Artykuły w czasopismach: „Porosity and volume fraction detection”

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Demidov, A. A., O. A. Krupnina, N. A. Mikhaylova i E. I. Kosarina. "INVESTIGATION OF POLYMER COMPOSITE MATERIAL SAMPLES BY X-RAY COMPUTED TOMOGRAPHY AND PROCESSING OF TOMOGRAMS WITH THE IMAGE OF THE VOLUME FRACTION OF POROSITY". Proceedings of VIAM, nr 5 (2021): 105–13. http://dx.doi.org/10.18577/2307-6046-2021-0-5-105-113.

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The question of the quality of samples made of polymer composite materials and its verification by x-ray computed tomography is considered. The capabilities of North Star Imaging X5000 tomograph were studied and the samples from PCM were examined for detection and evaluation of the porosity volume fraction. The factors influencing the accuracy of the estimation of the porosity volume fraction are investigated. Namely the size voxel, a filter material, quantity of projections. On the other hand, the size вокселя defines resolution of the digital image, the relation depends on a material of the applied filter a signal/noise, productivity of control worsens with growth of quantity of projections. The choice of optimum values of the listed parametres is necessary for satisfactory quality received tomographic images.

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Pan, Qinxue, Shuangyang Li, Yang Liu, Xiaoyu Xu, Meile Chang i Yunmiao Zhang. "Meso-Simulation and Experimental Research on the Mechanical Behavior of an Energetic Explosive". Coatings 11, nr 1 (7.01.2021): 64. http://dx.doi.org/10.3390/coatings11010064.

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This study establishes a model for polymer-bonded explosives (PBX) using Digimat-FE. The model identifies the relationship between the material’s effective elastic modulus and the explosive particle volume fraction, shape and gradation, and porosity, as well as other factors. Further, finite element analysis of the stress distribution of the PBX composite material is performed, and the mathematical models between the ultrasonic attenuation coefficient, particle volume fraction, and ultrasonic frequency are established. Finally, an efficient ultrasonic nondestructive testing system is designed to determine the stress distribution and fine crack groups in the material. Experimental results indicate that the relative error of stress detection is within 15%, which meets the requirements of engineering applications.

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Pan, Qinxue, Shuangyang Li, Yang Liu, Xiaoyu Xu, Meile Chang i Yunmiao Zhang. "Meso-Simulation and Experimental Research on the Mechanical Behavior of an Energetic Explosive". Coatings 11, nr 1 (7.01.2021): 64. http://dx.doi.org/10.3390/coatings11010064.

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This study establishes a model for polymer-bonded explosives (PBX) using Digimat-FE. The model identifies the relationship between the material’s effective elastic modulus and the explosive particle volume fraction, shape and gradation, and porosity, as well as other factors. Further, finite element analysis of the stress distribution of the PBX composite material is performed, and the mathematical models between the ultrasonic attenuation coefficient, particle volume fraction, and ultrasonic frequency are established. Finally, an efficient ultrasonic nondestructive testing system is designed to determine the stress distribution and fine crack groups in the material. Experimental results indicate that the relative error of stress detection is within 15%, which meets the requirements of engineering applications.

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Di Landro, Luca, Aurelio Montalto, Paolo Bettini, Stefania Guerra, Fabrizio Montagnoli i Marco Rigamonti. "Detection of Voids in Carbon/Epoxy Laminates and Their Influence on Mechanical Properties". Polymers and Polymer Composites 25, nr 5 (czerwiec 2017): 371–80. http://dx.doi.org/10.1177/096739111702500506.

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Defects, such as voids and delaminations, may significantly reduce the mechanical performance of components made of composite laminates. Distributed voids and porosity are generated during composite processing and are influenced by prepreg characteristics as well as by curing cycle parameters. On the basis of rheological and thermal analyses, as well as observations of laminates produced by different processing conditions, curing pressure appears the most influent factor affecting the void content. This work compares different methods for void analysis and quantitative evaluation (ultrasonic scan, micro-computed tomography, acid digestion, SEM image analysis) evidencing their applicative limitations. Carbon/epoxy laminates were produced in autoclave or oven by vacuum bag technique, using different processing conditions, so that void contents ranging from 0% to 7% volume were obtained. Effects of porosity over laminates mechanical performances are analysed. The results of tensile and compressive tests are discussed, considering the effect that different curing cycles have over void content as well as over fibre/resin fraction. Interlaminar strength, as measured by short beam shear tests, which is a matrix-dominated property, exhibits a reduction of failure strength up to 25% in laminates with the highest void content, compared to laminates with no porosity.

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Minh, Chanh Cao, i Padmanabhan Sundararaman. "Nuclear-Magnetic-Resonance Petrophysics in Thin Sand/Shale Laminations". SPE Journal 16, nr 02 (21.10.2010): 223–38. http://dx.doi.org/10.2118/102435-pa.

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Summary We discuss the use of nuclear-magnetic-resonance (NMR) logging in the petrophysical evaluation of thin sand/shale laminations. NMR helps detect thin beds, determine fluid type, establish the hydrocarbon type and volume if hydrocarbon is present, and, finally, determine the permeability of the sand layers (as opposed to that of the sand/shale system). Experiments were conducted on samples of 100% sand, 100% clay, and sand/clay layers with an NMR-logging tool at surface to verify the characteristic T2 bimodal relaxation distribution often observed in NMR logs that are acquired in thin beds. From the bimodal distribution, it is often possible to determine a cutoff to separate the productive sand layers from the shale layers and, with it, the porosity fraction of each component. Subsequently, the sand fraction, or net/gross ratio, can be estimated assuming that the 100%-sand porosity is known. Because gas, oil, and water have different NMR properties, fluid-typing techniques such as 2D NMR offer useful insights into the fluid type and properties in thin-layer sands. Because the laminations thickness is often less than the antenna aperture, the estimated permeability of the sand/ shale system will undercall the true permeability of the sand layers only. In this case, their permeability can be estimated quickly from Darcy's fluid-flow model. We show examples of thin sand/shale laminations that are oil-bearing and gas-bearing. In each case, the NMR detection was verified against borehole-imaging logs, and the fluid type in the sands was determined from multidimensional NMR analysis. The derived hydrocarbon volume was then compared with the results estimated from a triaxial induction tool. Permeability of the sand layers was also computed and compared to that of nearby thick sands. Core data in one well was used to validate NMR detection, porosity, permeability, and net sand thickness.

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Pervukhina, Marina, Pavel Golodoniuc, Boris Gurevich, Michael B. Clennell, Dave N. Dewhurst i Hege M. Nordgård-Bolås. "Prediction of sonic velocities in shale from porosity and clay fraction obtained from logs — A North Sea well case study". GEOPHYSICS 80, nr 1 (1.01.2015): D1—D10. http://dx.doi.org/10.1190/geo2014-0044.1.

