This paper investigates shear horizontal （SH） waves propagating in a periodically layered structure that consists of piezoelectric （PE） layers perfectly bonded with piezomagnetic （PM） layers alternately. The exp...This paper investigates shear horizontal （SH） waves propagating in a periodically layered structure that consists of piezoelectric （PE） layers perfectly bonded with piezomagnetic （PM） layers alternately. The explicit dispersion relations are derived for the two cases when the propagation directions of SH waves are normal to the interface and parallel to the interface, respectively. The asymptotic expressions for dispersion relations are also given when the wave number is extremely small. Numerical results for stop band effect and phase velocity are presented for a periodic system of alternating BaTiO3 and Terfenol-D layers. The influence of volume fraction on stop band effect and dispersion behaviors is discussed and revealed.展开更多
The fundamental shear horizontal（SH0） wave has several unique features that are attractive for long-range nondestructive testing（NDT）. By a careful design of the geometric configuration, electromagnetic acoustic t...The fundamental shear horizontal（SH0） wave has several unique features that are attractive for long-range nondestructive testing（NDT）. By a careful design of the geometric configuration, electromagnetic acoustic transducers（EMATs） have the capability to generate a wide range of guided wave modes, such as Lamb waves and shear-horizontal（SH） waves in plates. However, the performance of EMATs is influenced by their parameters. To evaluate the performance of periodic permanent magnet（PPM） EMATs, a distributed-line-source model is developed to calculate the angular acoustic field cross-section in the far-field. Numerical analysis is conducted to investigate the performance of such EMATs with different geometric parameters, such as period and number of magnet arrays, and inner and outer coil widths. Such parameters have a great influence on the directivity of the generated SH0 waves that arises mainly in the amplitude and width of both main and side lobes. According to the numerical analysis, these parameters are optimized to obtain better directivity. Optimized PPM EMATs are designed and used for NDT of strip plates. Experimental results show that the lateral boundary of the strip plate has no perceivable influence on SHO-wave propagation, thus validating their used in NDT. The proposed model predicts the radiation pattern ofPPM EMATs, and can be used for their parameter optimization.展开更多
The scattering of shear horizontal(SH)waves by a circular hole in an infinite piezomagnetic medium affected by magnetic field and compressive stress has been investigated theoretically in this study.The effective elas...The scattering of shear horizontal(SH)waves by a circular hole in an infinite piezomagnetic medium affected by magnetic field and compressive stress has been investigated theoretically in this study.The effective elastic,piezomagnetic,and magnetic permeability constants of the piezomagnetic material change with the external magnetic field and compressive stress.The governing differential equations for SH waves scattered by a circular hole are solved using the wave function expansion method.The effects of the magnetic field and compressive stress on mechanical displacement,dynamic stress,and magnetic potential of SH waves around a circular hole are discussed in detail.It has been found that the mechanical displacement around the circular hole increases with magnetic field and decreases with compressive stress.As the magnetic field increases,the maximum dynamic stress increases and structural resonance is strengthened.The findings presented in this study are beneficial for improving the performance of magnetoelastic acoustic wave devices.展开更多
Surface irregularities,such as hills and ridges,can significantly amplify ground motion caused by earthquakes.Therefore,in this study,we propose an analytical solution model to investigate the interaction between an a...Surface irregularities,such as hills and ridges,can significantly amplify ground motion caused by earthquakes.Therefore,in this study,we propose an analytical solution model to investigate the interaction between an asymmetric triangular hill on Earth and SH waves.Firstly,based on the development of wave functions and regional matching techniques,we introduce a semi-circular artificial auxiliary boundary,dividing the solution model into a semi-infinite body containing a semi-circular depression and an asymmetric fan-shaped region.Secondly,we derive the domain function form applicable to solving asymmetric problems.Utilizing the theory of complex variables,we establish a well-posed matrix for solving domain functions within the same coordinate system.Numerical results demonstrate that the scattering of SH waves by a protuberance is jointly influenced by the geometric parameters of the hill and the angle of incidence.Additionally,the frequency of the incident wave also has a certain degree of impact on the displacement amplitude.This study elucidates the scattering mechanism of SH waves by complex boundaries,providing a theoretical reference for building site selection and seismic design.In practical problems,the asymmetric assumption is more applicable than the symmetry assumption.展开更多
