Laser-assisted machining has been considered as an alternative for difficult-to-machine materials such as metallic alloys and ceramics. Machining of some materials such as high chromium alloys and high strength steels is still a delicate and challenging task. Conventional machines or computer numerical control (CNC) machines and cutting tools cannot adapt easily to such materials and induce very high costs for operations of rough machining or finishing. If laser-assisted machining can be implemented successfully for such materials, it will offer several advantages over the traditional methods including longer tool life, shorter machining time and reduced overall costs. This thesis presents the results of the research conducted on laser assisted machining of hard to wear materials used in making heavy duty mineral processing equipment for the mining industry. Experimental set up using a high power Nd:YAG laser beam attached to a lathe has been developed to machine these materials using cubic boron nitride (CBN) based cutting tools. The laser beam was positioned so that it was heating a point on the surface of the workpiece directly before it passed under the cutting tool. Cutting forces were measured during laser assisted machining and were compared to those measured during conventional machining. Results from the experiments show that with the right cutting parameters and laser beam position, laser assisted machining results in a reduction in cutting forces compared to conventional machining. A mathematical thermal model was used to predict temperatures within the workpiece at depths under the laser beam spot. The model was used to determine the effect of various cutting and laser parameters on the temperature profile within the workpiece. This study shows that laser assisted machining of hard to wear materials such as high chromium white cast iron shows potential as a possible economical alternative to conventional machining methods. Further research is needed before it can be introduced in industry as an alternative to conventional machining.

Aujourd'hui, les méthodes de corrélation d'images sont largement utilisées pour la caractérisation et le suivi temporel des essais mécaniques. Cependant dans le domaine de l'usinage, ces méthodes sont très peu employées pour l'étude en pointe d'outil de la coupe par manque d'accessibilité, de la faible taille de la zone observée et des fortes déformations dans la zone de coupe. Dans cette thèse, nous mettons en application la technique de corrélation d'images pour l'étude et la caractérisation des champs cinématiques induits dans la matière usinée, durant des essais de coupe conduits avec des conditions opératoires représentatives des opérations industrielles. Ces conditions nous ont permis de développer, en premier lieu, des outils expérimentaux et numériques. Puis, les performances du dispositif expérimental ainsi que les incertitudes de corrélation ont été quantifiées. Différentes stratégies d'exploitation des images ainsi que des outils numériques pour la mesure des caractéristiques de la coupe sont proposés. Ensuite, nous avons développé un outil de corrélation d'images intégrée pour la mesure des efforts dynamiques grâce à un modèle analytique. Pour valider l'ensemble des méthodes, des essais de rabotage, d'abord dans un alliage d'aluminium, puis dans un acier 100~CrMo~7 traité thermiquement, ont été conduits. Ils ont permis de quantifier les champs cinématiques ainsi que les caractéristiques de la coupe. Enfin ces outils ont été appliqués pour la prédiction de l'intégrité de surface engendrée par une géométrie 3D d'outil de coupe dans le matériau dur. / Nowadays, digital image correlation (DIC) methods are widely employed to the mechanical testing characterization and their temporal monitoring. However in the machining field, to study the cutting process at the tool edge, these methods are not commonly applied due to the poor accessibility, the size of the observed area and the large strain occurring herein. In this study, the kinematic fields induced in the material by the cutting process are characterized and analyzed at industrial cutting conditions. In order to take and treat the pictures of the cut, experimental and numerical techniques have been first established. Then, the experimental setup performances and the uncertainties of the DIC were quantified. Different images selection strategies for the DIC and numerical post-processing algorithm for measuring the characteristics of the cut were proposed. Furthermore, a DIC integrated approach based on an analytical model was developed to record dynamics cutting forces. Trials in orthogonal configuration were performed and analyzed to validate the developed procedures first in an aluminium alloy, then in a 100~CrMo~7 hardened steel. The kinematics fields and the macroscopic data of the cut were successfully measured thanks to these tools. Finally, they were used for the prediction of the surface integrity induced by a 3D cutting edge in the hard material.