1、INTERNATIONAL STANDARD ISO 16549 First edition 2004-06-01 Reference number ISO 16549:2004(E) ISO 2004 Textiles Unevenness of textile strands Capacitance method Textiles Irrgularit des fils textiles Mthode capacitiveISO 16549:2004(E) ii ISO 2004 All rights reserved PDF disclaimer This PDF file may co
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6、t office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in SwitzerlandISO 16549:2004(E) ISO 2004 All rights reserved iii Contents Page 1 Scope 1 2 Normative references 1 3 Terms and definitions 1 4 Principle 2 5 Appara
7、tus . 3 6 Atmosphere for conditioning and testing . 4 7 Sampling . 4 8 Procedure . 5 9 Calculations and expression of results . 6 10 Test report 6 Annex A (informative) Other methods for the determination of unevenness . 8 Bibliography . 10ISO 16549:2004(E) iv ISO 2004 All rights reserved Foreword I
8、SO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical c
9、ommittee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electr
10、otechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the m
11、ember bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identi
12、fying any or all such patent rights. ISO 16549 was prepared by Technical Committee ISO/TC 38, Te x t i l e s, Subcommittee SC 23, Fibres and yarns. This International Standard cancels and replaces ISO 2649 which is now obsolete.ISO 16549:2004(E) ISO 2004 All rights reserved v Introduction In the 196
13、0s the International Wool Textile Organization (IWTO) prepared an unevenness method destined for yarns and other strands made of wool. The method was adopted by ISO as ISO 2649:1974. It contains a discussion of the principles of unevenness testing and refers to the then-popular unevenness tester, th
14、e 1960s model of the Uster Evenness Tester, which was obsolete in mid-2000 when the present International Standard was written. Later, the IWTO prepared a new method, IWTO-18-00, published in 2000. ISO 16549 has mostly new wording but includes some elements of ISO 2649 and of IWTO-18-00 with thanks
15、to IWTO vi INTERNATIONAL STANDARD ISO 16549:2004(E) ISO 2004 All rights reserved 1 Textiles Unevenness of textile strands Capacitance method 1S c o p e This International Standard describes a method, using capacitance measuring equipment, for determining the unevenness of linear density along the le
16、ngth of textile strands. The method is applicable to tops, slivers, rovings, spun yarns and continuous filament yarns, made from either natural or man-made fibres, in the range of 4 tex ( ) to 80 ktex ( ) for staple-fibre strands and 1 tex ( ) to 600 tex ( ) for continuous-filament yarns. It is not
17、applicable to fancy yarns or to strands composed fully or partly of conductive materials such as metals; the latter require an optical sensor (see A.4). The method describes the preparation of a variance-length curve, as well as the determination of periodicities of linear density. It covers also th
18、e counting of imperfections in the yarn, namely of neps and of thick and thin places. Irregularities in the distribution of additives such as sizes, in moisture content and in fibre blending may increase the measured unevenness above its true value. 2 Normative references The following referenced do
19、cuments are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 139, Te x t i l e s Standard atmospheres for conditioning and testing 3
20、Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 unevenness variation of linear density along the length of a continuous strand or yarn NOTE The term is also used occasionally for the variation of yarn diameter. 3.2 coefficient-of-variation unev
21、enness value of unevenness (3.1) expressed as a coefficient of variation NOTE 1 The coefficient-of-variation unevenness is expressed in percent, for example . NOTE 2 See also 4.5 and 4.6. 3.3 mean-deviation unevenness value of unevenness (3.1) expressed as an average mean deviation NOTE 1 The mean-d
22、eviation unevenness is expressed in percent, for example, . g/km kg/km g/km g/km CV u CV u = 18,3 % U u U u = 14,6 %ISO 16549:2004(E) 2 ISO 2004 All rights reserved NOTE 2 See also 4.5 and 4.6. 3.4 capacitor length effective length of the capacitor in the direction of the specimen movement, usually
23、to 3.5 length between length of the test specimen for which the instrument takes an individual reading of mass NOTE 1 The unevenness value decreases as is increased. NOTE 2 In the capacitance method, is normally the capacitor length but it can be increased electronically. NOTE 3 is sometimes referre
24、d to in the literature as . 3.6 length within length of the specimen for which an individual value of unevenness is determined and a reading is given NOTE 1 The unevenness value increases as is increased. When is more than or so, then a further lengthening of increases (or ) only slightly. NOTE 2 is
25、 sometimes referred to in the literature as . 3.7 total measured length sum of all measured lengths 3.8 nep tightly tangled knot-like mass of unorganized fibres 3.9 package yarn wound to a shape, which may be supported (for example, bobbins, cones) or unsupported (for example, skeins, cakes), suitab
26、le for conditioning and testing 3.10 spectrogram attachment to unevenness testers for the calculation and presentation of periodic variations in the strand 3.11 thick place yarn defect with linear density substantially (at least ) greater than that of the adjoining segments of the yarn and extending
27、 for at least 3.12 thin place yarn defect with linear density substantially (at least ) smaller than that of the adjoining segments of the yarn and extending for at least 4P r i n c i p l e 4.1 A specimen is passed between two plates of a capacitor causing changes in capacitance which are proportion
28、al to the changes of mass of the specimen. The instrument evaluates these changes and reports them as or . 8mm 20mm L b L b L b L b B L w L w L w 100 m L w CV u U u L w W L w 50 % 5mm 50 % 5mm CV u U uISO 16549:2004(E) ISO 2004 All rights reserved 3 4.2 The fibre dielectric constant is also a factor
29、 determining the capacitance change. As long as the dielectric constant is unchanging (non-blended strands or perfectly uniform blending), the dielectric constant has no influence on the unevenness reading, which depends solely on the variation of mass. If the dielectric constant differs for the typ
