<title>Ultrasonic field modeling for arbitrary non-contact transducer source</title>

Abstract

We present a model for transient ultrasonic wave generation by Electromagnetic Acoustical Transducers (EMATs). Analytical solutions are currently available only for few kinds of sources and our model combines these analytical solutions and numerical computation to predict the ultrasonic field generated by arbitrary sources. This model can be used to calculate bulk waves within samples as well as surface waves on sample surfaces with the advantages of explicit physical meaning and quick processing speed over pure numerical calculations such as the Finite Element Method (FEM). We use the model to explain how static and dynamic magnetic fields generate ultrasonic waves in a sample. We wish to characterize the EMAT source in detail in order to tailor sources for optimal configuration for specific NDE applications. A Michelson laser interferometer is used to measure out of plane surface displacement of sample, and results agree well with the modelling simulation. The modelling can be used for arbitrary source.

3-D modeling and analysis of meander-line-coil surface wave EMATs

“…Using FEM, the distribution of eddy current, magnetic field and Lorentz force of EMATs can be acquired [6][7][8][9][10][11][12]14,15].…”

“…Comparing with the spiral-coil EMATs, the meander-line-coil EMATs possess higher directivity, and they are more widely used in real applications for surface layer detection. Although the modeling method proposed in [14,15] is suitable for spiral-coil EMATs whose sound source can be decomposed into several piston forces, this method is hard to be applied to the meander-line-coil EMATs whose sound source possesses many distinct features. Consequently, this paper proposes a novel 3-D modeling method for the meander-line-coil EMATs and analyzes characteristics of the transducers based on the established model.…”

“…Such simplification inevitably leads to inaccuracy of the models. Subsequently, based on [13], Jian built new models for spiral-coil surface wave EMATs with special attention of the influence of dynamic magnetic field [14,15], and found that Lorentz force due to the dynamic magnetic field played a more significant role in transmitting surface waves than that due to the static one when the excitation current is about 300 A [15].…”

“…To enhance the performance of EMATs, researchers have developed many EMAT models [2,[6][7][8][9][10][11][12][13][14][15]. These models have not only deepened the understanding of working principles of EMATs, but also established a solid foundation for the improvement of their performance.…”

Coil parameter analysis of meander-line coil electromagnetic acoustic transducer-based Rayleigh waves

“…In Dewhurst's study (2003, 2005), EMATs are designed as detectors of ultrasound because of their better detection performance than generation. Several theoretical models have been developed and experimental work done to study the coupling mechanism of EMATs (Jian et al, 2005a(Jian et al, , 2006bKawashima, 1985;Ludwig, 1992;Shapoorabadi et al, 2001Shapoorabadi et al, , 2005Thompson, 1973;Wang et al, 2012). Some work has been published on optimizing the design of EMATs for Rayleigh wave generation (Jian et al, 2005a(Jian et al, , 2006bWang et al, 2012).…”