Residual Stresses and Optimizing Machining Strategies for Aluminum Bars

R stresses have a major impact on the ability to fabricate dimensionally accurate machined components from aluminum wrought mill products. In addition, the ability to implement advanced assembly technologies such as determinant assembly, where parts are indexed to each other rather than to expensive assembly tooling, is compromised when the parts are not dimensionally accurate. An active research project on this subject is underway in which NCNR scientists are collaborating with Alcoa and Boeing. The current status of this project is outlined in this report. In this work, finite element methods (FEM) are being used to predict residual stress profiles and to examine the influence of material processing and machining approaches on part distortion. However, although Alcoa is developing new destructive methods to estimate residual stresses in bulk materials, the neutron diffraction capabilities of the NCNR for characterizing residual stresses is key to validating both the FEM calculations and the measurement technique being developed at Alcoa. Ultimately, the goal is to understand the generation of residual stresses and how to control their effects in manufacturing and to correlate model predictions with actual experimental measurements. This information is critical in achieving optimization of the Residual Stresses and Optimizing Machining Strategies for Aluminum Bars