ASTM E650 E650M-2012 red 0880 Standard Guide for Mounting Piezoelectric Acoustic Emission Sensors《安装压电声发射传感器的标准指南》.pdf

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1、Designation:E65097 (Reapproved 2007) Designation: E650/E650M 12Standard Guide forMounting Piezoelectric Acoustic Emission Sensors1This standard is issued under the fixed designation E650/E650M; the number immediately following the designation indicates the yearof original adoption or, in the case of

2、 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 document provides guidelines for mounting piezoelectric acoustic emission (AE) sensors.1.

3、21.2 UnitsThe values stated in either SI units or inch-pound units are to be regarded separately as standard. The values statedin each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining valuesfrom the two systems may result in non-conforma

4、nce with the standard.1.3 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 regulatorylimitations prior to

5、 use.2. Referenced Documents2.1 ASTM Standards:2E976 Guide for Determining the Reproducibility of Acoustic Emission Sensor ResponseE1316 Terminology for Nondestructive Examinations3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 bonding agenta couplant that physically attaches

6、the sensor to the structure.3.1.2 couplanta material used at the structure-to-sensor interface to improve the transfer of acoustic energy across theinterface.3.1.3 mounting fixturea device that holds the sensor in place on the structure to be monitored.3.1.4 sensora detection device that transforms

7、the particle motion produced by an elastic wave into an electrical signal.3.1.5 waveguide, acoustica device that couples acoustic energy from a structure to a remotely mounted sensor. For example,a solid wire or rod, coupled to a sensor at one end and to the structure at the other.3.2 Definitions:3.

8、2.1 For definitions of additional terms relating to acoustic emission, refer to Terminology E1316.4. Significance and Use4.1 The methods and procedures used in mounting AE sensors can have significant effects upon the performance of thosesensors. Optimum and reproducible detection of AE requires bot

9、h appropriate sensor-mounting fixtures and consistentsensor-mounting procedures.5. Mounting Methods5.1 The purpose of the mounting method is to hold the sensor in a fixed position on a structure and to ensure that the acousticcoupling between the sensor and the structure is both adequate and constan

10、t. Mounting methods will generally fall into one of thefollowing categories:5.1.1 Compression MountsThe compression mount holds the sensor in intimate contact with the surface of the structurethrough the use of force. This force is generally supplied by springs, torqued-screw threads, magnets, tape,

11、 or elastic bands. 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 1985. Last previous editio

12、n approved in 2002 as E650-97(2002)1. DOI:10.1520/E0650-97R07.Current edition approved June 15, 2012. Published July 2012. Originally approved in 1985. Last previous edition approved in 2007 as E650 - 97(2007). DOI:10.1520/E0650-12.2For referenced ASTM standards, visit the ASTM website, www.astm.org

13、, 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.1This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what chang

14、es 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 to be considered the offici

15、al 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.use of a couplant is strongly advised with a compression mount to maximize the transmission of acoustic ener

16、gy through thesensor-structure interface.5.1.2 BondingThe sensor may be attached directly to the structure with a suitable adhesive. In this method, the adhesive actsas the couplant. The adhesive must be compatible with the structure, the sensor, the environment, and the examination procedure.6. Mou

17、nting Requirements6.1 Sensor SelectionThe correct sensors should be chosen to optimally accomplish the acoustic-emission examinationobjective. Sensor parameters to be considered are as follows: size, sensitivity, frequency response, surface-motion response, andenvironmental and material compatibilit

18、y. When a multichannel acoustic-emission examination is being conducted, a subset ofsensors with characteristics similar to each other should be selected. See Guide E976 for methods of comparing sensorcharacteristics.6.2 Structure PreparationThe contacting surfaces should be cleaned and mechanically

19、 prepared. This will enhance thedetection of the desired acoustic waves by assuring reliable coupling of the acoustic energy from the structure to the sensor.Preparation of these surfaces must be compatible with the construction materials used in both the sensor and the structure. Possiblelosses in

20、acoustic energy transmission caused by coatings such as paint, encapsulants, loose-mill scale, weld spatter, and oxidesas well as losses due to surface curvature at the contact area must be considered.6.3 Couplant or Bonding Agent Selection:6.3.1 The type of couplant or bonding agent should be selec

21、ted with appropriate consideration for the effects of the environment(for example, temperature, pressure, composition of gas, or liquid environment) on the couplant and the constraints of theapplication. It should be chemically compatible with the structure and not be a possible cause of corrosion.

22、In some cases, it maybe a requirement that the couplant be completely removable from the surface after examination. In general, the selection of thecouplant is as important from an environmental standpoint as it is from the acoustical standpoint.6.3.2 For sensors that are primarily sensitive to part

23、icle motion perpendicular to their face, the viscosity of the couplant is notan important factor. Most liquids or greases will work as a couplant if they wet the surfaces of both the structure and the sensor.For those few sensors which are sensitive primarily to motion in the plane of their face, ve

24、ry high-viscosity couplant or a rigidbond is recommended.6.3.3 The thickness of the couplant may alter the effective sensitivity of the sensor. The thinnest practical layer of continuouscouplant is usually the best. Care should be taken that there are no entrapped voids in the couplant. Unevenness,

