Summary
This paper presents the results of experiments in which two thinwalled tubes of commercially pure aluminium in the annealed condition were loaded in combined tension and torsion in the plastic region at elevated temperatures. In the first test prestressing was in torsion but of a cyclic nature. In the other test prestressing included a path reversal in tension. It is shown that the hardening law introduced previously [3] is such that prestressing towards the origin of the stress space produces an increase in the width of the yield curve in the prestressing direction. It is also shown that a locus of zero deformation of yield surfaces can be postulated.
In the present paper we also show the existence of negative plastic strains and we show that offset yield surfaces are closely related to envelopes of proportional limit yield surfaces.
Zusammenfassung
In dieser Arbeit werden Resultate von Experimenten, in denen zwei dünnwandige Rohre aus handelsreinem, normal-geglühtem Aluminium durch Zug und Torsion bei erhöhten Temperaturen, im plastischen Bereich belastet wurden, angegeben. Im ersten Versuch wurde durch Torsion zyklisch vorverformt und im zweiten durch Zug bei Umkehr des Belastungsweges. Es wird gezeigt, daß das in [3] angegebene Verfestigungsgesetz bei Vorverformung gegen den Ursprung des Spanungsraumes eine Aufweitung der Fließkurve in der Vorverformungsrichtung bedingt. Es wird ferner gezeigt, daß die Existenz von Vorverformungen, die keine Veränderung der Fließflächen bewirken, postuliert werden kann.
In dieser Arbeit wird außerdem die Existenz negativer plastischer Verzerrungen gezeigt, und, daß der Beginn der Fließflächen eng verknüpft ist mit den Einhüllenden der Proportionalitätsgrenzen-Flächen.
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References
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Phillips, A., Tang, J.L. & Ricciuti, M. Some new observations on yield surfaces. Acta Mechanica 20, 23–39 (1974). https://doi.org/10.1007/BF01374960
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DOI: https://doi.org/10.1007/BF01374960