Thermomechanical Analysis and Experimental Validation of ECAP for Aluminum Sheet Metal

Equal-channel angular pressing (ECAP) is an established method for the improvement of mechanical properties by grain refinement through shear strains. While there is a profound knowledge about ECAP of bulk materials, there is only a little information on the effect of ECAP on sheet metals. Therefore, a tool was developed that is able to perform ECAP tests for metals with a thickness of 1.8 mm. In this contribution, a thermomechanical simulation model is used to examine the novel process. The simulation is performed to investigate the dissipated forming heat and the heat due to friction. To validate the numerical results, experiments with the ECAP tool for sheet metal are performed. By drilling holes in the sheet material, the forming temperature can be measured with thermocouples and friction parameters used in the simulation can be calibrated inversely. Since a detailed material model is essential for the inverse determination of individual parameters, a special focus of this article is on the determination of the thermomechanical parameters. For example, the plastic flow behavior or thermomechanical conversion, expressed as the Taylor–Quinney coefficient, is examined under a stress state similar to ECAP by means of a Miyauchi test. In this way, fundamental correlations between the heat development in the ECAP process for aluminum sheet metal and the shear strain introduced into the material can be obtained.