[PLASTIC INSTABILITY IN PURE SHEAR]. Annual Report, Part III.

Polymer materials are gaining more and more importance in engineering applications. A new methodology of analysis is required in order to assess the capability of such material in withstanding complex loads. Therefore, the behavior of these materials currently arouses a great research interest. The use of PVC plastic pipes in pressure vessels and pipelines has increased rapidly in the last decade. In order to determine the plastic behavior of PVC, an experimental method is presented. Through the results obtained from experimental tests, in the first part of this paper, we investigate the use of a phenomenological model proposed by G’Sell and Jonas. The true stress-strain response under large plastic deformation was investigated in different stress triaxiality frameworks. Particular attention was given to volumetric strain evolution, separation resulting from elastic volumetric strain, plastic volumetric strain and pure shear. The effect of stress triaxiality on plastic instability and fracture strain was also examined. The deformation process should be considered as explained, and the anisotropic plastic response induced by the deformation could be introduced in constitutive equations of G’Sell.

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The Stress Triaxiality Effect under Large Plastic Deformation of a Polybutylene Terephthalate (PBT)

International Journal of Engineering Research in Africa ◽

10.4028/www.scientific.net/jera.34.13 ◽

2018 ◽

Vol 34 ◽

pp. 13-28

Author(s):

Abdel Nour Zaim ◽

Benattou Bouchouicha ◽

Hadj Miloud Meddah ◽

El Bahri Ould Chikh

Keyword(s):

Plastic Deformation ◽

Pure Shear ◽

Stress Triaxiality ◽

Volumetric Strain ◽

Plastic Instability ◽

Large Plastic Deformation ◽

Polybutylene Terephthalate ◽

New Generation ◽

Plastic Volumetric Strain ◽

Strain Responses

In this work, we focus on a new generation of polymer named Polybutylene terephthalate (PBT). In order to analyse and determine true behaviour of this polymer, a special experimental method was used. Hence, the true stress/strain responses are investigated under a large plastic deformation in different stress triaxiality frameworks with a particular attention on the volumetric strain evolution, with their decomposition to an elastic volumetric strain, plastic volumetric strain and the pure shear. Moreover, the effect of stress triaxiality on the plastic instability and the fracture strain is also examined. With the plastic instability analysis, it was found that plastic strain hardening increases gradually with the triaxiality. Finally, in order to evaluate the damage of this polymer, a theoretical damage formula is proposed.

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