1、Designation: D 5536 94 (Reapproved 2004)Standard Practice forSampling Forest Trees for Determination of Clear WoodProperties1This standard is issued under the fixed designation D 5536; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision
2、, 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.INTRODUCTIONThe everyday use of wood for many different purposes creates a continual need for data on itsmechanical
3、 properties. Small clear specimen testing to characterize a species has historically beenemployed for such property determination, and related methods of test are outlined in Methods D 143.Because wood is a biological material, its mechanical properties are subject to considerable naturalvariation.
4、Thus, the results of tests to evaluate the mechanical properties of a species depend to a greatextent upon how the forest trees are sampled for test material. Ideally, if the results of mechanicalproperty evaluations are to be representative of the forest sampled, probability sampling of materialssu
5、ch as outlined in Practice E 105 must be used. However, true probability sampling of the forest treesfor determination of mechanical properties can be extremely complex and expensive because of thebroad geographic range and topographic conditions under which a tree species grows. In someinstances, d
6、irect probability sampling may be impractical, necessitating the need for alternativesampling procedures.2, 31. Scope1.1 This practice offers two alternative physical samplingprocedures: cruciform sampling and random sampling. Thechoice of procedure will depend upon the intended use for thetest resu
7、lts, the resources available for sampling and testing,and the availability of existing data on the mechanical proper-ties and specific gravity of the species of interest.1.2 A third procedure, double sampling, is included prima-rily by reference. This procedure applies the results of cruci-form or r
8、andom samples through correlation to improve orupdate property values.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 the
9、 applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:4D 143 Methods of Testing Small Clear Specimens of Tim-berD 2555 Method for Establishing Clear-Wood Strength Val-uesE 105 Practice for Probability Sampling of Materials3. Significance and Use3.1 This pra
10、ctice covers procedures of sampling for obtain-ing small clear wood specimens which, when tested in accor-dance with Methods D 143 and, in conjunction with full-sizeproduct tests, will provide mechanical properties for use inderiving design properties for lumbar, panels, poles, houselogs, and other
11、products.3.2 Data obtained by testing specimens sampled in accor-dance with these methods also provide information on theinfluence on mechanical properties of such factors as density,locality of growth, position in cross section, height in the tree,and moisture content.1This practice is under the ju
12、risdiction of ASTM Committee D07 on Wood andis the direct responsibility of Subcommittee D07.01 on Fundamental Test Methodsand Properties.Current edition approved May 15, 1994. Published July 1994.2Bendtsen, B. A.; Freese, Frank; Ethington, R. L., “A Forest Sampling Methodfor Wood Strength,” Forest
13、Products Journal, Vol 20, No. 11, 1970, pp. 3847.3Pearson, R. G., and Williams, E. J., “A Review of Methods for Sampling ofTimber,” Forest Products Journal, Vol 8, No. 9, 1958, pp. 263268.4For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at service
14、astm.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 Conshohocken, PA 19428-2959, United States.3.3 Cruciform sampling is of principal value when informa-
15、tion is desired on the influence on mechanical properties ofheight in the tree; of age or radial position in the tree; of rateof growth; the change from sapwood to heartwood; therelationships between mechanical properties and factors suchas specific gravity; and making general comparisons betweenspe
16、cies for purposes of rating or selecting species for specificend-use products. Cruciform sampling does not provide unbi-ased estimates of mean values, percentile or other descriptivestatistics, or a means of associating statistical confidence withestimates of descriptive statistics.3.4 Double sampli
17、ng is used when it is desired to improveor update existing estimates of mechanical property values thatare the basis for establishing allowable design stresses forstress-graded lumber, plywood, poles and piling, and otherwood products. The method involves predicting one propertyby carefully observin
18、g a well-correlated auxiliary property thatis presumably easier or cheaper to measure. A sample estimateof the auxiliary property is obtained with a high degree ofprecision by representatively sampling the population. Asmaller independent sample or a subsample of the large sampleis used to establish