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Prediction of sonic velocities in shales from well logs is important for seismic to log ties if the sonic log is absent for a shaly section, for pore pressure anomaly detection, and for data quality control. An anisotropic differential effective medium (DEM) was used to simulate elastic properties of shales from elastic properties and volume fractions of silt and wet clay (a hypothetical composite material that includes all clay minerals and water). Anisotropic elastic coefficients of the wet clay were assumed as a first-order approximation to be linearly dependent on wet clay porosity (WCP). Here, by WCP we mean a ratio of a pore volume occupied by water to a total volume of the wet clay. Effects of silt inclusions on elastic coefficients of shales were taken into account by using the anisotropic differential effective medium model. Silt inclusions were modeled as spherical quartz particles. Simulated elastic coefficients of shales were used to calculate compressional and shear velocities, and these were in a good agreement with the sonic velocities observed on a test data set from an offshore Mid-Norway well penetrating a 500-m vertical section of shale. To further study the elastic properties of wet clays, elastic coefficients calculated from compressional and sonic velocities measured in shales were inverted for vertical profiles of wet clay elastic coefficients. Analysis of these coefficients found that in the well considered, the increase in elastic coefficients of shales was controlled by the increase of silt fraction with depth. Elastic coefficients of wet clay found no increase with depth. The inverted elastic moduli of wet clay found much stronger correlation with WCP than do the moduli of shale. This confirmed the hypothesis that silt fraction is one of the key parameters for the modeling of elastic properties of shale.

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Podymova, N. B., I. E. Kalashnikov i L. I. Kobeleva. "Laser-ultrasonic study of the local porosity of reactive cast aluminum-matrix composites". Industrial laboratory. Diagnostics of materials 87, nr 5 (23.05.2021): 34–42. http://dx.doi.org/10.26896/1028-6861-2021-87-5-34-42.

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One of the most critical manufacturing defects of cast metal-matrix composites is a non-uniform porosity distribution over the composite volume. Unevenness of the distribution leads not only to local softening, but also plays a key role in the evolution of the damage process under the external loads. The goal of the study is to apply a new laser-ultrasonic method to in-situ study of a local porosity in reactive cast aluminum-matrix composites. The proposed method is based on statistical analysis of the amplitude distribution of backscattered broadband pulses of longitudinal ultrasonic waves in the studied materials. Laser excitation and piezoelectric detection of ultrasound were carried out using a laser-ultrasonic transducer. Two series of reactive cast aluminum-matrix composites were analyzed: reinforced by in situ synthesized Al3Ti intermetallic particles in different volume concentrations and by Al3Ti added with synthetic diamond nanoparticles. It is shown that for both series of the composites, the amplitude distribution of backscattered ultrasonic pulses is approximated by the Gaussian probability distribution applicable for statistics of large number of independent random variables. The empirical dependence of the half-width of this distribution on the local porosity in composites of two series is approximated by the same nearly linear function regardless of the size and fraction of reinforcing particles. This function was used to derive the formula for calculation of the local porosity in the studied composites. The developed technique seems to be promising in revealing potentially dangerous domains with high porosity in reactive-cast metal-matrix composites.

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Zhang, Ce, Ying Sun, Jing Xu, Xiaoping Shi i Guoli Zhang. "Study on Curing Deformation of Composite Thin Shells Prepared by M-CRTM with Adjustable Injection Gap". Polymers 14, nr 24 (19.12.2022): 5564. http://dx.doi.org/10.3390/polym14245564.

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A composite thin shell with a high fiber volume fraction prepared by resin transfer molding (RTM) may have void defects, which create deformations in the final curing and lead to the final product being unable to meet the actual assembly requirements. Taking a helmet shell as an example, a multi-directional compression RTM (M-CRTM) method with an adjustable injection gap is proposed according to the shape of the thin shell. This method can increase the injection gap to reduce the fiber volume fraction during the injection process, making it easier for the resin to penetrate the reinforcement and for air bubbles to exit the mold. X-ray CT detection shows that the porosity of the helmet shell prepared by the newly developed technology is 36.6% lower than that of the RTM-molded sample. The void’s distribution is more uniform, and its size is decreased, as is the number of voids, especially large voids. The results show that the maximum curing deformation of the M-CRTM-molded helmet shell is reduced by 13.7% compared to the RTM molded sample. This paper then further studies the deformation types of the shell and analyzes the causes of such results, which plays an important role in promoting the application of composite thin shells.

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Van, P. Phung, i Toan Khong Trong. "EFFECT OF POROSITY ON BEHAVIOURS OF PLATE STRUCTURES". JOURNAL OF TECHNOLOGY & INNOVATION 1, nr 1 (2.03.2020): 10–12. http://dx.doi.org/10.26480/jtin.01.2021.10.12.

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In this paper, effect of porosity on nonlinear analysis of plate structures is presented. Two porous distributions are considered. Governing equations are expressed by using isogeometric analysis (IGA) and the third-order shear deformation theory (TSDT). With these approaches, it is easy to fulfil the C1-continuity requirement of the plate model. The obtained results demonstrate the significance of porosity volume fraction, porosity distributions and volume fraction exponent on nonlinear analysis of the plate structures.

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Mkinga, Oras Joseph, Erik Skogen i Jon Kleppe. "Petrophysical interpretation in shaly sand formation of a gas field in Tanzania". Journal of Petroleum Exploration and Production Technology 10, nr 3 (13.12.2019): 1201–13. http://dx.doi.org/10.1007/s13202-019-00819-x.

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AbstractAn onshore gas field (hereafter called the R field—real name not revealed) is in the southeast coast of Tanzania which includes a Tertiary aged shaly sand formation (sand–shale sequences). The formation was penetrated by an exploration well R–X wherein no core was acquired, and there is no layer-wise published data of the petrophysical properties of the R field in the existing literature, which are essential to reserves estimation and production forecast. In this paper, the layer-wise interpretation of petrophysical properties was undertaken by using wireline logs to obtain parameters to build a reservoir simulation model. The properties extracted include shale volume, total and effective porosities, sand fractions and sand porosity, and water saturation. Shale volume was computed using Clavier equation from gamma ray. Density method was used to calculate total and effective porosities. Thomas–Stieber method was used to determine sand porosity and sand fraction, and water saturation was computed using Poupon–Leveaux model. The statistics of the parameters extracted are presented, where shale volume obtained that varies with zones is between 6 and 54% volume fraction, with both shale laminations and dispersed shale were identified. Total porosity obtained is in a range from 12 to 22%. Sand porosity varies between 15 and 25%, and sand fraction varies between 33 and 93% height fraction. Average water saturation obtained is between 32 and 49% volume fraction.

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Chen, Mengqin, Yuelong Bai, Zhifeng Zhang i Haidong Zhao. "The Preparation of High-Volume Fraction SiC/Al Composites with High Thermal Conductivity by Vacuum Pressure Infiltration". Crystals 11, nr 5 (6.05.2021): 515. http://dx.doi.org/10.3390/cryst11050515.

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The high-volume fraction SiC/Al composite is the new type of electronic packaging material, which plays an important role in the field of high-power integrated circuits. In this study, SiC/Al composites with high-volume fraction of SiC particles were prepared by vacuum pressure infiltration. The influence of SiC particle size and NH4HCO3 on the pores in the preform was explored, aiming to accurately adjust the volume fraction of SiC to meet the thermal performance requirements in different fields. In addition, the preform was infiltrated with different Al alloys, and the relationship between the porosity and thermal conductivity of SiC/Al was studied. For the SiC preform, the volume fraction of SiC can be adjusted regularly when 12 μm and 100 μm SiC particles are mixed in different proportions, and the volume fraction reaches the maximum when the proportion of coarse particles is about 77%. NH4HCO3 is conducive to the connectivity of pores in the preform, and about 40 vol.% of NH4HCO3 can effectively increase the porosity of the preform. Thermal conductivity is sensitive to the porosity of composites, especially in the range of 2.5–4.5%. A simple application of the Hasselman–Johnson model and a new thermal conductivity model, λd, established in this article, offer a good agreement with the experimental results.

