Shape Of Inclusions Research Articles

Dislocation Generation by Microparticle Inclusions

Microscopic inclusions are common sources of dislocations in solution-grown crystals, but the correspondence between the size and shape of inclusions and the probability of dislocation generation h...

Influence of inclusions on hydrogen-induced delayed cracking in hot stamping steels

The hydrogen-induced delayed cracking (HIDC) behaviors of two types of 1500 MPa grade hot stamping steels (HSSs) have been investigated by the method of slow strain rate tensile test and hydrogen permeation, where one is manufactured by compact strip production (CSP) process which is a revolution to the traditional HSS and the other by the traditional cold rolling process. The results show that the performance of HSS produced by CSP is superior to that of the traditional HSS, due to lower hydrogen embrittlement index, lower hydrogen diffusion coefficient and lower hydrogen content. It has been found that HIDC behavior is closely associated with inclusions. The inclusions of HSS produced by CSP are mainly spherical Al–Ca–O and CaS, while the inclusions in the traditional HSS are TiN + Al2O3 + MnS with sharp edges and corners. Based on these results, the influence of composition, shape and distribution of inclusions in HSS on HIDC and the mechanism of HIDC from the perspective of inclusions were analyzed and discussed.

Numerical Modeling of PZT- Piezoelectric Composites with Passive and Active Polymer Matrix

Piezoelectric composite materials with a polymer matrix are important for underwater acoustic and biomedical imaging applications. The dependence of electromechanical properties of piezoelectric composite on constituent material characteristics and shape of piezoelectric inclusions is a central problem that provides the opportunity to tailor the performance of piezoelectric composites according to design needs. A numerical model has been developed to investigate the electromechanical properties of 1-3 piezoelectric composites with a passive and active polymer matrix. Maxwell Homogenization method is employed to homogenize the solution domain. It is demonstrated that the use of PVDF as an active polymer matrix has a significant influence on piezoelectric charge coefficient d31, hydrostatic coefficient dh, voltage coefficient gh, and hydrophone figure of merit ghdh when compared to the passive Araldite-D polymer matrix. Overall, a 5 to 30% volume fraction of PZT-7A fiber inclusions in an active polymer matrix is the optimum ratio that has a significant effect on piezoelectric properties. The accuracy and effectiveness of homogenized material constants were verified by comparing the derived composite properties with experimental work published elsewhere. These results provide much needed intuitiveness in the development of piezoelectric polymer composite with better performance for transducer applications.

Novel and efficient simulation approach for effective permeabilities of randomly ordered two-phase compounds

Abstract This paper introduces a novel simulation approach for the magnetic properties of two-phase randomly ordered compounds. In industry, materials such as ferrous powder mixtures or metallic granulates are very often used as raw materials. Hence, their material characteristics are of utmost interest for material manufacturers in order to guarantee high quality standards. Typically, many parameters such as composition, inclusion shape, and the characteristics of the constituents affect the macroscopic physical behavior of such materials. In particular, the resulting permeability of multi-phase and randomly ordered materials exhibits a strong variation despite constant compounds. For the design and optimization of measurement setups, efficient simulators are necessary to estimate the effective permeability and its fluctuation range of a huge number of arrangements. In addition to the basic concept of the novel simulation method, this article presents some possible evaluations of the simulated results and their dependencies on the properties of the constituents. In the last century, a large number of different mixing formulas have been established in literature, which are summarized and compared to the simulation results. Finally, the simulated magnetic characteristics are evaluated with finite element simulation of a comparable particle arrangement.

Determination of Brinkman Model Parameters Using Stokes Flow Model

The two key parameters of the Brinkman’s model for fluid flow in porous media—permeability and effective viscosity—are determined theoretically. The analytical solution of a 1D problem for the Brinkman equation for the fluid flow in a porous medium between two solid walls is compared with results of the numerical Stokes fully resolved flow model in a two-dimensional periodic cells containing solid inclusions. The boundary value problem for the Stokes flow is solved using the boundary element method. The dependencies of the permeability and effective viscosity on porosity for various types of configurations and shapes of solid inclusions are numerically studied. The product of permeability and effective viscosity is introduced as a new parameter. It is shown that this parameter is almost constant for a wide range of values of porosity excluding the small interval close to the unity value. The analytical estimation confirms the numerically obtained values of the parameter. The obtained dependencies are verified by the solution of the 2D Brinkman flow problem. It is shown that the permeability and effective viscosity determined give good agreement between the pressure fields and flow streamlines of the exact solution of the two-dimensional Brinkman equation and the numerical solution of the Stokes equations. The approximations for the dependencies of permeability and effective viscosity on the porosity are constructed on the basis of the numerical data obtained. The applicability of the Brinkman and Darcy models is discussed.

