ASTM D143-1994(2007) Standard Test Methods for Small Clear Specimens of Timber《洁净木材小样品试验的标准方法》.pdf

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1、Designation: D 143 94 (Reapproved 2007)Standard Test Methods forSmall Clear Specimens of Timber1This standard is issued under the fixed designation D 143; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A

2、 number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.INTRODUCTIONThe need to classify wood species by evaluating the

3、physical and mechanical properties of smallclear specimens has always existed. Because of the great variety of species, variability of the material,continually changing conditions of supply, many factors affecting test results, and ease of comparingvariables, the need will undoubtedly continue to ex

4、ist.In the preparation of these methods for testing small clear specimens, consideration was given bothto the desirability of adopting methods that would yield results comparable to those already availableand to the possibility of embodying such improvements as experience has shown desirable. In vie

5、wof the many thousands of tests made under a single comprehensive plan by the U.S. Forest Service,the former Forest Products Laboratories of Canada (now Forintek Canada Corp.), and other similarorganizations, the methods naturally conform closely to the methods used by these institutions. Thesemetho

6、ds are the outgrowth of a study of both American and European experience and methods. Thegeneral adoption of these methods will tend toward a world-wide unification of results, permitting aninterchange and correlation of data, and establishing the basis for a cumulative body of fundamentalinformatio

7、n on the timber species of the world.Descriptions of some of the strength tests refer to primary methods and secondary methods. Primarymethods provide for specimens of 2 by 2-in. (50 by 50-mm) cross-section. This size of specimen hasbeen extensively used for the evaluation of various mechanical and

8、physical properties of differentspecies of wood, and a large number of data based on this primary method have been obtained andpublished.The 2 by 2-in. (50 by 50-mm) size has the advantage in that it embraces a number of growth rings,is less influenced by earlywood and latewood differences than smal

9、ler size specimens, and is largeenough to represent a considerable portion of the sampled material. It is advisable to use primarymethod specimens wherever possible. There are circumstances, however, when it is difficult orimpossible to obtain clear specimens of 2 by 2-in. cross section having the r

10、equired 30 in. (760 mm)length for static bending tests. With the increasing incidence of smaller second growth trees, and thedesirability in certain situations to evaluate a material which is too small to providea2by2-in.cross-section, a secondary method which utilizesa1by1-in. (25 by 25-mm) cross s

11、ection has beenincluded. This cross section is established for compression parallel to grain and static bending tests,while the 2 by 2-in. cross-section is retained for impact bending, compression perpendicular to grain,hardness, shear parallel to grain, cleavage, and tension perpendicular to grain.

12、 Toughness and tensionparallel to grain are special tests using specimens of smaller cross section.The user is cautioned that test results between two different sizes of specimens are not necessarilydirectly comparable. Guidance on the effect of specimen size on a property being evaluated is beyondt

13、he scope of these methods, and should be sought elsewhere.Where the application, measurement, or recording of load and deflection can be accomplished usingelectronic equipment and computerized apparatus, such devices are encouraged, providing they do notlower the standard of accuracy and reliability

14、 available with basic mechanical equipment.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.1. Scope1.1 These methods cover the determination of variousstrength and related properties of wood by testing small clearspecimens.1.1.1 Thes

15、e methods represent procedures for evaluating thedifferent mechanical and physical properties, controlling fac-tors such as specimen size, moisture content, temperature, andrate of loading.1.1.2 Sampling and collection of material is discussed inPractice D 5536. Sample data, computation sheets, and

16、cardshave been incorporated, which were of assistance to theinvestigator in systematizing records.1.1.3 The values stated in inch-pound units are to beregarded as the standard. The SI values are given in parenthe-ses and are provided for information only. When a weight isprescribed, the basic inch-p

17、ound unit of weight (lbf) and thebasic SI unit of mass (Kg) are cited.1.2 The procedures for the various tests appear in thefollowing order:SectionsPhotographs of Specimens 5Control of Moisture Content and Temperature 6Record of Heartwood and Sapwood 7Static Bending 8Compression Parallel to Grain 9I

18、mpact Bending 10Toughness 11Compression Perpendicular to Grain 12Hardness 13Shear Parallel to Grain 14Cleavage 15Tension Parallel to Grain 16Tension Perpendicular to Grain 17Nail Withdrawal 18Specific Gravity and Shrinkage in Volume 19Radial and Tangential Shrinkage 20Moisture Determination 21Permis