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Higaeg, Mohamed, Igor Balac, Aleksandar Grbovic, Milorad Milovancevic i Milos Jelic. "Numerical modeling of the porosity influence on strength of structural materials". Science of Sintering 51, nr 4 (2019): 459–67. http://dx.doi.org/10.2298/sos1904459h.

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The effect of micro-scale structural low-level porosity on strength of structural materials was studied using the three-dimensional Unit Cell Numerical Model - UCNM. A comparison between proposed UCNM and available experimental data in literature was done by comparing obtained values for stress concentration factor - SCF for different sizes and shapes of pore. Results for normalized strength obtained by proposed UCNM model are in agreement with available experimental data published in literature. It was confirmed that material porosity in form of closed pores, regarding pores? size (volume fraction) and shape, has note cable influence on strength of structural material. Less porosity in the material microstructure generally leads to higher values of material strength. For fixed porosity volume fraction, shape of pores has an impact on strength of structural material.

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Leontiev, Alexey P., Olga Yu Volkova, Irina A. Kolmychek, Anastasia V. Venets, Alexander R. Pomozov, Vasily S. Stolyarov, Tatiana V. Murzina i Kirill S. Napolskii. "Tuning the Optical Properties of Hyperbolic Metamaterials by Controlling the Volume Fraction of Metallic Nanorods". Nanomaterials 9, nr 5 (14.05.2019): 739. http://dx.doi.org/10.3390/nano9050739.

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Porous films of anodic aluminum oxide are widely used as templates for the electrochemical preparation of functional nanocomposites containing ordered arrays of anisotropic nanostructures. In these structures, the volume fraction of the inclusion phase, which strongly determines the functional properties of the nanocomposite, is equal to the porosity of the initial template. For the range of systems, the most pronounced effects and the best functional properties are expected when the volume fraction of metal is less than 10%, whereas the porosity of anodic aluminum oxide typically exceeds this value. In the present work, the possibility of the application of anodic aluminum oxide for obtaining hyperbolic metamaterials in the form of nanocomposites with the metal volume fraction smaller than the template porosity is demonstrated for the first time. A decrease in the fraction of the pores accessible for electrodeposition is achieved by controlled blocking of the portion of pores during anodization when the template is formed. The effectiveness of the proposed approach has been shown in the example of obtaining nanocomposites containing Au nanorods arrays. The possibility for the control over the position of the resonance absorption band corresponding to the excitation of collective longitudinal oscillations of the electron gas in the nanorods in a wide range of wavelengths by controlled decreasing of the metal volume fraction, is shown.

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MARIN, Mihaela, i Florin-Bogdan MARIN. "Determination of Porosity in Fluidized-Bed Carburized P/M Compacts Using an Image Software Analysis". Annals of “Dunarea de Jos” University of Galati. Fascicle IX, Metallurgy and Materials Science 44, nr 4 (15.12.2021): 40–43. http://dx.doi.org/10.35219/mms.2021.4.07.

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The aim of this research was to study the porosity in carburizing in fluidized-bed on sintered alloys produced by powder metallurgy route using an image analysis software and to compare the obtained results with the conventional method for porosity measurements. Porosity is a measure of the void fraction in a material. The total porosity is defined by the ratio of the volume of void space to the total bulk volume of the material, expressed as a percentage. Development of digital images and computer software lead to a new and suitable method to determine the porosity of powder metallurgy materials.

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Haryono, Florencius Eko Dwi, Hydian Suripto i Mukti Trenggono. "Sediment Porosity Investigation of Tidal Zone in Teluk Penyu Cilacap, Indonesia". Omni-Akuatika 16, nr 3 (30.12.2020): 71. http://dx.doi.org/10.20884/1.oa.2020.16.3.858.

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The sediment fraction is the grain size, sorting and composition of the sediment, while sediment porosity is the ratio of the volume of the cavity in total volume. The cavity in marine sediment is a habitat of decomposing organisms. The research aimed to analyze the relationship between the fraction and porosity of tidal zone sediments in coastal of Teluk Penyu Cilacap. This survey method used sediment core samplers, sediments fractions used sieve method and the porosity used method of Reeve (1986), and analysis used software SPSS20. The results showed that tidal zone sediments in coastal of Teluk Penyu Cilacap were dominated by the fine sand with percentage when high water was higher than low water. Based on mean size diameter, sediment near Serayu river was found medium sand and far was fine sand. Based on linear regression, the relation between sediment fraction and porosity at high water and low water was obtained very weak, but when low water was found in opposite condition to the high water, that the greater of sediment diameter was smaller of porosity. High porosity indicates a wider space between the sediments and allows more decomposing organisms. It is important to consider the results of the clearing of organic matter which affects to fish resources in coastal waters. Keywords: sediment fractions, porosity, teluk penyu

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Li, Ji Lin, Yue Qun Ma, Rong Shi Chen i Wei Ke. "Effects of Shrinkage Porosity on Mechanical Properties of a Sand Cast Mg-Y-Re (WE54) Alloy". Materials Science Forum 747-748 (luty 2013): 390–97. http://dx.doi.org/10.4028/www.scientific.net/msf.747-748.390.

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The distribution of shrinkage porosities in sand cast Mg-Y-RE (WE54) alloy castings was characterized through density measurement and calculated by Archimedess principle. The effect of porosity on mechanical properties of sand cast WE54 alloy was investigated through tensile tests and microstructure observation. It was found that the shrinkage porosities distributed mainly in the middle of the plate where the liquid feeding was quite inconvenient. And the porosities were formed along grain boundaries when secondary phases formed at the end of solidification. Hardness tests showed that the vikers hardness declined linearly with increasing porosity volume fraction. While the tensile strength and nominal yield strength declined exponentially as the porosity volume fraction increased. Microstructure observation showed that the fracture cracks propagated along the grain boundaries where porosities and secondary phases gathering together in as-cast WE54 alloy. The tiny porosities distributed in the secondary phases were observed, which could reduce the tensile strength of cast specimens significantly. The heat treatment strengthening effects were significantly weakened by porosities, and even no heat treatment strengthening effect was detected when the porosity volume fraction was higher than 1%. The microstructure observation also proved that no heat treatment strengthening effect existed in samples containing porosities.

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Abdulrazag, Elmiladi, Igor Balac, Katarina Colic, Aleksandar Grbovic, Milorad Milovancevic i Milos Jelic. "Numerical modeling of the porosity influence on the elastic properties of sintered materials". Science of Sintering 51, nr 2 (2019): 153–61. http://dx.doi.org/10.2298/sos1902153a.

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The effect of structural porosity on the elastic properties of sintered materials was studied using the new multi-pore unit cell numerical model - MPUC. Comparison between proposed MPUC model and previously adopted two-phase unit cell - FCC numerical model as well as available experimental data in literature, was done by comparing obtained values for modulus of elasticity - E, shear modulus - G and Bulk modulus - K. Results obtained by proposed MPUC model are in excellent agreement with available experimental data in literature. It was confirmed that material porosity regarding pores? size (volume fraction) has noticeable influence on elastic properties of sintered material. Less porosity in the material microstructure generally leads to noticeable higher values of E, G and K. For fixed volume fraction, shape of pores has no significant influence on elastic characteristics.

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Wu, Gruorong, i Jie Ouyang. "Use of Precise Area Fraction Model for Fine Grid DEM Simulation of ICFB with Large Particles". Symmetry 12, nr 3 (4.03.2020): 399. http://dx.doi.org/10.3390/sym12030399.

