Parameters Of Cellular Structure Research Articles

Sound transmission loss analysis of novel sandwich plate with star-shaped auxetic cellular cores

A star-shaped auxetic cellular metamaterial with a negative Poisson’s ratio (NPR) was employed in this study to model lightweight sandwich panels, and an analysis of its sound transmission characteristics was conducted. Utilizing the first-order shear deformation theory (FSDT) and the Hamiltonian principle, the free vibration equation for the sandwich plate is derived. Subsequently, leveraging the fluid-structure coupling condition and incorporating the Navier method, the sound transmission loss (STL) is analytically described. The efficacy of the proposed method is validated through numerical analysis and an acoustic insulation experiment using an impedance tube. Based on the theoretical modeling, it is calculated that the sound insulation effect of the star-shaped cellular core exceeds that of the traditional reentrant cellular with NPR. A systematic analysis is subsequently conducted to explore the impact of star-shaped cellular structure parameters on the STL of the sandwich panel. It can be obtained that the increase in core layer thickness leads to a reduction in the first-order resonance frequency of the sandwich panel, but concurrently diminishing its sound insulation performance. The change of the connecting rib length exerts a more considerable influence on the structure’s STL compared to the side rib length. While as the cell wall thickness reduces from 2.0 to 1.0 mm, the average STL of the sandwich plate across the analysis band decreases by 8.43%, from 46.3 to 42.7 dB.

EFFECT OF EGG WHITE PROTEIN AND WATER CONTENT ON THE STABILIZATION MECHANISMS OF NATURAL RUBBER LATEX FOAMS OBTAINED FROM MICROWAVE RADIATION

The global plastic consumption, as one of the paramount concerns of our society, open new paths of investigation in green materials. This study presents our contribution to the field with the obtention of natural rubber latex foams using egg white powder as bio stabilizing agent. The route followed to develop these samples is based on a two‐step process, a previous aeration, followed by microwave dehydration. This synthesis route is greener and eco‐friendlier than conventional ones due to the use of biobased bulk materials, the utilisation of microwave radiation which reduces the energy consumption in comparison with conventional heating methods and the elimination of the vulcanization process typically used when producing latex foams. In this work a deep study of the effect of egg white protein on natural rubber latex foams obtained at three water content levels (i.e. 40, 70, 90 phr) is carried out. The density and cellular structure parameters are measured for the formulations of liquid and solid foams which led to stable final samples in order to comprehend the stabilization mechanisms due to the presence of the egg white and the effect of water content in these systems. With the route developed in this research it has been possible to produce open cell natural rubber latex foams with densities as low as 53 kg/m3 and cell sizes as low as 114 µm.This article is protected by copyright. All rights reserved.

Determination of cell size/structures and mechanical properties of additively manufactured metallic components using X-ray technique

PurposeAdditive manufacturing (AM), a rapidly evolving paradigm, has shown significant advantages over traditional subtractive processing routines by allowing for the custom creation of structural components with enhanced performance. Numerous studies have shown that the technical qualities of AM components are profoundly affected by the discovery of novel metastable substructures in diverse alloys. Therefore, the purpose of this study is to determine the effect of cell structure parameters on its mechanical response.Design/methodology/approachInitially, a methodology was suggested for testing porous materials, focusing on static tensile testing. For a qualitative evaluation of the cellular structures produced, computed tomography (CT) was used. Then, the CT scanner was used to analyze a sample and determine its actual relative density, as well as perform a detailed geometric analysis.FindingsThe experimental research demonstrates that the mechanical properties of a cell’s structure are significantly influenced by its shape during formation. It was also determined that using selective laser melting to produce cell structures with a minimum single-cell size of approximately 2 mm would be the most appropriate method.Research limitations/implicationsFurther studies of cellular structures for testing their static tensile strength are planned for the future. The study will be carried out for a larger number of samples, taking into account a wider range of cellular structure parameters. An important step will also be the verification of the results of the static tensile test using numerical analysis for the model obtained by CT scanning.Originality/valueThe fabrication of metallic parts with different cellular structures is very important with a selective laser melted machine. However, the determination of cell size and structure with mechanical properties is quiet novel in this current investigation.

