This article deals with the investigation of the effects of porosity distributions on nonlinear free vibration and transient analysis of porous functionally graded skew(PFGS)plates.The effective material properties of...This article deals with the investigation of the effects of porosity distributions on nonlinear free vibration and transient analysis of porous functionally graded skew(PFGS)plates.The effective material properties of the PFGS plates are obtained from the modified power-law equations in which gradation varies through the thickness of the PFGS plate.A nonlinear finite element(FE)formulation for the overall PFGS plate is derived by adopting first-order shear deformation theory(FSDT)in conjunction with von Karman’s nonlinear strain displacement relations.The governing equations of the PFGS plate are derived using the principle of virtual work.The direct iterative method and Newmark’s integration technique are espoused to solve nonlinear mathematical relations.The influences of the porosity distributions and porosity parameter indices on the nonlinear frequency responses of the PFGS plate for different skew angles are studied in various parameters.The effects of volume fraction grading index and skew angle on the plate’s nonlinear dynamic responses for various porosity distributions are illustrated in detail.展开更多
In this paper, experimental and numerical study were both conducted to investigate the effect of pore size and porosity distribution on radiation absorption and thermal performance of porous solar energy absorber. Ult...In this paper, experimental and numerical study were both conducted to investigate the effect of pore size and porosity distribution on radiation absorption and thermal performance of porous solar energy absorber. Ultraviolet-visible-near infrared(UV-Vis-NIR) spectrophotometer was used to measure the transmittance of porous media to reflect its radiation absorption capabilities. Numerical model was established based on the assumption of thermal nonequilibrium condition as well as using P1 model to consider the radiation heat transfer. The UV-Vis-NIR spectrophotometer measurement showed that:(1) With smaller pore size, the spectral transmittance of the porous media would be lower and the solar radiation absorption would be better;(2)Among the materials with different pore size distributions, pore-size-decreased combo and pore-size-increased combo have almost equal absorption coefficient which are higher than that of uniform structure. Numerical simulation demonstrated that:(3)For materials with different pore size distributions, pore-size-decreased structure has the best radiation absorption due to its ability of maximizing the volumetric absorption effect, which is agreed with the UV-Vis-NIR spectrophotometer experimental results;(4) For materials with different porosity distributions, porosity-gradually-increased structure has the highest mean fluid/solid temperatures because it can utilize the enhanced convective/conductive heat transfer to improve the overall thermal performance of porous receiver;(5) Porous structure with pore-size-decreased distribution and porosity-gradually-increased distribution has the best thermal performance of which the mean temperatures of fluid/solid phases are the highest among all the studied cases.展开更多
This paper investigates the effect of porosity on active damping of geometrically nonlinear vibrations(GNLV)of the magneto-electro-elastic(MEE)functionally graded(FG)plates incorporated with active treatment constrict...This paper investigates the effect of porosity on active damping of geometrically nonlinear vibrations(GNLV)of the magneto-electro-elastic(MEE)functionally graded(FG)plates incorporated with active treatment constricted layer damping(ATCLD)patches.The perpendicularly/slanted reinforced 1-3 piezoelectric composite(1-3 PZC)constricting layer.The constricted viscoelastic layer of the ATCLD is modeled in the time-domain using Golla-Hughes-Mc Tavish(GHM)technique.Different types of porosity distribution in the porous magneto-electro-elastic functionally graded PMEE-FG plate graded in the thickness direction.Considering the coupling effects among elasticity,electrical,and magnetic fields,a three-dimensional finite element(FE)model for the smart PMEE-FG plate is obtained by incorporating the theory of layer-wise shear deformation.The geometric nonlinearity adopts the von K arm an principle.The study presents the effects of a variant of a power-law index,porosity index,the material gradation,three types of porosity distribution,boundary conditions,and the piezoelectric fiber’s orientation angle on the control of GNLV of the PMEE-FG plates.The results reveal that the FG substrate layers’porosity significantly impacts the nonlinear behavior and damping performance of the PMEE-FG plates.展开更多
