ASTM_E_1444_E1444M-16.pdf

E1444/E1444M-16e1field.The pie gauge or flexible laminated strips shall not bemasking of relevant indications by nonrelevant accumulationsused to determine adequate field strength.Exceptions necessi-of magnetic particles.Adequate magnetic field strength may betated by part geometry,size,or other factors require specificdetermined by one or a combination of the following methods:approval of the Cognizant Engineering Organization.6.3.1.1 In unidirectional,or multidirectional magnetizing6.2.6 Multidirectional Magnetization-Multidirectionalapplications,by examining parts having known or artificialmagnetization may be used to fulfill the requirement fordiscontinuities of the type,size,and location specified in themagnetization in two or more directions if it is demonstratedacceptance requirements or by using the notched shims asthat it is effective in all areas,which require examination asdefined in Annex Al;practical.Test parts in accordance with 6.3.1.1 or shims6.3.1.2 In unidirectional magnetizing applications only,bymanufactured to the requirements of AS 5371,or as otherwiseusing a Hall Effect probe gaussmeter capable of measuring theapproved by the Cognizant Engineering Organization,shall bepeak values of the tangential field as described in Annex A5.used to verify field direction,strength,and balance in multidi-Tangential-field strengths shall have a minimum value of 30rectional magnetization.Balancing of the combined magneticGauss(30 x 10 Tesla T)when measured at the part surfacefield is critical and an adequate balance must be visuallyusing a Hall Effect probe gaussmeter as described in Annexdemonstrated to be effective in all areas,which requireA5.The maximum Gauss value derived is limited by theexamination.The particle application must be timed so that therestrictions of6.3.1.magnetization levels reach full value in all directions while the6.3.1.3 Using the current levels specified by the formulasparticles are mobile on the surface under examination.Thegiven in Appendix X3 and Appendix X4.These current levelsresidual method shall only be used with the approval of theand formulas provide only a rough guide and shall only be usedCognizant Engineering Organization.in conjunction with either 6.3.1.1,or 6.3.1.2,or Cognizant6.2.7 Direct Magnetization-Direct magnetization is ac-Engineering Organization approval,or a combination plished by passing current directly through the part underIn some cases the formulas in Appendix X3 and Appendix X4examination.Electrical contact is made to the part using headmay lead to over magnetization of the work piece and careand tail stock,prods,clamps,magnetic leeches,or by othershould be exercised when using them.means.Caution shall be taken to ensure that the electrical6.3.2 Longitudinal Magnetization Using Coilscurrent is not flowing while contacts are being applied orLongitudinal magnetization is often accomplished by passingremoved and that excessive heating does not occur in any areacurrent through a coil encircling the part,or section of the part,of the part.Unless otherwise specified by the Cognizantto be examined(that is,by using a coil shot).This produces aEngineering Organization,prods shall not be used for themagnetic field parallel to the axis of the coil.The actualexamination of aerospace components(flight hardware)or oneffective distance must be demonstrated based on the particularfinished surfaces.part to be examined.For parts longer than these effective6.2.8 Indirect Magnetization-Indirect part magnetizationdistances,the entire length shall be examined by repositioninguses pre-formed coils,cable wraps,yokes,field(flux)flowthe part within the coil,allowing for approximately 10%fixtures,or a central conductor to induce a magnetic field in aeffective magnetic field overlap.See 6.3.1 for field strengthpart when no direct electrical contact is made.methods that can be used in coil magnetization.6.2.9 Induced Current Magnetization-Induced current6.4 Particle Application:magnetization(toroidal or circumferential field)is accom-6.4.1 Dry Magnetic Particle Application,Continuousplished by inductively coupling a part to an electrical coil inMethod-When using dry particles,the flow of magnetizingorder to create a suitable current flow within the part asillustrated in Fig.X5.2.This method is often advantageous oncurrent shall be initiated prior to application of the magneticring-shaped parts with a central aperture and with an L/D ratioparticles to the surface under examination and terminated afterless than three,especially where the elimination of arcing orpowder application has been completed and any excess blownburning is of vital importance.off.Precautions shall be taken to prevent any damage to thepart due to overheating.6.2.10 Parallel Current Induced Magnetization-This6.4.1.1 Apply dry powder so that a light,uniform,dust-likemethod of magnetization may occur when a ferromagnetic partcoating settles on the surface of the part under examinationis placed alongside and parallel to a current-carrying conduc-tor.A magnetic field will be induced in the part that is morewhile the part is being magnetized.Specially designed powdertransverse than circular.This type of magnetization shall not beblowers or shakers using compressed air or hand power shallbe used.The applicators shall introduce the particles into theused for magnetic particle testing unless approved by theair in a manner such that they reach the part surface in aCognizant Engineering Organization.uniform cloud with a minimum of force.6.2.11 Magnetization of Aerospace Lifting Hardware-The6.4.1.2 After the powder is applied,and before the magne-use of permanent magnets,electromagnetic yokes,coil wrapstizing force is removed,excess powder shall be removed,byor prods on aerospace lifting hardware must be approved by themeans of a dry air current with sufficient force to remove theCognizant Engineering Organization.excess particles if it interferes with interpretation and6.3 Magnetic Field Strength:evaluation,but not strong enough to disturb particles held by a6.3.1 Magnetic Field Strength-The applied magnetic fieldleakage field that is indicative of discontinuities.In order toshall have sufficient strength to produce satisfactoryrecognize the broad,fuzzy,lightly held powder patterns formedindications,but it must not be so strong that it causes theby near-surface discontinuities,the formation of indications