Quantitative relationships between cellular structure parameters and the elastic modulus of aluminum foam

The accurate prediction of the elastic modulus of aluminum foam is important for the application in high-tech fields, e.g. in aerospace industry. However, the scaling law based on the Gibson-Ashby model did not achieve the precise prediction of elastic modulus, in absence of complex porous structural features. In this study, we extended the scaling law by introducing the topological and morphological parameters into the multivariate equation. The 3D numerical images of aluminum foam specimens were obtained by X-ray tomography method, and the nine structural parameters were calculated and analyzed. The results show that as the porosity increases from 77% to 91%, the highest frequency of sphericity and solid material thickness of the cellular structure remains practically constant, although the distribution of cell size becomes more dispersed. The edges connections and the Inter-Branches Angle (IBA) of aluminum foam remain unchanged for all the specimens. Seven structural parameters were introduced into the extended scaling law to predict the elastic modulus with a higher residual value R2 of 0.932, in contrast to the R2 of 0.702 for the conventional scaling law. Through a stepwise linear regression method, the extended scale method was simplified by removing redundant parameters, and still achieved the elastic modulus predictions with a residual value R2 of 0.929. The remaining structural parameters in the extended scaling law, i.e. relative density, solid material thickness, and sphericity, were supposed to independently influence the elastic modulus, according to the covariance analysis. The three independent parameters offer the possibility to accurately predict and regulate the mechanical properties of aluminum foam.

Regulation Mechanism of the Shock Waves in a Pentamode Lattice-Ring Structure Subjected to Collision

This paper hopes to explore the application potential of pentamode materials in the field of shock protection. Hammer percussion tests revealed that the peak strain of the inner-ring front shock surface of the pentamode lattice-ring structure is 103.9% of that of the inner-ring rear shock surface. According to the simulation results, for a solid ring of equal mass made of the same base material, the ratio mentioned above reaches 3385.7%. Compared with the solid ring of equal mass made of the same base material, the pentamode lattice-ring structure saw a decline of 65.5% in the peak strain of its inner-ring front shock surface. The distribution laws of the group velocity characterizing energy-flow characteristics were discovered by calculating cell dispersion curves in various layers of the pentamode lattice-ring structure. The laws governing the effects of cellular structure parameters on group velocity anisotropy and pentamode characteristic parameters were also revealed. It was found that the deflection angle of the energy-flow vector is positively correlated with group velocity anisotropy and that the effects of pentamode characteristic parameters π and μ on the deflection angle of the energy-flow vector vary greatly in different value ranges. The deflection angle of the energy-flow vector has a decisive effect on the protection performance of the pentamode lattice-ring structure. The conclusions of this study can provide some theoretical support for the shock protection of submarine structures.

Dielectric properties of nucleated erythrocytes as simulated by the double spherical-shell model* *Project supported by the National Natural Science Foundation of China (Grant Nos. 51277099 and 52007087), the Natural Science Foundation of Zhejiang Province, China (Grant Nos. LY20C110001 and LSY19A010002), the Natural Science Foundation of Ningbo City, China (Grant Nos. 2019A610349 and 202003N4116), the Fund from the Educational Commission of

The dielectric properties of nucleated erythrocytes from bullfrogs were measured in a frequency range of 10 kHz–110 MHz. The complex permittivity (ε *), complex conductivity (κ *), and complex resistivity (ρ *) were analyzed and compared in the 10.63% to 37.58% haematocrit (Hct) range. The relaxation behavior, the passive electrical properties, and the cellular structure parameters, including the cell membrane, the cytoplasm, the nuclear membrane, and the nucleoplasm of the nucleated erythrocyte suspensions were investigated. The method used is based on the binomial Cole–Cole equation and the double spherical-shell physical models. Upon the elimination of the electrode polarization effect, two definite relaxations related to the interfacial polarization are observed on low- and high-frequency dispersions. The permittivity values and the characteristic frequency values differ by one order of magnitude: the low-frequency relaxation increments [Δ ε 1 = (5.63 ± 1.43)× 103] and the characteristic frequency [f c1 = (297.06 ± 14.48) kHz] derived from the cell membrane, the high-frequency relaxation increments [Δ ε 2 = (5.21 ± 1.20) × 102] and the characteristic frequency [f c2 = (3.73 ± 0.06) MHz] derived from the dielectric response to the external electric field of the nuclear membrane, respectively. Moreover, the other core dielectric parameters, such as the relative permittivity of the cell membrane [ε m = (7.57 ± 0.38)] and the nuclear envelope [ε ne = (23.59 ± 4.39)], the conductivity of the cytoplasm (hemoglobin, κ Hb = (0.50 ± 0.13) S/m] and the nuclear endoplasm [κ np = (2.56 ± 0.75) S/m], and the capacitance of the bilayer membranes [C m: (0.84 ± 0.04) μF/cm2], and C ne: (0.52 ± 0.10) μF/cm2] were also accurately and reliably measured. This work presents a feasible method to evaluate the dielectric parameters and the cellular structure of the erythrocytes of bullfrogs. Moreover, it paves the way for new studies on the haematology of frogs and the detection of nucleated cells via dielectric impedance spectroscopy.

