Papers by Author: Feng Jin

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Authors: Zheng Hua Qian, Feng Jin, Sohichi Hirose
Abstract: In this paper, we study the propagation of electro-elastic Love waves in a piezoelectric layered solid consisting of a transversely isotropic piezoelectric ceramic film deposited on an isotropic metal substrate. Dispersion relations are obtained in a very concise mathematical form for both electrically open and shorted circuits. Numerical example is given for a PZT-4/steel system. An interesting phenomenon on the fundamental mode of the Love waves in the case of electrically shorted circuit is realized and validated through the discussion on the limit values of phase velocity using the obtained dispersion relations. This validation appears new and is significant to understand the Love wave modes themselves and to the design of acoustic wave devices.
Authors: Zheng Hua Qian, Feng Jin, Kikuo Kishimoto
Abstract: The propagation behavior of Love waves in a functionally graded material layered half-space with initial stress is taken into account. The Wentzel-Kramers-Brillouin (WKB) asymptotic technique is adopted for the theoretical derivations. The analytical solutions are obtained for the dispersion relations and the distributions of mechanical displacement and stress along thickness direction in the layered structure. Firstly, these solutions are used to study effects of the initial stress on the dispersion relations and phase velocities, then influences of the initial stress on the distributions of mechanical displacement and shear stresses along thickness direction are discussed in detail. Numerical results obtained indicate that the phase velocity of Love wave increases with the increase of the magnitude of the initial tensile stress, while decreases with the increase of the magnitude of the initial compression stress. The effects on the dispersion relations of the Love wave propagation are negligible as the magnitudes of the initial stress are less than 100MPa. Some other results are shown for distributions of field quantities along thickness direction. The results obtained are not only meaningful for the design of functionally graded structures with high performance but also effective for the evaluation of residual stress distribution in the layered structures.
Authors: Feng Jin, Kikuo Kishimoto, Hirotsugu Inoue, Takashi Tateno
Abstract: The linear ultrasonic technique has been extensively used as a powerful, non-destructive test tool for reliability testing and failure analysis of electronic packaging. This is used most often in the inspection of defects such as delaminations, voids, or cracks through use of a SAM (Scanning Acoustic Microscope). Then, as the reliability level that is required of electronic packaging becomes higher and the thickness of package becomes thinner, the possible defect which needs to be detected becomes smaller. In the conventional SAM, however it is very difficult to detect small defects less than m µ 1 . 0 , such as micro-delaminations. In order to solve such a problem, this paper proposes a nonlinear ultrasonic method, where the nonlinearity caused by the effect of crack-face interactions is considered. The basic concept of this method involves harmonic frequencies that are generated in the transmitted ultrasonic wave due to the partial contact at the interface of micro-delamination. As an evaluation index, the nonlinear parameter dependent on the amplitude of the second order harmonic frequency component is obtained by spectral analysis of the transmitted signal. Experimental results show that the nonlinear parameter has good correlation with the micro-gap and the proposed method can detect the micro-delamination even less than nm 1 .
Authors: Feng Jin, Kikuo Kishimoto, H. Qing, Hisahiro Inoue, Takashi Tateno
Abstract: Layered structures, especially thin film/coating substrate system play important roles in micro-electro-mechanical system (MEMS) and microelectronics packages. Many surface acoustic wave (SAW) devices/sensors adopt the layered structures to achieve high performance that with a piezoelectric layer deposited on the substrate. Recently, much work has been carried out concerning the propagation behavior of surface waves in piezoelectric layered structures, in which the piezoelectric layers are bonded perfectly with the substrate materials. Actually, due to the thermal mismatch, the unavoidable initial stress in the piezoelectric layer and the brittleness nature of piezoelectric ceramics, imperfections exist in the interfaces of these layered structures. Due to the penetration properties of surface waves, the imperfect interfaces may influence the propagation behavior of surface waves. Up to now, little attention has been paid to the propagation behavior of surface waves in layered piezoelectric structures that the imperfect interfaces are taken into account. The propagation behavior of Love waves in a piezoelectric layered structure with imperfect interface is taken into account. Solutions of the mechanical displacement and electrical potential function are obtained for the piezoelectric layer and substrate, respectively, by solving the coupled electromechanical field equations. Effect of imperfect interface on the phase velocity of Love wave propagation is discussed in detail. Results obtained indicate that imperfect interface can greatly influence the propagation of Love waves under some certain conditions. The potential application of these results in the field of mechanical behavior of materials is also shown.
