Dissertation
Dissertation > Mathematical sciences and chemical > Physics > Solid State Physics > Solid nature of the > Electrical Properties

Coupling Problems of Multiple Physical and Mechanical Fields in Sense and Actuating Devices/structures

Author ZhangBenNiu
Tutor ZhangJunQian
School Chongqing University
Course Solid Mechanics
Keywords mechanical/electrical coupling effect electrical/magnetic coupling effect piezoelectric ceramic magnetic field sensor/actuator singular integro-differential equation
CLC O482.4
Type PhD thesis
Year 2003
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One of the basic characters of sensors/actuators is to transform one physical quantity into another physical quantity that is easier to measure or to transform a control physical signal into another kind of physical signal by the coupling of the physical quantities. There are two important aspects of the research of sensors/actuators: mechanical/electrical coupling effect and electrical/magnetic coupling effect. In this dissertation, an investigation on the mechanical/electrical coupling effect and on the electrical/magnetic coupling effect will be conducted. In the first part of the dissertation, the author will develop a model for a single piezoelectric layer bonded on an elastic structure. The model can consider the longitudinal and transverse electric field, the distributions of the interfacial normal stress and shear stress at the same time. Meanwhile this model can analyze the sense/actuating effects of the thin piezoelectric layer on the elastic structure accurately. And so it can avoid the disadvantage of the thin film/substrate theory which cannot predict the interfacial normal stress. To deal with the strong singular integral-high order differential governing equations in the single-layer model, the author developed a synthetical numerical algorithm which includes numerical integral algorithm, finite difference algorithm and the method to weaken the strong singular kernels in the integrals. Using the model and the algorithm, the electrical fields and the interfacial stresses of a PZT-5H piezo-elastic sensor/actuator structure are analyzed. The results show that: There are severe disturbs at the tips of the piezoelectric sensor/actuator. So the electric field intensity cannot be simply assumed to be uniform. There are concentrations of the interfacial normal and shear stresses at the tips of the interface between the piezoelectric layer and the substrate. And the value of the normal stress is much bigger than the shear stress, so the interfacial normal stress should be the main cause of the interfacial delamination. The output voltage will increase when both the length and the thickness of the piezoelectric layer increase. Meanwhile the change of the voltage by the change of the length will decrease when the thickness of the piezoelectric layer decrease. And when the thickness of the piezoelectric layer is 0.01mm, the change of the length of the<WP=8>piezoelectric layer will almost have no influence on the output voltage. However, one has to consider the effect of the length for the piezoelectric layer, which cannot be made to be such thin.For the thick piezoelectric layer, the author divided the layer into several subdivided layers with the same thickness, and deduced the governing integral-differential equations of the subdivided model.The numerical simulation is processed by the same synthetical algorithm. The results show that: for the piezoelectric actuator, the electric field produced by a unit applied voltage and the interfacial stress of the structure will decrease when the thickness of the piezoelectric layer increase. While the disturb of the electric field and the effect of the interfacial normal stress will increase when the thickness of the piezoelectric layer increase. For the piezoelectric sensor, the electric field produced by a unit strain applied on the substrate will have a little decrease when the thickness of the piezoelectric layer increase. While the disturb of the electric field will increase when the thickness of the piezoelectric layer increase. And the output voltage will increase by the increase of the size of the piezoelectric layer, the output voltage will have a linear relationship with the size (length or thickness) of the piezoelectric layer.In the second part of the dissertation, the author discusses a new magnetic sensor: magnetic-frequency sensor. The change of the output frequency is proportional to the change of the flux rate, which is induced by the change of the magnetic field, i.e. . A pendulum experiment and a magnetic field sensing experime

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