Prediction Of Solidifaction Defect In Electron Beam Welding

Many advantages of the aluminum alloy meet the requests of the aviation, space navigation and petroleum chemical industry. Such as low density, high electrical and thermal conductivity, good corrosion resistant and processing preferment. For its high thermal capacity, conductivity and latent heat, electron beam welding is the one of the best methods employed in the welding of large aluminum alloy plate because of high energy density, small heat-affected zone and low pollution etc.The existance of the shrinkage cavity in the electron beam welding, is one of the most important factors in the engineering practice. So it has very important meaning to analysis the formation of the shrinkage cavity.Finite element model for analysis formation of the shrinkage cavity is set up based on ANSYS software code, 20mm 5A06 aluminum alloy as the research object. The prediction criterion of the shrinkage cavity is G / R ? ?k ?T / DL, which is based on the the relationship between the dendrite liquid flow and the temperature field. Accompanying with contraction potential, compiled with APDL language, the criterion decides whether the shrinkage cavity forms.The temperature field is simulated with two different heat sources. Simulation of molten pool shape and trim welding line are well consistent with the experiment, which validate the applicability of the composite heat source model, composed of gauss and fitting parabolic heat source, in electron beam welding.The shared-memory parallel performance in ANSYS 12.1 is set up in order to simulate with less time, which can save time 20%. At the same time, different grid size, focus current, welding velocity and beam current are considered the factors on the size, position and distance of the shrinkage cavity. The results show that, the grid is finer, the size of the shrinkage cavity is closer to the experiment value. While the coarse grid is only fit for simulation of large shrinkage cavity. Under coarse grid, as the focus current increases, the equivalent points of the deficit reduce after the first increase. As for the relationship with beam current, the points increase after the first reduce. With the increment of the welding velocity, the points increase. The position of the shrinkage cavity most focuses on the bottom of the molten pool and has a periodicity. The experiment shows that the formation of the shrinkage cavity has a relationship with the weld appearance. The points of the deficit and the distance between the shrinkage cavity decrease with the weld wave more evenly and fine.Compared to the experiment values, the simulation errors of the shrinkage cavity size is 8.76% in melt depth, 23.46% in melt width while the grid size is 0.1mm×0.1mm×0.1mm. the simultation results present in this study are found to be in good agreement with the experiment values.