1、Designation: D2821 09Standard Test Method forMeasuring the Relative Stiffness of Leather by Means of aTorsional Wire Apparatus1This standard is issued under the fixed designation D2821; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisio
2、n, the 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 descr
3、ibes the use of a torsionalapparatus for measuring the relative stiffness of gloving leath-ers. This test method does not apply to wet blue.1.2 The values stated in SI units are to be regarded as thestandard. The values shown in parentheses are provided forinformation only.1.3 This standard does not
4、 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. Referenced Documents2.1 ASTM Standards
5、:2D1053 Test Methods for Rubber PropertyStiffening atLow Temperatures: Flexible Polymers and Coated FabricsD1610 Practice for Conditioning Leather and Leather Prod-ucts for Testing3. Significance and Use3.1 This test method is designed to measure the apparenttorsional modulus3of a leather specimen.
6、Experience hasshown that the torsion modulus of leather is directly related tothe characteristic known as stiffness when felt in a glove.44. Apparatus4.1 Torsion Apparatus5The torsional apparatus, Fig. 1,shall consist of a torsion head, A, capable of being turnedthrough a complete circle in a plane
7、normal to the torsion wire,N. The torsion head is equipped with an upper dial orprotractor, K, graduated from 0 to 360 in increments notgreater than 5, and a fixed index pointer, L. The protractor isattached to the torsion head by means of a friction bearing topermit movement for adjusting the zero
8、point. The top of thetorsion wire is attached to the torsion head at knob H by setscrew B and passes through the center of a loosely fitting sleevegripped by the friction bearing. The torsion head supportcarries a split bearing which can be activated by knob G, thuslocking the sleeve carrying the wi
9、re and permitting adjustmentof the zero point of the protractor without disturbing theposition of the torsion wire. The bottom of the wire shall befastened to the test specimen clamp, C, by means of a set screwconnector, D. A pointer, I, mounted above a fixed dial, J, shall1This test method is under
10、 the jurisdiction of ASTM Committee D31 on Leatherand is the direct responsibility of Subcommittee D31.04 on Apparel. This testmethod was developed in cooperation with the American Leather Chemists Assn.Current edition approved Oct. 1, 2009. Published December 2009. Originallyapproved in 1969 as D28
11、21 69T. Last previous edition approved in 2005 asD2821 00(2005)1. DOI: 10.1520/D2821-09.2For referenced 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 Summa
12、ry page onthe ASTM website.3This test method is similar to Test Method D1053. The original apparatus wasdescribed by Williamson, I., British Plastics, Vol 23, 1950, pp 87-90, 102; andtypical examples of the results of its use on leather were given in a paper byWitnauer, L. PA, and Palm, W.E., Journa
13、l, American Leather Chemists Assn.,JALCA, Vol 59, 1964, pp. 246-258.4Gloves were made from the neck and butt areas of cattlehide work-gloveleather selected for 3 of softness varying from soft to firm. These were ranked fromsoftest to firmest by 20 individuals. Since there was some overlapping of ran
14、k asassigned by individual observers, the final rank was assigned according to highestnumber of selections. Specimens of leather cut from the sides in the area from whicheach glove was cut were tested for stiffness according to this test method. At 90 oftwist, the stiffness values gave a ranking sim
15、ilar to that obtained by feel. Specimenscut parallel to the backbone gave more consistent ranking than specimens cutperpendicular to the backbone. This undoubtedly reflects the fact that work glovesare cut from a side with the fingers parallel to the backbone. A report of theseexperiments and data u
16、sed for calculation of precision and accuracy are on file atASTM Headquarters.5The sole source of supply of the apparatus known to the committee at this timeis Taber Industries, 455 Bryant Street, North Tonawanda, NY, 14120. If you areaware of alternative suppliers, please provide this information t
