Study of Rib Knits Coursewise Tensile Process

Abstract

Stretchability of knitwear is one of the most important factors of wearing comfort. Elasticity of knitted structures in course wise direction is usually higher than along wales and often characterized by crosswise shrinkage. Existing methods of knitting program development do not consider the real rate of wale wise shrinkage of rib knitted structure under the course wise extension. During the study experimental research has been carried out to fulfill empirical data on the relationship between samples’ length and width under uniaxial course wise elongation. A range of samples of rib 1×1, 2×2, 3×3, 4×4 and 5×5 knits, made of cotton, bamboo, polyacrylonitrile (PAN), wool/acrylic blend and wool yarn, were stretched with a tensile machine WDW-05M. In the process of stretching the width of each specimen was defined in the moments of extension by 50, 100, 150, 200, 250 and 300 per cent. It has been found that linear approximation can be applied to describe the dependence of specimen’s width on its relative course wise elongation. It was found that the stitch height/width ratio changes unevenly. In the beginning of the process of course wise stretching of a rib knitted structure, it does exist, such an interval, where an increase of the knit’s linear size along the courses occurs without a significant shrinkage in the wale wise direction. It is suggested to name the upper limit of this interval as “unidimensional extension limit” and define it as an extension of a standard (100×50mm) specimen, at which its width decreases by 10%. It was found as well that the value of this index significantly depends on the ribbing variation and much less on the type of raw materials

FRAME MODEL OF UNIAXIAL STRETCHING OF 1x1 RIB KNITS

“…In the formalization study the minimal width Wtc for a certain deformation state t can be assessed experimentally as well as the numbers of stitches in wales and courses of the specimen. For future development of the model it can be calculated as it was suggested in paper [16]. The change in the sample's shape depends on the way the tensile force is applying.…”