We study shear-horizontal （SH） waves in a rotated Y-cut quartz plate carrying an isotropic elastic layer of finite thickness.The three-dimensional theories of anisotropic elasticity and isotropic elasticity are used...We study shear-horizontal （SH） waves in a rotated Y-cut quartz plate carrying an isotropic elastic layer of finite thickness.The three-dimensional theories of anisotropic elasticity and isotropic elasticity are used for the quartz plate and the elastic layer,respectively.A transcen-dental frequency equation that determines the dispersion relations of the waves is obtained.The dispersion relations are obtained and plotted by solving the frequency equation using MATLAB.Approximate dispersion relations are also obtained analytically for two special cases.One is for long waves whose wavelength is much larger than the plate thickness.The other is for the case of a very thin elastic layer.The effects of the elastic layer on the dispersion relations are exam-ined.The results obtained are fundamental and useful to acoustic wave sensors for measuring the mechanical and geometric properties of the elastic layer.展开更多
We investigate the three-dimensional （3D） scattering problem of an incident plane shear horizontal wave by a partly through-thickness hole in an isotropic plate, in which the Lamb wave modes are also included due to...We investigate the three-dimensional （3D） scattering problem of an incident plane shear horizontal wave by a partly through-thickness hole in an isotropic plate, in which the Lamb wave modes are also included due to the mode conversions by the scattering obstacle in the 3D problem. An analytical model is presented such that the wave fields are expanded in all of propagating and evanescent SH modes and Lamb modes, and the scattered far-fields of three fundamental guided wave modes are analyzed numerically for different sizes of the holes and frequencies. The numerical results are verified by comparing with those obtained by using the approximate Poisson/Mindlin plate model for small hole radius and low frequency. It is also found that the scattering patterns are different from those of the SO wave incidence. Our work is useful for quantitative evaluation of the plate-like structure by ultrasonic guided waves.展开更多
For the inspection of large plate-like structures,the omni-directional guided wave transducer-based system has been regarded as an effective tool since only a few transducers are required to cover the entire inspectio...For the inspection of large plate-like structures,the omni-directional guided wave transducer-based system has been regarded as an effective tool since only a few transducers are required to cover the entire inspection area without blind zones.In comparison with Lamb waves,the shear horizontal(SH)wave is more promising because its fundamental mode is non-dispersive.In this work,we proposed an omni-directional SH wave piezoelec trie t ransducer(OSH-PT)based on a radially poled d24-mode PZT ring.Eoth the finite element simulations and experiments were carried out to demonstrate its performance in generating and receiving SH°wave.Results showed that the radially poled OSH-PT could generate single-mode SHo wave and receive SHo wave only over a wide frequency range from 70 to 200 kHz.The obtained signal-to-noise ratio can reach up to 26 dB in generation and 24 dB in reception.The omni-directivity of this OSH-PT is also very good with the deviation only about 6%in both generation and reception of SHo wave.Considering its easy fabrication,low cost and superior performances,this proposed OSH-PT may promote the applications of SHo wave-based inspection in structural health monitoring and nondestructive testing.展开更多
The propagation of shear-horizontal(SH)waves in the periodic layered nanocomposite is investigated by using both the nonlocal integral model and the nonlocal differential model with the interface effect.Based on the t...The propagation of shear-horizontal(SH)waves in the periodic layered nanocomposite is investigated by using both the nonlocal integral model and the nonlocal differential model with the interface effect.Based on the transfer matrix method and the Bloch theory,the band structures for SH waves with both vertical and oblique incidences to the structure are obtained.It is found that by choosing appropriate interface parameters,the dispersion curves predicted by the nonlocal differential model with the interface effect can be tuned to be the same as those based on the nonlocal integral model.Thus,by propagating the SH waves vertically and obliquely to the periodic layered nanostructure,we could invert,respectively,the interface mass density and the interface shear modulus,by matching the dispersion curves.Examples are further shown on how to determine the interface mass density and the interface shear modulus in theory.展开更多
