Papers by Author: Xin Yue Wu

Abstract: The common requests of the meshless interpolating functions are researched, and its construction method and procedures using the moving least squares method are introduced. The point collocation method is adopted to discretize the Kirchhoff-Helmholtz boundary integral equations into equation groups that constrained by boundary conditions. Constrained equation groups are solved by matrix-division method finally. Therefore, the discrete numeric expression of acoustic radiating and transferring model is obtained. In the example, acoustic field is calculated by the acoustic radiating and transferring model that obtained through both BMLM and BEM, and the results are contrasted between the computational values and the true values. It shows that the interpolating functions of BMLM could be built more flexible. So the accuracy of interpolation and calculation by BMLM is higher.

Abstract: Piezoelectric transducer with negative impedance matching circuit is put forward to enhance its performance in broadband frequencies. The typical multi-physics problem is coupled with sound wave equations, structure stress-strain equations, piezoelectric constitutive equations and electric ordinary equations, and it is analyzed with FEM in detail. Frequency response characteristics are simulated when shunted with negative-impedance in series. When proper negative synthesized elements are connected, the performance of low frequencies and bandwidth are enhanced obviously.

Abstract: The transfer matrix of rolling bearing including squeeze film damper (SFD) is studied, and the rotor – bearing system is modeled by transfer matrix method of multi-body system. It is proved by an example that the method, which provides a new idea to solve the problem of complex rotor – bearing system, is feasible and effective.

Abstract: A finite-difference numerical model is used to study the influence of surface textures configuration and depth on lubrication performance of hydrodynamic journal bearing. Reynolds equation is adopted to calculate the bearing dimensionless load carrying capacity, friction force and friction coefficient under different eccentricity ratio, textures configuration and depth. Results show that partial texturing in the inlet zone with shallow dimples and in the cavitation zone with deep dimples could improve bearing performance appreciably. The effect of the textures on bearing tribological performance was influenced by the eccentricity ratio. The advantage of partial textures decreases when the eccentricity ratio increases.

Abstract: In the paper, the interface crack of rubber - metal ring under the radial displacement load was studied by nonlinear finite element method, changes of the tear energy with crack dimension which extending from extrusion end and tensile end along the axial and circumferential direction to the interface was analyzed. The result is that there is a certain possibility of axial extension in the tensile end. The crack propagation is most likely to occur along the circumferential direction while is impossible along either axial or the circumferential direction in the extrusion end.

Abstract: The far-filed underwater explosive shock wave pressure and impulse is simulated by the FEM code LS-DYNA, and the simulation results are found having rapid decay characteristic through compared with the empirical results. Based on this phenomenon, the relations, whose validity is verified through a computation instance, between simulation mass and actual mass under given initial conditional is obtained by using curve fitting. Using those equations, the accuracy of LS-DYNA to simulate far-field underwater explosive can significantly be increased, thus the ability of this code to simulate far-field underwater explosion is enhanced.

Abstract: A finite-difference numerical model is used to study the influence of surface texture on lubrication performance of hydrodynamic journal bearing. Reynolds equation is adopted to calculate the bearing load carrying capacity, friction force and friction coefficient under different width-diameter ratio, different eccentricity ratio and different texture location. Results show that partial texture along the circumferential direction on the bearing with small width-diameter ratio will increase bearing performance appreciably. Partial texture along the axial direction will decrease friction coefficient effectively, especially at the film inlet zone or the position of film pressure trending to zero.

Abstract: Piezoelectric acoustic sensor with negative impedance matching circuit is put forward to enhance its sensitivity at low frequencies. The multi-physics problem coupled with sound wave equations, structure stress-strain equations, piezoelectric constitutive equations and electric ordinary equations is analyzed with FEM in detail. Frequency response characteristics are simulated when shunted with negative-capacitance, resistance in series. Sensitivity is obtained from 1kHz to 5kHz. When used proper electrical elements, the sensitivity of the piezoelectric sensor can even exceed that of no matching circuit over 2 factors in broad band.

Abstract: Piezoelectric material shunted with negative capacitance can be used to insulate sound theoretically. But sound insulation of the system is limited by many factors. The dielectric and mechanical loss of the piezoelectric system deteriorate seriously the ability at some frequencies. According to the ideal electric elements formulas, the capacitance has imaginary part because of the loss. It has important influence on sound insulation ability. If a series resistance is introduced into the shunting circuit to form the imaginary part to compensate the loss, it is dependent on frequency. Sound insulation would be increased only in narrow band, and at some frequencies the system with the shunting circuit even becomes unstable.

Abstract: Piezoelectric system shunted with proper negative capacitance in series has low dynamic stiffness. According to frequency characteristic equations of the piezoelectric system, optimal parameters and characteristics of both shunted series structures were deduced and compared theoretically. One is negative-capacitance and resistance in series, and the other is negative-capacitance, resistance and inductance in seires. It presented that high damping characteristic can be obtained at low frequencies when shunted with series negative-capacitance. If proper inductance is included in shunt circuit, effective bandwidth could be extended and the peak of amplitude of response is decreased, what’ more, the stability of this structure is enhanced. This technology can be used in vibration isolators or sensors and the shunt structure including inductance is recommended.