ASTM D2395-2007a Standard Test Methods for Specific Gravity of Wood and Wood-Based Materials《木材和木基材料比重的标准试验方法》.pdf

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1、Designation: D 2395 07aStandard Test Methods forSpecific Gravity of Wood and Wood-Based Materials1This standard is issued under the fixed designation D 2395; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision

2、. A 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.1. Scope1.1 These test methods cover the determination of the

3、specific gravity of wood and wood-based materials to generallydesired degrees of accuracy and for specimens of differentsizes, shapes, and moisture content conditions. The methodtitle is indicative of the procedures used or the specific area ofuse.SectionMethod AVolume by Measurement 7Method BVolume

4、 by Water Immersion 8Method CFlotation Tube 9Method DForstner Bit 10Method EIncrement Core 11Method FChips 121.2 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

5、 and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 9 Terminology Relating to Wood and Wood-Based Prod-uctsD 2555 Practice for Establishing Clear Wood Strength Val-uesD 4442 Test Methods for Direct Moisture Conten

6、t Measure-ment of Wood and Wood-Base MaterialsD 4444 Test Methods for Use and Calibration of Hand-HeldMoisture MetersE 1547 Terminology Relating to Industrial and SpecialtyChemicals3. Terminology3.13.1.1 green volume, nthe solid wood volume before anyshrinkage occurs due to drying to moisture conten

7、t below thefiber saturation point (about 30 %).3.1.2 moisture content, nin this standard, the amount ofwater contained in wood, expressed as a percentage of the massof oven-dry wood.3.1.2.1 DiscussionIn general, the amount of water inwood can be expressed on two different bases: as a percentageof th

8、e mass of oven-dry wood, or a percentage of the total massof wood and water. To avoid misunderstandings, it must beclear which basis is being used. In the forest industry and thewood products industry, the moisture content is usually ex-pressed as a percentage of the mass of oven-dry wood.3.1.3 spec

9、ific gravity, nin this standard, the ratio of theoven-dry mass of a specimen to the mass of a volume of waterequal to the volume of the specimen at a specified moisturecontent.3.1.3.1 DiscussionAs both the mass and volume of woodvary with the amount of moisture contained in the wood,specific gravity

10、 as applied to wood is an indefinite quantityunless the conditions under which it is determined are clearlyspecified. The specific gravity of wood is based on theoven-dry mass, but the volume may be that in the oven-dry,partially dry, or green condition. For further discussion, seeAppendix X2.3.1.3.

11、2 specific gravity at X % moisture content, nspecificgravity based on oven-dry mass of wood and its volume at aspecified moisture content (X %) between the oven-dry condi-tion and the fiber saturation point (volume at 12 % moisturecontent is frequently used).3.1.3.3 specific gravity, basic, nspecifi

12、c gravity based onoven-dry mass of wood and its green volume.3.1.3.4 specific gravity, oven-dry, or on oven-dry basis,nspecific gravity based on oven-dry mass of wood and itsoven-dry volume.4. Summary of Test Methods4.1 The accuracy of the specific gravity value obtained on arepresentative specimen

13、will depend upon the accuracy of themeasurements made. If the specimens are carefully preparedand regular in shape, the volume determined by Method A canbe quite exact. The volume of irregularly shaped specimenscan best be determined by immersion in water and if due care1These test methods are under

14、 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 1, 2007. Published July 2007. Originally approvedin 1965. Last previous edition approved in 2007 as D 2395 07.2For reference

15、d ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Con

16、shohocken, PA 19428-2959, United States.is taken to prevent absorption of water, Method B will giveresults of great precision. Method C is an approximate methodbut a procedure that can be very useful, particularly as part ofa production procedure. Methods D and E are especiallyadapted to gravity mea

17、surements of living trees or of in-placeelements and the accuracy of the result is dependent upon thecare used in obtaining the specimen. Method F is a specificprocedure for wood chips.5. Significance and Use5.1 The specific gravity of wood gives an excellent measureof the amount of wood substance p

18、resent in a sample. Thus, itmay serve as a valuable indicator of the amount of wood pulpthat could be produced, the workability of the material, or thestrength characteristics of a specimen or a species. It should berecognized that specific gravity varies between trees, within atree, and between spe

19、cies. Since the specific gravity of woodsubstance is practically constant for all species (approximately1.53), it is apparent that individual specific gravity values areindicative of the amount of wood substance present. It affordsa rapid and valuable method for selection of wood for specificuses.5.

