DOCUMENT RESUME SE 013 878 Magnetic Particle Testing, RQA .
DOCUMENT RESUMEED 086 444TITLEINSTITUTIONREPORT NOPUB DATENOTEEDRS PRICEDESCRIPTORSSE 013 878Magnetic Particle Testing, RQA/P11-5330.16.General Dynamics, San Diego, Calif. Convair Div.;National Aeronautics and Space Administration,Huntsville, Ala. George C. Marshall Space FlightCenter.NAS8-201851 Jan 67142p.MF- 0.65 HC- 6.58Aerospace Technology; *Finishing; *InstructionalMaterials; *Magnets; Post Secondary Education;Quality Control; Science Education; TechnicalEducation; *TechnologyABSTRACTAs one in the series of classroom training handbooks,prepared by the U.S. space program, instructional material ispresented in this volume concerning familiarization and orientationon magnetic particle testing. The subject is divided under thefollowing headings: Introduction, Principles of Magnetic ParticleTesting, Magnetic Particle Test Equipment, Mediums and TheirPreparation, Magnetic Particle Applications, Classification ofDiscontinuities, and Comparison and Selection of NondestructiveTesting Processes. High product reliability and quality in metalprocessirg are the main concerns through the volume. The Material isdesigned for use in the classroom and practical exercise portions,and successful completion of the corresponding programmed instructionhandbook is the prerequisite for receiving classroom training.Included are illustrations for explanation purposes and tables ofmagnetic characteristics. (CC)
JanuaryQUALITY ANDI ,U S DEPARTMENT OF HEALTH.EDUCATION 8 WELFARENATIONAL INSTITUTE OFEDUCATIONRELIABILITY ASSURANCELABORATORYTHIS DOCUMENT HAS fIEFN REPROOUCED EXACTLY AS RECEIVED FROMTHE PERSON OR ORGANIZATION ORIGINATiNG IT POINTS OF VIEW ON OPINIONSSTATED DO NOT NECESSARILY REPRESENT OFFICIAL NATIONAL INSTITUTE OFEDUCATION POSITION OR POL ICYMAGNETIC PARTICLE TESTINGRQA/M1 - 5330 .16sameAlARRIALLNOWINVILM ALABAMANATIONAL AERONAUTICS AND SPACE ADMINISTRATIONMSFt - Form 1262 (September 1961)1967
5330. 16PREFACEClassroom Training Handbook - Magnetic Pakic le Testing (5330. 16) is one of aseries of training handbooks designed for use in the classroom and practical exerciseportions of Nondestructive Testing. It is intended that this handbook be used in theinstruction of those persons who have successfully completed Programmed InstructionHandbook - Magnetic Particle Testing (5330. 11).Although formal classroom training ii -not scheduled at the present time, this handbook contains material that is beneficial to personnel engaged in Nondestructive Testing.NASA's programs involve tightly scheduled procurement of only small quantities ofspace vehicles and ground support equipment, requiring the extreme in reliability forthe first as well as later models. The failure of one article could result in missionfailure. This requirement for complete reliability necessitates a thoroughly disciplined approach to Nondestructive Testing.,A major share of the responsibility for assuring such high levels of reliability lieswith NASA, other Government agencies, and contractor Nondestructive Testing personnel. These are the people who conduct or monitor the tests that ultimately confirmor reject each piece of hardware before it is committed to its mission. There is noroom for error no chance for reexamination. The decision must be rightunquestionablythe first time.General technical questions concerning this publication should be referred to theGeorge C. Marshall Space Flight Center, Quality and Reliability Assurance Laboratory, Huntsville, Alabama 35812.The recipient of this handbook is encouraged to submit recommendations for updatingand comments for correction of errors in this initial compilation to George C.Marshall Space Flight Center, Quality and Reliability Assurance Laboratory(R-QUAL-OT), Huntsville, Alabama 35812.1