Based on the Boussinesq assumption, derived are couple equations of free surface elevation and horizontal velocities for horizontal irrotational flow, and analytical expressions of the corresponding pressure and verti...Based on the Boussinesq assumption, derived are couple equations of free surface elevation and horizontal velocities for horizontal irrotational flow, and analytical expressions of the corresponding pressure and vertical velocity. After the free surface elevation and horizontal velocity at a certain depth are obtained by numerical method, the pressure and vertical velocity distributions can be obtained by simple calculation. The dispersion at different depths is the same at the O (epsilon) approximation. The wave amplitude will decrease with increasing time due to viscosity, but it will increase due to the matching of viscosity and the bed slope, thus, flow is unstable. Numerical or analytical results show that the wave amplitude, velocity and length will increase as the current increases along the wave direction. but the amplitude will increase, and the wave velocity and length will decrease as the water depth decreases.展开更多
This theoretical study reports results on acoustic wave propagation along the interface of two half-spaces representing cubic crystals of both piezoelectric classes ?43m and 23 with strong piezoelectric effect. In sim...This theoretical study reports results on acoustic wave propagation along the interface of two half-spaces representing cubic crystals of both piezoelectric classes ?43m and 23 with strong piezoelectric effect. In similar configurations, the interfacial Maerfeld-Tournois waves can propagate along the interface of two transversely-isotropic materials of class 6 mm, in which the shear-horizontal surface acoustic waves (SH-SAWs) called the Bleustein-Gulyaev (BG) waves can also exist. Cubic piezoelectrics cannot support existence of the surface BG-waves, according to the recent report by Gulyaev and Hickernell. Hence, new interfacial SH-waves are studied in this paper concerning unique direction [101] of wave propagation in cubic crystals using different electrical boundary conditions (EBCs) of both metallized and non-metallized interfaces. The new interfacial SH-waves can always propagate along the interface of two identical piezoelectric crystals with opposite polarization. In this case, the calculated velocities for both EBCs coincide with the velocity of the ultrasonic surface Zakharenko wave (USZW) propagating in direction [101] on the metallized surface of a cubic piezoelectrics. It was also found that the new interfacial SH-waves can exist when wave propagation is along the interface of two dissimilar half-spaces, for instance, the piezoelectric cubic crystals Bi12SiO20 and Bi12GeO20. Several calculations are also carried out as examples. PACS: 51.40.+p, 62.65.+k, 68.35.Gy, 68.35.Iv, 68.60.Bs, 74.25.Ld.展开更多
The dynamic stress intensity factor (DSIF) and the scattering of SH wave by circle canyon and crack are studied with Green's function. In order to solve the problem, a suitable Green's function is constructed...The dynamic stress intensity factor (DSIF) and the scattering of SH wave by circle canyon and crack are studied with Green's function. In order to solve the problem, a suitable Green's function is constructed first, which is the solution of displacement fields for elastic half space with circle canyon under output plane harmonic line loading at horizontal surface. Then the integral equation for determining the unknown forces in the problem can be changed into the algebraic one and solved numerically so that crack DSIF can be determined. Last when the medium parameters are altered, the influence on the crack DSIF is discussed partially with the displacement between circle canyon and crack.展开更多
A closed-form analytic solution of two-dimensional scattering and diffraction of plane SH waves by a semi- cylindrical hill with a semi-cylindrical concentric tunnel inside an elastic half-space is presented using the...A closed-form analytic solution of two-dimensional scattering and diffraction of plane SH waves by a semi- cylindrical hill with a semi-cylindrical concentric tunnel inside an elastic half-space is presented using the cylindrical wave functions expansion method.The solution is reduced to solving a set of infinite linear algebraic equations.Fourier expansion theorem with the form of complex exponential function and cosine function is used.Numerical solutions are obtained by truncation of the infinite equations.The accuracy of the presented numerical results is carefully verified.展开更多