The deformation of soil skeleton and migration of pore fluid are the major factors relevant to the triggeringof and damages by liquefaction. The influence of pore fluid migration during earthquake has beendemonstrated...The deformation of soil skeleton and migration of pore fluid are the major factors relevant to the triggeringof and damages by liquefaction. The influence of pore fluid migration during earthquake has beendemonstrated from recent model experiments and field case studies. Most of the current liquefactionassessment models are based on testing of isotropic liquefiable materials. However the recent NewZealand earthquake shows much severer damages than those predicted by existing models. A fundamentalcause has been contributed to the embedded layers of low permeability silts. The existence ofthese silt layers inhibits water migration under seismic loads, which accelerated liquefaction and causeda much larger settlement than that predicted by existing theories. This study intends to understand theprocess of moisture migration in the pore space of sand using discrete element method （DEM） simulation.Simulations were conducted on consolidated undrained triaxial testing of sand where a cylindersample of sand was built and subjected to a constant confining pressure and axial loading. The porositydistribution was monitored during the axial loading process. The spatial distribution of porosity changewas determined, which had a direct relationship with the distribution of excess pore water pressure. Thenon-uniform distribution of excess pore water pressure causes moisture migration. From this, themigration of pore water during the loading process can be estimated. The results of DEM simulationshow a few important observations： （1） External forces are mainly carried and transmitted by the particlechains of the soil sample; （2） Porosity distribution during loading is not uniform due to nonhomogeneoussoil fabric （i.e. the initial particle arrangement and existence of particle chains）; （3）Excess pore water pressure develops differently at different loading stages. At the early stage of loading,zones with a high initial porosity feature higher porosity changes under the influence of external loading,which leads to a larger pore pressure variation （increase or decrease） in such zones. As the axial strainincreases, particle rearrangement occurs and final porosity distribution has minor relationship with theinitial condition, and the pore pressure distribution becomes irregular. The differences in the porepressure development imply that water will migrate in the pore space in order to balance the pore waterpressure distribution. The results of this simulation offer an insight on the microscale water migration inthe soil pore space, which is important for holistic description of the triggering of soil liquefaction in lightof its microstructure. 2015 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.展开更多
This article presents the investigation of nonlinear vibration analysis of tapered porous functionally graded skew(TPFGS)plate considering the effects of geometrical non-uniformities to optimize the thickness in the s...This article presents the investigation of nonlinear vibration analysis of tapered porous functionally graded skew(TPFGS)plate considering the effects of geometrical non-uniformities to optimize the thickness in the structural design.The TPFGS plate is analyzed considering linearly,bi-linearly,and exponentially varying thicknesses.The plate’s effective material properties are tailor-made using a modified power-law distribution in which gradation varies along the thickness direction of the TPFGS plate.Incorporating the non-linear finite element formulation to develop the kinematic equation’s displacement model for the TPFGS plate is based on the first-order shear deformation theory(FSDT)in conjunction with von Karman’s nonlinearity.The nonlinear governing equations are established by Hamilton’s principle.The direct iterative method is adopted to solve the nonlinear mathematical relations to obtain the nonlinear frequencies.The influence of the porosity distributions and porosity parameter indices on the nonlinear frequency responses of the TPFGS plate for different skew angles and variable thicknesses are studied for various geometrical parameters.The influence of taper ratio,variable thickness,skewness,porosity distributions,gradation,and boundary conditions on the plate’s nonlinear vibration is demonstrated.The nonlinear frequency analysis reveals that the geometrical nonuniformities and porosities significantly influence the porous functionally graded plates with varying thickness than the uniform thickness.Besides,exponentially and linearly variable thicknesses can be considered for the thickness optimizations of TPFGS plates in the structural design.展开更多