Authors: Zheng Hua Qian, Feng Jin, Zi Kun Wang, Kikuo Kishimoto
Abstract: The diffraction of Lamb waves by a finite delamination situated on a random plane parallel to the symmetric plane of a laminated plate is taken into account. Two imaginary planes are introduced to solve the problem by adopting the method of mode matching. By taking an appropriate finite number of terms of the infinite expansion series and some selected points on the two imaginary planes through convergence and precision tests, a matrix equation is obtained to evaluate the expansion coefficients numerically. Reflection coefficients versus the normalized length a/h and the relative location h1/h of the delamination are calculated in the low-frequency domain, the relative errors are found to be less than 1%. Results obtained indicate that the theory developed in this paper is meaningful for the detection of both the size and the location of a delamination in a laminated plate by cooperating with experimental techniques for the non-destructive evaluation (NDE) technology.
Authors: B. Han, Feng Xian Xin, Feng Jin, T.J. Lu
Abstract: Hail impact has been a long lasting threat for aircraft structures such as leading edges and forward sections. To mimic the physical process of hail impact on aircraft structures, a FEM model is established for all-metal sandwich structures having four different kinds of cores: corrugated core, pyramidal lattice core, metal foam core, and corrugation-foam hybrid core. Smoothed particle hydrodynamic (SPH) method is employed to predict the failure behavior of the hail, whilst the sandwich structures are described by a Lagrangian reference configuration. It is demonstrated that the sandwich structures with hybrid core outperforms the other three types for withstanding hail penetration as well as absorbing impact energy.
Authors: Feng Jin, Kikuo Kishimoto, Zheng Hua Qian, Zi Kun Wang
Abstract: The wave function expansion method is engaged for the theoretical derivations to study the effect of material parameters perturbations on the resonance acoustic scattering behavior of 1-3 piezoelectric composites. Numerical examples are provided to verify the effectiveness of the analysis. Results obtained are meaningful for the non-destructive evaluation of 1-3 piezoelectric composites.
Authors: Zheng Hua Qian, Feng Jin, Zi Kun Wang, Kikuo Kishimoto
Abstract: Following the advances in structural applications, composite structures are being used commonly in transducer applications to improve acoustic, mechanical and electrical performance of piezoelectric devices. Functional composite transducers for sensors and actuators generally consist of ceramics and polymers, the disadvantage of the brittleness nature of the piezoelectric ceramics can be overcome and the structures especially good for sensing can be allowed for building up. Propagation behavior of horizontally polarized shear waves (SH-waves) in piezoelectric ceramic-polymer composites with 2-2 connectivity is taken into account. The multilayer structures are consisted of piezoelectric thin films bonded perfectly with polymeric thin films alternately. The phase velocity equations of SH-waves propagation in the piezoelectric ceramic-polymer composites with 2-2 connectivity are obtained for the cases of wave propagation in the direction perpendicular to the layering and along the layering, respectively. Filter effect of this kind of structure and the effect of volume fraction and shear modulus ratio of piezoelectric layer to polymer layer on the phase velocity are discussed in detail, respectively. One practical combination of piezoelectric thin film-polymer thin film multilayer system is chosen to carry out the numerical simulation, some basic properties of SH-waves propagation in above multilayered structures are revealed.
Authors: Zi Kun Wang, Feng Jin, Z. Zong, Tie Jun Wang
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