This paper presents a closed-form solution for diffraction of plane SH waves by a semi-circular cavity in half-space by using wave function expansion method. Accuracy of the solution is checked by the displacement res...This paper presents a closed-form solution for diffraction of plane SH waves by a semi-circular cavity in half-space by using wave function expansion method. Accuracy of the solution is checked by the displacement residual and stress residual along the boundaries. Numerical results show that there are notable differences for response amplitudes between a semi-circular cavity and a whole-circular cavity in a half-space.展开更多
Diffraction of a two-dimensional （2D） semi-circular cavity in a half-space under incident SH-waves is studied using the classic wave function expansion method with a new de-coupling technique. This so-called ＂impro...Diffraction of a two-dimensional （2D） semi-circular cavity in a half-space under incident SH-waves is studied using the classic wave function expansion method with a new de-coupling technique. This so-called ＂improved cosine half- range expansion＂ algorithm exhibits an excellent performance in reducing displacement residual errors at two rim points of concern. The governing equations are developed in a manner that minimizes the residues of the boundary conditions. Detailed derivation and analysis procedures as well as truncation of infinite linear governing equations are presented. The semi-circular cavity model presented in this paper, due to its simple profile, is expected to be used in seismic wave propagation studies as a benchmark for examining the accuracies of various analytical or numerical methods for mixed-boundary wave propagation problems.展开更多
The evaporation duct which forms above the ocean surface has a significant influence on electromagnetic wave propagation above 2 GHz over the ocean. The effects of horizontal inhomogeneity of evaporation duct on elect...The evaporation duct which forms above the ocean surface has a significant influence on electromagnetic wave propagation above 2 GHz over the ocean. The effects of horizontal inhomogeneity of evaporation duct on electromagnetic wave propagation are investigated, both in numerical simulation and experimental observation methods, in this paper. Firstly, the features of the horizontal inhomogeneity of the evaporation duct are discussed. Then, two typical inhomogeneous cases are simulated and compared with the homogeneous case. The result shows that path loss is significantly higher than that in the homogeneous case when the evaporation duct height （EDH） at the receiver is lower than that at the transmitter. It is also concluded that the horizontal inhomogeneity of the evaporation duct has a significant influence when the EDH is low or when the electromagnetic wave frequency is lower than 13 GHz. Finally, experimental data collected on a 149-km long propagation path in the South China Sea in 2013 are used to verify the conclusion. The experimental results are consis- tent with the simulation results. The horizontal inhomogeneity of evaporation duct should be considered when modeling electromagnetic wave propagation over the ocean.展开更多
A closed-form analytical solution of surface motion of a semi-elliptical cylindrical hill for incident plane SH waves is presented. Although some previous analytical work had already dealt with hill topography of semi...A closed-form analytical solution of surface motion of a semi-elliptical cylindrical hill for incident plane SH waves is presented. Although some previous analytical work had already dealt with hill topography of semi-circular and shallow circular, our work aims at calculating surface motion of very prolate hill for high incident frequency, and explaining the special vibrating is checked by boundary conditions, numerical results for and some conclusions are obtained. properties of very prolate hill. Accuracy of the solution surface motion of oblate and prolate hills are calculated,展开更多
Uplift pressures of waves acting on horizontal plates are the important basis for design of maritime hollow-trussed structures. In this paper, an experimental study on the uplift pressures of waves on a horizontal pla...Uplift pressures of waves acting on horizontal plates are the important basis for design of maritime hollow-trussed structures. In this paper, an experimental study on the uplift pressures of waves on a horizontal plate is conducted by use of a series of model tests. Detailed analysis has been given to the formation mechanism of uplift pressures of waves. It is considered that the impact pressure intensity is mainly affected by geometrical factors (tangential angle of waves), dynamic factors (wave height, wave velocity, etc.) and air cushion. Based on the test results, an equation for calculation of the maximum uplift pressure intensity of waves on a plate is presented. A large quantity of test data shows good agreement of the present equation with the test results.展开更多
