Shahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-947510220200621Calculation of springback with considering of hardening laws in the cold roll forming process of the steel plateCalculation of springback with considering of hardening laws in the cold roll forming process of the steel plate110185810.22044/jsfm.2020.8358.2899FAJ.NaofalMech. Eng.,Tarbiat Modares Univ., Tehran, IranH.Moslemi NaeiniAcademic staffS.MazdakTafresh university engineering facultyJournal Article20190429springback is one of the challenges in the final shape of the steel in the cold roll forming process of the steel plate.The precision of the simulation of metal sheet forming processes for prediction of the springback depends on the stress-strain relationship, the yield function and the selected hardening model and the anisotropy of the material. In this paper, using alternating tension-compression experiment and using simulation in software LS-OPT, the variables of the Yoshida-Uemori hardening model have been obtained for St37 steel. Springback in the final shape of steel plate deformation is a challenge of the roll forming process. Since consideration of the hardening law is important in the springback, various models of hardening law are proposed for more accurate prediction of material behavior. One of the most accurate models in predicting metal behavior is the Yoshida-Uemori hardening model. The experimental tests were also carried out as well as the simulations in the Ls-dyna simulation software with and without Yoshida-Umari hardening. It was shown that the prediction of springback with using the Yoshida-Umari model was more accurate.springback is one of the challenges in the final shape of the steel in the cold roll forming process of the steel plate.The precision of the simulation of metal sheet forming processes for prediction of the springback depends on the stress-strain relationship, the yield function and the selected hardening model and the anisotropy of the material. In this paper, using alternating tension-compression experiment and using simulation in software LS-OPT, the variables of the Yoshida-Uemori hardening model have been obtained for St37 steel. Springback in the final shape of steel plate deformation is a challenge of the roll forming process. Since consideration of the hardening law is important in the springback, various models of hardening law are proposed for more accurate prediction of material behavior. One of the most accurate models in predicting metal behavior is the Yoshida-Uemori hardening model. The experimental tests were also carried out as well as the simulations in the Ls-dyna simulation software with and without Yoshida-Umari hardening. It was shown that the prediction of springback with using the Yoshida-Umari model was more accurate.https://jsfm.shahroodut.ac.ir/article_1858_1f5e16b48e9f651260147221e3bde0c6.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-947510220200621A study on plastic response of circular plates under uniformly and locally distributed dynamic loadingA study on plastic response of circular plates under uniformly and locally distributed dynamic loading1127185910.22044/jsfm.2020.9264.3091FAT.Mirzababaie MostofiFaculty of Mechanical Engineering, University of EyvanekeyM.Sayah BadkhorFaculty of Mechanical Engineering, University of Eyvanekey , Eyvanekey, IranH.BabaeiFaculty of Mechanical Engineering, University of GuilanJournal Article20200107In this paper, a non-dimensional analysis approach has been used to propose three empirical equations based on dimensionless numbers to predict the maximum transverse permanent deflection-thickness ratio of single-layered circular plates under uniformly and locally distributed dynamic loading. The effect of plate geometry, the impulse of applied load, mechanical properties of the plate, the strain-rate sensitivity, the load radius, and the stand-off distance was considered. In order to validate the empirical models, fourteen series of conducted experiments and 562 data points in the state of the art over the past forty years have been used. The obtained results showed good agreement between the model prediction results and the experimental values so that in total 338 experimental data for uniform loading, 75% (255 data) and 94% (318 data) of the data points were distributed in the ±10% and ±20% error range, respectively. In addition, in total 108 experimental data for localized loading without using stand-off distance, 59% (64 data) and 92% (99 data) of data points were distributed in these two ranges, respectively. For the localized loading using the stand-off distance, 68% (79 data out of 116) and 94% (99 data out of 116) of the data points were distributed in the ±10% and ±20% error range, respectively.In this paper, a non-dimensional analysis approach has been used to propose three empirical equations based on dimensionless numbers to predict the maximum transverse permanent deflection-thickness ratio of single-layered circular plates under uniformly and locally distributed dynamic loading. The effect of plate geometry, the impulse of applied load, mechanical properties of the plate, the strain-rate sensitivity, the load radius, and the stand-off distance was considered. In order to validate the empirical models, fourteen series of conducted experiments and 562 data points in the state of the art over the past forty years have been used. The obtained results showed good agreement between the model prediction results and the experimental values so that in total 338 experimental data for uniform loading, 75% (255 data) and 94% (318 data) of the data points were distributed in the ±10% and ±20% error range, respectively. In addition, in total 108 experimental data for localized loading without using stand-off distance, 59% (64 data) and 92% (99 data) of data points were distributed in these two ranges, respectively. For the localized loading using the stand-off distance, 68% (79 data out of 116) and 94% (99 data out of 116) of the data points were distributed in the ±10% and ±20% error range, respectively.https://jsfm.shahroodut.ac.ir/article_1859_e45320cec5d79a3c8b90ef5b4ce324ff.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-947510220200621Effect of repair welds on the microstructure and mechanical properties of 9Cr1Mo welding jointEffect of repair welds on the microstructure and mechanical properties of 9Cr1Mo welding joint2944186210.22044/jsfm.2020.9308.3103FAM.VaseghiFaculty of Mechanical and Energy Engineering, Shahid Beheshti University, Tehran, IranS.NazaralizadehFaculty of Mechanical and Energy Engineering, Shahid Beheshti University, Tehran, IranM.SameezadehFaculty of Mechanical and Energy Engineering, Shahid Beheshti University, Tehran, IranJournal Article202001229Cr1Mo steel is widely used in the construction of power plant components. Since performing periodic repairs is one of the most important requirements for industrial use of 9Cr1Mo steel, in the present study, the repair welding of the steel and post-weld heat treatments was carried out and its effect on the mechanical properties and microstructural evolutions after several stages of repair welding was studied. Therefore, a detailed structure-property relationship of weld metal, base metal, and HAZ using optical microscopy, scanning electron microscopy techniques as well as room temperature tensile test, impact test, and microhardness examinations were found. The results showed that there was a direct relationship between the number of welding repairs and the increase in average hardness. Moreover, the hardness gradient in the several welded samples was significantly higher than the one-pass welded sample. On the other hand, post-weld heat treatment