Energy and volume changes due to the formation of a circular inhomogeneity in a residual deviatoric stress field

An inclusion of purely dilatational eigenstrain in an infinitely extended isotropic elastic matrix, independently of its shape, causes a deviatoric stress field around it. The present paper analyses the energy and volume changes due to the formation of a circular inhomogeneity in a deviatoric stress field coming from a circular inclusion of dilatational eigenstrain. It is found that the elastic stress inside the inhomogeneity remains deviatoric and the inhomogeneity formation does not change the volume of the inclusion-matrix system; it is argued that the same occurs for any inclusion shape and non-uniform eigenstrain. The elastic energy changes occurring in the domains occupied by matrix, inhomogeneity, and inclusion are calculated, and its dependence on the elastic properties and geometrical parameters of inhomogeneity and matrix is numerically investigated. Strengthening effects of the matrix-inhomogeneity system are examined by means of the energy force and expanding moment acting on the inhomogeneity.

Effects of metal silicide inclusion interface and shape on thermal transport in silicon nanocomposites

While various silicon nanocomposites with their low thermal conductivity have received much attention for thermoelectric applications, the effects of inclusion interface and shape on thermal transport remain unclear. Here, we investigate thermal transport properties of silicon nanocomposites, in which metal silicide inclusions are periodically arranged within silicon. Using the known phonon dispersion relations and the diffuse mismatch model, we explore the effects of different silicide-silicon interfaces, and using Monte Carlo ray tracing simulations, we explore the effects of silicide inclusion shapes. Our investigations show that the thermal conductivity of silicon nanocomposites can be reduced to the range of nanoporous silicon of the same geometry, depending on the interface density, crystal orientation, and acoustic mismatch. For instance, CoSi2 inclusions of [111] orientation can reduce the nanocomposite thermal conductivity more effectively than inclusion materials with lower intrinsic thermal conductivity, such as NiSi2, when the inclusion density is up to 12.5% with an interface density of 7.5 μm−1. Among the silicide inclusion materials investigated in this work, Mn4Si7 leads to the lowest nanocomposite thermal conductivity due to a combination of low intrinsic thermal conductivity and high acoustic mismatch. Compared to widely spaced and symmetric inclusions such as a circular shape, narrowly spaced and asymmetric inclusions such as a triangular shape are more effective in limiting the phonon mean free path and reducing the nanocomposite thermal conductivity. These findings regarding thermal transport in silicon nanocomposites with respect to inclusion interface and shape will guide optimal material designs for thermoelectric cooling and power generation.

The use of technogenic dispersed waste engineering to obtain compact forms of graphite in the materials of the system Fe-C-Al

Currently, the significant problem of domestic engineering is to improve the quality level of products based on efficient resource-saving technologies. In the paper the main emphasis has been placed on using in such a significant procurement industry of engineering, which is foundry, dispersed iron-containing with a different degree of oxidation of the designated waste element. Moreover, this use of waste is proposed to carry out both at the stage of preparation of the melt for blanks, and in the manufacture of a mold. We are talking about blanks of materials based on the system Fe-C-Al, the quality of which is largely determined by the shape of graphite inclusions.

Analysis of three-dimensional ellipsoidal inclusions in thermoelectric solids

ABSTRACT Thermoelectric (TE) materials as energy functional semiconductors can directly convert heat into electrical power. Due to the brittle nature of semiconductors, voids or inclusions are easy to be produced in the TE materials. This paper studies the three-dimensional ellipsoidal inclusion problem in thermoelectric materials. By introducing two auxiliary functions, we successfully simplify the non-linear coupled governing equations into linear un-coupled equations and the linearization is validated by two practical cases. Based on the Green's function method, the analytical solutions of this problem are derived. We find that the thermoelectric field inside the ellipsoidal inclusion is always uniform when subjected to far-field uniform loads. Furthermore, we derive the effective material properties of the matrix-inclusion system in closed-form. We find that it is possible to enhance the thermoelectric properties as well as the figure of merit by inserting specific inclusions. Moreover, among the different shapes of inclusions, the elliptical cylinder fiber that lies along the loading direction has the most significant improvements to the material properties. This paper is the first that derives the analytical solutions of three-dimensional inclusion problems in TE materials.

