Cold rolling influence on residual stresses evolution in heat-treated AA7xxx T-section panels

This article describes a novel cold working method for relaxing residual stresses in extra-long quenched T-section panels. Distortion led by quench-induced residual stresses in components is usually a great concern for the aviation industry. In this study, the influence of cold rolling on the residual stresses in a scale-down quenched AA7050 T-section specimen is experimentally and numerically investigated. An integrated numerical model was built to predict the quenching and the subsequent cold rolling processes. High levels of compressive stress around the surfaces of quenched T-profile specimens and the tensile surface residual stresses (RS) in the quenched and cold rolled specimens were predicted via numerical analysis, the surface stresses magnitude and distribution have, therefore, been quantified via X-ray diffraction (XRD) technique. The deflection of quenched specimens experienced 1.5% and 3% cold rolling was measured as well. In addition, to examine the cold rolling effect on the mechanical properties of T-profile specimens, hardness tests were carried out on quenched and cold rolled T-section specimens. It concludes that with 1.5% cold rolling the residual stresses in the core part of quenched material can be effectively relieved to an extent of lower than 83 MPa, with limited change for the material properties.