The NDT TechnicianA Quarterly Publication for the NDT ...

I t has been said that one of theworld’s greatest challenges iseffective and clear communication.Even with good intentions,

statements can be misunderstood ormisinterpreted. This is especially true forterms used in nondestructive testing(NDT). Consider the following exampledialog that might transpire between twoNDT technicians. “We shot the weld butcouldn’t pull a 2T penny so we scrubbed itand had four indications, twodiscontinuities and two defects.” Despitethe words used, no shots were fired, noone was looking for a strange type ofmoney, and no one cleaned the weld. TheNDT technicians were using slang, orjargon commonly used by many in theNDT community. The information passedin that short sentence is this. Thetechnicians had performed a radiographictest of the weld but couldn’t achieve therequired test sensitivity so theyultrasonically tested it and found fourspots or areas in the weld, two of whichwere acceptable and two that wererejectable.

As with any specialized type of work,nondestructive testing has its ownvocabulary, much of which is oftenmisused even among the NDT workforceitself. We will look at some of the morecommon terms, try to clarify theirmeaning, and describe their proper use.

General Terminology

Among the words most commonly used(and misused) in the course of NDT workare discontinuity, flaw, defect and

indication. In many cases these terms areused interchangeably, further confusingthe issue as to what is meant or beingseen.Discontinuity. Discontinuities (sometimescalled flaws) are generally defined as an“Interruption in the physical structure orconfiguration of a test object.”1 whichmay or may not be detrimental to theuseful service of the part. Examples ofdiscontinuities include tears or cracks inthe material, unwanted inclusions(metallic or nonmetallic), and entrappedslag or porosity in a weld. If seriousenough to be considered detrimental tothe useful service of the part, thediscontinuity is called a defect.Defect. The term defect is defined as a“discontinuity whose size, shape,orientation or location (1) makes it

detrimental to the useful service of itshost object or (2) exceeds an accept/rejectcriterion of an applicable specification.”1

That is to say, some discontinuities areconsidered defects because they do notmeet the required acceptance criteriaeven though those discontinuities maynever be detrimental to the useful serviceof the part or cause the part to bedefective. The governing code orspecification will usually specify theacceptance criteria and the inspector isrequired to accept or reject a discontinuitybased on those requirements.Indication. An indication refers to aresponse or evidence of a responseresulting from a nondestructive test thatrequires further evaluation to determineits full significance (Fig. 1). The additionalevaluation is necessary because there canbe three types of indication:· relevant,· nonrelevant and· false.The inspector must be able to determinewhich type of indication is being seen.Relevant Indications. Relevant indicationsare those that are the result of an actualdiscontinuity. Examples of these would bethe discreet line of powder that disclosesa crack during an MT test or the vertical

FocusCommonMisunderstandings inNondestructive Testingby Charles J. Hellier

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Volume 7, Number 4 October 2008

Focus: Common Misunderstandings in Nondestructive Testing. . . . . . . 1

From the Editor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Tech Toon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Working Smarter: Avoiding Nicks, Dings and Scratches in FPI . . . . . . . . 5

Inbox . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Practitioner Profile: Samuel C. Bullard . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Crossword Challenge: Magnetic Testing . . . . . . . . . . . . . . . . . . . . . . . 10

A Publication of the American Society for Nondestructive Testing

CONTENTS

The NDT Technician A Quarter ly Publ icat ion for the NDT Pract it ioner

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Tech Toon

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FROM THE EDITOR

I f you’re a little confused about the exactdefinitions for some of the most commonterms used in nondestructive testing,

“Common Misunderstandings inNondestructive Testing” should help clearthings up. In addition to guidance on how touse NDT nomenclature accurately, the articlealso discusses some common misconceptions inthree primary NDT methods.

Gregory Robinson has documented anotherinnovation used in his NDT practice for TNT’s“Working Smarter” column. As a contributorto the feature, Gregory has a choice of a $50cash prize or $75 in credit for ASNTmerchandise. In addition, he is also entitled toone recertification credit.