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The heterogeneous structures in a gas–solid fluidized bed can be resolved in discrete element simulation so long as the grid is fine enough. In order to conveniently calculate mean porosity in fine grid simulations, a precise area fraction model is given for two-dimensional simulations. The proposed area fraction model is validated by the discrete element simulation test on a small-scale internal circulation fluidized system of large particles, using a fine grid size of two particle diameters. Simulations show that the discrete element method can perform well in modelling time-varying waveforms for the physical quantities in an internal circulating fluidized bed, employing the precise gas area fraction model. This thought of precise calculation can be generalized to construct a volume fraction porosity model for three-dimensional simulation by use of the similar symmetry of a rectangular grid. Moreover, to construct these area and volume fraction models is to enrich and perfect the underlying model of fine grid simulation.

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Sreedhara, Sudhakara Sarma, i Narasinga Rao Tata. "A Novel Method for Measurement of Porosity in Nanofiber Mat using Pycnometer in Filtration". Journal of Engineered Fibers and Fabrics 8, nr 4 (grudzień 2013): 155892501300800. http://dx.doi.org/10.1177/155892501300800408.

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Electrospun Polymer nanofibers have a wide range of applications including automotive air filters. Large surface area, small pores, flexible and adequate porosity are widely recognized as important parameters for improving the performance of the filter media and therefore measuring the porosity of the medium is extremely important. Porosity measurement techniques such as density based method, mercury porosimetry, capillary flow porometry, image analysis are relatively inaccurate and they have some disadvantages for measuring the porosity of the nano fibers. In the present study porosity measurement for nanofiber mat using pycnometer was explored. Pycnometer is generally used to measure the density of the solids of having volumes upto 150 cc. Volume of the nanofiber was measured by pycnometer and porosity is determined as fraction of the void in total volume of the fiber. Total volume is calculated from FESEM image thickness. Various advantages of pycnometry method when compared to other techniques were discussed based on the results of porosity measurements of nanofiber mats.

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Guo, Chao Qun, Ya Dong Sun, Yun Zhou, Bo Xie, Tian Yao Wang i Xiao Qing Zuo. "Fabrication, Structure and Property of Copper Foam". Materials Science Forum 933 (październik 2018): 41–48. http://dx.doi.org/10.4028/www.scientific.net/msf.933.41.

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Copper foams by using CaCl2 as space holder were successfully manufactured by sintering and dissolution process. The porosity ranges from 75% to 91%, and cell size from 0.3mm to 3.0m. The volume fraction of CaCl2 and sintering temperature are the main factors that affect porosity of copper foam. The yield plateau stress of copper foams with porosity between 75.88% and 90.19% is in range of 12.1~1.2MPa. The yield plateau stress decreases with the increase of porosity. The energy absorption per unit volume (W) copper foams with porosity between 75.88% and 90.19% is in range of 6.17~0.63MJ/m3. Under the condition of identical porosity, the absorption energy per unit volume (W) of copper foam is about 43% higher than aluminum foam. The maximum ideal energy absorption efficiency of copper foam is about 0.74, it indicates that the copper foam can be used as a good absorbing material.

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Kumar, Rajneesh, i Richa Vohra. "Response of thermoelastic microbeam with double porosity structure due to pulsed laser heating". Mechanics and Mechanical Engineering 23, nr 1 (10.07.2019): 76–85. http://dx.doi.org/10.2478/mme-2019-0011.

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Abstract The present investigation is concerned with vibration phenomenon of a homogeneous, isotropic thermoelastic microbeam with double porosity (TDP) structure induced by pulsed laser heating, in the context of Lord– Shulman theory of thermoelasticity with one relaxation time. Laplace transform technique has been applied to obtain the expressions for lateral deflection, axial stress, axial displacement, volume fraction field, and temperature distribution. The resulting quantities are recovered in the physical domain by a numerical inversion technique. Variations of axial displacement, axial stress, lateral deflection, volume fraction field, and temperature distribution with axial distance are depicted graphically to show the effect of porosity and laser intensity parameter. Some particular cases are also deduced.

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Siddiqui, Muhammad Owais Raza, Salma Farooq, Muhammad Dawood Husain i Saira Faisal. "Prediction of air permeability and effective thermal conductivity of multifilament polyester yarn by finite element analysis". Polimery 68, nr 1 (23.02.2023): 6–18. http://dx.doi.org/10.14314/polimery.2023.1.2.

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The effective thermal conductivity and air permeability of a multifilament polyester yarn used in sports T-shirts was investigated by computer modeling using finite element analysis. It has been shown that the number of fibers, the porosity of the yarn and the proportion of fibers in the volume fraction of the yarn have a direct effect on the effective thermal conductivity and air permeability of the multifilament yarn. It was found that with the increase in the number of fibers, the porosity of the yarn decreases linearly, while the volume fraction of the fibers increases, and thus the effective thermal conductivity increases. In addition, air permeability decreases exponentially.

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Azmi, K., Mohd Mustafa Al Bakri Abdullah i M. A. A. Mohd Salleh. "Fabrication of Cu-SiC_p Composites via the Electroless Copper Coating Process for the Electronic Packaging Applications". Advanced Materials Research 795 (wrzesień 2013): 272–75. http://dx.doi.org/10.4028/www.scientific.net/amr.795.272.

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Silicon carbide reinforced copper matrix (Cu-SiCp) composites are highly rated as thermal management materials due to their high thermal conductivity and low thermal expansion properties. However, the Cu-SiCp composites fabricated via the conventional powder metallurgy methods have substandard properties due to the weak bonding between the copper matrix and the SiCp reinforcement. In order to strengthen the bonding, the SiCp were coated with copper via electroless coating process. Based on the experimental results, a continuous copper deposition on the SiCp was obtained. The Cu-Coated layer improved the green strength of the composites thus allowed a high volume fraction of SiCp to be incorporated into the copper matrix. However, the increase in the volume fraction of SiCp has a significant effect on the apparent porosity of the Cu-SiCp composites. Nevertheless, the porosity of the Cu-Coated Cu-SiCp composites remained significantly lower than those of non-Coated Cu-SiCp composites especially at high volume fraction of SiCp.

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Nguyen, B. V., K. S. Challagulla, T. A. Venkatesh, D. A. Hadjiloizi i A. V. Georgiades. "Effects of porosity distribution and porosity volume fraction on the electromechanical properties of 3-3 piezoelectric foams". Smart Materials and Structures 25, nr 12 (14.11.2016): 125028. http://dx.doi.org/10.1088/0964-1726/25/12/125028.

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Шейнерман, А. Г., i С. А. Красницкий. "Моделирование влияния агломерации графена на механические свойства керамических композитов с графеном". Письма в журнал технической физики 47, nr 17 (2021): 37. http://dx.doi.org/10.21883/pjtf.2021.17.51385.18844.

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A model is proposed that describes the porosity, hardness, and fracture toughness of ceramic composites with agglomerates of graphene platelets. The model assumes that the agglomeration of graphene platelets occurs during the hot pressing of such composites, and pores are formed around the agglomerates. Within the model, the dependences of porosity, hardness, and fracture toughness of ceramic/graphene composites on the volume fraction of graphene are calculated. It is shown that the formation of pores explains the experimentally observed drop in the hardness and fracture toughness of composites for the volume fraction of graphene exceeding a critical value. The results of the model agree with the experimental data for the composites Al2O3-WC-TiC-Gr.

