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Wave Propagation of Porous Nanoshells
摘要： This study aims at investigating the wave propagation of porous nanoshells. The Bi-Helmholtz non-local strain gradient theory is employed in conjunction with a higher-order shear deformation shell theory, in order to include the size-dependent effects. The nanoshells are made of a porous functionally graded material (P-FGM), whose properties vary continuously along the thickness direction. A variational approach is here applied to handle the governing equations of the problem, which are solved analytically to compute the wave frequencies and phase velocities as function of the wave numbers. The sensitivity of the wave response is analyzed for a varying porosity volume fraction, material properties, non-local parameters, strain gradient length scales, temperature, humidity, and wave numbers. Based on the results, it is verified that the size-dependence of the response is almost the same to the one of plates, beams and tubes.
关键词： doubly-curved nanoshell,wave propagation,higher-order shear deformation shell theory,porous materials,generalized non-local strain gradient theory
更新于2025-09-23 15:23:52
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Effects of the microstructure and density profiles on wave propagation across an interface with material properties
摘要： The characterization of the interphase condition between two materials is current in mechanics. In general, its modeling is achieved by considering an interface with only purely elastic properties. In this paper, following previous works, also inertial interface properties are taken into account. For sufficiently low-frequency regime, we investigate two density profiles (affine and quadratic), for the interphase. Moreover, the interface and the interphase are placed between two solids with different characteristics. The first one is non-dispersive, while for the second one three cases are considered: (a) solid without microstructure, i.e., a Cauchy continuum, (b) solid with microstructure characterized by normal dispersion, i.e., a strain gradient continuum, and (c) by anomalous dispersion. The reflection coefficients are plotted for each case. These results are evaluated with respect to a benchmark finite elements simulation of the finite heterogeneous interphase, and the error is discussed. It is shown that the effects of microstructure can be appreciated at higher frequencies and that the proposed model results to be accurate.
关键词： Strain gradient,Reflection coefficient,Interface,Interphase,Density profiles,Wave propagation
更新于2025-09-23 15:23:52
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Energy harvesting properties of the functionally graded flexoelectric microbeam energy harvesters
摘要： Flexoelectricity may be an excellent candidate for piezoelectricity in micro and nano scaled energy harvesters due to its strong size dependency. In this paper, a size dependent analytical model of the cantilever-based functionally graded flexoelectric energy harvesters is developed. The Hamilton’s principle is used to derive the governing equations. By means of the Galerkin’s method, the approximated closed-form solutions of electrical output and energy conversion efficiency are obtained. For the functionally graded flexoelectric energy harvester, the effective flexoelectric response is controlled by not only the flexocoupling coefficient but also its first derivative. Numerical results of a 3μm-thick Polyvinylidene Fluoride/ Strontium Titanate composed functionally graded flexoelectric energy harvester demonstrate that when the volume fraction exponent varies from zero to infinity, the optimal working frequency gradually reduces from 41407Hz to 7761Hz and the optimal load resistance gradually increases from 0.99MΩ to 83.91 MΩ. Meanwhile, shrinking the thickness from 3μm to 0.3μm will highly increase the normalized power density and the energy conversion efficiency about one and two orders, respectively. Moreover, when the strain gradient elastic coefficient becomes larger, the natural frequency will increase while the corresponding maximum electrical output will decrease.
关键词： Functionally graded materials,Flexoelectric effect,Cantilever beam,Strain gradient elastic effect,Energy harvesters
更新于2025-09-23 15:22:29
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Flexoelectricity in Monolayer Transition Metal Dichalcogenides
摘要： Flexoelectricity, the coupling effect of the strain gradient and charge polarization, is an important route to tune electronic properties of low-dimensional materials. Here our extensive first-principles calculations reveal that structural wrinkling and corrugation will cause significant flexoelectricity in transition metal dichalcogenide (TMD) monolayers. The flexoelectricity is induced by the strain gradients created along the finite thickness of the wrinkled TMD monolayers and becomes more dominant in determining out-of-plane polarizations with decreasing wavelengths of the TMD wrinkles. According to the first-principles calculations and whole structural symmetry, a theoretical model is developed to describe the total out-of-plane polarizations and flexoelectric effect of the wrinkled TMD monolayers. The unveiled flexoelectricity in monolayer TMDs highlights a potential for their application in energy conversion devices.