Hollis Humphries, TNT EditorPO Box 28518, Columbus, Ohio 43228

(800) 222-2768 X206; fax (614) 274-6899<[email protected]>

trace on the screen of an ultrasonic testingmachine caused by entrapped slag orsidewall lack of fusion.Nonrelevant Indications. Nonrelevantindications are those that result from partgeometry, a physical condition or an actualdiscontinuity that is too small to beconsidered a defect.False Indication. A false indication is onethat shows up where no change ingeometry or discontinuity exists. Anexample of a false indication would be anindication caused by magnetic writing(slight magnetic field that can be left by awelding lead).

Method or Technique?

The terms method and technique are alsofrequently misused. For example, VT, PT,MT, RT, UT and ET are methods. For eachmethod there are specific techniques. Invisual testing, examples of techniqueswould be direct or remote viewing. Inpenetrant testing, techniques includevisible daylight, fluorescent,solvent-removable and water-washable.X-ray and gamma-ray are examples ofradiographic testing techniques. Inmagnetic particle testing, there arecontinuous and residual techniques, and inultrasonic testing, contact and immersiontechniques and so on.

Common Misunderstandings inUltrasonic Testing

Initial Pulse. Though sometimes referredto as the main bang or top surface signal,

Focus continued from page 1.

2 · 10/2008 · The NDT Technician

Figure 1. Decision tree for evaluatingrelevant indications.

Nondestructive Testing

Indication

Interpretation

Relevant

Evaluation

Accept Reject

Nonrelevant False

the initial pulse is defined by ASTM(E-1316) as “the response of the ultrasonicsystem display to the transmitter pulse.”2

The term initial pulse is consideredstandard and should be used to minimizeconfusion.Dead Zone and Near Zone. The deadzone and the near zone (field) are twototally different zones on the UT display.The dead zone describes that distanceunder the test surface where reflectorscannot effectively be resolved due to thepresence and width of the initial pulse.The near zone, on the other hand, is thatregion extending into the material fromthe entrant surface where ultrasonic wavefronts overlap, causing variations in soundintensity. There is a natural converging atthe end of the near zone which alsomarks the region of highest soundintensity with a standard flat transducer.The near zone is a function of wavelengthand transducer size, and can be calculatedusing the equation:

Straight Beam and Angle Beam. Anotherset of terms that need clarification arestraight beam and angle beam testing(Fig. 2). Straight beam testing refers to asound beam that hits the part surface at a90degree angle (perpendicular to thesurface). This sound beam is made up ofboth longitudinal or compression wavesand transverse or shear waves, but sinceboth waves travel at the same angle, onlyone signal is seen on the screen.

Angle beam testing uses a sound beamthat hits the part surface at an angleother than 90 degrees. Longitudinalwaves have a greater refracted angle (theangle of the sound beam in the part) thanshear waves, so until a certain angle isreached there are two sound beams inthe part. As the entry angle increases, thelongitudinal wave (L-wave) angle willincrease until it is no longer in the part,

leaving only the shear wave, which can beused for testing.

Common Misunderstandings inRadiographic Testing

The shim type penetrameter or imagequality indicator (IQI) is a flat rectangularplate or plaque used to determine thequality of a radiographic image (Fig.3).The penetrameter is made of the samematerial as the object being tested and isconfigured with a series of steps, holes orslots. The thickness of the penetrameter isusually 2 percent of weldment thickness(t); that being the ratio required by mostcodes. The series of holes in thepenetrameter have diameters that aremultiples of the thickness; the 1T holebeing equal to, the 2T hole being twiceand the 4T hole, four times the thicknessof the penetrameter.

Positioned adjacent to the point ofinspection, the penetrameter is exposedto the interrogating sourcesimultaneously with the test object. Howwell the outline of the plaque itself or theoutline of the specified hole can bediscerned in the resulting radiograph is

the means for judging the quality of theradiographic image.