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Wang, Yan Jun, Bin Wang, Li Ying Yang i Shou Ren Wang. "Microstructure Development and Properties of HSS-Based Self-Lubrication Composites". Advanced Materials Research 217-218 (marzec 2011): 625–30. http://dx.doi.org/10.4028/www.scientific.net/amr.217-218.625.

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High speed steel based ceramic preforms with three-dimensionally interpenetrated micropores were fabricated using the mixture of TiH2, CaCO3 and stearic acid as pore-forming agent. A self-made vacuum high pressure infiltration furnace was used to infiltrate the preforms with Pb-Sn based solid lubricants to create almost fully dense self-lubrication composites. The microstructure and properties of HSS-based self-lubrication composites were investigated as a function of sintered porosity. A quantitative analysis of microstructure was correlated with crushing strength，microhardness and wear rate to understand the influence of pore size, shape and distribution on mechanical and tribological behavior. Crushing strength and microhardness decreased with an increase in porosity. Meanwhile the decrease in microhardness with increasing porosity was slightly. The friction coefficient of HSS-based self-lubrication composites decreased with increasing the volume fraction of lubricant due to the self-lubrication and unique micropore structure. Within the range of lubricant volume fraction from 0% to 14%, the wear rate of the composites decreased steadily with the increase of lubricant content in the composites. Micropore structure and lubricant volume fraction play an important role in determining wear resistance of the composites whereas the measured bulk properties seem to be of minor importance.

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Zheng, Hong Liang, Yu Cheng Sun, Ning Zhang, Kai Zhang i Xue Lei Tian. "Shrinkage Porosity Simulation of Spheroidal Graphite Iron Castings Based on Macro-Micro Models". Materials Science Forum 689 (czerwiec 2011): 190–97. http://dx.doi.org/10.4028/www.scientific.net/msf.689.190.

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Shrinkage porosity is often found in Spheroidal graphite iron (S. G. Iron) castings because of the mushy zone and special volume change during their solidification. Although the volume expansion is very important to the shrinkage porosity simulation of S.G. Iron castings, conventional methods for predicting the porosity defects do not consider it. A Series of macro-micro models such as macro heat transfer calculation and microstructure formation simulation are proposed to simulate the solidification of S. G. Iron castings. The nucleation and growth models are employed to calculate the accurate latent heat and volume change especially graphite expansion during the solidification. The pressure induced by graphite expansion is introduced as a parameter to predict the shrinkage porosity and a new shrinkage porosity criterion is developed. Cooling curves and solid fraction of each phase are compared with experimental castings. At the same time, the porosity area ratio of castings is compared with the results calculated by several porosity criterions. The results show that the new shrinkage porosity simulation criterion of S. G. Iron castings based on macro-micro models is accurate on shrinkage porosity shape, size and distribution simulation.

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Liu, Shan, Fei Chen, Ying Yang, Qiang Shen i Kai Peng Zhang. "Thermo-Mechanical Analysis of Si₃N₄-Based Seal Coatings on Si₃N₄ Substrate". Key Engineering Materials 508 (marzec 2012): 42–47. http://dx.doi.org/10.4028/www.scientific.net/kem.508.42.

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In this Study, a Good Combination between Si3N4-Based Seal Coatings and Porous Si3N4Substrate Was Achieved by Room Temperature Spraying and Pressureless Sintering. To Evaluate the Joint Quality, Residual Stress due to Thermal Expansion Mismatch between the Coatings and Porous Layers Were Characterized by Computational Studies Using the Finite Element ANSYS Code. It Was Found that Si3N4-Based Seal Coating Allows a Gradual Change in Thermal Expansion Mismatch, Minimizing the Thermal Stresses Arising from Cooling or Heating. Further Theoretical Analysis Indicates that the Thermal Expansion Mismatch between the Two Layers Produced a Large Strengthening Effect for the Fraction of the Porosity below a Critical Level and that Substrates with the High Fraction of Porosity Showed Complete Cracking, as the Cracks Initiating in Adjacent Coatings. And the Volume Fraction of Pores Required to Cause Crack Deflection, in the Porous Layer, Was Predicted. The Effects of Layer Thickness and Porosity Fraction on Residual Stress Were Studied, which Are Used as Predictions towards Better Design of Composite Materials.

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Kossakowski, P. G. "Influence of Initial Porosity on Strength Properties of S235JR Steel at Low Stress Triaxiality". Archives of Civil Engineering 58, nr 3 (1.09.2012): 293–308. http://dx.doi.org/10.2478/v.10169-012-0017-9.

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Abstract The paper discusses the influence of the initial parameters on the strength parameters of S235JR steel at low stress triaxiality. The analysis was performed using the Gurson-Tvergaard-Needleman (GTN) material model, which takes into consideration the material structure. The initial material porosity was defined as the void volume fraction f0. The fully dense material without pores was assumed and the typical and maximum values of porosity were considered for S235JR steel in order to analyse the porosity effect. The strength analysis of S235JR steel was performed basing on the force-elongation curves obtained experimentally and during numerical simulations. Taking into consideration the results obtained, the average values of the initial void volume fraction f0 = 0.001 for S235JR steel is recommended to use in a common engineering calculations for elements operating at low stress triaxiality. In order to obtain more conservative results, the maximum values of f0 = 0.0024 may be used.

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30

Niang, Ibrahim, Chadi Maalouf, Tala Moussa, Christophe Bliard, Etienne Samin, Céline Thomachot-Schneider, Mohamed Lachi, Hervé Pron, Ton Hoang Mai i Salif Gaye. "Hygrothermal performance of various Typha–clay composite". Journal of Building Physics 42, nr 3 (22.05.2018): 316–35. http://dx.doi.org/10.1177/1744259118759677.

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This article deals with the influence of both morphology and amount of Typha on hygrothermal behavior of a Typha–clay composite for building application. An agromaterial containing the fiber mix of Typha Australis and clay was made in three samples: three fiber mixtures were prepared with different amounts Typha and cut type (transversal or longitudinal). The physical properties of these materials were studied in terms of porosity, apparent and absolute density, thermal conductivity, and hygric properties. Results show a real impact of the Typha fraction type and its volume content on hygrothermal properties of the studied material due to the porosity. The transversal fraction of Typha (80% in volume weight) seems to be the optimal composition for a better hygrothermal behavior.

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AMAZIANE, B., L. PANKRATOV i A. PIATNITSKI. "HOMOGENIZATION OF A SINGLE PHASE FLOW THROUGH A POROUS MEDIUM IN A THIN LAYER". Mathematical Models and Methods in Applied Sciences 17, nr 09 (wrzesień 2007): 1317–49. http://dx.doi.org/10.1142/s0218202507002339.

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The paper deals with homogenization of stationary and non-stationary high contrast periodic double porosity type problem stated in a porous medium containing a 2D or 3D thin layer. We consider two different types of high contrast medium. The medium of the first type is characterized by the asymptotically vanishing volume fraction of fractures (highly permeable part). The medium of the second type has uniformly positive volume fraction of fracture part. In both cases we construct the homogenized models and prove the convergence results. The techniques used in this work are based on a special version of the two-scale convergence method adapted to thin structures. The resulting homogenized problems are dual-porosity type models that contain terms representing memory effects.

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Wang, Chun Hua, Shao Kang Guan, Shou Shan Li i Rui Zhang. "Mechanical Properties of SiC_p/Cu Composites Prepared by Electric Conduction Sintering". Key Engineering Materials 353-358 (wrzesień 2007): 1402–5. http://dx.doi.org/10.4028/www.scientific.net/kem.353-358.1402.