In order to analyze the microstructure of salt anti-freezing asphalt concrete, i e, MFL（Mafilon） modified asphalt concrete, MIP（mercury intrusion porosity） method was used to obtain the data including porosity and...In order to analyze the microstructure of salt anti-freezing asphalt concrete, i e, MFL（Mafilon） modified asphalt concrete, MIP（mercury intrusion porosity） method was used to obtain the data including porosity and pore size distribution in micro scale. Results show that the porosity grows up with the increase of immersion duration and the salt content. During the immersion, the amount of large pores（60-200 μm） grow up gradually and porosity also grows up correspondingly. Even with different immersion duration, most pores＇ size distribute is beyond 7000 nm.展开更多
For accurate description of particle structure,single particle properties are required so that the properties of interest can be expressed as distributed parameters.X-Ray microtomography of the powder bed with subsequ...For accurate description of particle structure,single particle properties are required so that the properties of interest can be expressed as distributed parameters.X-Ray microtomography of the powder bed with subsequent particle separation can be used for this purpose.In this paper,a new algorithm for X-Ray microtomography images of spray dried particles was introduced since standard methods tend to fail if the particle size distribution is broad.The algorithm is based on 2D shape classification and subsequent 3D reconstitution of the particle using only a shape classifier as free parameter.The proposed algorithm was validated successfully.Using the algorithm,single particle porosities were obtained,which ranged from 0 to 70%.Prerequisites for the application of the algorithm are that a shape classifier can be set and that the 3D shape is regular.展开更多
Based on the principle of discrete element method （DEM）, a 2D slot model of a COREX melter gasifier was established to analyze the influence of cohesive zone shape on solid flow, including mass distribution, velocit...Based on the principle of discrete element method （DEM）, a 2D slot model of a COREX melter gasifier was established to analyze the influence of cohesive zone shape on solid flow, including mass distribution, velocity distribution, normal force distribution and porosity distribution at a microscopic level. The results show that the co- hesive zone shape almost does not affect the particle movement in the upper shaft and deadman shape. The particles in the lower central bottom experience large normal force to support the particles above them, while particles around the raceway and in the fast flow zone exhibit weak force network. The porosity distribution was also examined under three kinds of cohesive zones. Like the velocity distribution, the whole packed bed can be divided into four main re- gions. With the increase of cohesive zone position, the low porosity region located in the root of cohesive zone increa- ses. And the porosity distribution becomes asymmetric in the case of biased cohesive zone.展开更多
文摘This article deals with the investigation of the effects of porosity distributions on nonlinear free vibration and transient analysis of porous functionally graded skew(PFGS)plates.The effective material properties of the PFGS plates are obtained from the modified power-law equations in which gradation varies through the thickness of the PFGS plate.A nonlinear finite element(FE)formulation for the overall PFGS plate is derived by adopting first-order shear deformation theory(FSDT)in conjunction with von Karman’s nonlinear strain displacement relations.The governing equations of the PFGS plate are derived using the principle of virtual work.The direct iterative method and Newmark’s integration technique are espoused to solve nonlinear mathematical relations.The influences of the porosity distributions and porosity parameter indices on the nonlinear frequency responses of the PFGS plate for different skew angles are studied in various parameters.The effects of volume fraction grading index and skew angle on the plate’s nonlinear dynamic responses for various porosity distributions are illustrated in detail.