Though penetrameters of this type ofhave been in use for more than 50 years,they continue to be a source ofcontroversy. When it comes to seeing theimage of the 2T hole in the radiograph,some radiographic film interpreters seemto have a good imagination. Some codesappropriately state that the image of theessential hole must be clearly discernable.That should be a firm determination onthe part of the interpreter and not asupposition. Unfortunately, there are stillsome interpreters who relate the holeimages with discontinuity size. While truethat the presence of these hole images onthe radiograph represent the quality levelof the radiographic technique, theyshould not be used as a comparison withactual discontinuities. For example, thepresence of a 0.5 mm (0.02 in.) hole imageon a radiograph, does not a guaranteethat all discontinuities of that size will bedetected. Penetrameter holes have sharpedges, are always rounded and positionedfavorably to the radiation beam toN

D=2

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10/2008 · The NDT Technician · 3

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Figure 3. Hole-type penetrameter orimage quality indicator:(a) penetrameter positioned adjacent toweld and (b) diagram showing holepositions and relative dimensions.

Steel Shim

Lead number 4Thole

1Thole

2Thole

T

(a)

(b)

Penetrameter

Steel shim

Weld

Figure 2. Ultrasonic testing wave forms. ••

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Particlemotion

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icle

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ion

Straight beam(compression wave)

Angle beam(transverse wave)

provide the best image. Discontinuities onthe other hand, are not always favorablyoriented and are not always round inshape with known dimensions. It must beremembered that the penetrameter isused primarily as a gage to confirm that asuitable technique has been used and thatthe film has been properly processed.

Common Misunderstandings inMagnetic Particle Testing

Of all the technique variables in magneticparticle testing, one that must becontrolled has to do with the use of dryparticles (Fig. 4). A commonmisunderstanding is that the particles willalways cling to a discontinuity regardlessof the amount of air pressure appliedduring excess particle removal. Evenmaterials with high retentivity will not

always hold particles in place when astrong column of air is directed towardsit. Because of these problems, MTexaminers in many countries apply a darkvisible suspension from a pressurized canto the test area which has been coatedwith a fast drying white lacquer. Thisprovides a much higher contrast makinginterpretation easier and eliminating theconcern about removal of the dryparticles from a discontinuity.

Another serious problem results whenusing dry particles and the magnetizingforce is not applied during removal of theexcess. Most codes require the removal ofexcess particles while the current is beingapplied (continuous technique) and whenthe magnetic field is at its strongest level.

Conclusion

As professionals, we should strive toimprove communication by using

terminology that is appropriate andtechnically correct. We all benefit bymaking the effort to overcome the habitsof misuse that have been ingrained inNDT technology for decades.

References

1. Nondestructive Testing Handbook,third edition: Vol. 10, UltrasonicTesting, Columbus, OH: AmericanSociety for Nondestructive Testing(1996): p 526.

2. Annual Book of ASTM Standards:Section 3, Metals Test Methods andAnalytical Procedures. Vol. 03.03,Nondestructive Testing. WestConshohocken, PA: ASTMInternational (2007): p 691.

Charles J. Hellier, III is the founder andformer president of Hellier. He is aregistered professional engineer and boardcertified forensic examiner. A member ofASNT since 1958 and a past president, Mr.Hellier has been the recipient of numerousawards including the Robert C. McMasterGold Medal Award and the Philip D.Johnson Honorary Member Award. He isalso a past president of the NondestructiveTesting Management Association andauthor of The Handbook of NondestructiveEvaluation. TNT

Figure 4. Application of magnetizingforce to test object during magneticparticle inspection: (a) magnetic particleapplication and (b) removal of excessparticles with forced air.

Application ofelectromagneticfield with yoke

Magneticparticles

WeldApplication offorced air

(a)

(b)

Weld

Application ofelectromagneticfield with yoke

Magneticparticle

applicator

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I n the aerospace industry, very tighttolerances and surface finishes may berequired. To avoid metal on metal

contact while performing liquid fluorescentpenetrant inspection, try placing expandedplastic mesh on metal surfaces. It isrelatively inexpensive and can be cut to sizewith scissors or wire cutters (Fig. 1). Weutilize the plastic mesh throughout oursystem, i.e. cleaning baskets, dip baskets,dwell and rinse stations, dryer anddeveloper tank as well, thus preventing

nicks, dings, and scratches that couldpossibly cause rejects or rework. It’s asimple task to replace the mesh if needed.However, the mesh that we have beenusing throughout our line for the last fiveyears has only needed replacement once.

It should be noted that mesh from thedryer and developer tank need to befrequently scanned under black light for

possible retained penetrant. If the meshfluoresces, rinse until clear or replace themesh to eliminate any contaminationissues. Caution should also be exercised toavoid over-rinsing of product.

