1、Designation: D7811 13 (Reapproved 2017)Standard Test Method forBow and Skew Using a Measuring Tool1This standard is issued under the fixed designation D7811; 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 () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method is used to determine the bow and skewof woven and knitted fabrics over a fixed distance, using ameasuring tool.1.2
3、 This test method is useful when a small specimen or cutparts need to be evaluated for bow and skew, provided a warpor fill, or both, reference line is available, to aid in aligning thetool.1.3 Test Method D3882 may be used when measuring bowand skew in fabric in rolls. However, results obtained wit
4、hD3882 may not be comparable with results obtained by this testmethod.1.4 There is no known ISO equivalent standard.1.5 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.6 This standard does not purport to address all of thesafe
5、ty concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety, health and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.7 This international standard was developed in accor-dance
6、 with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Stand
7、ards:2D123 Terminology Relating to TextilesD1776 Practice for Conditioning and Testing TextilesD3882 Test Method for Bow and Skew in Woven andKnitted FabricsD3990 Terminology Relating to Fabric DefectsE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE691 Practice for Conducti
8、ng an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 For all terminology related to fabric defect terms, referto Terminology D3990.3.1.1 The following terms are relevant to this standard: bow,double bow, double hooked bow, double reverse bow, hookedbow, knitted fab
9、ric, skew, standard atmosphere for testingtextiles.3.2 For all other terminology related to textiles, refer toTerminology D123.4. Summary of Test Method4.1 A straightedge is placed across the fabric between twopoints at which a marked filling yarn, knitted course, desig-nated printed line, or design
10、ated design meets the two selvagesor edges. The greatest distance between the straightedge andthe marked filling line, knitted course, designated printed line,or designated design is measured parallel to the selvage.5. Significance and Use5.1 This test method provides a standard procedure forobtaini
11、ng data for research and development, quality control,acceptance and rejection under specifications, and for specialpurposes.5.2 The data obtained by this test method is applicable to thematerial under the conditions of this particular test and is notnecessarily the same as obtained under other envi
12、ronments inuse.5.3 This test method is considered satisfactory for accep-tance testing of commercial shipments.5.4 If there are differences of practical significance betweenreported test results for two laboratories (or more), compara-tive tests should be performed to determine if there is astatisti
13、cal bias between them, using competent statistical assis-tance. As a minimum, the test samples to be used are as1This test method is under the jurisdiction of ASTM Committee D13 on Textilesand is the direct responsibility of Subcommittee D13.60 on Fabric Test Methods,Specific.Current edition approve
14、d July 15, 2017. Published August 2017. Originallyapproved in 2013. Last previous edition approved in 2013 as D7811-13. DOI:10.1520/D7811-13R17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards v
15、olume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on st
16、andardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1homogeneous as possible, are drawn from the material fromwhich the disparate test resu
17、lts were obtained, and are ran-domly assigned in equal numbers to each laboratory for testing.Other fabrics with established test values may be used for thispurpose. The test results from the two laboratories should becompared using a statistical test for unpaired data, at aprobability level chosen
18、prior to the testing series. If a bias isfound, either its cause must be found and corrected, or futuretest results must be adjusted in consideration of the knownbias.5.5 Bow or skew can be induced during fabricmanufacturing, dyeing, tentering, finishing, or other operationswhere a potential exists
19、for uneven distribution of tensionsacross the fabric width. Bow and skew are more visuallydispleasing in colored, patterned fabrics such as plaids andhorizontal stripes rather than in solid colors because thecontrast makes the distortion more prominent. These defectsmay cause sewing problems in such
20、 fabrics and drapingproblems in finished products. Wavy or sharp breaks in the bowline are more detrimental to the appearance of small specimensof a sewn assembly.6. Apparatus6.1 Millimeter Rule, graduated in 1-mm (116-in.) divisions.6.2 Test FixtureSee Fig. 1 and Fig. 3. This tool, hereafterreferre
21、d to as “bow and skew measurement tool” is to be usedfor each measurement.6.2.1 Fig. 3 is a dimensioned drawing of bow and skewmeasurement tool.6.3 Bow Skew Measurement Tool Construction:6.3.1 Transparent material such as polycarbonate.6.3.2 Thickness 3 to 5 mm.6.4 Flat Surface, of sufficient area t
22、o lay the test specimen.6.5 Fabric Inspection Table (Optional) with suffcientlighting, for fabric on rolls or bolts.7. Interferences7.1 None identified.8. Sampling8.1 When testing fabric in rolls, consider rolls to be theprimary sampling units and select at least three areas from eachroll for testin
23、g, excluding the first and last fifth of the roll.Select areas for testing at random, and no closer to one anotherthan one fifth of the length of the roll.8.2 For cut parts of sufficient size for testing (i.e. at least 400mm in length), consider each part a test specimen, and test atleast three rand
