1、Designation: F 2174 02 (Reapproved 2008)An American National StandardStandard Practice forVerifying Acoustic Emission Sensor Response1This standard is issued under the fixed designation F 2174; 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 practice is used for routinely checking the sensi-tivity of acoustic emission (AE) sensors
3、. It is intended toprovide a reliable, precisely specified way of comparing a setof sensors or telling whether an individual sensors sensitivityhas degraded during its service life, or both.1.2 The procedure in this practice is not a “calibration” anddoes not give frequency-response information.1.3
4、The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.4 This practice does not purport to recommend one sensormanufacturer over another nor does it imply that one type ofsensor will react differently from another when using thispro
5、cedure.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Refer
6、enced Documents2.1 ASTM Standards:2E 650 Guide for Mounting Piezoelectric Acoustic EmissionSensorsE 750 Practice for CharacterizingAcoustic Emission Instru-mentationE 976 Guide for Determining the Reproducibility of Acous-tic Emission Sensor Response3. Significance and Use3.1 Degradation in sensor p
7、erformance can occur due todropping, mechanical shock while mounted on the test struc-ture, temperature cycles, and so forth. It is necessary anddesirable to have a simple measurement procedure that willcheck the consistency of sensor response, while holding allother variables constant.3.2 While tes
8、t blocks of many different kinds have beenused for this purpose for many years, an acrylic polymer rodoffers the best all-around combination of suitable acousticproperties, practical convenience, ease of procurement, andlow cost.3.3 Because the acoustic properties of the acrylic rod areknown to depe
9、nd on temperature, this practice requires that therod, sensors, and couplant be stabilized at the same workingtemperature, prior to application of the practice.3.4 Attention should be paid to storage conditions for theacrylic polymer rod. For example, it should not be left in afreezing or hot enviro
10、nment overnight, unless it is given timefor temperature stabilization before use.3.5 Properly applied and with proper record keeping, thispractice can be used in many ways, such as:3.5.1 To determine when a sensor is no longer suitable foruse.3.5.2 To check sensors that have been exposed to high-ris
11、kconditions such as dropping, overheating, and so forth.3.5.3 To get an early warning of sensor degradation overtime.3.5.4 To obtain matched sets of sensors and preamplifiers.3.5.5 To verify sensors quickly but accurately in the field,and to assist troubleshooting when a channel does not pass aperfo
12、rmance check.4. Apparatus4.1 Acrylic Polymer Cylindrical Rod (Fig. 1) should beused. The actual material of the acrylic polymer rod ispoly(methylmethacrylate)(PMMA).4.1.1 Dimensions of the rod should be 78.74 cm (31 in.)long by 3.81 cm (1.5 in.) in diameter with ends cut true andsmooth with a surfac
13、e finish of 0.4 m rms (0.16 in.).4.1.2 Other lengths of rod are acceptable, provided thatthere is sufficient distance to attenuate and prevent reflectedsignals from the non-sensor end of the rod reaching the sensor.4.1.3 A permanent reference mark (for example, an “X”) isplaced on the rod at a dista
14、nce of 10.16 cm (4 in.) from oneend; this marks the spot where the lead is to be broken. It isconvenient to provide a very small spotface, for example, 0.791This practice is under the jurisdiction of ASTM Committee F18 on ElectricalProtective Equipment for Workers and is the direct responsibility of
15、 SubcommitteeF18.55 on Inspection and Non-Destructive Test Methods for Aerial Devices.Current edition approved Oct. 1, 2008. Published December 2008. Originallyapproved in 2002. Last previous edition approved in 2002 as F 2174-02.2For referenced ASTM standards, visit the ASTM website, www.astm.org,
16、orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6 0.05-mm (0.031
17、 6 0.002-in.) diameter and 0.076 to 0.178mm (0.003 to 0.007 in.) deep at this reference mark point, torest the tip of the pencil lead to avoid slippage during the leadbreak process.4.2 Hsu-Nielsen Pencil Lead Break Source, 0.3 or 0.5 mm.A Nielsen shoe as described in Guide E 976 is optional.4.3 Sens