19、 a relationship between the auxiliaryproperty and the property for which an estimate is desired. Asapplied to sampling a forest, double sampling has employedspecific gravity to predict mechanical properties. The double-sampling method provides unbiased estimates of mean me-chanical property values a
20、nd an approximation method forestimating percentile values. Statistical confidence may beassociated with the estimates of the means but not thepercentile values.3.5 Random sampling is used when probability estimates ofdescriptive statistics and property distributional characteristicsare desired as t
21、he basis for establishing allowable designstresses for lumber and other stress-rated products. It isapplicable when data for a species do not exist or when existingestimates are believed no longer applicable because of achanging forest character. Random sampling provides betterprobability estimates
22、than double sampling and is less expen-sive and quicker if sampling and testing must be completed toestablish mechanical property-specific gravity regressions forthe double-sampling method.4. Authentic Identification4.1 The material shall be from trees selected in the forest byone qualified to ident
23、ify the species and to select the trees.Where necessary, herbarium samples such as leaves, fruit,twigs, and bark shall be obtained to ensure positive identifica-tion.5. Cruciform SamplingPrimary Method5.1 The standard methods for preparing small clear speci-mens of timber, primary method, provide fo
24、r cutting the logsections (divided into and identified as bolts) systematicallyinto sticks of nominal 212 by 212 in. (63 by 63 mm) in crosssection, that are later surfaced to provide the test specimens 2by 2 in. (50 by 50 mm) in cross section, on which the systemis based. These methods have served a
25、s a basis for theevaluation of the various mechanical and related physicalproperties of the clear wood of different species of wood. Thesemethods have been extensively used, and a large amount ofdata based on them have been obtained and published.5.1.1 The 2 by 2-in. (50 by 50-mm) test specimen has
26、theadvantage that it embraces a number of growth rings, is lessinfluenced by earlywood and latewood differences than smallerspecimens, and is large enough to represent a considerableproportion of the material.5.1.2 The choice of specimen size may be influenced by theobjectives of sampling and by the
27、 rate of growth of thematerial. Radial property gradients are primarily influenced byage, and large specimens that encompass several rings maymask the age influence. Height gradients must be evaluated byspecimens from the same annual ring because of age influence.Thus, small specimens are preferred
28、for measuring both radialand height gradients. When the purpose of sampling is toestimate clear wood properties, large specimens that include anumber of annual rings are preferred. Even with 2 by 2-in. (50by 50-mm) specimens, fast rates of growth will result in fewrings per specimen. Regardless of t
29、he purpose of sampling, theanalysis and reporting of data may require careful consider-ation of the character of the specimen.5.2 Selection of Number of TreesFor each species to betested, select the number and the character of the trees toaccomplish the purpose of the sampling. For traditional me-ch
30、anical property data base development, a minimum of fivetrees have usually been selected that have been judged “rep-resentative” of the trees harvested of the species. Note that ifunbiased estimates and statistical confidence statements arerequired, other methods are needed (Section 3).5.3 Selection
31、 and Number of Bolts The material of eachspecies selected for test shall be representative of the clear,straight-grained wood in the merchantable bole of the tree. Atraditional method of selection is shown in Appendix X2. Notethat the sampling permits varying the intensity of sampling bytree (in acc
32、ordance with A2) if the resulting data will supportthe anticipated analysis. X2.1 illustrates merchantable sectionand bolt labeling.5.4 Substitution of Flitches for Bolts:5.4.1 In cases where the logs or bolts are over 60 in. (1.5 m)in diameter, a single flitch 6 in. (150 mm) in thickness, takenthro
33、ugh the pith representing the full diameter of the log, maybe substituted, in the same length, for the full log or boltspecified in 5.3.5.4.2 Where orientation of test specimen to geographicfeatures is considered critical, flitch shall maintain the coordi-nates regarded as important in the specimen
34、of 5.9.5.5 Selection for Site Representation Inferences in analy-sis that relate to geographic distribution or site-specific featuresmust be anticipated in selecting both the sample numbers andsources. The number of trees shall conform to 5.2 and 5.3. Ifthe analysis requires statistical inferences,
