1、Designation: D6874 12Standard 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, in the case of revis
2、ion, 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.INTRODUCTIONNondestructive testing methods are used to determine the physical and mechanical properties ofwood-ba
3、sed 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 evaluating the influence of environmental conditions on product performance.These test methods for trans
4、verse vibration nondestructive testing of wood-based materials adoptmethods used by various testing and research organizations. These test methods will yield resultscomparable to traditional methods, permitting standardization of results, interchange and correlationof data, and establishment of a cu
5、mulative 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 (E) properties ofwood-based materials by nondestructive testing using trans-verse vibration in the vertical direction.1.2 Th
6、e 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 SI units that are provided for information onlyand are not considered standard.1.4 This st
7、andard 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 Documents2.1
8、 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 Dimension Lumber from In-Grade Testsof Full-Size SpecimensD2915 Practice for Sampling and Dat
9、a-Analysis for Struc-tural Wood and Wood-Based ProductsD4442 Test Methods for Direct Moisture Content Measure-ment of Wood and Wood-Base MaterialsD4761 Test Methods for Mechanical Properties of Lumberand Wood-Base Structural MaterialD7438 Practice for Field Calibration and Application ofHand-Held Mo
10、isture MetersE4 Practices for Force Verification of Testing MachinesE1267 Guide forAstm Standard Specification Quality State-ments (Withdrawn 1996)31These test methods are under the jurisdiction of ASTM Committee D07 onWood and is the direct responsibility of Subcommittee D07.01 on Fundamental TestM
11、ethods and Properties.Current edition approved Oct. 1, 2012. Published October 2012. Originallyapproved in 2003. Last previous edition approved in 2009 as D6874 03(20091).DOI: 10.1520/D6874-12.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at se
12、rviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken,
13、 PA 19428-2959. United States12.2 Other Standard:ISO 7626/1 Vibration and Shock-Experimental Determina-tion of Mechanical MobilityPart 1: Basic Definitionsand Transducers43. Terminology3.1 DefinitionsSee Terminology D9 and Test MethodsD198.3.2 Definitions of Terms Specific to This Standard:3.2.1 cal
14、ibrationthe 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 simplest mode ofvibration for a simply supported beam is the vertical motionproduced from a
15、 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 response ofthe instrumentation to a reference material.3.2.4 transverse vibrationthe oscil
16、lation 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 structural member is deflected at its mid-span andallowed to oscillate in a transverse be
17、nding 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 property for the configurationtested. This value can be related to static and other dynamicmodu
18、li 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 elasticity is often used forsurveys, for segregation of lumber for test purposes, and toprovide
19、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. Apparatus6.1 The testing equipment shall consist of three essentialelements:6.1.1 A support a
20、pparatus,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 be supported in amanner to prevent damage to the specimen at the point ofcontact between
21、 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 Reaction AlignmentProvision shall be made at thereactions to allow for initial twist in the
22、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 axisparallel to the span to provide adequate bearing across thewidth of the specimen.6.2.3 Lat
23、eral 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 that anequal portion of the length overhangs each support. Excessiveoverhang may alter re
24、sults obtained. If basic equation (Eq 1)isused, then the span (!) to length (!t) ratio shall exceed 0.98. Ifother !/!tratios are used, more exacting analysis and equationsshall be used; see Ref (1).5NOTE 1In testing of dimension lumber, an overhang of approximately1 in. on each end is often used.The
25、 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 oscillation in a reproducible manner in thefundamental mode. The method of analysis is b
26、ased 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 toexclude lateral components; neither excessive impact norprolonged contact with the spec
27、imen are recommended.NOTE 2For example, a manual tap on a 16-foot 2-by-12, supportedflat-wise having an E of 2.0 106psi will result in a vertical oscillationof between 3 and 4 Hz.6.3.2 Mechanical MethodsThe guidelines of 6.3.1 shall beduplicated with mechanical systems. Specimens with very highstiff