5330.16ACKNOWLEDGMENTSThis handbook was prepared by the Convair Division of General Dynamics Corporationunder NASA Contract NAS8-20185. Assistance in the form of process data, technicalreviews, and technical advice was provided by a great many companies and individuals.The following listing is an attempt to acknowledge this assistance and to express ourgratitude for the high degree of interest exhibited by the firms, their representatives,and other individuals who, in many cases, gave considerable time and effort to theproject.Aerojet-General Corp.; Automation Industries, Inc., Sperry Products Division;AVCO Corporation; The Boeing Company; Douglas Aircraft Co., Inc.; Grumman Aircraft; Lockheed Aircraft Co.; Magnaflux Corp.; The Martin Co. (Denver); McDonnellAircraft Corp.; North American Aviation, Inc.; Rohr Corporation; Southwest ResearchInstitute; St. Louis Testing Laboratories, Inc.; Uresco, Inc.; X-Ray Products Corp.ii
5330.16CLASSROOM TRAINING HANDBOOKMAGNETIC PARTICLE TESTINGCHAPTER 1INTRODUCTIONCHAPTER 2PRINCIPLES OF MAGNETIC PARTICLE TESTINGCHAPTER 3MAGNETIC PARTICLE TEST EQUIPMENTCHAPTER 4MEDIUMS AND THEIR PREPARATIONCHAPTER 5MAGNETIC PARTICLE APPLICATIONSCHAPTER 6CLASSIFICATION OF DISCONTINUITIESCHAPTER 7COMPARISON AND SELECTION OF NDT PROCESSES
5330.16CHAPTER 1: INTRODUCTIONTABLE OF ERALPURPOSEDESCRIPTION OF CONTENT1. Arrangement2. LocatorsINDUSTRIAL APPLICATIONS OF MAGNETIC PARTICLE TESTINGTESTING PHILOSOPHYPERSONNELTESTING CRITERIATEST PROCEDURESTEST OBJECTIVEPage1-31-31-31-31-31-41-41-41-41-41-5
5330.16CHAPTER 1:100INTRODUCTIONGENERALThe complexity and expense of space programs dictate fabrication and testing procedures that insure reliability of space vehicles and associated ground support equipment. Nondestructive testing (testing without destroying) provides many of theseprocedures. Of the number of nondestructive test procedures available, the magneticparticle tests, with which this handbook is concerned, is one of the oldest nondestructive test methods and a proven tool.s101PURPOSEThe purpose of this handbook is to provide the fundamental knowledge of magneticparticle testing required by quality assurance and tes', personnel to enable them to:ascertain that the proper test technique, or combination of techniques, is used toassure the quality of the finished product; interpret, evaluate, and make a sound decision as to the results of test; and recognize .those areas of doubtful test results thatrequire either retest or assistance in interpretation and evaluation.1021.DESCRIPTION OF CONTENTSARRANGEMENTThe material contained in this handbook is presented in a logical sequence and consistsof:2.a.Chapter 1:Introduction and testing philosophyb.ChapterPrinciples of magnetic particle testing, describing theory,fields, current and demagnetizationc.Chapter3:Magnetic particle test equipment, equipment and accessoriesconsideration, and their operationd.Chapter 4:Mediums, their characteristics, application, and preparatione.Chapter5:Magnetic particle applications, classification of magnetizationmethods, surface preparation, and demagnetization requirementf.Chapter6:Magnetic particle indications, their characteristics, classification by origin, and preservation0.Chapter7:Comparison and selection of NDT processesLOCATORSThe first page ,3f each chapter consists of a table of contents for the chapter. Majorparagraphs, figures, and tables are listed in each table of contents.1-3
5330.16103INDUSTRIAL APPLICATIONS OF MAGNETIC PARTICLE TESTINGBecause magnetization of certain metals is possible, a medium having magnetic attraction is applied to the surface of the test object Ater or during induction of a magneticfield, thereby detecting certain discontinuities which are present in the material. Sincemagnetic particle testing is capable of revealing discontinuities (variations in materialcomposition) economically, it is one of the most used nondestructive test methods.104TESTING PHILOSOPHYThe basic reason for use-of nondestructive testing is to assure maximum reliabilityof space and associated ground supporting hardware, fabricated of many materials. Toaccomplish such reliability, standards have been set and test results must meet theserigid NASA standards.105PERSONNELIt