Gregory P. RobinsonEaton Aerospace

ASNT NDT Level IIINorth Charleston, SC

<[email protected]> TNT

Working SmarterAvoiding Nicks, Dings andScratches in FPI

Figure 1. Expanded plastic mesh preventsmetal on metal contact in fluorescentpenetrant inspection system. Arrows showplacement in (a) dip basket, (b)dwellstation, (c) rinse tank, (d)dryer, and(e) developer tank. •

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(a)

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Plastic meshattached to sides

and bottom ofdip basket

Plastic meshcovering dwell

station rack

Placement inbottom of rinse

tank

Placed onbottom of

dryer

Placed onbottom of

developer tank

Topics submitted for “Working Smarter”earn $50 in cash or a $75 credit for ASNTmerchandise if published. For moreinformation, Contact the TNT Editor:

PO Box 28518, Columbus, OH 43228(800) 222-2768 X206;

(614) 274-6899 fax <[email protected]>

Q: I'm trying to find information regarding probability of defectdetection using NDT methods in the aerospace industry. HasASNT ever published an article about this subject? G.B.,Cudahy, California.

A: Probability of detection (POD) uses statistics to predict thereliability of a method in a specific application. The topic ofPOD appears in three NDT Handbook volumes.· NDT Handbook, third edition: Vol. 2, Liquid Penetrant

Testing. Ch. 9, p 275-285.· NDT Handbook, third edition: Vol. 5, Electromagnetic

Testing, p 260-261, 486-487.· NDT Handbook, third edition: Vol. 7, Ultrasonic Testing,

p 530-534.Entries in the PT and UT volumes are relevant to aerospace.You may also find the “Complete Materials Evaluation Index”helpful. It lists every article published in Materials Evaluationfrom 1947 through 2007. A search for your topic turns up anumber of articles. Click the “Publications” link at<www.asnt.org>, pull down to Materials Evaluation and lookfor the download text link.

Reader response to yoke dragging query (Vol. 7, No. 1).

I was reading the “Q&A Inbox” on yokes in the 01/2008 issue.If a yoke operates on 60 Hz AC, the skin depth of field maycause it to be insufficient for demagnetizing a plate above acertain thickness. Further, though dragging yokes downoilfield pipe is a common practice, this action wears down thecorners of the yoke legs and, in some cases, results in a yokethat cannot then lift the 10 lb test mass. RKS, Houston, Texas.

Q: Can you direct me in how the Standards DevelopmentCommittee (SDC) found/established equivalent eyeexaminations? Refer to Draft BSR/ASNT CP-106:200X. para.7.2.3. M.D. Cheney, Kansas

A: Initially drafted in early 2004 and based on ISO 9712:1999,“CP-106: Nondestructive Testing Qualification andCertification of Personnel” had the term "or equivalent" inthe near vision acuity section. Because other ASNTcertification documents use the same term, ASNT’s TechnicalServices Department received numerous calls asking forclarification for the Jaeger number equivalents. As a result,the SDC, ASNT’s consensus committee for developingAmerican National Standards, agreed that a note clarifyingequivalents could be added. The following organizationswere consulted in drafting the text.· Snellen values and the Times Roman points: The

American Optometric Association, the National OptometricAssociation, the Ohio State University Department ofOptometry and several Columbus, Ohio optometrists.

· OrthoRater values: Reichert, Inc.· Titmus values: SperianOn points two and three above, both companies gave thevalues listed in “CP-106”. Regarding point one above, mostresponses referenced Clinical Refraction, by Irvin Borish. Dr.Timothy Wingert, Acting Director of the Clinical Care Groupof the American Optometric Association, specified the thirdedition, Vol. 1, (1975): pp 391 and 418. Noting the book wasnow out of print, Dr. Wingert also stated the information wasstill valid and summarized the comparison with the followingtable:

Jaeger 1 2 3Times Roman Point 3.5 4.5 6.0

Snellen 20/22 20/27 20/40

It should be noted that most optometrists record values ineven numbers, 20/20 is usually accepted for J-1 and 20/25 forJ-2. However, a company should describe whateverconvention they use in their written practice. If you researchthis subject yourself, you may notice that some internationalNDT certification documents such as ISO 9712, EN 473 and theCanadian CAN/CGSB 48.9712 all list near visual acuityrequirement as Jaeger J-1, Times Roman N4.5 or equivalent.But, according to the table shown in Clinical Refraction, N4.5is equivalent to Jaeger J-2, not J-1, so the SDC chose to keepTimes Roman 3.5 as the equivalent listed in “CP-106.”