Reflection shifts in a graphene-coated dielectric–metal composite of non-spherical particles

Using effective medium theory, spatial and angular Goos–Hanchen and Imbert–Fedorov reflection shifts of a graphene-coated granular substrate composed of non-spherical gold nanoparticles in a dielectric host are investigated. The numerical results indicate that the composite substrate can play a role in tunability of shifts similar to that of an electrically-controlled graphene layer does. It is realized that both shape and volume fraction of granular inclusions can bring about a broad shift modulation. This may provide applications in nano-optics as well as in characterizing the parameters of the composite.

A new approach for electro-elastic analysis of piezoelectric fiber composites with arbitrary shaped inclusions under anti-plane shear and in-plane electric loadings

Electro-elastic analysis of piezoelectric fiber composites with arbitrary shaped inclusions subjected to far field uniform anti-plane shear and in-plane electric loadings is performed in this study in order to increase the electromechanical performance and protect the vulnerable piezoelectric inclusion from electromechanical damage. A three-phase model with a representative volume element of piezoelectric fiber composites with arbitrary shaped inclusions is proposed based on the generalized self-consistent theory. Meanwhile, a new conformal mapping method based on Cauchy integral and series expansion is also proposed to map an arbitrary two-connected domain into an annular domain. Both of the electro-elastic responses and the effective moduli of the piezoelectric fiber composites with arbitrary shaped inclusions for the anti-plane problem are obtained using the complex potentials in series form and the homogenization strategy. Comparisons with literature show a good agreement. Additionally, the effects of the fiber shape and the fiber volume fraction on the normal shear stress and the tangential electric field distributions outside the piezoelectric fiber, and the effective moduli are investigated using the proposed model and method. It is shown that the normal shear stresses and the tangential electric fields outside piezoelectric fiber have intense fluctuations at the corner of the inclusion. Both of the electro-elastic responses and the effective moduli of piezoelectric fiber composites become larger as the shape of piezoelectric inclusion sharpens and the fiber volume fraction increases. Furthermore, the proposed model and method can be used for determining the appropriate shape and volume fraction of the piezoelectric inclusion to significantly reduce stress and electric field concentrations around the inclusion and optimize the electromechanical performance of piezoelectric fiber composites.

Effective elastic isotropic moduli of highly filled particulate composites with arbitrarily shaped inhomogeneities

The purpose of present work is three-fold: (i) to model thin binding interphases within highly filled particulate composites (HFPCs) as equivalent spring-type interfaces of zero-thickness; (ii) to develop a computational approach for calculating the effective elastic moduli of HFPCs containing arbitrarily shaped inhomogeneities; (iii) to establish a numerical scheme which generates simplified models for substitution of real representative volume elements of HFPCs while ensuring linear isotropic elasticity at the macroscopic scale. At first, a spring-type interface model with explicit physical background is derived to replace the soft interphases in HFPCs, and the macroscopic quantities and effective moduli accounting for the interfacial discontinuities are reformulated. Then, the strong and weak formulations of the boundary value problems of HFPCs are constructed, and a computational approach is developed by using the extended finite element and level set methods so as to determine the effective moduli of HFPCs. A numerical procedure is further elaborated to generate macroscopically isotropic RVEs by dividing a cubic model into differently shaped subdomains, and the minimal number of cutting planes is obtained based on the necessary and sufficient conditions in He (2004). Finally, discussions are made on the inclusion size and shape effects on the overall isotropic moduli of HFPCs.

