Nanotechnologies allow the production of yarns containing nanofibres for use in composites, membranes and biomedical materials. Composite yarns with a conventional thread core for mechanical strength and a nanofibrous envelope for functionality, e.g. biological, catalytic, have many advantages. Until now, the production of such yarns has been technologically difficult. Here, we show an approach to composite yarn production whereby a plume of nanofibers generated by high throughput AC needleless and collectorless electrospinning is wound around a classic thread. In the resulting yarn, nanofibres can form up to 80% of its weight. Our yarn production speed was 10 m/min; testing showed this can be increased to 60 m/min. After the yarn was embedded into knitwear, scanning electron microscope images revealed an intact nanofibrous envelope of the composite yarn. Our results indicate that this production method could lead to the widespread production and use of composite nanofibrous yarns on an industrial scale.
The paper presents the approach to analyse of reaction forces and contact pressure for ring-traveller system in twisting machine. The theory of the ballooning yarn has been adapted for the calculation of reactions, and the motion equation is developed for traveller with two reaction forces. The components of normal reaction forces are analyzed for system with free balloon and control one. The effect of the balloon control ring is shown to be significant, reducing the reaction forces of traveller or increasing the speed of spindle. Contact pressure generated between the ring and the traveller is analyzed using Hertzian contact theory. The article also presents the recommendations for optimization of the traveller shape to increase its service life.
The paper is focused on the design of the electrode for needleless coaxial electrospinning. This method allows to produce core/shell nanofibers from the free surface of a polymeric two-layer. The geometry of the designed model of electrode was analyzed using the software Autodesk Simulation Multiphysics. The results of electrostatic field simulation indicate the sharp edges of the electrode as the source of high electric intensity. These sharp edges lead to the loss of the electric energy during the electrospinning process. Based on that, the new cylindrical geometry of the electrode was developed. The results of carried out experiments clearly demonstrate the enhancement of the electrospinning process stability.
Vehicles and Engines, Studentská 2, 461 17 Liberec 1, Czech Rep. .Abstract. This paper is concerned with experimental analysis of the behaviour of mechanisms of sewing machines. There has been carried out mapping of the sound field in the vicinity of the sewing machine, in order to locate the source of impact loading and to establish the overall hygienic loading of the machine. Based upon this analysis, the acceleration of the needle bars has been measured. These two measuring have led to the conclusion that it is the cam mechanism which most contributes to the noise and impact loading.
The paper focuses on the process of non-contacting kinetic energy accumulation at the dead-end positions of a reciprocating rectilinear motion with a variable stroke. It describes the development of a magnetic-mechanical accumulator that absorbs energy while the moving part is decelerating towards the dead-end position and releases the energy back to the system while it is accelerating from the dead-end position. At the same time, it enables stroke modification of a certain level with a minimal impact on the maximum force of the accumulator. With respect to the magneto-static analysis of components, the preload of the mechanical element has been set accordingly. The dynamic analysis of the system has been carried out and the prototype produced and tested on the testing rig.
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