1、Designation: D4761 11Standard Test Methods forMechanical Properties of Lumber and Wood-Base StructuralMaterial1This standard is issued under the fixed designation D4761; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of l
2、ast revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.INTRODUCTIONNumerous evaluations of the mechanical properties of wood-based structural material have beensatisfactorily conducted s
3、ince the late 1920s, using Test Methods D198. Those methods are best suitedto a laboratory environment and are adaptable to a variety of products such as stress-graded lumber,sawn timber, laminated timbers, wood-plywood composite members, reinforced and prestressedtimbers.The procedures presented in
4、 these test methods have been derived from those set forth in TestMethods D198. They are intended primarily for application to stress-graded lumber, but can be usedfor other wood-base structural material as well. The procedures are more flexible than those in TestMethods D198, making testing in a no
5、nlaboratory environment more feasible. Thus the test methodscan be used on production sites for field testing and quality control, as well as in laboratories forresearch applications. Key differences from Test Methods D198 are the testing speed, the deflection-measuring procedures for test specimens
6、 under load, and the detail of data reporting. Furthermore, thetest methods do not require that specimens be loaded to failure.Since these test methods allow latitude in testing procedures, the procedures used shall be fullydocumented in the test report. It may also be desirable to correlate the res
7、ults from tests carried outaccording to these test methods with test results obtained through the use of a traditional procedure,such as that set forth in Test Methods D198.1. Scope1.1 These test methods cover the determination of themechanical properties of stress-graded lumber and other wood-base
8、structural material.1.2 These test methods appear in the following order:SectionBending edge-wise 6Bending flat-wise:Center point loading 7Third point loading 8Axial strength in tension 9Axial strength in compression 101.3 This standard does not purport to address all of thesafety concerns, if any,
9、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 ASTM Standards:2D9 Terminology Relating to Wood and Wood-Based Prod-u
10、ctsD198 Test Methods of Static Tests of Lumber in StructuralSizesD2915 Practice for Sampling and Data-Analysis for Struc-tural Wood and Wood-Based ProductsD4442 Test Methods for Direct Moisture Content Measure-ment of Wood and Wood-Base MaterialsD7438 Practice for Field Calibration and Application o
11、fHand-Held Moisture MetersE4 Practices for Force Verification of Testing Machines1These test methods are under the jurisdiction of ASTM Committee D07 onWood and are the direct responsibility of Subcommittee D07.01 on FundamentalTest Methods and Properties.Current edition approved July 15, 2011. Publ
12、ished September 2011. Originallyapproved in 1988. Last previous edition approved in 2005 as D4761 05. DOI:10.1520/D4761-11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, re
13、fer 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.E6 Terminology Relating to Methods of Mechanical TestingE177 Practice for Use of the Terms Precision and Bias inASTM Test M
14、ethods2.2 Other Document:3NIST Voluntary Product Standard PS20 American Soft-wood Lumber StandardNOTE 1The current version of PS20 is given as an example of aproduct standard applicable to stress-graded lumber. Other product stan-dards may apply to stress-graded lumber. For wood-base structuralmater
15、ials other than stress-graded lumber, relevant product standards mayapply.3. Terminology3.1 DefinitionsSee Terminologies D9 and E6 and Prac-tices E4 and E177 for definitions of terms used in these testmethods.3.2 Definitions of Terms Specific to This Standard:3.2.1 breadththat dimension of the test
16、specimen in thedirection perpendicular to the span and perpendicular to thedirection of an applied bending load.3.2.2 depththat dimension of the test specimen in thedirection perpendicular to the span and parallel to the directionof an applied bending load.3.2.3 spanthe distance between the center l
17、ines of thepivot points upon which the test specimen is supported toaccommodate a transverse bending load or, for tension loading,the distance between the grips.4. Significance and Use4.1 These test methods provide procedures that are appli-cable under true field conditions, such as in a plant withs
18、pecimens not at moisture equilibrium.4.2 The data established by these test methods can be usedas follows:4.2.1 Develop strength and stiffness properties for the popu-lation represented by the material being tested (that is, indi-vidual grades, grade combinations, species, species groups, orany othe
