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A novel piezoelectric actuator is proposed to enhance its displacement in broad band at low frequencies. Its structure consists of a tunable stiffness part and a driven part. The tunable stiffness part is the piezoelectric stacks shunted with negative capacitance and its effective stiffness could be softening widely under the proper capacitance ratios at low frequencies. The principle of tunable stiffness...
The effective stiffness and the natural frequencies of a piezoelectric system shunted with negative capacitance could be changed with the capacitance ratios. Integrated the shunted piezoelectric stacks with driven piezoelectric patches, a novel non-resonant smart transducer is put forward and its low frequency performance is enhanced obviously. The proposed smart transducer is simulated with multi-physics...
To calculate transfer matrix of the plane non-uniform pure bending beam by transfer matrix method of multibody system quickly and efficiently, the stiffness matrix of the beam was calculated by the finite element method firstly, and then the transfer matrix of the beam was calculated. It was proved by the example that this method is effective and feasible. And it provided a new idea to solve the problem...
Dynamic model of a rotor-journal bearing system under base shock excitations was established. Energy differential equations were derived by applying Lagrange equation with FE in space domain. Bending and shear deformation energy of shaft element were taken into account. Inertia force due to rotor mass eccentricity was introduced and treated as a generalized external force. Oil-film force was determined...
This paper extends the transfer matrix technique (TMT) to the shock response analysis of a large complex propulsion shaft system under base shock excitations by a transfer matrix-Newmark formulation itegration method. In order to eliminate the numerical instability of TMT, the transfer vector {fT : ëT}T is used, instead of the traditional one {fT : eT}T. For the shock response computation of the...
To investigate the influence of loading opportunity of shock excitations on dynamic responses of rotor-bearing systems subjected to base shock excitations, dynamic differential equations of a rigid rotor-bearing system were established. Gyroscopic effect and mass eccentricity of the rotor were considered. Shock responses were obtained by numerical simulation. Four cases are investigated that will...
The conventional Newmark method based on average acceleration concept cannot be directly applied to solve state-space first-order differential equations, which contains no explicit acceleration terms. Combining with a Newmark iteration algorithm based on average velocity concept, a Riccati-transfer matrix method was proposed to obtain transient response of rotor systems under base shock excitations...
Aimed at the vacancy of Quick Fire-Fighting method for Vessel Electric Equipment, a kind of monitoring and quick Fire-Fighting System for vessel electric equipment was developed, which has filled the technology vacancy in inland. The functions, such as fire monitoring, alarming and Quick Fire-Fighting before opening of the electric equipment case, are very important for reducing the fire loss and...
New semi-passive negative impedance matching technology is put forward to enhance the sensitivity of piezoelectric acoustic sensor at low frequencies; what's more, the bandwidth of high sensitivity is very broad. Mason electro-mechanical equivalent model of piezoelectric acoustic sensor is established and analyzed. Based on impedance matching theory, the parameters of matching circuit are obtained...
Semi-passive shunted piezoelectric layer for sound absorption is a typically multi-physics problem 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 semi-passive piezoelectric sound absorption structure shunted with negative-capacitance,...
Basic characteristics of piezoelectric system shunted with negative capacitance are studied in this paper. After established general frequency domain equations of piezoelectric system shunted with negative capacitance, the expressions of natural frequency, dynamic stiffness and generalized electro-mechanical coupling factor are obtained. For the case there is only a negative capacitance in the shunting...
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