operations increased the number of precipitations in the weld metal and HAZ and the size of primary austenite grains in the weld metal and HAZ was more homogeneous.9Cr1Mo steel is widely used in the construction of power plant components. Since performing periodic repairs is one of the most important requirements for industrial use of 9Cr1Mo steel, in the present study, the repair welding of the steel and post-weld heat treatments was carried out and its effect on the mechanical properties and microstructural evolutions after several stages of repair welding was studied. Therefore, a detailed structure-property relationship of weld metal, base metal, and HAZ using optical microscopy, scanning electron microscopy techniques as well as room temperature tensile test, impact test, and microhardness examinations were found. The results showed that there was a direct relationship between the number of welding repairs and the increase in average hardness. Moreover, the hardness gradient in the several welded samples was significantly higher than the one-pass welded sample. On the other hand, post-weld heat treatment operations increased the number of precipitations in the weld metal and HAZ and the size of primary austenite grains in the weld metal and HAZ was more homogeneous.https://jsfm.shahroodut.ac.ir/article_1862_1c270e91c59fd0b0c1ab8467a2da00d4.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-947510220200621Theoretical and experimental analysis of jamming of workpiece in the fixture by using the block and palm studyTheoretical and experimental analysis of jamming of workpiece in the fixture by using the block and palm study4558186310.22044/jsfm.2020.8872.3007FAH.ParvazN.SepehryFaculty of Mechanical and Mechatronics Engineering, Shahrood University of Technology, Shahrood, IranM.Keyhani YazdiFaculty of Mechanical and Mechatronics Engineering, Shahrood University of Technology, Shahrood, IranJournal Article20190901Jamming of workpiece in the fixture is an unwanted phenomenon which usually occurs during its loading or unloading processes. Investigating the conditions of the jamming occurrence and determining the conditions in which jamming would not occur, are considered as the important steps in the verification stage of the fixture design procedure. In this paper, analytical and experimental analysis is conducted for studying the jamming occurrence conditions using the block and palm study. Theoretical model is established based on the minimum norm principle. The proposed theoretical models in the previous studies which investigated the jamming phenomenon in the quasi-static conditions are also incorporated. Experiments are also designed and implemented for validation of the theoretical predictions. For this purpose, experimental setup is designed and fabricated for the block and palm case study. After measurement of the coefficient of friction between the block, base plate and pal, the jamming-in travel of block (distance in which jamming occurred) is then measured using a rotary encoder and the image processing techniques. The worst-case error equal to 6.8mm (equivalent to 3.8%) is obtained for the jamming-in travel of block between the theoretical predictions and experimental results which indicated the accuracy of the suggested theoretical model.Jamming of workpiece in the fixture is an unwanted phenomenon which usually occurs during its loading or unloading processes. Investigating the conditions of the jamming occurrence and determining the conditions in which jamming would not occur, are considered as the important steps in the verification stage of the fixture design procedure. In this paper, analytical and experimental analysis is conducted for studying the jamming occurrence conditions using the block and palm study. Theoretical model is established based on the minimum norm principle. The proposed theoretical models in the previous studies which investigated the jamming phenomenon in the quasi-static conditions are also incorporated. Experiments are also designed and implemented for validation of the theoretical predictions. For this purpose, experimental setup is designed and fabricated for the block and palm case study. After measurement of the coefficient of friction between the block, base plate and pal, the jamming-in travel of block (distance in which jamming occurred) is then measured using a rotary encoder and the image processing techniques. The worst-case error equal to 6.8mm (equivalent to 3.8%) is obtained for the jamming-in travel of block between the theoretical predictions and experimental results which indicated the accuracy of the suggested theoretical model.https://jsfm.shahroodut.ac.ir/article_1863_5db2f337b20782e2d84199d698627e94.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-947510220200621Theoretical and Numerical Analysis of Hot Deep Drawing of Hemispherical Thick HeadTheoretical and Numerical Analysis of Hot Deep Drawing of Hemispherical Thick Head5978186410.22044/jsfm.2020.8960.3031FAM.VahdatiShahrood University of TechnologyM. A.RasooliMalek-AshtarM.GerdooeiShahrood University of TechnologyJournal Article20190927One of the common processes for the head production is welding which is done by joining preformed sheets. Manufactured product due to assembly error, metallurgical defects and weak mechanical strength of the joint, does not have adequate dimensional and mechanical quality. Therefore, the hot deep drawing is an alternative process in order to solve the aforementioned disadvantages due to the production of one-piece head. In the present paper, theoretical and numerical analysis of the manufacture of a hemispherical thick head made of HY-100 alloy steel with a sheet thickness of 63.5 mm using this process with a blank-holder is presented. In this study, the Johnson-Cook constitutive model is used to describe the flow behavior of the material and the Johnson-Cook damage model is used to predict the probability of failure. It is assumed that the process is carried out isothermal and the strain rate is constant. The results of theoretical analysis showed that the drawing force decreases with increasing temperature, decreasing friction, and increasing the radius of the die curvature. On the other hand, the results of the numerical analysis showed that the head was successfully formed. Also, no trace of wrinkling appeared in the flange and the greatest thickness reduction occured in areas near the top of hemisphere. On the other hand, the thickness of areas close to the flange, increases. The comparison between forces showed that drawing force values obtained from theoretical and numerical analysis under different temperatures and friction conditions differed by a maximum of 10%.One of the common processes for the head production is welding which is done by joining preformed sheets. Manufactured product due to assembly error, metallurgical defects and weak mechanical strength of the joint, does not have adequate dimensional and mechanical quality. Therefore, the hot deep drawing is an alternative process in order to solve the aforementioned disadvantages due to the production of one-piece head. In the present paper, theoretical and numerical analysis of the manufacture of a hemispherical thick head made of HY-100 alloy steel with a sheet thickness of 63.5 mm using this process with a blank-holder is presented. In this study, the Johnson-Cook constitutive model is used to describe the flow behavior of the material and the Johnson-Cook damage model is used to predict the probability of failure. It is assumed that the process is carried out isothermal and the strain rate is constant. The results of theoretical analysis showed that the drawing force decreases with increasing temperature, decreasing friction, and increasing the radius of the die curvature. On the other hand, the results of the numerical analysis showed that the head was successfully formed. Also, no trace of wrinkling appeared in the flange and the greatest thickness reduction occured in areas near the top of hemisphere. On the other hand, the thickness of areas close to the flange, increases. The comparison between forces showed that drawing force values obtained from theoretical and numerical analysis under different temperatures and friction conditions differed by a maximum of 10%.https://jsfm.shahroodut.ac.ir/article_1864_2b910ff830fc749854eacbc3a37c1cb3.