20、2 It may be desirable to know the specific gravity of aliving tree, a structural member already in place, a log crosssection, a segment of a research element, or the earlywood orlatewood layer. The specimen thus may be large or small,regular or irregular, and at a variety of moisture contents. These

21、test methods give procedures that include all of these variablesand provides for calculation of specific gravity values todegrees of accuracy generally needed.6. Test Specimens6.1 The specific gravity specimens shall be fully represen-tative of the material from which they are taken. The specimensiz

22、e shall be such that accurate measurements of mass andvolume are easy to attain. Where other standards specify thelocation and size of specific gravity specimens, these require-ments shall be carefully followed. The specimens shall becarefully cut from the larger element to ensure clean-cutsurfaces.

23、 All loose fibers shall be carefully removed before thespecimen is weighed and measured. The specimen shall be freefrom knots, and if pitch or other infiltrates are present, this shallbe noted in the report or they shall be extracted before specificgravity values are obtained.6.2 MeasurementsThe dim

24、ensions of test specimens shallbe measured to a precision of 60.3 % or less, and the massshall be determined to a precision of 60.2 % or less. Wheredrying of specimens is required, this shall be done in an ovenmaintained at 103 6 2C. (For most panel materials and woodspecimens 1 in. (25 mm) in lengt

25、h parallel to grain, drying for48 h in an oven having good air circulation and exchange willbe sufficient to reach constant mass.)7. METHOD AVOLUME BY MEASUREMENT7.1 Applicability:7.1.1 Shape of SpecimenThe specimen must be regular inshape with right-angle corners for determination of volume bylinea

26、l measurement. The procedure is adaptable to any size ofspecimen or to specimens of any moisture content. If thesurfaces of the specimen are smooth and sufficient measure-ments are taken, the volume can be obtained with considerableaccuracy. Special care must be taken in measurement of verysmall or

27、thin specimens. Volume of irregular or rough-surfacedspecimens should be obtained by Method B.7.2 Procedures7.2.1 MeasurementMeasure the length (L), width (w), andthickness (t) of the specimen in accordance with 6.2 in asufficient number of places to ensure an accurate indication ofvolume. In small

28、specimens, uniform in size, one or twomeasurements of each dimension will suffice; in larger speci-mens the number of measurements will depend on the unifor-mity of the specimen, but at least three measurements of eachdimension will be required.7.2.2 MassDetermine the initial mass (I) of the specime

29、nat the time of test in accordance with 6.2.7.2.3 Moisture ContentDetermine the moisture content(M) of the specimen to permit description of the basis on whichthe specific gravity is computed. Test Methods D 4442 andD 4444 indicate procedures that should be used.7.2.4 Small SpecimensThe entire speci

30、men may be usedfor determination of moisture content.7.2.5 Intermediate SpecimensWhen the specimen is of asize that is unsuitable for moisture content determinations (thetime to oven-dry to constant mass would be excessive), asegment may be cut from the specimen for a moisture contentspecimen. Selec

31、t this segment so that its moisture content isrepresentative of that of the larger specimen. Where possible insolid wood elements, the moisture content specimen shall be offull cross-sectional dimensions and 1 in. (25 mm) in length(parallel to grain). In sheet materials the specimen shall beequal in

32、 thickness to the thickness of the material and 3 by 6 in.(76 by 122 mm) in size.7.2.6 Structural ElementsIn full-sized members, deter-mine the moisture content from a segment cut from themember. It shall be of full cross-sectional dimensions and 1 in.(25 mm) in length (parallel to grain), and shall

33、 be selected froma representative area of the member. To avoid the effects of enddrying, cut the specimen at least 18 in. (457 mm) in from theend of the member.7.2.7 Special SituationsWhere the specimen or elementcannot be cut to secure a moisture content segment, anapproximate moisture content may

34、be obtained through the useof a moisture meter which is used in accordance with themanufacturers recommendations. Since the moisture contentvalue is approximate, it should be recognized that the specificgravity value obtained will also be approximate.7.2.8 Specimen PreparationWhen the moisture conte

