Abstract:

In order to obtain a more reasonable approach to estimate staple yarn strength, based on idealized assumptions of yarn structure and definition of critical slipping length, the expression of fiber critical slipping length during yarn breaking process was deduced, as well as the actual contributions that breaking and slipping fibers made to yarn strength. Considering variation of fiber number in each yarn cross section, yarn strength was then calculated by simulating fiber random arrangement in the yarn based on the calculated critical slipping length. Viscose and polyester yarns of various yarn counts and twist multipliers were spun and their strengths were tested for calculation and verification. It could be seen from calculated results that the critical slipping lengths declines with the increase of the yarn twist multiplier. Meanwhile, as the twist multiplier increases, the calculated yarn strength increases to the highest point and then decreases, which is in good agreement with tested results.

Key words: staple yaran strength, critical slipping length, twist multiplier, effective fiber strebgth, slipping frictional force