An experimental method of bioimpedance measurement and analysis for discriminating tissues of fruit or vegetable

It is difficult to apply bioimpedance technique to discriminate plant tissues due to the large variability of Cole parameters. A novel electronic method for characterizing tissue of fruit or vegetable with discrimination capability is presented. A specially designed electrode-pair is used to measure the bioimpedance and Cole parameters are extracted. The relaxation time which is a fundamental property of a given tissue is then estimated and analysis of variance is performed to gain statistical relevance. Bioimpedance is measured for apple and potato tissues in the frequency range of 1 Hz to 1 MHz and rigorous data analyses are performed. With 99% confidence, it is shown than the relaxation time is independent of position of measurement and is specific for a given fruit or vegetable. Further, the tissues of different species of a given fruit (or vegetable) is shown to be discriminated statistically at the confidence level of 98%. An excellent correlation is shown between the bioimpedance parameters and the parameters of cellular structure. Experimental data shows that our technique can be generalized to distinguish unhealthy or treated fruits (or vegetables) and therefore bearing immense applicability in the characterization of plant tissue.

Energy Saving Effect in Conditions of Air Infiltration through External Wall Made of Air-Permeable Materials

The purpose of research consists: in analysing the results, obtained on the development of lightweight ceramic materials with variable cellular structure parameters for efficient control of heat exchange and air permeability processes in external enclosing structures of buildings; in the compilation of the model of economizing effect in such a structures with penetrable porous medium. The features of thixotropy processes of ceramic slurry masses based on natural silicites are investigated. Lightweight ceramics with variable parameters of the cellular structure was obtained by the method of vibra-swelling at a frequency of vibration of the slurry 1200…1500 min−1, the amplitude 3…5 mm, during 3 min. A model is developed, that describes the heat transfer and air-permeability processes in external enclosing structures during the movement of counter current heat flows from the heated room and as an infiltration from the outer surface of the enclosing structure. This model takes into account, that with such an exchange under certain conditions may arise the economizing effect, in which part of the heat flow of the room is transferred to the pores of the material. It is shown, that according to standards of thermal protection of buildings the process of infiltration of cold air is considered as an unfavourable factor, causing the cooling of the structure mass and increasing of heat losses. Calculation model is applied for a limited number of design solutions of external enclosing structures with the material, having penetrable porous medium, that provides its increased air permeability. Based on model of economizing effect in the external wall, the approximate evaluation of the heat economy is given due to the reducing of the inlet cold air and amount of the heat on its temperature rise. As a result of research are developed the light ceramic materials with changeable parameters of cellular structure. This significantly improved the variability of macrostructure parameters, increased the degree of reproducibility of the required technical result and the strength characteristics of the ceramic material. A model is developed, describing the economizing effect, which can arise during the process of air infiltration in external enclosing with a similar material structure. According to the model the economizing effect increases with raising of building height, as well as with decreasing resistance to air permeability of external enclosure structure. There was given the effect of heat saving during air infiltration on the example of a room with a small area.

Study of the Foaming Kinetics in Epoxidized Natural Rubber Foams Crosslinked by Electron Beam Irradiation

AbstractThis work focuses on studying natural rubber (NR) and epoxidized natural rubber (ENR) foams crosslinked at different absorbed doses and foamed using a chemical blowing agent. The aim is to study if the existence of epoxide groups within the natural rubber molecular structure influences the expansion capacity and the cellular structure morphology of these types of foam. This is accomplished by studying the foaming kinetics, that is, by quantifying the evolution of density and cellular structure parameters, such as cell size and cell density, as a function of foaming time. The results show that ENR foams exhibit higher cell nucleation rates and less intense cell degeneration than NR ones, which is because the presence of epoxide groups allows the polymer to reach higher crosslinking levels. Consequently, ENR foams present more homogeneous cellular structures and lower cell sizes.

