ASTM D4761-2005 Standard Test Methods for Mechanical Properties of Lumber and Wood-Base Structural Material《木材及木基结构材料机械性能的标准试验方法》.pdf

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1、Designation: D 4761 05Standard Test Methods forMechanical Properties of Lumber and Wood-Base StructuralMaterial1This standard is issued under the fixed designation D 4761; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of

2、 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.INTRODUCTIONNumerous evaluations of the mechanical properties of wood-based structural material have beensatisfactorily conducte

3、d since the late 1920s, usingTest Methods D 198.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

4、in these test methods have been derived from those set forth in TestMethods D 198. 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 D 198, making testing in

5、a nonlaboratory 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 D 198 are the testing speed, thedeflection-measuring procedures for test speci

6、mens under load, and the detail of data reporting.Furthermore, the test methods do not require that specimens be loaded to failure (Note 1).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 corr

7、elate the results 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 D 198.1. ScopeNOTE 1A proof load may be used, which will permit the determina-tion of a specified strength percentile w

8、ithout testing the total sample todestruction. Designing a test program on the basis of proof loading can becomplex, requiring consideration in relation to the objectives of the testprogram. Guidance on this matter can be found in the paper by Johnson.21.1 These test methods cover the determination

9、of themechanical properties of stress-graded lumber and other wood-base structural material.1.2 These test methods appear in the following order:SectionBending edge-wise 6-11Bending flat-wise:Center point loading 12-17Third point loading 18-23Axial strength in tension 24-29Axial strength in compress

10、ion 30-351.3 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 the applica-bility of regulatory limitations prior to use.2. Ref

11、erenced Documents2.1 ASTM Standards:3D9 Terminology Relating to WoodD 198 Test Methods of Static Tests of Lumber in StructuralSizesD 2915 Practice for Evaluating Allowable Properties forGrades of Structural LumberD 4442 Test Methods for Direct Moisture Content Measure-ment of Wood and Wood-Base Mate

12、rialsE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical Test-ing1These test methods are under the jurisdiction of ASTM Committee D07 onWood and are the direct responsibility of Subcommittee D07.01 on FundamentalTest Methods (2) a loading mecha-nis

13、m for applying load at a specified rate or prescribed loadinterval; and (3) a force-measuring apparatus that can becalibrated to the accuracy requirements of 8.3.2, following theprocedures outlined in Practices E4. If the test is for modulusof elasticity only, no force-measuring device is required.

14、Fig. 1illustrates the traditional device meeting the requirements ofthese test methods for modulus of elasticity measurement.20.1.1 Load and Support Apparatus, including bearingplates at least as wide as the specimen is broad. It isrecommended that the bearing plate length be no less than onehalf th

15、e specimen depth. If only the modulus of elasticity is tobe determined in accordance with 19.2, the bearing platerequirement may be waived. The apparatus shall also includeappropriate mechanisms such as rollers or pivots to minimizethe development of axial forces in the test specimen.20.1.2 Loading

16、ConfigurationThe simply supported testspecimen shall be subjected to two equal, concentrated loadsspaced equidistant between the supports. (See Note 3).20.1.3 If an incremental load system is used for modulus ofelasticity, the pre-load shall be sufficient to force the specimeninto contact with the s

17、upports, firmly seat moveable parts, andproduce sufficient deflection to permit establishing the base forthe incremental measurement. The known incremental loadshall be of sufficient magnitude to produce deflection greaterthan 0.050 in.NOTE 12In North American practice, these incremental loads arese

18、lected to give deflections ranging from 0.070 in. (1.8 mm) to 0.210 in.(5.3 mm), with a minus tolerance of approximately 10 %, at respective Elevels of 1.0 and 3.0 3 106psi (6.9 GPa and 21 GPa) for dimension sizesranging from 2 by 3 to 2 by 10 (38 by 63 to 38 by 235 mm).20.1.4 Deflections in the sup

19、port system shall be measuredto determine that either they are negligible or that calibration ofthe system can compensate for the deflections. (See also 20.2).NOTE 13As the span/depth ratio decreases, the magnitude of theapplied load must be increased to produce deflections in the range requiredby 2

20、0.1.3. Stability of the applied load is a safety consideration in designof the apparatus. For high loads, the applied loads may need to be hungrather than supported as shown in Fig. 1. These higher loads may alsoincrease deflections in the support apparatus.20.2 Deflection-Measuring Apparatus, for m

21、odulus of elas-ticity calculations, to monitor the deflection of the test speci-men. Deflection may be measured directly as the 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 reactions.