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-947510220200621Investigation of dynamics and stability behavior of axially moving micro-beams with functionally graded property in the longitudinal directionInvestigation of dynamics and stability behavior of axially moving micro-beams with functionally graded property in the longitudinal direction7994186510.22044/jsfm.2020.8952.3027FAA.ForooghiMechanical Engineering, Tarbiat Modares University, Tehran, IranM.SafarpourMechanical Engineering, Tarbiat Modares University, Tehran, Iran.A.AlibeiglooMechanical Engineering, Tarbiat Modares University, Tehran, IranJournal Article20190925In this paper, in order to improve the efficiency of the moving systems, vibrations and stability of axially functionally graded Rayleigh moving micro-beams are studied. Also, to clarify the influences of various parameters such as axially functionally graded, the length of the material characteristics, and the whirling inertia on the stability boundaries of Rayleigh and Euler-Bernoulli beams, a detailed parametric study is done. It is assumed that the material characteristics of the system change linearly or exponentially in longitudinal direction continuously. To calculate the natural frequencies, dynamics configuration, and divergence and flutter instability thresholds of the system, the strain gradient theory, Galerkin discretization method, and an eigenvalue problem are utilized. In addition, the analytical relations are extracted for the critical velocity of the system. Critical velocity contours and stability maps are examined for different distributions. It is demonstrated that the exponential and linear changes lead to a more stable system in the variable state of density and elastic modulus, respectively. Also, the results indicated that increasing the elastic modulus gradient parameter or decreasing the density gradient parameter results in an increase in the natural frequency of the system and a development in the stability regions. Hence, the alteration in the density and elastic modulus gradient parameters has an opposite role in the dynamic behavior of the system.In this paper, in order to improve the efficiency of the moving systems, vibrations and stability of axially functionally graded Rayleigh moving micro-beams are studied. Also, to clarify the influences of various parameters such as axially functionally graded, the length of the material characteristics, and the whirling inertia on the stability boundaries of Rayleigh and Euler-Bernoulli beams, a detailed parametric study is done. It is assumed that the material characteristics of the system change linearly or exponentially in longitudinal direction continuously. To calculate the natural frequencies, dynamics configuration, and divergence and flutter instability thresholds of the system, the strain gradient theory, Galerkin discretization method, and an eigenvalue problem are utilized. In addition, the analytical relations are extracted for the critical velocity of the system. Critical velocity contours and stability maps are examined for different distributions. It is demonstrated that the exponential and linear changes lead to a more stable system in the variable state of density and elastic modulus, respectively. Also, the results indicated that increasing the elastic modulus gradient parameter or decreasing the density gradient parameter results in an increase in the natural frequency of the system and a development in the stability regions. Hence, the alteration in the density and elastic modulus gradient parameters has an opposite role in the dynamic behavior of the system.https://jsfm.shahroodut.ac.ir/article_1865_2cce07ab8b1c57f6492f89089fde40c2.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-947510220200621Experimental, numerical and analytical study of energy absorbtion in drop weight tear test specimen with chevron notch on API X65 steelExperimental, numerical and analytical study of energy absorbtion in drop weight tear test specimen with chevron notch on API X65 steel95110186710.22044/jsfm.2020.9440.3129FAE.FathiUniversity of Birjand
Department of Mechanical EngineeringSayyed H.HashemiJournal Article20200304Drop weight tear test (DWTT) is a common experiment to determine the dynamic properties and evaluate the fracture energy of steel specimens. The purpose of present research is presenting experimental, numerical and analytical methods for determination energy transferred to the specimen during impact. Test specimen was cut from an actual spiral seam welded steel pipe with an outside diameter of 1219mm and wall thickness of 14.3mm and then machined to standard size. Then chevron notch was placed in the middle of specimen and test sample was fractured under dynamic loading with initial impact velocity of 6.3m/s. Experiment was impelemented on three specimens by dropping the impactor from 2m height. By drawing and analyzing the energy-displacement and energy-velocity diagrams a linear relation between fracture energy and hammer velocity was. Using this relation by having the impactor velocity in each time, one could evaluate the transferred energy to the specimen and finally the fracture energy of tested specimen. Also, using kinetic energy and potential energy formula by knowing the hammer location and velocity in each time and by neglecting energy losses one could calculate the absorbed energy in the specimenDrop weight tear test (DWTT) is a common experiment to determine the dynamic properties and evaluate the fracture energy of steel specimens. The purpose of present research is presenting experimental, numerical and analytical methods for determination energy transferred to the specimen during impact. Test specimen was cut from an actual spiral seam welded steel pipe with an outside diameter of 1219mm and wall thickness of 14.3mm and then machined to standard size. Then chevron notch was placed in the middle of specimen and test sample was fractured under dynamic loading with initial impact velocity of 6.3m/s. Experiment was impelemented on three specimens by dropping the impactor from 2m height. By drawing and analyzing the energy-displacement and energy-velocity diagrams a linear relation between fracture energy and hammer velocity was. Using this relation by having the impactor velocity in each time, one could evaluate the transferred energy to the specimen and finally the fracture energy of tested specimen. Also, using kinetic energy and potential energy formula by knowing the hammer location and velocity in each time and by neglecting energy losses one could calculate the absorbed energy in the specimenhttps://jsfm.shahroodut.ac.ir/article_1867_c71dcc18ea7723d2acc71fbf557fa293.