On-line Spectral Diagnosis Of Arc Features And Porosities In Aluminum Wire And Arc Additive Manufacturing

Large aluminum component applied to aerospace has the trend to complicate, and traditional manufacturing technology couldn't meet its requirements. Wire and Arc Additive Manufacturing(WAAM) has an advantage in manufacturing simple, large components for its high deposition efficiency, material utilization and low cost. In recent years, many research results have been achieved on its process shaping, microstructure, mechanical properties, however WAAM hasn't been widely applied, because its process stability requires to be improved. On-line monitoring of it is the key to ensuring that this technology can be widely used. In this research, the radiation spectrum of the Aluminum WAAM plasma/high temperature steam was collected and analysed to find the physical mechanism of the technology and explore the feasibility to detect manufacturing defects online. The main results are listed as follows.Firstly, a spectral collection system of Aluminum WAAM plasma was developed. An algorithm for background removal based on discrete wavelet transform was first used to process the spectroscopy of arc welding to improve the accuracy, when the wavelet basis was db7 and the wavelet decomposition level was 5, the continuum spectrum could be removed.Secondly, the influence of welding parameters on WAAM spectroscopy was investigated. The characteristics of this technology corresponded to spectroscopy. The concrete conclusions are listed as follows: 1) The spectral parameters increased as the current increased. The electron density decreased at the first few layers, because the temperature of metal increased as the heat input accumulated and the work function decreased. 2) The spectral intensity dropped severely as ILH increased, the electron density and the electron temperature dropped in different degree. The spectral parameters of the anode and cathode were the strongest in the arc, and the raise of ILH led the detecting position away from the cathode, so the spectral parameters decreased. 3) No obvious relationship was found between spectroscopy and shielding gas flux.In the end, the relationship between the intensity of H I 656.28 nm and porosity was explored by prefabricating pollution. The research proved that on-line monitoring of porosities in WAAM by spectroscopy was feasible. When no pollution was imposed, the intensity of H I 656.28 nm was between 100 and 400 counts, the radius of porosity was between 20 and 40 ?m.When low melting-point liquid material was preset, the size of the porosities and the intensity of H I 656.28 nm was similar to the pollution-free sample. When the process was disturbed by solid lubricant, the intensity of H I 656.28 nm and porosity ratio increased.