Research Information System
Thesis Type: Doctorate
Institution Of The Thesis: Gazi University, Fen Bilimleri Enstitüsü, -, Turkey
Approval Date: 2020
Thesis Language: Turkish
Student: AHMET SUAT YILDIZ
Supervisor: Oğuzhan Yılmaz
Abstract:Additive manufacturing is promising by providing complex design flexibility, less material usage and short lead times. Wire arc additive manufacturing (WAAM) is a variant of additive manufacturing which allows production of large-scale and middle complex parts. In this thesis work, geometrical, mechanical and metallurgical properties of WAAM parts with the thermal behavior effects was studied. Firstly, the effect of the main WAAM parameters wire feed speed (WFS) and the ratio of WFS to travel speed (TS) on bead geometry, microstructure, and mechanical properties was investigated. The results showed that WFS and WFS/TS are the major parameters to control the heat input and bead geometry. A regression model which estimates the bead geometry was developed. With two chosen parameter sets, low and high heat input single-bead walls, and multiple bead walls with parallel and oscillation building strategy were deposited. Tensile and microstructure specimens extracted from the walls showed that the high heat input improves the toughness by 22%, but lowers the yield and tensile strength by 6% and 4% respectively. Vertical and horizontal oriented samples tensile test results showed that the material exhibits isotropic properties with WAAM. In order to investigate the thermal behavior in the material, a model using finite element method was developed and verified with the experiments. This model was further developed to estimate the cooling time between layers. The cooling curves were also used to estimate the microstructure which affects the mechanical properties of the parts by using the continuous cooling transformation diagram