Plastic deformation and damage of polyoxymethylene in the large strain range at elevated temperatures |
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Authors: | J Mohanraj IM Ward A Dahoun C G'Sell |
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Affiliation: | a School of Mechanical Engineering, University of Leeds, Leeds LS2 9JT, UK b IRC in Polymer Science and Technology, School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK c Ecole des Mines de Nancy, INPL, Parc de Saurupt, 54042 Nancy, France |
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Abstract: | The deformation behaviour of polyoxymethylene has been studied in plane strain compression at temperatures from 120 °C up to 165 °C and in uniaxial tension and simple shear at 160 °C for strain rates from 10−4 to 1 s−1. In uniaxial tension the stress-strain behaviour was determined by a novel video-controlled testing system. The measurements showed that there was a very significant evolution of volumetric strain, indicating that damage mechanisms play a key role in the plastic deformation behaviour.All tests showed similar deformation stages with a short region of visco-elastic behaviour followed by a rounded yield point. The von Mises equivalent yield stress for these tests showed a linear relationship with logarithmic strain rate, suggestive of an Eyring type thermally activated process. After yielding, all stress-strain curves showed a long plastic deformation regime, which in shear occurred at constant stress. In plane strain compression there was also only a very small increase in stress, in contrast to uniaxial tension where very significant strain hardening was observed at high strains, which is attributed to the onset of structural changes. |
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Keywords: | Polyoxymethylene Plastic deformation Damage |
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