Shape Of Inclusions Research Articles

Effect of inclusion on contact damage evolution of wind turbine gears based on configurational force theory

The gear box of wind turbine is subjected to the complex environment such as random wind load for a long time, and the gear contact fatigue becomes a key factor limiting the stability and reliability of wind turbine equipment. Therefore, the research on the gear contact damage evolution mechanism is faced with difficulties such as complex stress states, damage anisotropy and failure modeling. However, traditional fracture mechanics and damage mechanics are limited in predicting the failure load of complex defects and evaluating the structural integrity. Material configurational force theory can describe the effect of defect configurational change on the free energy of materials and be used to predict the damage and failure behavior of materials. In this paper, a wind turbine gear contact damage model is constructed based on this theory. The gear contact interface stress field simulation analysis is carried out for the key bearing area of gear contact, and the gear contact damage evolution process under contact load is simulated. For the problem of gear failure caused by metal oxide inclusion, the damage evolution model based on Jk parameters is established. The damage evolution process of gear containing inclusions under contact loading is simulated numerically, and the influence of depth, shape and location of inclusions on the damage evolution behavior is analyzed. The research results have shown that the configurational force theory damage model can effectively simulate the contact damage phenomenon of gear and explain the pitting and spalling of gear surfaces. It has theoretical significance to predict contact fatigue life of gear accurately.

The Influence of Financial Inclusion and Financial Technology on the Intention to Use Online Loans: Financial Behavior as an Intervening Variable

This study investigates the influence of financial inclusion and financial technology (fintech) on the intention to use online loans, with financial behavior acting as an intervening variable. In light of the increasing popularity of online loans and the concerns around consumer financial behavior, the research explores how enhanced access to financial services and fintech platforms impacts users' financial decisions. Using a quantitative design, the study collected data from 150 teachers in Malang Regency through questionnaires and applied path analysis using SPSS 23 to examine the relationships between variables. The results indicate that financial inclusion and fintech significantly improve financial behavior, which, in turn, positively affects the intention to use online loans. The study’s novelty lies in its identification of financial behavior as a key mediator, offering a new model to explain how financial inclusion and fintech shape online loan usage. The findings are particularly valuable for policymakers aiming to improve fintech regulation, platform providers looking to enhance consumer engagement, and educators focusing on financial literacy programs.

Fine‐Tuning of Elastic Properties by Modifying Ordering of Parallel Nanolayer Inclusions in Hard Sphere Crystals

It is known that changes on the microscopic, structural level of materials exert changes on their macroscopic properties, in particular elastic ones. This approach can be used to alter the elastic properties of materials. However, it is not easy to predict the impact of a particular change in the structure of crystals. The recent studies show that depending on the size, shape, and orientation of inclusions used, the resulting elastic properties may differ. Inclusions may enhance, weaken, or eliminate the auxetic properties in a hard sphere model. This study is focused on the influence of the spatial distribution of planar inclusions within the hard sphere crystal and its impact on its elastic properties. Periodic systems containing two nanolayer inclusions in the representative volume element, oriented orthogonally to ‐direction and in various spatial ordering, are considered. It has been shown that introducing layer inclusions causes the deterioration of auxetic properties in the ‐direction. However, the latter weakly depends on the spatial ordering of the inclusion layers. Moreover, changes in the size of the inclusion particles, combined with different ordering of the inclusion layers, can be used to coarsely and finely tune the elastic properties of the model crystal.

Effects of the inclusion shape, arrangement, and volume fraction on effective elastic moduli of two-dimensional two-phase composites

The spatial arrangement and shape of inclusions can have a major impact on two-phase composites' mechanical properties. Few studies consider the coupling effects of these two factors on the effective elastic moduli of two-phase composites. This study introduces the circularity of inclusions to modify the three-point approximation (TPA) for quantitatively predicting the coupling effects of inclusion planar arrangement and shape. Two-dimensional particle packing structures of monosized particles are generated with polygons, superellipses, and superovals of different circularities and volume fractions via the ordered arrangement approach or the discrete element method. Then, the lattice model is conducted on the particle packing structures to verify the reliability of the modified TPA. The comparison between the theoretical calculation and the numerical simulation indicates that our modified TPA can predict the effects of planar arrangement, shape, and volume fraction of inclusions on the effective moduli. The proposed modified TPA offers fresh perspectives on comprehending intricate relationships between the macro-property and composition of composites.

