Numerical Simulation Of Temperature Field In Laser Melting Process

With the increasing request of ability of resisting abrasivity, causticity, oxidation and fatigue in material surface, material surface hardening and remodel have been one of important subject in related domains, especially, laser melting employed. Laser melting is a crossed problem involving mechanics,thermodynamics, solidification, heat transfer as well as material. To optimize material parameter and design independently, it is necessary to research the theory of laser melting process further and set up a reasonable numerical model. Thus Application software is programmed using space elastic-plastic finite element method. With numerical simulation, the relationship of technical parameters and processed performance feature is set up, to show thermal physical specialty in laser melting process. The numerical model is set up on the basis of the action and mechanization generated by laser and material in laser melting process. Thus diversified courses are described due to laser radiation, including convection and material structure change. It is complicated to set up a relationship of laser parameters,material parameters and the processed result. We increase the cognition of the mechanization of the laser melting process with the expansion of the application of material laser process. The research of advanced surface character-change and shape-change by means of laser is becoming a corporate aim for those engaged in background research and engineering. The laser melting hardening is a process, during which parts of material surface are heated and melted, then rapidly solidified due to heat transfer of cold mental matrix. Cast nonequilibrium structure is formed in processed surface, which is possessed with high rigidity, and resisting abrasivity and causticity.Researchs indicate laser heat source can be supposed to be a surface heat source with a certain shape and thin energy distribution. To obtain higher precision, model is usually supposed to be one with a body heat source in practical numerical simulation, which is determined by laser characteristic. Light energy is changed into heat energy in free electron model surface. However the energy transmission in the depth of body is followed by heat transfer law. But in practical laser melting process, laser energy is partially used to heat matrix. The percentage of the energy is called material absorptivity; Material absorptivity to laser is related to material characteristic and changed according as material temperature and surface roughness. When laser intensity achieve a certain value or pass it, mental surface will melt and keep liquid. As the processed time going on, due to heat diffusion, the interface between solid and liquid will expand to the depth and width of solid matrix. After process, overheat of liquid leads to further expansion of the interface between solid and liquid, then to reverse direction, till liquid disappears and material solidifies completely. In nature, laser melting process of mental material is one with solid phase transformation and phase transformation between liquid and solid. The materials at each side of interface between solid and liquid are possessed with different thermal physical parameters (heat transfer rate, heat diffusion rate, specific heat and density etc). In laser melting process, the interface between solid and liquid is moving as time. The release and absorption of heat on interface is closely related with temperature variation, so it is necessary to consider latent heat due to phase transformation between solid and liquid. Moreover thermal physical parameter alters a lot in high temperature, chiefly related with temperature.At president, existing commercial application software is not fit for this project, and without other application program either; the researchers of related literatures did not issue their program. Based on these things, it is necessary to programme a set of effective analytical software using space elastic-plastic finite element method and corresponding numerical al...