17、o ASTM Interna-tional Headquarters. Your comments will receive careful consideration at a meetingof the responsible technical committee, which you may attend.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.be provided to indicate the
18、 twist applied to the specimen.Torsion is applied by manually turning knob H or the remotecontrol knob M.4.2 StandThe torsion apparatus shall be mounted on arigid supporting stand, O.4.3 Torsion Wires6Torsion wires shall be made of tem-pered spring wire 315 mm (12.5 in.) long, with each end firmlyaf
19、fixed within a rod measuring 5 mm (316 in.) in diameter and12.5 mm (12 in.) long so as to give a free length between therods of 290 6 2.5 mm (11.5 6 0.1 in.).4.4 Specimen ClampsTwo clamps shall be provided forholding each test specimen. The top clamp, C, shall bemounted at the bottom of the torsion
20、wire. The bottom clamp,E, shall be fashioned to move up and down without bindingwithin guides, F, mounted in the base. The weight of bottomclamp E shall be 15 6 0.01 g.5. Test Specimens5.1 Unless otherwise specified in the detailed specification,cut the specimen using a sharp die measuring 12.70 6 0
21、.03 mm(0.5006 0.001 in.) wide and 114 6 2 mm (4.5 6 0.1 in.) long.When known the direction to the backbone shall be indicated.It is good practice, however, to include a control specimen withknown twist characteristics.5.2 Condition the specimen as specified in Practice D1610.6. Preparation of Appara
22、tus6.1 Clamp the specimen in the testing apparatus as de-scribed below so that 89 6 2 mm (3.5 6 0.1 in.) of thespecimen is free between the clamps. It is advisable to markthis distance on the specimen using a bench marker.6.2 Insert the specimen into the jaws of the bottom clamp,E, until the edge of
23、 the clamp meets the bench mark. Be surethe specimen is perpendicular to the jaws of the clamp.6.3 Insert the other end of the specimen into the jaws of theupper clamp, C, up to the bench mark. Be sure the specimen isperpendicular to clamp.6.4 Insert the bottom clamp into the clamp guide, F.6.5 Unlo
24、ck the top dial by turning knob G counterclockwiseabout14 turn.6.6 Bring both clamps into parallel position by turning knobH, or knob M, either clockwise or counterclockwise so there isno twist to the specimen. When the clamps are parallel adjustthe top clamp indicator, I, so it is over the “0” mark
25、 on thelower dial, J, by holding the clamp parallel in one hand andturning the indicator. The indicator is attached to the upperclamp by a friction clasp.6.7 Lock the top dial, K, by turning knob G clockwise untiltight.6.8 Set the top dial by actually turning dial K to read 270(top dial is tension f
26、itted).NOTE 1By setting the dial to 270, the 90 twist of the specimen willbe subtracted out automatically, and the readings obtained will be that ofthe wire to give the desired 90 twist of the specimen.NOTE 2When setting top dial care should be taken not to twist thewire, causing the top clamp indic
27、ator to move. Movement of the indicatormeans that knob G was not tightened sufficiently. If this happens repeatoperations 6.5-6.8 as may be necessary.NOTE 3Dial K is attached to knob H through a friction bearing, thuspermitting dial K to be adjusted while the wire, which is attached to knobH, is in
28、a locked position when knob G is tight. Loosening knob G permitsknob H and dial K to be turned freely as a unit.NOTE 4The procedure outlined here is for testing of specimens at 90twist. If in the detailed specification, other degrees of angular twist arespecified, then the preflexing cycles and the
29、final measurement shall bemade at the specified degree of twist. The zero shall be adjusted to read360 minus the specified degrees of angular twist, and the torsion valueswill become corrected for the new value.7. Procedure7.1 Preflex the specimen by applying the same degree ofangular twist as speci
30、fied for the test through a minimum oftwo cycles as detailed below.7.2 Loosen knob G and turn the top dial, K, using knob H orknob M, slowly in a counterclockwise direction until the upper6The original torsion wire was a stainless steel rocket wire, Type NS-302, 0.0106 0.0025 in. (0.025 6 0.06 mm) i
