Yarn twist blocking occurs when a yarn slides over a yarn guide or other machine part. This paper reviews previous investigations on twist blockage, the influence of yarn and guide conditions, and especially twist blocking mechanisms. The twist block- ing mechanisms so far suggested are all based on a continuum yarn model-a yarn treated as a flexible and laterally deformable cylindrical body. The validity and draw- backs of these mechanisms are discussed. A further mechanism based on the continuum yarn model-twist blocking due to biased normal pressure distribution across the yarn-is proposed, and yarn twist blocking phenomena are then re-examined by treat- ing the yarn as an array of mobile fibers.
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