19、sible Variations 22Calibration 231.3 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 limitat

20、ions prior to use.2. Referenced Documents2.1 ASTM Standards:2D 198 Test Methods of Static Tests of Lumber in StructuralSizesD 2395 Test Methods for Specific Gravity of Wood andWood-Based MaterialsD 3043 Test Methods for Structural Panels in FlexureD 3500 Test Methods for Structural Panels in Tension

21、D 4442 Test Methods for Direct Moisture Content Measure-ment of Wood and Wood-Base MaterialsD 4761 Test Methods for Mechanical Properties of Lumberand Wood-Base Structural MaterialD 5536 Practice for Sampling Forest Trees for Determina-tion of Clear Wood PropertiesE4 Practices for Force Verification

22、 of Testing Machines3. Summary of Methods3.1 The mechanical tests are static bending, compressionparallel to grain, impact bending toughness, compressionperpendicular to grain, hardness, shear parallel to grain (Note1), cleavage, tension parallel to grain, tension-perpendicular-to-grain, and nail-wi

23、thdrawal tests. These tests may be made onboth green and air-dry material as specified in these methods.In addition, methods for evaluating such physical properties asspecific gravity, shrinkage in volume, radial shrinkage, andtangential shrinkage are presented.NOTE 1The test for shearing strength p

24、erpendicular to the grain(sometimes termed “vertical shear”) is not included as one of the principalmechanical tests since in such a test the strength is limited by the shearingresistance parallel to the grain.4. Significance and Use4.1 These methods cover tests on small clear specimens ofwood that

25、are made to provide the following:4.1.1 Data for comparing the mechanical properties ofvarious species,4.1.2 Data for the establishment of correct strength func-tions, which in conjunction with results of tests of timbers instructural sizes (see Methods D 198 and Test Method D 4761),afford a basis f

26、or establishing allowable stresses, and4.1.3 Data to determine the influence on the mechanicalproperties of such factors as density, locality of growth,position in cross section, height of timber in the tree, change ofproperties with seasoning or treatment with chemicals, andchange from sapwood to h

27、eartwood.5. Photographs of Specimens5.1 Four of the static bending specimens from each speciesshall be selected for photographing, as follows: two averagegrowth, one fast growth, and one slow growth. These speci-mens shall be photographed in cross section and on the radialand tangential surfaces. Fi

28、g. 1 is a typical photograph of a crosssection of 2 by 2-in. (50 by 50-mm) test specimens, and Fig. 2is the tangential surface of such specimens.6. Control of Moisture Content and Temperature6.1 In recognition of the significant influence of temperatureand moisture content on the strength of wood, i

29、t is highlydesirable that these factors be controlled to ensure comparabletest results.6.2 Control of Moisture ContentSpecimens for the test inthe air-dry condition shall be dried to approximately constantweight before test. Should any changes in moisture contentoccur during final preparation of spe

30、cimens, the specimensshall be reconditioned to constant weight before test. Testsshall be carried out in such manner that large changes inmoisture content will not occur. To prevent such changes, it is1These methods are under the jurisdiction of ASTM Committee D07 on Woodand are the direct responsib

31、ility of Subcommittee D07.01 on Fundamental TestMethods and Properties.Current edition approved April 1, 2007. Published April 2007. Originallyapproved in 1922. Last previous edition approved in 2000 as D 143 94 (2000)e1.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact

32、 ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.D 143 94 (2007)2desirable that the testing room and rooms for preparation of testspecimens have some means of humidity control.6.3 Control o

33、f TemperatureTemperature and relative hu-midity together affect wood strength by fixing its equilibriummoisture content. The mechanical properties of wood are alsoaffected by temperature alone. When tested, the specimensshall be at a temperature of 68 + 6F (20 + 3C). The tempera-ture at the time of

34、test shall in all instances be recorded as aspecific part of the test record.7. Record of Heartwood and Sapwood7.1 Proportion of SapwoodThe estimated proportion ofsapwood present should be recorded for each test specimen.8. Static Bending8.1 Size of SpecimensThe static bending tests shall bemade on

35、2 by 2 by 30 in. (50 by 50 by 760 mm) primarymethod specimens or 1 by 1 by 16 in. (25 by 25 by 410 mm)secondary method specimens. The actual height and width atthe center and the length shall be measured (see 22.2).8.2 Loading Span and SupportsUse center loading and aspan length of 28 in. (710 mm) f

