• Steel and Composite Structures
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• v.43 no.1
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• pp.129-137
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• 2022

Dynamic response of a laminated porous concrete beam reinforced by nanoparticles subjected to harmonic transverse dynamic load is investigated considering structural damping. The effective nanocomposite properties are evaluated on the basis of Mori-Tanaka model. The concrete beam is modeled by the sinusoidal shear deformation theory (SSDT). Utilizing nonlinear strains-deflection, energy relations and Hamilton's principal, the governing final equations of the concrete laminated beam are calculated. Utilizing differential quadrature method (DQM) as well as Newmark method, the dynamic displacement of the concrete laminated beam is discussed. The influences of porosity parameter, nanoparticles volume percent, agglomeration of nanoparticles, boundary condition, geometrical parameters of the concrete beam and harmonic transverse dynamic load are studied on the dynamic displacement of the laminated structure. Results indicated that enhancing the nanoparticles volume percent leads to decrease in the dynamic displacement about 63%. In addition, with considering porosity of the concrete, the dynamic displacement enhances about 2.8 time.

• Advances in materials Research
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• v.12 no.2
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• pp.133-159
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• 2023

In this paper, a size-dependent dynamic investigation of a porous metal foams microbeamsis presented. The novelty of this study is to use a metal foam microbeam that contain porosities based on the refined high order shear deformation beam model, with sinusoidal shear strain function, and the modified strain gradient theory (MSGT) for the first time. The Lagrange's principle combined with differential quadrature hierarchicalfinite element method (DQHFEM) are used to obtain the porous microbeam governing equations. The solutions are presented for the natural frequencies of the porous and homogeneoustype microbeam. The obtained results are validated with the analytical methods found in the literature, in order to confirm the accuracy of the presented resolution method. The influences of the shape of porosity distribution, slenderness ratio, microbeam thickness, and porosity coefficient on the free vibration of the porous microbeams are explored in detail. The results of this paper can be used in various design formetallic foammicro-structuresin engineering.

• Structural Engineering and Mechanics
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• v.88 no.6
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• pp.551-567
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• 2023

In this work, the free vibration analysis of functionally graded material (FGM) sandwich plates with porosity is conducted using the p-version of the finite element method (FEM), which is based on the first-order shear deformation theory (FSDT). The sandwich plate consists of two face-sheet layers of FGM and a homogeneous core layer. The obtained results are validated using convergence and comparison studies with previously published results. Five porosities distribution models of FGM sandwich plates are assumed and analyzed. The effect of the thickness ratio, boundary conditions, volume fraction exponents, and porosity coefficients of the top and bottom layers of FGM sandwich plates on the natural frequency are addressed.

• Journal of Korea Foundry Society
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• v.21 no.3
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• pp.163-178
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• 2001

The squeeze infiltration process is potentially of considerable industrial importance. The performance enhancements resulting from incorporation of short alumina fiber into aluminum are well documented. These are particularly significant for certain automobile components. Aluminum matrix composite automotive parts, such as diesel engine pistons or engine blocks are produced using squeeze casting apparatus or pressure die-casting apparatus. But the solidification process gets complicated with manufacturing parameters and the factors for porosity formation have not fully understood yet. In this study the formation of porosity during squeeze infiltration has been studied experimentally to achieve an improved understanding of the squeeze infiltration process for manufacture of short-fiber-reinforced components, particularly the mechanism of porosity formation. Al-based MMCs produced under a range of conditions were examined metallographically and the porosity characterised;a kind of matrix, an initial temperature of melt, and a volume fraction of reinforcement. The densimetry and the microscopic image analysis were done to measure the amount of porosity. A correlation between manufacturing parameters and defects was investigated through these.

• Special Issue of the Society of Naval Architects of Korea
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• 2006.09a
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• pp.128-133
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• 2006

Generally, porosity which was formed by pyrolysis of the primer is usually generated in the weld metal in respect of increase of the welding speed. in order to analyze the cause of porosity generation, this study was performed using FCAW(flux cored arc welding) process for three kinds of inorganic.zinc primer. in addition the evaluation by influence of welding method on porosity generation is conducted to compare between FCAW and MAG(metal active gas) welding with the same inorganic zinc primer. As the result of this investigation, not only primer of lower organic binder and zinc but also FCAW process than MAG in fillet welding have been verified the excellent resistance to the porosity generation for horizontal fillet welding.

• Journal of Powder Materials
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• v.9 no.1
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• pp.50-60
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• 2002

SPS(Spark Plasma Sintering ) is known to be an excellent sintering method for porous materials. In the present work an attempt has been made of fabricating porous 316L Stainless steel with good mechanical properties by using controlled SPS process Porosity was 21%~53% at sintering temperature of $600^{\circ}C$~100$0^{\circ}C$ The limit of porosity with available mechanical strength was 30% at given experimental conditions. Porosity can be controlled by manipulating the intial height of the compact by means of the supporter and punch length. The applied pressure can be exerted entirely upon the supporter, giving no influence on the specimen. The specimen is then able to be sintered pressurelessly. In this case porosity could be controlled from 38 to 45% with good mechanical strength at sintering temperature of 90$0^{\circ}C$. As the holding time increased, neck between the particles grew progressively, but shrinkage of the specimen did not occur, implying that the porosity remained constant during the whole sintering process.