35、ntspecimen is a portion of the element, remove all loose particlesfrom the specimen and determine the initial mass (I)inaccordance with 6.2.7.3 DryingOven-dry the moisture content specimen toconstant mass in accordance with 6.2, and determine theoven-dry mass (F).8. METHOD BVOLUME BY WATER IMMERSION

36、8.1 ApplicabilityD 2395 07a28.1.1 Type of SpecimenThis procedure is particularlyadaptable to specimens of irregular shape or having a roughsurface. Limitations on specimen size are based primarily onsize of immersion tanks available. In small size specimens, lessthan 1 cm3in volume, air bubbles adhe

37、ring to the specimensurface can result in considerable error in volume measurementand thus to the computed specific gravity value. Freshly cutgreen wood will not absorb appreciable quantities of waterduring the brief immersion period.As soon as any drying of thewood has taken place however, the surf

38、ace must be sealedbefore immersion in water or else the volumetric displacementof the wood specimen will be in error in an amount equal to thevolume of water absorbed by the wood.8.2 Procedures8.2.1 MassDetermine the initial mass (I) of the specimenat time of test in accordance with 6.2.8.2.2 Volume

39、Determine the volume of the specimen byone of the following modes. Volume may be determined in theas received condition if the specimen is green; or in the asreceived condition if the specimen is partially dry or afteroven-drying if the pores are adequately sealed (see 8.2.2.5).Determine the volume

40、of the specimen by measuring thevolume of water displaced or by determining the mass of thewater displaced. The mass in grams is numerically equal to thevolume in cubic centimetres.8.2.2.1 Mode IPlace the specimen in a tank of knownvolume and add sufficient water to fill the tank. Then removethe spe

41、cimen and determine the volume of water remaining.The tank volume less the volume of water remaining is equalto the volume of the specimen. The relationship betweenspecimen volume and tank volume shall be such that theprecision of specimen volume measurement is high.8.2.2.2 Mode IIPlace a container

42、holding enough water tocompletely submerge the specimen on one pan of a balance asshown in Fig. 1. Then balance the combined mass of thecontainer and water with mass added to the other pan. Hold thespecimen so that it is completely submerged without touchingthe sides of the container by means of a s

43、harp, pointed, slenderrod and balance the scales again. The mass added to restorebalance is equal to the mass of water displaced by thespecimen.Alternatively, an automatic balance may be used andwill greatly facilitate the speed of such measurements. If verysmall specimens are used, the accuracy of

44、resulting data islikely to be low.8.2.2.3 Mode IIIPlace a container holding enough waterto completely submerge the specimen below one pan of abalance as shown in Fig. 2. The container shall be sufficientlylarge so that immersion of the specimen causes no materialchange in water level. Suspend a wire

45、 basket of sufficient massto hold the specimen submerged from this same pan andimmerse it in the water. Balance the mass of the basket whenfreely immersed with mass added to the other scale pan. Weighthe specimen in air. Place the specimen in the basket and holdit completely submerged without touchi

46、ng the container whilebalancing the scales again. The mass added to restore balance,if the specimen is lighter than water, plus the mass of thespecimen in air equals the volume of water displaced. If thespecimen is heavier than water, subtract the mass added torestore balance from the mass of the sp

47、ecimen in air todetermine the volume of water displaced.8.2.2.4 Mode IVImmerse the specimen, of an elongatedshape, in a graduated tube having a cross section only slightlylarger than that of the specimen as shown in Fig. 3. Read thewater level in the tube, preferably to an even graduation mark,befor

48、e immersing the specimen. Immerse the specimen, hold itsubmerged with a slender pointed rod if necessary, anddetermine the water level again. The difference in water levelis equal to the volume of the specimen.8.2.2.5 Surface Treatment of Specimen Green specimensmay be immersed in water for volume d

49、eterminations withoutmaterial absorption of water that will affect volume determi-nations. Dip air-dry or oven-dry specimens in hot paraffin waxbefore making volume determinations. After the wax dip,weigh the specimen again and use this mass in conjunctionwith the immersed mass for determining volume in Mode IIand Mode III (8.2.2.2 and 8.2.2.3). Alternatively, softwoodspecimens or hardwood specimens with small pores may bedipped in a solution of paraffin wax in carbon tetrachloride: 1oz of paraffin wax in 260 in.3of carbon tetrachloride (1 g ofpar