28、ness 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.ansi.org.5The boldface numbers in parentheses refer to a list of references at the end ofthis
29、standard.FIG. 1 Transverse Vibration in the Fundamental ModeD6874 1226.4 Measurement SystemMeasurement of the frequency ofoscillation shall be obtained by either a force or displacementmeasuring device calibrated to ensure accuracy in accordancewith Practices E4 and ISO 7626/1.6.4.1 Force Measuring
30、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 displacement in response to the initial displacementis an alternative method to determine frequency of
31、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 before acquiring the data to ensure the data acquired isonly related to the fundamental vertical mode.7
32、. 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 grade description, shall be noted as part of the sampleor specimen description.7.2 Span to Depth RatioT
33、he span-to-depth ratio used shallbe greater than 20 unless special precautions are taken topermit higher frequency measurements.7.3 Moisture ContentMoisture content (MC) of specimensshall be measured in accordance with Test Methods D4442 orD7438, or both. Specific reference to the current moisturest
34、atus of the specimens shall be made; for example,equilibrated, recently kiln dried containing gradients, air dried,packaged specimens of unknown drying history, and so forth.Identification of MC gradients caused by drying or surfacewetting is recommended. MC gradients within a piece mayaffect the dy
35、namic E (see X1.1.17).8. Procedure8.1 Standardization and CalibrationThe testing systemshall be standardized and calibrated using standard referencematerials. The procedures of Annex A1 shall be followed. Theresults of this test method are conditional upon proper stan-dardization and appropriate cho
36、ice 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 standard static test results.8.2 ExcitationThe procedures of excitation listed underSection 6 shall be followed. Repetitions a
37、re 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 be taken during thetest sequence to allow calculation of this contribution tomeasurement tolerances.8.3 Calculation of Modulus
38、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!2w !3KdIg(1)where:Etv= transverse vibration modulus of elasticity, psi (MPa),! = span, in. (mm),w = weight of specimen, lbf (N)
39、,fr= frequency of oscillation, Hz,I = specimen moment of inertia, bd3/12,b = breadth (width), in. (mm),d = depth, in. (mm),g = acceleration due to gravity, 386 in./s2(9807 mm/s2),andKd= constant for free vibration of a simply supported beam,2.47.8.3.2 Analysis and Presentation of ResultsAnalysis ofd
40、ata 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 shall indicate whether thecalculations of E are based on the actual, individual piece crosssection dimensions at the time of tes
41、t 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 calculating apparent modulus of elasticity values. If, forexample, the temperature varies during the test and affects theproperties of
42、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 Adjustments to dynamic E values for moisturecontent of specimens above 22 % MC shall be documented(see X1.1.21).9. Report9.1 The report
43、shall be sufficiently complete to permitreproduction of the test, including the calibration process.Inadequate explanation of the basis of the modulus of elasticitymeasurement results in data of unknown comparability.9.2 Particular attention shall be given to comprehensivereporting of the traceabili
44、ty of transducer calibrations tonationally acceptable references.9.3 The report shall contain at least the following elements:9.3.1 EquipmentDescription of the apparatus, includingthe manufacturer of the device, the model, and the calibrationsystem if incorporated in the manufactured device. If mech
45、ani-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, ifnot reported as part of 9.3.1; the support surfaces; and theprovisions employed for support of twisted or irregular sur-faces.
46、9.3.3 EnvironmentDescribe the temperatures during cali-bration and data collection and other factors in the operatingenvironment that may affect measurement. Note changes inthese factors over the data collection period.9.3.4 CalibrationIdentify whether the E was calculatedusing the fundamental formu
47、la (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 standardization and for calibration shall be provided.D6874 1239.3.5 Test DataPresent the test data in the units compa-rable to those
48、 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 made to test datashall be fully explained, including actions taken to meet thereporting requirements of Practice D2915.10. Precision an
49、d 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 subject to significant change under the test conditions.Reference materials are often recommended or provided, orboth, by the manufacture
