Renewable energy storage technologies are critical for transitioning to sustainable energy systems,with salt caverns playing a significant role in large-scale solutions.In water-soluble mining of low-grade salt format...Renewable energy storage technologies are critical for transitioning to sustainable energy systems,with salt caverns playing a significant role in large-scale solutions.In water-soluble mining of low-grade salt formations,insoluble impurities and interlayers detach during salt dissolution and accumulate as sediment at the cavern base,thereby reducing the storage capacity and economic viability of salt cavern gas storage(SCGS).This study investigates sediment formation mechanisms,void distribution,and voidage in the Huai'an low-grade salt mine,introducing a novel self-developed physical simulation device for two butted-well horizontal(TWH)caverns that replicates compressed air injection and brine discharge.Experiments comparing“one injection and one discharge”and“two injections and one discharge”modes revealed that(1)compressed air effectively displaces brine from sediment voids,(2)a 0.5 MPa injection pressure corresponds to a 10.3 MPa operational lower limit in practice,aligning with field data,and(3)sediment voidage is approximately 46%,validated via air-brine interface theory.The“two injections and one discharge”mode outperformed in both discharge volume and rate.Additionally,a mathematical model for brine displacement via compressed air was established.These results provide foundational insights for optimizing compressed air energy storage(CAES)in low-grade salt mines,advancing their role in renewable energy integration.展开更多
Large-grain REBa_(2)Cu_(3)O_(7-δ)(REBCO,RE=rare earth)bulk superconductors offer promising magnetic field trapping capabilities due to their high critical current density,making them ideal for many important applicat...Large-grain REBa_(2)Cu_(3)O_(7-δ)(REBCO,RE=rare earth)bulk superconductors offer promising magnetic field trapping capabilities due to their high critical current density,making them ideal for many important applications such as trapped field magnets.However,for such large-grain superconductor bulks,there are lots of voids and cracks forming during the process of melting preparation,and some of them can be up to hundreds of microns or even millimeters in size.Consequently,these larger size voids/cracks pose a great threat to the strength of the bulks due to the inherent brittleness of superconductor REBCO materials.In order to ensure the operational safety of related superconducting devices with bulk superconductors,it is firstly important to accurately detect these voids/cracks in them.In this paper,we proposed a method for quantitatively evaluating multiple voids/cracks in bulk superconductors through the magnetic field and displacement response signals at superconductor bulk surface.The proposed method utilizes a damage index constructed from the magnetic field signals and displacement responses to identify the number and preliminary location of multiple defects.By dividing the detection area into subdomains and combining the magnetic field signals with displacement responses within each subdomain,a particle swarm algorithm was employed to evaluate the location and size parameters of the defects.In contrast to other evaluation methods using only magnetic field or displacement response signals,the combined evaluation method using both signals can identify the number of cracks effectively.Numerical studies demonstrate that the morphology of voids and cracks reconstructed using the proposed algorithm ideally matches real defects and is applicable to cases where voids and cracks coexist.This study provides a theoretical basis for the quantitative detection of voids/cracks in bulk superconductors.展开更多
Nano-twinned copper(nt-Cu),with a preferred orientation,is highly promising as interconnect materials in high-density advanced packaging due to its considerable mechanical strength,excellent electrical conductivity,an...Nano-twinned copper(nt-Cu),with a preferred orientation,is highly promising as interconnect materials in high-density advanced packaging due to its considerable mechanical strength,excellent electrical conductivity,and resistance to thermal migration.However,its application is impeded by sulfur-containing byproducts from the electroplating process,exacerbating the formation of Kirkendall voids within solder joints during thermal aging.Herein,through the incorporation of Zinc(Zn)into the nt-Cu layer,we develop a nt-Cu/Zn composite structure.Our findings provide the first definitive confirmation of the mechanism by which sulfur atoms migrate to the Cu_(3)Sn/nt-Cu interface through interstitial diffusion,thereby reducing the activation energy for vacancy formation.We further demonstrate that Zn effectively an-choring sulfur atoms,forming ZnS within the nt-Cu layer during heat treatment,which increases the vacancy formation energy and inhibits the development of Kirkendall voids.Remarkably,no Kirkendall voids are observed in the modified interconnects even after prolonged aging at 150℃ for 1000 h.The nt-Cu/Zn composite metallization layers significantly decrease the growth rate of interfacial intermetallic compounds by 33.6% and enhance the shear strength of solder interconnections to 228.9%.This research underscores the potential of nt-Cu in advanced electronic packaging,offering new pathways for improving the power density and reliability of electronic devices.展开更多