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-947510220200621Non-linear analysis of FG beam-based double-movable-electrode MEMSNon-linear analysis of FG beam-based double-movable-electrode MEMS111126186810.22044/jsfm.2020.9137.3069FAH. A.Aalam HakkakanDepartment of Mechanical Engineering, Engineering faculty, Hakim Sabzevari University, Sabzevar, IranA. R.AskariDepartment of Mechanical Engineering, Engineering Faculty, Hakim Sabzevari University, Sabzevar, IranJournal Article20191204The objective of the present paper is to investigate the static and dynamic responses of geometric non-linear micro-beams, which are made of functionally graded materials, in double-movable-electrode micro-electro-mechanical systems (MEMS). To do so, employing the non-linear strain-displacement relation in such structures based on the von Kármán theory, the governing equations of motion have been obtained by Hamilton’s principle and then solved through the Galerkin weighted residual method. The static and dynamic findings of the present work have been verified by those available in the literature for single-movable-electrode systems. The present static and dynamic results for double-movable-electrode systems have also been compared and successfully validated by those obtained through 3-D finite element simulations carried out in COMSOL commercial software. At the rest of the paper, aside from the influence of the movability of both electrodes, the inertia and material graduation effects on the non-linear response of the system have been investigated. The results reveal that the movability of both electrodes drastically reduces the pull-in voltage of the system.The objective of the present paper is to investigate the static and dynamic responses of geometric non-linear micro-beams, which are made of functionally graded materials, in double-movable-electrode micro-electro-mechanical systems (MEMS). To do so, employing the non-linear strain-displacement relation in such structures based on the von Kármán theory, the governing equations of motion have been obtained by Hamilton’s principle and then solved through the Galerkin weighted residual method. The static and dynamic findings of the present work have been verified by those available in the literature for single-movable-electrode systems. The present static and dynamic results for double-movable-electrode systems have also been compared and successfully validated by those obtained through 3-D finite element simulations carried out in COMSOL commercial software. At the rest of the paper, aside from the influence of the movability of both electrodes, the inertia and material graduation effects on the non-linear response of the system have been investigated. The results reveal that the movability of both electrodes drastically reduces the pull-in voltage of the system.https://jsfm.shahroodut.ac.ir/article_1868_50aa84ea18f3b48c6e66aa820553ef14.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-947510220200621Free vibration of rotating FGM conical shell with smart patchesFree vibration of rotating FGM conical shell with smart patches127140186910.22044/jsfm.2020.9504.3143FAM.JafariniasarA. AJafariProfessor of KNT UniversityM.Irani RahagiDepartment of Solid Mechanics, Faculty of Mechanical Engineering, University of KashanJournal Article20200410In this paper, free vibrations of rotating conical shell with smart patches are investigated. Shell is considered as a thin-wall and equations of motion are obtained from the energy method. Patches are in pairs on the inner and outer shell and play role of sensor and actuator in control of the system. Number of these patches are four. Using classical theory, Love strain- displacement relations, stress-strain relations, and guessed answer with known Location functions and unknown time functions, and Lagrange equation, governing equation of motion as ODE are obtained. The benefit of this method is the non-use of Hamilton's principle and get involved in differentiation and partial integrals. Natural frequencies with and without smart patches in two boundary conditions are compared with results of previous studies and then effect of angular velocity, patches area, boundary conditions and non-homogeneous index of both functionally graded material (shell and smart material) on natural frequency are investigated.In this paper, free vibrations of rotating conical shell with smart patches are investigated. Shell is considered as a thin-wall and equations of motion are obtained from the energy method. Patches are in pairs on the inner and outer shell and play role of sensor and actuator in control of the system. Number of these patches are four. Using classical theory, Love strain- displacement relations, stress-strain relations, and guessed answer with known Location functions and unknown time functions, and Lagrange equation, governing equation of motion as ODE are obtained. The benefit of this method is the non-use of Hamilton's principle and get involved in differentiation and partial integrals. Natural frequencies with and without smart patches in two boundary conditions are compared with results of previous studies and then effect of angular velocity, patches area, boundary conditions and non-homogeneous index of both functionally graded material (shell and smart material) on natural frequency are investigated.https://jsfm.shahroodut.ac.ir/article_1869_f8fb19b1099a255ebfa61959d5f6335d.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-947510220200621Layered finite element analysis of laminated composite plates by using unsymmetric membrane element and non-conforming bending elementLayered finite element analysis of laminated composite plates by using unsymmetric membrane element and non-conforming bending element141152187010.22044/jsfm.2020.9230.3085FAH.SangtarashCivil Engineering, Sistan and Baluchestan University, Zahedan, Iran.H.Ghohani ArabCivil Engineering, Sistan and Baluchestan University, Zahedan, Iran.M. RSohrabiCivil Engineering, Sistan and Baluchestan University, Zahedan, Iran.M.R.GhasemiCivil Engineering, Sistan and Baluchestan University, Zahedan, Iran.Journal Article20191227This study presents a new quadrilateral element for layered finite element analysis of laminated composite plates which is obtained through assemblage of membrane and plate bending elements. The membrane component is a new unsymmetric quadrilateral element with drilling degrees of freedom, in which two different types of displacement fields are used as the test and trial functions. The test function is a new kind of displacement field with drilling degrees of freedom obtained by using interpolation along the element edges. The trial function is a stress field computed through analytical solutions of Airy stress function. The bending component of lroposed element is a non-conforming plate element that its displacement is computed using third-order deformation modes and the rotational field of element is defined by using first-order Jacobean matrix. The results of numerical benchmark problems show that the the proposed element is capable for analysis of laminated composite plates with varius geometry and boundary. The maximum error of the proposed element among the considered numerical problems is only 1.5 percent.This study presents a new quadrilateral element for layered finite element analysis of laminated composite plates which is obtained through assemblage of membrane and plate bending elements. The membrane component is a new unsymmetric quadrilateral element with drilling degrees of freedom, in which two different types of displacement fields are used as the test and trial functions. The test function is a new kind of displacement field with drilling degrees of freedom obtained by using interpolation along the element edges. The trial function is a stress field computed through analytical solutions of Airy stress function. The bending component of lroposed element is a non-conforming plate element that its displacement is computed using third-order deformation modes and the rotational field of element is defined by using first-order Jacobean matrix. The results of numerical benchmark problems show that the the proposed element is capable for analysis of laminated composite plates with varius geometry and boundary. The maximum error of the proposed element among the considered numerical problems is only 1.5 percent.https://jsfm.shahroodut.ac.ir/article_1870_468a611bb4e73c282a538272d786eddf.