1、Designation: D 6874 03Standard Test Methods forNondestructive Evaluation of Wood-Based FlexuralMembers Using Transverse Vibration1This standard is issued under the fixed designation D 6874; the number immediately following the designation indicates the year oforiginal adoption or, in the case of rev
2、ision, the year 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.INTRODUCTIONNondestructive testing methods are used to determine the physical and mechanical properties ofwood
3、-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 evaluating the influence of environmental conditions on product performance.These test methods for tr
4、ansverse 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
5、 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 materials by nondestructive testing using transversevibration in the vertical direction.1.2 The
6、test methods are limited to specimens having solid,rectangular sections.1.3 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 t
7、he applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:D 9 Terminology Relating to Wood2D 198 Test Methods of Static Tests of Timbers in StructuralSizes2D 1990 Practice for Establishing Allowable Properties forVisually-Graded Dimension Lumber from In-Grade
8、 Testsof Full-Size Specimens2D 2915 Practice for Evaluating Allowable Properties forGrades of Structural Lumber2D 4442 Test Methods for Direct Moisture Content Measure-ment of Wood and Wood-Base Materials2D 4444 Test Methods for Use and Calibration of Hand-HeldMoisture Meters2D 4761 Test Methods for
9、 Mechanical Properties of Lumberand Wood-Base Structural Material2E 4 Practices for Force Verification of Testing Machines3E 1267 Guide for ASTM Standard Specification QualityStatements42.2 Other Standard:ISO 7626/1 Vibration and Shock-Experimental Determina-tion of Mechanical MobilityPart 1: Basic
10、Definitionsand Transducers53. Terminology3.1 DefinitionsSee Terminology D 9 and Test MethodsD 198.3.2 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, dete
11、rmined 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 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
12、this standard applies.3.2.3 standardizationthe determination of the response ofthe instrumentation to a reference material.1These test methods are under the jurisdiction of ASTM Committee D07 onWood and is the direct responsibility of Subcommittee D07.01 on Fundamental TestMethods and Properties.Cur
13、rent edition approved April 10, 2003. Published June 2003.2Annual Book of ASTM Standards, Vol 04.10.3Annual Book of ASTM Standards, Vol 03.01.4Discontinued 1996, see 1995 Annual Book of ASTM Standards, Vol 14.02.5Available from American National Standards Institute, 25 W. 43rd St., 4thFloor, New Yor
14、k, NY 10036.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.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 ex
15、citingits 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 bending mode. Observa-tions of frequency of oscillation are used to calculate modulusof elasticity.5. Significance and Use5.1 The dynamic mo
16、dulus of elasticity provided by thesetest methods is a fundamental property 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
17、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 indication of environmental or processing effect.5.2 The modulus of elasticity, whether measured staticallyor dynamically, is often a usef
18、ul predictor variable to suggestor explain property relationships.6. Apparatus6.1 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 e
19、nds 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 it and the reaction support. The reactions shallbe such that change in length of the specimen longitudinalmovement and rotation of the sp
20、ecimen 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 length of the specimen.If the bearing surfaces of the specimen at its reaction are notparallel to the bearing surface of the reactions, th
21、e 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 Lateral SupportNo lateral support shall be applied.Specimens unstable in this mode shall not be tested using thismethod.6.2.4 Lengthwise Posi
22、tioning and Overhang of theSpecimenThe specimen shall be positioned such that 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
23、 exacting analysis and equationsshall be used; see Ref (1).6NOTE 1In testing 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.
24、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 based onoscillation in this mode (Fig. 1).6.3.1 Manual MethodA manual deflection of the speci-men will provide sufficient impetus for oscil
25、lation for manyproducts. The deflection shall be vertical with an effort toexclude 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
26、a vertical oscillationof between 3 and 4 Hz.6.3.2 Mechanical MethodsThe guidelines of 6.3.1 shallbe duplicated with mechanical systems. Specimens with veryhigh stiffness require mechanical excitation by a high force orcarefully regulated impact/release.6.4 Measurement SystemMeasurement of the freque
27、ncyof oscillation shall be obtained by either a force or displace-ment measuring device calibrated to ensure accuracy in accor-dance with Practices E 4 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
28、 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 oscillation.6.4.3 Measurement of the Fundamental ModeIn these testmethods, it is critical that only the frequen
29、cy 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. Test Specimen7.1 Specimens shall be solid and rectangular. Deviations inshape and uniformity in dimension fro
30、m 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 RatioThe span-to-depth ratio usedshall be greater than 20 unless special precautions are taken topermit higher freque
31、ncy measurements.6The boldface numbers in parentheses refer to the list of references at the end ofthis standard.FIG. 1 Transverse Vibration in the Fundamental ModeD68740327.3 Moisture ContentMoisture content of specimens shallbe measured in accordance with Test Methods D 4442 orD 4444, or both. Spe
32、cific 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 D 4444 procedures to identify gradientscaused by drying or surf
33、ace 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 of Annex A1 shall be followed. Theresults of this test
34、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 standard static test results.8.2 ExcitationThe procedur
35、es 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 be taken during thetest sequence to allow calculation of
36、 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!2ws!3KdIg(1)where:Etv= transverse vibration modulus of e
37、lasticity, 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 mm/s2),andKd= constant for free vibration of a simply su
38、pportedbeam, 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 PracticeD 2915, Section 4.8.3.2.1 The presentation of results shall indicate whether thecalculations of E are based o
39、n 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 calculating apparent modulus of elasticity values. If, forexam
40、ple, 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 D 1990 and in Ref (2).8.3.2.3 Adjustments to dynamic E values for moisturecontent of specime
41、ns 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 elasticitymeasurement results in data of unknown comparability.9.2 Parti
42、cular 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, includingthe manufacturer of the device, the model, and
43、 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, ifnot reported as part of 9.3.1; the support surfaces;
44、 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 inthese factors over the data collection period.9.3.4 C
45、alibrationIdentify 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 standardization and for calibration shall be provided.9.3.5
46、 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 made to test datashall be fully explained, including actions taken to
47、meet thereporting requirements of Practice D 2915.10. Precision and Bias10.1 The precision and bias are dependent upon equipmentused (see Section 6) and the Standardization and Calibrationpractices applied.D6874033ANNEX(Mandatory Information)A1. STANDARDIZATION AND CALIBRATIONA1.1 StandardizationA1.
48、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
49、, by the manufacturer of the test system. The standardiza-tion test shall provide at least one reference point (output)within the operating range of interest. The standard referencematerial shall provide vibration performance within the rangeof vibration frequency of the test.A1.1.2 Typically, a metal bar had been employed as thereference material for standardization. Care shall be taken tocompensate for the effect of temperature variation on the metalproperties when standardization tests are repeated over theduration of the test program.NOTE A1.1Trad