Compositions Based on Nanosized Powders Carbides of Tungsten and Titanium, Obtained by the Method Self-Propagating High Temperature Synthesis for the Modification of Gray Cast Iron and Steel 110g13L

Iron-based alloys (steel and cast iron) are currently the main structural materials that provide a high level of mechanical and technological properties along with a relatively low cost. Increasing the performance characteristics (tensile strength, hardness, wear resistance, corrosion resistance and, ultimately, service life) of cast irons and steels is an urgent task. The quality of castings made of cast iron and steel depends on many technological parameters that affect the processes of crystallization of the melt (casting temperature, molding mixture, chemical composition, volume of casting, overheating of the metal during smelting, etc.). It is possible to improve the quality of castings without changing the technology of smelting and pouring metal into molds, if you learn how to manage the crystallization process. The laboratories have grown defect – free iron crystals with a tensile strength of more than 1000 kg/m2 (strength of carbon steel-40 kg/m2). Attempts to improve the mechanical properties by creating a single crystal are not justified, so you have to go the opposite way-to influence the crystallization process to get a lot of small crystals (grains), which also allows you to achieve high mechanical properties. The dependence of the strength characteristics on the grain size is well described by the law of Hall-Petch, according to which when the average grain size is reduced by 3...5 times there is an increase in the hardness of the material, with a further decrease in the average grain size by more than 10 times – an increase in plasticity. Influence on the processes of crystallization of iron and steel melts (change the size of metal grains, change the shape, size and distribution of graphite inclusions) can be the introduction of small additives substances (modifiers), not chemically interacting with the matrix. The use of modifiers to increase the rate of crystallization, reduce the structural heterogeneity of castings has good prospects. In addition, unlike doping, modification does not require a large number of expensive additives and, accordingly, slightly increases the final cost of production.

An Experimentally Trained Noise Filtration Method of Optical Coherence Tomography Signals

A method for wavelet filtration procedure training for optical coherence tomography (OCT) images using the experimental measurements of test objects that were constructed by means of water solutions of monodisperse nanoparticles and several microscopic inclusions has been described in the present paper. The choice of test-object parameters (concentration of water solution, size of nanoparticles, and shape, dimensions, and mutual position of inclusions) has allowed the modeling of various working conditions of OCT and setting different criteria for estimation of filtration efficiency. In the present work, the optimal filter for the considered example of a test object has been selected among the combinations of various basic functions of five wavelet families, soft and hard threshold filtering methods, four decomposition levels, and threshold values in a range of 0.05–3.05. The mutual position of the micro-inclusions has been used as a criterion for evaluating the filtration efficiency. As a result, it has been shown that the determined wavelet filter leads to effective suppression of the scattering noise in OCT images and preserve information about the structure of the object under study.

Tailoring the thermal and mechanical properties of lightweight cement-based composites by macro and micro fillers

Design and fabrication of high-strength and low-thermal-conducting cement-based materials are urgently needed for developing low-energy-consuming buildings. Here glass bead (GB) and ground expanded perlite (EP) particles were respectively used as the macro and micro insulating fillers to synthesize thermally insulating cement-based composites (C-GB-EP). The material structures, mechanical and thermal properties of the C-GB-EP composites were investigated by comprehensive experimental tests. Results indicate that both fillers have no obvious influences on cement hydration, but accelerate the carbonation of calcium hydroxide due to the loosely compacted microstructures. The C-GB-EP composites show complex and multi-scaled material structures dominated by the interactions between the fillers and matrices in different scales. The C-GB-EP composites retain their mechanical properties in the limited EP contents. The C-GB-EP composites show relatively low thermal conductivities and very high thermal-resistant abilities with respect to compressive strength and density. A multi-scale micromechanical model was proposed to predict the effective thermal conductivity of the composites. Inclusion shapes play an important role on depressing the thermal conductivity of composites. Incorporation of penny-shaped insulating inclusions in cement matrix may be an appropriate and effective way to design new types of thermally insulating cement-based composites.

Band gaps for flexural elastic wave propagation in periodic composite plate structures based on a non-classical Mindlin plate model incorporating microstructure and surface energy effects

A new model for determining band gaps for flexural elastic wave propagation in periodic composite plate structures containing square and cruciform inclusions is developed using a non-classical Mindlin plate model incorporating the microstructure and surface energy effects. The new model reduces to the classical elasticity-based counterpart when both the microstructure and surface energy effects are not considered. The plane wave expansion method and the Bloch theorem for periodic media are used in the formulation. The band gaps predicted by the newly developed model depend on the microstructure and surface elasticity of each constituent material, the unit cell size, and the volume fraction. To quantitatively illustrate the effects of these factors, a parametric study is conducted. The numerical results reveal that the microstructure and surface energy effects on the band gaps are significant only when the plate thickness is small. In addition, it is found that the first band gap size decreases with the increase of the unit cell length according to both the current non-classical and classical models. Moreover, it is seen that the volume fraction has a significant effect on the first band gap size, and large band gaps can be obtained by tailoring the volume fraction and inclusion shape.

