Prediction of residually stress-induced warpage while machining aircraft monolithic parts

Various kinds of monolithic parts made of aluminum or titanium alloys have been widely used in the aircraft construction industry. Due to the complex shape, large dimension, thin cross-section and high cutting removal rate, monolithic parts prone to warp during manufacturing. The purpose of this study was to develop a methodology for predicting machining-induced warpage and the new residual stress redistribution in the remaining material while given the initial residual stress distributions. Finite Element Method(FEM) was introduced to predict residually stress-induced warpage in 7075T74 aluminum alloy specimens. A comparison of experimental and finite element results demonstrates favorable agreement. The methodology was used to analyze machining-induced warpage and the new residual stress distribution while machining monolithic parts. Experimental and FEM efforts have verified that initial residual stresses in aluminum alloy forging have detrimental influence on finished part geometry of monolithic parts. The magnitude of the warpage directly relates to the unbalanced forces established by the residual stress field. Given a known residual stress distribution, part warpage can be accurately predicted using finite element techniques.