Study of distortion on milled thin-wall aluminum parts influenced by initial residual stress and toolpath strategy

Abstract

Monolithic aluminum alloy parts are highly required in the aeronautical industry, but they show significant geometrical distortion after the machining process. This work investigated the distortion attributed by the initial residual stress of the raw material and the machining-induced residual stress during the milling process, as well as exploring the effects of the machining toolpath strategy. Single-/multi-pocket parts were milled from 7050-T7451 aluminum blocks with different initial residual stresses, and an element deletion method was developed for the numerical study to simulate different sequences of material removal. It was revealed that the toolpath parallel to the long side of the block caused more distortion on the side surfaces of the final part. The value of distortion was positively correlated to the magnitude of the initial residual stress of raw material. The simulation results indicated that the distortion attributed by machining-induced residual stress accounted for about 15% of the final distortion. The finding promotes the design optimization of machining monolithic parts by minimizing distortion, thereby benefitting the application of large monolithic parts in industry.