Numerical and experimental investigation of HDPE behavior during 2-ECAP process using 90° and 120° dies

Abstract

Among various severe plastic deformation methods, equal channel angular pressing (ECAP) is an effective tool to introduce large plastic deformation of simple shear. The principle consists to extrude the sample several times through two intersecting channels with the aim to improve the mechanical properties of the material by altering the morphology of its microstructure. In this work, a numerical and experimental investigation of a typical semi-crystalline thermoplastic polymer (high density polyethylene, HDPE) during two-turn ECAP (2-ECAP) using 90° and 120° dies has been presented. The warping of the extruded samples has been also highlighted experimentally. The material parameters of an elasto-viscoplastic constitutive law were identified using compressive tests at different temperatures and strain rates. The effects of the main parameters, such as, the channel angles, the dimensions of the intermediate channel, the friction and the temperature have been analyzed. Finally, to confirm the numerical results, two dies composed of one elbow (1-ECAP) and two elbows (2-ECAP) have been manufactured and tested. It was found that the warping obtained using 2-ECAP die is more reduced than that of 1-ECAP die even with several passes.