31、n diameter, bright finish, with chemicalcomposition of 0.08 to 0.12 % carbon, 8 to 10 % nickel, and 17 to 19 % chromium,from National Standard Co., http:/. If other wire is used,it should be calibrated as described in Test Method D1053 and have a constant of0.0182 gcm/deg.FIG. 1 Torsion ApparatusD28
32、21 092clamp indicator, I, shows that the specimen has been twisted90 (see Note 4). (Try to keep a uniform rate that will takeabout 4 to 5 s/90. The use of the remote control knob M isrecommended as it permits a more uniform application oftwist.)7.3 Reverse rotation to the clockwise direction and con
33、tinuerotating slowly until the specimen clamp indicator I has passedthe original reference line indicated on the lower dial J byapproximately 45. Reverse the direction of rotation again andslowly realign the specimen clamp indicator I with the originalreference line indicated on lower dial, J.7.4 If
34、 the upper dial does not read 270 (see Note 4), tightenknob G and bring the upper dial to 270 by actually turning dialK.7.5 Repeat steps 7.2-7.4 for one more cycle. This completesthe preflexing operation.7.6 Loosen knob G and again turn upper dial K using knobH or knob M, slowly and in a countercloc
35、kwise direction, untilthe specimen clamp indicator, I, shows a 90 twist (see Note 4).7.7 Read from the upper dial, K, the angle of torsion andrecord this value to the nearest 5.NOTE 5Torsion values can be obtained at several increments ofangular twist on the same specimen without removing it from th
36、eapparatus. If torsion measurements are to be made at more than oneincrement of angular twist, it is advisable to make the first torsionmeasurement at the lowest degree of twist and proceed with the increasingincrements in consecutive order. When this is done it is essential that thespecimen be pref
37、lexed for two cycles at each increment of angular twist.NOTE 6Excessively high values may be due to either (a) overshootingthe end point from turning the dial too rapidly; ( b) the specimen is notperpendicular to clamp jaws and causes bottom clamp to bind; or (c)neglecting to reset zero point betwee
38、n the second preflexing cycle and thefinal reading.NOTE 7Excessively low values, especially at higher degrees of twistmay be caused by inadvertently stopping the specimen at 90 instead ofgoing to the higher order.7.8 Release the specimen from the top clamp.7.9 Remove the bottom clamp from the guide
39、and releasethe specimen.8. Report8.1 The report shall include the following:8.1.1 Complete identification of the material tested includ-ing type, source, manufacturers code designation, form, datemade, etc.8.1.2 Direction to backbone.8.1.3 Dimensions of test specimen, details of conditioningof speci
40、mens prior to test, and torsional constant of torsionwire used.8.2 Report torsion to the nearest 5, and indicate the angulartwist applied to the specimen.9. Precision and Bias9.1 The precision of the test method is largely limited by thespecimen to specimen variation in such a complex material aslea
41、ther.9.1.1 At the 95 % confidence level, repeat determinationson a single specimen made singly by the same operator ondifferent days should not differ by more than 13 % of thelowest value.9.1.2 At the 95 % confidence level, single determinationsmade at different laboratories on the same specimen sho
42、uld notdiffer by more than 23 % of the lowest value.10. Keywords10.1 glove leather; stiffnessAPPENDIX(Nonmandatory Information)X1. HISTORICAL INFORMATIONX1.1 Lengths of the standard wire can be obtained atnominal cost from ASTM International Headquarters. Originaladjunct produced in 1975.7X1.2 Worki
43、ng drawings for the apparatus are available atnominal cost from ASTM International Headquarters. Originaladjunct produced in 1985.8X1.2.1 Original instrument design is shown in Fig. X1.1.7Available from ASTM Headquarters. Order ADJD282101.8Available from ASTM Headquarters. Order ADJD282102.D2821 093
44、ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are
45、 entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standar
46、dsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committ
47、ee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress
48、or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).FIG. X1.1 Original instrument manufactured by Fulton CountyMachine and Supply Co., Inc.D2821 094
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