基金supported by the National Natural Science Foundation of China (Grant No. 51606142)the China Postdoctoral Science Foundation (Grant No. 2016M592787)+2 种基金the Natural Science Basic Research Plan in Shaanxi Province of China (Grant No. 2017JQ5001)the Fundamental Research Funds For the Central Universities (Grant No. xjj2016049)Creative Team Plan (Grant No. cxtd2017004) in Xi’an Jiaotong University
文摘In this paper, experimental and numerical study were both conducted to investigate the effect of pore size and porosity distribution on radiation absorption and thermal performance of porous solar energy absorber. Ultraviolet-visible-near infrared(UV-Vis-NIR) spectrophotometer was used to measure the transmittance of porous media to reflect its radiation absorption capabilities. Numerical model was established based on the assumption of thermal nonequilibrium condition as well as using P1 model to consider the radiation heat transfer. The UV-Vis-NIR spectrophotometer measurement showed that:(1) With smaller pore size, the spectral transmittance of the porous media would be lower and the solar radiation absorption would be better;(2)Among the materials with different pore size distributions, pore-size-decreased combo and pore-size-increased combo have almost equal absorption coefficient which are higher than that of uniform structure. Numerical simulation demonstrated that:(3)For materials with different pore size distributions, pore-size-decreased structure has the best radiation absorption due to its ability of maximizing the volumetric absorption effect, which is agreed with the UV-Vis-NIR spectrophotometer experimental results;(4) For materials with different porosity distributions, porosity-gradually-increased structure has the highest mean fluid/solid temperatures because it can utilize the enhanced convective/conductive heat transfer to improve the overall thermal performance of porous receiver;(5) Porous structure with pore-size-decreased distribution and porosity-gradually-increased distribution has the best thermal performance of which the mean temperatures of fluid/solid phases are the highest among all the studied cases.
文摘This paper investigates the effect of porosity on active damping of geometrically nonlinear vibrations(GNLV)of the magneto-electro-elastic(MEE)functionally graded(FG)plates incorporated with active treatment constricted layer damping(ATCLD)patches.The perpendicularly/slanted reinforced 1-3 piezoelectric composite(1-3 PZC)constricting layer.The constricted viscoelastic layer of the ATCLD is modeled in the time-domain using Golla-Hughes-Mc Tavish(GHM)technique.Different types of porosity distribution in the porous magneto-electro-elastic functionally graded PMEE-FG plate graded in the thickness direction.Considering the coupling effects among elasticity,electrical,and magnetic fields,a three-dimensional finite element(FE)model for the smart PMEE-FG plate is obtained by incorporating the theory of layer-wise shear deformation.The geometric nonlinearity adopts the von K arm an principle.The study presents the effects of a variant of a power-law index,porosity index,the material gradation,three types of porosity distribution,boundary conditions,and the piezoelectric fiber’s orientation angle on the control of GNLV of the PMEE-FG plates.The results reveal that the FG substrate layers’porosity significantly impacts the nonlinear behavior and damping performance of the PMEE-FG plates.
文摘The deformation of soil skeleton and migration of pore fluid are the major factors relevant to the triggeringof and damages by liquefaction. The influence of pore fluid migration during earthquake has beendemonstrated from recent model experiments and field case studies. Most of the current liquefactionassessment models are based on testing of isotropic liquefiable materials. However the recent NewZealand earthquake shows much severer damages than those predicted by existing models. A fundamentalcause has been contributed to the embedded layers of low permeability silts. The existence ofthese silt layers inhibits water migration under seismic loads, which accelerated liquefaction and causeda much larger settlement than that predicted by existing theories. This study intends to understand theprocess of moisture migration in the pore space of sand using discrete element method （DEM） simulation.Simulations were conducted on consolidated undrained triaxial testing of sand where a cylindersample of sand was built and subjected to a constant confining pressure and axial loading. The porositydistribution was monitored during the axial loading process. The spatial distribution of porosity changewas determined, which had a direct relationship with the distribution of excess pore water pressure. Thenon-uniform distribution of excess pore water pressure causes moisture migration. From this, themigration of pore water during the loading process can be estimated. The results of DEM simulationshow a few important observations： （1） External forces are mainly carried and transmitted by the particlechains of the soil sample; （2） Porosity distribution during loading is not uniform due to nonhomogeneoussoil fabric （i.e. the initial particle arrangement and existence of particle chains）; （3）Excess pore water pressure develops differently at different loading stages. At the early stage of loading,zones with a high initial porosity feature higher porosity changes under the influence of external loading,which leads to a larger pore pressure variation （increase or decrease） in such zones. As the axial strainincreases, particle rearrangement occurs and final porosity distribution has minor relationship with theinitial condition, and the pore pressure distribution becomes irregular. The differences in the porepressure development imply that water will migrate in the pore space in order to balance the pore waterpressure distribution. The results of this simulation offer an insight on the microscale water migration inthe soil pore space, which is important for holistic description of the triggering of soil liquefaction in lightof its microstructure. 2015 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.
