An analysis by the finite element method of material deformation in equal channel angular extrusion

Deformation behavior of the work piece during equal channel angular extrusion (ECAE) processing is predicted using the commercial finite element code ABAQUS. ECAE has a number of advantages over conventional extrusion processes including nearly homogeneous deformation, the ability to develop a variety of microstructures and the ability to repeat the process without changing work piece cross-section and dimensions. Equal channel angular extrusion is a unique process which results in shear deformation via simple shear with a uniaxial compressive stress superimposed.; Initially, slip line theory formed the theory of ECAE and was limited to an ideal rigid plastic material model. However, proper design of the die requires the knowledge of the influence of variables such as friction conditions, realistic material models, and work piece geometry on the process mechanics. In order to obtain more realistic estimation of the stress and strain distribution throughout the work piece, it is necessary to analyze ECAE using an elastic-plastic model. This is accomplished herein using finite element models which are based on the principle of virtual work rate and include finite deformation.; Deformation of the work piece and punch pressure are strongly dependent on the number of elements used and die angle. The smoothness given at the die junctions (corner where shear plane begins) significantly affects the distribution of plastic strain as well as deformation of the work piece. The development of a gap or clearance between the work piece and the die is also a function of element size and die junction smoothness. Distortion of the work piece due to a limited length for the extrusion channel is due to the rigid body rotation and strongly depends on the material, the number of elements and the time increment for calculations.; The elastic-plastic analysis yields more reliable results in the elastic deformation region than the rigid plastic analysis. The numerical results for the perfectly plastic analysis with a die angle of 90{dollar}spcirc{dollar} shows good agreement with the theory of ECAE for punch pressure and the shear plane angle. However, the perfectly plastic analysis for a die angle greater than 90{dollar}spcirc{dollar} shows a deviation from ECAE theory as well as the development of a free surface near the junction of the die. Moreover, a free surface is developed for work hardening materials regardless of die angle.