Approximate and numerical analysis of nonlinear forced vibration of axially moving viscoelastic beams

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.

Polymer-based EMI shielding composites with 3D conductive networks:A mini-review

High-frequency electromagnetic waves and electronic products can bring great convenience to people’s life,but lead to a series of electromagnetic interference(EMI)problems,such as great potential dangers to the normal operation of elec-tronic components and human safety.Therefore,the research of EMI shield-ing materials has attracted extensive attention by the scholars.Among them,polymer-based EMI shielding materials with light weight,high specific strength,and stable properties have become the current mainstream.The construction of 3D conductive networks has proved to be an effective method for the prepara-tion of polymer-based EMI shielding materials with excellent shielding effective-ness(SE).In this paper,the shielding mechanism of polymer-based EMI shield-ing materials with 3D conductive networks is briefly introduced,with emphasis on the preparation methods and latest research progress of polymer-based EMI shielding materials with different 3D conductive networks.The key scientific and technical problems to be solved in the field of polymer-based EMI shielding materials are also put forward.Finally,the development trend and application prospects of polymer-based EMI shielding materials are prospected.

Nonlinear thermomechanical deformation behaviour of P-FGM shallow spherical shell panel

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.

Enhancing power generation of piezoelectric bimorph device through geometrical optimization

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.