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-947510220200621The investigation of microstructure and mechanical properties of metallic glass/ceramic reinforced hybrid Al matrix composite used as foam precursor materialThe investigation of microstructure and mechanical properties of metallic glass/ceramic reinforced hybrid Al matrix composite used as foam precursor material153162187110.22044/jsfm.2020.9130.3067FAM. R.RezaeiSchool of engineering, Damghan university, DamghanA.R.AlbooyehSchool of Engineering, Damghan university, DamghanM.ShayestefarSchool of Engineering, Damghan University, Damghan, IranH.ShiraghaeiSchool of Engineering, Damghan University, Damghan, IranJournal Article20191204In this study, Al matrix hybrid composites reinforced with amorphous/ceramic particles have been produced via powder metallurgy process. Pure aluminum powder particles were blended with various volume fractions of TiH2 and amorphous Fe75Si15B5Zr5 particles. Blended powders were then consolidated through spark plasma sintering (SPS). The microstructure, phase evolution and mechanical properties of composites were examined. Microstructural investigations indicated that the reinforcing particles were segregated along the grain boundaries and mean grain sizes were decreased by increasing the amorphous particles content. Also, increasing the volume fraction of reinforcements had negligible effect on the porosity content of composites. Phase investigations revealed the presence of amorphous phase in the XRD patterns and absence of any undesirable matrix/reinforcement interfacial products. Compared to composite without amorphous reinforcements, the yield strength and hardness of composites contain 15 vol. % of amorphous particles and 1 vol. % of TiH2 particles were enhanced for 35% and 20%, respectively.In this study, Al matrix hybrid composites reinforced with amorphous/ceramic particles have been produced via powder metallurgy process. Pure aluminum powder particles were blended with various volume fractions of TiH2 and amorphous Fe75Si15B5Zr5 particles. Blended powders were then consolidated through spark plasma sintering (SPS). The microstructure, phase evolution and mechanical properties of composites were examined. Microstructural investigations indicated that the reinforcing particles were segregated along the grain boundaries and mean grain sizes were decreased by increasing the amorphous particles content. Also, increasing the volume fraction of reinforcements had negligible effect on the porosity content of composites. Phase investigations revealed the presence of amorphous phase in the XRD patterns and absence of any undesirable matrix/reinforcement interfacial products. Compared to composite without amorphous reinforcements, the yield strength and hardness of composites contain 15 vol. % of amorphous particles and 1 vol. % of TiH2 particles were enhanced for 35% and 20%, respectively.https://jsfm.shahroodut.ac.ir/article_1871_9959adb780cdbc442c7775d2f04d4188.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-947510220200621Study of Primary and Secondary Nonlinear Resonances of Nanobeam Based on Nonlocal Strain Gradient TheoryStudy of Primary and Secondary Nonlinear Resonances of Nanobeam Based on Nonlocal Strain Gradient Theory163175187210.22044/jsfm.2020.8274.2878FAH.KaramadM. Sc. Student, Mech Eng, Quchan University of Technology, Quchan, IranA.AndakhshidehAssis Prof, Mech Eng, Quchan University of Technology, Quchan, IranS.MalekiAssis Prof, Mech Eng, Quchan University of Technology, Quchan, IranJournal Article20190409In this paper, the nonlinear forced vibrations of nonlocal Euler-Bernoulli nanobeam that is utilized in nanoelectromechanical systems are studied using the analytical method of multiple time scales. Based on non-linear strain gradient elasticity theory, governing equation of Euler-Bernoulli nanobeam with von-karman geometric nonlinearity is derived using Hamilton principle. In the next step, using the Galerkin method, the partial differential governing equations for simply supported boundary conditions are reduced to time variable ordinary nonlinear differential equation. Subsequently, the nonlinear forced vibration equation is solved using a multiple time scalar method. After solving the nonlinear excited equation, primary and secondary resonances of nonlocal nanobeam are studied. The region of acceptable sub-harmonic responses is identified and for different values of nonlocal parameter, the frequency response curves and response amplitudes versus excitation amplitude is plotted in all resonances as primary, super-harmonic and sub-harmonic. These results show that using nonlocal strain gradient theory is a fundamental necessity for analyzing nonlinear vibration of nanobeams. The results of this paper can be used to improve the design and optimization of nanoelectromechanical systems.In this paper, the nonlinear forced vibrations of nonlocal Euler-Bernoulli nanobeam that is utilized in nanoelectromechanical systems are studied using the analytical method of multiple time scales. Based on non-linear strain gradient elasticity theory, governing equation of Euler-Bernoulli nanobeam with von-karman geometric nonlinearity is derived using Hamilton principle. In the next step, using the Galerkin method, the partial differential governing equations for simply supported boundary conditions are reduced to time variable ordinary nonlinear differential equation. Subsequently, the nonlinear forced vibration equation is solved using a multiple time scalar method. After solving the nonlinear excited equation, primary and secondary resonances of nonlocal nanobeam are studied. The region of acceptable sub-harmonic responses is identified and for different values of nonlocal parameter, the frequency response curves and response amplitudes versus excitation amplitude is plotted in all resonances as primary, super-harmonic and sub-harmonic. These results show that using nonlocal strain gradient theory is a fundamental necessity for analyzing nonlinear vibration of nanobeams. The results of this paper can be used to improve the design and optimization of nanoelectromechanical systems.https://jsfm.shahroodut.ac.ir/article_1872_39514be66c1dbb703dfcff5da5ca6a1a.