is imperative that personnel responsible for magnetic particle testing be trained andhighly qualified with a technical understanding of the test equipment, the item undertest (specimen), and the test proceddres. Quality assurance personnel must beequally qualified. To make optimum use of magnetic particle testing, personnel conducting tests must continually keep abreast of new developments. There is no substitute for knowledge.106TESTING CRITERIAWhen required by appropriate documentation, .every vehicle and support articlemust be tested using applicable Nondestructive Testing techniques. The criteria is part of a building block test philosophy which dictates that each itemmust be tested individually before it is required to perform in sub-assemblieswhich are in turn tested individually before they are required to perform inassemblies. Using this approach, unsatisfactory and faulty articles are discovered at the earliest possible time, resulting in higher system reliabilityand reduced cost.107TEST PROCEDURESApproved procedures for magnetic particle testing are formulated from analysis of thetest specimen, review of past history, experience on like or similar specimens, andinformation available concerning similar specimen discontinuities. It is the responsibility of personnel conducting or checking test to insure that test procedures areadequately performed, and that the test objective is accomplished. Procedures foundincorrect or inadequate must be brought to the attention of responsible supervisiOnfor correction and incorporation into revised procedures.1-4
5330.16108TEST OBJECTIVEThe objective of magnetic particle testing is to insure product reliability by providing a means of:1.a.Obtaining a visual image of an indication related to a discontinuity in or onthe surface of a material.b.Disclosing the nature of discontinuities without impairing the material.c.Separating acceptable and unacceptable material in accordance with predetermined standards.2. No test is successfully completed until an evaluation of the test results is made.Evaluation of test procedures and results requires understanding of the test objective.1-5
5330.16CHAPTER 2:PRINCIPLES OF MAGNETIC PARTICLE TESTINGTABLE OF CONTENTSParagraph2002011GENERALTHEORY OF MAGNETISM1. General2. Magnetic Poles3. Magnetic Field4. Lines of Force5. Longitudinal Magnetization6. Horseshoe MagnetVector FieldConsequent Poles9. Distorted Fields10. Leakage Fields7.g.202203MAGNETIC MATERIALSELECTRICALLY INDUCED MAGNETIC FIELDS1. General2.Right-Hand Rule3.4.Coil5.Magnetic FluxFlux DensityPermeabilityReluctanceResidual MagnetismRetentivity10. Coercive Force6.7.8.9.204HYSTERESIS. LOOP1.2.3.205GeneralVirgin CurveResidual MagnetismCoercive ForceReversed Polarity4.5.6. Curve CharacteristicsCIRCULAR. AND LONGITUDINAL MAGNETIZATION1. GeneraLMagnetization3. Longitudinal MagnetizationPage2-52-52-52 -52-62 -62-72-72-72-82-82-92-102-102-102 -112 -112-112 -122-122-122-122 62-1
5330.16TABLE OF CONTENTS (CONT)Paragraph200PageFIELD DISTRIBUTION IN MAGNETIC ANDNONMAGNETIC CONDUCTOR S1.2.3.4.5.GeneralSolid Nonmagnetic ConductorSolid Magnetic ConductorHollow Nonmagnetic ConductorHollow Magnetic Conductor(3.Alternating Current Field DistributionDirect Current Residual FieldsAlternating Current Field Distributio,-7.8.207MAGNETIZING CURRENT CHARACT1AISTICS2 -172 -172 -192 -192 -219 912 -2293.4Penetration Characteristics2-242.CURRENT REQUIREMENTS1.2.342099 -1 {2GeneralAlternating CurrentHalf-Wave Rectifie.1 Current.1.2082 -16GeneralCircular MagnetizationLongitudinal MagnetizationProd MagnetizationTHEORY OF DEMAGNETIZATION1.2.3.4.Figure 2-1Figure 2-2Figure 2-3Figure 2-4Figure 2-5Figure 2-6Figure 2-7Figure 2-8Figure 2-9Figure 2-10Figure 2 -11Figure 2-12Figure 2-132 -292 -239 9,12 -242 -952-962-282-28GeneralAlternating Current DemagnetizationDirect Current DemagnetizationEfficiency of Demagnetization2 -282 -28Orientation of MoleculesAttraction and RepulsionMagnetic Field Surrounding Bar MagnetPoles in Straight Bar, Horseshoe, and Broken MagnetVector Field DiagramConsequent PolesCut and Fused Bar-Magnet Illustrating Opposite PolarityLeakage Fields Around DiscontinuitiesRight-Hand RuleLongitudinal Field Around CoilThe Hysteresis Curve2-5,,Hysteresis Loop CharacteristicsCircular Magnetization by Direct andIndirect Current 2-142-152-2