Anisotropic induced polarization modeling with neural networks and effective medium theory

Interpreting three-dimensional induced polarization (IP) data requires rock physics models that reflect the omnipresent anisotropy of the Earth’s crust. The Generalized Effective Medium Theory of Induced Polarization (GEMTIP) can model the IP signatures of rocks with polarizable mineral inclusions. However, it is computationally demanding because it requires numerically solving the depolarization tensors of each inclusion. We aim to streamline GEMTIP simulations by (1) integrating anisotropic background conductivity and triaxial ellipsoidal inclusions in the model and (2) estimating the depolarization tensors with a neural network. We validate the neural network predictions against known solutions for spherical and spheroidal inclusions, and we test our method using data from an actual rock sample. The neural network shows a relative sensitivity of 56% to inclusion shape and 44% to host rock anisotropy and is up to 100,000 times faster than numerical integration. We release the pre-trained neural network implementation as an open-source Python package, thereby providing a new method to interpret the IP signatures of anisotropic rocks.

Preliminary Study on Multi-Scale Modeling of Asphalt Materials: Evaluation of Material Behavior through an RVE-Based Approach

This study employs a microstructure-based finite element modeling approach to understand the mechanical behavior of asphalt mixtures across different length scales. Specifically, this work aims to develop a multi-scale modeling approach employing representative volume elements (RVEs) of optimal size; this is a key issue in asphalt modeling for high-fidelity fracture modeling of heterogeneous asphalt mixtures. To determine the optimal RVE size, a convergence analysis of homogenized elastic properties is conducted using two types of RVEs, one made with polydisperse spherical inclusions, and another made with polydisperse truncated cylindrical inclusions, each aligned with the American Association of State Highway and Transportation Official’s maximum density gradation curve for a 12.5 mm Nominal Maximum Aggregate Size (NMAS). The minimum RVE lengths for this NMAS were found to be in the range of 32–34 mm. After the optimal RVE size for each inclusion shape is obtained, computational models of heterogeneous Indirect Tensile Asphalt Cracking Test samples are then generated. These models include the components of viscoelastic mastic, linear elastic aggregates, and cohesive zone modeling to simulate the rate-dependent failure evolution from micro- to macro-cracking. Examination of load-displacement responses at multiple loading rates shows that both heterogeneous models replicate experimentally measured data satisfactorily. Through micro- and macro-level analyses, this study enhances our understanding of the composition-performance relationships in asphalt pavement materials. The procedure proposed in this study allows us to identify the optimal RVE sizes that preserve computational efficiency without significantly compromising their ability to capture the asphalt material behavior under specific operational conditions.

Phase-field modelings of fracture investigate the influence of interfacial effects on damage and optimal material distribution in brittle inclusion-matrix structures

This present work uses the phase-field modelings to investigate the influence of interfacial effects on damage and mechanical behavior, as well as the optimal distribution of the inclusion shape within brittle inclusion-matrix structures in various typical cases. These two constituent phases in the structures are assumed to be either isotropic or anisotropic. To achieve these goals, this work will: (i) use the phase-field modelings either considering or neglecting interfacial debonding, and the anisotropic phase-field modeling; (ii) determine and incorporate the strain tensor orthogonal decompositions into each specific phase-field modeling to enhance the accuracy and effectiveness of the simulation methods; (iii) combine the phase-field modelings with the BESO topology optimization algorithm to analyze the influence of interfacial effects on relationship curves and the optimal distribution of the inclusion shape. Through proposed numerical examples, it is demonstrated that the interfacial effects strongly influence crack paths, behavior curves, and optimal material distribution in structures. When considering interfacial effects, cracks are almost unable to penetrate into the inclusion phase. However, when neglecting interfacial effects, cracks propagate into the inclusion phase. This reason makes the structure more difficult to damage than when considering the interfacial effects, as evidenced by greater peak load values in behavior curves and greater total fracture resistance of the material. Especially in the example of inclusion phase optimization, the total fracture resistance value of the case neglecting interfacial effects is more than 107.9% greater than that considering interfacial effects.

