Effects of Cotton Fiber Blending and Processing on HVI Measurements—Part II

An earlier study confirmed the influence of cotton fiber length characteristics on the High Volume Instrument™ (HVI) strength measurement and devised a quantitative correction factor to compensate for the effect. The current paper investigated the validity of two important assumptions utilized in the previous study. Firstly, single fiber testing confirmed that the particular sample preparation method used to generate samples of different fiber length characteristics from a common cotton sliver did not introduce any inherent damage to the fibers (and so this could not be the explanation for the observed trend in measured fiber strength as a function of fiber length). Secondly, the positioning of the jaws relative to the beard in the HVI strength measurement was explored. This positioning was found to be quite variable for replicate measurements on the same cotton being a function of the size of each individual beard. The average positioning between the different samples was found to be similar and this validated the assumption and approach used previously for deriving the correction factor for that particular sample set. Characterizing the position of the jaws was extended using a wider range of cotton samples. The HVI positioning algorithm appears to not simply be a function of the size of the beard (i.e. the ‘amount’ parameter), but is also dependent on fiber length characteristics. It was also observed that the reported HVI elongation values displayed both a significant bias due to fiber length and also a dependence on the size of individual beards tested.

Section: Resultsmentioning

confidence: 96%

“…Fryer et al. 8,9 studied the effect of varying the jaw placement on the HVI strength measurement and demonstrated that placing the jaws at different span lengths may introduce errors into strength measurements by changing the subset of fibers in the test.…”

mentioning

confidence: 99%

Understanding the influence of fiber length on the High Volume Instrument™ measurement of cotton fiber strength

Naylor

Delhom

Cui

et al. 2014

“…24 , 25 The low repeatability of the SFI, however, prevents it from being used in the United States Department of Agriculture’s (USDA's) raw cotton classification system. 26–29…”

mentioning

confidence: 99%

Image-based Bilateral Beard Method for measuring weight-based short fiber contents in raw cotton and semi-finished slivers

Lang

Zhang

Wang³

et al. 2021

In this paper, an economical way for accurately determining weight-based short fiber contents in raw cotton and semi-finished slivers by utilizing special bilateral beard specimens and image processing was introduced. In the specimen preparation, cotton fibers were drawn by a manual device into a sliver, then the sliver was combed to form a bilateral beard specimen, and finally the bilateral beard was scanned to generate a grayscale image from which a relative fiber number curve was extracted. An algorithm for calculating the weight-based short fiber contents based on the curve was proposed. Five types of cottons were repetitively measured to investigate the robustness of the results of [Formula: see text] and [Formula: see text], with the weight ratio of fibers shorter than 12.7 and 16 mm, respectively. The results showed that measuring two bilateral beards for each sample could keep the error rate lower than 15%, while four specimens kept the error rate lower than 10%. Compared with AFIS Pro 2, this Image-based Bilateral Beard Method provided results with lower standard deviations and variable coefficients, signifying its analogous or better robustness. In addition, 37 samples from some of the world’s major producing areas were measured by this method and AFIS Pro 2, and a Bland–Altman analysis confirmed a good agreement between the results from the two methods. As only a manual fiber drawing device and an office scanner are needed, this Image-based Bilateral Beard Method is clearly a cheap approach for accurately determining the short fiber contents in raw cotton and semi-finished slivers.

“…Fryer et al. 16,17 modeled the effect of varying the jaw placement (i.e. the distance D1 in Figure 1) on the HVI strength measurement and demonstrated that placing the jaws at different span lengths may introduce errors into strength measurements by changing the subset of fibers in the test.…”

mentioning

confidence: 99%

Evidence and potential explanation of the influence of fiber length on the High Volume Instrument measurement of cotton fiber strength

Naylor

2013

This study explores the influence of cotton fiber length characteristics on the High Volume Instrument (HVI) strength measurement. A set of cotton samples cut at different lengths from a common parent sliver was used. HVI strength data exhibited a consistent trend as a function of the fiber length properties. This data was analyzed using the working hypothesis that the HVI estimates the total mass of fiber at a position between the jaws, rather than the true mass, which contributes to the breaking force. A quantitative model was developed to correct for this overestimation based on the shape of the Fibrogram. It was demonstrated that the Fibrogram can be adequately modeled as a straight line in the region of the HVI strength measurement. Based on this, it was found that the required correction factor is a function of the mean fiber length and various geometrical parameters of the HVI instrument (i.e. (a) the distance from the base of the beard to the inside edge of the clamp nearest the base of the jaws, and (b) the actual position of the beard's fiber length determination relative to the clamping jaws). Importantly this correction factor is independent of the shape of the fiber length distribution. Application of this correction factor approach was able to remove the effect of fiber length on the corrected strength values. The same model was also applied to other published data and, again, a simple correction factor based on mean fiber length adequately 'removed' the observed bias.Cotton length and strength are two important fiber quality parameters that are commonly measured using the Uster High Volume Instrument (HVI) (e.g. ASTM Test method D 4605-86 1 ). For example, the Agricultural Marketing Service of the United States Department of Agriculture (USDA) specifies a range of cotton fiber quality parameters, including fiber strength and length characteristics based on HVI measurements.Average length and strength values of US cotton have both steadily improved, 2 and it is assumed that these values reflect real and separate improvements in both characteristics. Indeed, plant breeders develop strategies for new varieties with improved length and strength on the assumption that both are separate parameters that require attention.Cotton fiber length is generally quite variable within a sample and description of the length distribution has been the subject of a wide range of studies (recent work includes Krifa 3,4 and Lin et al. 5 ). Fiber breakage during ginning is a major contributor to the broadening of the length distribution, and as Krifa 3 notes, modeling of the length distribution is dominated by applications of 'breakage models'. 6-8 Krifa 4 demonstrated that a mixture of two Weibull probability density functions adequately fits the experimental length distribution data.