1、Designation: F 2174 02An 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 revision, the yea
2、r of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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. It is intended
3、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 The values stated
4、 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 thisprocedure.1.5 This s
5、tandard 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. Referenced Documents2.
6、1 ASTM Standards:E 650 Guide for Mounting Piezoelectric Acoustic EmissionSensors2E 750 Practice for Characterizing Acoustic Emission Instru-mentation2E 976 Guide for Determining the Reproducibility of Acous-tic Emission Sensor Response23. Significance and Use3.1 Degradation in sensor performance can
7、 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 test blocks of ma
8、ny 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 depend on temperat
9、ure, 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 environment overnigh
10、t, 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-riskconditions su
11、ch 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 aperformance check.4
12、. 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 surface finish of 0.
13、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 distance of 10.16 c
14、m (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, 0.796 0.05-mm (0.031 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
15、 slippage during the leadbreak process.1This practice is under the jurisdiction of ASTM Committee F18 on ElectricalProtective Equipment for Workers and is the direct responsibility of SubcommitteeF18.55 on Acoustic Emission.Current edition approved March 10, 2002. Published May 2002.2Annual Book of
16、ASTM Standards, Vol 03.03.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.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 Sensor(s), to be tested.4.4 Acoustic Emissio
17、n 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, sensors, and couplant havebeen allowed to
18、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 secured with tape or other means no close
19、r 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 referencesensor that is dedicated to this p
20、urpose 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 applicationtechniques (refer to Guide E 650). Wipe
21、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 the 3oclock direction as indicated in Fig
22、. 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.). A Nielsen shoe may be used to obtain a consistent 30angle between the lead and the surface. Hold the pe
23、ncilpointing 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 tosteady the pencil, but there must be no fi
24、nger 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 Veri-fication Form, similar to that show
25、n 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 averageamplitude of the other sensors tested in th
26、e 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 are known to affect the acousticabsor
27、ption 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 (environmental) temperature prior to applicati
28、on.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, even withoutreference to the results
29、 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 acrylic rod; calibration; sensorFIG. 1
30、Acrylic Rod DescriptionF2174022FIG. 2 Sensor Performance Verification FORMF2174023ASTM 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 v
31、alidity 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 andif not revised, either reapproved or withdrawn. Your c
32、omments 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, which you may attend. If you feel that your comments ha
33、ve 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).F2174024