Working with constructs of inclusion for understanding teachers’ literacy practices and their impact on student learning

ABSTRACT The paper explores teachers’ language literacy practices in underprivileged, inner-city schools in Athens, Greece, and their implications for student learning and educational inclusion. The current developments of global/European and national education policy agendas on literacy and inclusion inform the research questions of the study. Bernstein’s theory of pedagogic discourse frames our analysis on the reproduction of social inequalities through schooling and informs our discussion on the discursive means and the pedagogic practices for their interruption. Findings, based on interview data and classroom observations, indicate that global discourses on inclusion, (re)articulated in the disadvantaged school settings of the study, invest the notion of inclusion with three different meanings: a. inclusion as assimilation and absorption into the dominant culture and society; b. inclusion as therapy for students’ emotional ‘traumas’; and c. inclusion as recognition of difference. We argue that these constructs of inclusion shape teaching practices that either promote or undermine student learning and empowerment.

FE modeling to generate composite RVEs with high volume fractions and various shapes of inclusions

This work proposes a novel multi-step dynamic FE compression method to generate Representative Volume Elements (RVEs) of composites containing a variety of inclusions. This method is actualized through a sequential and four-stage procedure: (1) Sparse and periodic inclusions exhibiting a predefined orientation distribution are generated by implementing a modified random sequential adsorption algorithm, (2) Sparse inclusions undergo biaxial compression into the region of the targeted RVE via a dynamic FE analysis, (3) Periodic inclusions are compressed into the region utilizing a dynamic FE analysis with periodic boundary conditions, and (4) Positions and orientations of the compressed inclusions are extracted and the RVE in computer-aided design format is then generated. The proposed method confers advantages from four distinct perspectives: (1) applicability to various inclusion geometries, including ellipses, lobules, polygons, kidneys and stars, (2) ability to generate periodic RVEs of composites with high inclusion volume fractions (up to 80.0% for circular inclusions), (3) simple and straightforward numerical implementation without explicitly considering inclusion intersection check and (4) capacity to predefine inclusion orientation distribution. Statistical analyses utilizing multiple spatial descriptors, i.e., inclusion orientation angle, local volume fraction, Voronoi cell area, nearest-neighbor distance and orientation, second order intensity function, radial distribution function and two-point probability function, confirm randomness of inclusion distribution in the generated RVEs. The elastic properties and damage behaviors of composites via the FE homogenization method are predicted based on the generated RVEs and are compared with those of available experimental data, the literature and the mean-field homogenization models to demonstrate effectiveness of the proposed multi-step dynamic FE compression method.

Fast Fourier transform method in peridynamic micromechanics of composites

We consider a static linear bond–based peridynamic (proposed by Silling, see J. Mech. Phys. Solids 2000; 48:175–209) composite materials (CMs) of a periodic structure. In the framework of the second background of micromechanics (also called computational analytical micromechanics), one proved that local micromechanics (LM) and peridynamic micromechanics (PM) are formally analogous to each other for CM of both random and periodic structures. It allows a straightforward generalization of LM methods (including fast Fourier transform, FFT) to their PM counterparts. So, in the PM counterpart of the implicit periodic Lippmann–Schwinger (L-S) equation in LM, we have three convolution kernels corresponding to the properties of the matrix, inclusions, and interactive interface. Eshelby tensor in LM, depending on the inclusion shape, is replaced by PM counterparts depending on the shapes of inclusions, and the interaction interface (although the Eshelby concept of homogeneous eigenfields does not work in PM). The mentioned tensors are estimated once (as in LM) in a frequency domain (also by the FFT method). The possible incorrectness of FFT applications to PM is analyzed and corrected. The polarization schemes of the solution of the L-S equation in the Fourier space have one primary unknown variable (polarization), whereas the PM counterpart contains three primary ones estimated at each step, which are formally similar to the LM case. A description of the generalized basic scheme and the Krylov approach is presented. Computational complexities O(N log2 N) of the FFT methods are the same in both LM and PM.

