1、Designation:E149502 (Reapproved 2007) Designation: E1495/E1495M 12Standard Guide forAcousto-Ultrasonic Assessment of Composites, Laminates,and Bonded Joints1This standard is issued under the fixed designation E1495/E1495M; the number immediately following the designation indicates the yearof origina
2、l adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This guide explains the rationale and basic technology for the ac
3、ousto-ultrasonic (AU) method. Guidelines are given fornondestructive evaluation (NDE) of flaws and physical characteristics that influence the mechanical properties and relative strengthof composite structures (for example, filament-wound pressure vessels), adhesive bonds (for example, joints betwee
4、n metal plates),and interlaminar and fiber/matrix bonds in man-made composites and natural composites (for example, wood products).1.2 This guide covers technical details and rules that must be observed to ensure reliable and reproducible quantitative AUassessments of laminates, composites, and bond
5、ed structures. The underlying principles, prototype apparatus, instrumentation,standardization, examination methods, and data analysis for such assessments are covered. Limitations of the AU method andguidelines for taking advantage of its capabilities are cited.1.3 The objective of AU is to assess
6、subtle flaws and associated strength variations in composite structures and bonded joints.Discontinuities such as large voids, disbonds, or extended lack of contact at interfaces can be assessed by other NDE methods suchas conventional ultrasonics.1.4 Additional information may be found in the publi
7、cations cited in the list of references at the end of this guide. The referencedworks provide background on research, applications, and various aspects of signal acquisition, processing, and interpretation.1.5The values stated in SI units are to be regarded as the standard. The values given in paren
8、theses are for information only.1.5 UnitsThe values stated in either SI units or inch-pound units are to be regarded as standard. The values stated in eachsystem may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from thetwo systems may re
9、sult in non-conformance with the standards.1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulator
10、ylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E543 Specification for Agencies Performing Nondestructive TestingE1316 Terminology for Nondestructive Examinations2.2 ASNT Standard:3ANSI/ASNT CP-189 Standard for Qualification and Certification of Nondestructive Testing PersonnelS
11、NT-TC-1A Recommended Practicem for Personnel Qualifications and Certification in Nondestructive Testing2.3 AIA Document:4NAS-410 Certification and Qualification of Nondestructive Testing Personnel3. Terminology3.1 Definitions:3.1.1 acousto-ultrasonics (AU)a nondestructive examination method that use
12、s induced stress waves to detect and assess the1This guide is under the jurisdiction of ASTM Committee E07 on Nondestructive Testing and is the direct responsibility of Subcommittee E07.04 on Acoustic EmissionMethod.Current edition approved July 1, 2007. Published July 2007. Originally approved in 1
13、992. Last previous edition approved in 2002 as E1495-02. DOI:10.1520/E1495-02R07.Current edition approved June 15, 2012. Published July 2012. Originally approved in 1992. Last previous edition approved in 2007 as E1495 - 02 (2007). DOI:10.1520/E1495-12.2For referenced ASTM standards, visit the ASTM
14、website, www.astm.org, or contact ASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3Available from American Society for Nondestructive Testing (ASNT), P.O. Box 28518, 1711 Arlingate Ln., Co
15、lumbus, OH 43228-0518, http:/www.asnt.org.4Available from Aerospace Industries Association of America, Inc. (AIA), 1000 Wilson Blvd., Suite 1700, Arlington, VA 22209-3928, http:/www.aia-aerospace.org.1This document is not an ASTM standard and is intended only to provide the user of an ASTM standard
16、an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is
17、to be considered the official document.*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.diffuse defect states, damage conditions, and variations of mechanical properties
18、 of an examination structure. The AU methodcombines aspects of acoustic emission (AE) signal analysis with ultrasonic materials characterization methods (TerminologyE1316).3.1.2 Additional related definitions may be found in Terminology E1316.3.2 Definitions of Terms Specific to This Standard:3.2.1
19、stress wave factor (SWF)a generic measure of the relative energy loss (attenuation) or propagation efficiency of stresswaves generated by the AU method. There are many ways to define and calculate the SWF. Several of these are described inSection 11 of this guide.4. Summary of Guide4.1 GeneralTwo pr
20、obes are attached to a sample in a send-receive configuration. One (a pulsed sending probe) is optimizedfor wave generation, while the other (a receiving probe) is optimized for signal sensing. The probes are attached to the samplesurface at normal incidence. The usual, and often most practical, con
21、figuration has piezoelectric probes, a sender and receiver, onthe same side of the examination part (1).5Measurements are performed by allowing ultrasonic stress waves to interact with avolume of material between the probes. The waves are modified by the material microstructure and morphology (2).4.