文摘This article presents the investigation of nonlinear vibration analysis of tapered porous functionally graded skew(TPFGS)plate considering the effects of geometrical non-uniformities to optimize the thickness in the structural design.The TPFGS plate is analyzed considering linearly,bi-linearly,and exponentially varying thicknesses.The plate’s effective material properties are tailor-made using a modified power-law distribution in which gradation varies along the thickness direction of the TPFGS plate.Incorporating the non-linear finite element formulation to develop the kinematic equation’s displacement model for the TPFGS plate is based on the first-order shear deformation theory(FSDT)in conjunction with von Karman’s nonlinearity.The nonlinear governing equations are established by Hamilton’s principle.The direct iterative method is adopted to solve the nonlinear mathematical relations to obtain the nonlinear frequencies.The influence of the porosity distributions and porosity parameter indices on the nonlinear frequency responses of the TPFGS plate for different skew angles and variable thicknesses are studied for various geometrical parameters.The influence of taper ratio,variable thickness,skewness,porosity distributions,gradation,and boundary conditions on the plate’s nonlinear vibration is demonstrated.The nonlinear frequency analysis reveals that the geometrical nonuniformities and porosities significantly influence the porous functionally graded plates with varying thickness than the uniform thickness.Besides,exponentially and linearly variable thicknesses can be considered for the thickness optimizations of TPFGS plates in the structural design.
基金Funded by the National Natural Science Foundation of China(No.51578290)
文摘In order to analyze the microstructure of salt anti-freezing asphalt concrete, i e, MFL（Mafilon） modified asphalt concrete, MIP（mercury intrusion porosity） method was used to obtain the data including porosity and pore size distribution in micro scale. Results show that the porosity grows up with the increase of immersion duration and the salt content. During the immersion, the amount of large pores（60-200 μm） grow up gradually and porosity also grows up correspondingly. Even with different immersion duration, most pores＇ size distribute is beyond 7000 nm.
文摘For accurate description of particle structure,single particle properties are required so that the properties of interest can be expressed as distributed parameters.X-Ray microtomography of the powder bed with subsequent particle separation can be used for this purpose.In this paper,a new algorithm for X-Ray microtomography images of spray dried particles was introduced since standard methods tend to fail if the particle size distribution is broad.The algorithm is based on 2D shape classification and subsequent 3D reconstitution of the particle using only a shape classifier as free parameter.The proposed algorithm was validated successfully.Using the algorithm,single particle porosities were obtained,which ranged from 0 to 70%.Prerequisites for the application of the algorithm are that a shape classifier can be set and that the 3D shape is regular.
基金Item Sponsored by the Fundamental Research Funds for the Central Universities of China(N090402021)
文摘Based on the principle of discrete element method （DEM）, a 2D slot model of a COREX melter gasifier was established to analyze the influence of cohesive zone shape on solid flow, including mass distribution, velocity distribution, normal force distribution and porosity distribution at a microscopic level. The results show that the co- hesive zone shape almost does not affect the particle movement in the upper shaft and deadman shape. The particles in the lower central bottom experience large normal force to support the particles above them, while particles around the raceway and in the fast flow zone exhibit weak force network. The porosity distribution was also examined under three kinds of cohesive zones. Like the velocity distribution, the whole packed bed can be divided into four main re- gions. With the increase of cohesive zone position, the low porosity region located in the root of cohesive zone increa- ses. And the porosity distribution becomes asymmetric in the case of biased cohesive zone.