This article presents an analysis of the scattering of anti-plane shear waves from a single cylindrical inhomogeneity partially bonded to an unbounded magneto-electro-elastic matrix. The magneto-electric permeable bou...This article presents an analysis of the scattering of anti-plane shear waves from a single cylindrical inhomogeneity partially bonded to an unbounded magneto-electro-elastic matrix. The magneto-electric permeable boundary conditions are adopted. The crack opening displacement is represented by Chebyshev polynomials and a system of equations is derived and solved for the unknown coefficients. Some examples are calculated and the results are illustrated. The results show that the COD increases when the piezomagnetic coefficient of the inhomogeneity bonded to the piezoelectric matrix becomes larger, and that the COD decreases when the piezomagnetic coefficient of the matrix with the piezoelectric inhomogeneity increases.展开更多
基金supported by the National Natural Science Foundation of China (Nos.10672108,10572069 and 10820101048)
文摘This paper investigates shear horizontal （SH） waves propagating in a periodically layered structure that consists of piezoelectric （PE） layers perfectly bonded with piezomagnetic （PM） layers alternately. The explicit dispersion relations are derived for the two cases when the propagation directions of SH waves are normal to the interface and parallel to the interface, respectively. The asymptotic expressions for dispersion relations are also given when the wave number is extremely small. Numerical results for stop band effect and phase velocity are presented for a periodic system of alternating BaTiO3 and Terfenol-D layers. The influence of volume fraction on stop band effect and dispersion behaviors is discussed and revealed.
基金supported by National Natural Science Foundation of China(Grant Nos.51075012,10772008)Beijing Municipal Natural Science Foundation of China(Grant No.1122005)
文摘The fundamental shear horizontal（SH0） wave has several unique features that are attractive for long-range nondestructive testing（NDT）. By a careful design of the geometric configuration, electromagnetic acoustic transducers（EMATs） have the capability to generate a wide range of guided wave modes, such as Lamb waves and shear-horizontal（SH） waves in plates. However, the performance of EMATs is influenced by their parameters. To evaluate the performance of periodic permanent magnet（PPM） EMATs, a distributed-line-source model is developed to calculate the angular acoustic field cross-section in the far-field. Numerical analysis is conducted to investigate the performance of such EMATs with different geometric parameters, such as period and number of magnet arrays, and inner and outer coil widths. Such parameters have a great influence on the directivity of the generated SH0 waves that arises mainly in the amplitude and width of both main and side lobes. According to the numerical analysis, these parameters are optimized to obtain better directivity. Optimized PPM EMATs are designed and used for NDT of strip plates. Experimental results show that the lateral boundary of the strip plate has no perceivable influence on SHO-wave propagation, thus validating their used in NDT. The proposed model predicts the radiation pattern ofPPM EMATs, and can be used for their parameter optimization.
基金supported by the National Natural Science Foundation of China(grant number 11862014)the Military Civilian Integration Project of Gansu province.
文摘The scattering of shear horizontal(SH)waves by a circular hole in an infinite piezomagnetic medium affected by magnetic field and compressive stress has been investigated theoretically in this study.The effective elastic,piezomagnetic,and magnetic permeability constants of the piezomagnetic material change with the external magnetic field and compressive stress.The governing differential equations for SH waves scattered by a circular hole are solved using the wave function expansion method.The effects of the magnetic field and compressive stress on mechanical displacement,dynamic stress,and magnetic potential of SH waves around a circular hole are discussed in detail.It has been found that the mechanical displacement around the circular hole increases with magnetic field and decreases with compressive stress.As the magnetic field increases,the maximum dynamic stress increases and structural resonance is strengthened.The findings presented in this study are beneficial for improving the performance of magnetoelastic acoustic wave devices.
基金supported by the National Key R&D Program of China(Grant No.2022YFC3003601)Joint Funds of the National Natural Science Foundation of China Project on Earthquake Science(Grant No.U2239252)the program of the Innovative Research Team in China Earthquake Administration.
