Simulation-Based Investigation of the Distortion of Milled Thin-Walled Aluminum Structural Parts Due to Residual Stresses

Abstract Nowadays, aluminum components in aircraft are mainly found in the form of thin-walled monolithic structural parts of the internal fuselage and the wings as spars and ribs [1]. This is because these components have excellent material properties for lightweight applications, such as a high strength-to-weight ratio and good corrosion resistance [2]. A typical manufacturing process to produce such structural components is milling. For these weight-optimized, monolithic components, up to 95% of the material is removed by machining [3]. The challenge with these thin-walled structural components, which are up to 14 m long, is that part distortion can occur because of the manufacturing-specific process chain [4]. Residual stresses due to machining and upstream processes such as forming, and heat-treatments are known to be the key factor for causing those distortions [5]. In this research the effect of the residual stresses, the machining strategy, the part topology and the geometry, including the wall-thickness, on distortion were investigated experimentally, and simulatively by validated virtual models based on the finite-element method. Those models can then be used to predict the distortion. At the end distortion minimization techniques were derived.