Finally, when using a reading card, note that the distance atwhich the card is to be read changes with the font size. Usingthe card at other distances will lead to a false eye test. JamesW. Houf, Senior Manager, ASNT Technical Services Dept.

E-mail, phone or fax your questions for the “Inbox” to theEditor: <[email protected]>, phone (800) 222-2768 X206,fax (614) 274-6899. TNT


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The Naval Aviation Technical Data and Engineering ServiceCommand (NATEC) provides oversight for the manufacture anddistribution of aviation parts, maintains related technical data,provides manuals for maintenance and repair of aircraft andrelated systems and trains sailors to work on those aircraft andsystems. NATEC personnel also step in with technical assistancefor Navy and Marine Corps technicians when needed.

You work for NATEC. Are you military personnel?

I’m not uniformed personnel. I’m a Department of Defense(DOD) employee. But, I do have a twenty-year U.S. Navycareer in front of this 15-year career as a civil servant.

How did you get started in NDT?

Early in my Navy career, I was stationed at Pax River (U.S.Naval Air Station Patuxent River, Maryland). The paint andfiberglass shop where I worked also housed the NDI lab. I did

some penetrant and mag grunt workfor the NDI guys and I found itinteresting. After leaving Pax River, Iwent to welding school and did a tourdown in Gitmo (Guantánamo BayNaval Base). Some of my work thereincluded cleaning and prepping partsfor NDI. I asked the NDI techniciansabout what they were doing and howit worked. Putting welding and NDItogether looked like a good idea and Idecided to get into the NDI field aftercompleting my welding tenure. MyNavy NDI training began in 1978 and I

maintained both welding and NDI certifications untilretirement from the military in 1988. Then I went to work forthe organization that would eventually become NATEC.

How many NDI personnel are there?

There’s the surface or shipboard side of the Navy and thenthere’s the air side that deals with airplanes. On the air sideof the house, we are just 325 strong.

What are the Naval NDI certification levels?

Our primary certifying document is NAMP (Naval AviationMaintenance Program). As far as education and on-the-jobtraining are concerned, NAMP references NAS 410 (NAS 410:Certification & Qualification of Nondestructive Test Personnel)which kind of mirrors SNT-TC-1A. That said, because of theway that we do our inspections, our depot artisans are ourLevel III engineers. They write and deliver the procedures withall of the necessary parameters for completing inspections tothe fleet. When our NDI technicians come out of NDI school,

they have completed 13 weeks of compressed and veryintense NDI training in ET, MT, PT, UT, and RT. When theygraduate, they are considered Level II NDI technicians.

Does Navy NDI training include digital technologies?

Not at this time. There are proposals in the works for trainingand equipment upgrades that will facilitate the transition ofwet film radiographers to digital radiography. Phased arraytechnology is also under consideration down the road. Muchof our current fleet is comprised of older aircraft that don’tuse composites. With the acquisition of new aircraft, such asthe F-35 Joint Strength Fighter and the EA-18G Growler, thatwill change. There’s extensive use of composites in theirdesign and in that of other new aircraft. Newer inspectiontechnologies will have to be implemented to inspect them.

Can you describe the work you do?

