1、Designation: D6874 03 (Reapproved 2009)1Standard Test Methods forNondestructive Evaluation of Wood-Based FlexuralMembers Using Transverse Vibration1This standard is issued under the fixed designation D6874; the number immediately following the designation indicates the year oforiginal adoption or, i
2、n the case of 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.1NOTEA units of measurement statement was editorially added in December 2009.INTRODUCTIONNonde
3、structive testing methods are used to determine the physical and mechanical properties ofwood-based materials. These test methods help ensure structural performance of products manufac-tured from a variety of wood species and quality levels of raw materials. These test methods also assistin evaluati
4、ng the influence of environmental conditions on product performance.These test methods for transverse vibration nondestructive testing of wood-based materials adoptmethods used by various testing and research organizations. These test methods will yield resultscomparable to traditional methods, perm
5、itting standardization of results, interchange and correlationof data, and establishment of a cumulative body of information on wood species and products of theworld.1. Scope1.1 These test methods cover the determination of theflexural stiffness and modulus of elasticity properties of wood-based mat
6、erials by nondestructive testing using transversevibration in the vertical direction.1.2 The test methods are limited to specimens having solid,rectangular sections.1.3 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to
7、 SI units that are provided for information onlyand are not considered standard.1.4 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 det
8、ermine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D9 Terminology Relating to Wood and Wood-Based Prod-uctsD198 Test Methods of Static Tests of Lumber in StructuralSizesD1990 Practice for Establishing Allowable Properties forVisually-Graded Di
9、mension Lumber from In-Grade Testsof Full-Size SpecimensD2915 Practice for Evaluating Allowable Properties forGrades of Structural LumberD4442 Test Methods for Direct Moisture Content Measure-ment of Wood and Wood-Base MaterialsD4444 Test Method for Laboratory Standardization andCalibration of Hand-
10、Held Moisture MetersD4761 Test Methods for Mechanical Properties of Lumberand Wood-Base Structural MaterialE4 Practices for Force Verification of Testing MachinesE1267 Guide for ASTM Standard Specification QualityStatements31These test methods are under the jurisdiction of ASTM Committee D07 onWood
11、and is the direct responsibility of Subcommittee D07.01 on Fundamental TestMethods and Properties.Current edition approved Dec. 1, 2009. Published December 2009. Originallyapproved in 2003. Last previous edition approved in 2003 as D6874 03. DOI:10.1520/D6874-03R09E01.2For referenced ASTM standards,
12、 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.3Withdrawn. The last approved version of this historical standard is referencedon www.astm.o
13、rg.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.2.2 Other Standard:ISO 7626/1 Vibration and Shock-Experimental Determina-tion of Mechanical MobilityPart 1: Basic Definitionsand Transducers43. Terminology3.1 DefinitionsSee Terminol
14、ogy D9 and Test MethodsD198.3.2 Definitions of Terms Specific to This Standard:3.2.1 calibrationthe determination of the relationship be-tween the response of standardized instrumentation to proper-ties of reference material, determined by a standard method.3.2.2 fundamental mode of vibrationthe sim
15、plest mode ofvibration for a simply supported beam is the vertical motionproduced from a slight vertical displacement of the member atits mid-span. This is termed its fundamental mode of vibration(Fig. 1) and is the mode to which this standard applies.3.2.3 standardizationthe determination of the re
16、sponse ofthe instrumentation to a reference material.3.2.4 transverse vibrationthe oscillation of a simply sup-ported bending member that results from an initial displace-ment of the member at its mid-span or other means of excitingits fundamental mode of vibration.4. Summary of Test Method4.1 The s
17、tructural member is deflected at its mid-span andallowed to oscillate in a transverse bending mode. Observa-tions of frequency of oscillation are used to calculate modulusof elasticity.5. Significance and Use5.1 The dynamic modulus of elasticity provided by thesetest methods is a fundamental propert
18、y for the configurationtested. This value can be related to static and other dynamicmoduli of elasticity as measured on the same configuration.5.1.1 The rapidity and ease of application of these testmethods facilitate its use as a substitute for static measure-ments.5.1.2 Dynamic modulus of elastici
19、ty is often used forsurveys, for segregation of lumber for test purposes, and toprovide indication of environmental or processing effect.5.2 The modulus of elasticity, whether measured staticallyor dynamically, is often a useful predictor variable to suggestor explain property relationships.6. Appar
20、atus6.1 The testing equipment shall consist of three essentialelements:6.1.1 A support apparatus,6.1.2 An excitation system, and6.1.3 A measurement system.6.2 Support ApparatusThe support shall provide verticalsupport to the ends of the specimen yet permit rotation.6.2.1 ReactionsThe specimen shall
