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2. Meteoritic iron artefacts redux

Creator:
Zavyalov, Vladimir I. and Terekhova, Nataliya N.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
meteoritic iron, nickel, bloomery iron, archaeometallurgy, prehistory, Early Middle Ages, meteoritické železo, nikl, svářkové železo, archeometalurgie, pravěk, and raný středověk
Language:
Czech
Description:
The earliest iron artefacts are often presented as products made of meteoritic iron, which is characterised by its high iron content. However, recent studies have shown that high nickel and iron content cannot be taken as a firm criterion for establishing its meteoritic origin. The most effective tool for helping to specify the elemental composition in such cases is a metallographic analysis. It turns out that the material of many artefacts regarded as having been forged from meteoritic iron could in fact be bloomery iron. An analysis of ample yet scattered evidence suggests that the production of items from meteoritic iron could in fact be irregular and sporadic and Nejstarší železné artefakty jsou namnoze prezentovány jako výrobky z meteoritického železa, jehož typickým rysem je vysoký obsah niklu. Nedávné studie však ukázaly, že vysoké obsahy niklu v železe nelze brát jako pevné kritérium pro stanovení jeho meteoritického původu. Nejúčinnějším nástrojem, který v takových teriál mnoha předmětů, které jsou považovány za výkovky z meteoritického železa, může být ve skutečnosti železem svářkovým. Analýza četné, byť porůznu rozptýlené evidence nasvědčuje tomu, že výroba předmětů z meteoritického železa mohla být ve skutečnosti prostorově nerovnoměrná a sporadická.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

3. Thermo-mechanical properties of NiTi closed coil springs--force degradation and force regeneration over time, viscous properties

Creator:
Bezrouk, Aleš, Balský, Libor, Smutný, Martin, Nosek, Tomáš, Záhora, Jiří, Hanuš, Josef, and Polma, Richard
Format:
print, text, and regular print
Type:
model:article, article, Text, časopisecké články, práce podpořená grantem, and TEXT
Subject:
pevnost v tlaku, elasticita, lidé, testování materiálů, nikl, ortodontické aparáty, pevnost v tahu, časové faktory, titan, and viskozita
Language:
English
Description:
INTRODUCTION: The aim of this study was to find out the impact of degradation and regeneration of force over time at NiTi springs on the value and course of the final acting force and to verify the possibility of using these phenomena for a directed transition to the reverse plateau and its maintaining. METHODS: Static and cyclic mechanical loadings were performed. At first unused springs were tested. Afterwards the springs were mechanically stabilized by stress cycling and finally tested again. The difference in shape of the working curves was assessed. For simulation and description of the force degradation the modified Voight model was used. RESULTS: New springs, mainly those with large hysteresis, showed a significant stress-strain curve movement and shape changes during the cycling. The effect of the stress-strain curve course change disappeared fully in the stabilized springs. Multiple loading led to an overall decrease of force value during the measurement. The effect of force degradation and regeneration over time by simple static loading varies in the range of percentage of the nominal force in the plateau area. The transition between stress-strain curve phases caused by the degradation or regeneration of the force wasn't observed in case of mechanically stabilized springs. CONCLUSIONS: Springs should be mechanically stabilized before their application. The degree of force degradation over time is insignificant for mechanically stabilized springs. Degradation or regeneration of force over time, mechanical stabilization or micromovements in the mouth don't cause any transition between individual stress-strain curve phases. and A. Bezrouk, L. Balský, M. Smutný, T. Nosek, J. Záhora, J. Hanus, R. Polma
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public