1、SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirelyvoluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefro
2、m, is the sole responsibility of the user.”SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions.QUESTIONS REGARDING THIS DOCUMENT: (724) 772-8512 FAX: (724) 776-0243TO PLACE A DOCUMENT
3、 ORDER; (724) 776-4970 FAX: (724) 776-0790SAE WEB ADDRESS http:/www.sae.orgCopyright 1991 Society of Automotive Engineers, Inc.All rights reserved. Printed in U.S.A.SURFACEVEHICLE400 Commonwealth Drive, Warrendale, PA 15096-0001INFORMATIONREPORTJ1242REV.MAR91Issued 1978-06Revised 1991-03Superseding
4、J1242 DEC88(R) ACOUSTIC EMISSION TEST METHODS1. ScopeThe scope of this SAE Information Report is to supply the user with sufficient information so that hemay decide whether acoustic emission test methods apply to his particular inspection problem. Detailedtechnical information can be obtained by ref
5、erring to Section 2.2. References2.1 Related PublicationsThe following publications are provided for information purposes only and are not arequired part of this document.Nondestructive Testing Handbook, Vol. 5, Acoustic Emission Testing, 1987, American Society forNondestructive Testing, Columbus, O
6、H 43228.Metals Handbook, Ninth Edition, Vol. 17, pp. 278294, Nondestructive Evaluation and Quality Control, 1989,ASM International, Metals Park, OH 44073.Tool and Manufacturing Engineers Handbook, Vol. 4, Quality Control and Assembly, 1987, Society ofManufacturing Engineers, Dearborn, MI 48121.“Acou
7、stic Emission,“ A Symposium presented December 78, 1971, at Bal Harbor, Florida. American Societyfor Testing and Materials, STP 505, (1972).Monitoring Structural Integrity by Acoustic Emission, A Symposium presented at Fort Lauderdale, Florida,January 1718, 1974. American Society for Testing and Mat
8、erials, STP 571, (1975).R. G. Liptai and D. O. Harris, “Acoustic Emission An Introductory Review.“ Materials Research andStandards, Vol. 11, No. 3, March 1971, pp. 810.C. R. Horak and A. F. Weyhreter, “Acoustic Emission System for Monitoring Components and Structures in aSevere Fatigue Noise Environ
9、ment,“ Materials Evaluation, Vol. 35, No. 5, May 1977, pp. 5963.J. C. Spanner, “Acoustic Emission Techniques and Applications,“ Intex Publishing Co., 1974.ASTM E 569, “Recommended Practice for Acoustic Emission Monitoring of Structures During ControlledStimulation,“ American Society for Testing and
10、Materials, Philadelphia, PA 19103.SAE J1242 Revised MAR91-2-ASTM E 610, “Definitions of Terms Relating to Acoustic Emission,“ American Society for Testing and Materials,Philadelphia, PA 19103.3. GeneralAcoustic emission is defined as a transient elastic wave generated by the rapid release of energyf
11、rom a localized source or sources within a material. The emission may be the result of any of several changestaking place in the material. A crack may be growing, the material may be undergoing permanent deformation,the internal structure may be changing due to heat treatment, or, in the case of com
12、posite materials, the fibersthat strengthen the material may be breaking.Some metals produce audible acoustic emission when they are bent. This is due to a deformation processcalled twinning. Tin, magnesium, and zinc show this effect. In tin this is known as “tin cry.“Acoustic emission technology is
13、 applicable to many nondestructive inspection problems. These includedetection and growth monitoring of fatigue cracks and stress-corrosion cracking, in-process determination ofweld quality, measurement of adhesive bond integrity, and in certain cases, the detection of loose parts inassembled compon
14、ents. Acoustic emission is particularly useful for monitoring the growth of a crack in orderto give warning of impending failure, and to detect deformation. It is also useful for surveying very largevolumes to locate emission sites. However, these sites often must be evaluated by supplementary metho
15、ds.3.1 There are several advantages of acoustic emission as a nondestructive test method when compared with morecommon methods such as radiography, ultrasonics, or magnetic particle techniques. Some of these are asfollows:a. It is capable of continuously monitoring a complete structure in real time.