Directions dependence of the elastic properties of a 3D augmented re-entrant cellular structure

In this paper, a 3D augmented re-entrant cellular structure (ARCS) is proposed and its Poisson's ratios and elastic properties can be modulated in a wide range. Based on the classical beam theory, the elastic properties on the principle directions are obtained as functions of the structural parameters and then are verified by finite element method (FEM) simulations. Compared with the classical 3D re-entrant cellular structure (RCS), the Young's moduli of the new 3D structure on the principal directions show a significant increase, and the Poisson's ratio can be tunable with the control of the internal parameters of cellular structure. In addition, the elastic properties on off-axis directions are obtained by analytical solutions, which show that the Young's moduli on the off-axis directions are much lower than the principle ones. In addition, the shear moduli also show strong dependence on the loading directions. Moreover, by stretching in the principal directions, the ARCS expands in all vertical directions when the moduli ratio is below 0.5. However, stretching in the off-axis directions, the Poisson's ratios are no longer negative in its vertical directions. The results suggest a possible approach to design new auxetic materials with tunable Poisson's ratios for engineering applications.

Influence of the irradiation dose in the cellular structure of natural rubber foams cross-linked by electron beam irradiation

This work focused on the production of natural rubber foams by cross-linking the polymer matrix using high energy electron beam at different irradiation doses (from 50 to 150kGy) and foaming it with a chemical blowing agent. The aim was to study how the irradiation dose influenced the cellular structure morphology of the produced foams. This was accomplished by quantifying the evolution of cellular structure parameters, such as cell size and cell density, with respect to foaming time and irradiation dose. The results showed that the foams irradiated at the lowest dose are more prone to suffer cellular structure degeneration, resulting in the formation of bimodal cellular structures, while foams irradiated with the highest dose, exhibited more uniform cellular structure. In the latter case, the nucleation density clearly increased resulting in the formation of foams with homogeneous cellular structures and smaller cell sizes (≈20μm).

Importance of Gluten and Starch for Structural and Textural Properties of Crumb from Fresh and Stored Bread

Bread crumb cellular structure and elasticity were monitored during aging and their relation to the main flour constituents, gluten and starch, was studied. The linear relation between the time-dependent slope of the linear part of the force-deformation curve, obtained in a static compressive test, and the shear modulus, obtained in quasi-static shear wave measurements, allowed calculating the Poisson’s ratio of bread crumb. This ratio and, thus, cell geometry remain unaffected during bread storage. While the elastic modulus of bread crumb strongly increased upon storage, image analysis and ultrasonic inspection, interpreted in the framework of the Biot-Allard model for porous structures, further confirmed that its cellular structure parameters did not change. Changing gluten properties in dough by means of redox agents had a profound impact on bread crumb density and its foam structure without affecting the rheological properties of the crumb cell walls. In agreement with the theory for cellular solids with open cells, bread with a lower density and a uniform crumb structure initially had a lower elastic modulus, which was maintained during aging, while bread with a higher density showed the opposite. Inclusion of an antifirming maltogenic exo-amylase in the recipe altered neither bread density, nor its macroscopic cellular structure parameters, but strongly affected the impact of storage on crumb texture. It was concluded that, without affecting starch properties or moisture content, the bread density, which is inter alia related to gluten properties, is a major determinant of bread crumb structure and texture during storage. In breads with a similar density and crumb foam structure, the evolution of crumb modulus during storage is determined by the changes in starch.

Changes of cellular structure of potato tuber parenchyma tissues during storage

The presented work is continuation of researches on cellular structure of potato tuber parenchyma tissue. It concerns changes of the potato tuber cellular structure parameters during storage. Tubers of two varieties: Andromeda and Pasat were tested, 5 tubers for each variety and storage period. Cylindrical samples 10 mm in diameter and 1 mm thick were taken out of two types of tissues − potato pith and internal parenchyma from each tuber. Images of the tissues in natural state were taken with optical confocal microscope. Technique elaborated earlier by the author was used to obtain images containing number of cells sufficient for statistical analysis. As the result of analysis performed following mean values parameters of cell size and shape were used: surface area of plane section of the cell A (μm<sup>2</sup>) and cell elongation E. The results show differences between cell size for potato pith and internal parenchyma Andromeda variety and storage period. For this smaller values of the area of cell were obtained just after harvest. No differences of area of cell were observed for Pasat variety, and no differences in elongation of cell were observed for all varieties.

Thermal fatigue resistance of open cell ceramic foams

A variety of open cell ceramic foams were subjected to rapid thermal cycles by infrared heating and forced air cooling to study the thermal fatigue behaviour of these materials. After cycling, the extent of damage in the samples was determined by measuring the elastic modulus using dynamic resonance (non-destructive test) and the retained strength in three-point bending (destructive test). It was found that the retained elastic modulus and strength gradually decreased with an increase in the number of cycles, followed by a saturation behaviour indicating a damage accumulation mechanism. The extent of damage was found to depend on the cellular structure parameters (i.e. cell size and density), composition, as well as thermal cycling variables, such as maximum temperature, cooling rate, etc.