We describe the general features of a numerical model, and of its extentions, for calculating the temperature and velocity field in a three-dimensional workpiece undergoing deep-penetration laser beam welding. In our model the deposition of power from the beam is represented by time-dependent boundary conditions on the equations of energy and momentum transfer. These boundary conditions are specified at each timestep on a moving surface whose shape follows a modified Beer-Lambert’:s law. Our model also includes the effects of the buoyancy force on the melt pool and of the surface tension gradient on the surface of the fluid. Examples of isotherms and convection patterns calculated using our model are presented and their significance for predicting weldment properties is discussed. The coupled equations of energy, momentum transfer and continuity combined with the time dependent boundary conditions representing the keyhole and the moving boundaries of the workpiece are solved by employing a modified SIMPLE algorithm. We briefly discuss the important features of the numerical methods used in our model.

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1992
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