16、b. It is very sensitive to the presence of active flaws when compared to other nondestructive testmethods, but usually requires these other methods to characterize the flaws.c. It can detect discontinuities that may be inaccessible to other nondestructive test methods.d. It is suitable for use durin
17、g proof testing in those structures that will be stressed sufficiently to producelocal plastic deformation during the test.3.2 Limitations of acoustic emission testing include:a. Inactive nonpropagating flaws cannot be detected.b. The significance of a detected source of emission cannot be assessed
18、unambiguously.c. As with many other nondestructive tests, acoustic emission tests are best used in conjunction withother nondestructive test methods, such as ultrasonics and radiography.d. The part or system under test must be stressed by an external stimulus.4. PrincipleThere are two types of acous
19、tic emission: burst and continuous. The length of a single burst ofemission is measured in microseconds. Continuous emission consists of a series of closely spaced noisepeaks of random amplitude that occur without interruption. Burst emissions usually have a larger amplitudethan continuous emissions
20、.A specimen must be stressed to generate acoustic emission. For a material with no active sources, emissionusually occurs while the stress is increasing. When the stress stops increasing, the emission stops. For manymaterials, excluding composites, when the force is reapplied it must exceed the prev
21、ious stress level before thespecimen will emit again.SAE J1242 Revised MAR91-3-Most of the acoustic emission signals that are useful in nondestructive testing are usually of low amplitude andhave frequencies that are above the audible range. Ordinarily they are between 100 kHz and 1 MHz,depending up
22、on the application. Low frequencies are filtered out in order to avoid interference from unwantedsources of noise such as machines or electrical equipment. The maximum distance that the signals will travelin a structure and still be detectable depends on the type of material and on the range of freq
23、uencies in thesignal. In steel pressure vessels, the acoustic emission caused by crack growth in welds can travel 10 m ormore from the source of the emission to the transducer that is detecting it.The location of a source of the emission is determined by triangulation methods. These are based on the
24、differences in the times required for the signals to reach the various elements in an array of transducers.5. ProcedureSpecially designed transducers are used for detecting the acoustic emission in a test specimenor structure. These must be coupled to the test specimen with a suitable liquid or grea
25、se, or by means of anepoxy cement or other adhesive. The output of the transducer is amplified and the low frequencies filtered out.Processing of the signal is usually very desirable. The simplest method for monitoring an acoustic emissiontest is to electronically convert the high frequency acoustic
26、 emission signals to lower frequencies that can beheard with the human ear. The most common methods, however, use chart recorders or cathode rayoscilloscopes to display the test results. Magnetic tape is used for storing larger amounts of data for laterprocessing or display. Specialized equipment fo
27、r the detection and processing of acoustic emission signals isavailable from several manufacturers. Data processing as applied to acoustic emission tests is limited only bythe creativity and sophistication of the user and the data processing facility.6. Notes6.1 Marginal IndiciaThe change bar (l) lo
28、cated in the left margin is for the convenience of the user in locatingareas where technical revisions have been made to the previous issue of the report. An (R) symbol to the leftof the document title indicates a complete revision of the report.PREPARED BY THE SAE IRON AND STEEL TECHNICAL COMMITTEE
29、 DIVISION 25NONDESTRUCTIVE TEST METHODSSAE J1242 Revised MAR91RationaleNot applicable.Relationship of SAE Standard to ISO StandardNot applicable.ApplicationThe scope of this SAE Information Report is to supply the user with sufficient information so thathe may decide whether acoustic emission test m
30、ethods apply to his particular inspection problem.Detailed technical information can be obtained by referring to Section 2.Reference SectionNondestructive Testing Handbook, Vol. 5, Acoustic Emission Testing, 1987, American Society forNondestructive Testing, Columbus, OH 43228.Metals Handbook, Ninth
31、Edition, Vol. 17, pp. 278294, Nondestructive Evaluation and Quality Control,1989, ASM International, Metals Park, OH 44073.Tool and Manufacturing Engineers Handbook, Vol. 4, Quality Control and Assembly, 1987, Society ofManufacturing Engineers, Dearborn, MI 48121.“Acoustic Emission,“ A Symposium pre
32、sented December 78, 1971, at Bal Harbor, Florida. AmericanSociety for Testing and Materials, STP 505, (1972).Monitoring Structural Integrity by Acoustic Emission, A Symposium presented at Fort Lauderdale,Florida, January 1718, 1974. American Society for Testing and Materials, STP 571,(1975).R. G. Li
33、ptai and D. O. Harris, “Acoustic Emission - An Introductory Review.“ Materials Research andStandards, Vol. 11, No. 3, March 1971, pp. 810.C. R. Horak and A. F. Weyhreter, “Acoustic Emission System for Monitoring Components and Structuresin a Severe Fatigue Noise Environment,“ Materials Evaluation, V
34、ol. 35, No. 5, May 1977,pp. 5963.J. C. Spanner, “Acoustic Emission Techniques and Applications,“ Intex Publishing Co., 1974.ASTM E 569, “Recommended Practice for Acoustic Emission Monitoring of Structures During ControlledStimulation,“ American Society for Testing and Materials, Philadelphia, PA 19103.ASTM E 610, “Definitions of Terms Relating to Acoustic Emission,“ American Society for Testing andMaterials, Philadelphia, PA 19103.Developed by the SAE Iron and Steel Technical Committee - Division 25Nondestructive Test MethodsSponsored by the SAE Iron and Steel Technical Committee
