| Lasers are ideal tools for various material processing. Inherent characteristics of light energy allow an easy control over the delivery and thus provide high-quality results. Due to the recent technological advances, transformation hardening with laser have seen a growing interest. Each part to be heat treated by laser require the development of recipes in order to achieve desired resuIts. Numerical modeling allows to simulate the process with great accuracy, thus reducing the need of experiments. This study focuses on the modeling and simulation of thermal flow resulting from the interaction between laser beam and workpiece. A numerical function is developed to accurately and automatically model a laser beam traversing complex surfaces, such as the gear tooth.;First, a literature review covers the modeling of laser hardening. It reviews the different technics, factors inherent within the process and the state of current knowledge. A particular interest is done over the laser hardening of AISI 4340 steel and on application of the process on small spur gears. Subsequently, the basic principles of the process are exposed as wells as the parameters and mechanisms that are taking place.;After this overview, the study focuses on numerical modeling using finite-element method. Two modeling approaches are established and used to simulate simple situations with COMSOL software. These approaches are numerically validated by reproducing tests found in literature.;The numerical function is developed in MATLAB based on one of these approaches. It is developed to model the passage of the laser on the surface of a 3D component while including deformations of the laser beam and the variations of the absorption coefficient according to the conditions of interaction laser / surface.;The function is validated by a series of experiments using a fiber laser and fiat specimens made of AISI 4340. We observe the dynamics of the absorption coefficient under different operating conditions (power, speed and incidence angle). The tests are validated based on surface temperatures and the dimensions of the hardened zones. The developed models can predict the size of the treatment with a relative error of 2%. These tests are also an opportunity to verify the self-quenching capabilities of AISI 4340 made possible by the inherent characteristics of the laser process. |
