報告題目: Impact model and control of ultrasonic excitation using electrormagnetic acoustic transducer

報告人：Dr. Fumio Kojima（Kobe University）

報告時間：2016年11月24日14:30

報告地點：18-529

主辦單位：國際交流合作處、航空宇航學院、機械結構力學及控制國家重點實驗室、校科協

Dr. Fumio Kojima received the Doctor of Engineering from Kyoto University in 1985. He was a staff scientist at Institute of Computer Applications in Science and Engineering (ICASE), NASA Langley Research Center, Hampton, Virginia during 1986-90. In 1990, he was an assistant professor at Research Center in Applied Mathematics (RIMS) in the University of Southern California. In 1991 he was an associate professor at the Department of Mechanical Engineering, Osaka Institute of Technology and became a professor in 1994. In 1999, he joined Graduate School of Science and Technology, Kobe University. He retired his position at Kobe University this year. He is currently Emeritus Professor of Kobe University, Visiting Professor at Tohoku University, and at Tokyo Metropolitan University. He was also scientific consultant at ICASE during 1990-92 and had visiting positions in North Carolina State University (CRSC), University of Minnesota (IMA), Chinese University of Hong Kong, Xian Jiaotong University, etc. He has been a scientific advisor for the Institute of Applied Mechanics at Vietnamese Academy of Science and Technology since 2005. He has been also an editor of Electrical Journal of Advanced Maintenance (E-JAM) since 2009, a president of the Institute of Systems, Control and Information Engineers (ISCIE) during 2013 to 2014 and a fellow of Japan Society of Mechanical Engineers (JSME) and ISCIE.

This lecture is concerned with a mathematical modeling of ultrasonic excitation signal using electromagnetic acoustic transducer (EMAT). The set of impact models by EMAT are described by a static magnetic problem, a semi-static eddy current problem, and a magnetic-elastic coupling problem. The bias magnetic field by permanent magnets can be described by a nonlinear static magnetic field model. The dynamic magnetic field by electrical coil can be analyzed by a time-dependent linear electro-magnetic model. The magnetic-elastic coupling is generated by interaction between bias and dynamic magnetic fields. Consequently, impact models of ultrasonic test signals are formulated as total effects by Lorentz, magnetization, and magnetostrictive forces. The method presented here is applied to guided wave testing system for detecting corrosion of pipe wall thinning.