查看更多>>摘要：The two-dimensional thermoelectric coupling conduction problem of an inhomogeneity, which is characterized by a Laurent polynomial and embedded in a thermoelectric material subjected to uniform electric current density or uniform energy flux at infinity, is studied under the conditions of the electrical insulation and thermal conduction continuity. While the complex potential denoting the electric field has a compact form, the complex potential indicating the temperature field can be treated as a boundary value problem of analytic function. Then, an iterative strategy is developed to solve the series solution of the temperature fields inside and outside the inhomogeneity, expressed by Faber polynomials and their associated polynomials. Finally, the non-uniform temperature fields for the inhomogeneities shaped elliptic and polygonal shapes are carried out in a series form. After the convergence is guaranteed, the results are analyzed to show that the inhomogeneities with different shape characteristics exhibit different effects on the temperature distribution, and the temperature perturbation increase on the boundary is primarily determined by the relative thermal conductivity of the matrix to the inhomogeneity. The maximum curvature can be used to determine the severity of the maximum temperature perturbation on the boundary of inhomogeneities with the same area.
查看更多>>摘要：Partial contacts between faces are common in cracks. They produce strong stiffening effect, even if they are small. The cross-property connection implies that they produce a similar effect on the crack resistivity contributions. These effects lead to a substantial reduction of the "effective" crack density that controls the overall properties. The present work analyzes these issues in a systematic way, as functions of contact distributions. In particular, the effects of contact density and clustering are examined. The paper contains a critical review of the earlier works as well as new results.
查看更多>>摘要：In this paper, three-dimensional (3D) dynamic analysis of a rotational smart piezomagnetic-flexomagnetic (PFM) multi-functional micro-disk has been investigated. In the mathematical modeling, an attempt has been made to develop a wide range of factors influencing the analyzed structure, which is intended to be used as a micro-sensor/actuator. The investigated smart microdisk could have many sensitive and accurate applications, especially in the aerospace industry. The geometry is assumed to be an annular microscale structure. Flexomagnetic property, observable on the small scale, has been considered for the material of the analyzed disk, and is one of the principal factors influencing the present research. Due to the angular rotation of the annular micro-disk, it is possible to control the sensing process in delicate conditions, particularly in environments influenced by microgravity. A comprehensive dynamic simulation is performed according to the 3D elasticity, then the governing equations of the smart micro-disk are extracted using the energy method. The effect of several parameters on the numerical results has been thoroughly examined. The deformation results, based on the piezo-flexomagnetic effect of the analyzed structure, have been obtained, enabling the design of precise sensors/actuators for advanced technological applications. The presented theoretical model offers a suitable approach for extending experimental tasks. It should be noted that the equations presented in this paper are original and can serve as a benchmark reference in this field. In conclusion, we found that there is a direct link between the rotational speed of the micro-disk and the surrounding magnetic field, and high angular velocities can impede the influence of the magnetic-induced mechanical load.
Daniel PeckGaspare Da FiesIvan VirshyloGennady Mishuris...
104237.1-104237.21页
查看更多>>摘要：This paper investigates hydraulic fracture in a medium with periodic heterogeneous toughness. Results for the plane-strain (KGD) model are analysed. The energy distribution as the fracture propagates is examined, along with the evolution of the crack geometry. It is shown that the solid layer acts as an elastic battery, discharging to promote rapid propagation through weaker material layers. The limiting case of an infinite-length crack is discussed. The velocity of the fluid throughout the crack length is also considered. For fractures in high-toughness material it is shown that fluid backflow can occur, with its profile dependent on the toughness distribution. The implications of these findings are discussed.
查看更多>>摘要：Critical remarks on the paper "Analytical Solutions and Case Studies on Stress-Dependent Corrosion in Pressurized Spherical Vessels" published in Metals, 2023, vol. 13, are given. They concern serious errors in treating the problem, as well as incorrect treatment of works of other authors - in particular, article published in the International Journal of Engineering Science. Due to practical importance of the topic, these errors and inconsistencies need to be exposed.
查看更多>>摘要：A plane strain problem for a partially electrically conducting and partially insulated crack in a homogeneous piezoelectric material is considered. The electrically conducting zone is located either on both crack faces or on one of them. Remote mechanical tensile stresses orthogonal to the crack and the electric field orthogonal or parallel to the crack are applied. The appearance of contact zones between the crack faces is supposed. The computational model is based on the finite element method. Determination of the energy release rates at the crack tips is realized using the virtual crack closure technique. The results of solving a number of test problems are presented. They demonstrate the satisfactory accuracy of the model. The impact on the fracture parameters of such factors as the length and location of conducting zone, the direction of the electric field, and the poling direction of the piezoelectric material is analyzed.