19、r defined, identifiable sample).4.2.2 Confirm the validity of strength and stiffness proper-ties for the population represented by the material being tested.4.2.3 Investigate the effect of parameters that may influencethe strength and stiffness properties of the material, such asmoisture content, te
20、mperature, knot size and location, or slopeof grain.4.3 The procedures chosen in accordance with these testmethods shall be fully documented in the report to facilitatecorrelation with test results obtained through the use oftraditional procedures, such as those set forth in Test MethodsD198.5. Prec
21、ision and Bias5.1 The precision and bias of these test methods have notyet been established.6. BENDING EDGE-WISE6.1 Scope6.1.1 This test method provides procedures for the determi-nation of the strength and modulus of elasticity of stress-gradedlumber and other wood-base structural material in bendi
22、ngedge-wise.6.2 Summary of Test Methods6.2.1 The test specimen is simply supported and loaded bytwo concentrated forces spaced equidistant from the supports.The specimen is loaded at a prescribed rate and, as applicable,observation of load or deflection, or both, is made until failureoccurs or a pre
23、selected load is reached.6.3 Apparatus6.3.1 Testing MachineA device that combines (1) a reac-tion frame to support the test specimen, (2) a loading mecha-nism for applying load at a specified rate, and (3) a force-measuring apparatus that can be calibrated to the accuracyrequirements of 6.3.3.2 foll
24、owing the procedures outlined inPractices E4.6.3.1.1 Load and Support Apparatus, including bearingplates at least as wide as the specimen is broad and notexceeding the member depth in length. The bearing plates shallhave eased edges and sufficient bearing lengths to avoid alocalized crushing failure
25、 at the load and support points. Theapparatus shall also include appropriate mechanisms, such asrollers or pivots, to minimize the development of axial forcesin the test specimen. Each bearing point shall include anin-plane pivot point. Bearing plates and rollers shall be initiallycentered about the
26、ir pivot points.6.3.1.2 Loading ConfigurationThe simply supported testspecimen shall be subjected to two equal transverse concen-trated loads spaced equidistant from the supports.NOTE 2The apparent modulus of elasticity varies for different loadingconfigurations (see Practice D2915). While the loadi
27、ng configuration thatcommonly serves as the basis for assigning design values assumes auniformly distributed load, a configuration with two concentrated loadssymmetrically placed within the test span usually is more suitable forstructural tests. This configuration also produces a constant bendingmom
28、ent, free of shear, in the portion of the specimen between the loadpoints.6.3.1.3 Lateral Supports, when necessary, to restrict thespecimen lateral deflection. Specimens having a depth-to-breadth ratio of three or greater are subject to lateral instabilityduring loading and may require lateral suppo
29、rts. These sup-ports shall allow movement of the specimen in the direction ofload application and have minimal frictional restraint.6.3.2 Deflection-Measuring Apparatus, for modulus of elas-ticity calculations, to monitor the deflection of the test speci-men. Deflection may be measured directly as t
30、he displacementof the loading head of the testing machine. In this case,deflection is expressed as the average deflection of the loadpoints with respect to the end reaction plates. If, because of thedesign of the apparatus, the deflection measurement includesextraneous components, the deflection dat
31、a may be adjusted forsuch extraneous components (Note 3). In all instances, thereport shall include a complete description of test conditions,extraneous components, and data adjustment procedures.NOTE 3If the extraneous components are an appreciable portion ofthe total measurement, the test apparatu
32、s should be reexamined for itssuitability.3Available from National Institute of Standards and Technology (NIST), 100Bureau Dr., Stop 3460, Gaithersburg, MD 20899-3460.D4761 1126.3.3 Accuracy:6.3.3.1 The two load points shall be located within18 in. (3mm) of the distance determined in accordance with
33、 6.3.1.2 and6.4.2.2.6.3.3.2 The force-measuring apparatus shall be such as topermit load measurements with an error not to exceed 61.0 %of the load for loads greater than or equal to 1000 lbf (4450 N).For loads smaller than 1000 lbf, the error shall not exceed 610lbf (45 N).6.3.3.3 The deflection-me
34、asuring apparatus shall be such asto permit deflection measurements with an error not to exceed62.0 % of the deflection for deflections greater than or equal to0.150 in. (4 mm). For deflections smaller than 0.150 in., theerror shall not exceed 60.003 in. (0.08 mm).6.4 Test Specimen6.4.1 Cross Sectio
