Constraint behaviour of polymeric materials due to multiaxial loading
To ensure a safe operation of a component or structure under real service conditions it is necessary to compare an existing stress state with material properties and to keep the material constraint safely below the failure limit. But this comparison is in many cases quite difficult as service loading modes are mostly multiaxial whilst typical material properties are determined in uniaxial stress fields, e.g. in a tension test. Those multiaxial stress states are commonly reduced to a fictive uniaxial stress state, the equivalent stress, which describes the same material constraint. This uniaxial equivalent stress state allows comparison with material parameters determined in uniaxial stress fields.
The present work summarizes classical strength hypotheses and discusses possible modifications in order to consider the influence of the hydrostatic stress tensor.
A load-controlled testing machine has been developed, which allows tests on tubular specimens under defined tension, compression, torsion, internal pressure and defined combined loads. Creep tests have been conducted in combined tension/torsion or compression/torsion tests.
The validity of those modified and extended equivalent stress criteria has been experimentally verified on PMMA, PVC and PA6 and on data taken from literature. The model parameters used in these modified criteria can be determined in experimentally simple tests - e.g. like tension and compression tests or tension and torsion tests.Lesen Sie die deutsche Zusammenfassung auf Kunststoffe.de
Multiaxial stress state, equivalent stress, material constraint, hydrostatic stress tensor, static short-term test, creep test, load controlled testing machine, combined Tension-/Compression-/Torsion-/Internal pressure test
Institute / chair: Technische Universität Darmstadt, Fachbereich Maschinenbau
Technical consultant for expert services: Prof. Dr.-Ing. Günter Mennig (Betreuer), Prof. Dr. J. Wissmann
Publication year: 1982
Provider: Wissenschaftlicher Arbeitskreis Kunststofftechnik (WAK) / Kunststoffe.de
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