NEW METHOD FOR THE EVALUATION OF WOVEN FABRIC UNEVENNESS

Abstract

Unevenness of woven fabric results from irregularity of the yarn used as well as from the process of its manufacture (weaving). A periodical and non-periodical yarn irregularity shows itself in the flat textile by known effects - the moiré effect, cloudiness, and stripiness. It is possible to predict the appearance of flat textiles from measured values of yarn mass irregularity and their characteristic functions (a spectrogram, a variance-length curve). The evaluation of surface unevenness of woven fabrics is done not directly but by judging their appearance, most often subjectively. For evaluation of flat textile appearance, it is also possible to use a so-called area-variation curve. The curve can be constructed on the basis of analysis of a woven fabric image either by a special program, created by J. Militky (Technical University of Liberec) in the programming environment Matlab, or by means of image analysis. By these methods it is possible to evaluate an image of real flat textile as well as a simulated image from an apparatus for yarn irregularity measurement. The woven fabric image is in grey scale. The variation coefficient of greyness degrees expresses the unevenness of flat textiles. In the experiment both real woven fabric images and simulated appearances of woven fabric, obtained by means of the apparatus Uster Tester IV, are evaluated by the methods mentioned above. The acquired area-variation curves are compared with each other and compared with visual evaluation of the woven fabric image. It was found that area-variation curves show only marked unevenness of woven fabric.