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Thermal post-impact behaviour of closed-cell cellular structures with fillers
Matej Vesenjak, Andreas Öchsner, Zoran Ren, 2007, original scientific article

Abstract: The study describes the behavior of regular closed-cell cellular structure with gaseous fillers under impact conditions and consequent post-impact thermal conduction due to the compression of filler gas. Two dependent but different analyses types have been carried out for this purpose: (i) a strongly coupled fluid-structure interaction and (ii) a weakly coupled thermal- structural analysis. This paper describes the structural analyses of the closed-cell cellular structure under impact loading. The explicit code LS-DYNA was used to computationally determine the behavior of cellular structure under compressive dynamic loading, where one unit volume element of the cellular structure has been discretised with finite elements considering a simultaneous strongly coupled interaction with the gaseous pore filler. Closed-cell cellular structures with different relative densities and initial pore pressures have been considered. Computational simulations have shown that the gaseous filler influences the mechanical behavior of cellular structure regarding the loading type, relative density and type of the base material. It was determined that the filler's temperature significantly increases due to the compressive impact loading, which might influence the macroscopic behavior of the cellular structure.
Keywords: mechanics, cellular structures, closed cells, gas fillers, impact loading, fluid-structure interaction, dynamic loads, LS-DYNA, ANSYS CFX 10.0, computational simulations
Published: 31.05.2012; Views: 982; Downloads: 20
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The influence of thread twist on alterations in fibers` mechanucl properties
Andreja Rudolf, Jelka Geršak, 2006, original scientific article

Abstract: In order to design high-quality threads, it is necessary to know the properties of threads and fibers, as well as the loadings and deformations which may occur during the sewing process. Thread properties depend on the mechanical properties of the fiber and the constructional parameters of the thread and its surface treatment, which directly influence sewing performance.The mechanical properties of a thread primarily depend on the fiber mechanical properties and the amount of twist. Knowledge of the thread dynamic loadings during the sewing process, depending on the number of turns and the lubrication method, is important for planning the required processing properties of the thread. This paper presents research into the influence of thread twist and the lubrication method on the mechanical properties and dynamic load of PES core-spun thread and its fibers. Research into the mechanical properties of the different twisted and surface treated threads, and separated fibers was carried out for this purpose. The influence of threaddynamic load during a sewing process was also researched regarding any alterations in the mechanical properties of the threads and separated fibers. Analyses of the results show that the amount of twist depends on the mechanical properties of the thread and its constituent fibers, whilst the method of surface treatment is based on the specific mechanical properties of the thread. A dynamic load causes greater or smaller thread deformations, which is reflected in changes in the thread and fiber mechanical properties. The occurred changes depend on dynamic load, amount of twist, and the lubrication method, which is confirmed with statistical analysis of the measured results.
Keywords: garment manufacturing, sewing, threads, textile fibres, surface treatment, dynamic loads, mechanical properties, amount of twist
Published: 30.05.2012; Views: 1651; Downloads: 23
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