Analytical and Numerical Model of Laser Welding Phenomena with the Initial Preheating

The paper presents the analysis of stress state in flat elements of welded dual-beam laser. One of them (lower power) is used as a source of preheating, the second (main) as a source of welding. The temperature field is determined using the equation of heat conduction, which comprises a convection term and is solved by the Green function method. Temporary and residual stresses obtained from equilibrium equations solutions by FEM using the law nonisothermal plastic flow with isotropic strengthening and Huber-Misses condition plasticity. In the model was taken into account strain of phase transitions and transformation plasticity. The phase transformation model is based on the continuous cooling transformation diagram plotted for steel welded, as well as on the Avrami, Koistinen and Marburger equations. Thermomechanical parameter changes of material as a function of phase contents and temperature are considered.