NSF/DFG Collaboration to Understand the Prime Factors Driving Distortion in Milled Aluminum Workpieces

薄壁铝工件在铣削过程中由于工件内部的残余应力而变形。变形降低了加工精度。变形需要时间密集和昂贵的返工或可能导致拒绝。在这个建议中，我们将研究如何薄壁整体工件的变形可以控制铣削时。进行了实验研究，并开发了用于预测工件变形的有限元模型。进行干铣削实验以产生关于变形现象的基本知识。这些实验为有限元模拟提供了定量数据。工件的变形分析与多个参数。这些因素是切削条件、工件几何形状、夹紧装置以及初始体残余应力的大小和分布。实验结果允许所需的有限元模型的边界条件的规格。此外，实验和数值计算结果可以连续比较，以评估有限元模型的能力。采用X射线衍射法和等高线法测量残余应力。通过比较两种方法的检测结果，可以更好地评价两种方法的检测能力。这有助于建立或进一步改进方法。工件变形是由体应力和加工残余应力引起的。两者都将在有限元模型中考虑。通过数值计算和实验结果，我们将探讨体应力和加工诱导应力对变形的影响。将确定可能的应力状态，其中仅体残余应力、仅加工残余应力或体残余应力和加工残余应力的组合限定变形。数值生成的铣削策略实验用于研究补偿或抵消批量残余变形的可能性。该研究项目的结果是显着提高加工精度，效率和可持续性铣削薄壁整体工件。

Thin-walled workpieces of aluminum are distorted during milling due to the residual stresses inside the workpiece. Distortion reduces the machining accuracy. Distortion necessitates time-intensive and expensive rework or can result into rejection. Within this proposal, we will investigate how the distortion of thin-walled monolithic workpieces can be controlled when milling. Experimental investigations are carried out and a finite element model for the prediction of the distortion of the workpiece is developed. Dry milling experiments are conducted to generate fundamental knowledge about the distortion phenomena. These experiments provide a quantitative database for the finite element simulations. The distortion of the workpiece is analyzed with regard to multiple parameters. Those are the cutting condition, the workpiece geometry, the clamping device, as well as the magnitude and distribution of the initial bulk residual stress. The experimental results allow for the specification of required boundary conditions for the finite element model. Moreover, experimental and numerical results can be continuously compared in order to evaluate the capability of the finite element model. The x-ray diffraction method and contour method will be applied to measure the residual stresses. The comparison of the results will facilitate the evaluation of the capability of both methods. This helps to establish or further improve the methods. Workpiece distortion is induced by both bulk and machining residual stresses. Both will be considered in the finite element model. With the numerical and experimental results we will explore the significance of the bulk and machining induced stress for the distortion. Possible stress regimes will be determined, where bulk residual stresses only, machining residual stresses only, or a combination of bulk residual stresses and machining residual stresses define the distortion. Numerically generated milling strategies are experimentally used to investigate the possibility to compensate or counteract bulk residual distortion. The result of the research project is a significant improvement of the machining accuracy, the efficiency, and sustainability in milling of thin-walled monolithic workpieces.