Papers by Author: Shao Ze Yan

Abstract: Planetary gears are the most popular transmission machinery in large reduction ratio circumstances, which is because of the advantages of compactness, co-axial and high power efficiency. Accurate dynamic model is crucial when planetary gears are used in precise positioning and controlling systems. A dynamic model considering gear backlash and bearing compliance is established in this work. A typical planetary gearbox is simulated with the model. The results prove the validity of the model and demonstrate that gear backlash and bearing compliance have significant influence on planetary gear transmission.

Abstract: With the scenario of reliability estimation, a geometrically complex mechanical/structural component with multiple damage sites should be treated as a system, since there are many links (damage sites) of similar failure probabilities on any of such a component and the failures of the individual damage sites are not perfectly dependent of each other. Conventional system reliability model is not applicable to such a system because of the statistical dependence among the element (damage site) failures. To estimate the reliability of a mechanical system (or a complex component) in which element (damage site) failure dependence plays an important role, a model capable of reflecting the effect of element failure dependence is necessary. The present paper develops models which can deal with multiple damage sites and multiple failure mechanisms, reflect the dependence among element failure events and that among different failure modes. Such models are applicable to both typical mechanical systems and various components.

Abstract: The upper and lower bound estimation of natural frequencies for intelligent truss structure with uncertain-but-bounded parameters is studied in this paper. Firstly, following the finite element method, the expressions of the interval stiffness and interval mass matrix of piezoelectric intelligent truss structures are derived directly from the interval parameters. Then, based on the matrix perturbation and interval extension theory, an interval parameter perturbation method is proposed for solving the upper and lower bound of natural frequencies. Finally, a 16-bar planar intelligent truss structure is used as an example to illustrate the applicability and validity of the presented method, and some useful conclusions are obtained.

Abstract: A theoretical model of the displacement-heating response of the differential shape memory alloy (SMA) actuator was developed. The model was constructed by using the constitutive equation and considering the force equilibrium and the energy balance on the SMA. The output displacement was predicted as a function of the heating power by the model and the simulations of the output displacement and temperature of the SMA actuator were also obtained. To evaluate the model, a prototype actuator which was made up of two SMA coil springs placed opposite each other was briefly described and an experimental setup of the SMA actuator was developed to study the relations among the heating power, the temperature and the output displacement of the SMA actuator. The similarity between the simulated and experimental results verified the proposed model, which indicated that the proposed model could express the thermo-mechanical behavior of the differential Ni-Ti SMA actuators.

Abstract: The responses of the piezoelectric stack actuator under electro-mechanical loading are investigated. Two types of tests are performed: influences of the preload on characteristics of the stack and dynamic test. Experimental results indicate strong dependence of the stack properties on the electro-mechanical loading conditions. The displacement output is initially enhanced with an increase of the mechanical preload, and the maximum value is obtained at the preload of about 0.4 kN. But much higher preload will cause the decrease of the displacement output. The effective piezoelectric coefficient and the hysteresis degree are employed to describe the variations of the stack’s performances caused by the mechanical preload. The effective piezoelectric coefficient under different preloads can be calculated by using experimental results of the displacement output and input voltage. Within low frequency band of about 400 Hz, the displacement magnitude of the stack is nearly constant, and the phase lag increases with the increase of the driving frequency at the applied sine sweep voltage with the amplitude of 150V.

Abstract: The influence of electro-mechanical operation conditions on the actuation capabilities of the piezoelectric bimorph is investigated in this paper. The objective is to compare the performance of the piezoelectric bimorph in different operation conditions and to determine the optimum operating conditions. An experimental set-up is built, and a series of experiments are presented to investigate the static and dynamic characteristics of the bimorph, including tip displacements of the bimorph under different preloads, dynamic response at different drive frequencies, step response and creep. Some properties such as displacement output, force output and hysteresis of the piezoelectric bimorph under different operating conditions are evaluated. Experimental results indicate strong dependence of both elastic and piezoelectric properties of the bimorph on the operating conditions.

Abstract: AC and DC conductivities have been measured by using the real (e¢) and imaginary (e¢¢) parts of the dielectric constant data of glass and glass-ceramics (GC) at different temperatures in the rage 297-642K and in the frequency range 100 Hz to 10 MHz. Using Anderson –Stuart model, we have calculated the activation energy, which is observed to be lower than that of the DC conductivity. The analysis for glass/glass-ceramics indicates that the conductivity variation with frequency exhibits an initial linear region followed by nonlinear region with a maximum in the high-frequency region. The observed frequency dependence of ionic conductivity has been analyzed within the extended Anderson–Stuart model considering both the electrostatic and elastic strain terms. In glass/glassceramic the calculations based on the Anderson-Stuart model agree with the experimental observations in the low frequency region but at higher frequencies there is departure from measured data.

Abstract: Piezoelectric materials have an ability to efficiently transform mechanical energy to electric energy and vice versa, which makes them useful as structural dampers. The objective of this work is to investigate the damping capabilities of a piezoceramic shunted by different types of passive electrical circuits. The material properties of the shunted piezoceramic are modeled and the analytical results show that the shunted piezoceramic exhibits different damping potentials depending on the piezoelectric properties of the material and the shunt circuits. An experimental set-up of a cantilever beam with surface bonded piezoceramics is proposed to investigate the damping characteristics of the shunted piezoceramic. An analytical model is developed to describe the influence of the shunted piezoceramic on the dynamic response of the beam. The damping performances of the piezoceramic shunted by different circuits are compared respectively and the experimental results show approximate agreement with the numerical simulations of the model.