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中南大学学报(英文版)

Journal of Central South University

Vol. 23    No. 4    April 2016

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Comparison of three formulations for eddy-current problems in a spiral coil electromagnetic acoustic transducer
SHI Wen-ze(石文泽)1,2, WU Yun-xin(吴运新)1,2, 3, GONG Hai(龚海)1,2,3,4, ZHAO Zhi-ran(赵志然)1,2, FAN Ji-zhi(范吉志)1, 3, TAN Liang-chen(谭良辰)1,2

1. State Key Laboratory of High Performance Complex Manufacturing(Central South University),
Changsha 410083, China;
2. School of Mechanical and Electrical Engineering, CentralSouthUniversity, Changsha 410083, China;
3. Nonferrous Metal Oriented Advanced Structural Materials and ManufacturingCooperativeInnovationCenter, Changsha 410083, China;
4. School of Materials Science and Engineering, Central South University, Changsha 410083, China

Abstract:Three differential equations based on different definitions of current density are compared. Formulation Ⅰ is based on an incomplete equation for total current density (TCD). Formulations Ⅱ and Ⅲ are based on incomplete and complete equations for source current density (SCD), respectively. Using the weak form of finite element method (FEM), three formulations were applied in a spiral coil electromagnetic acoustic transducer (EMAT) example to solve magnetic vector potential (MVP). The input impedances calculated by Formulation III are in excellent agreement with the experimental measurements. Results show that the errors for Formulations I&II vary with coil diameter, coil spacing, lift-off distance and external excitation frequency, for the existence of eddy-current and skin & proximity effects. And the current distribution across the coil conductor also follows the same trend. It is better to choose Formulation I instead of Formulation III to solve MVP when the coil diameter is less than twice the skin depth for Formulation I is a low cost and high efficiency calculation method.

 

Key words: electromagnetic acoustic transducer (EMAT); eddy current; finite element method (FEM); skin and proximity effects; spiral coil

中南大学学报(自然科学版)
  ISSN 1672-7207
CN 43-1426/N
ZDXZAC
中南大学学报(英文版)
  ISSN 2095-2899
CN 43-1516/TB
JCSTFT
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