In-situ monitoring of wire ARC additive manufacturing

Abstract

Wire are additive manufacturing (WAAM) is based on Direct Energy Deposition (DED) method that creates the part by melting and fusion process. This process is having an advantage of high deposition rate with effective utilization of material which incorporates high heat energy input, which tends to severe heat accumulation with respect to the heat dissipation, which leads to structural dis integrity. The in-situ measurement is used to calibrate the heat accumulation. This thesis presents the analysis of the in-situ monitoring inter-pass temperature and control of the generated temperature to obtain the desired mechanical and geometrical properties, by means of numerical simulation. The investigation focus on the effect of the heat accumulation and the temperature field for various component used in the system, which is bead and substrate. The continuous deposit cause significantly raise in the peak temperature, and thus idle time is used as a controlling method. With initial deposition of layers, the temperature increases along the travelling direction, however at later stages the temperature at the leading edge of bead start to increase as compared to the trailing edge of the bead. The peak temperature of the immediate deposited bead initially increases steeply with the deposited number of layers and then tends to achieve the steady value. Similar increase of temperature is observed with the increase in heat input, which further tends to achieve the stead value irrespective of the heat input and layer number. The weld pool size shows an increasing trend with the increase in layer number, evidencing the increase in heat accumulation due to lower temperature gradient along the building direction. In addition, the study on the influence of the continuous and pillar assemble design substrate on temperature field were analyzed and observed the peak temperature of the pillar based substrate is higher than continuous bar substrate by 25 to 80˚C. Similar rise was observed in idle time by 45 to 90 seconds per layer, which evidences the slight increase in heat dissipation due to increased mass available for conduction in continuous bar substrate. The proportional relation is existed between the yield stress and the hardness property. Due to the variation in temperature distribution, the yield stress varies accordingly and thus the hardness. The observed hardness variation along the bead building direction were calculated at later chapter. Therefore controlling the bead temperature plays an important role in geometrical and mechanical properties.