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-947510220200621Uncertainty quantification of the turbulent flow field and heat transfer of film coolingUncertainty quantification of the turbulent flow field and heat transfer of film cooling177192187310.22044/jsfm.2020.8750.2982FAA.Mohammadi-AhmarDepartment of Mechanical Engineering, University of Tehran, Tehran, Iran.S.SalehiDepartment of Mechanical Engineering, University of Tehran, Tehran, Iran.M.RaiseeDepartment of Mechanical Engineering, University of Tehran, Tehran, Iran.Journal Article20190730In the present paper, Uncertainty Quantification (UQ) of the turbulent flow field and heat transfer of film cooling is investigated. For this end, two stochastic flow and heat transfer parameters, namely, the Reynolds number (Re) and the turbulent Prandtl number (Pr_t) with the uniform Probability Distribution Functions (PDFs), along with six stochastic film cooling parameters, namely, the blowing ratio (M), the density ratio (DR), the turbulent intensity and the length scales of mainstream and coolant flow (I_h,I_c,L_h,L_c) all with the Beta PDF are considered. To quantify uncertainty in different flow conditions, UQ analysis is firstly investigated in the low blowing ratio (i.e., M=0.5) and then in the high blowing ratio (i.e., M=2). The uncertainties are propagated in the turbulent flow field and heat transfer using the Non-Intrusive Polynomial Chaos Expansion (NIPCE) method with polynomial order p=3. The non-deterministic CFD results show that considering stochastic conditions yield to a significant effect on the film cooling effectiveness. In addition, among the considered random parameters, the uncertain variables of Re, DR and M mostly influence the cooling effectiveness. While the remaining of random parameters (i.e. I_h,I_c,L_h and L_c) show a negligible effect.In the present paper, Uncertainty Quantification (UQ) of the turbulent flow field and heat transfer of film cooling is investigated. For this end, two stochastic flow and heat transfer parameters, namely, the Reynolds number (Re) and the turbulent Prandtl number (Pr_t) with the uniform Probability Distribution Functions (PDFs), along with six stochastic film cooling parameters, namely, the blowing ratio (M), the density ratio (DR), the turbulent intensity and the length scales of mainstream and coolant flow (I_h,I_c,L_h,L_c) all with the Beta PDF are considered. To quantify uncertainty in different flow conditions, UQ analysis is firstly investigated in the low blowing ratio (i.e., M=0.5) and then in the high blowing ratio (i.e., M=2). The uncertainties are propagated in the turbulent flow field and heat transfer using the Non-Intrusive Polynomial Chaos Expansion (NIPCE) method with polynomial order p=3. The non-deterministic CFD results show that considering stochastic conditions yield to a significant effect on the film cooling effectiveness. In addition, among the considered random parameters, the uncertain variables of Re, DR and M mostly influence the cooling effectiveness. While the remaining of random parameters (i.e. I_h,I_c,L_h and L_c) show a negligible effect.https://jsfm.shahroodut.ac.ir/article_1873_e2708b0e7b2e655e85ac1d92d0bfb9e2.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-947510220200621Experimental investigation and estimation of thermal conductivity and contact conductance of granular activated carbon packed bed as a function of densityExperimental investigation and estimation of thermal conductivity and contact conductance of granular activated carbon packed bed as a function of density193204187410.22044/jsfm.2020.6207.2475FAM.SiavashiP.MohammadiMech. Eng., Iran University of Science and technology, Tehran, IranM. H.Khaliji OskueiMech. Eng., School of Engineering, Warwick University, Coventry, EnglandK.GhasemiSchool of Mechanical Engineering, Iran University of Science and TechnologyJournal Article20170911Activated carbon (AC) is a kind of carbon that because of having tiny and low-volume cavities provides a good contact surface for adsorption and chemical reactions. AC has various applications in industries like filtration, water purification, refrigeration, agriculture, medicine industries and so on. Recognizing thermal properties of AC is valuable to provide an appropriate design of its applications especially in adsorption refrigeration cycles. In such designs the most important parameters of AC bulk is its thermal conductivity and thermal contact conductance resistance with wall. In this study, a test setup is prepared to conduct experimental investigation and estimate required parameters for granular AC. Granular AC with four different densities was packed in a steel closed cylinder and thermal loading was applied on its outside wall. By measuring transient temperature at the center of the cylinder and using inverse thermal methods, thermal conductivity and contact conductance with steel wall were estimated. Results show increase in thermal conductivity and contact conductance between carbon and steel wall as density increases.Activated carbon (AC) is a kind of carbon that because of having tiny and low-volume cavities provides a good contact surface for adsorption and chemical reactions. AC has various applications in industries like filtration, water purification, refrigeration, agriculture, medicine industries and so on. Recognizing thermal properties of AC is valuable to provide an appropriate design of its applications especially in adsorption refrigeration cycles. In such designs the most important parameters of AC bulk is its thermal conductivity and thermal contact conductance resistance with wall. In this study, a test setup is prepared to conduct experimental investigation and estimate required parameters for granular AC. Granular AC with four different densities was packed in a steel closed cylinder and thermal loading was applied on its outside wall. By measuring transient temperature at the center of the cylinder and using inverse thermal methods, thermal conductivity and contact conductance with steel wall were estimated. Results show increase in thermal conductivity and contact conductance between carbon and steel wall as density increases.https://jsfm.shahroodut.ac.ir/article_1874_70a14a540a97bdc0750416053100c1ab.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-947510220200621Reduced pressure drop in the air inlet of a cruise missile using adjoint optimizationReduced pressure drop in the air inlet of a cruise missile using adjoint optimization205217187510.22044/jsfm.2020.8745.2980FAM. R.Tavalaee FardAerospace Department, Malek Ashtar University of Technology, Tehran, IranH.ParhizkarAerospace Department, Malek Ashtar University of Technology, Tehran, IranM.GarshasbiAerospace Department, Malek Ashtar University of Technology, Tehran, IranJournal Article20190727The air inlet is one of the main components of propulsion systems, whose main task is to supply the required airflow uniformly.This study aims to optimize an S-type inlet used in cruise missiles. The adjoint optimization tools available in fluent software are used for this purpose. In the first step, the method has been validated experimentally. <br /> The recovered pressure for the present study is 0.96 %, which has a good agreement with the results from the empirical method In the following, numerical modeling of the airflow is performed in the existing S-shaped duct. Then, using the numerical solution of the adjoint equations, the sensitivity of the cost function to the deformation of duct walls is calculated. According to geometric constraints, the purpose of optimization is to achieve a geometry that can minimize the total pressure drop by minimum geometry changes and provide the required mass flow rates. In the present work, by removing the flow separation region due to adjoint optimization, the total pressure drop has been reduced from 4.6 to 3 percent, and the mass flow rate has increased from 5.1 to 6.5 kg/s.The air inlet is one of the main components of propulsion systems, whose main task is to supply the required airflow uniformly.This study aims to optimize an S-type inlet used in cruise missiles. The adjoint optimization tools available in fluent software are used for this purpose. In the first step, the method has been validated experimentally. <br /> The recovered pressure for the present study is 0.96 %, which has a good agreement with the results from the empirical method In the following, numerical modeling of the airflow is performed in the existing S-shaped duct. Then, using the numerical solution of the adjoint equations, the sensitivity of the cost function to the deformation of duct walls is calculated. According to geometric constraints, the purpose of optimization is to achieve a geometry that can minimize the total pressure drop by minimum geometry changes and provide the required mass flow rates. In the present work, by removing the flow separation region due to adjoint optimization, the total pressure drop has been reduced from 4.6 to 3 percent, and the mass flow rate has increased from 5.1 to 6.5 kg/s.https://jsfm.shahroodut.ac.ir/article_1875_e8f61c3a9acd2d9fdf47eea4db2948a6.