Coupled simulation of thermal-metallurgical-mechanical behavior in laser keyhole welding of AH36 steel

A computational fluid dynamics (CFD) simulation of the molten pool in laser keyhole welding was utilized to acquire temperature data for further metallurgical and mechanical calculations. For the CFD simulation, the governing equations were solved, and the scattering and absorption of the laser beam in the plume were modeled at both the standard atmospheric condition (101,325 Pa) and a vacuum condition (3,000 Pa). A stochastic ray-tracing algorithm was adopted to effectively implement the transmission and scattering of laser bundles of rays. The temperature data from the CFD simulation were then imported to a finite element method (FEM)-based heat conduction analysis to simulate the thermal-metallurgical-mechanical behavior during the cooling phase of the weldment. The strain, residual stress, and distortion were calculated using an elastoplastic model based on the phase transformation-dependent material properties. An element deactivation scheme was used to take care of the zero-strength condition of the elements in the molten pool and keyhole region. The Vickers hardness and the residual stress were measured to verify the simulation model, and the experimental and simulation results had a similar tendency.