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
Inverse Relaxation/Stress Recovery in Cotton Fibers and Yarn
The literature on mechanical properties of textile fibers is replete with data on viscoelastic characteristics like stress relaxation, creep, creep recovery, etc. A closely associated property, &dquo;stress recovery&dquo; or &dquo;inverse relaxation,&dquo; on the other hand, does not seem to have been investigated. If an extended specimen is allowed to recover a part of the deformation and constrained to remain at a length higher than what it is likely to assume if allowed to retract fully, the stress in the specimen tends to increase. This inverse relaxation or stress recovery, which is a function of time, is initially fast but slows down later on. The stress thus rises exponentially with respect to time. Neither a discussion of the significance of stress recovery nor experimental data on this property can be found in literature, though Peters and Woods have mentioned tension build-up [ 1 ]. We record here the stress recovery data on a cotton fiber sample and a cotton yarn sample tested using the Instron Tensile Tester.
16—The Position of the Cloth Fell in Power Looms
A theoretical analysis of the factors governing pickspacing has been carried out as part of an investigation into the problem of setting-on places in woven fabrics. Mathematical expressions relating the rate of take-up to the position of the cloth fell and the latter to pickspacing are developed for both bumping and non-bumping conditions. Some features of the warp tension cycle are discussed and it is shown how the work done in beating up the new pick can be calculated.