Project Details
Projekt
Thermal effects when turning Al-MMC - experiments and simulations
Subject Area
Metal-Cutting and Abrasive Manufacturing Engineering
Mechanics
Mechanics
Term
from 2014 to 2018
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 260779103
Aluminum-Metal-Matrix-Composites (Al-MMC) are two-phase high-performance materials. Hence, an increasing usage is predicted for these materials due to their excellent properties. The generated heat during turning causes thermal expansions of the workpiece and the tool, which decrease the accuracy of machining. In order to determine and compensate such deformations, time and cost-intensive experimental investigations need to be carried out at present. Since Al-MMC are high cost materials, it is of particular interest to reduce the experimental effort for this class of materials. In the first and second period of the project, finite element models to calculate the deformations of the workpiece and the tool when turning aluminum and Al-MMC were developed. In the third period of the project thermal effects during turning complex workpiece geometries will be compensated. The heterogeneous meso-scale of the Al-MMC has been represented in a material model in order to determine the required material properties for a local model of chip formation and a global model of the workpiece. The heat flux into the workpiece and the tool respectively as well as the process forces are calculated using the local model of chip formation. These results serve as boundary conditions for the global model of the workpiece and the tool. The global models calculate the respective temperature distribution, the associated thermal expansion and the deformation due to the process forces. The developed finite element models will be used in the third period of the project to determine strategies for the compensation of thermal effects in turning of complex workpiece geometries. Afterwards, these strategies are to be verified experimentally. A first general reduction of thermal effects on the accuracy of machining is performed by determining process parameters and sequences of individual operations that reduce the thermal loads on the workpiece and the tool. The accuracy of machining is thus remarkably enhanced. The remaining deviation from the nominal workpiece geometry, caused by thermal effects in the workpiece and the tool, can then be compensated through accordingly adapted depths of cut. To ensure both a minimized deviation from the nominal diameter and an appropriate surface integrity, rough turning and finish turning will be considered. The tool paths, which are the result of the adapted depths of cut, for the experimental investigations are generated using CAD-CAM technology. Potential differences in terms of the calculated and experimentally measured accuracy of machining will be analyzed by multiple experimental results, such as the temperature distribution and the process forces. As a result of the project, for the first time experimentally validated finite element models allowing for process planning when turning aluminum and Al-MMC will be available. The accuracy of machining can thus be remarkably enhanced.
DFG Programme
Priority Programmes