Study of fractality nature in VO2 films and its influence on metal-insulator phase transition

The mechanisms underlying the origin of fractal shape of inclusions of a new phase in VO2 films during metal-insulator phase transition are discussed. The obtained results show that hysteresis of the temperature dependence of resistance R(T) significantly depends on the film morphology and texture. Moreover, some fractal features are observed. To determine the fractal dimension D of the structural elements of the studied films from their images, different fractal analysis approaches were preliminary compared and discussed. As a result of the film image treatments, the boundaries of the structural elements were found to have fractal dimensions of 1.3 to 1.5 or higher and to correlate with the shape of R(T). The fractal boundaries indicate the dominant role of elastic stress on the phase transition of films, which is confirmed by numerical modeling. Based on these results, an analytical model is proposed that relates the free energy of a film to the fractal dimension of its constituents. Depending on the ratio of the elastic and interface specific energies, the position of the free energy minimum F corresponds to a certain fractal dimensionality D. A small interface energy leads to a higher fractal dimension making the initial phase more stable. This conclusion explains well all the effects observed experimentally in VO2. The obtained results provide a better understanding of the influence of structure and morphology on other properties of the studied films.

The structure and shape of graphite inclusions in cast iron, affecting the durability of molds. Part 4

The structure and shape of graphite inclusions in cast iron, affecting the durability of molds. Part 4

Enhancing solar panel cooling efficiency: a study on the influence of nanofluid inclusion and pin fin shape during melting and freezing of phase change materials

The present article presents a 3D simulation of a solar thermal panel containing phase change materials (PCMs). Two pipes are devised in the panel, and several pin fins (PFs) are applied to each pipe. Organic PCMs are encapsulated in a compartment around the PFs and pipes. The variable is PF shape, which includes four types, i.e., square, rectangular, triangular, and circular. Nanofluid (NFD) is used within the pipes. The study is carried out transiently and continued until the stabilization of outlets. Utilizing an FEM method based on a weak form, namely, Galerkin, to find a numerical solution for mathematical modeling. The artificial intelligent results indicate that using triangular, square, rectangular, and circular PFs provides the highest NFD temperature in the outlet, respectively. Circular PFs lead to a lower heat transfer coefficient (HC) compared to other PFs. The comparison between various PF shapes shows that the use of circular and triangular PFs results in the lowest and highest panel temperature, respectively. Moreover, the highest and lowest volume fraction of melting PCMs around the pipe is obtained through the use of triangular and circular PFs, respectively.

Extended Darcy–Forchheimer law including inertial flow deflection effects

Recent advances in manufacturing techniques are providing porous media with both high permeability, necessary for effective passive flow control, and high structural strength, essential for engineering applications. We therefore examine the predictive accuracy of the standard Darcy–Forchheimer (DF) law, which is often used to model porous media flows, for inclusion Reynolds numbers (Re) ranging from the low linear regime to the high nonlinear regime where unsteady effects such as vortex shedding become evident. We consider two different inclusion shapes, square and circular, and three different arrangements of the inclusions – inline, staggered and random. The numerical simulations show that the DF law performs well for low-Re flows, irrespective of the inclusion configuration. For intermediate/high-Re flows, the DF law is adequate only when the arrangement is highly random. However, for the regularly arranged topologies or less random geometries at intermediate/high-Re flows, the DF-law performance diminishes significantly due to flow sheltering and redirection (‘inertial flow deflection’) effects that arise from flow inertia, separation and vortex shedding in the wake of the inclusions. It is shown that the standard DF law, in which the nonlinear permeability tensor is independent of orientation, does not capture such effects. We modified the DF law to capture flow redirection effects by allowing the Forchheimer permeability tensor to depend on the flow orientation with respect to the principal geometrical directions of the porous geometry, and examined this extended DF law for these flows.