35、nUnless the effect of cross-sectionmodifications is a test evaluation objective, test the specimenwithout modifying the dimensions of the commercial crosssection.6.4.2 Length:6.4.2.1 The minimum specimen length shall be the span,determined in accordance with 6.4.2.2, plus an extensionbeyond the cent
36、er lines of the end reactions to accommodatethe bearing plates, such that the specimen will not slip off theend reactions during the test. In cases where the unsupportedspecimen length outside the test span at an end reaction(overhang) exceeds 10 times the specimen depth, report theamount of overhan
37、g at each end reaction.6.4.2.2 The span will depend on the purpose of the testprogram. It is customary to express the span as a multiple ofthe test specimen depth (Note 4). While spans that currentlyserve as a basis suitable for testing range from 17 times thedepth of the specimen to 21 times the de
38、pth, other spans maybe used under this test method. Practice D2915 gives anindication of the variation of the apparent modulus of elasticitywith span-to-depth ratios.NOTE 4The depth here refers to the relevant size specified in the sizeclassification of the applicable product standard (for stress-gr
39、aded lumber,for example, the depth here may refer to the dressed dry size specified inthe size classification of the current version of PS20 for the nominal size,for example, 3.5 in. (89 mm) for a nominal 4 in.).6.4.3 ConditioningSpecimens may be tested as producedor conditioned (for example, temper
40、ature, moisture content, ortreatment), depending on the purpose of the test program. If thetemperature of the specimens at the time of testing is less than45F (7C) or more than 90F (32C), report that temperature.6.5 Procedure6.5.1 Specimen Measurements:6.5.1.1 Before testing, measure and record the
41、cross-sectional dimensions of every specimen to the nearest 0.04 in.(1 mm). Make measurements at midlength of the specimenunless another location is more appropriate to the purpose ofthe test.6.5.1.2 Following the test, measure the moisture content ofevery specimen in the vicinity of the failure zon
42、e in accordancewith the procedures outlined in Test Methods D4442 orPractice D7438.6.5.2 Test Setup:6.5.2.1 Lengthwise PositioningIf the specimen is to belocated within the test span without bias regarding defects,achieve this by centering the specimen in the span or by anyother scheme suitable to t
43、he purpose of the test program.6.5.2.2 Selection of the Tension EdgeRandomly select theedge to be subjected to tension testing.6.5.3 Speed of TestingThe test rate shall be such that thesample target failure load would be achieved in approximately1 min (Note 5). The failure load should not be reached
44、 in lessthan 10 s nor more than 10 min (Note 6).NOTE 5Some caution is warranted here. A test rate to achieve theaverage failure load for the sample in approximately 1 min will differ fromthat to achieve a lower percentile load for the same sample in approxi-mately 1 min.NOTE 6For stress-graded lumbe
45、r, a rate of motion of the testingmachine loading head of approximately 3 in. (75 mm)/min will usuallypermit the test to be completed in the prescribed time for span to depthratios of 17:1 and in cases where the target failure load is the averagefailure load for the sample.6.5.4 Load-Deflection Data
46、Obtain load-deflection data,as required, using the apparatus specified in 6.3.2.NOTE 7For stress-graded lumber, data obtained for loads correspond-ing to maximum stresses in the specimen ranging from 400 to 1000 psi(2.75 to 7 MPa) will usually be adequate for modulus of elasticitycalculations.6.5.5
47、Maximum LoadIf the purpose of the test is todetermine strength properties, record the maximum load at-tained in the test.NOTE 8In proof loading, the intended load target may not be reachedor may be exceeded slightly. The actual attained load as well as the targetload should therefore be recorded.6.5
48、.6 Record of FailureDepending on the purpose of thetest, a description of the characteristic causing failure, and itslocation within the test span, may be required.NOTE 9An example of a coding scheme for recording characteristictype and failure location is given in Appendix X1. This example wasderiv
49、ed for application to stress-graded lumber.6.6 Report6.6.1 The report content depends on the purpose of the testprogram. The report shall include, at the minimum, thefollowing information:6.6.1.1 Description of the testing machine, including de-tailed drawings, the span, and the deflection-measuring appa-ratus, if applicable.6.6.1.2 Description of calibration procedures, frequency,and records.6.6.1.3 Method used for the measurement of the moisturecontent of specimens.6.6.1.4 Speed of testing and means of control of the speed oftesting.6.6.1.5 Specimens le
