Transient Thermal Stress Problem of a Functionally Graded Magneto-Electro-Thermoelastic Hollow Sphere.
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ABSTRACT: This article is concerned with the theoretical analysis of the functionally graded magneto-electro-thermoelastic hollow sphere due to uniform surface heating. We analyze the transient thermoelastic problem for a functionally graded hollow sphere constructed of the spherical isotropic and linear magneto-electro-thermoelastic materials using a laminated composite mode as one of theoretical approximation in the spherically symmetric state. As an illustration, we carry out numerical calculations for a functionally graded hollow sphere constructed of piezoelectric and magnetostrictive materials and examine the behaviors in the transient state. The effects of the nonhomogeneity of material on the stresses, electric potential, and magnetic potential are investigated.
Project description:The optimal distribution of the reinforcing fibers for stiffening hollow cylindrical composites is explored using the linear elasticity theory. The spatial distribution of the vascular bundles in wild bamboo, a nature-designed functionally graded material, is the basis for the design. Our results suggest that wild bamboos maximize their flexural rigidity by optimally regulating the radial gradation of their vascular bundle distribution. This fact provides us with a plant-mimetic design principle that enables the realization of high-stiffness and lightweight cylindrical composites.
Project description:This paper presents a closed-form solution for the arbitrary polygonal inclusion problem with polynomial eigenstrains of arbitrary order in an anisotropic magneto-electro-elastic full plane. The additional displacements or eigendisplacements, instead of the eigenstrains, are assumed to be a polynomial with general terms of order M+N. By virtue of the extended Stroh formulism, the induced fields are expressed in terms of a group of basic functions which involve boundary integrals of the inclusion domain. For the special case of polygonal inclusions, the boundary integrals are carried out explicitly, and their averages over the inclusion are also obtained. The induced fields under quadratic eigenstrains are mostly analysed in terms of figures and tables, as well as those under the linear and cubic eigenstrains. The connection between the present solution and the solution via the Green's function method is established and numerically verified. The singularity at the vertices of the arbitrary polygon is further analysed via the basic functions. The general solution and the numerical results for the constant, linear, quadratic and cubic eigenstrains presented in this paper enable us to investigate the features of the inclusion and inhomogeneity problem concerning polynomial eigenstrains in semiconductors and advanced composites, while the results can further serve as benchmarks for future analyses of Eshelby's inclusion problem.
Project description:In this work, the problem of a curved functionally graded piezoelectric (FGP) actuator with sandwich structure under electrical and thermal loads is investigated. The middle layer in the sandwich structure is functionally graded with the piezoelectric coefficient g31 varying continuously along the radial direction of the curved actuator. Based on the theory of linear piezoelectricity, analytical solutions are obtained by using Airy stress function to examine the effects of material gradient and heat conduction on the performance of the curved actuator. It is found that the material gradient and thermal load have significant influence on the electroelastic fields and the mechanical response of the curved FGP actuator. Without the sacrifice of actuation deflection, smaller internal stresses are generated by using the sandwich actuator with functionally graded piezoelectric layer instead of the conventional bimorph actuator. This work is very helpful for the design and application of curved piezoelectric actuators under thermal environment.
Project description:This study offers a comprehensive investigation into the parameters affecting the sound transmission characteristics of a double-walled sandwich magneto-electro-elastic cross-ply layered plate resting on viscoelastic medium in thermal environment. To this end, the walls of this sandwich structure are modeled based on the assumptions of the first-order shear deformation theory. The governing equations are derived via a coupled set of equations targeting vibration and acoustic aspects of the problem after the application of Hamilton’s principle. The obtained equations are then solved by the implementation of double Fourier series and the second velocity potential, giving an accurate estimation of sound transmission loss under initial magnetic and electric potentials, variations of temperature, ply angle, acoustic cavity depth, incident angle of sound waves, and viscoelastic parameters.