24、omly chosen specimens.9. Calibration and Standardization9.1 Bow and Skew Measurement Tool Calibration:9.2 Bow Skew Measurement Tool is to be verified to Fig. 3dimensions by using scale or rule traceable to NIST orequivalent national standard.10. Conditioning10.1 Condition the test specimens to moist
25、ure equilibriumfor testing in the standard atmosphere for testing textiles inaccordance with Practice D1776 or, if applicable, in thespecified atmosphere in which the testing is to be performed.10.2 When full rolls or bolts of fabric cannot be properlyconditioned in a reasonable time with available
26、facilities,perform the test without conditioning and report the actualFIG. 1 Bow Skew Tool with Open SlotD7811 13 (2017)2condition prevailing at the time of the test. Such results maynot correspond with the results obtained when testing afterconditioning.10.3 Testing is to be conducted in an environ
27、ment of 23 62 C and 50 6 5 % relative humidity.FIG. 2 Bow Skew Tool with Open Slot Lined Up to MaterialFIG. 3 Bow Skew Tool with Open SlotsDimensionedD7811 13 (2017)310.4 Condition test specimens for 24 h in an environment of23 6 2 C and 50 6 5 % relative humidity.10.5 If test specimens are conditio
28、ned for less than 24 h, orunder different conditions, note and report the alternativetimes/conditions used.10.6 If the test specimen is tested in an environment otherthan the environment outlined in 10.3, note actual environmen-tal conditions at the time of testing.11. Procedure AUsing the Tool on R
29、olled Goods11.1 Start by positioning the Bow and Skew MeasurementTool (reference Fig. 1 and Fig. 2) to the far left side of theunrolled material.11.2 Line up line AB on the Bow and Skew MeasurementTool to the selvage edge of the material (selvage may curveaway from Line AB match points A repeat step
30、s 12.2 and 12.3 as needed.12.5 Follow the fill line or pattern from point C to point Don the Bow and Skew Measurement Tool.12.6 Use the integrated scale at point D on the Bow andSkew Measurement Tool to measure the distance of the fill lineor pattern from line CD at point D (if bow is the major effe
31、ct).If skew is the major effect, measure at the farthest point fromline CD using the integrated scale in the center of the tool.12.7 Record the data.312.7.1 The scale has 1-mm increments grouped in sectionsof 5 mm each totaling 620 mm from Line CD).12.8 If the specimen is between 500 and 800 mm wide
32、,move the Bow and Skew Measurement Tool to the right so thatpoint C is now located where point D was previously (Line CDis 400 mm which is the dimension that the Bow and Skew is tobe measured over).12.9 Position the Bow and Skew Measurement Tool on thecut specimen so that line AB follows the new war
33、p line. Thewarp line may curve away from Line AB match points A the details are given inan ASTM Research Report416.1.1 Repeatability limit (r)Two test results obtainedwithin one laboratory shall be judged not equivalent if theydiffer by more than the “r” value for that material; “r”istheinterval rep
34、resenting the critical difference between two testresults for the same material, obtained by the same operatorusing the same equipment on the same day in the samelaboratory.16.1.1.1 Repeatability limits are listed in Table 1.16.1.2 Reproducibility limit (R)Two test results shall bejudged not equival
35、ent if they differ by more than the “R” valuefor that material; “R” is the interval representing the criticaldifference between two test results for the same material,obtained by different operators using different equipment indifferent laboratories.16.1.2.1 Reproducibility limits are listed in Tabl
36、e 1.16.1.3 The above terms (repeatability limit and reproduc-ibility limit) are used as specified in Practice E177.16.1.4 Any judgment in accordance with statements 16.1.1and 16.1.2 would have an approximate 95 % probability ofbeing correct.16.2 BiasAt the time of the study, there was no acceptedref
37、erence material suitable for determining the bias for this testmethod, therefore no statement on bias is being made.16.3 Following the exclusion of identified outlier data, thisprecision statement was determined through the statisticalexamination of 144 test results, from six laboratories, on sixfab
38、rics which were described as:Sample A flame laminated knitted seating fabricSample B unlaminated knitted seating fabricSample C unlaminated knitted seating fabricSample D laminated knitted seating fabricSample E laminated knitted seating fabricSample F laminated knitted seating fabric16.4 If using t
39、he data shown in Table 1, select a fabric typethat is closest in characteristics to the material being tested.17. Keywords17.1 bow; fabric; knitted fabric; measuring tool; skew;woven fabricASTM International takes no position respecting the validity of any patent rights asserted in connection with a
40、ny 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 entirely their own responsibility.This standard is subject to revision at any time by the responsible technica
41、l 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 standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration
42、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 Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor
43、 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 or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.as
44、tm.org). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D13-1137. ContactASTM CustomerService at serviceastm.org.D7811 13 (2017)6
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