Control of MnS Inclusions in High- and Low-Sulfur Steel by Tellurium Treatment.

Manganese sulfide (MnS) inclusion in steel is related to the machinability of steel. Controlling the type and shape of MnS inclusion has been a problem for the steelmaking process for a long time. The effect of tellurium (Te) treatment on the control of MnS inclusion is studied with experiments and discussion of sequential solidification. The result shows that Te addition to the high- and low-sulfur steel dominantly changes the size and shape of MnS inclusions in steel. The aspect ratio of inclusions in cast steel changes with Te/S ranges from 0 to 1.9, which offers an effective way to control the MnS type and thus to improve the machinability and mechanical properties of steel. With an excessive Te addition, no further improvement could be observed by scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS).

Effect of processing at the steel vacuum processing unit (SVPU) on desulfurization of unmodified and modified KP-2 steel

The object of the research is the processes of statistical processing of the chemical composition of KP-2 wheel steel. One of the most problematic places in the smelting of modern steel is the stability of the chemical composition due to the use of uncontrolled content of scrap, charge and standard modifiers, which are made by the fused method. To eliminate this problem, multifunctional modifiers were used during the study. This is due to the fact that the KP-2 steel modification method proposed in this article has a number of features. In this case, the influence modifiers of multifunctional action on the installation of vacuum processing of steel on desulfurization of wheel steel KP-2, obtained under the conditions of the open joint-stock company «Interpipe NTRP» (Dnipro, Ukraine), is established. In particular, when treating a steel melt with multifunctional modifiers, not only a refining effect occurs, but also an increase in the stability of the chemical composition and level of mechanical characteristics of the KP-2 wheeled steel. This is confirmed by the coefficients of variation and interfusion difference presented in the article (span), obtained by statistical processing of a large data set – 442 serial heats and 1 modified (6 wheels). Thanks to the multifunctional modification, the level of mechanical characteristics and the quality of the finished wheels really increases. Compared with similar mass-produced materials, such as FeSi, FeCa, FeMn, SiCa, the use of new multifunctional modifiers in KP-2 wheel steel provides a significant reduction in the mass fraction of sulfur than in the same metal that is processed in the traditional way. It is established that the use of multifunctional modifiers changes the shape of non-metallic inclusions to globular and reduces their number, which also increases the level of mechanical properties of KP-2 wheel steel. The obtained coefficients of variation prove that the mechanical characteristics of KP-2 modified steel are more stable than in serial melts of the same steel. This will increase the demand and quality of these railway wheels.

Influence of the inclusion shape on the effective elastic properties of composites

The elastic properties of composites are mainly determined by the characteristics of reinforcing inclusions. This work addresses the dependence of the elastic properties of inclusion-reinforced composites on the inclusion shape. Specifically, ball-shaped, spherical and cubic inclusions are considered.

A Robust Inclusion Boundary Reconstructor for Electrical Impedance Tomography With Geometric Constraints

As a nondestructive, nonradioactive, and high temporal resolution technique, electrical impedance tomography (EIT) has potential applications in industrial and biomedical imaging. A novel geometrically constrained boundary reconstructor (GCBR) is presented for EIT. It can directly calculate the boundary of the target inclusions embedded into a homogeneous background conductivity and is robust to noise. The proposed GCBR depends on a specially designed energy function, which consists of the residual term and the geometric constraints’ term. The residual term drives the estimated inclusion boundary to the targets. The geometric constraints’ term regularizes the estimations and automatically excludes the meaningless boundary guesses from the candidate solution. A set of numerical tests are conducted to discuss the key factors influencing the boundary reconstruction performance. A set of experimental tests are conducted to evaluate the performance of the proposed GCBR. The position, size, and shape of the target inclusions are well reconstructed from the real data. The mean position error and mean Hausdorff distances between the target and reconstructed boundaries are 0.39% and 2.2% of the maximal observation diameter, respectively. The mean area errors and the mean area of the symmetric difference between the target and reconstructed inclusion regions are 0.32% and 2.54% of the total observation area, respectively.