders in the area
of aircraft structural integrity and associated technologies to ex-
change information on the latest developments in the design and
acquisition of new aircraft systems and the maintenance of aging
aircraft systems in both military and commercial fleets. This is an
unclassified/unlimited attendance open Conference.
For more information, contact Dr. Joseph Gallagher, ASC/EN,
WPAFB, OH at (937)255-5312, by email at
[email protected]; or contact Universal Technology
Corporation (UTC) at (937)426-2808 and ask for the 2004 USAF
ASIP Conference Desk, by fax at (937)426-8755, or by email at
[email protected]. The conference is maintaining a
website at http://www.asipcon.com.
Page 7
October 2004
MEETINGS AND SYMPOSIA CALENDARwww.ntiac.com/calendar.php
2004
October 52nd Defense Working Group On Nondestructive Testing, Crowne Plaza
26-28 Hotel - Detroit Metro Airport, in Romulus, MI. Attendance is restricted to Government
personnel and contractors; others may be invited to give presentations. For more
information, visit the group’s web site at: http://hometown.aol.com/dodndt, or
contact Host Representative Ms. Midge Krueger, U.S. Army TARDEC, COMM
586.574.5563 / DSN 786.5563 / email : [email protected].
November ASNT Fall Conference and Quality Testing Show, November 15-19, Riviera
15-19 Hotel, Las Vegas, Nevada. For more information contact Kelly Wise, [email protected],
1-800-222-2768 ext 227, FAX 1-614-274-6899.
November 30- 2004 Air Force Structural Integrity Program (ASIP) Conference, Peabody
December 2 Memphis, Memphis TN. Abstracts due June 30, 2004; registration is online via the
ASIP website at www.asipcon.com. For further information contact the ASIP
Registration Desk, care of Universal Technologies Corporation, at (937)426-2808.
2005
January 31- 8th Joint NASA/FAA/DoD Conference On Aging Aircraft, January 31-February
February 3 3, 2005, at the Wyndham Palm Springs and Palm Springs Convention Center, Palm
Springs CA. More information on the conference is available from their website
http://www.agingaircraft.utcdayton.com/index.html .
May 2-4 14th International Symposium on Nondestructive Testing of Wood, Hannover
Germany, May 2nd-4th. Deadline for tentative titles and abstracts is September 15,
2004. More information available through the Symposium’s website at http://
www.fh-eberswalde.de/ndt2005.
June 19-24 Third US-Japan Symposium On Advancing Applications and Capabilities In
NDE, Maui Prince Hotel, Maui Hawaii, June 19-24 2005. Deadline for abstracts is
October 8, 2004 at http://www.asnt.org/events/events.htm ; for more information
contact ASNT, PO Box 28518, Columbus OH 43228-0518 or call (614)274-6899.
Page 8
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CALL FOR PAPERS
visit www.ntiac.com/calendar.php for the most up-to-date NTIAC calendar
2004
September 15
14th International Symposium on Nondestructive Testing of Wood, Hannover
Germany, May 2nd-4th. Deadline for tentative titles and abstracts is September 15,
2004. More information available through the Symposium’s website at http://
www.fh-eberswalde.de/ndt2005.
October 8
Third US-Japan Symposium On Advancing Applications and Capabilities In
NDE, Maui Prince Hotel, Maui Hawaii, June 19-24 2005. Deadline for abstracts
is October 8, 2004 at http://www.asnt.org/events/events.htm ; for more informa-
tion contact ASNT, PO Box 28518, Columbus OH 43228-0518 or call (614)274-
6899.