Biçim bozulmalarının modellenmesi ve havacılık malzemelerinin işlenmesi

Milling process is used in the machining of advanced engineering materials such as Gamma Titanium Aluminide, Titanium and Aluminum Alloys. These materials have various aerospace applications, such as 48-2-2 Gamma Titanium Aluminide and Ti-6Al-4V due to their superior thermo-mechanical properties are used in the aircraft engines and rockets. Whereas, Al7050 is mainly utilized in aircraft structural parts. The aircraft parts are consisting of thin-wall structures and often suffer a deformation which causes a dimensional surface error due to the action of the mechanical and thermal loads generated during the milling process. Therefore, the deformation of thin-walled structural parts is the major problem in aerospace industries. This problem may lead to low productivity, part rejection and high production cost. To avoid part rejection and achieve better machining results it becomes necessary to predict the distortion of the part before going into actual machining. In this thesis, a 3D transient finite element based model is developed to predict the distortion of the Al7050 thin-wall complex structural parts due to the milling process. The combined effect of mechanical and thermal load is considered in the model. These loads are analytically estimated and used as an input for the FEM simulation. A new approach is proposed for applying the mechanical and thermal loads on the final part geometry. Milling experiments in 5-axis CNC machining center are performed in order to validate the simulation results. The results are validated using force measurements, temperature measurements, laser measurements, and coordinate machine measurements. Besides the distortion modeling, machining tests on Gamma Titanium Aluminide (γ- TiAl) and Ti6Al4V Alloys are performed. The novelty of the study lies in reporting the orthogonal database of 48-2-2 γ-TiAl. The developed database is used to predict the cutting forces for milling process for Ti-48Al-2Cr-2Nb (48-2-2) γ-TiAl by employing orthogonal to oblique transformation technique. High-performance coatings have become a successful standard for increasing the efficiency of machining tools in industry over the last decade. The study focuses on establishing an orthogonal cutting database for different tool coatings; AlTiN and AlCrN coatings. The effect of coating on friction coefficient, shear stress, shear angle and cutting forces are investigated. Friction coefficient identified from the orthogonal turning shows that the AlCrN coating has the highest friction coefficient as compared to the AlTiN coating whereas the AlCrN coating has a smaller shear angle as compared to the AlTiN coating. Predicted cutting forces are validated with the experimental cutting forces during end milling and ball-end milling operations for different cutting conditions. The simulated results showed good agreement with the experimental results. Overall, this study provides an important guide for machining of 48 2-2 γ-TiAl alloys and facilitating the transition from processing traditional materials to advanced materials for manufacturing industries.