A hybrid finite element analysis of shot peen contour forming using residual stress measurements

Abstract

In order to develop surfaces that have the proper curvature for aerospace structures, it is sometimes necessary to use shot peen forming, also known as contour forming, to create the desired shape in a piece of metal. Since the preferred metal in aerospace continues to be aluminum and its alloys, this study will concentrate on the effects of shot peening on aluminum. Typically, shot intensity is measured using standard Almen strips made from cold rolled SAE 1070 spring steel. Since the effects of the shot on aluminum is the chief concern of this study, aluminum strips of the same size and thickness will be used to determine the intensity of the shot on aluminum parts. These strips will be exposed for different amounts of time to different intensities, measured using the steel Almen strips, and then the intensity (or arc height) will be measured on the aluminum strips. The residual stresses in these strips will then be measured using the hole drill method (ASTM E837). The stresses from the residual stress test will then be used to develop a finite element model that simulates the aluminum strips and the deformation in them. The model will then be calibrated with the empirical data. From there, it will be the goal of this study to be able to predict the deformation of aluminum parts when exposed to certain shot peen intensities. This will enable more efficient contour forming processes with less rework. Furthermore, the trial and error of a manual process can be avoided with the use of robotics. Robotics/Automation can also help in creating more consistent results.