The National Research Institute of Mechanical Engineering plans to organize the Institute-level defense of the Doctoral Thesis for PhD Candidate Ngo Trong Binh in early September 2023. The Institute hereby publishes the information on the Candidate's Doctoral Thesis as follows:

Full name of PhD Candidate: Ngo Trong Binh

Supervisors: Assoc. Prof. Dr. Hoang Tung and Assoc. Prof. Dr. Vu Huy Lan

Major: Mechanical Engineering - Code: 9520103

Training Institution: National Research Institute of Mechanical Engineering - Ministry of Industry and Trade

Thesis title: "Research on the MAG welding process for narrow-gap butt joints"

Training Institution: National Research Institute of Mechanical Engineering - Ministry of Industry and Trade

Summary of new conclusions of the Thesis:

- This is an experimental research work applying narrow-gap butt welding technology (NG-MAG welding) for thick CT.38 carbon steel, with the following new contributions:

+ Proposing an experimental research methodology for the NG-MAG welding process of thick CT.38 steel suitable for practical conditions using the MAG D500 welding power source of the National Research Institute of Mechanical Engineering and the locally available LINCOLN FLEXTEC^® 500x welding equipment. Using the N27 experimental design method with the survey domain of 3 independent factors defining the welding parameters: welding current (I_h, A), welding speed (v_h, m/h), and bevel angle (a, degrees). The quality of the welded joint is evaluated through a set of criteria including: mechanical-physical properties (microhardness, tensile strength) and metallographic characteristics (macrostructure, microstructure in characteristic sub-regions);

+ Applying mathematical statistical data processing methods according to the full factorial orthogonal experimental design of 3 levels and 3 factors (N27) using the least squares method to develop a numerical model predicting the tensile strength (s_k, MPa) of the NG-MAG welded joint in the form of a second-order polynomial. Accordingly, it is easy to select the appropriate NG-MAG welding parameters for CT.38 steel to achieve the required tensile strength for welded structures. At the same time, 2D and 3D graphs were provided to visually represent the influence patterns of NG-MAG welding parameters on s_k within the selected survey domain of the three parameters I_h, v_h, and a.

- The research results of the thesis can be applied in production practice and serve as reference material for training endogenous Science and Technology (S&T) human resources.

For the detailed content of the Doctoral Thesis of PhD Candidate Ngo Trong Binh, please see here