Nickel-based alloys are the primary structural materials in steam generators of high-temperature gas reactors.To understand the irradiation effect of nickel-based alloys,it is necessary to examine dislocation movement...Nickel-based alloys are the primary structural materials in steam generators of high-temperature gas reactors.To understand the irradiation effect of nickel-based alloys,it is necessary to examine dislocation movement and its interaction with irradiation defects at the microscale.Hardening due to voids and Ni_(3)Al precipitates may significantly impact irradiation damage in nickel-based alloys.This paper employs the molecular dynamics method to analyze the interaction between edge dislocations and irradiation defects(void and Ni_(3)Al precipitates)in face-centered cubic nickel.The effects of temperature and defect size on the interaction are also explored.The results show that the interaction process of the edge dislocation and irradiation defects can be divided into four stages:dislocation free slip,dislocation attracted,dislocation pinned,and dislocation unpinned.Interaction modes include the formation of stair-rod dislocations and the climbing of extended dislocation bundles for voids,as well as the generation of stair-rod dislocation and dislocation shear for precipitates.Besides,the interactions of edge dislocations with voids and Ni_(3)Al precipitates are strongly influenced by temperature and defect size.展开更多
Ccanposites are common material constructions for high-tech use now. Mechanical properties of woven reinforced composites are influenced by voids inside the structure. Voids could be classified to the two sections. Lo...Ccanposites are common material constructions for high-tech use now. Mechanical properties of woven reinforced composites are influenced by voids inside the structure. Voids could be classified to the two sections. Long and thin cracks are more dangerous than pores. It is important to find relations between preparation and place of occurrence of voids. This paper classifies defects according to rise mechanism, point of occurrence, orientation, size and affect to the properties. Image analysis was used for observing samples. Future work would be oriented not only to observing real samples, bet also to calculate mechanical properties frwn real and ideal structures in 3D woven reinforced composites.展开更多
According to the basic idea of dual-complementarity, in a simple and unified way proposed by the author, various energy principles in theory of elastic materials with voids can be established systematically, In this p...According to the basic idea of dual-complementarity, in a simple and unified way proposed by the author, various energy principles in theory of elastic materials with voids can be established systematically, In this paper, an important integral relation is given, which can be considered essentially as the generalized pr- inciple of virtual work. Based on this relation, it is possible not only to obtain the principle of virtual work and the reciprocal theorem of work in theory of elastic materials with voids, but also to derive systematically the complementary functionals for the eight-field, six-field, four-field and two-field generalized variational principles, and the principle of minimum potential and complementary energies. Furthermore, with this appro ach, the intrinsic relationship among various principles can be explained clearly.展开更多
This paper aims at investigating the effect of voids on the tensile properties of [（±45）4/（0,90）/（±45）2] S and [（±45）/0 4/（±45）（0,90）] S composites.Specimens with void contents in the r...This paper aims at investigating the effect of voids on the tensile properties of [（±45）4/（0,90）/（±45）2] S and [（±45）/0 4/（±45）（0,90）] S composites.Specimens with void contents in the range of 0.4% to 9.0% were fabricated from carbon/epoxy fabric.The void content was determined by ultrasonic attenuation and optical image analysis,and microscopic inspection was also used to analyze the shape and size of the voids.The influence of voids on the tensile strength and modulus of both stacking sequence is compared in terms of the size and the shape of the voids.The effect of voids on the initiation and propagation of tensile failure of both stacking sequence composite was investigated.展开更多