22、If, because of thedesign of the apparatus, the deflection measurement includesextraneous components, the deflection data may be adjusted forsuch extraneous components (Note 4). In all instances, thereport shall include a complete description of test conditions,extraneous components, and data adjustm

23、ent procedures.20.2.1 If an incremental load is applied for determination ofmodulus of elasticity, the deflection-measuring device shall besuitable for measuring the deflection caused by the incrementalload.20.3 Accuracy:20.3.1 The two load points shall be located within18 in. (3mm) of the distance

24、determined in accordance with 20.1.2 and21.2.2.20.3.2 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)

25、.20.3.2.1 For modulus of elasticity based on incrementalloads, these loads shall be calibrated to within 61 % of thestipulated value.20.3.3 The deflection-measuring apparatus shall be such asto permit deflection measurements with an error not to exceed62.0 % of the deflection for deflections greater

26、 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).21. Test Specimen21.1 Cross SectionUnless the effect of cross-sectionmodifications is a test evaluation objective, test the specimenwithout modifying the dimensions of the commer

27、cial crosssection.21.2 Length:21.2.1 The minimum specimen test length shall be the span,determined in accordance with 9.2, plus an extension beyondthe center lines of the end reactions to accommodate thebearing plates, such that the specimen will not slip off the endreactions during the test.21.2.2

28、Because this is a short-span test, the length of thespecimen will often exceed the test length of 21.2.1.Asampling procedure shall specify where, along the specimenlength, the test length shall be positioned.21.2.2.1 The standard span for this test is 32 times the depthfor nominal 2 in. (38 mm) lumb

29、er. Other spans/depth ratios are16 in. = 410 mm48 in. = 1220 mmNOTE 1This device is used for assessment of E in third-point,flat-wise bending on a span-to-depth ratio of 32 for 112-in. (38-mm) thicklumber.FIG. 1 Schematic of Static Bending Testing DeviceD4761055permissible but load levels and within

30、-piece sampling methodsshall be carefully documented, noting changes from the tradi-tional span/depth ratio.21.3 ConditioningSpecimens may be tested as producedor as conditioned (for example, temperature, moisture content,or treatment), depending on the purpose of the test program. Ifthe temperature

31、 of the specimens at the time of testing is lessthan 45F (7C) or more than 90F (32C), report thattemperature.22. Procedure22.1 Specimen MeasurementThe procedures of 10.1 shallbe followed.22.2 Test Setup:22.2.1 Lengthwise PositioningThe objective may be tolocate the test span within the total length

32、without biasregarding defects, or it may be to locate the test span atlocations predetermined by specified criteria. This positioningshall be achieved by a within-piece sampling plan that specifiesthe method of locating the test area (see 21.2.2). The procedureshall be documented (see Section 23).22

33、.2.1.1 If this method is being used to determine specimenstrength, after the test location is determined, the specimenlength shall be adjusted if necessary to provide equal extensionover both test supports (prevent unequal overhang).22.2.1.2 If this method is being used for modulus ofelasticity only

34、, unequal extension beyond the supports ispermitted. A weight may be placed directly over a support tostabilize the specimen where a long extension (overhang) ispresent.22.3 Rate of Load Application:22.3.1 Strength and Modulus of Elasticity by ContinuousLoadingThe practices of 10.3 shall be followed

35、.22.3.2 Modulus of Elasticity by Incremental TestIf theincremental loading method is used, a pre-load shall beapplied, followed by the incremental load. Loads shall beapplied and deflections recorded rapidly to prevent the influ-ence of creep.NOTE 14It is common North American practice to complete t