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-947510220200621The effect of changing the position of the hot wall and increasing the amplitude and number of oscillations of wavy wall on the flow and heat transfer of nanofluid inside the channel in the presence of magnetic fieldThe effect of changing the position of the hot wall and increasing the amplitude and number of oscillations of wavy wall on the flow and heat transfer of nanofluid inside the channel in the presence of magnetic field219236187610.22044/jsfm.2020.8917.3022FAM.NematiPHD student, Faculty of Engineering, University of yazdM.SefidDepartment of Mechanical Engineering, Yazd University, Yazd, IranA.R.RahmatiJournal Article20190917In this paper, the effect of changing position of heat source on nanofluid heat transfer under the influence of magnetic field in the wavy channel with variable amplitude and number of oscillations is investigated by Lattice Boltzmann Method. A uniform magnetic field is applied perpendicular to the channel. The first half of the upper channel wall, wavy form with the amplitude and number of variable oscillations at constant cold temperature, and the half of the bottom channel with variable position, are at constant hot temperature. Other walls are insulated for heat and mass. In this study, the effect of parameters such as Reynolds number, nanoparticle volume fraction, Hartmann number, hot wall position and amplitude and number of wavy wall oscillations were evaluated. The results show that at a specific position location of the hot wall, the average Nusselt number increases with the increase of other parameters. The highest heat transfer also occurs when the hot wall is closer to the channel inlet that results in an average 20% increase in the Nusselt number. The effect of increasing the Hartmann number on heat transfer is greater when the hot wall is closer to the channel outlet. Increasing the percentage of nanoparticles increases heat transfer and this effect increases with decreasing Reynolds number.In this paper, the effect of changing position of heat source on nanofluid heat transfer under the influence of magnetic field in the wavy channel with variable amplitude and number of oscillations is investigated by Lattice Boltzmann Method. A uniform magnetic field is applied perpendicular to the channel. The first half of the upper channel wall, wavy form with the amplitude and number of variable oscillations at constant cold temperature, and the half of the bottom channel with variable position, are at constant hot temperature. Other walls are insulated for heat and mass. In this study, the effect of parameters such as Reynolds number, nanoparticle volume fraction, Hartmann number, hot wall position and amplitude and number of wavy wall oscillations were evaluated. The results show that at a specific position location of the hot wall, the average Nusselt number increases with the increase of other parameters. The highest heat transfer also occurs when the hot wall is closer to the channel inlet that results in an average 20% increase in the Nusselt number. The effect of increasing the Hartmann number on heat transfer is greater when the hot wall is closer to the channel outlet. Increasing the percentage of nanoparticles increases heat transfer and this effect increases with decreasing Reynolds number.https://jsfm.shahroodut.ac.ir/article_1876_5793b683f199c59ca90c67b82502cd83.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-947510220200621Modeling and Prediction of Fuel Consumption and Emissions of Direct Injection Diesel Engines using Artificial Neural Network by Applying Control Parameters of Engine Speed, Fuel Mass and Inlet Air TemperatureModeling and Prediction of Fuel Consumption and Emissions of Direct Injection Diesel Engines using Artificial Neural Network by Applying Control Parameters of Engine Speed, Fuel Mass and Inlet Air Temperature237251187710.22044/jsfm.2020.4080.2084FAA.Zarenejad AshkezariImam Khomeini Maritime University of NowshahrM.R.HadaviShahid Rajaei Teacher Training University and University of Imam Khomeini Marine Sciences, Department of Mechanical Engineering, Tehran, IranJournal Article20160316In the present study, using artificial neural network, modeling and prediction of NOx, soot and fuel consumption in a direct injection diesel engine is done by applying control variables of engine speed, inlet air temperature and fuel mass injected into the combustion chamber. For this purpose, the empirical experiments were carried out to prepare the necessary modeling and correlation between input and output parameters by neural network. The neural network with the Levenberg-Marquardt training algorithm is designed to train the existing relationship between the above parameters, in which the output variables are modeled completely independently. In other words, for any output such as NOx, the number of hidden layer neurons as well as the lattice control parameters would be quite different from the same parameters for soot or fuel consumption. The results show that the designed neural network reaches accuracy 0.97 for 36 neurons in the hidden layer at 3733th epoch to test the data in NOx modeling. Also, modeling of soot with more neurons and accuracy 0.96 is performed in the 2081th epoch. On the other hand, the test accuracy for modeling fuel consumption for 19 neurons in the hidden layer at 3698th epoch was 0.94 which is due to the uneven distribution of the experimental data over a wide range of modeling ranges. The neural network can also be used as an effective method in direct injection diesel engines intelligent control systems to reduce pollutants and fuel consumption due to its fast convergence and hence short response time.In the present study, using artificial neural network, modeling and prediction of NOx, soot and fuel consumption in a direct injection diesel engine is done by applying control variables of engine speed, inlet air temperature and fuel mass injected into the combustion chamber. For this purpose, the empirical experiments were carried out to prepare the necessary modeling and correlation between input and output parameters by neural network. The neural network with the Levenberg-Marquardt training algorithm is designed to train the existing relationship between the above parameters, in which the output variables are modeled completely independently. In other words, for any output such as NOx, the number of hidden layer neurons as well as the lattice control parameters would be quite different from the same parameters for soot or fuel consumption. The results show that the designed neural network reaches accuracy 0.97 for 36 neurons in the hidden layer at 3733th epoch to test the data in NOx modeling. Also, modeling of soot with more neurons and accuracy 0.96 is performed in the 2081th epoch. On the other hand, the test accuracy for modeling fuel consumption for 19 neurons in the hidden layer at 3698th epoch was 0.94 which is due to the uneven distribution of the experimental data over a wide range of modeling ranges. The neural network can also be used as an effective method in direct injection diesel engines intelligent control systems to reduce pollutants and fuel consumption due to its fast convergence and hence short response time.https://jsfm.shahroodut.ac.ir/article_1877_c1d3d843a058b5c25c008eeff6e6a279.