36、or the primary method and 14in. (360 mm) for the secondary method. These spans wereestablished in order to maintain a minimum span-to-depth ratioof 14. Both supporting knife edges shall be provided withbearing plates and rollers of such thickness that the distancefrom the point of support to the cen

37、tral plane is not greater thanthe depth of the specimen (Fig. 3). The knife edges shall beadjustable laterally to permit adjustment for slight twist in thespecimen (Note 2).NOTE 2Details of laterally adjustable supports may be found in Fig.1 of Methods D 3043.8.3 Bearing BlockA bearing block of the

38、form and size ofthat shown in Fig. 4 shall be used for applying the load forprimary method specimens. A block having a radius of 112 in.FIG. 1 Cross Sections of Bending Specimens Showing Different Rates of Growth of Longleaf Pine (2 by 2-in. (50 by 50-mm) Specimens)FIG. 2 Tangential Surfaces of Bend

39、ing Specimens of Different Rates of Growth of Jeffrey Pine 2 by 2-in. (50 by 50 by 760-mm)SpecimensD 143 94 (2007)3(38 mm) for a chord length of not less than 2 in. (50 mm) shallbe used for secondary method specimens.8.4 Placement of Growth RingsThe specimen shall beplaced so that the load will be a

40、pplied through the bearingblock to the tangential surface nearest the pith.8.5 Speed of TestingThe load shall be applied continu-ously throughout the test at a rate of motion of the movablecrosshead of 0.10 in. (2.5 mm)/min (see 22.3), for primarymethod specimens, and at a rate of 0.05 in. (1.3 mm)/

41、min forsecondary method specimens.8.6 Load-Deflection Curves:8.6.1 Load-deflection curves shall be recorded to or beyondthe maximum load for all static bending tests. The curves shallbe continued to a 6 in. (150 mm) deflection, or until thespecimen fails to support a load of 200 lbf (890 N) for prim

42、arymethod specimens and to a 3 in. (76 mm) deflection or until thespecimen fails to support a load of 50 lbf (220 N) for secondarymethod specimens.8.6.2 Deflections of the neutral plane at the center of thelength shall be taken with respect to points in the neutral planeabove the supports. Alternati

43、vely, deflection may be takenrelative to the tension surface at midspan. However, take careto ensure that vertical displacements which may occur at thereactions are accounted for.8.6.3 Within the proportional limit, deflection readings shallbe taken to 0.001 in. (0.02 mm). After the proportional lim

44、it isreached, less refinement is necessary in observing deflections,but it is convenient to read them by means of the dial gage (Fig.3) until it reaches the limit of its capacity, normally approxi-mately 1 in. (25 mm). Where deflections beyond 1 in. areencountered, the deflections may be measured by

45、 means of thescale mounted on the loading head (Fig. 3) and a wire mountedat the neutral axis of the specimen of the side opposite theyoke. Deflections are read to the nearest 0.01 in. (0.2 mm) at0.10 in. (2.5 mm) intervals and also after abrupt changes inload.8.6.4 The load and deflection of first

46、failure, the maximumload, and points of sudden change shall be read and shown onthe curve sheet (Note 3) although they may not occur at one ofthe regular load or deflection increments.NOTE 3See Fig. 5 for a sample static bending data sheet form.8.7 Description of Static Bending FailuresStatic bendin

47、g(flexural) failures shall be classified in accordance with theFIG. 3 Static Bending Test Assembly Showing Method of Load Application, Specimen Supported on Rollers and Laterally AdjustableKnife Edges, and Method of Measuring Deflection at Neutral Axis by Means of Yoke and Dial Attachment (Adjustabl

48、e scale mounted onloading head is used to measure increments of deformation beyond the dial capacity.)FIG. 4 Details of Bearing Block for Static Bending TestsD 143 94 (2007)4appearance of the fractured surface and the manner in whichthe failure develops (Fig. 6). The fractured surfaces may beroughly

49、 divided into “brash” and “fibrous”, the term “brash”indicating abrupt failure and“ fibrous” indicating a fractureshowing splinters.8.8 Weight and Moisture ContentThe specimen shall beweighed immediately before test, and after the test a moisturesection approximately 1 in. (25 mm) in length shall be cut fromthe specimen near the point of failure. (see 21.1 and 22.1).9. Compression Parallel to Grain9.1 Size of SpecimensThe compression-parallel-to-graintests shall be made on 2 by 2 by 8 in. (50 by 50 by 200 mm)primary method specimens, or 1 by 1 by 4 in. (25 by 25