文摘Surface irregularities,such as hills and ridges,can significantly amplify ground motion caused by earthquakes.Therefore,in this study,we propose an analytical solution model to investigate the interaction between an asymmetric triangular hill on Earth and SH waves.Firstly,based on the development of wave functions and regional matching techniques,we introduce a semi-circular artificial auxiliary boundary,dividing the solution model into a semi-infinite body containing a semi-circular depression and an asymmetric fan-shaped region.Secondly,we derive the domain function form applicable to solving asymmetric problems.Utilizing the theory of complex variables,we establish a well-posed matrix for solving domain functions within the same coordinate system.Numerical results demonstrate that the scattering of SH waves by a protuberance is jointly influenced by the geometric parameters of the hill and the angle of incidence.Additionally,the frequency of the incident wave also has a certain degree of impact on the displacement amplitude.This study elucidates the scattering mechanism of SH waves by complex boundaries,providing a theoretical reference for building site selection and seismic design.In practical problems,the asymmetric assumption is more applicable than the symmetry assumption.
基金supported by the National Natural Science Foundation of China (Nos. 11072116,10772087 and 10932004)Key Team of Technological Innovation of Zhejiang Province (Grant 2009R50025)+2 种基金Key Industrial Project of Bureau of Science and Technology,City of Ningbo (No. 2005B100015)grants from the Bureau of Science and Technology,City of Ningbo,through the International Collaboration Initiative (Project 2007B10052)Sponsored by K.C.Wong MagnaFund in Ningbo University
文摘We study shear-horizontal （SH） waves in a rotated Y-cut quartz plate carrying an isotropic elastic layer of finite thickness.The three-dimensional theories of anisotropic elasticity and isotropic elasticity are used for the quartz plate and the elastic layer,respectively.A transcen-dental frequency equation that determines the dispersion relations of the waves is obtained.The dispersion relations are obtained and plotted by solving the frequency equation using MATLAB.Approximate dispersion relations are also obtained analytically for two special cases.One is for long waves whose wavelength is much larger than the plate thickness.The other is for the case of a very thin elastic layer.The effects of the elastic layer on the dispersion relations are exam-ined.The results obtained are fundamental and useful to acoustic wave sensors for measuring the mechanical and geometric properties of the elastic layer.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11474195,11274226,51478258 and 51405287
文摘We investigate the three-dimensional （3D） scattering problem of an incident plane shear horizontal wave by a partly through-thickness hole in an isotropic plate, in which the Lamb wave modes are also included due to the mode conversions by the scattering obstacle in the 3D problem. An analytical model is presented such that the wave fields are expanded in all of propagating and evanescent SH modes and Lamb modes, and the scattered far-fields of three fundamental guided wave modes are analyzed numerically for different sizes of the holes and frequencies. The numerical results are verified by comparing with those obtained by using the approximate Poisson/Mindlin plate model for small hole radius and low frequency. It is also found that the scattering patterns are different from those of the SO wave incidence. Our work is useful for quantitative evaluation of the plate-like structure by ultrasonic guided waves.
基金the National Natural Science Foundation of China under Grant No.11672003.
文摘For the inspection of large plate-like structures,the omni-directional guided wave transducer-based system has been regarded as an effective tool since only a few transducers are required to cover the entire inspection area without blind zones.In comparison with Lamb waves,the shear horizontal(SH)wave is more promising because its fundamental mode is non-dispersive.In this work,we proposed an omni-directional SH wave piezoelec trie t ransducer(OSH-PT)based on a radially poled d24-mode PZT ring.Eoth the finite element simulations and experiments were carried out to demonstrate its performance in generating and receiving SH°wave.Results showed that the radially poled OSH-PT could generate single-mode SHo wave and receive SHo wave only over a wide frequency range from 70 to 200 kHz.The obtained signal-to-noise ratio can reach up to 26 dB in generation and 24 dB in reception.The omni-directivity of this OSH-PT is also very good with the deviation only about 6%in both generation and reception of SHo wave.Considering its easy fabrication,low cost and superior performances,this proposed OSH-PT may promote the applications of SHo wave-based inspection in structural health monitoring and nondestructive testing.