35、random sampling(Section 7) is one method.5.6 Field Marking:5.6.1 Field marking procedures shall ensure identification oftrees, bolts, and shipment. Appendix X2 provides a traditionalmethod.D 5536 94 (2004)25.6.2 If the orientation of test specimens to geographical orbolt features is critical, mainte
36、nance of cardinal point orienta-tion is recommended.5.7 Field Descriptions:5.7.1 Complete field notes describing the material shall befully and carefully made by the collector. These notes shall besufficient to supply documentation similar to that in TableX1.1, with actual content chosen as appropri
37、ate for theobjectives of the study.5.7.2 Photographs of the standing trees selected should betaken when practicable.5.8 Preparation for ShipmentMaintenance of moisturecontent of the material and of all labeling documentation is arequirement. Paragraph X2.3 provides traditional guidelines.5.9 Sawing
38、and Marking of Bolts and Test SticksSectionsof logs (consisting of two bolts) shall be marked and sawn into212 by 212-in. (60 by 60-mm) sticks. Marking of bolts andsticks shall maintain continuity to the tree, and shipment.Consistency with 5.6 shall be maintained. Paragraphs A2.1through A2.4 documen
39、t the traditional procedures.5.10 Matching for Tests of Dry Material:5.10.1 If one purpose of sampling is to provide comparisonof green and dry properties, provisions may be made formatching of specimens within the tree. The traditional ap-proach is as follows:5.10.2 The collection of the material (
40、Section 5) has beenarranged to provide for tests of both green and dry specimensthat are closely matched by selection from adjacent parts of thesame tree. The 8-ft (2.4-m) long sections, after being marked inaccordance with 5.9.1, shall be sawn and marked in 212 by212-in. (60 by 60-mm) by 8-ft stick
41、s. Each 212 by 212-in. by8-ft stick shall then be cut into two 4-ft (1.2-m) pieces, makingsure that each part carries the proper designation and bolt letter.5.10.3 Some of the 212 by 212-in. by 4-ft (60 by 60-mm by1.2-m) sticks from each 8-ft (2.4-m) section are to providespecimens to be tested gree
42、n (unseasoned) and the remainingones are to be dried and tested. To afford matching, the 4-ftsticks of one bolt shall be interchanged with the 4-ft sticks ofthe next adjacent bolt from the same tree to form twocomposite bolts, each being complete and being made of equalportions of the adjacent 4-ft
43、bolts. The sticks from one of thesecomposite bolts shall be tested green and those from the othershall be tested after drying. Thus, the sticks of each compositebolt shall be regarded as if they were from the same bolt.Paragraph X2.5 illustrates a method of forming compositebolts.5.10.4 The traditio
44、nal procedure provides for end-to-endmatching (end matching) of sticks to be tested dry with thoseto be tested green, which is to be preferred when practicable. If,because of the nature of the material, end matching is notpracticable, side matching may be used.6. Cruciform SamplingSecondary Method6.
45、1 The cruciform secondary method is intended for use inevaluating the properties of wood only when relatively smalltrees, generally less than 12 in. (300 mm) in diameter, areavailable to provide the test specimens and only when suchtrees because of crook, cross grain, knots, or other defects areof s
46、uch quality that the longer clear, straight-grained specimensrequired by the primary method cannot reasonably be obtained.Whenever possible, the procedure for the primary method shallbe used regardless of the size of trees. Since the procedure forthe secondary method for many features, such as in se
47、lectionand care of material, is identical with the primary method, thesecondary method presented herewith are referenced to theprimary method, and procedure is given only where it differstherefrom. For convenience the section numbers in the second-ary method corresponds in the last two digits with t
48、henumbering of the primary method. Thus Section 6 for thesecondary method corresponds in subject matter to Section 5.6.1.1 Because of the cross-sectional size and the length ofspecimen required for some of the tests (30 in. (760 mm) forstatic and impact bending) it is, however, sometimes difficult t
49、oobtain test specimens in adequate number and entirely free ofdefects from bolts representing smaller trees, particularly treesunder 12 to 15 in. (30 to 38 cm) in diameter. With increasingneed for evaluating the properties of species involving smallertrees, and the increasing importance of second-growth timberthat is expected to be harvested much before it reaches the sizesattained in virgin stands, there has developed a need forsecondary methods of test in which at least the longer testspecimens are smaller than 2 by 2 in. (50 by 50 mm) in crosssection.6.1.2 The exc
