• Journal of Biomedical Engineering Research
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• v.7 no.2
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• pp.117-118
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• 1986

It is well known that nonlinear propagation characteristics of the wave in the tissue may give very useful information for the medical diagnoisis. In this paper, a new method to detect nonlinear propagation characteristics of the internal vibration in the tissue for the low frequency mechanical vibration by using bispectral analysis is proposed. In the method, low frequency vibration of f0( = 100Hz) is applied on the surface of the object, and the waveform of the internal vibration x (t) is measured from Doppler frequency modulation of silmultaneously transmitted probing ultrasonic waves. Then, the bispectra of the signal x (t) at the frequencies (f0, f0) and (f0, 2f0) are calculated to estimate the nonlinear propagation characteristics as their magnitude ratio, w here since bispectrum is free from the gaussian additive noise we can get the value with high S/N. Basic experimental system is constructed by using 3.0 MHz probing ultrasonic waves and the several experiments are carried out for some phantoms. Results show the superiority of the proposed method to the conventional method using power spectrum and also its usefulness for the tissue characterization.

• Journal of Biomedical Engineering Research
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• v.16 no.4
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• pp.525-532
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• 1995

In this paper, a new try to measure nonlinear propagation characteristics of the pulse along blood vessel by using bispectral analysis is introduced, and the possibility of its application to the medical diagnosis is shown. In this method, the waveforms of pulse motion of blood vessel at two separated measuring points on the wall were detected from Doppler frequency modulation of transmitted probing ultrasonic waves. Then the auto- and crossbispectrum of detected waveforms are calculated to estimate the quadratic NTF (nonlinear transfer function) between the two measuring positions. In order to show relationships between the NTF and the nonlinear propagation characteristics, computer simulations have been performed. As the propagation distance increases, harmonic frequency components in NTF increases broadly due to the nonlinear effect in the propagation of blood pulse. In order to represent this phenomena quantitatively, we propose a new parameter, dispersion ratio of WTF. Basic experimental system was constructed by using 3.5MHz probing ultrasonic waves and the preliminary experiments were carried out on ague phantom and human body. Experimental results showed the validity of the measurement system enoughly.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.5
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• pp.564-572
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• 2012

Harmonic imaging is introduced in the present article and its principle and physical characteristics is described in contrast to conventional ultrasonic imaging. The principle of the conventional image which uses ultrasonic echoes reflected at the interfaces between tissues is presented, and the nonlinear ultrasonic propagation which results in harmonic components is conceptually described. The pulse inversion technique which effectively extracts the harmonic components from the ultrasonic echo signals is introduced, and the advantages of the constructed harmonic images are summarized comparing with those of conventional ultrasonic images. The harmonic images are classified according to the mechanism of harmonic production, and the typical harmonic images obtained from patients are presented in contrast to the corresponding sonograms. Clinical significance and prospects of harmonic imaging and the future research areas are discussed.

• Journal of Biomedical Engineering Research
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• v.14 no.1
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• pp.31-40
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• 1993

It is well known that nonlinear propagation characteristics of the wave in the tissue may give very useful information for the medical diagnoisis. In this paper, a new method to detect nonlinear propa gation characteristics of the internal vibration in the tissue for the low frequency mechanical vibra lion by using bispectral analysis is proposed. In the method, low frequency vibration of $f_0(=100Hz)$ is applied on the surface of the object, and the waveform of the internal vibration ${\times}{\;}(t)$ is measured from Doppler frequency modulation of silmultaneously transmitted probing ultrasonic waves. Then, the bispectra of the signal ${\times}{\;}(t.)$ at the frequencies ($f_0,{\;}f_0$) and ($f_0,{\;}2f_0$) are calculated to estimate the nonlinear propagation characteristics as their magnitude ratio, where since bispectrum is free from the gallssian additive noise we can get the value with high S/N. Basic experimental system is con structed by using 3.0 MHz probing ultrasonic waves and the several experiments are carried out for some phantoms. Results show the superiority of the proposed method to the conventional method using power spectrum and also its usefulness for the tissue characterization.

• Journal of Biomedical Engineering Research
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• v.16 no.3
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• pp.359-366
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• 1995

The parameter, B/A, quantifies nonlinearity of the pressure-density relationship of propagation medium. This study investigated quantitative evaluation technique for healing fractured bones using this ultrasonic nonlinear parameter, B/A, obtained by the second harmonic amplitude method. A series of fundamental experiments were performed on cylinder phantoms made of aluminium, which demonstrated potential capability of nonlinear parameter B/A in the diagnosis of healing fractured bones using ultrasound.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.2
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• pp.214-219
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• 2001

