D. Radivojevic’s research while affiliated with University of Novi Sad and other places

Determination of warp length for weaving of required length of fabric is always a current problem of weaving production Thus the aim of this paper is to contribute to the development of a method for the correct definition of required warp length for a given fabric length. Designing the warp length is closely related to the determination of warp ends crimp The crimp of warp ends in fabric is defined by a number of parameters. The most important among them are characteristics of yams used fabric weave, density and tension of threads. Analyzing theoretical assumptions and experimental results defined are relationships that can be used in designing warp lengths to form various structural and construction solutions.

In many cases single yarns do not fulfill the requirements necessary for the production of certain types of textiles. At the same time, they do not have most of the characteristics that are important for textile production with outstanding quality parameters. Therefore, the twisting process is employed to produce twisted yarns which can be used to produce fabrics for various applications. The breaking properties of twisted yarn depend on the strength of the component yarns, the number of strands, the twisting amount, the friction forces between the yarns, as well as on the twisting method used. The use of known parameters of twisted yarns determines the relations defining their breaking force. The breaking force is here defined as a function of the breaking forces of the component yarns, the number of yarns twisted in the yarn, and their angle to the twisted yarn axis. In addition, based on experimental results and the theorethical equations, real mathematical relations were established which can serve to project the breaking forces of ring and rotor twisted yarns obtained by the method of double layer twisting. This will simplify and improve the technical preparation of the weaving process. twisted yarn type. Special attention was given to the projecting of the breaking forces of twisted ring spun yarns, twisted rotor spun yarns and twisted yarns made of one rotor spun and one ring spun yarn. By combining one ring spun and one ro-tor spun yarn, an attempt was made to take advantage of the positive properties of two component yarns.

Projecting of deformation characteristics of single and twisted wool yarns Determination of yarn load limit values during its processing is a precondition for correct process adjustment and also for maintaining yarn quality. Using experimental data, Berejev's model was modified in such way as to enable the projecting of the breaking forces of worsted wool yarns with linear densities of 18 tex to 32 tex. An equation for projecting breaking forces of twisted yarns with 18 × 2 tex and 32 × 2 tex was derived. The elasticity, elasticity limits and yield point limits of single yams with 21 tex, 23 tex and 25 tex, as well as their more complex twisted structures were analyzed. Based on experimental results and theoretical equations, real mathematical relationships were established, enabling projecting of forces, elongations, elasticity limits, yield and breaking points of single and twisted wool yarns, which offers a possibility to predict yarn behavior during subsequent processing.

Defining thresholds for yarn strain in manufacturing process is crucial for appropriately adjusting these processes and keeping high yarn quality. That is the main reason why the issue has drawn so much intention. The knowledge of elasticity limits and yield points is very important for the optimization of the production process and further twisted woolen yarns processing. Therefore, this paper defines the limits for elasticity and yield points and breaking forces of woolen yarns with the linear density of 21x2 tex, 23x2 tex and 25x2 tex, obtained by two-for-one twisting method. The interrelationship between the forces and the elongations at elasticity limits, yield points and breaking force of these yarns are also analyzed. Besides, on the basis of experimental results and equations, real mathematical dependences are set, which can be used to predict forces and elongations of woolen yarns at elasticity limits, yield points and breaking limits.

In the winding process, on its way from the spinning tube to the bobbin, yarn was exposed to different influences that caused various tensions in different sectors. The increase in the tension force brought about a decrease in the linear density of all the wound yarns. All of this influenced the resulting tension with which the yarn was wound onto the bobbin. After two weeks, the deformation characteristics of these yarns were examined. Also determined were values of the breaking forces and relative elongation at break for all the linear density. On the basis of a F-ε curve, elasticity limits were defined as well as the yield point of the wound yarns analysed. Making use of the recommendations of some investigators, it was possible to project the breaking forces, elasticity limit force and forces at the yield point. The quality control of raw materials, process control and yarn quality control are a necessary help for the technologist to establish a well-set winding process. It is only on the basis of the exact parameters provided by such controls that it becomes possible to intervene correctly and in time in order to achieve optimal results and obtain good quality wound yarn.

The physical-mechanical properties of yarns, similar to those of other solid matters, are a function of their structure. Yarns are composed of fibres of different lengths and shapes, resulting in yarn spirals with varying radii, which can form kinks at intervals, and even project from the yarn surface. Therefore, it is not the overall length of the fibre that contributes to the yarn strength, but only the spun-in part of it. In this work the spinning-in coefficient KF was determined for carded and combed rotor-spun yarns, in accordance with the theory of spun-infibres in yarns. Measurements have shown that the inner structure of cotton rotor-spun yarns, presented by the value of the coefficient varies with the spinning system used The KF values for combed yarns show that most of the fibres were incorporated into the yarn, which gives better physical-mechanical characteristics. In carded yarns, this coefficient is slightly lower, indicating a greater number of looped fibres and fibres incorporated into the yarn with less than half their lengths.

There have been many attempts to pre-determine the yam quality, taking in consideration, besides the fibre type, also the spinning system and machinery working conditions taking part in the process of yam manufacturing. All these attempts can be divided into theoretical ones, when complex mathematical models are obtained, and arithmetically-empirical ones, based on a large number of experimental measurements. One of such attempts is the method by AX Solovjev, which refers to ring spinning. The paper explores the possibility of applying this method for determination the limits of spinnability and tensile properties of OE yams spun from microfibres, which are the basis for the predetermination of the quality of this yarn type.

Knowing the mutual coherence of the deformational characteristics of fabrics, their regular projections are provided according to their future assignment. The limit of elasticity and the creep limit of the fabrics are characterized, by which their behavior during exploitation can be simulated. Therefore, in this work, analyzed is the relationship between the breaking forces, the elasticity limit forces and the creep limit of the fabrics produced from filament PA yarns and Wo-PES mixed yarns. Also, according to the values obtained of the forces that the fabrics can be subjected to during the exploitation, can be projected, without the perturbation of their quality.

The physical-mechanical properties of yarns, similar to those of other solid matter, are a function of their structure. The yarns are composed of fibers of different lengths and shapes, resulting in yarn spirals with varying radii, forming kinks at intervals, and even projecting from the yarn's surface. Therefore, it is not the overall length of the fiber that contributes to the yarn's strength, but only the spun-in part thereof. In this work, the spinning-in coefficient, KF, was determined for conventional and compact ring--spun yarns, in accordance with the "theory of spun-in fibers in yarns". The measurements have shown that the inner structure of cotton ring-spun yarns, presented by the value of the coefficient, varies with the spinning system used. KF values for compact yarns show that most of the fibers have been incorporated into the yarn, giving better physical-mechanical characteristics. In conventional ring-spun yarns, this coefficient is slightly lower, indicating a greater number of looped fibers and fibers incorporated into the yarn with less than half their lengths.

In the winding process, yarn is exposed to various factors on its way from the spinning tube to the bobbin which influence yarn tension in particular sectors of the yarn path. This results in the tension with which the yarn is wound on the bobbin. In this work, the yarn tension of the wound yarns was measured under different winding conditions; afterwards the multi-cyclic mechanical deformation of these yarns was examined. The resistance to multi-cyclic extensions was assessed by repeated extension to constant elongation using an Instron tester. An elongation of 4% corresponding to warp elongation on the loom was chosen. Worsted wool yarns spun from T-62 and T-63 wool fibres with linear densities 25 tex, 12 tex and 21 tex were chosen as experimental material.