1、Designation: D 2256 02 (Reapproved 2008)Standard Test Method forTensile Properties of Yarns by the Single-Strand Method1This standard is issued under the fixed designation D 2256; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、 year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () 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 This test method covers the
3、determination of tensileproperties of monofilament, multifilament, and spun yarns,either single, plied, or cabled with the exception of yarns thatstretch more than 5.0 % when tension is increased from 0.05 to1.0 cN/tex (0.5 to 1.0 gf/tex).1.2 This test method covers the measurement of breakingforce
4、and elongation of yarns and includes directions for thecalculation of breaking tenacity, initial modulus, chord modu-lus, and breaking toughness.1.2.1 Options are included for the testing of specimens in:(A) straight, (B) knotted, and (C) looped form.1.2.2 Conditions of test are included for the tes
5、ting ofspecimens that are: (1) conditioned air, (2) wet, not immersed,(3) wet, immersed, (4) oven-dried, (5) exposed to elevatedtemperature, or (6) exposed to low temperature.NOTE 1Special methods for testing yarns made from specific fibers;namely, glass, flax, hemp, ramie, and kraft paper and for s
6、pecific products;namely, tire cords and rope, have been published: Test Methods D 885,and Specification D 578.NOTE 2For directions covering the determination of breaking force ofyarn by the skein method refer to Test Method D 1578.1.3 This standard does not purport to address all of thesafety concer
7、ns, 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. Referenced Documents2.1 ASTM Standards:2D76 Specification for Tensile Testing Mac
8、hines for TextilesD 123 Terminology Relating to TextilesD 578 Specification for Glass Fiber StrandsD 885 Test Methods for Tire Cords, Tire Cord Fabrics, andIndustrial Filament Yarns Made from ManufacturedOrganic-Base FibersD 1578 Test Method for Breaking Strength of Yarn in SkeinFormD 1776 Practice
9、for Conditioning and Testing TextilesD 2258 Practice for Sampling Yarn for TestingD 2904 Practice for Interlaboratory Testing of a Textile TestMethod that Produces Normally Distributed DataD 2906 Practice for Statements on Precision and Bias forTextilesD 4848 Terminology Related to Force, Deformatio
10、n andRelated Properties of TextilesD 4849 Terminology Related to Yarns and FibersE 178 Practice for Dealing With Outlying Observations3. Terminology3.1 Definitions:3.1.1 Refer to Terminology D 4848 for definitions of thefollowing terms used in this standard: breaking force, breakingstrength, breakin
11、g tenacity, breaking toughness, chord modu-lus, elongation, elongation at break, elongation at rupture,initial modulus, knot-breaking force, knot breaking strength,linear density, loop breaking force, loop-breaking strength,single-strand breaking force, single-strand breaking strength,strength and t
12、enacity.3.1.2 Refer to Terminology D 123 and Terminology D 4849and for definitions of other terms used in this standard.4. Summary of Test Method4.1 Single-strand yarn specimens are broken on a tensiontesting machine at a predetermined elongation rate and thebreaking force and the elongation at brea
13、k are determined.Elongation at a specified force or the force or tenacity at aspecified elongation may also be obtained. Breaking force,breaking tenacity, elongation, initial and chord modulus, andbreaking toughness of the test specimen, in terms of lineardensity, may be calculated from machine scal
14、es, dials, record-ing charts, or by an interfaced computer.4.2 This test method offers the following three physicalconfigurations of the specimen:4.2.1 Configuration A, straight.1This test method is under the jurisdiction ofASTM Committee D13 on Textilesand is the direct responsibility of Subcommitt
15、ee D13.58 on Yarns and Fibers.Current edition approved July 1, 2008. Published August 2008. Originallyapproved in 1964. Last previous edition approved in 2002 as D 2256 02.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For An
16、nual 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.4.2.2 Configuration B, knotted.4.2.3 Configuration C, looped.4.3 This test
17、 method also offers the following six conditionsof test with respect to moisture content of the specimens at thetime of testing:4.3.1 Condition 1, conditioned to moisture equilibrium fortesting with standard atmosphere for testing textiles.4.3.2 Condition 2, wet not immersed.4.3.3 Condition 3, wet i
18、mmersed.4.3.4 Condition 4, oven-dried.4.3.5 Condition 5, high temperature.4.3.6 Condition 6, low temperature.4.4 A test option is specified by combining a specimenconfiguration and a moisture content condition, for example,OptionA1 means a straight specimen conditioned and tested ina standard atmosp
