Steady-state periodical response is investigated for an axially moving viscoelastic beam with hybrid supports via approximate analysis with numerical confirmation. It is assumed that the excitation is spatially unifor...Steady-state periodical response is investigated for an axially moving viscoelastic beam with hybrid supports via approximate analysis with numerical confirmation. It is assumed that the excitation is spatially uniform and temporally harmonic. The transverse motion of axially moving beams is governed by a nonlinear partial-differential equation and a nonlinear integro-partial-differential equation. The material time derivative is used in the viscoelastic constitutive relation. The method of multiple scales is applied to the governing equations to investigate primary resonances under general boundary conditions. It is demonstrated that the mode uninvolved in the resonance has no effect on the steady-state response. Numerical examples are presented to demonstrate the effects of the boundary constraint stiffness on the amplitude and the stability of the steady-state response. The results derived for two governing equations are qualitatively the same,but quantitatively different. The differential quadrature schemes are developed to verify those results via the method of multiple scales.展开更多
In this paper, it is demonstrated that the power output of a bimorph energy harvesting device can be significantly enhanced through geometrical optimization. The results of the study show that the maximum power is gen...In this paper, it is demonstrated that the power output of a bimorph energy harvesting device can be significantly enhanced through geometrical optimization. The results of the study show that the maximum power is generated when the length of piezoelectric layer is 1/3 and the length of proof mass is 2/3 of the total device length. An optimized device with a total volume of approximately 0.5 cm3 was fabricated and was experimentally character- ized. The experimental results show that the optimized device is capable of delivering a maximum power of 1.33 mW to a matched resistive load of 138.4 kΩ, when driven by a peak mechanical acceleration of 1 g at the resonance frequency of 68.47 Hz. This is a very significant power output representing a power density of 2.65 mW/cm3 compared to the value of 200 9W/cm3 normally reported in literature.展开更多
In the present article, the linear and the nonlinear deformation behaviour of functionally graded （FG） spherical shell panel are examined under thermomechanical load. The temperature- dependent effective material pr...In the present article, the linear and the nonlinear deformation behaviour of functionally graded （FG） spherical shell panel are examined under thermomechanical load. The temperature- dependent effective material properties of FG shell panel are evaluated using Voigt＇s micro-mechanical rule in conjunction with power-law distribution. The nonlinear mathematical model of the FG shell panel is developed based on higher-order shear deformation theory and Green-Lagrange type geometrical nonlinearity. The desired nonlinear governing equation of the FG shell panel is computed using the variational principle. The model is discretised through suitable nonlinear finite element steps and solved using direct iterative method. The convergence and the val- idation behaviour of the present numerical model are performed to show the efficacy of the model. The effect of different parameters on the nonlinear deformation behaviour of FG spherical shell panel is highlighted by solving numerous examples.展开更多
One form of energy generation that is expected to be on the rise in the next several decades is thermoelectric power generation (TEPG) which converts heat directly to electricity.Compared with other methods,TEPG posse...One form of energy generation that is expected to be on the rise in the next several decades is thermoelectric power generation (TEPG) which converts heat directly to electricity.Compared with other methods,TEPG possesses the salient features of being compact,light-weighted,noiseless in operation,highly reliable, free of carbon dioxide emission and radioactive substances. Low current conversion efficiency and high cost,however,are some of the disadvantages. Use of TEPG is therefore justified to hightech applications associ- ated with aerospace,military operation,tel-communication and navigation,instrumentation of unmanned vehicles moni- tored from remote locations.More-over,TEPG does not con- tribute to the depletion of natural resource and pollution of the environment such as climate warming that has been a concern in recent times.This work is concerned with provid- ing an overview of the state of the art of TEPG with empha- ses placed on assessing its current and potential applica- tion.Pointed out are the ways to fabricate high performance thermoelectric material,a hurdle to overcome for the en- hancement of TEPG device efficiency.展开更多
基金supported by the National Natural Science Foundation of China (10902064 and 10932006)China National Funds for Distinguished Young Scientists (10725209)+2 种基金the Program of Shanghai Subject Chief Scientist (09XD1401700)Shanghai Leading Talent Program,Shanghai Leading Academic Discipline Project (S30106)the program for Cheung Kong Scholars Programme and Innovative Research Team in University (IRT0844)
文摘Steady-state periodical response is investigated for an axially moving viscoelastic beam with hybrid supports via approximate analysis with numerical confirmation. It is assumed that the excitation is spatially uniform and temporally harmonic. The transverse motion of axially moving beams is governed by a nonlinear partial-differential equation and a nonlinear integro-partial-differential equation. The material time derivative is used in the viscoelastic constitutive relation. The method of multiple scales is applied to the governing equations to investigate primary resonances under general boundary conditions. It is demonstrated that the mode uninvolved in the resonance has no effect on the steady-state response. Numerical examples are presented to demonstrate the effects of the boundary constraint stiffness on the amplitude and the stability of the steady-state response. The results derived for two governing equations are qualitatively the same,but quantitatively different. The differential quadrature schemes are developed to verify those results via the method of multiple scales.
文摘In this paper, it is demonstrated that the power output of a bimorph energy harvesting device can be significantly enhanced through geometrical optimization. The results of the study show that the maximum power is generated when the length of piezoelectric layer is 1/3 and the length of proof mass is 2/3 of the total device length. An optimized device with a total volume of approximately 0.5 cm3 was fabricated and was experimentally character- ized. The experimental results show that the optimized device is capable of delivering a maximum power of 1.33 mW to a matched resistive load of 138.4 kΩ, when driven by a peak mechanical acceleration of 1 g at the resonance frequency of 68.47 Hz. This is a very significant power output representing a power density of 2.65 mW/cm3 compared to the value of 200 9W/cm3 normally reported in literature.
文摘In the present article, the linear and the nonlinear deformation behaviour of functionally graded （FG） spherical shell panel are examined under thermomechanical load. The temperature- dependent effective material properties of FG shell panel are evaluated using Voigt＇s micro-mechanical rule in conjunction with power-law distribution. The nonlinear mathematical model of the FG shell panel is developed based on higher-order shear deformation theory and Green-Lagrange type geometrical nonlinearity. The desired nonlinear governing equation of the FG shell panel is computed using the variational principle. The model is discretised through suitable nonlinear finite element steps and solved using direct iterative method. The convergence and the val- idation behaviour of the present numerical model are performed to show the efficacy of the model. The effect of different parameters on the nonlinear deformation behaviour of FG spherical shell panel is highlighted by solving numerous examples.
文摘One form of energy generation that is expected to be on the rise in the next several decades is thermoelectric power generation (TEPG) which converts heat directly to electricity.Compared with other methods,TEPG possesses the salient features of being compact,light-weighted,noiseless in operation,highly reliable, free of carbon dioxide emission and radioactive substances. Low current conversion efficiency and high cost,however,are some of the disadvantages. Use of TEPG is therefore justified to hightech applications associ- ated with aerospace,military operation,tel-communication and navigation,instrumentation of unmanned vehicles moni- tored from remote locations.More-over,TEPG does not con- tribute to the depletion of natural resource and pollution of the environment such as climate warming that has been a concern in recent times.This work is concerned with provid- ing an overview of the state of the art of TEPG with empha- ses placed on assessing its current and potential applica- tion.Pointed out are the ways to fabricate high performance thermoelectric material,a hurdle to overcome for the en- hancement of TEPG device efficiency.