查看更多>>摘要：This paper explores the influence of microstructures on the effective thermal expansion coefficient of thermal metamaterials, highlighting the surface-induced size-dependent effects. These effects stem from the unique porous microstructural characteristics, influenced by volume fraction and geometric configuration. Unlike nanoscale phonon-driven surface effects, comprehensive finite element numerical simulations reveal that macroscopic surface mechanisms in thermal metamaterials arise from changes in heat conduction pathways due to microstructural features. These surface regions, characterized by an intrinsic length, are determined by the microstructure itself. To accurately capture the complex size-dependent coefficients of linear thermal expansion, we developed a surface-oriented homogenization method that leverages the interaction between extrinsic and intrinsic length under surface mechanisms. Unlike classical homogenization methods, this approach does not require compliance with the principle of scale separation. The effectiveness of this surface-oriented homogenization method is demonstrated through simulations of thermal metamaterial sheet subjected to temperature variations, highlighting that this method combines the efficiency of traditional homogenization methods with the high accuracy of high-fidelity finite element methods. This paper not only provides a novel surface-oriented homogenization approach that can overcome computational challenges of thermal metamaterial structures but also offers an approach to constructing an offline dataset for the intrinsic length that is beneficial to guiding the data-driven design of thermal metamaterial structures.
查看更多>>摘要：This study, for the first time, investigates the bulk waves in mechanical metamaterial thickness-and shear-deformable doubly-curved shells; it considers spherical, elliptical, hyperbolic, and cylindrical shell structures. A third-order shear deformable model, involving thickness deformation, is employed to capture in-surface and out-of-surface, rotational, and stretching motions within a curvilinear coordinate system. Equations of motion are obtained via Hamilton's principle, resulting in a set of coupled partial differential equations. A genetic programming-based micromechanics method for mechanical properties has been developed in the literature recently; this paper uses it as simulation inputs. A harmonic approach is used to solve these equations and to obtain the circular frequency. For the spherical, elliptical, hyperbolic, and cylindrical shells, influences of the curvatures on the wave frequency are highlighted. In the Appendix, a comparative analysis for a simplified case (excluding metamaterial effects, and multilayer configurations) demonstrates very good agreement with prior studies.
查看更多>>摘要：Novel layered soft electroactive materials/structures have various special functions and features which can be uniquely applied to different modern science and engineering fields. In this paper, three-dimensional full-field solutions for the indentation characterization of layered soft electroactive media are presented by using a newly established semi-analytical approach. This approach is based on the integration of the Fourier-Bessel series system of vector functions, the dual-variable and position method and the Green's function. For illustration, the flat-ended indentation of a layered neo-Hookean ideal dielectric half-space, incorporating interfacial imperfections and material inhomogeneity between adjacent layers, is taken as an example. The present method is first verified by comparing with the exact solution for a reduced homogeneous case and then applied to multi-layered half-spaces with varying interfacial conditions, ranging from the frictionless contact case to the perfectly bonded case, and with linearly/exponentially graded shear moduli within the layers. The effects of the material compressibility and the interfacial imperfections on the full-field responses are investigated through one-layer and two-layer half-space models, respectively. The imperfections are found to play as barriers in the propagation of indentation-induced distortion within the layered structure. The comparison between the incremental von Mises stress for 20-layer and 100-layer half-spaces further highlights the positive significance of increasing layers to prevent stress mismatches in such structures. Most interestingly, with the advantage of much lower cost on fabrication, the layered structure with sufficient layers is quantitively demonstrated to achieve desired performance comparable to the continuously graded one. We believe that the present study not only establishes a good reference for characterizing the properties of soft multi-field coupled materials/structures containing material inhomogeneity and/or imperfections but also provides a benchmark pattern for addressing related complex boundary-value problems.
查看更多>>摘要：In this paper, the thermodynamics of granular material is developed to get constitutive relations for unified modelling of undrained viscoplastic flow behavior with complex combined effects of state, rate, time, and path. The proposed formulations of energy storages and dissipations lead to the state-dependent hyperelasticity with an elastic instable region and the viscoplasticity with considerations of the granular kinetic flow. Subjected to strict thermodynamic restraints, a generalized law of viscoplastic shear flow is proposed for granular material as the combination of state-based and rate-based viscoplastic flows, which predictively captures the diversity of undrained granular flow pattern with elastic-plastic coupled non-coaxialities among stresses, (total/ viscoplastic/elastic) strains, and their increments. The viscoplastic flow is also linked with the granular temperature that accounts for the granular kinetic fluctuation varying from dilative dense flow to large unlimited flow under shear-induced static liquefaction. This enables predictions of the creep and the stress relaxation as well as the over- and -under shooting of stress under stepwise changes in strain rate. The model is well validated by predicting the flow potential, phase transformation, critical state, and rate/time effects under undrained conventional triaxial shearing and simple shearing for Toyoura sand, which are strongly related to the void ratio, the confining pressure, the shear stress, and the shear mode.
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