Abstract

In recent decade high demand was observed for economical small-batch fabrication of components for aerospace, defense, and oil and gas industries. Wire Arc Additive Manufacturing (WAAM) is a promising candidate technology for replacement or supplement of conventional fabrication processes that rely on billets and forgings. However, WAAM-built parts suffer from residual stress and distortion, which limit wider application of WAAM in the industry. High-pressure post-build and inter-layer rolling was found effective to mitigate residual stress and distortion, but the mitigation mechanism is complicated and needs to be understood. Finite element analysis method proves robust and accurate for simulation of thermo-mechanical effects that occur during WAAM and rolling processes. However, large-scale post-build and inter-layer rolling simulations are challenging due to enormous computational cost. In this study an efficient modelling technique was developed for simulation of large-scale manufacturing processes through determination of steady-state solution using a reduced-size model and then mapping the solution to the full-size component. This technique has been successfully implemented for investigation of residual stress and plastic strain evolution during post-build and inter-layer rolling of a WAAM deposited wall. The numerical predictions were verified against experimental results. The tensile plastic strain induced by the rolling caused relaxation of the tensile residual stress generated by the WAAM deposition. Cyclic formation of tensile residual stress occurred during the WAAM deposition, whereas inter-layer rolling counteracted the residual stress development. The slotted roller induced larger magnitude longitudinal plastic strain and more efficiently reduced tensile residual stress in the WAAM wall, as compared to the flat roller. The residual stress, plastic strain and distortion were also compared for the rolled WAAM component before and after clamps removal. It was found that the clamps removal caused minor redistribution of residual stress in the post-build and inter-layer rolled components, since the rolling already mitigated the WAAM residual stress in the clamped condition.