International Journal of Engineering Science最新文献

Structural schemes of applicative interests in Engineering Science frequently encounter the intricate phenomenon of discontinuity. The present study intends to address the discontinuity in the flexure of elastic nanobeam by adopting an abstract variational scheme. The mixture unified gradient theory of elasticity is invoked to realize the size-effects at the ultra-small scale. The consistent form of the interface conditions, stemming from the established stationary variational principle, is meticulously set forth. The boundary-value problem of equilibrium is properly closed and the analytical solution of the transverse displacement field of the elastic nanobeam is addressed. As an alternative approach, the eigenfunction expansion method is also utilized to scrutinize the efficacy of the presented variational formulation in tackling the flexure of elastic nanobeams with discontinuity. The flexural characteristic of mixture unified gradient beams with diverse kinematic constraints is numerically illustrated and thoroughly discussed. The anticipated nanoscopic features of the characteristic length-scale parameters are confirmed. The demonstrated numerical results can advantageously serve as a benchmark for the analysis and design of pioneering ultra-sensitive nano-sensors. The established variationally consistent size-dependent framework paves the way ahead in nanomechanics and inspires further research contributing to fracture mechanics of ultra-small scale elastic beams.

There has been tremendous recent interest in Direct Air Capture (DAC) systems. A key part of any DAC system are the multiple air intake units. In particular, the arrangement of such units for optimal capture and sequestration is critical. Accordingly, this work develops an easy to use model for a modular unit system, where an approximate flow field is computed for each unit and the aggregate flow field is developed by summing the fields from each unit. This allows for a modular framework that can be used for rapid simulation and design of an overall DAC system. The rapid rate at which these simulations can be completed enables the ability to explore inverse problems seeking to determine which parameter combinations can deliver the maximum sequestration of tracer plume particles for the minimum amount of energy input. In order to cast the objective mathematically, we set up an inverse as a Machine Learning Algorithm (MLA); specifically a Genetic MLA (G-MLA) variant, which is well-suited for nonconvex optimization. Numerical examples are provided to illustrate the framework.

Nanocomposites can show different properties according to the type of reinforcements they have. In this article, a model for the study of nanocomposites is examined, which is able to examine all nanocomposites with elliptical, cylindrical, spherical and rectangular reinforcements. Also, in this model, unlike some other models, the effects of interphase section are included. The results obtained from this model are compared with the results of experimental tests. Also, in present research, instead of classical continuum theories, generalized continuum mechanics is used and combined with above model to present more accurate model for studying nanocomposites. After estimating the material properties of nanocomposites, the static and dynamics behaviors of them are also studied and the influences of various parameters such as volume fraction of interphase section, geometrical shapes of reinforcements, volume fraction of fibers, gradient parameter, nonlocality and magnetic field are investigated on the results.

The drying phenomenon in soils involves complex interactions between thermal, hydrological, and mechanical effects within a multiphase system. While several researches (both mechanics and mixture theory approach) has been applied to study various thermo-hydro-mechanical (THM) coupled processes in porous media, incorporating both multiphase flow and phase change in soil drying remains limited. This work addresses this research gap by deriving new governing equations for a two-phase flow model suitable for soil drying by extending the mixture coupling approach. The derived model is implemented in COMSOL Multiphysics and validated against experimental data, demonstrating good agreement between the model predictions and the ob- served results. A sensitivity analysis is performed to investigate the impact of critical parameters on the drying process. The findings reveal that volumetric strain is most sensitive to Young’s modulus, while the saturation of liquid water is most affected by intrinsic permeability. Additionally, preliminary results for a kaolinite clay sample during the drying process are presented, extending the applicability of the derived model to specific soil types. This research provides a comprehensive framework for fully THM coupled modelling of soil drying, which can serve as a basis for future investigations.

The paper proposes a transparent and compact form of constitutive and equilibrium relations for the plane thermoelasticity of quasicrystal solids. The symmetry and positive definiteness of the obtained extended tensors of material constants are studied. An extension of the Stroh formalism is proposed for solving plane problems of thermoelasticity for quasicrystals. It is proved that the eigenvalues of the Stroh eigenvalue problem in the most general case of 3D quasicrystal materials do are purely complex. The relations between the matrices and vectors of phonon–phason elastic and thermoelastic coefficients of the proposed extended Stroh formalism are obtained. A fundamental solution to the plane problem of thermoelasticity of a quasicrystal medium is derived. The asymptotic behavior of physical and mechanical fields near the vertices of objects whose geometry can be modeled by a discontinuity line (cracks, thin inclusions) is studied, and the concepts of the corresponding generalized field (heat flux and phonon–phason stress) intensity factors are introduced. Examples of the influence of heat sources and sinks on an infinite quasicrystal medium containing a rectilinear heated crack are considered.

