Analysis of plastic deformation of semi-crystalline polymers during ECAE process using 135° die

Abstract

In this paper, analysis of plastic deformation of high density polyethylene (HDPE) and polypropylene (PP) during an equal channel angular extrusion (ECAE) process is investigated. The effects of ram speed, number of passes, processing route and temperature are tested experimentally using a 135 • die. The results show that the pressing force decreases with an increase in the number of passes and reaches a saturation state rapidly for routes A and C compared to routes B A and B C. Furthermore, it is found that the reduced curvature of the extruded samples is obtained by route C, however, the maximum warping is obtained by route A. A slight influence of temperature on the reduction of the warping is observed on the extruded samples. In order to predict the plastic strain inside the extruded samples, an elastic viscoplastic model is identified using compressive tests at different strain rates and coupled with the finite element method (FEM). A good correlation is found between the numerical modeling and experimental findings. FEM results show that the PP samples display a higher level of plastic strain compared to HDPE samples. However, almost the same degree of strain heterogeneity is obtained for both polymers. Finally, in order to reduce the warping and improve the strain homogeneity, a controlled back-pressure with small corner angle is expected to be an adequate solution.

Experimental Investigation of Mechanical Behavior of a Polyamide before and after Constrained Groove Pressing Process

“…Nowadays polymers are replacing metallic materials in many domains of the industry; they have been widely used in different applications such as mechanical components and electronic devices as covers, coupler, gears, etc., due to their relatively low cost of manufacture and variability [28]. In this context, SPD technique, especially ECAP process, has been largely used to improve the mechanical properties of the polymers and several papers have been published on different polymeric materials, such as, low density polyethylene (LDPE) [29], Polycarbonate (PC) [30]- [32], Polyethylene terephthalate (PET) [33], [34], polymethyl-methacrylate (PMMA) [35], High Density Polyethylene (HDPE) [36]- [38], Polypropylene (PP) [39], [40], and others.…”

Experimental investigation and modelling of hot forming B4C/AA6061 low volume fraction reinforcement composites

“…The resultant bar or sheet often requires secondary manufacturing operations to produce the final product geometry. It is advisable to perform such manufacturing processes on MMCs at elevated temperatures where ductility is higher and forming load is lower (Aour and Mitsak, 2016). This combination increases manufacturing capability and results in an increased material yield compared with machining to achieve final part geometry.…”

Numerical investigation of the effect of constrained groove pressing process on the mechanical properties of polyamide PA66

“…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][12][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].…”