1、Designation: D7811 13Standard 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. A number in pare
2、ntheses 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 This test method
3、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 withD3882 may not be
4、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 thesafety concerns, if an
5、y, 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:2D123 Terminology Relating to TextilesD1776 Practic
6、e 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 Conducting an Interlaboratory Study toDetermine the Precision of
7、 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 fabric, skew, standard atmosphere for testingtextiles.3.2 F
8、or 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 designated design meets the two selvagesor edges. The greatest
9、 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 forobtaining data for research and development, quality control,ac
10、ceptance 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 environments inuse.5.3 This test method is considered satisf
11、actory 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 astatistical bias between them, using competent statistical assis
12、-tance. As a minimum, the test samples to be used are ashomogeneous as possible, are drawn from the material fromwhich the disparate test results 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 thisp
13、urpose. The test results from the two laboratories should becompared using a statistical test for unpaired data, at aprobability level chosen prior to the testing series. If a bias is1This test method is under the jurisdiction of ASTM Committee D13 on Textilesand is the direct responsibility of Subc
14、ommittee D13.60 on Fabric Test Methods,Specific.Current edition approved July 1, 2013. Published August 2013. DOI: 10.1520/D7811-13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume inform
15、ation, 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 States1found, either its cause must be found and corrected, or futuretest results must be adjusted in consideration of the
16、 knownbias.5.5 Bow or skew can be induced during fabricmanufacturing, dyeing, tentering, finishing, or other operationswhere a potential exists for uneven distribution of tensionsacross the fabric width. Bow and skew are more visuallydispleasing in colored, patterned fabrics such as plaids andhorizo
17、ntal stripes rather than in solid colors because thecontrast makes the distortion more prominent. These defectsmay cause sewing problems in such fabrics and drapingproblems in finished products. Wavy or sharp breaks in the bowline are more detrimental to the appearance of small specimensof a sewn as
18、sembly.6. Apparatus6.1 Millimeter Rule, graduated in 1-mm (116-in.) divisions.6.2 Test FixtureSee Fig. 1 and Fig. 3. This tool, hereafterreferred 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
19、 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 to lay the test specimen.6.5 Fabric Inspection Table (Optional) with suffcientlighting, for fabric on rolls or bolts.7. Interferences7.1 None identified.8. S
20、ampling8.1 When testing fabric in rolls, consider rolls to be theprimary sampling units and select at least three areas from eachroll for testing, 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
21、.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 randomly 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
22、. 3dimensions by using scale or rule traceable to NIST orequivalent national standard.10. Conditioning10.1 Condition the test specimens to moisture equilibriumfor testing in the standard atmosphere for testing textiles inaccordance with Practice D1776 or, if applicable, in thespecified atmosphere in
23、 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 facilities,perform the test without conditioning and report the actualcondition prevailing at the time of the test. Such results maynot correspond with the
24、results obtained when testing afterconditioning.10.3 Testing is to be conducted in an environment of 23 62 C and 50 6 5 % relative humidity.FIG. 1 Bow Skew Tool with Open SlotD7811 132FIG. 2 Bow Skew Tool with Open Slot Lined Up to MaterialFIG. 3 Bow Skew Tool with Open SlotsDimensionedD7811 13310.4
25、 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 conditioned 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
26、 the environment outlined in 10.3, note actual environmen-tal conditions at the time of testing.11. Procedure AUsing the Tool on Rolled 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 t
27、he Bow and Skew MeasurementTool to the selvage edge of the material (selvage may curveaway from Line AB match points A repeat steps 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
28、 Bow andSkew Measurement Tool to measure the distance of the fill lineor pattern from line CD at point D (if bow is the major effect).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
29、 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,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
30、Skew is tobe measured over).12.9 Position the Bow and Skew Measurement Tool on thecut specimen so that line AB follows the new warp 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 obtainedwit
31、hin one laboratory shall be judged not equivalent if theydiffer by more than the “r” value for that material; “r”istheinterval representing the critical difference between two testresults for the same material, obtained by the same operatorusing the same equipment on the same day in the samelaborato
32、ry.16.1.1.1 Repeatability limits are listed in Table 1.16.1.2 Reproducibility limit (R)Two test results shall bejudged not equivalent 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,obt
33、ained by different operators using different equipment indifferent laboratories.16.1.2.1 Reproducibility limits are listed in Table 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.
34、1and 16.1.2 would have an approximate 95 % probability ofbeing correct.16.2 BiasAt the time of the study, there was no acceptedreference 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 dat
35、a, thisprecision statement was determined through the statisticalexamination of 144 test results, from six laboratories, on sixfabrics which were described as:Sample A flame laminated knitted seating fabricSample B unlaminated knitted seating fabricSample C unlaminated knitted seating fabricSample D
36、 laminated knitted seating fabricSample E laminated knitted seating fabricSample F laminated knitted seating fabric16.4 If using the 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
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41、t the aboveaddress 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/).4Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D13-1137. ContactASTM CustomerService at serviceastm.org.D7811 136