I wear multiple hats in multiple arenas. My primary focus isthe fleet Navy Marine Corps technician. Once technicianscomplete the NDI course at Naval Air Station Pensacola, theyare required by our governing documents to recertify everythree years. I’m one of the folks authorized to provide theinterim recertification process. I do the training, the recerts,the testing — anything that’s required for the recertificationprocess. Another of my hats is as an interface between thedepots and the fleet sailor. I’m closer to the fleet sailor thanthe Level III engineers. When a new or particularly difficulttype of inspection or procedure has been developed, I’mcalled on to provide a little more hands on for the fleetpersonnel before they go out to implement it. Anotherportion of my job is as a technical expert for newtechnologies. For example, let’s say we have to replace anultrasonic instrument that is legacy or that needs to bereplaced. I help a division of Naval Air Systems Command(NAVAIR) to look for emerging technologies to replace it. Wespend time working with the unit to make sure it meets fleetinspection requirements. Once a system has been selected anda contract awarded, I help develop training to introduce it tothe fleet. I guess you could say I’m like a smoke jumper. I finda hot spot and drop in.

What is the most rewarding aspect of your work?

I feel I’m a kind of spokesperson for the fleet — sailor andmarine. Our NDI technicians are very dedicated and they wantto excel in the NDI arena. I’m able to reach out and get theanswers needed to resolve their issues. For instance, we’venoted in the last few years that we may have been takingtechnicians straight from the schoolhouse and putting theminto deployed areas too quickly — possibly without givingthem all the tools needed to get onsite and inspect all theplatforms in their battle group. Noting that, we’ve made

PRACTITIONERPROFILESamuel C. Bullard


some changes to our documentation to provide them with anadditional 3 months of on-the-job training at specific sitesafter completing NDI training. They’ll have a broader andmore comfortable range of experience to prepare them forthe platforms and aircraft they will eventually be testing attheir final duty stations.

Is much of your time spent traveling?

For the last four to five years, I’ve been on the road betterthan 320 days a year.

Where does the Navy NDI technician work?

That’s specified in three levels. There’s the operational orsquadron level where the planes are prepped for flight. Ifsomething breaks, then they pull it off and send it to theintermediate level where any repairs or testing that’s requiredis done. If the repairs can’t be done at the intermediate level,it goes to the depot level.

Does Naval NDI experience and training transfer readily intothe private sector?

NDI technicians often ask me that. What kind of jobs can theyfind in the civilian sector? I work regularly with inspectionequipment manufacturers, OEMs — key folks in the industry.I’ve been able to recommend 8 or 9 NDI personnel forpositions in private industry. The companies that hired themon liked what they saw. It’s still up to the company that hires

them to validate what the technician brings to the table inthe way of experience and certification. NAVAIR recognizesthem as capable to perform Level II duties, but privateindustry has extensive requirements for experience in eachNDI method that is not currently tracked through Navymandated records. One of my personal crusades is to teachthe fleet technicians the importance of documenting all oftheir on-the-job training and experience. If they do that andit meets necessary requirements, I can provide them with adocument that says they are certified as a Level II according toNAS 410. That way, when they walk away from the uniform,they have credentials stating they are Level II technicians.

What advice can you give to those considering NDT careers?

I get asked that a lot. If you want to pursue this field afterleaving the military, I strongly recommend getting into anengineering or materials science program, perhaps as distancelearning through various colleges or universities. Basicmetallurgy courses like those available through ASMInternational are good too. It’s important to understand thematerials you work with and the principles of the inspectionequipment you use. That’s why in the Navy and Marine Corps,you have to have a metal smith background to get into NDIschool. You can’t be an avionics technician or an enginemechanic. You have to be a metal smith equipped to dealwith metal and composite components.

Sam Bullard can be reached at (360) 929-2421; email<[email protected]>. TNT


The Smartest and Smallest Investment YouEver Make in Your Career could be the

$75 You Spend to Join ASNT.

• Building professional relationships

• Accessing information and resources

• Increasing career opportunities

• Networking with peers

ASNT members get involved with local sections, serve on international committees, present and publish papers, attend conferences, earn certification credentials, and receive recognition. If NDT matters in your career, then ASNT membership is a wise investment to make.The entry point starts here www.asnt.org or phone ASNT at

(614) 274-6003, (800) 222-2768 for US and Canada

Because this global Society is your resource for:• Developing leadership skills

• Sharing experience and expertise

• Gaining competitive advantages

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Volume 8NDT Handbook

MagneticTesting

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Across1. Ferromagnetic core surrounded by a coil of wire that

temporarily becomes a magnet when an electric current flowsthrough the wire.

6. Demagnetization process in decreasing steps where thepersistence of each polarity in turn is overcome by itsopposing field.