Often in abandoned mine sites are present both underground voids produced by mining and the tailings of treatment plant.An interesting solution for the rehabilitation of the sites would be to place the tailings of the...Often in abandoned mine sites are present both underground voids produced by mining and the tailings of treatment plant.An interesting solution for the rehabilitation of the sites would be to place the tailings of the process in the underground mining voids,thus obtaining the reclamation of surface areas and the stabilization of abandoned voids to prevent the dangerous phenomena of subsidence.However,these operations require inert waste,which must not be source of pollution,and the choice of a water/solid optimum to ensure good conditions of pumpability.展开更多
The effects of rotation and gravity on an electro-magneto-thermoelastic medium with diffusion and voids in a generalized thermoplastic half-space are studied by using the Lord-Shulman (L-S) model and the dual-phase-la...The effects of rotation and gravity on an electro-magneto-thermoelastic medium with diffusion and voids in a generalized thermoplastic half-space are studied by using the Lord-Shulman (L-S) model and the dual-phase-lag (DPL) model. The analytical solutions for the displacements, stresses, temperature, diffusion concentration, and volume fraction field with different values of the magnetic field, the rotation, the gravity, and the initial stress are obtained and portrayed graphically. The results indicate that the effects of gravity, rotation, voids, diffusion, initial stress, and electromagnetic field are very pronounced on the physical properties of the material.展开更多
A general and new explicit isogeometric topology optimisation approach with moving morphable voids(MMV)is proposed.In this approach,a novel multiresolution scheme with two distinct discretisation levels is developed t...A general and new explicit isogeometric topology optimisation approach with moving morphable voids(MMV)is proposed.In this approach,a novel multiresolution scheme with two distinct discretisation levels is developed to obtain high-resolution designs with a relatively low computational cost.Ersatz material model based on Greville abscissae collocation scheme is utilised to represent both the Young’s modulus of the material and the density field.Two benchmark examples are tested to illustrate the effectiveness of the proposed method.Numerical results show that high-resolution designs can be obtained with relatively low computational cost,and the optimisation can be significantly improved without introducing additional DOFs.展开更多
Four cellulose ethers（CEs） were compared for their effects on the pore structure of cement paste using mercury intrusion porosimetry. The experimental results show that the total pore volume and porosity of cement p...Four cellulose ethers（CEs） were compared for their effects on the pore structure of cement paste using mercury intrusion porosimetry. The experimental results show that the total pore volume and porosity of cement pastes containing the four cellulose ethers are significantly higher than that of the pure cement pastes and the total pore volume and porosity of cement pastes containing HEC（hydroxyethyl cellulose ether） or low viscosity cellulose ethers are low in four CEs. By changing the surface tension and viscosity of liquid phase and the strengthening of liquid film between air voids in cement pastes, CEs affect the formation, diameter evolution and upward movement of air voids and the pore structure of hardening cement paste. For the four CEs, the pore volume of cement pastes containing HEC or low viscosity cellulose ethers is higher with the diameter of 30-70 nm while lower with the diameter larger than 70 nm. CEs affect the pore structure of cement paste mainly through their effects on the evolvement of the small air voids into bigger ones when the pore diameter is below 70 nm and their effects on the entrainment and stabilization of air voids when the pore diameter is above 70 nm.展开更多
The formation and growth of Kirkendall voids in a binary alloy system during deformation process were investigated byphase field crystal model.The simulation results show that Kirkendall voids nucleate preferentially ...The formation and growth of Kirkendall voids in a binary alloy system during deformation process were investigated byphase field crystal model.The simulation results show that Kirkendall voids nucleate preferentially at the interface,and the averagesize of the voids increases with both the time and strain rate.There is an obvious coalescence of the voids at a large strain rate whenthe deformation is applied along the interface under both constant and cyclic strain rate conditions.For the cyclic strain rate appliedalong the interface,the growth exponent of Kirkendall voids increases with increasing the strain rate when the strain rate is largerthan1.0×10-6,while it increases initially and then decreases when the strain rate is smaller than9.0×10?7.The growth exponent ofKirkendall voids increases initially and then decreases gradually with increasing the length of cyclic period under a square-waveform constant strain rate.展开更多
