Thermal effects when turning Al-MMC - experiments and simulations

车削 Al-MMC 时的热效应 - 实验和模拟

• 批准号: 260779103
• 负责人: Professor Dr.-Ing. Jan C. Aurich
• 金额: --
• 依托单位: Lehrstuhl für Fertigungstechnik und Betriebsorganisation (FBK)
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2017-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/260779103?language=en
• 关键词: Thermal; effects; when; turning; Al

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.

铝基复合材料（Al-MMC）是一种两相高性能材料。因此，由于其优异的性能，预计这些材料的使用量将增加。车削过程中产生的热量会引起工件和刀具的热膨胀，从而降低加工精度。为了确定和补偿这种变形，目前需要进行时间和成本密集的实验研究。由于Al-MMC是高成本材料，因此减少这类材料的实验工作是特别有意义的。在项目的第一和第二阶段，开发了有限元模型来计算车削铝和Al-MMC时工件和刀具的变形。在项目的第三阶段，将补偿车削复杂工件几何形状过程中的热效应。在材料模型中已经表示了异质的Al-MMC的介观尺度，以确定切屑形成的局部模型和工件的全局模型所需的材料特性。利用切屑形成的局部模型计算了工件和刀具的热通量以及加工力。这些结果作为工件和刀具的全局模型的边界条件。全局模型计算相应的温度分布、相关的热膨胀和由于过程力引起的变形。开发的有限元模型将用于项目的第三阶段，以确定复杂工件几何形状车削过程中热效应的补偿策略。之后，这些策略将被实验验证。通过确定工艺参数和减少工件和工具上的热负荷的各个操作的顺序来执行对加工精度的热影响的第一总体减少。因此，加工精度显著提高。由工件和刀具中的热效应引起的与标称工件几何形状的剩余偏差然后可以通过相应地适配的切削深度来补偿。为确保与标称直径的偏差最小化和适当的表面完整性，将考虑粗车和精车。使用CAD-CAM技术生成的刀具路径，这是适应的切削深度的结果，为实验研究。计算和实验测量的加工精度的潜在差异将通过多个实验结果进行分析，例如温度分布和过程力。作为该项目的结果，首次实验验证的有限元模型允许在车削铝和Al-MMC时进行工艺规划。因此，可以显著地提高加工精度。