Experimental and numerical study of ECAE deformation of polyolefins

Equal channel angular extrusion (ECAE) is a relatively novel deformation process used to produce severe plastic deformation by simple shear of materials with the aim to improve their mechanical properties. In this study, the influence of ram speed, friction, processing route, number of passes and back-pressure on pressing force and inhomogeneous behaviour during ECAE of high density polyethylene and polypropylene was investigated by finite element modelling (FEM) and experimental testing. Digital image correlation method was used to measure the surface deformation of the sample during ECAE process. A good correlation was found between the FEM simulations and the experimental results. The strain distribution is not homogeneous and a large residual curvature is remaining after complete extrusion without back-pressure. In order to improve the homogeneity of strain distribution, it is suggested, based on the present results, to use a tool with a low corner angle in combination with the application of a back-pressure on the sample end at the exit channel.