The deterioration of the sleeper support on the ballasted track begins with the accumulation of sleeper voids.The increased dynamic loading in the voided zone and the ballast contact conditions cause the accelerated g...The deterioration of the sleeper support on the ballasted track begins with the accumulation of sleeper voids.The increased dynamic loading in the voided zone and the ballast contact conditions cause the accelerated growth of the settlements in the voided zones,which results in the appearance of local instabilities like ballast breakdown,white spots,subgrade defects,etc.The recent detection and quantification of the sleeper voids with track-side and onboard monitoring can help to avoid or delay the development of local instabilities.The present paper is devoted to the study of the dynamic behavior of railway track with sleeper voids in the ballast breakdown zone.The result of the experimental track-side measurements of rail acceleration and deflection is presented.The analysis shows the existence of the dynamic impact during wheel entry in the voided zone.However,the measured dynamic impact is subjected to the bias of the track-side measurement method.Both the mechanism of the impact and the measurement aspects are explained by using the one-beam model on viscoelastic foundation.The void features in the dynamic behavior are analyzed for the purpose of track-side and onboard monitoring.A practical method of the void parameter quantification is proposed.展开更多
The distribution characteristics of air voids in ultrathin asphalt friction course(UAFC) samples with different gradations and compaction methods were statistically analyzed using X-ray computed tomography(CT) and ima...The distribution characteristics of air voids in ultrathin asphalt friction course(UAFC) samples with different gradations and compaction methods were statistically analyzed using X-ray computed tomography(CT) and image analysis techniques. Based on the results, compared with the AC-5 sample, the OGFC-5mixture has a higher air void ratio, a larger air void size and a greater number of air voids, with the distribution of internal air voids being more uniform and their shapes being more rounded. The two-parameter Weibull function was applied to fit the gradation of air voids. The fitting results is good, and the function parameters are sensitive to changes in both mineral gradation and compaction method. Moreover, two homogeneity indices were proposed to evaluate the compaction uniformity of UAFC samples. Compared with the Marshall method,the SGC method is more conducive to improve the compaction uniformity of UAFC samples. The compaction method significantly influences the air void distribution characteristics and compaction uniformity of AC-5sample, but has a less significant impact on OGFC-5 sample. The experimental results in the study provides a solid foundation for further explorations on the internal structure and mixture design of UAFC.展开更多
According to the basic idea of dual-complementarity,in a simple and unified way proposed by the author,some basic principles in dynamic theory of elastic materials with voids can be established sys- tematically.In thi...According to the basic idea of dual-complementarity,in a simple and unified way proposed by the author,some basic principles in dynamic theory of elastic materials with voids can be established sys- tematically.In this paper, an important integral relation in terms of convolutions is given,which can be con- sidered as the generalized principle of virtual work in mechanics.Based on this relation,it is possible not on- ly to obtain the principle of virtual work and the reciprocal theorem in dynamic theory of elastic materials with voids,but also to derive systematically the complementary functionals for the eight-field,six-field, four-field and two-field simplified Gurtin-type variational principles.Furthermore,with this approach,the in- trinsic relationship among various principles can be explained clearly.展开更多
From the Boltzmann's constitutive law of viscoelastic materials and the linear theory of elastic materials with voids, a constitutive model of generalized force fields for viscoelastic solids with voids was given....From the Boltzmann's constitutive law of viscoelastic materials and the linear theory of elastic materials with voids, a constitutive model of generalized force fields for viscoelastic solids with voids was given. By using the variational integral method, the convolution-type functional was given and the corresponding generalized variational principles and potential energy principle of viscoelastic solids with voids were presented. It can be shown that the variational principles correspond to the differential equations and the initial and boundary conditions of viscoelastic body with voids. As an application, a generalized variational principle of viscoelastic Timoshenko beams with damage was obtained which corresponds to the differential equations of generalized motion and the initial and boundary conditions of beams. The variational principles provide a way for solving problems of viscoelastic solids with voids.展开更多
