Thermo-Mechanical Behavior of Multi-Layer Deposition for Wire Arc Additive Manufacturing of Structural Steel: Wire Arc Additive Manufacturing

Wire arc additive manufacturing (WAAM) process, following the directed energy deposition (DED) technique, has evolved as one of the most prominent additive manufacturing (AM) technologies to fabricate large and intricate shapes of metallic components. The physical basis of the WAAM process is associated with rapid heating, melting, layer-by-layer melt deposition, solidification, and moderate cooling rate of the fabricated part. Consequently, different regions of the additive manufactured part experience variable heating and cooling cycles due to repeated heating and cooling. The continuously varying transient thermal cycles lead to residual stresses and distortion in fabricated components, mainly influenced by the temperature gradient along the build direction. The generation of residual stress and distortion result in warping, delamination, and unfavorable fatigue properties of the AM components. The in-situ prediction of transient temperature profile and its impact on residual stresses in an arc-based DED technique is practically impossible by any contact measurement technologies. As the cooling or idle times between the successively deposited layers play a significant role in the thermomechanical behavior of as-deposited materials, the inclination towards developing a numerical model by considering different process variants in the layer-by-layer deposition process is evolving. In the present work, a finite-element-based thermo-mechanical 3D model is developed for the WAAM process by triggering the effect of the inter-pass cooling period. The model results are validated with experiments reported in independent literature. Increasing the inter-layer dwell time decreases built material’s peak temperature and residual stress. At the same time, the distribution of effective stress along the built material’s center line increases with idle times.