報 告 人：Wei Hong教授（Iowa State University）
報告題目：A PHASE-FIELD MODEL FOR DIELECTRIC BREAKDOWN
報告時間：2014年5月29日（周四）下午4:00-5:00
報告地點：浙江大學玉泉校區(qū)教十二-118
Abstract
Using an analogy between electrical breakdown and mechanical fracture, this research develops a phase-field model for the electric damage initiation and propagation in dielectric solids during breakdown. Instead of explicitly tracing the growth of a conductive channel, the model introduces a continuous phase field to characterize the degree of damage, and the conductive channel is represented by a localized region of fully damaged material. Similar as in the classic theory of fracture mechanics, an energetic criterion is taken: the conductive channel will grow only if the electrostatic energy released per unit length of the channel is greater than that dissipated through damage. Such an approach circumvents the detailed analysis on the complex microscopic processes near the tip of a conductive channel, and provides a means of quantitatively predicting breakdown phenomena in materials, composites, and devices. This model is implemented into a finite-element code and several numerical examples are solved. With randomly distributed defects, the model recovers the inverse power relation between breakdown strength and sample thickness. Through a numerical study the effect of the layered structure in a breakdown-resistant laminate is demonstrated. Unlike its mechanical counterpart, particle reinforced composite does not effectively enhance the breakdown-resistance properties. In the case of a very compliant substrate, the breakdown strength is even lower due to electro-mechanical coupling.
Biography
Wei Hong is currently an Associate Professor of Aerospace Engineering at Iowa State University. He received his Ph.D. degree in Engineering Sciences from Harvard University in 2006, and both his M.E. and B.E. degrees in Engineering Mechanics from Tsinghua University, in 2002 and 2000 respectively. Between 2006 and 2008, Wei was a Postdoctoral Research Fellow in the School of Engineering and Applied Sciences at Harvard University. Since 2008, Wei has been working as a faculty member in the Department of Aerospace Engineering at Iowa State University, where he also holds curtsey appointments from the departments of Materials Science and Engineering and Mechanical Engineering. His research mainly focuses on solid mechanics and its application in soft active materials, functional ceramics, fracture and damage, solid-state electrochemical reactions, and dielectric failure of solids.
