A Wet Etching Method Coupled With Finite Element Analysis-Based Compliance Function to Determine Residual Stress in High-Speed Milling

Abstract

High-speed milling (HSM) is widely used in the automotive and aerospace industries in fabricating mechanical components. HSM induced residual stress may significantly impact fatigue life and the corrosion resistance of machined components. Traditional methods of residual stress measurement are very time consuming and expensive. In this paper we presents a wet etching approach to obtain strain as a function of slot depth introduced in the subsurface. The strain readings were collected from a strain gauge mounted on the specimen surface near the slot edge. A compliance function can be conveniently calculated by simulating slot cutting using a finite element method via a Legendre polynomial subroutine as the applied load. The calculated compliance functions and measured strain values at different depths were used as inputs into a program to calculate residual stress. This leads to a faster and less expensive method of determining residual stress when compared with the traditional methods. The capability of this new approach was demonstrated by high-speed milling 6061-T651 and 7050-T7451 aluminum alloys. A design-of-experiment method was used to conduct milling tests with three levels of cutting speed, feed rate, and DOC. Residual stress profiles with 12 data points with the spatial resolution as small as 1μm in the subsurface were then obtained. Residual stress sensitivity to cutting conditions was investigated. In addition, subsurface microstructure and microhardness were also measured to characterize surface integrity in a broad sense.