8. Ability of material to transmit electric current. Inverselyrelated to resistivity

10. Magnetic field intensity is governed by the density of theselines, which form closed loops that do not cross.

11. Reduction of residual magnetism to an acceptable level.14. Break, fissure or rupture, sometimes vee shaped in cross

section and relatively narrow. Propagating discontinuitycaused by fatigue, corrosion or stresses.

15. Electric current that flows continuously in one directionthrough a conductor.

18. Magnetization remaining in a ferromagnetic material aftermagnetizing force is gone.

19. Factors in test based on mental and physical condition of theinspector, training, experience level and the physicalconditions under which the inspector must work.

21. Force, magnetic field intensity or potential difference —measured in air or vacuum in ampere turns.

22. At surface of cylinder and perpendicular to axis.23. Magnet that retains magnetization after a coercive field has

been removed.24. Dimensionless property describing a material’s response to an

external magnetic field.

Down2. Transmission of electric current through material. Inverse of

electrical resistance.3. Percentage of magnetic flux from a primary circuit that links

a secondary circuit; effectiveness of a coil in inducing eddycurrents in the test object.

4. Lagging of a ferromagnetic test object’s magnetization underthe influence of a changing external magnetic field intensity.

5. Encircling solenoid carrying a current that imparts alongitudinal magnetic field in ferromagnetic components.

7. Active or residual magnetic field oriented along the length oraxis of the part.

9. Parallel to an object’s surface.12. Measure of the opposition of a circuit to a change in current.13. Ratio of magnetic induction over magnetizing force.16. Path followed by magnetic flux lines that may include the

test object, any air gaps and an electromagnetic orpermanent magnet yoke.

17. Material’s ability to maintain remanent magnetism in theabsence of a coercive field.

20. Author of fundamental equations of electromagnetic fieldtheory.

Across1.electromagnet6.downcycle8.conductivity

10.flux11.demagnetization14.crack

15.direct18.residual19.human21.magnetomotive22.tangential23.permanent24.susceptibility

Down2.conductance3.coupling4.hysteresis5.coil7.longitudinal9.tangential

12.inductance13.permeability16.circuit17.retentivity20.Maxwell

Answers

Clues for this “Crossword Challenge” are based on glossary entries taken from the Magnetic Testing volume of the NDTHandbook series. To be published this Fall, Volume 8, Magnetic Testing, covers the magnetic particle testing method in detail.Much of that information also pertains to magnetic flux leakage testing, which has been administered by ASNT as a techniqueof the electromagnetic testing method. The terms in this crossword pertain to both tests.

Volume 7, Number 4 October 2008

Publisher: Wayne HollidayPublications Manager: Tim Jones

Editor: Hollis HumphriesTechnical Editor: Ricky L. Morgan

Review Board: William W. Briody, Bruce G. Crouse,Ed E. Edgerton, Anthony J. Gatti Sr., Jesse M. Granillo,Edward E. Hall, Richard A. Harrison, James W. Houf,Jocelyn Langlois, Eddy Messmer, Raymond G. Morasse,Ronald T. Nisbet, Angela Swedlund

The NDT Technician: A QuarterlyPublication for the NDT Practitioner(ISSN 1537-5919) is publishedquarterly by the American Society forNondestructive Testing, Inc. The TNTmission is to provide informationvaluable to NDT practitioners and aplatform for discussion of issuesrelevant to their profession. ASNT exists to create a safer world by promoting the professionand technologies of nondestructive testing.

Copyright © 2008 by the American Society for Nondestructive Testing, Inc.ASNT is not responsible for the authenticity or accuracy of informationherein. Published opinions and statements do not necessarily reflect theopinion of ASNT. Products or services that are advertised or mentioned donot carry the endorsement or recommendation of ASNT.

IRRSP, Materials Evaluation, NDT Handbook, Nondestructive TestingHandbook, The NDT Technician and www.asnt.org are trademarks of TheAmerican Society for Nondestructive Testing, Inc. ACCP, ASNT, Level III StudyGuide, Research in Nondestructive Evaluation and RNDE are registeredtrademarks of the American Society for Nondestructive Testing, Inc.

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