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: matzkanin@ntiac.com

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

yolken.tri@direcway.com

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, editor@ntiac.com, 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: info@ntiac.comWebsite: 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

Dirk.Snauwaert@ae.ge.com

Deborah Case

Media Relations

GE Transportation

+ 1.513.243.0094

Deborah.Case@ae.ge.com

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: mbaird@zetec.com

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: info@pqndt.com.

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

joseph.gallagher@wpafb.af.mil; 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

jjennewine@utcdayton.com. 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 : midge.krueger@us.army.mil.

November ASNT Fall Conference and Quality Testing Show, November 15-19, Riviera

15-19 Hotel, Las Vegas, Nevada. For more information contact Kelly Wise, kwise@asnt.org,

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.