Control of residual stress in inter-layer hammering hybrid arc-based directed energy deposition manufacturing of cross-structure based on finite element method

Using arc-directed energy deposition (ADED) to manufacture parts with cross-structures is common in the aviation field. Inter-layer hammering with lower load demand has proved to be a promising technology to improve the microstructure and mechanical properties. At present, the residual stress (RS) evolution mechanism during inter-layer hammering hybrid ADED of the crosse-structures is not clear. In this study, a finite element model for inter-layer hammering hybrid ADED is developed to simulate two distinct hybrid manufacturing strategies for cross-structure: Alternating Inter-layer Hammering (AIH) and Complete Inter-layer Hammering (CIH). The accuracy of the hybrid model has been validated through assessments of thermal history, residual stress (RS), and warping. The hammering-introduced tensile plastic strain mitigates the compressive plastic strain caused by the cross-structure shrinkage during the deposition process and then reduces the tensile stress. The "Stress self-relief" helps to reduce the magnitude of stress under the CIH. Compared to the cross-structure manufactured by ADED alone, the stress at the cross-position is reduced to 79 Mpa and 39 Mpa under AIH and CIH strategies, respectively, from an initial 164 Mpa. Additionally, both of the two hammering strategies eliminate warping in the crosse-structure.