Further Development of a Predictive Tool for Managing Distortion in Electron Beam Additive Manufacturing

Residual stress and shape distortion are inherent features of wire-feed Electron Beam Additive Manufacturing (EBAM) due to the high thermal gradients associated with the high deposition rates. Uncontrolled distortion can cause deviation from tolerances for dimensions of built parts and lead to high rejection rates. As a result, parts may require stress relief heat treatments during deposition which can add to costs. Accurate predictive models of residual stress and distortion are of high interest as crucial tools in the development of active methods for distortion control and management. CSIRO and Boeing have collaborated to develop a tool named C-THRU^TMthat has been successfully applied to predict residual stress and distortion and to manage post-build distortion for a T-shaped part. Residual stress measurements by neutron diffraction have validated the predictive tool.

In this paper, the application of C-THRU^TM to further predict post-build residual stress and distortion in a complex 3D geometry Ti-6Al-4V part, designed by GKN, and built by EBAM, is described. Predicted post-build distortions are in good agreement with those measured from experimental builds. The results provide an understanding of the evolution of temperature, deformation, stress and clamp-induced reaction forces during and after completion of the build. Some challenges faced by machine operators during building parts having large and complex geometry by this process are also discussed.