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SiCp/Cu composites were fabricated at 700 oC and under 40MPa for 10min in vacuum by electric conduction sintering. The mechanical properties and microstructure of the composites were studied. The porosity of the composites increases when the volume fraction of SiCp exceeds 35%. The flexural strength of the composites decreases with increasing fraction of SiCp. The composites with 10 vol.% SiCp exhibited ductile fracture behavior, while composites with the volume fraction of SiCp in the range of 20–65% exhibited brittle fracture behavior. The composites with 35 vol.% SiCp showed the highest hardness.

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33

Dańko, R., i J. Dańko. "Determination of the Surface and Volume Porosity, on the Basis of the Main Fraction of the Polifractional Matrix of Moulding and Core Sands". Archives of Foundry Engineering 16, nr 4 (1.12.2016): 191–95. http://dx.doi.org/10.1515/afe-2016-0108.

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Abstract The aim of the hereby paper is to present the developed model of determining the volume and surface porosity based on the main fraction of polifractional materials, its experimental verification and utilisation for the interpretation of effects accompanying the formation of a moulding sand apparent density, porosity and permeability in the blowing processes of the core and moulds technology.

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34

Vaka, Vijayakumar, Prabhakar Sathujoda, Neelanchali Asija Bhalla, Y. V. Satish Kumar i Roberto Citarella. "A Study on Dynamic Behaviour of Thermally Distributed Exponentially Graded Rotor System with Induced Porosities". Mathematical Problems in Engineering 2022 (2.06.2022): 1–14. http://dx.doi.org/10.1155/2022/2424772.

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The present work deals with the dynamic analysis of exponential law-based functionally graded (FG) rotor-bearing systems. The effect of thermal gradation and porosity on dynamic characteristics of FG rotor shafts has been studied first time, using exponential law with a novel two-nodded FG rotor element based on Timoshenko beam theory (TBT). Porous material properties are assorted using exponential law and thermal gradation across the cross section of the FG shaft using exponential temperature distribution (ETD). The effects of temperature and porosity on natural frequencies and whirl frequencies are studied. It has been observed that there is a significant reduction in natural frequencies and whirl frequencies with an increase in volume fraction of porosity and temperature. Attempts have been made to obtain suitable reasons for the behaviours based on the material properties. Furthermore, the steady-state and transient vibration responses have been simulated using the Houbolt time marching technique for the ceramic-based FG rotor shaft system. The result shows the maximum amplitude of the steady-state and transient vibration responses is increased, and the critical speed of the FG rotor system shifts towards the left with the increase in volume fraction of porosity and temperature.

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35

Tang, Cheng Yang, Wen Yi, Xian Feng He i Li Tan. "The Comparison and Analysis of Void Fraction of OGFC-13 Asphalt Concrete through Vacuum Method and Volume Method". Applied Mechanics and Materials 847 (lipiec 2016): 17–24. http://dx.doi.org/10.4028/www.scientific.net/amm.847.17.

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In this paper, the mixture ratio experiment has been done about OGFC-13 asphalt mixture of the layer on S103(liuyang section) of Changsha, Hunan province The void fraction of asphalt mixture is determined by vacuum sealing method and volume method on the condition of different material and different gradation. Through the comparison and analysis of void fraction determined values by vacuum method and volume method, it can been found that the air porosity of OGFC-13 asphalt mixture has a good linear relationship with the 2.36mm pass rate. The linear relationship of void fraction determined value by vacuum method and volume method relates with materials and nominal diameter.

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36

Hilliard, Zachary J., i Pavel R. Hrma. "The void fraction of melter feed during nuclear waste glass vitrification". MRS Proceedings 1744 (2015): 107–12. http://dx.doi.org/10.1557/opl.2015.311.

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ABSTRACTTo efficiently vitrify Hanford waste, the melting process (i.e., melter feed turning into waste glass) must be modeled and optimized. The rate of heat transfer to the melter feed in a waste glass melter, and thus the rate of melting, is strongly affected by the melter feed porosity, especially in the final stages where the glass-forming melt produces foam that insulates the feed from the molten glass. The volume expansion test allows the determination of the melter feed porosity as a function of temperature. This test measures the profile area of the feed pellet as it turns into glass. This contribution presents the calculation of the void fraction (porosity) of the melter feed as a function of temperature, heating rate, and material parameters. The process of finding the void fraction is described as well as results from the application of this process.

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37

Lv, Sheng Li, Qing Na Zeng, Lei Jiang Yao, Liu Ding Chen i Xiao Yan Tong. "Microstructure Modeling for Prediction of Thermal Conductivity of Plain Weave C/SiC Fibre Bundles Considering Manufacturing Flaws". Applied Mechanics and Materials 109 (październik 2011): 17–22. http://dx.doi.org/10.4028/www.scientific.net/amm.109.17.

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The aim of this paper is to propose a microstructure modeling for prediction of thermal conductivity of plain weave C/SiC fibre bundles considering manufacturing flaws. Utilized photomicrographs taken by scanning electron microscope (SEM), an accurate representative volume element (RVE) model for carbon fiber bundles is established. Based on the steady-analysis method, the axial and transverse thermal conductivity of the carbon fibre bundles are calculated as 40.32Wm-1K-1 and 11.33 Wm-1K-1, respectively. The manufacturing flaws have different effects on thermal conductivity, the study shows that class A porosity has a significant effect on thermal conductivity, which leads to the thermal conductivity on the axial direction decrease by 13.31% and transverse direction decrease by 20.56% compared with no flaws RVE. While class B porosity has little influence on the k-value. The change law of axial and transverse thermal conductivity along with porosity volume is also observed: as porosity volume fraction is increasing, the thermal conductivity of fibre bundles shows significant linear decrease.

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Cho, Jin-Rae. "Natural Element Static and Free Vibration Analysis of Functionally Graded Porous Composite Plates". Applied Sciences 12, nr 22 (16.11.2022): 11648. http://dx.doi.org/10.3390/app122211648.

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The static bending and free vibration of functionally graded (FG) porous plates were analyzed by a 2D natural element method (NEM). Recent studies on FG materials considered the porosity because micropores and porosity were observed during the fabrication of FG materials owing to the difference in solidification temperatures. However, the mechanical responses of FG porous plates were not sufficiently revealed, and furthermore most numerical studies relied on the finite element method. Motivated by this situation, this study intended to investigate the combined effects of material composition and porosity distributions and plate thickness on the static bending and free vibration responses of ceramic–metal FG plates using 2D NEM incorporated with the (3,3,2) hierarchical model. The proposed numerical method is verified from the comparison with the reference such that the maximum relative difference is 5.336%. Five different porosity distributions are considered and the central deflection and the fundamental frequency of ceramic–metal FG porous plates are parametrically investigated with respect to the combination of the porosity parameter, the ceramic volume fraction index, and the width–thickness (w/t) ratio and to the boundary condition. The ranges of three parameters were set to 0–0.5 for the porosity, 0–0.6 for the ceramic volume fraction, and 3–20 for the width–thickness ratio. It was found from the numerical experiments that the static and free vibration responses of ceramic–metal FG porous plates are significantly affected by these parameters.

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Joulaee, N., Ahmed Makradi, Saïd Ahzi i Moe A. Khaleel. "Fracture Toughness and Crack Deflection in Porous Multilayered Ceramics: Application to NiO-YSZ". Materials Science Forum 553 (sierpień 2007): 69–74. http://dx.doi.org/10.4028/www.scientific.net/msf.553.69.

