Measuring the Region of Frictional Slip and Its Applications.

Abstract

The region of frictional slip ΔT of spun yarns. has been suggested by J.W.S. Hearle, P. Grosberg and S. Backer. An attempt is made to determine continuously and objectively values of frictional slip ΔT by using an untwisting and drafting system developed by anthors for the rearrangment of fibers in open-end yarns.The system is constructed with two pairs of rollers ; feed rollers and delivery rollers, and with one set of rotor fitted between the two pairs of rollers to untwist a yarn falsely. The surface velocity of the delivery roller is slightly higher than that of the feed roller.In this system, the twist density between, the feed roller and the rotor is reduced to T-R, where T is a number of twist of a yarn and R is a number of untwisting by mechanical operations. If the value of T-R is very small, the yarn tension may be reduced to nearly zero. Assuming that the yarn tension is zero when the value of T-R is within the range of ΔT*/2≤T-R≤ΔT*/2, relation between the relative frequency of the zero tension of the yarn Z (R) and the probability density function of the yarn twist density n (T) is given by : Z (R) =∫R+ΔT*/2R-ΔT*/2n(T)dtZ (R) can be measured by using the untwisting and drafting system, and n (T) is determined by untwisting and twisting method. Then, the values of ΔT* are caluculable by the equation above.The experimental results are as follows : (1) The linear relation is found between ΔT and ΔT*.(2) ΔT is not constant throughout the sample of yarn, i. e., the more twisted parts of the yarn shows the smaller value of ΔT* and vice versa.(3) Many kinds of yarns with the same material but produced by different spinning operations, show the general rule that under certain limiting condition for ΔT* the stronger yarn shows the smaller mean value of ΔT*.