Project description:A peridynamic (PD) model of functionally graded materials (FGMs) is presented to simulate transient heat conduction in the FGM plate with insulated cracks. The surface correction is considered in the model to reduce the surface effect near the domain boundary and insulated cracks. In order to verify the proposed model, a numerical example for the FGM plate is carried out. The results show good agreement with the analytical solution. The convergence of the model with the surface correction for FGMs without cracks is then investigated. The results reveal that our model converges to the classical solutions in the limit of the horizon going to zero. The effects of two material points discretization schemes on the accuracy of numerical results are investigated. For transient heat conduction of FGMs with a static crack, the results obtained from the proposed PD model agree well with that from the finite element method. Finally, transient heat conduction of the FGM plate with a dynamic horizontal crack and intersecting cracks is simulated and discussed.
Project description:This work demonstrates a simple microfluidic device to synthesize a magneto-thermochromic sphere with Janus inner structure. The Janus sphere is composed of Fe3O4 microspheres, thermochromic particles, and polyacrylamide matrix. Because the Fe3O4 microspheres are assembled together in one pole, the Janus sphere can turn around by varying the direction of the external magnetic field. Originating from the temperature-dependent property of the thermochromic particles, the final Janus sphere can change its color from red to pale blue when the temperature is increased from 5 to 45 °C. The detailed formation process and the magneto-thermochromic mechanism are carefully investigated. Due to the magnetic switch and thermochromism, these Janus spheres can be applied as colorful displays by controlling the magnetic field and temperature. The results demonstrate that the dual responsive Janus spheres possess broad application potential in temperature sensors and displays.
Project description:Radiofrequency ablation has been used to treat low-risk thyroid cancer; however, its oncological safety remains unclear. We applied transient sublethal thermal stress to thyroid cancer cells to simulate clinical scenarios in which incomplete radiofrequency ablation leads to residual viable thyroid cancer cells.
Project description:The control of ion trans-membrane transport through graphene oxide (GO) membranes is achieved by electric and magnetic fields. Electric field can either increase or decrease the ion transport through GO membranes depending on its direction, and magnetic field can enhance the ion penetration monotonically. When electric field is applied across GO membrane, excellent control of ion fluidic flows can be done. With the magnetic field, the effective anchoring of ions is demonstrated but the modulation of the ion flowing directions does not occur. The mechanism of the electro- and magneto-modulated ion trans-membrane transport is investigated, indicating that the electric fields dominate the ion migration process while the magnetic fields tune the structure of nanocapillaries within GO membranes. Results also show that the ion selectivity of GO membranes can be tuned with the electric fields while the transport of ions can be enhanced synchronously with the magnetic fields. These excellent properties make GO membranes promising in areas such as field-induced mass transport control and membrane separation.
Project description:The palette of tools for perturbation of neural activity is continually expanding. On the forefront of this expansion is magnetogenetics, where ion channels are genetically engineered to be closely coupled to the iron-storage protein ferritin. Initial reports on magnetogenetics have sparked a vigorous debate on the plausibility of physical mechanisms of ion channel activation by means of external magnetic fields. The criticism leveled against magnetogenetics as being physically implausible is based on the specific assumptions about the magnetic spin configurations of iron in ferritin. I consider here a wider range of possible spin configurations of iron in ferritin and the consequences these might have in magnetogenetics. I propose several new magneto-mechanical and magneto-thermal mechanisms of ion channel activation that may clarify some of the mysteries that presently challenge our understanding of the reported biological experiments. Finally, I present some additional puzzles that will require further theoretical and experimental investigation.
Project description:Hollow microspheres with high specific surface area are widely used in thermal insulation, drug delivery and sustained release, catalysis and optical absorption. Eutectic gallium-indium (EGaIn) undergoes phase transformation and oxidation when heated in aqueous solution, which can provide a crystal seed and preferential growth environment for nanomaterials. Therefore, it is very promising to further study the application of liquid metal in functional and structural nanomaterials. In this study, a EGaIn-based ice cream-shaped hollow sphere array with nanostructures was firstly synthesized on the designed hole array model using a hydrothermal process, and then the surface was further modified by fluorination to form a superhydrophobic film. Different sizes of the hollow Eutectic gallium-indium zinc oxide (EGaIn-ZnO) microspheres could be easily achieved by varying the size of the model, hence leading to controllable wettability. Furthermore, hollow microspheres hold much air, making it feasible for application in the field of anti-ice and thermal insulation.