5330.16TABLE OF CONTENTS (CONT)ParagraphFigure 2-14Figure 2-15Figure 2-16Figure 2-17PageLongitudinal MagnetizationField Distribution In and Around a Nonmagnetic ConductorField Distribution In and Around a Solid Magnetic ConductorField Distribution In and Around a Hollow NonMagneticConductorField Distribution In and Around a Hollow Magnetic Conductor .Field Distribution In and Around a Hollow Magnetic CylinderWith Central ConductorField Distribution In and Around Solid Magnetic Conductor2-162-172-182-20Figure 2-26Figure 2-27Carrying Alternating CurrentField Distribution In and Around a Hollow Magnetic ConductorCarrying Alternating CurrentSingle Phase Alternating Current Wave-FormRectification of Alternating Current to Half-WaveDirect CurrentThreshold Sensitivities of Various MetalsCircular Magnetization of Typical Specimens Using Head-Shotor Central ConductorDemagnetization Flux-Curve Projected from Hysteresis CurveDemagnetization CoilTable 2-1Table 2-2Magnetic Characteristics of, MaterialsMagnetizing Current for Sdlid and Tubular ArticlesFigure 2-18Figure 2-19Figure 2-20Figure 2-21Figure 2-22Figure 2:-23Figure 2-24Figure 2-254,2-3
5330.16CHAPTER 2:200PRINCIPLES OF MAGNETIC PARTICLE TESTINGGENERALMagnetic particle testing is a relatively easy and simple test method that can be appliedto finished articles, billets, hot rolled bars, and forgings. It can also be used tocheck processing operations, such as heat treat, machining, and grinding. Magneticparticle testing consists of magnetization of the article, application of a magneticmedium, and interpretation of the magnetic medium patterns.2011.THEORY OF MAGNETISMGENERALAn object is magnetized when part or all of its molecules have their north and southpoles oriented. (See Figure 2-1.)sicilVsNepIssoNeoQNeSeNeSeNeSeNeSe e&ebG01)G00eeeeeeeee o eRANDOM ORIENTATION OF MOLECULESALIGNED MOLECULESFigure 2-1. Orientation of Molecules2.MAGNETIC POLESA body which possesses the ability to attract iron pieces is called a magnet. Magnetsmay be permanent, retaining their magnetism more or less permanently; or temporary, retaining their magnetism only as long as a magnetizing force is being applied.The ability of the magnet to attract or repel is not uniform over its surface, but isconcentrated at local areas called poles. Each magnet has at least two opposite poles,which are attracted by the earth's magnetic poles; hence, the poles are respectivelycalled the north and south poles. The attraction and repulsion of poles are illustratedin Figure 2-2.2-5
5330.16NREPELNATTRACTNNFigure 2-2. Attraction and Repulsion3.MAGNETIC FIELDA magnetic field exists within and around a permanent magnet or around a conductorcarrying an electric current. The magnetic field surrounding a permanent bar magnet has polarity, but the magnetic field surrounding a conductor does not. As anexample, the earth itself can be thought of as a bar magnet because of its two poles.Quite frequently the field surrounding the earth strongly magnetizes large ferromagnetic objects that lie aligned with the earth's poles for periods of time.4.LINES OF FORCEThe concept of lines of force is useful for describing a magnetic field. As illustratedin Figure 2-3, a bar magnet is covered with a sheet of paper and iron filings are- - .,. .N. \\\ il/ / /i\\ \ \\ N\\\\N,/ 4, z//J /1///////!///I\ \,,,. \\\\\.\\\\,,\iiii,///, y,////:/z'-,/,':z'1 /1I''/2-----.:---.;-:\,a\I\i'.\\IiiiiiVii,i.t1,-!% --1*v .%1--.f.7 - ----- ------------: ------w-'----'------. -"--fromIrrv\\: -- --//- ,,,-;,/,/,7- ---- -%.,I, I,---,---,.,,,/filifi\li // '//7 1/II\\.,., ,\\\\\\///,/,11\II\\Figure 2-3. Magnetic Field Surrounding Bar Magnet2-6-----1.4 ;--------:--- ----\\ \\ \
