Characterization of Machining Distortion due to Residual Stresses in Quenched Aluminum

Abstract

Manufacturing methods and procedures are advancing through research and development, to optimize machine tools, machining strategies, and the overall manufacturing system. In the aerospace industry, machining distortions, or the deviation of part shape from the original intent after being released from a fixture, occur, reducing productivity. Residual stresses locked into the workpiece are a primary factor contributing to machining distortions. The residual stresses are induced by prior material processing steps such as rolling, forging, heat treating, etc. — which are needed in the aerospace industry for high strength. Machining distortions result in significant economic losses due to reworking, remanufacturing, and/or rejecting components in the manufacturing and aerospace industries. Quenched 7050 T74 aluminum was used to investigate material removal with respect to milling distortions. Using material with a known residual stress profile, a prismatic u-shape geometry was machined and distortions were characterized, quantified, and described in detail. This paper shows a transparent and repeatable method for characterizing distortion for machined parts. The results from the distorted u-shapes indicate similar characteristics from distortion due to bulk residual stresses and machining factors.