21、be supported in amanner to prevent damage to the specimen at the point ofcontact between it and the reaction support. The reactions shallbe such that change in length of the specimen longitudinalmovement and rotation of the specimen about the reaction dueto deflection will be unrestricted.6.2.2 Reac
22、tion AlignmentProvision shall be made at thereactions to allow for initial twist in the length of the specimen.If the bearing surfaces of the specimen at its reaction are notparallel to the bearing surface of the reactions, the specimenshall be shimmed or the bearing surfaces rotated about an axispa
23、rallel to the span to provide adequate bearing across thewidth of the specimen.6.2.3 Lateral SupportNo lateral support shall be applied.Specimens unstable in this mode shall not be tested using thismethod.6.2.4 Lengthwise Positioning and Overhang of theSpecimenThe specimen shall be positioned such t
24、hat anequal portion of the length overhangs each support. Excessiveoverhang may alter results obtained. If basic equation (Eq 1) isused, then the span(s) to length (L) ratio shall exceed 0.98. Ifother s/L ratios are used, more exacting analysis and equationsshall be used; see Ref (1).5NOTE 1In testi
25、ng of dimension lumber, an overhang of approximately1 in. on each end is often used. The amount of overhang may be influencedby the convenience of handling and positioning but should be keptuniform from specimen to specimen.6.3 Excitation SystemThe member shall be excited so asto produce a vertical
26、oscillation in a reproducible manner in thefundamental mode. The method of analysis is based onoscillation in this mode (Fig. 1).6.3.1 Manual MethodA manual deflection of the speci-men will provide sufficient impetus for oscillation for manyproducts. The deflection shall be vertical with an effort t
27、oexclude lateral components; neither excessive impact norprolonged contact with the specimen are recommended.NOTE 2For example, a manual tap on a 16-foot 2-by-12, supportedflat-wise having a MOE of 2.0 3 106psi will result in a vertical oscillationof between 3 and 4 Hz.6.3.2 Mechanical MethodsThe gu
28、idelines of 6.3.1 shallbe duplicated with mechanical systems. Specimens with veryhigh stiffness require mechanical excitation by a high force orcarefully regulated impact/release.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ans
29、i.org.5The boldface numbers in parentheses refer to a list of references at the end ofthis standard.FIG. 1 Transverse Vibration in the Fundamental ModeD6874 03 (2009)126.4 Measurement SystemMeasurement of the frequencyof oscillation shall be obtained by either a force or displace-ment measuring devi
30、ce calibrated to ensure accuracy in accor-dance with Practices E4 and ISO 7626/1.6.4.1 Force Measuring SystemChanges in the force inresponse to the vibration at one or both of the supports aremethods used to obtain frequency of oscillation.6.4.2 Deflection Measuring SystemMeasurement of themid-span
31、displacement in response to the initial displacementis an alternative method to determine frequency of oscillation.6.4.3 Measurement of the Fundamental ModeIn these testmethods, it is critical that only the frequency associated withthe fundamental vertical oscillation mode be used. Use a shortdelay
32、before acquiring the data to ensure the data acquired isonly related to the fundamental vertical mode.7. Test Specimen7.1 Specimens shall be solid and rectangular. Deviations inshape and uniformity in dimension from end-to-end andside-to-side incidental to sampling, such as wane included in alumber
33、grade description, shall be noted as part of the sampleor specimen description.7.2 Span to Depth RatioThe span-to-depth ratio usedshall be greater than 20 unless special precautions are taken topermit higher frequency measurements.7.3 Moisture ContentMoisture content of specimens shallbe measured in
34、 accordance with Test Methods D4442 orD4444, or both. Specific reference to the current moisturestatus of the specimens shall be made; for example, equili-brated, recently kiln dried containing gradients, air dried,packaged specimens of unknown drying history, and so forth.Use of Test Methods D4444
35、procedures to identify gradientscaused by drying or surface wetting is recommended. MCgradients within a piece may affect the dynamic E (seeX1.1.17).8. Procedure8.1 Standardization and CalibrationThe testing systemshall be standardized and calibrated using standard referencematerials. The procedures
36、 of Annex A1 shall be followed. Theresults of this test method are conditional upon proper stan-dardization and appropriate choice of calibration method.NOTE 3It has been a practice to use aluminum bars as well as lumberspecimens as standardization materials and, often, also for calibrationagainst a
37、 standard static test results.8.2 ExcitationThe procedures of excitation listed underSection 6 shall be followed. Repetitions are recommended toreduce the chance of bias caused by improper excitation.8.2.1 To quantify measurement uncertainty for precisionand bias estimates, specific data sets shall
38、be taken during thetest sequence to allow calculation of this contribution tomeasurement tolerances.8.3 Calculation of Modulus of Elasticity:8.3.1 Basic EquationThe following formula shall be usedto calculate modulus of elasticity from the measured oscillationin the fundamental mode (Fig. 1):Etv5fr!