基金Project supported by the National Natural Science Foundation of China(Nos.11472182 and 11272222)the China Scholarship Council(No.201907090051)。
文摘The propagation of shear-horizontal(SH)waves in the periodic layered nanocomposite is investigated by using both the nonlocal integral model and the nonlocal differential model with the interface effect.Based on the transfer matrix method and the Bloch theory,the band structures for SH waves with both vertical and oblique incidences to the structure are obtained.It is found that by choosing appropriate interface parameters,the dispersion curves predicted by the nonlocal differential model with the interface effect can be tuned to be the same as those based on the nonlocal integral model.Thus,by propagating the SH waves vertically and obliquely to the periodic layered nanostructure,we could invert,respectively,the interface mass density and the interface shear modulus,by matching the dispersion curves.Examples are further shown on how to determine the interface mass density and the interface shear modulus in theory.
基金National Natural Science Foundation of China.(Grant No.19572077)
文摘Based on the Boussinesq assumption, derived are couple equations of free surface elevation and horizontal velocities for horizontal irrotational flow, and analytical expressions of the corresponding pressure and vertical velocity. After the free surface elevation and horizontal velocity at a certain depth are obtained by numerical method, the pressure and vertical velocity distributions can be obtained by simple calculation. The dispersion at different depths is the same at the O (epsilon) approximation. The wave amplitude will decrease with increasing time due to viscosity, but it will increase due to the matching of viscosity and the bed slope, thus, flow is unstable. Numerical or analytical results show that the wave amplitude, velocity and length will increase as the current increases along the wave direction. but the amplitude will increase, and the wave velocity and length will decrease as the water depth decreases.
文摘This theoretical study reports results on acoustic wave propagation along the interface of two half-spaces representing cubic crystals of both piezoelectric classes ?43m and 23 with strong piezoelectric effect. In similar configurations, the interfacial Maerfeld-Tournois waves can propagate along the interface of two transversely-isotropic materials of class 6 mm, in which the shear-horizontal surface acoustic waves (SH-SAWs) called the Bleustein-Gulyaev (BG) waves can also exist. Cubic piezoelectrics cannot support existence of the surface BG-waves, according to the recent report by Gulyaev and Hickernell. Hence, new interfacial SH-waves are studied in this paper concerning unique direction [101] of wave propagation in cubic crystals using different electrical boundary conditions (EBCs) of both metallized and non-metallized interfaces. The new interfacial SH-waves can always propagate along the interface of two identical piezoelectric crystals with opposite polarization. In this case, the calculated velocities for both EBCs coincide with the velocity of the ultrasonic surface Zakharenko wave (USZW) propagating in direction [101] on the metallized surface of a cubic piezoelectrics. It was also found that the new interfacial SH-waves can exist when wave propagation is along the interface of two dissimilar half-spaces, for instance, the piezoelectric cubic crystals Bi12SiO20 and Bi12GeO20. Several calculations are also carried out as examples. PACS: 51.40.+p, 62.65.+k, 68.35.Gy, 68.35.Iv, 68.60.Bs, 74.25.Ld.
文摘The dynamic stress intensity factor (DSIF) and the scattering of SH wave by circle canyon and crack are studied with Green's function. In order to solve the problem, a suitable Green's function is constructed first, which is the solution of displacement fields for elastic half space with circle canyon under output plane harmonic line loading at horizontal surface. Then the integral equation for determining the unknown forces in the problem can be changed into the algebraic one and solved numerically so that crack DSIF can be determined. Last when the medium parameters are altered, the influence on the crack DSIF is discussed partially with the displacement between circle canyon and crack.
文摘A closed-form analytic solution of two-dimensional scattering and diffraction of plane SH waves by a semi- cylindrical hill with a semi-cylindrical concentric tunnel inside an elastic half-space is presented using the cylindrical wave functions expansion method.The solution is reduced to solving a set of infinite linear algebraic equations.Fourier expansion theorem with the form of complex exponential function and cosine function is used.Numerical solutions are obtained by truncation of the infinite equations.The accuracy of the presented numerical results is carefully verified.
