GB/T 3292.1-2008 English PDF (GB/T3292.1-2008)

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GB/T 3292.1-2008: Textiles -- Unevenness of textile strands -- Part 1: Capacitance method
GB/T 3292.1-2008
Textiles - Unevenness of textile strands - Part 1.Capacitance method
ICS 59.080.20
W04
National Standards of People's Republic of China
GB/T 3292.1-2008
Replace GB/T 3292-1997
Test method for textile yarn unevenness
Part 1.Capacitance method
(ISO 16549.2004, Textiers-Unevennessof-Textiers-
Capacitance measurement, MOD)
2008-06-18 released
Implementation of.2009-03-01
General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China
Issued by the National Standardization Administration of China
Test method for textile yarn unevenness
Part 1.Capacitance method
1 Scope
This part of GB/T 3292 stipulates that the line density shall be measured along the length of the yarn (including spun yarn, roving and sliver) with a capacitive evenness tester.
The method of degree of unevenness.
This section applies to staple fiber yarns and continuous chemical fiber filament yarns. For short fiber yarns, the test range is from 4tex～
For 80ktex, the testing range for filament yarns ranges from 10dtex to 1670dtex. This section does not apply to fancy yarns and conductive materials (such as
The latter can be measured by photoelectric method (see Part 2 of GB/T 3292).
This section describes the generation process of the coefficient of variation-length curve, as well as the method of determining the periodic variation of linear density. This part
It also includes counts of yarn defects (ie, details, thick knots, and neps).
2 Normative references
The clauses in the following documents become clauses of this part through the reference of this part of GB/T 3292.All dated quotations
All subsequent amendments (not including errata content) or revisions do not apply to this section. However, it is encouraged to achieve
The parties to the agreement study whether the latest versions of these documents can be used. For undated reference documents, the latest version is applicable to this
part.
GB/T 6529 Standard atmosphere for textile humidity control and testing (GB/T 6529-2008, ISO 139.2005, MOD)
3 Terms and definitions
The following terms and definitions apply to this part of GB/T 3292.
3.1
The degree of uneven yarn density along the length of the yarn.
Note. This term is also often used to indicate the variation of yarn diameter.
3.2
C Ｍ
The percentage of the ratio of the standard deviation of the yarn linear density to the average linear density within the total test length.
3.3
Um
Within the cumulative test length, the total average of the absolute value of the difference between the linear density value of each point and the average linear density within the length and the total test length
The percentage of the ratio of the average linear density.
3.4
The effective length of the capacitor in the direction of movement of the specimen is usually 8 mm to 20 mm.
GB/T 3292.1-2008
3.5
Lb
Basically measure the length of the sample unit for unevenness of the test strip.
Note 1.The unevenness value between segments decreases as Lb increases.
Note 2.In the capacitance method, Lb is usually the length of the capacitance, but it can be increased electronically.
Note 3.Lb is sometimes expressed as B in references.
3.6
Lw
Test the total length of the uneven sliver.
Note 1.The unevenness value increases with the increase of Lw. When Lw exceeds about 100m, with the further increase of Lw, Cm only slightly changes.
Note 2.Lw is sometimes expressed by W in references.
3.7
One of the frequency domain representations of yarn linear density changes. The abscissa (logarithm) is the wavelength corresponding to the periodic unevenness, and the ordinate (linear) is
The relative average amplitude value of periodic unevenness expresses the periodic variation of the yarn.
3.8
Tightly entangle fiber knots, pellets, small balls, etc. that are difficult to loosen.
3.9
The linear density of the yarn increases to a certain extent and continues for more than 5mm.
3.10
The linear density of the yarn decreases to a certain extent and continues for more than 5mm.
3.11
Various yarn winding types suitable for testing (such as bobbins, cones, rovings, slivers, etc.).
3.12
One of the time-domain representations of yarn linear density changes. The abscissa indicates the length calculated from the starting end of the tested yarn sliver test.
The ordinate indicates the relative size of the linear density of the yarn to be tested.
3.13
Under normal circumstances, the value of Cm refers to the value of Cm for the length of the capacitor. The length of the measuring field is extended by the electronic method, and the calculation is not
Cm value under the same cutting length (this method corresponds to the early cutting weighing method). Constructed by several CV values under different cutting lengths
Become a coefficient of variation-length curve.
4 Principle
4.1 When the sample passes through the two capacitor plates, the rate of change of capacitance is linear with the rate of change of sample mass. The evenness meter calculates these
Change and use C m or Um to characterize.
4.2 Fiber dielectric constant is also a factor that determines the rate of change of capacitance. As long as the dielectric constant does not change (non-blended yarn or ideal
GB/T 3292.1-2008
Blending), the dielectric constant has no effect on the value of unevenness, and completely depends on the variation of quality. If the dielectric constant is due to the type of fiber in the blend
The type or mixing is irregular and different, then the unevenness value will be greater than the true value. Therefore, this difference in results requires attention.
4.3 Compared with the test results of the evenness tester, the unevenness value obtained by the cutting-weighing method has a high consistency. In recent years, other researches
This conclusion is also obtained, so the result of the evenness tester can be used as the true value of unevenness.
