Reliable calculations of heat and fluid flow during conduction mode laser welding through optimization of uncertain parameters

During conduction mode laser beam welding, the quality of numerical simulation of heat transfer and fluid flow in the weld pool is significantly affected by the uncertainty in the values of absorptivity, effective thermal conductivity, and effective viscosity that cannot be easily prescribed from fundamental, principles. Traditionally, values of these parameters are either prescribed based on experience or adjusted by trial and error. This paper proposes a deterministic approach to improve reliability of heat transfer and fluid flow calculations. The approach involves evaluation of the optimized values of absorptivity, effective thermal conductivity, and effective viscosity during conduction mode laser beam welding from a limited volume of experimental data utilizing an iterative multivariable optimization scheme and a numerical heat transfer and fluid flow model. The optimization technique minimizes the error between the predicted and the measured weld dimensions by considering the sensitivity of weld dimensions with respect to absorptivity, effective thermal conductivity, and effective viscosity. Five sets of measured weld pool dimensions corresponding to five different welding conditions were utilized for the optimization. However, the procedure could identify the optimized values of the three uncertain parameters even with only three sets of measured weld pool dimensions.