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The arrangement of ceramic layers in laminated structures is an interesting way to enhance the flaw tolerance of brittle ceramic materials. The interfaces are expected to deflect cracks, increasing the fracture energy of the laminate compared to a monolithic material and thus raising the toughness. The target of this study is to predict the volume fraction of pores, in porous layers, required to cause crack deflection. Formulation of the fracture toughness and fracture energy as function of the material porosity is presented for random and ordered pores distribution. The effect of crack tip-flaws interaction is considered to estimate the pores volume fraction needed for crack deflection. In this work, dense and porous layers of NiO-YSZ material similar to the one used in the fuel cells technology are considered. The fracture energy of a porous material with an ordered distribution of pores shows a possibility of crack deflection at a porosity of 22.5%. However for a system with randomly distributed pores this possibility can be seen at 36% of porosity.

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40

Abbas Tiambo DATCHOSSA, Valéry Kouandété DOKO i Emmanuel Essè Timothée OLODO. "Evaluation of the dynamic modulus of elasticity of a pozzolanic mortar of rice husk ash reinforced with sugarcane bagasse". World Journal of Advanced Research and Reviews 17, nr 2 (28.02.2023): 709–17. http://dx.doi.org/10.30574/wjarr.2023.17.2.0311.

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In the last decades, many works are going in the direction of valorization of vegetable biomass. The aim of the present work is to determine the dynamic modulus of elasticity of a cementitious matrix composite with rice husk ash pozzolan reinforced with sugarcane bagasse. To do this, we formulated mortars in which we varied the volume fraction of sugarcane bagasse and kept 10% of rice husk ash as a cement replacement. The sugarcane bagasse fractions of 0%, 3%, 6% and 10% yielded the mortars denoted RHA10, R10SB3, R10SB6, R10SB10, respectively. We have experimentally determined the density, the porosity of the different mortars obtained. Then, we determined by ultrasound test the speed of propagation of sound waves in the different mortars before calculating their dynamic moduli of elasticity. The results of the study show that the porosity, density, and dynamic modulus of elasticity of RHA10 mortars decreases with the increase of the volume fraction of sugarcane bagasse. The dynamic moduli of RHA10, R10SB3, R10SB6 and R10SB10 are 3.25GPa, 3.14GPa, 2.56GPa, 1.71GPa respectively with a porosity-dynamic modulus correlation R² of 0.94.

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Van Ginkel, J. T., P. A. C. Raats i I. A. Van Haneghem. "Bulk density and porosity distributions in a compost pile". Netherlands Journal of Agricultural Science 47, nr 2 (1.11.1999): 105–21. http://dx.doi.org/10.18174/njas.v47i2.470.

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This paper mainly deals with the description of the initial distribution of bulk density and porosity at the moment a compost pile is built or rebuilt. A relationship between bulk density and vertical position in a pile is deduced from theoretical and empirical considerations. Formulae to calculate the air filled volume fraction and the true densities of the solid phase and of the organic matter are derived. The true density of dry matter is used in the computation of porosity distributions. The relationships between bulk density and height and between air-filled volume fraction and height are shown to be valid for composting material consisting of chopped wheat straw and chicken manure. The check of this validity is limited to total bulk density values ranging from 150 to 950 kg/msuperscript 3, with values of dry matter content varying between 18 and 28% (w.b.). Moreover, the gravimetric dry matter content must be constant throughout the total cross section of the pile. The error in the calculated bulk densities and air-filled volume fractions was found to be 12% at a reliability level of 95%. It was concluded that the presented equations will give reasonable results for other values of dry matter content and other kinds of chopped fibrous materials as long as the gravimetric dry matter content remains independent of height.

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Dybowski, Bartłomiej, Łukasz Poloczek i Andrzej Kiełbus. "The Porosity Description in Hypoeutectic Al-Si Alloys". Key Engineering Materials 682 (luty 2016): 83–90. http://dx.doi.org/10.4028/www.scientific.net/kem.682.83.

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Al-Si alloys are the most important group among aluminum casting alloys. They are widely used in automotive and aerospace industries. Chemical modification of the Al-Si alloys leads to formation of fine, fibrous Al-Si eutectic mixture ensuring high mechanical properties. The modification is however known to increase the alloy porosity, which may, in turn, result in decrease of its properties. The following paper presents results of the research on quantitative description of the Al-Si cast alloys porosity and influence of Na modification on the porosity of AlSi9Mg alloy. Porosity in the hypoeutectic Al-Si alloys occurs in four types: shrinkage cavities, shrinkage porosity, isolated gas pores and gas pores surrounded by shrinkage porosity. Na modification leads to increase of shrinkage pores volume fraction.

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Roskosz, S. "Quantitative Evaluation of Porosity in Turbine Blades Made of IN713C Superalloy After Hot Isostatic Pressing". Archives of Metallurgy and Materials 62, nr 1 (1.03.2017): 253–58. http://dx.doi.org/10.1515/amm-2017-0038.

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Abstract The aim of this paper is an assessment of the influence of hot isostatic pressing treatment on porosity of cast samples - turbine blades and vane clusters made of the IN713C superalloy. Two variants of HIP treatments, differing in pressure from each other, have been used. The quantitative evaluation of the porosity was performed using light microscopy and quantitative metallography methods. The use of the hot isostatic pressing significantly decreased the volume fraction and size of pores in the test blades, the remaining pores after the HIP process being characterized by a round shape. The increased pressure has caused significant reductions in the area fraction and size of the pores.

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Bahadur, Jitendra, Cristian R. Medina, Lilin He, Yuri B. Melnichenko, John A. Rupp, Tomasz P. Blach i David F. R. Mildner. "Determination of closed porosity in rocks by small-angle neutron scattering". Journal of Applied Crystallography 49, nr 6 (2.11.2016): 2021–30. http://dx.doi.org/10.1107/s1600576716014904.

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Small-angle neutron scattering (SANS) and ultra-small-angle neutron scattering (USANS) have been used to study a carbonate rock from a deep saline aquifer that is a potential candidate as a storage reservoir for CO2sequestration. A new methodology is developed for estimating the fraction of accessible and inaccessible pore volume using SANS/USANS measurements. This method does not require the achievement of zero average contrast for the calculation of accessible and inaccessible pore volume fraction. The scattering intensity at highQincreases with increasing CO2pressure, in contrast with the low-Qbehaviour where the intensity decreases with increasing pressure. Data treatment for high-Qscattering at different pressures of CO2is also introduced to explain this anomalous behaviour. The analysis shows that a significant proportion of the pore system consists of micropores (<20 Å) and that the majority (80%) of these micropores remain inaccessible to CO2at reservoir pressures.

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45

Ebrahimi, Farzad, i Fateme Mahmoodi. "A modified couple stress theory for buckling analysis of higher order inhomogeneous microbeams with porosities". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 233, nr 8 (12.08.2018): 2855–66. http://dx.doi.org/10.1177/0954406218791642.

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In this paper, buckling behavior of a higher order functionally graded microbeam with porosities is investigated based on the modified couple stress theory and the exact position of the neutral axis. Porosities are evenly and unevenly distributed inside the functionally graded microbeam. Material properties of the functionally graded microbeam are assumed to vary in the thickness direction through a modified form of power-law distribution in which the volume fraction of porosities is considered. The governing equations are derived by using Hamilton's principle and an analytical method is employed to solve these equations for various boundary conditions. The present formulation and numerical results demonstrate a good agreement with some available cases in the literature. Influences of several important parameters such as power-law exponent, porosity distributions, porosity volume fraction, slenderness ratio, and various boundary conditions on buckling loads of porous functionally graded microbeams are investigated and discussed in detail.