25、such as a taperfrom one side of the sensor to the other, can also reduce sensitivity or produce an unwanted directionality in the sensor response.6.3.4 A useful method for applying a couplant is to place a small amount of the material in the center of the sensor face, thencarefully press the sensor

26、on to the structure surface, spreading the couplant uniformly from the center to the outside of the sensorface.6.3.5 In some applications, it may be impractical to use a couplant because of the nature of the environment (for example, veryhigh temperatures or extreme cleanliness requirements). In the

27、se situations, a dry contact may be used, provided sufficientmechanical force is applied to hold the sensor against the structure. The necessary contact pressure must be determinedexperimentally. As a rough guide, this pressure should exceed 0.7 MPa (100 psi). 100 psi.6.3.6 Great care must be taken

28、when bonding a sensor to a structure. Surface deformation, that can be produced by eithermechanical loading or thermal expansion, may cause a bond to crack, peel off, or, occasionally, destroy the sensor. Bond crackingis a source of acoustic emission. A compliant adhesive may work in some cases. If

29、differential expansion between the sensor, thebond, and the surface is a possibility, a suitable bonding agent should be confirmed by experiment.6.3.7 When bonds are used, the possibility of damaging either the sensor or the surface of the structure during sensor removalmust be considered.6.3.8 The

30、use of double-sided adhesive tape as a bonding agent is not recommended.6.4 Mounting Fixture Selection :6.4.1 Mounting fixtures must be constructed so that they do not create extraneous acoustic emission or mask valid acousticemission generated in the structure being monitored.6.4.1.1 The mount must

31、 not contain any loose parts of particles.6.4.1.2 Permanent mounting may require special techniques to prevent sensor movement caused by environmental changes.6.4.1.3 Detection of surface waves may be suppressed if the sensor is enclosed by a welded-on fixture or located at the bottomof a threaded h

32、ole. The mounting fixture should always be designed so that it does not block out a significant amount of acousticenergy from any direction of interest.6.4.2 The mounting fixture should provide support for the signal cable to prevent the cable from stressing the sensor or theelectrical connectors. I

33、n the absence of a mounting fixture, some form of cable support should be provided. Care should be takento ensure that the cable can neither vibrate nor be moved easily. False signals may be generated by the cable striking the structureand by triboelectric effects produced by cable movement.6.4.3 Wh

34、ere necessary, protection from the environment should be provided for the sensor or sensor and mounting fixture.6.4.4 The mounting fixture should not affect the integrity of the structure being monitored.6.4.4.1 Permanently installed mounting fixtures must be constructed of a material compatible wit

35、h the structure. Possibleelectrolytic effects or other forms of corrosion must be considered when designing the mounting fixture.E650/E650M 1226.4.4.2 Alterations of the local environment by the mount, such as removal of the insulation, must be carefully evaluated andcorrected if necessary.6.4.5 The

36、 mounting fixture should be designed to have a minimal effect on the response characteristics of the sensor.6.5 WaveguidesWhen adverse environments make direct contact between the sensor and the structure undesirable, an acousticwaveguide may be used to convey the acoustic signal from the structure

37、to the sensor. The use of a waveguide inserts anotherinterface with its associated losses between the structure and the sensor and will distort, to some degree, the characteristics of theacoustic wave.6.5.1 An acoustic waveguide should be mounted so as to ensure that its surface will not contact any

38、 materials that will causesignal damping in the waveguide.6.5.2 If acoustic waveguides are used when acoustic-emission source location is being performed, the extra time delay in thewaveguides must be accounted for in the source location program.7. Verification of Response7.1 After the sensor(s) are

39、 mounted on a structure, adequate response should be verified by injecting acoustic signals into thestructure and examining the detected signal either on an oscilloscope or with the AE system to be used in the examination. If thereis any doubt as to the sensor response, the sensor should be remounte

40、d.7.1.1 The test signal may be injected by an external source such as the Hsu-pencil source, or a gas jet (helium or other suitablegas), or by applying an electrical pulse to another sensor mounted on the structure. For a description of these methods see GuideE976.7.2 Periodic VerificationOn an exte

41、nded acoustic emission examination, it may be desirable to verify the response of thesensors during the examination. Verification should be performed whenever circumstances indicate the possibility of a change inthe coupling efficiency.7.3 Post VerificationAt the end of an acoustic emission examinat

42、ion, it is good practice to verify that all sensors are stillworking and that there have been no dramatic changes in coupling efficiencies.8. Report8.1 Any report of the mounting practice should include details of the sensor mounting fixture(s), surface preparation method,and the couplant that was u

43、sed.9. Keywords9.1acoustic emission; acoustic emission sensors; acoustic emission transducers; AE; bonding agent; couplant; mounting fixture;waveguide9.1 acoustic emission; acoustic emission sensors; acoustic emission transducers;AE; bonding agent; couplant; mounting fixture;waveguideSUMMARY OF CHAN

44、GESCommittee E07 has identified the location of selected changes to this standard since the last issue(E650 - 97(2007) that may impact the use of this standard. (June 15, 2012)(1) Changed designation to be a combined units standard.(2) Added new 1.2 to include combined units standard statement.(3) C

45、hanged values in 6.3.5 to the correct combined units format.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such pa

46、tent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited ei

47、ther for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair

48、 hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this stan

49、dard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).E650/E650M 123