1、Designation: E 2001 08Standard Guide forResonant Ultrasound Spectroscopy for Defect Detection inBoth Metallic and Non-metallic Parts1This standard is issued under the fixed designation E 2001; the number immediately following the designation indicates the year oforiginal adoption or, in the case of
2、revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide describes a procedure for detecting defects inmetallic and non-metallic parts using t
3、he resonant ultrasoundspectroscopy method. The procedure is intended for use withinstruments capable of exciting and recording whole bodyresonant states within parts which exhibit acoustical or ultra-sonic ringing. It is used to distinguish acceptable parts fromthose containing defects, such as crac
4、ks, voids, chips, densitydefects, tempering changes, and dimensional variations that areclosely correlated with the parts mechanical system dynamicresponse.1.2 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of
5、 this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E 1316 Terminology for Nondestructive ExaminationsE 1876 Test Method for Dynamic Youngs Modulus, ShearModulus, and P
6、oissons Ratio by Impulse Excitation ofVibration3. Terminology3.1 DefinitionsThe definitions of terms relating to con-ventional ultrasonics can be found in Terminology E 1316.3.2 Definitions of Terms Specific to This Standard:3.2.1 resonant ultrasonic spectroscopy (RUS), na nonde-structive examinatio
7、n method, which employs resonant ultra-sound methodology for the detection and assessment of varia-tions and mechanical properties of a test object. In thisprocedure, whereby a rigid part is caused to resonate, theresonances are compared to a previously defined resonancepattern. Based on this compar
8、ison the part is judged to be eitheracceptable or unacceptable.3.2.2 swept sine method, nthe use of an excitation sourceto create a transient vibration in a test object over a range offrequencies. Specifically, the input frequency is swept over arange of frequencies and the output is characterized b
9、y aresonant amplitude response spectrum.3.2.3 impulse excitation method, nstriking an object witha mechanical impact, or electromagnetic field (laser and/orEMAT) causing multiple resonances to be simultaneouslystimulated.3.2.4 resonant inspection (RI), nany induced resonantnondestructive examination
10、 method employing an excitationforce to create mechanical resonances for the purpose ofidentifying a test objects conformity to an established accept-able pattern.4. Summary of the Technology (1)34.1 Introduction:4.1.1 In addition to its basic research applications in phys-ics, materials science, an
11、d geophysics, Resonant UltrasoundSpectroscopy (RUS) has been used successfully as an appliednondestructive testing tool. Resonant ultrasound spectroscopyin commercial, nondestructive testing has a few recognizablenames including, RUS Nondestructive Testing, Acoustic Reso-nance Spectroscopy (ARS), an
12、d Resonant Inspection. Earlyreferences to this body of science often are termed the “sweptsine method.” It was not until 1990 (2) that the name ResonantUltrasound Spectroscopy appeared, but the two techniques aresynonymous. Additionally, impulse methods, like the strikingof a rail car wheel with a h
13、ammer, and listening for theresponses, have been used for over 100 years to detect theexistence of large cracks. RUS based techniques are becomingcommonly used in the manufacture of steel, ceramic, andsintered metal parts. In these situations, a part is vibratedmechanically, and defects are detected
14、 based on changes in thepattern of resonances or variations from theoretically calcu-lated or empirically acceptable spectra. RUS measures allresonances, in a defined range, of the part rather than scanningfor individual defects. In a single measurement, RUS-based1This guide is under the jurisdictio
15、n of ASTM Committee E07 on Nondestruc-tive Testing and is the direct responsibility of Subcommittee E07.06 on UltrasonicMethod.Current edition approved July 1, 2008. Published July 2008. Originally approvedin 1998. Last previous edition approved in 2003 as E 2001 - 98(2003).2For referenced ASTM stan
16、dards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The boldface numbers in parentheses refer to the list of references at the end ofthis
17、 guide.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.techniques potentially can test for numerous defects includingcracks, chips, cold shuts, inclusions, voids, oxides, contami-nants, missed processes or operations, and variations
18、in dimen-sion, hardness, porosity, nodularity, density, and heat treatment.Since the RUS measurement yields a whole body response, itis often difficult to discriminate between defect types. Thetechnique is effective for detecting parts with structural anoma-lies, but less effective for diagnosing th
