Doctoral thesis information of researcher Mai Tất Lợi (revised version after the Institutional Thesis Evaluation Committee):

Full name of researcher: Mai Tất Lợi

Supervisors: Prof. Dr. Vũ Ngọc Pi and Assoc. Prof. Dr. Lê Thu Quý

Field: Mechanical Engineering - Code: 9520103

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

Thesis title: “Research on external cylindrical surface machining using ultrasonic-assisted electrical discharge machining with graphite electrode”

Summary of new conclusions of the thesis

1. Scientific significance

- The research introduced ultrasonic vibration into the electrical discharge machining process of external cylindrical surfaces on hardened 90CrSi material using a graphite electrode. Thereby, it clarified the influence of vibration on the machining process and determined the optimal vibration and input parameters to enhance machining efficiency.

- The research contributes results to the field of study on ultrasonic-assisted electrical discharge machining (EDM).

2. Practical significance

- Application of ultrasonic vibration to the external cylindrical surface EDM process to improve machining efficiency in the practical manufacturing of compression molding dies.

- The research results can serve as reference material for teaching and research activities in the field of mechanical machining.

- The research findings can be used as a basis for further scientific studies in the field of mechanical machining.

3. New contributions of the thesis

- One of the pioneering studies on ultrasonic-assisted electrical discharge machining (UV-EDM) for external cylindrical surfaces - a characteristic profile that is difficult to machine using conventional EDM due to debris accumulation and arc instability.

- Utilization of a graphite electrode, a material with good electrical conductivity and high formability but prone to wear, making it suitable for evaluating the electrode wear rate (EWR) reduction effectiveness of ultrasonic vibration.

- The research proposed and solved single-objective and multi-objective optimization problems for key output parameters, including material removal rate (MRR), surface roughness (SR), and

electrode wear rate (EWR), contributing to improving the efficiency and quality of the machining process in modern manufacturing.

Based on a solid theoretical foundation, a clear identification of research gaps, and specific practical application orientations, the research promises to make significant contributions to the development of UV-EDM technology under Vietnamese conditions, while opening up new research directions and applications in the field of advanced manufacturing.

Detailed content of the doctoral dissertation by Ph.D. Candidate Mai Tất Lợi, view here