39、2ws!3KdIg(1)where:Etv= transverse vibration modulus of elasticity, psi (MPa),s = span, in. (mm),w = weight of specimen, lbf (N),fr= frequency of oscillation, Hz,I = specimen moment of inertia, bh3/12,b = breadth (width), in. (mm),h = height, in. (mm),g = acceleration due to gravity, 386 in./s2(9807
40、mm/s2),andKd= constant for free vibration of a simply supportedbeam, 2.47.8.3.2 Analysis and Presentation of ResultsAnalysis ofdata collected from samples and the presentations of resultsshall be consistent with the appropriate methods of PracticeD2915, Section 4.8.3.2.1 The presentation of results
41、shall indicate whether thecalculations of E are based on the actual, individual piece crosssection dimensions at the time of test or on standard (designbase) dimensions.8.3.2.2 Environmental ConditionsSensitivity of the testspecimens to changes in the test environment shall be consid-ered in calcula
42、ting apparent modulus of elasticity values. If, forexample, the temperature varies during the test and affects theproperties of the test material, this shall be considered inpresentation of test results.Appropriate adjustments for lumberare included in Practice D1990 and in Ref (2).8.3.2.3 Adjustmen
43、ts to dynamic E values for moisturecontent of specimens above 22 % MC shall be documented(see X1.1.21).9. Report9.1 The report shall be sufficiently complete to permitreproduction of the test, including the calibration process.Inadequate explanation of the basis of the modulus of elasticitymeasureme
44、nt results in data of unknown comparability.9.2 Particular attention shall be given to comprehensivereporting of the traceability of transducer calibrations tonationally acceptable references.9.3 The report shall contain at least the following elements:9.3.1 EquipmentDescription of the apparatus, in
45、cludingthe manufacturer of the device, the model, and the calibrationsystem if incorporated in the manufactured device. If mechani-cal excitation is employed, the mechanism shall be describedalong with the method of assuring adequate excitation.9.3.2 Test SetupDescription of the specimen supports, i
46、fnot reported as part of 9.3.1; the support surfaces; and theprovisions employed for support of twisted or irregular sur-faces.9.3.3 EnvironmentDescribe the temperatures during cali-bration and data collection and other factors in the operatingenvironment that may affect measurement. Note changes in
47、these factors over the data collection period.9.3.4 CalibrationIdentify whether the E was calculatedusing the fundamental formula (Eq 1) or the adjusted formula(see A1.2.4). If the latter was used, describe the source of thefactors ksand z. A comprehensive description of the materialsused for standa
48、rdization and for calibration shall be provided.D6874 03 (2009)139.3.5 Test DataPresent the test data in the units compa-rable to those employed in 7.1. The data presentation shallinclude an estimate of the precision and bias of the data andmethod of estimation.9.3.6 Data AdjustmentsAll adjustments
49、made to test datashall be fully explained, including actions taken to meet thereporting requirements of Practice D2915.10. Precision and Bias10.1 The precision and bias are dependent upon equipmentused (see Section 6) and the Standardization and Calibrationpractices applied.ANNEX(Mandatory Information)A1. STANDARDIZATION AND CALIBRATIONA1.1 StandardizationA1.1.1 Standardization shall be performed on the dynamictest apparatus to verify the integrity of the system. Suitablereference materials for standardization have properties that arenot s
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