Issue 51

M. S. Bennouna et alii, Frattura ed Integrità Strutturale, 51 (2020) 254-266; DOI: 10.3221/IGF-ESIS.51.20 255 Nowadays it is evident that the numerical approach completes the experimental one in the research activity. In this context comes the present study which completes a detailed experimental study of the effect of CGP on polymer (PA66) was carried out and published by Bennouna et al [1]. Note that the CGP process is performed with two tools, a corrugating one for applying intense plastic deformation to material and a straightening one to restore the straight shape of the sample. This study applies the FEM (finite element method) approach which is widely applied by researchers. Among the most successful applications this method we find the modeling of the deformation of material [2-5]. Noting that deformation, rate of deformation and chemical composition are parameters which have a significant effect on the mechanical properties of the material [6, 7]. Many phenomenological models have been used to simulate the intense plastic deformation of polymeric materials such as those used by Bardenhagen et al [8], Frank and Brockman [9], Colak [10] and which has been by several researchers such as Aour et al. [11-13], Mitsak [14] and Draï and Aour [15] and that used by Estrin et al and improved by Mckenzie et al [16] and also by Hosseini and Kazminezhad [17]. Simulating intense deformations such as those induced by the CGP process using finite element is a very complex operation that those of small deformations because introducing simple definitions such as isotropic hardening or perfectly plastic conditions do not lead to precise results to see acceptable [ 18]. To describe the plastic deformation behavior of polymeric materials many constitutive models have been used by searchers to simulate semi crystalline Polymers with a finite element tool such as abaqus. In general these models are based on the additive decomposition of the strain rate tensor d into an elastic part d e and a viscoplastic part d vp : d = d e + d vp Note that a single pressing of CGP process yields a shear strain of  =h/h =1 (where h is the groove wide) at deformed region. This is equivalent to an effective strain ε eff = 2 4 2 3        = 0.58 But the present simulation was carried out by injecting into the modeling; the true parameters extracted from the experimental tests and corrected using the correction factor of the machine which leads to engineering values. For this reason, experimental tensile tests were performed on PA66 samples to obtain the stress-strain curve shown in Fig. 1 [1]. Figure 1 : Stress-strain curve obtained from a tensile test on PA66 polyamide [1].