National Institute for Materials Science, Japan

Biography: Dr. Dongfeng He, now is a senior researcher of National Institute for Materials Science in Japan. He got his B Sc in applied physics, M Sc in condensed matter of physics, Ph.D. in superconducting electronics at Peking University. Once worked at Julich Research Center in Germany as a visiting researcher, and now at National Also Institute for Materials Science in Japan as a Senior researcher. He is also visiting Professor of Chinese Academy of Engineering Physics and Beijing University of Technology. Before 2008, his research interests are on SQUID (superconducting quantum interference device) and its applications. Currently Dr. Dongfeng He’s researches focus at high sensitive magnetic sensors, nondestructive evaluations of combustion chamber of rocket, steel rebar corrosion in concrete, CFRP material, and 3D-printed products.

Speech Title: Evaluation of Steel Reinforcing Bar in Concrete Using Electromagnetic Method
Abstract: Corrosion of steel reinforcing bars in concrete reduces the strength capacity of the structures, and also causes the corrosion cracking in the concrete. Detection of the corrosion of steel reinforcing bar in concrete at its early stage is important for the safety evaluation of the concrete structures. We developed an electromagnetic system to evaluate the steel reinforcing bar in concrete non-destructively. Using AC magnetic induction method with the diameter of the excitation coil of 70 mm and a low noise inductive detection coil, the covering depth and the diameter of steel reinforcing bar in concrete were successfully detected. By optimizing the system, the diameter measurement resolution of steel reinforcing bar is about 1 mm, and the depth measurement resolution is about 0.5 mm at the depth of 50 mm in laboratory tests. Some field experiments were also done to evaluate the steel rebar in the bridges of Japan railway.