Influence of Tool and Hole Diameters on the Accuracy of Measuring Machining-Induced Residual Stress of Aerospace Aluminum Alloy by Incremental Hole-Milling Method

Machining-induced residual stress(MIRS) have a large influence on distortion in thin-wall monolithic aluminum parts. Incremental hole-drilling method is widely used to measure MIRS versus depth, but there are few studies on tool and hole diameters of measuring MIRS below the rotation of 50000 rpm. In this study, different tool and hole diameters were discussed to evaluate their role in the accuracy and repeatability of measuring MIRS. In the meanwhile, a finite element mode(FEM) with dimensional of 25 × 25 × 1 mm3 cube sample was developed to predict distortion considering measured MIRS as initial stress state. At last, an experiment was conducted to validate the simulation results. Results show that the maximum normal and shear residual stress decreases 27.6 and 25.7%, respectively, when a hole of 2.0 mm in diameter is made using a cemented carbide end mill of 2.0 mm in diameter compared with that using a cemented carbide end mill of 1.5 mm in diameter by orbital technology. Outliers appear when hole diameter exceed more than 2.0 mm, and the standard deviation of maximum normal residual stress increases 88.7%. Based on residual stress measurement, measured and calculation distortion results, a cemented carbide end mill of 1.5 mm in diameter by milling a hole of 2.0 mm in diameter through orbital milling technology is recommended to measure MIRS, and the calculated distortion is the most consistent with measured distortion.