The Application Of Numerical Simulation On Laser Strengthening

With the development computer science, finite element method and finite difference method, it is possible to set up a model to describe the physical processes of laser strengthening processes. If some experimental works were carried out to demonstrate the accuracy of modelling and simulation results, then,laser strengthening processes can been accurately simulated by computer; so the virtual laser strengthening processes can been realized based on computer simulation. The relationship between the properties of materials and the technical parameters heat treatment processes can been set up by a large amount of computer numerical simulation works. These numerical simulation results are useful to optimize the technical parameters Laser heat treatment.The theory of multi-physics coupling and finite element method are used to set up a model to describe the physical processes of laser strengthening processes. Then, the temperature field and stress field of these physical processes can been calculated accurately. The quantitative relationship between the laser parameters between laser parameters with the width and depth of harding area is Analyzed. The temperature distribution, the molten pool shapes and fluid flow have been computed,these numerical simulation results can provide the theoretical basis for the practical application of laser strengthening processing.The main work and results of this master dissertation are as follow:The finite element models used for modeling the distribution of temperature field in 45CrMo due to laser strengthening were created by using COMSOL software. The temperature field during laser transformation hardening process and the width and depth of laser transformation hardening zone were calculated. Discussed the sensitivity level of hardened layers effected by laser power and laser scanning speed. The results show that: Effects of changes in laser power on the layer depth is significantly greater than the changes in scanning speed.An axisymmetric numerical model of a laser-induced molten pool has been developed for a laser interaction with Al plate. Based on mixture continuity equations, the coupled PDE of a laminar fluid flow and heat transfer is solved by the finite element method, taking into account the coupled effects of buoyancy, Marangoni forces and the thermophysical characteristics with temperature variations. The temperature distribution, the molten pool shapes and fluid flow have been computed for three calculation cases: (?)γ/(?)T<0,(?)γ/(?)T>0,(?)γ/(?)T=0, corresponding to three different surface tension gradients. The numerical results showed that fluid flow has a significant effect on the shape of the molten pool and can not be ignored during laser processing.