30、es of fibres in a blend and if, at the same time, the blend is irregular, then the reading of unevenness is increased above its true value. The interpretation of results therefore requires caution. 4.3 Several studies have been conducted over the years, see Reference 3 for example, comparing the tru
31、e unevenness of a specimen, determined by cutting and weighing (see A.3.1), with the reading from an unevenness tester. Good agreement was obtained, so the readings from the tester can be taken as being the true unevenness value. 4.4 The value of unevenness has meaning only if both and are known and
32、 they should, in principle, always be reported, preferably as ( , ). EXAMPLE ( , ). In practice, these two values are usually left unstated and are assumed to be those of the most commonly used unevenness tester, namely : for yarns, for rovings, for slivers and tops; : total length of yarn on the pa
33、ckage. 4.5 There are two possible expressions for unevenness, and . The is now obsolete and its use, while permitted, is discouraged. is the preferred expression. 4.6 If mass is distributed near to “normal”, then the ratio of is approximately 1,25. This conversion factor must be used cautiously beca
34、use, in case of departures from normality, the ratio can be considerably different. The conversion factor may be used to convert a table of quality levels from to . 4.7 When is plotted against , a “variance-length curve” is obtained which gives additional information on the materials unevenness. Whe
35、n the plot is made on log-log paper, then the curve is almost a straight line and its slope gives information on the relationship between short-term and long-term unevenness. 4.8 Unevenness testers usually contain a spectrogram, which analyses the data and provides information on periodic variations
36、 of linear density. This information is useful in finding faults in the processing. The analysis uses an algorithm based on the Fourier transformation. 4.9 Unevenness testers usually contain a counter for yarn imperfections, namely neps, and thick and thin places. The level beyond which the imperfec
37、tions are counted can be adjusted. 4.10 Unevenness is a fundamental feature of yarn construction. It influences the efficiency of processing as well as fabric appearance. Lower unevenness generally results in a better-looking fabric but the relation is not simple and interpretation requires special
38、care. 5 Apparatus 5.1 Different types of apparatus are in use for measuring strands made of staple fibres and filament yarns. 5.2 The apparatus consists of the following elements: a) measuring device, featuring several measuring condensers, usually grouped into one unit, for strands of varying linea
39、r density, yarn guiding and pretensioning devices, an adjustable-speed motor to advance the strand; L b L w CV u L b L w CV u 10 mm 1 000 m L b 8mm 12mm 20mm L w CV u U u U u CV u CV u /U u U u CV u CV u L bISO 16549:2004(E) 4 ISO 2004 All rights reserved b) signal processing unit, which computes an
40、d indicates the values of or and may also calculate the variance-length curve and present a graph of the periodic variations of linear density, also counts the number of imperfections in most instruments. The unit shall be able to operate at the threshold level of , above which thick places are coun
41、ted, and the level of , below which thin places are counted. reports a reading for neps which shall be a product of the length, expressed in millimetres, of the nep and the percent excess over the average linear density of the yarn (for example, ). The level of , above which neps are counted, shall
42、be available. other levels (for the three imperfection types) are also usually available; c) printer (optional), which provides a plot of the linear density of the strand; d) twisting device for testing untwisted or low-twist filament yarns. This device produces false twist in an untwisted or low-tw
43、ist filament yarn, so that the yarn presents a nearly round cross-section as it passes through the condenser. If the yarn passes through in a flat mode, there is the danger of adding variation depending on the way the flat yarn is presented. The direction of the imparted false twist must be the same
44、 as that of any twist present in the yarn. The twisting device need not be used for the testing of monofilaments. 5.3 To calibrate, use the procedure built into the instrument if possible. Alternatively, use a standard (usually tape) of known unevenness provided by the instrument manufacturer and fo
45、llow the manufacturers instructions. Finally, if the manufacturers standard is not available, an in-house material of known and preferably low unevenness, may be used. 6 Atmosphere for conditioning and testing The standard atmosphere for preconditioning, conditioning and testing shall be as specifie
46、d in ISO 139. Assure that the total length of the material to be tested is in moisture equilibrium. Conditioning for is usually sufficient for unsupported packages. Supported packages shall be conditioned for . 7 Sampling 7.1 Select laboratory samples in one of the following two ways: according to a
47、 material specification, if available; by agreement between the parties. 7.2 The following minimum numbers of packages are recommended: tops and slivers: 3 packages; rovings: 4 packages; staple-fibre yarns: 10 packages; filament yarns: 5 packages. 7.3 The material shall be unwound directly from the
48、package during testing so as to avoid possible deformation during handling. 7.4 Test the number of specimens per package given in the material specification. If no specification is available, test one specimen per package. CV u U u + 50 % 50 % 4mm 50 % + 200 % 24 h 48 hISO 16549:2004(E) ISO 2004 All
49、 rights reserved 5 7.5 Test the following lengths of test specimens. These are minimum values for the total measured length. tops and slivers: ; rovings: ; staple-fibre yarns: ; filament yarns: . 8 Procedure 8.1 Setting of the apparatus If the tester allows a choice between a “normal” and an “inert” test, perform the “normal” test and then the “inert” if desired to establish the variance-length curve. The “normal” choice for some testers will result in the performanc