5330.16scattered over the paper. The Lines of force arrange themselves in characteristicpatterns. They never cross; they seek the path of least resistance; they are mostdenSely packed at the poles of the magnet; and they flow from north to south outsidethe magnet, but from south to north within the magnet.5.LONGITUDINAL MAGNETIZATIONA permanent bar magnet is the Aimplest example of longitudinal magnetization. Sincethe direction of the magnetic flux is axial, it usually has two poles. Longitudinalmagnetization is said to exist in an object when the flux lines traverse in a directionessentially parallel to one of its axes.G.HORSESHOE MAGNETIf a straight bar magnet is bent, it becomes a horseshoe magnet. When the magnet isbent further to make a complete loop and the ends are fused together, the polesdisappear; i, e. a closed magnetic circuit is formed. If the circle is cut, eitherpartially or all the way through, the poles reappear as shown in Figure 2-4.WILL LIFT OR DRAW A NAILTO THE MAGNETFIELD IS ENTIRELYWITHIN, THUS NOEXTERNAL FORCELEAKAGE FIELD WILLATTRACT MAGNETICPARTICLESFigure 2-4. Poles in Straight Bar, Horseshoe, and Broken Magnet7,VECTOR FIELDTwo magnetizing fr.-ces may be imposed simultaneously upon the area of a magnetizable object. When this occurs, the two fields do not exist independently; that is, theobject is not magnetized in two directions at once, but a vector field is formed whichis the esultant in direction and strength of the two imposed fields. This phenomenonis illustrated in Figure 2-5, where Fa is the first magnetizing force, Fb, the secondmagnetizing force, and Fab equals the resultant magnetizing force.2-7
5330.16Figure 2-5. Vector Field Diagram8.CONSEQUENT POLESConsequent poles exist when more than two poles are present simultaneously in amagnetized object. For example, there may be two north poles and one south pole.Figure 2-6 illustrates a series of poles along the length of an article. Herein lies theprinciple of magnetic particle testing, since under test particle build-up occurs ateach of the poles.9.DISTORTED FIELDWhile it is normal to conceive of magnetic fields as being either circular or longitudinal in many cases the actual field is a combination of the two. This is known as adistorted field. Distorted fields may be produced intentionally, or they may beFigure 2-6. Consequent Poles2-8
5330. 16unavoidable. When produced intentionally, they are of great value in accomplishingthe desired result, which is to produce a magnetic field at an angle to the direction ofa possible discontinuity. Distorted fields are often helpful and, in some instancesessential to the success of certain magnetic particle test procedures.10.LEAKAGE FIELDThe magnetic field around a bar magnet is shown in Figure 2-2. If a bar magnet isbroken in two, making two shorter bars, each immediately becomes a separate barmagnet with a north and a south pole. If the two bars are again fused together, withopposite magnetic poles adjacent, the poles will not completely disappear. A smallconcentrated leakage field will remain in the fusion area. (See Figure 2-7.) Similarly, if the bar is cut only Partially through two opposite poles will appear, and aleakage field will exist in the area of the cut. From Figure 2-8 it can be seen thatNSSNSSNSNNFigure 2-7. Cut and Fused Bar-magnet Illustrating Opposite PolaritySLOTMAGNETIC PARTICLEBUILD-UPFigure 2-8, Leakage Fields Around Discontinuities2- 9
5330.16leakage fields are actually magnetic lines of force that leave the bar and pass throughthe air from one pole to the other of opposite polarity Since the new opposite poleswere created by the interruption of the paths
on magnetic particle testing. The subject is divided under the following headings: Introduction, Principles of Magnetic Particle Testing, Magnetic Particle Test Equipment, Mediums and Their Preparation, Magnetic Particle Applications, Classification of Discontinuities, and Comparison and Selection of Nondestructive Testing Processes.
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