FAST FOURIER TRANSFORM METHOD FOR PERIDYNAMIC BAR OF PERIODIC STRUCTURE

The basic feature of the peridynamics [introduced by Silling (2000)] considered is a continuum description of material behavior as the integrated nonlocal force interactions between infinitesimal material points. A heterogeneous bar of the periodic structure of constituents with peridynamic mechanical properties is analyzed. One introduces the volumetric periodic boundary conditions (PBCs) at the interaction boundary of a representative unit cell (UC), whose local limit implies the known locally elastic PBCs. This permits us to generalize the classical computational homogenization approach to its counterpart in peridynamic micromechanics (PM). Alternative to the finite element methods (FEM) for solving computational homogenization problems are the fast Fourier transforms (FFTs) methods developed in local micromechanics (LM). The Lippmann-Schwinger (L-S) equation-based approach of the FFT method in the LM is generalized to the PM counterpart. Instead of one convolution kernel in the L-S equation, we use three convolution kernels corresponding to the properties of the matrix, inclusions, and interaction interface. The Eshelby tensor in LM depending on the inclusion shape is replaced by PM counterparts depending on the inclusion size and interaction interface (although the Eshelby concept of homogeneous eigenfields does no work in PM). The mentioned tensors are estimated one time (as in LM) in a frequency domain (also by the FFT method). Numerical examples for 1-D peridynamic inhomogeneous bar are considered. Computational complexities O (N <i>log</i><sub>2</sub> N) of the FFT methods are the same in both LM and PM.

Using enzymatic synthesis of hydroxyapatite as a technique to develop materials for biomedical applications

Composite materials based on gels and hydroxyapatite could provide promising characteristics for biomedical materials because of biocompatibility, osteointegration, and easy implementation. In this research, enzymatic synthesis of hydroxyapatite was studied as a technique for tissue engineering and scaffolds creation. The hydroxyapatite crystals were synthesized using this method and characterized with X-ray diffraction, electron microscopy, IR and Raman spectroscopy and analytical methods. As a result, a material with assumed composition of Ca10−x(HPO4)x(PO4)6−x(OH)2−x/CaHPO4/CaCO3 was obtained by enzymatic synthesis. The dynamics of size evolution, texture and crystallinity of the solid phase as a function of deposition time were also investigated. Afterwards, this method was used for gel mineralization with hydrogels such as agarose, alginate, gelatin, and polyacrylamide. Hydroxyapatite crystals obtained inside and above the hydrogels were analyzed with X-ray diffraction and electron microscopy. The particle diameter distribution functions were used to evaluate the mineralization in different gels. The shape and size of mineral inclusions depend on the density of the hydrogel grid. The localization of the formed solid phase depends on the nature of the gel and the concentration of alkaline phosphatase inside it. The results provide an opportunity to control the morphology of calcium phosphate particles produced during mineralization, which is important for the creation of biomedical materials with specified and reproducible characteristics.

Evolution of cross-sectional shapes of liquid inclusions enclosed in a crystal: Computer simulation and its application for studying interface kinetics

The previously developed model of the cross-sectional stationary shape of a liquid inclusion migrating through a non-uniformly heated crystal has been extended to the case of transient processes caused by changes in the temperature gradient value and/or temperature oscillations. On the basis of computer simulations, the evolution of the cross-sectional shapes of the inclusions with 4 facets in their cross sections has been analyzed for the cases of different mechanisms of interfacial processes. A technique for estimating kinetic coefficients from the geometry of the inclusion shapes established after imposing and removing the temperature gradient has been proposed. The possibility of controlling the velocity and shape of the 4-faceted inclusions by means of temperature oscillations has been demonstrated and discussed.

A finite element-convolutional neural network model (FE-CNN) for stress field analysis around arbitrary inclusions