4.4 The unevenness value is only valid when both Lb and Lw are known. In principle, they are always reported together. A more preferable way of expression is
Cvm (Lb, Lw), such as Cvm (8mm, 1000m). In actual use, Lb and Lw are usually not marked, and the unevenness tester
The default is the most frequently used situation, that is.
---Lb. 8mm spun yarn, 12mm roving, 20mm sliver;
---Lw. The total length of the tested yarn in the package.
4.5 There are two ways of expressing the unevenness, Cmm and Um. Um has now been gradually abandoned, allowed but not encouraged to use, C Ｍ is recommended
Recommended representation method.
4.6 If the mass distribution is close to the normal distribution, the ratio of Cvm/Um is approximately 1.25.This conversion factor must be used with care, because
In order to deviate from the normal distribution, this ratio may be quite different.
4.7 When outputting the value of Cm under different cutting lengths, a "coefficient of variation-length curve" can be obtained, which gives information about the unevenness of the material.
Rate some additional information. When it is output through double logarithmic graph paper, the curve is almost a straight line, and its slope gives about
Information on the unevenness of short and long clips.
4.8 The test result of the unevenness tester usually contains a spectrogram, which provides information about the periodic variation of the linear density. According to this information, you can find
Process defects. Spectral analysis uses algorithms based on Fourier transform.
4.9 The test results of the unevenness tester usually include the number of yarn defects, that is, the count results of the neps, thick knots and detail counters.
4.10 Unevenness is a basic feature of yarn structure. It reflects production efficiency and fabric appearance. Lower unevenness usually produces more
Good-looking fabric, but it is not a simple equivalence relationship, and some other factors (such as uneven twisting, etc.) need to be considered.
5 devices
5.1 Different types of devices are used to test slivers composed of staple fiber and filament yarn.
5.2 The device consists of the following components.
a) Detection device, the components are.
---Several measuring capacitances, usually assembled into one unit, used to test yarns with different linear densities;
---Yarn guide and adjustable tensioner;
---The roller traction system that enables the yarn to pass through the detection device at a certain speed.
b) Signal processing unit.
---Calculate and display the value of C犞 m or Um, can also calculate the coefficient of variation-length curve, and provide the periodic variation of linear density
Graphics
---Calculate and display the defects of each file.
Note. Defects are usually divided into the following files.
Neps. +400%, +280%, +200%, +140%.
Thick sections. +100%, +70%, +50%, +35%.
Details. -60%, -50%, -40%, -30%.
c) Printer (optional).
---Provide yarn linear density index and graphic output.
d) Twisting device for testing untwisted or low-twist filament yarns, allowing the filament yarns to pass through the capacitance detection area with an approximately circular cross-section. Correct
The test on monofilament does not require twisting device.
5.3 For calibration, use the program built into the instrument as much as possible. The standard information of known unevenness provided by the instrument manufacturer can also be used.
No. If the instrument manufacturer does not have an available standard, a known sample with a low unevenness can also be used.
GB/T 3292.1-2008
6 Standard atmosphere
The standard atmosphere for pre-conditioning, conditioning and testing shall be in accordance with the standard atmosphere specified in GB/T 6529.Normally non-packaged yarns are humidified for 24h, packaged yarns
The humidity should be adjusted for 48h.
7 Sampling
7.1 Select laboratory samples according to one of the following methods.
---According to relevant regulations of product standards;
---According to the agreement of the relevant parties.
7.2 Recommended sampling number.
---Sliver. 3 rolls;
---Roving. 4 packages;
---Short fiber yarn. 10 packages;
---Filament yarn. 5 packages.
7.3 The test material should be unwound directly during the test to avoid deformation of the yarn.
7.4 The number of samples for each package shall be in accordance with the product standard. If the product standard does not stipulate, each package shall be tested once.
7.5 The sampling length shall be at least.
---Sliver. 50 m;
---Roving. 100m;
---Short fiber yarn. 400 m;
---Filament yarn. 400m.
8 Procedure
8.1 Regularly verify the evenness meter according to the method stipulated in the measurement and verification regulations of the evenness meter.
8.2 Selection of uneven curve range.
---Sliver. ±25%;
---Roving. ±50%;
---Glass fiber yarn. ±100%;
---Short fiber yarn. ±100%;
---Filament yarn. ±10% or ±12.5%.
8.3 Selection of Capacitance Measuring Slot
There is a certain degree of overlap between the ranges of adjacent capacitance measuring tanks, so that certain samples can be tested in the two tanks, and the results may be different.
different. According to the recommendation of the instrument manufacturer, select the suitable measuring slot for different yarn counts.
8.4 Selection of yarn unwinding speed
Generally, the unwinding speed is selected according to the yarn bearing capacity and the needs of test analysis. The following unwinding speeds are recommended. If other
Speed, which should be indicated in the test report.
---Sliver. 25m/min;
---Roving. 50m/min;
---Spinning yarn. 400m/min.
8.5 Yarn guide device
Before the test, adjust the yarn guide and tension device to provide a pre-tension that will not stretch the yarn (otherwise it will damage the material) to ensure that the sample does not
GB/T 3292.1-2008