19、here for testing textiles.4.5 Unless otherwise indicated, the phrase “single-strandbreaking force” is associated with Option A1.5. Significance and Use5.1 Acceptance TestingOptionA1 of Test Method D 2256is considered satisfactory for acceptance testing of commercialshipments because the test method
20、has been used extensively inthe trade for acceptance testing. However, this statement is notapplicable to knot and loop breaking force tests, tests on wetspecimens, tests on oven-dried specimens, or tests on speci-mens exposed to low or high temperatures and should be usedwith caution for acceptance
21、 testing because factual informationon between-laboratory precision and bias is not available.5.1.1 If there are differences of practical significance be-tween reported test results for two laboratories (or more),comparative tests should be performed to determine if there isa statistical bias betwee
22、n them, using competent statisticalassistance. As a minimum, use the samples for such a com-parative tests that are as homogeneous as possible, drawn fromthe same lot of material as the samples that resulted in disparateresults during initial testing and randomly assigned in equalnumbers to each lab
23、oratory. The test results from the labora-tories involved should be compared using a statistical test forunpaired data, a probability level chosen prior to the testingseries. If a bias is found, either its cause must be found andcorrected, or future test results for that material must beadjusted in
24、consideration of the known bias.5.2 Fundamental PropertiesThe breaking tenacity, calcu-lated from the breaking force and the linear density, and theelongation are fundamental properties that are widely used toestablish limitations on yarn processing or conversion and ontheir end-use applications. In
25、itial modulus is a measure of theresistance of the yarn to extension at forces below the yieldpoint. The chord modulus is used to estimate the resistance toimposed strain. The breaking toughness is a measure of thework necessary to break the yarn.5.3 Comparison to Skein TestingThe single-strandmetho
26、d gives a more accurate measure of breaking forcepresent in the material than does the skein method and uses lessmaterial. The skein-breaking force is always lower than thesum of the breaking forces of the same number of ends brokenindividually.5.4 ApplicabilityMost yarns can be tested by this testm
27、ethod. Some modification of clamping techniques may benecessary for a given yarn depending upon its structure andcomposition. To prevent slippage in the clamps or damage as aresult of being gripped in the clamps, special clampingadaptations may be necessary with high modulus yarns madefrom fibers su
28、ch as glass or aramid or extended chain polyole-fin. Specimen clamping may be modified as required at thediscretion of the individual laboratory providing a representa-tive force-elongation curve is obtained. In any event, theprocedure described in this test method for obtaining tensileproperties mu
29、st be maintained.5.5 Breaking StrengthThe breaking strength of a yarninfluences the breaking strength of fabrics made from the yarn,although the breaking strength of a fabric also depends on itsconstruction and may be affected by manufacturing operations.5.5.1 Because breaking strength for any fiber
30、-type is ap-proximately proportional to linear density, strands of differentsizes can be compared by converting the observed breakingstrength to breaking tenacity (centinewtons per tex, grams-force per tex, or grams-force per denier).5.6 ElongationThe elongation of a yarn has an influenceon the manu
31、facturing process and the products made. Itprovides an indication of the likely stretch behavior of garmentareas such as knees, elbows, or other points of stress. It alsoprovides design criteria for stretch behavior of yarns or cordsused as reinforcement for items such as plastic products, hose,and
32、tires.5.7 Force-Elongation CurveForce-elongation curves per-mit the calculation of various values, not all of which arediscussed in this test method, such as elongation at break,elongation at specified force, force at specified elongation,initial elastic modulus which is resistance to stretching, co
33、m-pliance which is ability to yield under stress, and is thereciprocal of the elastic modulus, and area under the curve, ameasure of toughness, which is proportional to the work done.NOTE 3Force-elongation curves can be converted to stress-straincurves if the force is converted to unit stress, such
34、as to centinewtons pertex, or pounds per square inch, or pascals, or grams-force per tex, orgrams-force per denier, and the elongation is based on change per unitlength.5.8 Knot and Loop Breaking ForceThe reduction inbreaking force due to the presence of a knot or loop isconsidered a measure of the