In this paper, the nonlinear behavior of ultrasonic wave in partially degraded material is considered. For this aim, FDM(finite difference method) model for the nonlinear wave equation was developed with the restriction to the 1-D longitudinal wave motion and how the partial degradation in material contributes to the detected nonlinear parameter was analyzed quantitatively. In order to verify the rightness of this simulation method, the relation between the detected nonlinear parameter and the continuous distribution of degradation obtained from simulation was compared with experiment results and the simulation and experiment results showed similar tendency. It can be known from simulation result that the degree of degradation, the range of degradation and the continuous distribution of degradation have strong correlation with the detected nonlinear parameter. As it was possible in these simulations that only special part is assumed as degraded one, the quantitative evaluation of partially degraded material may be obtained by using this method.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.5
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• pp.458-463
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• 2010

Since the acoustic nonlinearity is sensitive to the minute variation of material properties, the nonlinear ultrasonic technique(NUT) has been considered as a promising method to evaluate the material degradation or fatigue. However, there are certain limitations to apply the conventional NUT using the bulk wave to thin plates. In case of plates, the use of Lamb wave can be considered, however, the propagation characteristics of Lamb wave are completely different with the bulk wave, and thus the separate study for the nonlinearity of Lamb wave is required. For this work, this paper analyzed first the conditions of mode pair suitable for the practical application as well as for the cumulative propagation of quadratic harmonic frequency and summarized the result in for conditions; (1) phase matching, (2) non-zero power flux, (3) group velocity matching, and (4) non-zero out-of-plane displacement. Experimental results in aluminum plates showed that the amplitude of the secondary Lamb wave and nonlinear parameter growed up with increasing propagation distance at the mode pair satisfying the above all conditions and that the ration of nonlinear parameters measured in Al6061-T6 and Al1100-H15 was closed to the ratio of the absolute nonlinear parameters.

• Coupled systems mechanics
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• v.10 no.1
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• pp.39-60
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• 2021

The present paper is concerned with the study of nonlinear ultrasonic waves in a magneto thermo (MT) elastic armchair single-walled carbon nanotube (ASWCNT) resting on polymer matrix. The analytical formulation is developed based on Eringen's nonlocal elasticity theory to account small scale effect. After developing the formal solution of the mathematical model consisting of partial differential equations, the frequency equations have been analyzed numerically by using the nonlinear foundations supported by Winkler-Pasternak model. The solution is obtained by ultrasonic wave dispersion relations. Parametric work is carried out to scrutinize the influence of the non local scaling, magneto-mechanical loadings, foundation parameters, various boundary condition and length on the dimensionless frequency of nanotube. It is noticed that the boundary conditions, nonlocal parameter, and tube geometrical parameters have significant effects on dimensionless frequency of nano tubes. The results presented in this study can provide mechanism for the study and design of the nano devices like component of nano oscillators, micro wave absorbing, nano-electron technology and nano-electro- magneto-mechanical systems (NEMMS) that make use of the wave propagation properties of armchair single-walled carbon nanotubes embedded on polymer matrix.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.3
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• pp.276-282
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• 2013

This paper proposes an ultrasonic method for measurement of linear and hysteretic interfacial stiffness of contacting surfaces between two steel plates subjected to nominal compression pressure. Interfacial stiffness was evaluated by the reflection and transmission coefficients obtained from three consecutive reflection waves from solid-solid surface using the shear wave. A nonlinear hysteretic spring model was proposed and used to define the quantitative interfacial stiffness of interface with the reflection and transmission coefficients. Acoustic model for 1-D wave propagation across interfaces is developed to formulate the reflection and transmission waves and to determine the linear and nonlinear hysteretic interfacial stiffness. Two identical plates are put together to form a contacting surface and pressed by bolt-fastening to measure interfacial stiffness at different states of contact pressure. It is found from experiment that the linear and hysteretic interfacial stiffness are successfully determined by the reflection and transmission coefficient at the contact surfaces through ultrasonic pulse-echo measurement.

• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.2
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• pp.77-83
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• 2006

Ultrasonic nonlinearity has been considered as a solution for the detection of microcracks or interfacial delamination in a layered structure. The distinguished phenomenon in nonlinear ultrasonics is the generation of higher-order harmonic waves during the propagation. Therefore, in order to quantify the nonlinearity, the conventional method measures a parameter defined as the amplitude ratio of a second-order harmonic component and a fundamental frequency component included in the propagated ultrasonic wave signal. However, its application In field inspection is not easy at the present stage because no standard methodology has yet been made to accurately estimate this parameter. Thus, the aim of this paper is to propose an advanced signal processing technique for the precise estimation of a nonlinear ultrasonic parameter, which is based on power spectral and bispectral analysis. The method of estimating power spectrum and bispectrum of the pulse-like ultrasonic wave signal used in the commercial SAM (scanning acoustic microscopy) equipment is especially considered in this study The usefulness of the proposed method Is confirmed by experiments for a Newton ring with a continuous air gap between two glasses and a real semiconductor sample with local delaminations. The results show that the nonlinear parameter obtained tv the proposed method had a good correlation with the delamination.