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-947510220200621Experimental study of subsurface damage and material removal mechanisms in abrasive waterjet milling process of aluminum oxide ceramicExperimental study of subsurface damage and material removal mechanisms in abrasive waterjet milling process of aluminum oxide ceramic253265187810.22044/jsfm.2020.8942.3026FAF.PashmforoushDepartment of mechanical engineering, faculty of engineering, university of maragheh, maragheh, iran.R.Beyraghi BaranlouDepartment of mechanical engineering, Faculty of engineering, University of Maragheh, Maragheh, Iran.R.MaroofiazarFaculty of Mechanical Engineering, University of MaraghehA.Hassanpour Babajanuniversity of maraghehJournal Article20190928Machining of hard and brittle materials such as aluminum oxide ceramic by conventional machining processes is very difficult due to the high hardness and wear resistance of this material, subsurface damages, poor surface quality and severe wear of the cutting tool. In this regard, abrasive water jet machining is widely used for machining of hard and brittle materials due to its excellent properties such as lack of thermal stresses, low machining forces, lack of mechanical contact between the specimen and cutting tool and compatibility with environment. Hence, in this research, abrasive water jet milling of aluminum oxide ceramic was experimentally investigated. In this respect, the influence of input parameters such as water jet pressure, feed rate, abrasive particles weight fraction and nozzle gap was evaluated on subsurface damages and material removal mechanisms (i.e. micro-cutting and micro-fracture). The obtained results indicate that the dominant material removal mechanism for aluminum oxide is micro-fracture, in which, material removal takes place by formation of micro-cracks and micro-craters beneath the abrasives indentation depth. Also, the results demonstrate that the probability of subsurface damages formation increases by increasing the jet pressure, decreasing feed rate, decreasing the nozzle gap and increasing the abrasives weight fraction. The statistical analysis of variance (ANOVA) revealed that the most significant parameters affecting subsurface damage depth are water jet pressure, weight fraction of abrasive particles, feed rate and nozzle gap, respectively. The contribution percentage of these parameters is 54.37%, 31.15%, 12.91% and 1.57%, respectively.Machining of hard and brittle materials such as aluminum oxide ceramic by conventional machining processes is very difficult due to the high hardness and wear resistance of this material, subsurface damages, poor surface quality and severe wear of the cutting tool. In this regard, abrasive water jet machining is widely used for machining of hard and brittle materials due to its excellent properties such as lack of thermal stresses, low machining forces, lack of mechanical contact between the specimen and cutting tool and compatibility with environment. Hence, in this research, abrasive water jet milling of aluminum oxide ceramic was experimentally investigated. In this respect, the influence of input parameters such as water jet pressure, feed rate, abrasive particles weight fraction and nozzle gap was evaluated on subsurface damages and material removal mechanisms (i.e. micro-cutting and micro-fracture). The obtained results indicate that the dominant material removal mechanism for aluminum oxide is micro-fracture, in which, material removal takes place by formation of micro-cracks and micro-craters beneath the abrasives indentation depth. Also, the results demonstrate that the probability of subsurface damages formation increases by increasing the jet pressure, decreasing feed rate, decreasing the nozzle gap and increasing the abrasives weight fraction. The statistical analysis of variance (ANOVA) revealed that the most significant parameters affecting subsurface damage depth are water jet pressure, weight fraction of abrasive particles, feed rate and nozzle gap, respectively. The contribution percentage of these parameters is 54.37%, 31.15%, 12.91% and 1.57%, respectively.https://jsfm.shahroodut.ac.ir/article_1878_5cc446ecb817066c1fd1bc584491d91c.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-947510220200621Investigation of the effect of cavity insertion in brick on heat transfer through using computational fluid dynamic simulationInvestigation of the effect of cavity insertion in brick on heat transfer through using computational fluid dynamic simulation267283187910.22044/jsfm.2020.8596.2964FAA.Shahverdy GhahfakhriDepartment of Mechanical Engineering, Vali-e-Asr University of Rafsanajn, Rafsanjan, IranA.R.Arab SolgharDepartment of Mechanical Engineering, Vali-e-Asr University of Rafsanajn, Rafsanjan, IranM.MohammadiDepartment of Mechanical Engineering, Vali-e-Asr University of Rafsanajn, Rafsanjan, IranJournal Article20191005In this study, heat loss through light weight concrete bricks as a function of the size and number of bricks’ cavities was examined via numerical simulation. To minimize the simplifications, conjugate convection and radiation heat transfer within the brick’s cavities filled with air was considered. Also, in the solid of the brick, conduction heat transfer was taken into account. To assess the orientation of the cavities in the brick, two geometrical constrains were employed in the design of the bricks leading to 22 different layouts for which there should be at least two cavities and at most nine enclosures inside a brick. Computational fluid dynamic approaches based on finite volume method were used for the simulations. 3D natural heat transfer with incompressible laminar flow was assumed in the cavities under steady state conditions. To analyze and compare the results in terms of thermal characteristics, the equivalent coefficient of conduction heat transfer was defined. Also, the results were presented with isotherms and velocity contours. Finally, the best configurations of air cavities in the view point of heat transfer were found. The results demonstrate that the configuration and size of the cavities have profound impact on the rate of heat transfer. Also, considering radiation heat transfer in the cavities is rather important.In this study, heat loss through light weight concrete bricks as a function of the size and number of bricks’ cavities was examined via numerical simulation. To minimize the simplifications, conjugate convection and radiation heat transfer within the brick’s cavities filled with air was considered. Also, in the solid of the brick, conduction heat transfer was taken into account. To assess the orientation of the cavities in the brick, two geometrical constrains were employed in the design of the bricks leading to 22 different layouts for which there should be at least two cavities and at most nine enclosures inside a brick. Computational fluid dynamic approaches based on finite volume method were used for the simulations. 3D natural heat transfer with incompressible laminar flow was assumed in the cavities under steady state conditions. To analyze and compare the results in terms of thermal characteristics, the equivalent coefficient of conduction heat transfer was defined. Also, the results were presented with isotherms and velocity contours. Finally, the best configurations of air cavities in the view point of heat transfer were found. The results demonstrate that the configuration and size of the cavities have profound impact on the rate of heat transfer. Also, considering radiation heat transfer in the cavities is rather important.https://jsfm.shahroodut.ac.ir/article_1879_bc43dbd65db57eaa4c5777bbd24413e4.pdf