Numerical Simulation Of Temperature Field,Stress Field And Deformation During Wire-arc Additive Manufacturing

Wire-Arc Additive Manufacturing(WAAM)is a kind of additive manufacturing technologies which uses arc as heat source to melt wire for directional deposition.In recent years,WAAM has gradually expanded from aerospace to general civil industrial manufacturing with its advantages of low cost and high flexibility with the increase in use of precious and difficult-to-machine metal materials and customized complex structures.However,the complex temperature field caused by the local and repeated heating characteristics of heat source in the process of WAAM makes the structures have high residual stress and significant macroscopic deformation.The distribution of residual stress will be more complex and the deformation will usually be larger with the increase of the forming size.The performance and appearance of the WAAM parts will be reduced by residual stress and macroscopic deformation which will even directly lead to manufacturing failure.Therefore,WAAM has not yet realized the engineering application of large structure and further basic research is still needed.As a fundamental research,based on MSC.Marc finite element software,a thermal-elastic-plastic finite element calculation method considering both material nonlinearity and geometric nonlinearity was developed to simulate temperature field,stress field and deformation in MIG-WAAM structures with Q345 as the substrate and Y309 L as the deposition material.The evolution law of temperature field,stress field and deformation in process of linear and circular thin-walled structural parts and multi-layer and multi-pass WAAM was simulated by the method and the rationality of the numerical simulation results is verified by experimental means.Based on the numerical simulation results,the effects of deposition sequence,number of deposition layers and inter-pass temperature on temperature field,stress field and deformation of linear thin-walled parts during the WAAM were discussed.The effects of substrate thickness and inter-pass temperature on temperature field,stress field and deformation were also discussed in the process of multi-layer and multi-pass WAAM.The results show that in the continuous WAAM,the accumulation of heat inside the substrate and deposited materials increases rapidly which leading to the peak temperature and average temperature experienced by the deposited material gradually increase,while the cooling rate gradually reduce with the increase of depositing layers.The deposited material will undergo multiple stress cycles with the change of temperature during the process of WAAM.The stress of the deposited layers will be significantly affected by the subsequent deposition process due to the softening effect of the temperature field generated by the subsequent deposition material on the adjacent deposited layers.The numerical simulation results show that the final deposition layer has the most significant effect on the residual stress of the part.After the completion of WAAM,the longitudinal tensile residual stress is mainly distributed interior of linear thin-walled part and there is a large stress distribution gradient on both sides of the part.Meanwhile,the number of deposition layers and inter-pass temperature have a great influence on the stress distribution.The stress distribution of circular thin-walled part is that the compressive stress at the bottom inner wall side is balanced with the tensile stress at the outer wall side.The central position is mainly circumferential tensile residual stress and the top position is mainly circumferential compressive residual stress.The overall deformation of linear thin-walled structure is longitudinal bending deformation while the circular thin-walled structures is up-warping around the substrate and sinking inside,the circular deposition layers gradually indent in the radial direction with the increase of layers.For the multi-layer and multi-pass WAAM in this study,the heat accumulation rate inside the substrate and part more rapidly while the cooling rate of the material more slowly compared with the two kinds of thin-walled parts.After the completion of WAAM,the longitudinal tensile residual stress is mainly distributed inside the part and the transverse tensile residual stress is mainly distributed on the upper and lower surfaces of the substrate.The increase of substrate thickness can effectively increase the cooling rate of the deposited material and reduce the deformation of substrate.Meanwhile,the inter-pass temperature has certain influence on both the distribution and the magnitude of residual stress,but it has limited influence on the angular distortion of the substrate.