Neil S. Bailey

Investigation of keyhole plume and molten pool based on a three-dimensional dynamic model with sharp interface formulation

Laser keyhole welding is a complicated multi-phases, multi-physics process, especially when assisting gases are involved. A three-dimensional transient model is developed to investigate the dynamics of keyhole, together with the vapour plume and molten pool, in a self-consistent manner. The model features the utilization of sharp interface method for accurate consideration of the complex surface phenomena on the keyhole wall and a comprehensive hydrodynamic calculation for both the vapour plume and molten pool. The model is validated against experiments and the simulation results are discussed. It is found that the interplay of the multiple reflections and the plume attenuation due to particle absorption/scattering is crucial for the laser absorption intensity and hence the temperature on the keyhole wall, and the keyhole wall temperature distribution has profound influences on the fluid flow and temperature/species distributions in both the molten pool and keyhole plume.

Numerical Modeling of Transport Phenomena and Dendritic Growth in Laser Spot Conduction Welding of 304 Stainless Steel

A multiscale model is developed to investigate the heat/mass transport and dendrite growth in laser spot conduction welding. A macroscale transient model of heat transport and fluid flow is built to study the evolution of temperature and velocity field of the molten pool. The molten pool shape is calculated and matches well with the experimental result. On the microscale level, the dendritic growth of 304 stainless steel is simulated by a novel model that has coupled the cellular automata (CA) and phase field (PF) methods. The epitaxial growth is accurately identified by defining both the grain density and dendrite arm density at the fusion line. By applying the macroscale thermal history onto the microscale calculation domain, the microstructure evolution of the entire molten pool is simulated. The predicted microstructure achieves a good quantitative agreement with the experimental results.

Optimization of Laser Hardening Processes for Industrial Parts With Complex Geometry via Predictive Modeling

A predictive laser hardening model for industrial parts with complex geometric features has been developed and used for optimization of hardening processes. A transient three-dimensional thermal model is combined with a three-dimensional kinetic model for steel phase transformation and solved in order to predict the temperature history and solid phase history of the workpiece while considering latent heat of phase transformation. Further, back-tempering is also added to the model to determine the phase transformation during multitrack laser hardening. The integrated model is designed to accurately predict temperature, phase distributions and hardness inside complex geometric domains. The laser hardening parameters for two industrial workpieces are optimized for two different industrial laser systems using this model. Experimental results confirm the validity of predicted results.Copyright

Numerical Modeling of Transport Phenomena and Dendritic Growth in Laser Conduction Welding of 304 Stainless Steel

A multi-scale model is developed to investigate the heat/mass transport and dendrite growth in laser spot conduction welding. A macro-scale transient model of heat transport and fluid flow is built to study the evolution of temperature and velocity field of the molten pool. The molten pool geometry and other solidification parameters are calculated, and the predicted pool geometry matches well with experimental result. On the micro-scale level, the dendritic growth of 304 stainless steel is simulated by a novel model that has coupled the Cellular Automata (CA) and Phase Field (PF) methods. The epitaxial growth is accurately identified by defining both the grain density and dendrite arm density at the fusion line. By applying the macro-scale thermal history onto the micro-scale calculation domain, the microstructure evolution of the entire molten pool is simulated. The predicted microstructure achieves a good quantitative agreement with the experimental results.Copyright