Issue 51

M. S. Bennouna et alii, Frattura ed Integrità Strutturale, 51 (2020) 254-266; DOI: 10.3221/IGF-ESIS.51.20 256 Figure 2 : Different phases that the sample undergo during the tensile test. Fig. 1and Fig.2 show that the deformation of the material passes through three different phases: the first (I) is a phase of elastic deformation, the second (II) is a phase of plastic deformation with a low strain hardening, and in the third phase (III), a softening was noted (stress drop) which results of the high ductility of this polymer, which determines a fast lowering stress, but this is due to the use of engineering strains. Data of this experimental curve are used for the numerical simulation. M ATERIAL AND METHODS he simulations were run using Abaqus, an FE tool. The initial dimensions of the PA66 sample used are the same as those used in the experimental study carried out and published by Bennouna et al (87 × 45 × 3 mm), (2018) [1] . The same boundary conditions were also used with a mesh of 4935 4-node quadrilateral elements of the CPE4R type (four- node plane strain element) (Fig. 3). Note that true strains values are used for the simulation and not nominal values. Figure 3 : Finite element discretization of samples. As shown in Fig. 4 pure shear occurs in the inclined areas of the sample but some regions remain undeformed, which means that the microstructure has certain heterogeneity (Fig 5). To overcome this disadvantage and introduce a uniform deformation in the workpiece, the sample is placed on the right side of tool during one cycle and then pushed to the left side during the next cycle. The friction metal/polymer was considered in the simulation although the surfaces of the dies and samples were polished to reduce it. T