Analysis of the heat input into the workpiece due to drilling and the resulting influences on the wall of the hole for 42CrMo4

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The third phase of the project focusses on an active geometric compensation of thermal deformations for a complex component with drilling holes for AISI 4140 (German Grade 42CrMo4). This goal will be achieved by a simulation-based design of machining strategies. An increase of complexity compared to the second phase of the project will be achieved by intersecting drilling holes in combination with further drillings on the component. With this example, the interactions of thermally and thereby mechanically induced effects can be represented much better during the drilling operation.To reach this objective, the simplified 3D-Model of a drilling operation achieved during the last period will be adjusted to the changed starting position and validated experimentally at the beginning. For this transfer step the modular model construction can be used to tailor each partial model to its specific application. As part of this work, the temperature terms implemented in the model for the heat input of the drill will be extended simultaneously for a universal design of the drill geometry. With the help of the advanced simulation model the overall heat balance which is responsible for the formation of residual stress and distortion states will be investigated by parametric studies. In this way essential information for the targeted generation of resiudal stresses and the resulting distortions can be obtained. A parametrization of the workpiece with respect to the distance of drilling holes will complete this workpackage. After the heat balance can be fully described, the investigation of the use of cold sources will follow aiming to minimize the distortion potential by controlled cooling of a simplified component. This cold sources are to be used to run after the manufacturing process, but also parallel to the production of further drilling holes. As a result of the calculations in the model the best times, places and intensities for the activation of the cold sources will be obtained. In a subsequent development step a circular milling model will be developed as a further method for compensating the residual stress and distortion conditions and tested again in the simplified component. With this model, drilling geometries will be examined in terms of roundness and orientation in order to derive compensation strategies for the distortion behavior resulting from controlled non-circular and curved drilling of the holes. This allows to produce holes and overall geometries, which are ideal after reaching the thermal equilibrium. In the final step, the active geometric compensation will be carried out under synergetic use of all gained insights and results and application of circular milling and cold sources for the complex component. At the end the effects of single or multiple compensation strageties will be vaildated experimentally.