19、e exact location orcause of an anomaly within a part. Nevertheless, on certaintypes of parts, it can be accurate, fast, inexpensive and requireno human judgment, making 100 % examination possible inselected circumstances. Many theoretical texts (3) discuss therelationship between resonances and elas
20、tic constants andinclude the specific application of RUS to the determination ofelastic constants (4). The technology received a quantumincrease in attention when Migliori published a review article,including the requisite inexpensive electronic designs andprocedures from which materials properties
21、could be measuredquickly and accurately (5). The most recent applicationsinclude studies in ultrasonic attenuation, modulus determina-tions, thermodynamic properties, structural phase transitions,superconducting transitions, magnetic transitions, and the elec-tronic properties of solids.Acompendium
22、of these applicationsmay be found in the Migliori (1) text. Resonant ultrasoundspectroscopy also found use in the study of the elasticproperties of the Apollo moon rocks (6).4.1.2 This guide is intended to provide a practical introduc-tion to RUS-based nondestructive test (NDT), highlightingsuccessf
23、ul applications and outlining failures, limitations, andpotential weaknesses. Vibrational resonances are consideredfrom the perspective of defect detection in 4.2.In4.3 and 4.4,a review of some of the types of RUS measurements are givenand 4.6 examines the common practice of using the impulseexcitat
24、ion method. In 4.6, some example implementations andconfigurations of RUS systems and their applications arepresented. Finally, the guide concludes with a discussion ofconstraints, which limit the effectiveness of RUS.4.2 Mode Shapes and Defects:4.2.1 Resonant ultrasound spectroscopy/NDT techniques,
25、operate by driving a part at given frequencies and measuring itsmechanical response (Fig. 1 contains a schematic one embodi-ment of a RUS apparatus). The process proceeds in smallfrequency steps over some previously determined region ofinterest. During such a sweep, the drive frequency typicallybrac
26、kets a resonance. When the excitation frequency is notmatched to one of the parts resonance frequencies, very littleenergy is coupled to the part; that is, there is little mechanicalvibration. At resonance, however, the energy delivered to thepart is coupled generating much larger mechanical vibrati
27、ons.A parts resonance frequencies are determined by the standarddynamic equations of motion, which include variables formass, stiffness, and damping. From a materials perspective,this is affected by its dimensions (to include the shape andgeometry) and by the density and the elastic constants of the
28、material. The required frequency window for a scan dependson the size of the part, its mechanical rigidity, and the size ofthe defect being sought.4.2.2 Vibrational resonances produce a wide range of dis-tortions. These distortions include shapes, which bend andtwist. It is known that increasing the
29、 length of a cylinder willlower some resonant frequencies. Similarly, reducing thestiffness, that is, reducing the relevant elastic constant, lowersthe associated resonant frequency for most modes; thus, for agiven part, the resonant frequencies are measures of stiffness,and knowledge of the mode sh
30、ape helps to determine whatqualities of the part affect those frequencies. If a defect, such asa crack, is introduced into a region under strain, it will reducethe effective stiffness, that is, the parts resistance to deforma-tion, and will shift downward the frequency of resonant modesthat introduc
31、e strain at the crack. This is one basis for detectingdefects with RUS-based techniques.4.2.3 The torsional modes represent a twisting of a cylinderabout its axis. These resonances are easily identified becausetheir frequencies remain constant for fixed length, independentof diameter. A crack will r
32、educe the ability of the part to resisttwisting, thereby reducing the effective stiffness, and thus, thefrequency of a torsional mode. A large defect can be detectedreadily by its effect on the first few modes; however, smallerdefects have much more subtle effects on stiffness, andtherefore, require
33、 higher frequencies (high-order modes) to bedetected. Detection of very small defects may require using thefrequency corresponding to the fiftieth, or even higher, mode.FIG. 1 Schematic of the Essential Electronic Building Blocks to Employ RUS in a Manufacturing EnvironmentE2001082Some modes do not
34、produce strain in the end of the cylinder,therefore, they cannot detect end defects. To detect this type ofdefect, a more complex mode is required, the description ofwhich is beyond the scope of this specification. A defect in theend will reduce the effective stiffness for this type of mode, andthus