22、2 PrincipleTheAU method measures the relative efficiency of stress wave propagation in a material. The dominant attributemeasured is stress wave attenuation. Lower attenuation, a high SWF value, means better stress wave energy transmission for manycomposites and, therefore, better transmission and r
23、edistribution of dynamic strain energy. More efficient strain energy transfer andstrain redistribution during loading or impact corresponds to increased strength and fracture resistance in composite structures andadhesive bonds. A lower SWF usually indicates regions in which strain energy is likely
24、to concentrate and result in crack growthand fracture (3).4.3 Structure Configuration EffectsIn monolithic plates and homogeneous composite slabs, the SWF will exhibit signalattenuation effects due to variations in microstructure, morphology, porosity, cure state, microcrack populations, etc. (4). A
25、 lowerSWF typically corresponds to regions of higher attenuation. In laminated structures or bonded joints, however, interfaces andbondlines can produce either lower or higher SWF values, depending on the bond quality (5). Delaminated regions can producehigher SWF values because more energy is refle
26、cted or channeled to the receiving probe.4.4 In-Plane MeasurementsOffsetting probes enables the collection of stress wave reverberations that have traveled in-planefrom sender to receiver. It is therefore possible to measure in-plane, mechanical property variations in principal load directions infib
27、er-reinforced laminates or adhesively bonded joints (that is, properties such as interlaminar shear strength and adhesive bondstrength).4.5 Signal Collection CriterionWith theAU method, instead of singling out specific echoes, all of the multiple reverberations,including signals from internal reflec
28、tors and scatterers, are collected and analyzed together. Even with pulse-echo orthrough-transmission configurations, all stress wave reflections and reverberations in a local volume of material are collected andevaluated, as in backscatter, forward-scatter, and diffuse field analysis.4.6 Wavelength
29、 CriterionIn composite panels or bonded plates, the sender should produce wavelengths that are comparableto or less than the panel or plate thickness. Suitable wavelengths are those passed by the examination piece at frequencies equalto or greater than the sending probe center frequencies.5. Signifi
30、cance and Use5.1 GeneralConventional ultrasonics should be considered first for the detection of overt flaws such as delaminations incomposites. Thereafter, AU should be considered for composites that are proved to be free of major flaws or discontinuities. TheAU method is intended almost exclusivel
31、y for assessing the collective effects of dispersed defects and subcritical flaw populations.These are material aberrations that influence AU measurements and also underlie mechanical property variations, dynamic loadresponse, and impact and fracture resistance.5.2 Specific AdvantagesThe AU method c
32、an be used to evaluate composite laminate and bond quality using access to onlyone surface as, for example, the exterior surface of pressure vessels. It is unnecessary to utilize angle beam fixtures because themethod can always be applied with probes at normal incidence. The method can be applied us
33、ing dry coupling with elastomer padsattached to the probes, and there is no need to immerse the examination object in water.5.3 General ApplicationsThe AU method was devised to assess diffuse discontinuity populations and any associated changesof the mechanical properties of composites and composite
34、-like materials. The AU method has been used to evaluatefiber-reinforced composites (6), composite laminates (7), filament-wound pressure vessels (8), adhesive bonds (9), paper and woodproducts (10), and cable and rope (11). The method has been shown to be particularly practical for assessing the st
35、rength ofadhesively bonded joints. It has also been shown to be useful for assessing microporosity (12), micro-cracking (13), hydrothermalaging (14), and damage produced by impacts (15) and fatigue (16).6. Basis of Application6.1 Personnel Qualification5The boldface numbers in parentheses refer to t
36、he list of references at the end of this guide.E1495/E1495M 1226.1.1 If specified in the contractual agreement, personnel performing examinations to this standard shall be qualified inaccordance with a nationally recognized NDT personnel qualification practice or standard such as ANSI/ASNT CP-189,SN