35、brittleness of the yarn. Elongationin knot or loop tests is not known to have any significance andis not usually reported.5.9 Rate of OperationIn general, the breaking forcedecreases slightly as time-to-break increases.5.9.1 Operation of CRT, CRE, and CRL tension testingmachines at a constant time-t
36、o-break has been found tominimize differences in test results between the three types oftension testing machines. When tensile tests are performed at aD 2256 02 (2008)2fixed time-to-break, then reasonable agreement in breakingforce has generally been found to exist between CRT and CREtension testing
37、 machines.3Consistent results are also obtainedbetween different manufacturers of CRL tension testing ma-chines when they are operated at the same time-to-break. Theagreement is not necessarily good, however, between CRE orCRT tension testing machines on the one hand and CRLtension testing machines
38、on the other even when they are alloperated at the same time-to-break. The CRE-type tester is thepreferred tension testing machine.5.9.2 This test method specifies an average time-to-break of20 6 3 s as recommended by ISO TC 38 on Textiles, TheInternational Standards Association test committee for s
39、tan-dardizing tests for fibers, yarns, and fabrics. It also provides foralternate speeds, such as 300 6 10 mm (12 6 0.5 in.)/minwhen using a 250-mm (10-in.) gage length. See 9.2.5.9.3 The tolerance of 63 s for the time-to-break is wideenough to permit convenient adjustment of the tension testingmach
40、ines rate of operation, and it is narrow enough to ensuregood agreement between tests. The difference in breaking forcebetween tests at 17 and 23 s will usually not exceed 1.5 % ofthe higher value.5.9.4 In case a tension testing machine is not capable ofbeing operated at 20-s time-to-break, alternat
41、ive rates ofoperation are included in this test method. These alternativerates may be used only by agreement between the partiesconcerned or when required in an applicable material specifi-cation.5.10 Tests on Wet SpecimensTests on wet specimens areusually made only on yarns which show a loss of bre
42、akingforce when wet or when exposed to high humidity, forexample, yarns made from animal fibers and man-made fibersbased on regenerated and modified cellulose. Wet tests aremade on flax yarns to detect adulteration by failure to show again in breaking force.5.11 Tests on Oven-Dried Specimens and Spe
43、cimens at HighTemperaturesTests on oven-dried specimens at standard orhigh temperatures are usually made only on yarns that will beused at high temperatures or will be used under very dryconditions which will affect the observed breaking force, forexample, on rayon yarns intended for use in tire cor
44、ds andyarns for other industrial purposes. Note that results obtainedwhen testing oven-dried specimens at standard temperaturewill not necessarily agree with the results obtained whentesting oven-dried yarns at high temperatures.5.12 Tests on Specimens at Low TemperaturesTests onspecimens exposed to
45、 low temperatures are usually made onlyon yarns that will be used at low temperatures, for example,yarns used in outerwear designed for cold climates or outer-space situations. Low-temperature tests are made on coatedyarns used in the manufacture of materials used in outdoorapplications, such as scr
46、eening fabrics.6. Apparatus and Reagents6.1 Tension Testing Machine, of the CRE, CRL, or CRTtype, conforming to Specification D 76, with respect to forceindication, working range, capacity, and verification of re-corded elongation, and designed for operation at the ratesspecified in 9.1. A variable-
47、speed drive, a change of gears, orinterchangeable weights are required to obtain the 20-s time-to-break. If the rate of operation is adjusted in steps, the stepsshould be no greater than 1.25:1.00. The tension testingmachine may be equipped with: (1) clamps having flat-facedjaws or (2) capstan-, dru
48、m-, or snubbing-type clamps (Note 5).Automatic (self-loading and recording) single-end tensiontesting machines may be used, provided they meet the require-ments as to gage length, rate of operation, and accuracy ofcalibration. The tension testing machine may be interfacedwith a computer system for o
49、peration and data gathering. TheCRE-type tension testing machine is recommended unlessotherwise agreed upon between the purchaser and the supplier.NOTE 4Test machines capable of both tension and compression areacceptable for use with Test Method D 2256 when operated in the tensionmode.NOTE 5Flat-faced clamps are usually used with fine yarns. Thesnubbing-type clamps are used with coarse yarns or yarns that show a highbreaking force. They are also used when specimens slip in the clamps orthe number of breaks at or close to the jaws exceeds statistical expecta-tions.T