35、, will shift downward the frequency of the resonance. Ingeneral, it must be remembered that most modes will exhibitcomplex motions, and for highly symmetric objects, can belinear combinations of several degenerate modes, as discussedin 4.3.2.4.3 General Approaches to RUS/NDT:4.3.1 Test Evaluation Me
36、thods (1)Once a fingerprint hasbeen established, for conforming parts, numerous algorithmscan be employed to either accept or reject the part. Forexample, if a frequency 650 Hz can be identified for allconforming parts, the detection of a peak outside of thisboundary condition will cause the compute
37、r code to signal a“test reject” condition. The code, rather than the inspector,makes the accept/reject decision. The following sections willexpand on some of these sorting criteria.4.3.2 Frequency Shifts:4.3.2.1 Resonant ultrasound spectroscopy measurementsgenerally produce strains (even on resonanc
38、e) that are wellwithin the elastic limit of the materials under test, that is, theatomic displacements are small in keeping with the “nonde-structive” aspect of the testing. If strains are applied above theelastic limit, a crack will tend to propagate, causing a mechani-cal failure. Note that certai
39、n important engineering properties,for example, the onset of plastic deformation, yield strength,etc., generally are not derivable from low-strain elastic prop-erties. Sensitivity of the elastic properties of an object to thepresence of a crack depends on the stiffness and geometry ofthe sample unde
40、r test. This concept is expanded upon under4.4.3.4.3.2.2 Fig. 2 shows an example of the resonance spectrumfor a conical ceramic part. Several specific types of modes arepresent in this scan, and their relative shifts could be used todetect defects as discussed above; however, the complexity issuch t
41、hat, for NDT purposes, some selections must be made sothat only a portion of such a large amount of information isused. For simple part geometries, the mode type and frequencycan be calculated, and selection of diagnostic modes can bebased on these results. For complex geometries, empiricalapproache
42、s have been developed to identify efficiently diag-nostic modes for specific defects. In this process, a technicianmeasures the spectra for a batch of known good and bad parts.The spectra are compared to identify diagnostic modes whoseshift correlates with the presence of the defect. The key is tois
43、olate a few resonances, which differ from one another, whenknown defects are present in the faulty parts.4.3.3 Peak SplittingOne of the techniques employed foraxially symmetric parts is identified in texts on basic wavephysics (7). Some test procedures are based on simple fre-quency changes while ot
44、hers include the recognition thatsymmetry is broken when a defect is present in a homoge-neous, isotropic symmetrical part. These techniques employsplitting of degeneracies or simply “splitting.” A cylinderactually has two degenerate bending modes, both orthogonal toits axis. The bending stiffness f
45、or both of these modes, andtherefore their resonance frequency, is proportional to thediameter of the cylinder. Because the part is symmetric, bothmodes have the same stiffness, and therefore, the same fre-quency (the modes are said to be degenerate and appear to bea single resonance). When the symm
46、etry is broken by a chip,however, the effective diameter is reduced for one of theorthogonal modes. This increases the frequency for that mode,so both modes are seen. In addition, a crack or inclusion affectsthe symmetry. This splitting of the resonances is illustrated inFig. 3, which shows spectra
47、for a good part and two defectiveparts. The part is a steel cylinder. Fig. 3 also demonstrates auseful feature of this particular technique, that is, the size of thesplitting is proportional to the size of the defect. It is importantto recognize that not all resonance peaks are degenerate. Puretorsi
48、onal modes, for example, are not degenerate, so theycannot be used for splitting.4.3.4 Phase Information and Peak Splittings:4.3.4.1 In practice, the same empirical approach describedfor frequency shifts is used to identify diagnostic modes whosesplittings correlate with the size of a defect of inte
49、rest. Thesensitivity of this type of measurement is enhanced by theinterference, which occurs between closely-spaced peaks. Thedestructive interference develops into a visible spectral split-ting which would not be noticeable with the amplitude spec-trum (the real and quadrature components add to form theFIG. 2 Typical Broad-Spectrum ScanE2001083amplitude response). Most commercial systems function rea-sonably well without this attribute, but the problem can beexacerbated when the material exhibits resonance line widthswhich are greater than 1 % of the frequency. Under s
