Measurements of inverse creep in polyester multifilament yarns
Creep and Inverse creep are the important fundamental properties of textile materials. These properties determine the relaxation behaviour of the product. We have designed and fabricated an instrument which can measure the creep and inverse creep. The instrument consists of a Trans - Receiver unit interfaced with Embedded System along with the Personal Computer. Existing technique for measuring inverse creep does not measure the instantaneous extension or contraction. The newly fabricated instrument, can measure the instantaneous extension and contraction of the yarn up to an accuracy of 0.02%. This can be measured after every 500 μs. The position of the yarn, which is to be hanged, is vertical. The 'Electronic Timer Unit', replaces a meter scale. Set up is improved by using electronic utilities. The capability is enhanced to next level of time and distance resolutions. Automation enables to have flexibility of time from microseconds to minutes. Data is stored in different text files. Different samples of Polyester multifilament yarn were used in the experiment. The length and the load were altered. Change in stress lead to instantaneous extension or contraction followed by creep or inverse creep. This can sensed by the sensor and further stored in the memory of the Computer. The percentage creep and inverse creep were measured and have been reported in this present paper
Relaxation and Inverse Relaxation of Yarns After Dynamic Loading
During weaving, warp yams are subjected to dynamic loading before stress relaxation during a loom stop. A test method is presented for simulating this behavior. There are three types of relaxation curves—simple relaxation, inverse relaxation, and mixed relaxation—depending on the previous load history of the yam. One can calculate the residual force at infinite time in a relaxation test from a model for the tensile curve of spun yams. There seems to be good correlation with the results of tests made using this method.
Influence of a Yarn Extractive Nozzle on the Apparent Loss of Twist in Rotor Open-End Acrylic Staple Spun Yarns
The influence of a yam extractive nozzle on the apparent loss of twist or "residual twist" has been studied for rotor open-end acrylic staple spun yarns. Four factors were studied: two quantitative factors - yam linear density at three levels and yarn twist multiplier at five levels, and two qualitative factors - three nozzle types and four rotor types. The analysis of results showed that both rotor type and extractive nozzle type exert a significant influence on residual twist, which tends to increase when the nozzle produces an increasing false twist effect on the yam and to decrease when yarn friction against the rotor increases. Residual twist increases significantly in a linear manner with both yarn linear density and twist multiplier. The nozzle type interacts significantly with all other factors (rotor type, yam linear density, and twist multiplier). An inter action between yarn linear density and twist multiplier has been also detected. Generally both nozzle type and twist multiplier exert a significant influence on the residual twist coefficient of variation.