Yuewei Ai

Cellular automaton modeling for dendritic growth during laser beam welding solidification process

A modified non-equilibrium cellular automaton (CA) model is proposed to simulate the dendrite growth along the fusion boundary under transient conditions during the solidification process of laser beam welding (LBW) pool. The main non-equilibrium solidification effects, including solute trapping, deviation of the liquidus line slope, and kinetic undercooling, are taken into consideration in this modified CA model. The evolution of dendrite morphology, concentration field, and velocity field was investigated. Four growth periods, i.e., the initial stable period, the instability period, the competitive growth period, and the short-term stable period, were observed during the solidification process of LBW pool. The dendrite growth patterns were different in these periods due to the transient solidification conditions. The solute distribution predicted by this modified CA model showed similar trends to that predicted by the previous phase field model. The dendrite tip velocity was significantly influenced by the thermal undercooling and constitutional undercooling in the LBW pool, and the tip velocity field can be divided into three stages, i.e., the planar growth stage, competitive stage, and short-term steady growth stage. In addition, further comparison between the simulated dendrite morphology and experimental dendrite morphology was performed. Results showed that the simulated morphology of dendrites agreed well with the experimental results. In particular, the primary dendrite arm spacing predicted by this model was in good agreement with that obtained from experiments.A modified non-equilibrium cellular automaton (CA) model is proposed to simulate the dendrite growth along the fusion boundary under transient conditions during the solidification process of laser beam welding (LBW) pool. The main non-equilibrium solidification effects, including solute trapping, deviation of the liquidus line slope, and kinetic undercooling, are taken into consideration in this modified CA model. The evolution of dendrite morphology, concentration field, and velocity field was investigated. Four growth periods, i.e., the initial stable period, the instability period, the competitive growth period, and the short-term stable period, were observed during the solidification process of LBW pool. The dendrite growth patterns were different in these periods due to the transient solidification conditions. The solute distribution predicted by this modified CA model showed similar trends to that predicted by the previous phase field model. The dendrite tip velocity was significantly influenced by ...

Prediction of weld bead for fiber laser keyhole welding based on FEA

Fiber laser keyhole welding as a popular metal joining process has been widely used in a variety of applications especially automotive, shipbuilding and aerospace industries. Although process parameters determination based on experiments is the frequently used in the practical welding, it is often a very costly and time consuming. Accurately predicting the weld bead without expensive trial experiments has great theoretical significance and engineering value for welding process parameters pre-selection. An innovative volume heat source model was proposed for weld bead geometry prediction through finite element analysis (FEA) in fiber laser keyhole welding. The hybrid heat source model consists of a double ellipsoid heat source and a 3D Gaussian heat distribution model. To validate the effectiveness of the proposed heat source model, the fiber laser keyhole welding of the stainless steel SUS301L-HT has been carried out in this paper. The main three parameters, laser power (LP), welding speed (WS) and focal position (FP) have been taken into consideration as the design variables. Both of the predicted values from the FEA and back propagation neural network (BPNN) are compared with the experimental results. The FEA predicted results achieve good agreement with experimental results of weld bead shape and dimension and are better than BPNN predicted results. The objective variation trend is also analyzed by two prediction methods. From the discussion, it is revealed that the proposed prediction method of weld bead is effective for fiber laser keyhole welding process and replacing the expensive experiments.Fiber laser keyhole welding as a popular metal joining process has been widely used in a variety of applications especially automotive, shipbuilding and aerospace industries. Although process parameters determination based on experiments is the frequently used in the practical welding, it is often a very costly and time consuming. Accurately predicting the weld bead without expensive trial experiments has great theoretical significance and engineering value for welding process parameters pre-selection. An innovative volume heat source model was proposed for weld bead geometry prediction through finite element analysis (FEA) in fiber laser keyhole welding. The hybrid heat source model consists of a double ellipsoid heat source and a 3D Gaussian heat distribution model. To validate the effectiveness of the proposed heat source model, the fiber laser keyhole welding of the stainless steel SUS301L-HT has been carried out in this paper. The main three parameters, laser power (LP), welding speed (WS) and focal ...