Estimation of macroscopic properties of heterogeneous materials has always posed significant problems. Procedures based on numerical homogenization, although very flexible, consume a lot of time and computing power. Thus, many attempts have been made to develop analytical models that could provide robust and computationally efficient tools for this purpose. The goal of this paper is to develop a reliable analytical approach to finding the effective elastic–plastic response of metal matrix composites (MMC) and porous metals (PM) with a predefined particle or void distribution, as well as to examine the anisotropy induced by regular inhomogeneity arrangements. The proposed framework is based on the idea of Molinari & El Mouden (1996) to improve classical mean-field models of thermoelastic media by taking into account the interactions between each pair of inhomogeneities within the material volume, known as a cluster model. Both elastic and elasto-plastic regimes are examined. A new extension of the original formulation, aimed to account for the non-linear plastic regime, is performed with the use of the modified tangent linearization of the metal matrix constitutive law. The model uses the second stress moment to track the accumulated plastic strain in the matrix. In the examples, arrangements of spherical inhomogeneities in three Bravais lattices of cubic symmetry (Regular Cubic, Body-Centered Cubic and Face-Centered Cubic) are considered for two basic material scenarios: “hard-in-soft” (MMC) and “soft-in-hard” (PM). As a means of verification, the results of micromechanical mean-field modeling are compared with those of numerical homogenization performed using the Finite Element Method (FEM). In the elastic regime, a comparison is also made with several other micromechanical models dedicated to periodic composites. Within both regimes, the results obtained by the cluster model are qualitatively and quantitatively consistent with FEM calculations, especially for volume fractions of inclusions up to 40%.

Micromechanical modelling of particulate composites with non-ellipsoidal particle shapes presents significant challenges because analytical approaches based on the fundamental results of Eshelby cannot be used. On the other side, direct numerical evaluations by finite element analysis can involve high computational cost in the case when particle features have small radius of curvature, sharp edges and require extremely fine meshes. This paper proposes substituting the exact particle shape with a surrogate model producing approximately the same contribution to the effective elastic moduli. We illustrate our approach by considering rotationally symmetric 3D particle shapes with the external surface defined by the Laplace's spherical harmonics. In this case, spherical layered surrogates offer good accuracy of approximation, especially when the material parameters of each layer are determined by the particle swarm optimization algorithm. The proposed approach is presented by considering several highly undulated particle shapes and comparing the surrogate model results with direct finite element simulations of the original microstructure.

A new scaling theory called finite similitude has appeared in the open literature for the scaling of physical systems. The theory is founded on the metaphysical concept of space scaling and consequently can in principle be applied to all physics. With regard to the application of the theory to multi-physics however, an obstacle is dissimilar mathematical formulations, that are preferred and applied in practice. This paper looks to combine electrical and mechanical physics under the rules of the scaling theory for the analysis of scaled electromechanical systems. To facilitate this the physics of electromechanics is described using transport equations on a projected space termed the scaling space. It is shown that this approach unifies the mechanical and electrical descriptions and allows the scaling theory to be applied and for scaling identities to be established. Additionally, on confirming that the scaling space possesses all the attributes of a real physical space (despite being a mere projection), mathematical modelling (to great advantage) is performed directly and integrated with the scaling theory. To showcase the concepts, mathematical models for previously researched electromechanical systems are directly analysed in the new scaling space. It is demonstrated how such models automatically account for scale dependencies in the electromechanical systems they represent. The huge potential of the new approach is revealed providing the means for formulating (for the first time) realistic representative scaled-mathematical models.

Although auxetic metamaterials exhibit unique and unusual mechanical properties, such as a negative Poisson's ratio, their mechanics remains poorly understood. In this study, we model a graded beam fabricated from graphene origami-enabled auxetic metamaterials and investigate its dynamics from the perspective of different shear deformation theories. The auxetic metamaterial beam is composed of multiple layers of graphene origami-enabled auxetic metamaterials, where the content of graphene origami varies through the layered thickness; both the auxetic property and other properties are varied in a graded manner, which are effectively be approximated via micromechanical models. The Euler-Bernoulli, third-order, and higher-order shear deformable refined beam theories are adopted to model the auxetic metamaterial beam as a continuous system. Following this, the governing motion equations are derived using the Hamiltonian principle and then are numerically solved using a weighted residual method. The obtained results provide a comprehensive understanding of how graphene origami content and its distribution pattern, graphene folding degree, and the utilisation of different shear deformation theories influence the dynamic behaviour of the beam.

We propose a weak form of the transient heat equations for solid bodies, as a time-dependent spatial variation of the heat displacement vector field, whose time derivative is the heat flux. This develops the variational principle originally proposed by Biot, inasmuch Fourier’s law is embedded as a holonomic constraint, while energy conservation results from the variation (the vice-versa from Biot). This is a neat formulation because only the heat displacement appears in the variational equations, whereas Biot’s form also involved the unknown temperature field: Fourier’s law is used only a posteriori to recover the temperature. Since the heat displacement is generally more regular than the temperature field, it represents a natural variable in problems with material inhomogeneities, uneven radiation, thermal shocks. The three-dimensional analytical set-up is presented in comparison with Biot’s, for boundary conditions accounting for radiation and convection. A mechanical analogy with the equilibrium of an elastic bar with viscous constraints is suggested for the one-dimensional case. The variational equations are implemented in a finite element code. Numerical experiments on benchmark problems, involving high temperature gradients, confirm the efficiency of the proposed approach in many structural problems.