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Li, Ang, Liyan Zhang, Jianguo Yang, Shichao Li, Fei Xiao, Yulai Yao, Yiming Huang, Bo Liu i Longsheng Li. "Study on Anisotropic Petrophysical Modeling of Shale: A Case Study of Shale Oil in Qingshankou Formation in Sanzhao Sag, Songliao Basin, China". Geofluids 2023 (27.04.2023): 1–21. http://dx.doi.org/10.1155/2023/6236986.

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Seismic petrophysics is an important link between seismic elastic properties and reservoir physical properties. Based on the petrological and microstructure characteristics of shale in the Qingshankou formation of Sanzhao sag in the north of Songliao Basin, this paper presents an anisotropy petrophysical model with complex pore structure suitable for organic shale constructed with the use of the Voigt-Reuss-Hill average model, an anisotropy self-consistent approximation+differential effective medium model, and the layering of clay and kerogen is simulated by using the Voigt-Reuss-Hill average and bond transform to achieve the simulation of shale anisotropy. Based on the proposed model, the effects of the organic volume fraction, porosity, and pore aspect ratio on rock elastic properties are discussed. The result shows that with the increase of matrix porosity, all elastic parameters show a decreasing trend; with the increase of the organic volume fraction, except shear modulus, other elastic parameters show an increasing trend. Through comparative analysis, the elastic parameters (Lamé impedance and Shear impedance) sensitive to the organic volume fraction and porosity are optimized; the seismic petrophysical cross-plot template with core calibration is constructed. The application shows that the predicted S-wave velocity based on the proposed model is in good agreement with the S-wave velocity derived from dipole source logging. Combined with the high-precision prestack elastic parameter inversion, the “sweet spot” characteristics can be well described, and the research could contribute to a better “sweet spot” description and provide a better support for shale exploration in Sanzhao sag.

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Kim, Woo Chan Ethan, Seung Yong Yang i Noh Yu Kim. "Ultrasonic Estimation of Volume Fraction of Kelvin Structure Using Micro-Structural Model". Applied Mechanics and Materials 864 (kwiecień 2017): 218–23. http://dx.doi.org/10.4028/www.scientific.net/amm.864.218.

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A quantitative ultrasound (QUS) method is developed for estimation of volume fraction of porous Kelvin structure to understand acoustic characteristics of trabecular bone. A Kelvin cellular specimen composed of isotropic tetra-kaidecahedron was produced by 3D printer with ABS plastic material to simulate artificial trabecular bone. The unit cell of Kelvin specimen has a size of 3.4mm and 81% of porosity. The specimen was completely filled with paraffin wax as a substitute of bone marrow. The speed of sound (SOS) of the wax-filled Kelvin specimen was measured using the time-of-flight (TOF) of ultrasound. Based on micro-structural model, shape parameters of Kelvin specimen is correlated with SOS and elastic constant to evaluate volume fraction of the specimen quantitatively. 25.8% of volume fraction was estimated for the Kelvin specimen which has actual volume fraction of 19%. It is concluded from experiment that the ultrasonic method developed in this study is effective and can be applied to diagnose and monitor osteoporosis.

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Pak, J., i O. A. Plumb. "Melting in a Two-Component Packed Bed". Journal of Heat Transfer 119, nr 3 (1.08.1997): 553–59. http://dx.doi.org/10.1115/1.2824139.

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The melting of a multi-component mixture that consists of melting and nonmelting components is examined. A numerical solution is obtained by solving the energy equation and continuity equations for both solid and liquid phases for a one-dimensional system. Both constant volume and constant porosity melting models are explored. Experiments were conducted to confirm the numerical results. During the experiments, heat was applied at the bottom of a rectangular packed bed containing salol (benzoic acid 2-hydroxyphenylester) and glass beads. The experiments were conducted with various sizes of glass beads ranging from 120 μm to 450 μm in diameter with salol having an average diameter of 90 μm. During the melting process, the volume fraction of the phase-change material (salol), temperature, and applied heat flux were measured. The volume fraction of the salol was measured utilizing gamma attenuation. Upon melting, the salol moves as two fronts, one downward due to gravity and one upward due to capillary action. The constant porosity model yields results which compare well with the experimental data.

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Gácsi, Zoltán, C. Hakan Gür, Andrea Makszimus i Tadeusz Pieczonka. "Investigation of Microstructure Inhomogeneity in SiC_p-Reinforced Aluminum Matrix Composites". Materials Science Forum 534-536 (styczeń 2007): 901–4. http://dx.doi.org/10.4028/www.scientific.net/msf.534-536.901.

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The type, volume fraction, size, shape and arrangement of embedded particles influence the mechanical properties of the particle reinforced metal matrix composites. This presents the investigation of the SiC particle and porosity distributions in various aluminum matrix composites produced by cold- and hot-pressing. The microstructures were characterized by optical microscopy and stereological parameters. SiC and porosity volume fractions, and the anisotropy distribution function were measured to establish the influence of the consolidation method. The results showed that SiC particles are arranged in a different way during the cold- and hot pressing. The amount of porosity in the hot pressed specimens is always lower than that in the cold pressed ones; however, cold pressed and sintered samples have few large pores whereas more fine pores develop in the hot pressed ones. In the cold pressed specimens, heating rate for sintering influences the final density, the amount of porosity increases parallel to the increase in the relative particle size; and coating of SiC particles with Cu lowers the porosity while Ni-coating does not result in such an effect.

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Ferreira, S. C., Alexandre Velhinho, L. A. Rocha i Francisco Manuel Braz Fernandes. "Microstructure Characterization of Aluminium Syntactic Functionally Graded Composites Containing Hollow Ceramic Microspheres Manufactured by Radial Centrifugal Casting". Materials Science Forum 587-588 (czerwiec 2008): 207–11. http://dx.doi.org/10.4028/www.scientific.net/msf.587-588.207.

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Syntactic functionally graded metal matrix composites (SFGMMC) are a class of metallic foams in which closed porosity results from the presence of hollow ceramic microspheres (microballoons), whose spatial distribution varies continuously between the inner and the outer section of the part, thus resulting in a continuous variation in properties. In this work, aluminiumbased SFGMMC rings were fabricated by radial centrifugal casting. The graded composition along the radial direction is controlled mainly by the difference in the centrifugal forces which act on the molten metal matrix and the ceramic particles, due to their dissimilar densities. In this case where the density of the SiO2-Al2O3 microballoons is lower than that of molten aluminium, the particles show a tendency to remain closer to the inner periphery of the ring. Thus the microballoon volume fraction increases along the radial direction of the ring from the outer to the inner periphery; in other words, the particle-rich zone is limited to an inner layer of the ring. Precursor conventional MMCs were prepared by stir-casting from the constituent materials, by homogeneously dispersing commercial SiO2-Al2O3 microballoons (particle size: 50 µm; particle volume fraction: 5 and 10 %) within a molten commercial Al-7Si-0.3Mg (A356) alloy. The resulting MMCs were then re-melt and centrifugally cast in order to produce the functionally graded composites. Particle gradients in the centrifugally cast composites were investigated by quantitative image analysis of optical micrographs (for the estimation of the particle volume fraction, mean particle diameter and porosity volume fraction).

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