关键词： energy conversion,monolayer,strain gradient,flexoelectricity,polarization,transition metal dichalcogenides
更新于2025-09-23 15:21:21
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Size-dependent instability of organic solar cell resting on Winkler-Pasternak elastic foundation based on the modified strain gradient theory
摘要： The present study employs the modified strain gradient theory (MSGT) in conjunction with the refined shear deformation plate theory to explore the buckling behaviour of simply supported and clamped OSC. The Winkler-Pasternak elastic foundation is implemented to idealise the foundation. The size-dependent effect of the OSC is captured by the three length scale parameters within the MSGT. The Hamilton principle is used to derive the equations of motion and the boundary conditions, and the Galerkin procedure is subsequently implemented to obtain the critical buckling load. Subsequently, the framework is extended to the thermally induced buckling behaviour, and three types of temperature rise patterns, namely uniform, linear and nonlinear temperature variations, along the thickness of the OSC are considered. Several verification studies are conducted to illustrate the accuracy of the present method. Besides, size-dependent material properties are taken into consideration during the numerical experiments. Thorough studies are conducted to demonstrate the difference between critical buckling loads and temperature variations obtained from the MSGT, the modified couple stress theory (MCST), and the classical plate theory (CPT) models. Furthermore, the effects of length scale parameter (hl), the aspect ratio (ab), the length-to-thickness ratio (ah) and the Winkler-Pasternak elastic foundation parameters on the buckling behaviour of the OSC are also revealed by the numerical results.
关键词： Refined shear deformation plate theory,Strain gradient elasticity theory,Thermal buckling,Organic solar cell,Mechanical buckling,Elastic foundation
更新于2025-09-12 10:27:22
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Static bending and free vibration of organic solar cell resting on Winkler-Pasternak elastic foundation through the modified strain gradient theory
摘要： Organic solar cell (OSC), which is deemed to be the most promising third generation solar energy application, is developing vigorously. Based on the modified strain gradient theory (MSGT) and the refined shear deformation plate theory, static bending and free vibration of the size-dependent OSC are thoroughly investigated in this paper. A Winkler-Pasternak elastic foundation is considered for the OSC. A multiscale suitable plate analysis framework (i.e., both macro- and micro plates can be handled) is developed herein. Three length scale parameters are incorporated in the presented analysis to capture the size-dependency of the OSC. By setting two or three of them into zero, the presented model could degenerate into the modified couple stress theory (MCST) and the classical plate theory (CPT). The derivation of the governing equations and the corresponding boundary conditions are conducted by Hamilton principle. The Navier-type solution is employed for solving the governing equations of the simply supported OSC. The accuracy of the presented method is validated. Extensive numerical experiments have been conducted to investigate the differences between the adopted MSGT, the MCST and the CPT. Moreover, the impacts of the geometrical configuration as well as the elastic foundation parameters on the static bending and free vibration characteristics are illustrated in the numerical studies. This paper also explores the thickness of the active layer effect on the free vibration behaviour in combination with the power conversion efficiency (PCE) of the OSC.
关键词： Structural analysis,Modified strain gradient theory,Organic solar cell
更新于2025-09-11 14:15:04
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Effects of end-on oriented polymer chains at the donor/acceptor interface in organic solar cells
摘要： The transport and magnetic properties of LaAlO3/SrTiO3 (LAO/STO) heterostructure have been studied during cooling and warming. The strain gradient perpendicular to the surface of the heterostructure increases with the thickness of LAO film. The conductivity accelerated recoveries (CAR) are found at 80 K and 176 K in the interface of LAO/STO sample with millimeter scale, and are more obvious for thicker LAO layers during warming. These two recovering temperatures correspond to the migrating energies of oxygen single vacancy and divacancy trapped by polarized domain walls, separately. This indicated that domain walls diffuse along the longitudinal direction and expand to larger area due the strain gradient perpendicular to the interface. The stable and precise accelerating recovering temperatures make the sample at a larger scale a potential widely applied temperature standard reference. The magnetization measurements reveal the coexistence of paramagnetic and diamagnetic in the LAO/STO samples at whole temperature from 2 K to 300 K. The abnormal electric resistance rise is observed with the decreasing temperature below 25 K for the samples of 7 and 15 LAO layers. This anomaly is attributed to the Kondo effect below 25 K and weak anti-localization below 5 K due to the weightier paramagnetic content. The larger diamagnetic content suppresses these contributions in 25 LAO layers sample. This work provided an insightful view that the strain modified structure domain leads to the enhancement of CAR effect, which helps to achieve a better understanding of domain related physics in the LAO/STO system.
关键词： magnetization,LaAlO3/SrTiO3 heterostructure,conductivity accelerated recoveries,domain walls,weak anti-localization,strain gradient,Kondo effect
更新于2025-09-11 14:15:04