Improved Dynamic Magnetostriction measurement method based on M-EMAT for the characterization of residual strain

Abstract

The Dynamic Magnetostriction (DM) measurement method as a nondestructive testing method of ferromagnetic materials, measures the DM curve using electromagnetic acoustic transducer (EMAT) to characterize material and predict the mechanical properties. Lorentz forces and magnetostriction forces contribute mainly to the ultrasonic generation. Only the range of low field, in which the magnetostriction force mechanism is predominant can be used to measure the DM curve, but the boundaries of this range are uncertain. The improved DM measurement method based on shear wave Magnetostriction EMAT (M-EMAT) is proposed and the theory of generation of shear waves is derived. For the M-EMAT, only magnetostriction force mechanism contributed to the generation of shear waves. A theoretical model for the optimization of the transducer is developed, the model is in good agreement with the experimental results. The microstructure changes caused by residual strain will affect the magnetostriction coefficient and the DM curve. Therefore, the DM curves of low carbon steel specimens with different levels of residual strains are measured by the optimized transducer to characterize the residual strain. The normalized results demonstrate that the slope of the DM curve obviously changes with the residual strain. This leads to the conclusion that the DM measurement method can be used to characterize the residual strain of the low carbon steels.

Keywords

Dynamic Magnetostriction EMAT shear wave optimization residual strain

Get full access to this article

View all access options for this article.

References

Dobmann

Kröning

Theiner

, Nondestructive characterization of materials (ultrasonic and micro-magnetic techniques) for strength and toughness prediction and the detection of early creep damage, Nuclear Engineering and Design157 (1995), 137–158.

Igarashi

Alers

G.A.

and Purtscher

P.T.

, Magnetostrictive EMAT efficiency as a materials characterization tool, in: Review of Progress in Quantitative Nondestructive Evaluation, Springer, Boston, 1998, pp. 1485–1492.

Wolter

Dobmann

and Fraunhofer

, Micromagnetic testing for rolled steel, European Conference on Nondestructive Testing9 (2006).

Altpeter

Dobmann

Hübschen

, Nondestructive characterization of neutron induced embrittlement in nuclear pressure vessel steel microstructure by using electromagnetic testing, Studies in Applied Electromagnetics and Mechanics35 (2011), 322.

Ren

and Zhou

, Fast measurement of magnetostriction coefficients for silicon steel strips using magnetostriction-based EMAT, Sensors18 (2018), 4495.

Hirao

and Ogi

, Electromagnetic Acoustic Transducers: Noncontacting Ultrasonic Measurements Using EMATs, Springer Japan, 2017, pp. 15–65.

Igarashi

and Alers

G.A.

, Excitation of bulk shear waves in steel by magnetostrictive coupling, IEEE Ultrasonics Symposium. Proceedings (1998), 893–896.

Makar

J.M.

and Tanner

B.K.

, The effect of plastic deformation and residual stress on the permeability and magnetostriction of steels, Journal of Magnetism and Magnetic Materials222(3) (2000), 291–304.

Xie

Tian

, A hybrid nondestructive testing method of pulsed eddy current testing and electromagnetic acoustic transducer techniques for simultaneous surface and volumetric defects inspection, NDT & E International86 (2017), 153–163.