Facing the problems lack of considering the non-uniform distribution of the static bias magnetic field and computing the panicle displacements in the simulation model of electromagnetic acoustic transducer （EMAT）, a...Facing the problems lack of considering the non-uniform distribution of the static bias magnetic field and computing the panicle 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.展开更多
The governing equation and energy equations for thermal-elastic coupling vibration of cylindrical shell were developed. The Garlerkin method was used in numerical process. Some useful result can be concluded from nume...The governing equation and energy equations for thermal-elastic coupling vibration of cylindrical shell were developed. The Garlerkin method was used in numerical process. Some useful result can be concluded from numerical result. With the increase of the amplitude of temperature and coupling coefficient, the speed of vibration decaying becomes slower and the coupling effect becomes weaker. The larger the ration of length to radius and length to thickness, the faster the decaying of the vibration amplitude and the vibration frequency increase. It means the coupling effect gets stronger. The larger the coupling coefficient, the smaller the axial stress, the axial force and the bendind moment are.展开更多
This paper presents an accurate and efficient method for the computation of resonant frequencies and radiation patterns of a dual frequency stacked circular microstrip antenna.The problem is first formulated using th...This paper presents an accurate and efficient method for the computation of resonant frequencies and radiation patterns of a dual frequency stacked circular microstrip antenna.The problem is first formulated using the Hankel transform domain approach and expressions are obtained for the Green's function in the Hankel transform domain,which relates the electric surface currents on the circular disks and tangential electric field components on the surfaces of the substrates. Then Galerkin's method together with Parsebal's relation for Hankel transformation is used to solve for the unknown currents, In the derivation process,the resonant frequencies are numerically determined as a function of the radii of two circular disks and thicknesses and relative permittivies of two substrates.Finally,the far zone radiation patterns are directly obtained from the Green's function and the currents. The numerical results for the resonant frequencies and radiation patterns are in excellent agreement with the available experimental data corroborating the accuracy of the present method.展开更多
基金Project(10974115) supported by the National Natural Science Foundation of China
文摘Facing the problems lack of considering the non-uniform distribution of the static bias magnetic field and computing the panicle 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.
文摘The governing equation and energy equations for thermal-elastic coupling vibration of cylindrical shell were developed. The Garlerkin method was used in numerical process. Some useful result can be concluded from numerical result. With the increase of the amplitude of temperature and coupling coefficient, the speed of vibration decaying becomes slower and the coupling effect becomes weaker. The larger the ration of length to radius and length to thickness, the faster the decaying of the vibration amplitude and the vibration frequency increase. It means the coupling effect gets stronger. The larger the coupling coefficient, the smaller the axial stress, the axial force and the bendind moment are.
文摘This paper presents an accurate and efficient method for the computation of resonant frequencies and radiation patterns of a dual frequency stacked circular microstrip antenna.The problem is first formulated using the Hankel transform domain approach and expressions are obtained for the Green's function in the Hankel transform domain,which relates the electric surface currents on the circular disks and tangential electric field components on the surfaces of the substrates. Then Galerkin's method together with Parsebal's relation for Hankel transformation is used to solve for the unknown currents, In the derivation process,the resonant frequencies are numerically determined as a function of the radii of two circular disks and thicknesses and relative permittivies of two substrates.Finally,the far zone radiation patterns are directly obtained from the Green's function and the currents. The numerical results for the resonant frequencies and radiation patterns are in excellent agreement with the available experimental data corroborating the accuracy of the present method.