36、hepre-load, deflection zero, prescribed load application, and the incrementaldeflection measurement within approximately 6 s.22.4 Load-Deflection DataObtain load-deflection data, asrequired, using the apparatus specified in 20.2.22.5 Maximum LoadIf the purpose of the test is todetermine strength pro

37、perties, record the maximum load at-tained in the test.NOTE 15In proof loading, the intended load target may not be reachedor may be exceeded slightly. For some applications, it is recommendedthat both the actual attained load and the target load be recorded.22.6 Record of FailureDepending on the pu

38、rpose of thetest, a description of the characteristic causing failure, and itslocation within the test span, may be required. (See Note 10.)23. Report23.1 The content of the report depends on the purpose of thetest program. The report shall include, at the minimum, allapplicable information as outli

39、ned in Section 11.AXIAL STRENGTH IN TENSION24. Scope24.1 This test method provides procedures for the determi-nation of the axial tensile strength of stress-graded lumber andother wood-base structural material.25. Summary of Test Method25.1 The specimen is subjected to an axial tensile loadapplied n

40、ear its ends. The specimen is loaded at a prescribedrate and observation of load is made until failure occurs or apreselected load is reached.26. Apparatus26.1 Testing Machine, combining (1) a loading mechanismfor applying an axial tensile load at a specified rate and (2)aforce-measuring apparatus t

41、hat can be calibrated to the accu-racy requirements of 26.3 following procedures outlined inPractices E4.26.2 Grips or Clamping Devices, to transmit the tensile loadfrom the testing machine to the test specimen such that (1) thespecimen damage due to clamping is minimized and (2)slippage is minimize

42、d during load application.26.2.1 Distance Between GripsThe clear distance be-tween grips depends on the purpose of the test program and thematerial being tested.NOTE 16It is recommended that, for stress-graded lumber, the cleardistance between grips be, at the minimum, 25 times the width of the test

43、specimen in order to minimize problems of end fixity and to properlyaccount for the effect of grain deviations on strength. Because of practicallimitations on the use of equipment for field testing, this may not alwaysbe feasible for the wider width of stress-graded lumber, for which a cleardistance

44、 between grips less than 12 times the width of the test specimenis not recommended. The width here refers to the dressed dry sizespecified in the size classification the current version of PS20. Tominimize problems in the interpretation of data results, it is furtherrecommended that all specimens be

45、 tested at a constant clear span betweengrips.26.3 AccuracyThe force-measuring apparatus shall besuch as to permit load measurements with an error not toexceed 62.0 % of the load.27. Test Specimen27.1 Cross SectionSee 9.1.27.2 LengthThe minimum specimen length shall be theclear distance between grip

46、s, determined in accordance with26.2.1, plus any required length to achieve contact along thefull length of the grips.27.3 ConditioningSee 9.3.28. Procedure28.1 Specimen Measurements:28.1.1 Measure and record before testing the cross-sectionaldimensions and moisture content of every specimen for whi

47、chthe tensile strength is to be calculated. Make measurements atmidlength of the specimen unless another location is moreappropriate to the purpose of the test.28.1.2 Accuracy of Measurements of the Cross-SectionalDimensionsSee 10.1.2.D476105628.1.3 Moisture Content MeasurementsSee 10.1.3.28.2 Test

48、SetupCenter the specimen in the grips, takingcare to have the long axis of the specimen coincide with thedirection of load application. Apply load to the specimen at arate determined in accordance with 28.3.28.3 Speed of TestingThe test rate shall be such that thesample target failure load would be

49、achieved in approximately1 min (Note 6). Failure load should not be reached in less than10 s nor more than 10 min.NOTE 17For stress-graded lumber, a stress rate of approximately4000 psi (30 MPa)/min will usually permit the test to be completed in theprescribed time, in cases where the target failure load is the average failureload for the sample.28.4 Maximum LoadSee 10.5.28.5 Record of FailureSee 10.6.29. Report29.1 The content of the report depends on the purpose of thetest program. The report shall include, at the minimum, allapplicable information as p