• Earthquakes and Structures
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• v.10 no.6
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• pp.1429-1449
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• 2016

The effect of porosity on bending and free vibration behavior of simply supported functionally graded plate reposed on the Winkler-Pasternak foundation is investigated analytically in the present paper. The modified rule of mixture covering porosity phases is used to describe and approximate material properties of the FGM plates with porosity phases. The effect due to transverse shear is included by using a new refined shear deformation theory. The number of unknown functions involved in the present theory is only four as against five or more in case of other shear deformation theories. The Poisson ratio is held constant. Based on the sinusoidal shear deformation theory, the position of neutral surface is determined and the equation of motion for FG rectangular plates resting on elastic foundation based on neutral surface is obtained through the minimum total potential energy and Hamilton's principle. The convergence of the method is demonstrated and to validate the results, comparisons are made with the available solutions for both isotropic and functionally graded material (FGM). The effect of porosity volume fraction on Al/Al2O3 and Ti-6Al-4V/Aluminum oxide plates are presented in graphical forms. The roles played by the constituent volume fraction index, the foundation stiffness parameters and the geometry of the plate is also studied.

• Steel and Composite Structures
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• v.47 no.5
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• pp.633-644
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• 2023

Taking a look at the previously published papers, it is revealed that there is a porosity index limitation (around 0.35) for the mechanical behavior analysis of the functionally graded porous (FGP) structures. Over mentioned magnitude of the porosity index, the elastic modulus falls below zero for some parts of the structure thickness. Therefore, the current paper is presented to analyze the vibrational behavior of the FGP Timoshenko beams (FGPTBs) using a novel refined formulation regardless of the porosity index magnitude. The silica aerogel foundation and various hydrothermal loadings are assumed as the source of external forces. To obtain the FGPTB's properties, the power law is hired, and employing Hamilton's principle in conjunction with Navier's solution method, the governing equations are extracted and solved. In the end, the impact of the various variables as different beam materials, elastic foundation parameters, and porosity index is captured and displayed. It is revealed that changing hygrothermal loading from non-linear toward uniform configuration results in non-dimensional frequency and stiffness pushing up. Also, Al - Al2O3 as the material composition of the beam and the porosity presence with the O pattern, provide more rigidity in comparison with using other materials and other types of porosity dispersion. The presented computational model in this paper hopes to help add more accuracy to the structures' analysis in high-tech industries.

• Journal of the Korean Geotechnical Society
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• v.40 no.4
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• pp.127-135
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• 2024

The purpose of this paper is to establish the relationship between compression wave velocity and porosity in unsaturated soil using a deep neural network (DNN) algorithm. Input parameters were examined using the error norm method to assess their impact on porosity. Compression wave velocity was conclusively found to have the most significant influence on porosity estimation. These parameters were derived through both field and laboratory experiments using a total of 266 numerical data points. The application of the DNN was evaluated by calculating the mean squared error loss for each iteration, which converged to nearly zero in the initial stages. The predicted porosity was analyzed by splitting the data into training and validation sets. Compared with actual data, the coefficients of determination were exceptionally high at 0.97 and 0.98, respectively. This study introduces a methodology for predicting dependent variables through error norm analysis by disregarding fewer sensitive factors and focusing on those with greater influence.

• Advances in nano research
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• v.14 no.4
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• pp.375-389
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• 2023

In this study, free vibration analysis of functionally graded (FG) porous truncated conical shell panels reinforced by graphene platelets (GPLs) has been investigated for the first time. Additionally, the effect of three different types of porosity distribution and five different types of GPLs patterns on dynamic response of the shell are also studied. Halpin-Tsai micromechanical model and Voigt's rule are used to determine Young modulus, shear modulus and Poisson's ratio with mass densities of the shell, respectively. The main novelties of present study are: applying 3D elasticity theory and the finite element method in conjunction with Rayleigh-Ritz method to give more accurate results unlike other simplified shell theories, and also presenting a general 3D solution in cylindrical coordinate system that can be used for analyses of different structures such as circular, annular and annular sector plates, cylindrical shells and panels, and conical shells and panels. A convergence study is performed to justify the correctness of the obtained solution and numerical results. The impact of porosity and GPLs patterns, the volume of voids, the weight fraction of graphene nanofillers, semi vertex and span angles of the cone, and various boundary conditions on natural frequencies of the functionally graded panel have been comprehensively studied and discussed. The results show that the most important parameter on dynamic response of FG porous truncated conical panel is the weight fraction of nanofiller and adding 1% weight fraction of nanofiller could increase 57% approximately the amounts of natural frequencies of the shell. Moreover, the porosity distribution has great effect on the value of natural frequency of structure rather than the porosity coefficient.