基金supported by National Natural Science Foundation of China (No. 50978183)Tianjin Natural Science Foundation (No. 07JCZDJC10100)
文摘This paper presents a closed-form solution for diffraction of plane SH waves by a semi-circular cavity in half-space by using wave function expansion method. Accuracy of the solution is checked by the displacement residual and stress residual along the boundaries. Numerical results show that there are notable differences for response amplitudes between a semi-circular cavity and a whole-circular cavity in a half-space.
文摘Diffraction of a two-dimensional （2D） semi-circular cavity in a half-space under incident SH-waves is studied using the classic wave function expansion method with a new de-coupling technique. This so-called ＂improved cosine half- range expansion＂ algorithm exhibits an excellent performance in reducing displacement residual errors at two rim points of concern. The governing equations are developed in a manner that minimizes the residues of the boundary conditions. Detailed derivation and analysis procedures as well as truncation of infinite linear governing equations are presented. The semi-circular cavity model presented in this paper, due to its simple profile, is expected to be used in seismic wave propagation studies as a benchmark for examining the accuracies of various analytical or numerical methods for mixed-boundary wave propagation problems.
基金Project supported by the National Natural Science Foundation of China(Grant No.11174235)the Fundamental Research Funds for the Central Universities(Grant No.3102014JC02010301)
文摘The evaporation duct which forms above the ocean surface has a significant influence on electromagnetic wave propagation above 2 GHz over the ocean. The effects of horizontal inhomogeneity of evaporation duct on electromagnetic wave propagation are investigated, both in numerical simulation and experimental observation methods, in this paper. Firstly, the features of the horizontal inhomogeneity of the evaporation duct are discussed. Then, two typical inhomogeneous cases are simulated and compared with the homogeneous case. The result shows that path loss is significantly higher than that in the homogeneous case when the evaporation duct height （EDH） at the receiver is lower than that at the transmitter. It is also concluded that the horizontal inhomogeneity of the evaporation duct has a significant influence when the EDH is low or when the electromagnetic wave frequency is lower than 13 GHz. Finally, experimental data collected on a 149-km long propagation path in the South China Sea in 2013 are used to verify the conclusion. The experimental results are consis- tent with the simulation results. The horizontal inhomogeneity of evaporation duct should be considered when modeling electromagnetic wave propagation over the ocean.
基金supported by National Natural Science Foundation of China under grant No.50978183
文摘A closed-form analytical solution of surface motion of a semi-elliptical cylindrical hill for incident plane SH waves is presented. Although some previous analytical work had already dealt with hill topography of semi-circular and shallow circular, our work aims at calculating surface motion of very prolate hill for high incident frequency, and explaining the special vibrating is checked by boundary conditions, numerical results for and some conclusions are obtained. properties of very prolate hill. Accuracy of the solution surface motion of oblate and prolate hills are calculated,
文摘Uplift pressures of waves acting on horizontal plates are the important basis for design of maritime hollow-trussed structures. In this paper, an experimental study on the uplift pressures of waves on a horizontal plate is conducted by use of a series of model tests. Detailed analysis has been given to the formation mechanism of uplift pressures of waves. It is considered that the impact pressure intensity is mainly affected by geometrical factors (tangential angle of waves), dynamic factors (wave height, wave velocity, etc.) and air cushion. Based on the test results, an equation for calculation of the maximum uplift pressure intensity of waves on a plate is presented. A large quantity of test data shows good agreement of the present equation with the test results.
基金Project supported by the National Natural Science Foundation of China (Nos. 10132010 and 50135030).
文摘This article presents an analysis of the scattering of anti-plane shear waves from a single cylindrical inhomogeneity partially bonded to an unbounded magneto-electro-elastic matrix. The magneto-electric permeable boundary conditions are adopted. The crack opening displacement is represented by Chebyshev polynomials and a system of equations is derived and solved for the unknown coefficients. Some examples are calculated and the results are illustrated. The results show that the COD increases when the piezomagnetic coefficient of the inhomogeneity bonded to the piezoelectric matrix becomes larger, and that the COD decreases when the piezomagnetic coefficient of the matrix with the piezoelectric inhomogeneity increases.