18、or(s), to be tested.4.4 Acoustic Emission Equipment, with amplitude measure-ment capability, for recording sensor response. (Operatingfamiliarity with the apparatus is assumed.)4.5 Couplant, to be standardized and documented by theuser of this practice.5. Procedure5.1 Ensure that the acrylic rod, se
19、nsors, and couplant havebeen allowed to stabilize to the ambient temperature of theexamination environment.5.2 Place the prepared acrylic rod horizontally on a suitablehard, flat surface (such as a bench top) with the 10.16-cm(4.0-in.) reference mark facing vertically up (12 oclock). Therod may be s
20、ecured with tape or other means no closer than 12in. from the reference mark.5.3 Prepare and power the AE measurement system includ-ing preamplifier (if used) and connecting cables. Allowwarm-up time as necessary. Verify the systems performance.Verification may be accomplished on the rod using a ref
21、erencesensor that is dedicated to this purpose and not exposed to thehazards of field use; or it may be accomplished by electronicprocedures such as those described in Practice E 750.5.4 Mount the sensor to be tested on the flat end of the rodusing the prescribed couplant and normal good application
22、techniques (refer to Guide E 650). Wipe off old couplant beforemounting and do not position so that it is resting on the samesurface supporting the acrylic rod. This will prevent slipping ofthe sensor during sensor verification. If the sensor is aside-connector type, have the connector pointing in t
23、he 3oclock direction as indicated in Fig. 1.5.5 Using the pencil lead source, break lead with the end ofthe 9.3-mm lead in the center of the reference mark, within 0.5mm (0.020 in.) with a lead extension of 2.5 6 0.5 mm (0.1 60.20 in.).ANielsen shoe may be used to obtain a consistent 30angle between
24、 the lead and the surface. Hold the pencilpointing toward the sensor but with its axis approximately 22(a quarter of a right angle) off from the axis of the rod, so thatthe lead flies off to one side and does not hit the sensor. Fingersmay be rested on the rod on the side away from the sensor tostea
25、dy the pencil, but there must be no finger contact or othermaterials in contact with the rod between the pencil and thesensor, except for the hard surface on which the acrylic rod isresting.5.6 Make three consistent lead breaks for each sensor,recording amplitude responses on a Sensor Performance Ve
26、ri-fication Form, similar to that shown in Fig. 2. Determine theaverage sensor amplitude response and proceed to the nextsensor. When complete, compile an average of all amplitudes.5.7 The acceptance criteria for each sensor shall be a valuethat does not deviate more than 62 dB from the averageampli
27、tude of the other sensors tested in the group. All sensorsthat fall outside this criteria shall be removed from service andrepaired or replaced. Use of sensors outside the averageamplitude of the group will compromise the validity of the AEtest results.6. Precision and Bias6.1 Temperature variations
28、 are known to affect the acousticabsorption properties of the acrylic rod. However, since this isa comparative technique rather than an absolute one, thispractice can be carried out with good results if all componentparts used in the practice have been allowed to stabilize to theexamination (environ
29、mental) temperature prior to application.6.2 Person-to-person variations can be reduced to a range of1 dB by proper technique and training.6.3 Variations in fracture performance within a lead andbetween leads are possible. With experience, occasional badbreaks can often be identified by the operator
30、, even withoutreference to the results of the measurement.6.4 Bad breaks are relatively common as the pencil is aboutto run out of lead.6.5 Uniformity of material is a major quality goal of the leadmanufacturer, but, even so, runs of bad lead can occur due tomanufacturing variations.7. Keywords7.1 a
31、crylic rod; calibration; sensorFIG. 1 Acrylic Rod DescriptionF 2174 02 (2008)2FIG. 2 Sensor Performance Verification FORMF 2174 02 (2008)3ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this st
32、andard are expressly advised that determination of the validity of any such patent 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 a
33、ndif not revised, either reapproved or withdrawn. Your comments are invited either 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,
34、 which you may attend. If you feel that your comments have not received a fair 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 standard 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).F 2174 02 (2008)4