37、T-TC-1A, NAS-410, or a similar document and certified by the employer or certifying agency, as applicable. The practice orstandard used and its applicable revision shall be identified in the contractual agreement between the using parties.6.2 Qualification of Nondestructive Agencies6.2.1 If specifie
38、d in the contractual agreement, NDT agencies shall be qualified and evaluated as described in Practice E543.The applicable edition of Practice E543 shall be specified in the contractual agreement.6.3 Proper application of the AU method requires the involvement of an NDE specialist to plan and guide
39、the examinationprocedure. Knowledge of the principles of ultrasonic examination is required. Personnel applying AU should be experiencedpractitioners of conventional ultrasonic and acoustic emission examination and associated methods for signal acquisition,processing, and interpretation.6.4 Particul
40、ar emphasis should be placed on personnel having proficiency in computer signal processing and the use of digitalmethods for time and frequency domain signal analysis. Familiarity with ultrasonic spectrum analysis using digital Fouriertransforms is mandatory. Spectral distribution, multiple regressi
41、on, and pattern recognition analyses and adaptive learningprocedures are important.6.5 Application of the AU method also requires proficiency in developing and designing reference standards. The developmentof reference standards is needed for each type of material and configuration to be examined. B
42、ecauseAU measurements are relativeand comparative, experimental examinations confirmed by destructive testing are needed to avoid ambiguities in the interpretationof results.7. Limitations7.1 GeneralThe AU method possesses the limitations common to all ultrasonic methods that attempt to measure eith
43、erabsolute or relative attenuation. When instrument settings and probe configurations are optimized for AU, they are unsuitable forconventional ultrasonic flaw detection.7.2 Signal Reproducibility FactorsThe AU results may be affected adversely by the following factors: (1) improper selectionof type
44、 and amount of couplant, (2) couplant thickness variations and bubbles, (3) specimen surface roughness and texture, (4)probe misalignment and insufficient pressure, (5) probe resonances and insufficient damping, and (6) insufficient instrumentbandwidth.8. Standardization8.1 Self-StandardizationThe s
45、ender and receiver probes can be used to verify each other. Deficiencies in the instrumentationand probe response become evident by comparing the results with the standard waveforms established previously for a referenceitem. Commercial ultrasonic probes and AE sensors respond to deformation (stress
46、) waves in a complex fashion that involves bothnormal and in-plane displacements of the examination sample surface. Although it is possible to standardize such probes in anabsolute sense, even sensors of the same design and specification should be treated as unique and definitely noninterchangeable.
47、8.2 Stress Wave Factor NormalizationRegardless of how the SWF is defined, it is practical to normalize it relative to somestandard value, for example, the maximum value found for the optimum condition of a representative material sample or structure.This is appropriate where many nominally identical
48、 articles will be examined.8.3 Reference StandardsNormalization of the SWF is the first step toward establishing a reference standard. The second stepis to fabricate a set of samples exhibiting the full range of expected material conditions and flaw states. One of these samples shouldrepresent the o
49、ptimum condition of the material. This procedure should be followed by the development of benchmark structuresthat can be used as comparative standards.9. System Configuration9.1 Standard ConfigurationFour possible AU probe configurations are shown in Fig. 1. With the probes on the same side ofa panel, examination proceeds by holding the probes in a fixture and moving them as a unit to cover the examined area. For zerooffset between probes, the configuration reduces to either the pulse-echo or through-transmission mode, as shown in Fig. 1 (b) and(d) respectively.
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