The process of extrusion through square dies is widely used to produce profile sections. In recent years, the demand for complicated shapes has been increased and therefore the control of the process and the prediction of mechanical properties have become more important. Square die extrusion is normally carried out at the elevated temperature. Thus, the involved mechanics is basically non-steady and analysis should be made for the non-steady state throughout the entire process, which is not amenable to analysis due to the complicated metal flow in the non-steady hot extrusion process using a square die. Furthermore, the three-dimensional analysis is required, since the usual practical profiles are mostly asymmetric in the cross-sectional shape.
In the present study, two kinds of kinematic description have been used to simulate the hot square die extrusion processes. The updated Lagrangian FEM is applied to analyze hot square die extrusion without die land. To carry out the simulation of hot extrusion of profiles, an automatic remeshing technique with modular concept is proposed. An arbitrary Lagrangian-Eulerian(ALE) FEM has been developed for the analysis of hot square die extrusion. The finite element formulation is derived and implemented. Updating scheme of time dependent variables and mesh control are also examined.
In order to validate the FEM programs, experiments were carried out using AISI Al-1100 as the working material at the elevated temperature. The computed FEM results are compared with experimental results. The comparison shows that the computational results are generally in good agreement with the experiments in extrusion load, temperature distribution and deformed shape.
In square die extrusion of complicated profiles, land parts and flow guides play important roles in controlling the metal flow properly. The effects of lands and flow guides are investigated through the simulation of the process. As industrial examples, extrusion of a H-section with flow guide and the extrusion of a L-section without axis of symmetry have been simulated by using the developed ALE program. A scheme for the determination of die land length has been proposed. The calculated die land is in good agreement with the industrial design. When the flow guide and the die land are employed in the die system, the results exhibit more uniform velocity field. That is, extrusion with flow guide and with adequatedie land could improve product quality.
Through the numerical examples and the experiment, it has been shown that the present methods can be used effectively in analysis and die design of hot square die extrusion processes.