This study presents a data-driven finite element-machine learning surrogate model for predicting the end-to-end full-field stress distribution and stress concentration around an arbitrary-shaped inclusion. This is important because the model’s capacity to handle large datasets, consider variations in size and shape, and accurately replicate stress fields makes it a valuable tool for studying how inclusion characteristics affect material performance. An automatized dataset generation method using finite element simulation is proposed, validated, and used for attaining a dataset with one thousand inclusion shapes motivated by experimental observations and their corresponding spatially-varying stress distributions. A U-Net-based convolutional neural network (CNN) is trained using the dataset, and its performance is evaluated through quantitative and qualitative comparisons. The dataset, consisting of these stress data arrays, is directly fed into the CNN model for training and evaluation. This approach bypasses the need for converting the stress data into image format, allowing for a more direct and efficient input representation for the CNN. The model was evaluated through a series of sensitivity analyses, focusing on the impact of dataset size and model resolution on accuracy and performance. The results demonstrated that increasing the dataset size significantly improved the model’s prediction accuracy, as indicated by the correlation values. Additionally, the investigation into the effect of model resolution revealed that higher resolutions led to better stress field predictions and reduced error. Overall, the surrogate model proved effective in accurately predicting the effective stress concentration in inclusions, showcasing its potential in practical applications requiring stress analysis such as structural engineering, material design, failure analysis, and multi-scale modeling.

PATHOMORPHOLOGICAL CHANGES IN THE KIDNEYS AND LIVERS OF RED-EARED SLIDER AFTER PARENTERAL ADMINISTRATION OF CEFTIFUR

Diseases of reptiles and the principles of their treatment are significantly different from the therapy of mammals and birds, which is primarily related to the anatomical and physiological features of representatives of this class of poikilothermic animals. In the complex treatment of infectious diseases of reptiles, a fairly effective antibiotic is ceftifur, which belongs to the third-generation cephalosporins, which are widely used in veterinary medicine.
 To study the effect of cephalosporins on the body of reptiles, a histological and ultra-structural examination of the kidneys and liver of Red-eared slider (Trachemys scripta elegans) was performed, which were administered intramuscularly ceftifur (at a dose of 2.2 mg/kg) every 24 hours.
 Experimental animals were removed from the experiment on the 7th day. Histological sections were made using a sledge microtome and cryostat microtome, stained with hematoxylin and eosin, Sudan III. Electron microscopic research was carried out using an electron microscope PEM-100-01.
 As a result of the histological examination and transmission electron microscopy of the kidneys, dyscirculatory changes were revealed, characterized by the expansion and overflow of blood mainly in venous vessels, desquamation of endothelial cells in the vessel lumen, as well as dystrophic changes in the epithelium of the renal tubules. Structural changes in the epithelium of renal tubules were accompanied by damage to mitochondria, expansion of the tubules of the smooth endoplasmic reticulum and the accumulation of cytosomes, lysosomes, and autophagolysosomes in the cytoplasm. In the liver, a decrease in the density of melanomacrophage complexes was recorded, as well as a decrease in the number and change in the shape of fatty inclusions in the cytoplasm of hepatocytes, decrease in the number of glycogen granules. In necrotized hepatocytes, the nucleus underwent pyknotic changes, the cytoplasmic matrix brightened, and cytoplasmic organelles underwent destruction.

Convergent finite element methods for the perfect conductivity problem with close-to-touching inclusions

Abstract In the perfect conductivity problem (i.e., the conductivity problem with perfectly conducting inclusions), the gradient of the electric field is often very large in a narrow region between two inclusions and blows up as the distance between the inclusions tends to zero. The rigorous error analysis for the computation of such perfect conductivity problems with close-to-touching inclusions of general geometry still remains open in three dimensions. We address this problem by establishing new asymptotic estimates for the second-order partial derivatives of the solution with explicit dependence on the distance $\varepsilon $ between the inclusions, and use the asymptotic estimates to design a class of graded meshes and finite element spaces to solve the perfect conductivity problem with possibly close-to-touching inclusions. In particular, we propose a special finite element basis function that resolves the asymptotic singularity of the solution by making the interpolation error bounded in $W^{1,\infty }$ in a neighborhood of the close-to-touching point, even though the solution itself is blowing up in $W^{1,\infty }$. This is crucial in the error analysis for the numerical approximations. We prove that the proposed method yields optimal-order convergence in the $H^1$ norm, uniformly with respect to the distance $\varepsilon $ between the inclusions, in both two and three dimensions for general convex smooth inclusions, which are possibly close-to-touching. Numerical experiments are presented to support the theoretical analysis and to illustrate the convergence of the proposed method for different shapes of inclusions in both two- and three-dimensional domains.