Comparison of three formulations for eddy-current problems in a spiral coil electromagnetic acoustic transducer  

作　　者：石文泽 吴运新 龚海 赵志然 范吉志 谭良辰 

机构地区：[1]State Key Laboratory of High Performance Complex Manufacturing(Central South University),Changsha 410083,China [2]School of Mechanical and Electrical Engineering,Central South University,Changsha 410083,China [3]Nonferrous Metal Oriented Advanced Structural Materials and Manufacturing Cooperative Innovation Center,Changsha 410083,China [4]School of Materials Science and Engineering,Central South University,Changsha 410083,China

出　　处：《Journal of Central South University》2016年第4期817-824,共8页中南大学学报（英文版）

基　　金：Project(2014BAF12B01)supported by the Key Projects in the National Science&Technology Pillar Program during the Twelfth Five-year Plan Period,China;Project(51405520)supported by the National Natural Science Foundation of China;Project(2012CB619505)supported by National Basic Research Program of China

摘　　要：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 {I1 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 Ili 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.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.

关 键 词：electromagnetic acoustic transducer （EMAT） eddy current finite element method （FEM） skin and proximity effects spiral coil 

分 类 号：TB552[理学—物理]