Modeling and finite element analysis of transduction process of electromagnetic acoustic transducers for nonferromagnetic metal material testing

Abstract

Facing the problems lack of considering the non-uniform distribution of the static bias magnetic field and computing the particle displacements in the simulation model of electromagnetic acoustic transducer (EMAT), a multi-field coupled model was established and the finite element method (FEM) was presented to calculate the entire transduction process. The multi-field coupled model included the static magnetic field, pulsed eddy current field and mechanical field. The FEM equations of the three fields were derived by Garlerkin FEM method. Thus, the entire transduction process of the EMAT was calculated through sequentially coupling the three fields. The transduction process of a Lamb wave EMAT was calculated according to the present model and method. The results show that, by the present method, it is valid to calculate the particle displacement under the given excitation signal and non-uniformly distributed static magnetic field. Calculation error will be brought about if the non-uniform distribution of the static bias magnetic field is neglected.

Keywords

metal material nondestructive testing / electromagnetic acoustic transducer / multi-field coupling / Garlerkin method / finite element

References

[1] WangX.-h., ZhuC.-m., MaoH.-l., HuangZ.-feng.. Feasibility analysis for monitoring fatigue crack in hydraulic turbine blades using acoustic emission technique [J]. Journal of Central South University, 2009, 16(3): 444-450

[2] HuangS.-l., LiL.-m., ShiK.-r., WangX.-feng.. Magnetic field properties caused by stress concentration [J]. Journal of Central South University, 2004, 11(1): 23-26

[3] MasahikoH., HirotsuguO.EMATS for science and industry non-contacting ultrasonic measurements [M], 2003, Boston, Kluwer Academic Publishers: 1-9

[4] AlersG. A., BurnsL. R.. EMAT designs for special applications [J]. Materials Evaluation, 1987, 45(10): 1184-1189

[5] DixonS., EdwardsC., PalmerS. B.. Experiment to monitor adhesive cure using electromagnetic acoustic transducers [J]. Insight-Non-Destructive Testing and Condition Monitoring, 1995, 37(12): 969-973

[6] MurayamaR., AyahaK.. Evaluation of fatigue specimens using EMATs for nonlinear ultrasonic wave detection [J]. Journal of Nondestructive Evaluation, 2007, 26(2/3/4): 115-122

[7] SedlakP., SikulaJ., LokajicekT., MoriY.. Acoustic and electromagnetic emission as a tool for crack localization [J]. Measurement Science and Technology, 2008, 19(4): 45701

[8] ThompsonR.B.. Noncontact transducers [C]. Ultrasonics Symposium Proceedings, 1977, New York, IEEE: 74-83

[9] LudwigR., YouZ., PalanisamyR.. Numerical simulations of an electromagnetic acoustic transducer-receiver system for NDT applications [J]. IEEE Transactions on Magnetics, 1993, 29: 2081-2089

[10] Jafri-shapoorabadiR., KonradA., SinclairA. N.. Comparison of three formulations for eddy-current and skin effect problems [J]. IEEE Transactions on Magnetics, 2002, 38: 617-620

[11] Jafri-shapoorabadiR., KonradA., SinclairA. N.. Computation of current densities in the receiving mode of electromagnetic acoustic transducers [J]. Journal of Applied Physics, 2005, 97(10): 100-106

[12] KaltenbacherM., FttingerK., LerchR., TittmannB.. Finite element analysis of coupled electromagnetic acoustic systems [J]. IEEE Transactions on Magnetics, 1999, 35: 1610-1613

[13] JianX., DixonS., GrattanK. T., EdwardsR. S.. A model for pulsed Rayleigh wave and optimal EMAT design [J]. Sensors and Actuators: A, Physical, 2006, 128: 296-30

[14] EISLEY J G., Mechanics of elastic structures: Classical and finite element methods [M]. Englewood Cliffs: Prentice Hall, 1989: 55–70.

[15] JinJ. M.The finite element method in electromagnetics [M], 2000, New York, Wiley: 529-536