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| PART - II |
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Chapter 6
Practical Application |
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Can We Modify the General Equation to Accept HVI Data? |
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A reader is now most likely to raise two questions. i) Can we modify The General Equation to calculate CSP of ring-spun yarn from HVI data? i) Can we modify The General Equation to estimate rotor yarn CSP from HVI data? |
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Before we begin to answer these questions, let us recapitulate some tenable premises that are fundamental to The General Equation: |
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A single fibre-length parameter is totally inadequate to characterize disparate cottons like S-4, which has a uniform fibre-length distribution, and DCH cotton, that is notorious for its variation in fibre-length for their susceptibility to yarn irregularity -- Figure II – 6 - v. |
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A study of data on the frequency of thin and thick places in the yarn clearly establishes that the use of a parameter that is derived from Baer-sorter statistics, namely, effective length, and %-ages of fibres shorter than 12-mm and longer than 24-mm is very appropriate to use in the expression for the irregularity fraction. |
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Fibre millitex is the valid measure of fineness for use in predictive equations – not the rapidly measurable micronaire. |
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The typical inverted parabola shape of the CSP-TM plot is the result of the three-fold effect of twist: with increasing twist, there is a reduction in fibre-slippage, a shortening of the gauge-length of fibre-breakage in yarn tenacity-test, and an increase in the obliquity of fibres within the yarn to the yarn axis. |
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Now HVI does not provide data on any of the following: the %-ages of fibres at the two critical lengths; fibre-tenacity at two different gauge-lengths; fibre millitex. Furthermore, in the fibre-tenacity testing by HVI there is a likelihood of some percentage of fibres in the bundle under test having a free end within the test length. Would not this %-age be more for a short-fibre cotton than for a comparatively long cotton? Again would not this %-age be more for a cotton that is much more variable in length than that for a very uniform cotton? One can argue that this very feature of the fibre-bundle test by HVI, of there being free fibre-ends in the bundle that breaks, can perhaps make it quite suitable for estimating yarn tenacity, the test for which shares the feature with HVI fibre-tenacity test. One has then to rewrite the expression for F3 taking this aspect into consideration. One has to ponder over these points and questions before one rushes to modifying The General Equation, for use with HVI data. Having said this, let us yield to the exigency in the situation. |
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