Mechanical & Materials Engineering, Department of


Date of this Version

Winter 12-4-2015


A DISSERTATION Presented to the Faculty of The Graduate College at University of Nebraska In Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy, Major: Mechanical Engineering and Applied Mechanics, Under the Supervision of Professor Kamlakar P. Rajurkar. Lincoln, Nebraska: November, 2015

Copyright (c) 2015 Bai Shao


Micro parts and systems are playing crucial roles in the area of semiconductor, biomedical device, micro fluid devices, automotive, aerospace and so forth. Micro manufacturing is one of the most important technologies in realizing miniaturization. Compared to other micro manufacturing methods, micro-EDM is drawing lots of attention due to its ability to machine complex 3D parts regardless of the hardness of the workpiece material.

Micro-EDM is the cumulative result of numerous single discharges; therefore, it is crucial to understand the single discharge material removal process in micro-EDM. However, due to the stochastic nature and complex process mechanism, micro-EDM, including its material removal mechanism, has not been fully understood. Process modeling is an effective way to learn and predict the process.

This thesis is focused on the modeling and simulation of the single discharge micro-EDM. Firstly, a method based on analytical solution of the heat transfer equation to determine the energy distribution ratio is presented. Energy distribution ratio is a decisive parameter in micro-EDM process, which determines the energy input into the electrode. This method uses experimentally measured crater geometries to calculate the energy distribution ratio, which is accurate and easy to apply. Secondly, along with the calculated energy distribution ratio and other realistic boundary conditions, a comprehensive thermal model has been studied. The study shows that the simulation results are very close to the experimental measurements after considering the plasma flushing efficiency. Finally, thermal Marangoni effect has been incorporated into the micro-EDM thermal model. Heat transfer and laminar flow have been studied simultaneously. This model is able to simulate the crater formation process. The simulation results prove that Marangoni effect plays an important role in micro-EDM.

Advisor: Kamlakar P. Rajurkar