Doctoral thesis information of PhD candidate Nguyen Van Tung (revised version after the Institute-level Thesis Evaluation Council):

Full name of PhD candidate: Nguyen Van Tung

Supervisory team: Prof. Dr. Vu Ngoc Pi and Dr. Phan Dang Phong

Field: Mechanical Engineering - Code: 9520103

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

Thesis title: "Study on the influence of some technological parameters on the process of external cylindrical surface sinking using graphite electrode with powder-mixed dielectric fluid"

Summary of new conclusions of the thesis

1. Scientific significance:

- The thesis contributes to clarifying the relationship between the main machining parameters of PMEDM including C_p, T_on, T_off, I_p and SV for single-objective problems (surface roughness, material removal rate and electrode wear rate) and multi-objective problems, and at the same time proposes reasonable pulse settings for the process of machining 90CrSi steel using graphite electrode.

-  This study contributes to supplementing a solid theoretical foundation for further research on EDM and PMEDM technology.

2. Practical significance

- The results of the thesis can be directly applied in production to machine complex-shaped parts such as punches and dies using the PMEDM method, improving product quality and predicting values to optimize the machining process in order to minimize production costs.

- In addition, the research results of the thesis can be used as reference material for further research and teaching in the specialized field of EDM and PMEDM machining.

3. New contributions of the thesis

The results of the research can be used for the development of EDM technology and especially the PMEDM method. The outstanding new points of the research include:

- Successfully used the PMEDM process with graphite electrode to machine the external surface of cylindrical shaped parts made of 90CrSi material with dielectric fluid mixed with SiC powder.

- Studied the influence of the main input technological parameters including powder concentration, pulse-on time, pulse-off time, pulse current and pulse voltage on the output parameters of the PMEDM process such as surface roughness, material removal rate and electrode wear rate. In addition, optimal pulse settings for single-objective functions including minimum surface roughness, maximum material removal rate and minimum electrode wear rate have been proposed.

- Solved the multi-objective optimization problem with the above-mentioned single-objective functions using two methods: Taguchi method combined with grey relational analysis and multi-criteria decision-making methods including: TOPSIS, MABAC and EAMR combined with two weight determination methods Entropy and MEREC. Thereby, optimal pulse settings corresponding to each method are proposed. Furthermore, the application scope of the optimization results of each method is also provided.

Detailed information of the thesis of PhD candidate Nguyen Van Tung can be viewed here