The development of pores in a clastic reservoir is one of the most important research subjects in oil-gas exploration and development, whereas the many reasons for the formation of secondary porosity have increased th...The development of pores in a clastic reservoir is one of the most important research subjects in oil-gas exploration and development, whereas the many reasons for the formation of secondary porosity have increased the degree of difficulty in such research. Thus the research aims are to discover the controlling factors of solutional voids in feldspars and to predict favorable regions for these voids. Macroscopic and systematic researches into the relationship between the kaolinite content in the feldspar solutional void developed area of the Chang 2 reservoir group of the Triassic Yanchang Formation in the Midwest Ordos Basin and the solutional void in feldspar have been made, and from this it can be determined that the kaolinite content has an indicative function to the distribution of the solutional void in feldspar. Solutional void in feldspar is relatively well developed at the area where kaolinite content is high. Although the factors affecting kaolinite content are complicated, yet that of the research area is mainly affected by the impact of the leaching atmospheric water acting on the palaeogeomorphology. Three favorable zone belts for the development of solutional voids in feldspars are forecasted on the basis of restoration of palaeogeomorphology.展开更多
A mechanism of plastic how localization in ductile matter near microvoids is studied. The voids with the size-scale of micromillimeter exist in sheet specimens under tensile loading, and the plastic strain held around...A mechanism of plastic how localization in ductile matter near microvoids is studied. The voids with the size-scale of micromillimeter exist in sheet specimens under tensile loading, and the plastic strain held around voids is obtained by digital image processing of deformed grids. The size growth of the microvoids, the spacing change of the neighboring voids, and the development of shear bands in the ligament between the voids, are presented by experimental results accompanied with the plastic strain distribution, that gives good interpretation to the process of void growth and coalescence with the how localization in the ligaments.展开更多
Introducing voids into AlN layer at a certain height using a simple method is meaningful but challenging.In this work,the AlN/sapphire template with AlN interlayer structure was designed and grown by metal-organic che...Introducing voids into AlN layer at a certain height using a simple method is meaningful but challenging.In this work,the AlN/sapphire template with AlN interlayer structure was designed and grown by metal-organic chemical vapor deposition.Then,the AlN template was annealed at 1700℃for an hour to introduce the voids.It was found that voids were formed in the AlN layer after high-temperature annealing and they were mainly distributed around the AlN interlayer.Meanwhile,the dislocation density of the AlN template decreased from 5.26×10^(9)cm^(-2)to 5.10×10^(8)cm^(-2).This work provides a possible method to introduce voids into AlN layer at a designated height,which will benefit the design of AlN-based devices.展开更多
This work aims at designing a set of curing pressure routes to produce laminates with various void contents. The effects of various consolidation pressures resulting in different void contents on mechanical strength o...This work aims at designing a set of curing pressure routes to produce laminates with various void contents. The effects of various consolidation pressures resulting in different void contents on mechanical strength of carbon/epoxy laminates have been examined. Characterization of the voids, in terms of void volume fraction, void distribution, size, and shape, was performed by standard test, ultrasonic inspection and metallographic analysis. The interlaminar shear strength was measured by the short-beam method. An empirical model was used to predict the strength vs porosity. The predicted strengths conform well with the experimental data and voids were found to be uniformly distributed throughout the laminate.展开更多
基金financial support from the National Key Research and Development Program of China(No.2024YFB4007100)the Basic ForwardLooking Project of the Sinopec Science and Technology Department,“Research on the Long-Term Sealing Mechanism of Multi-layer Salt Cavern Hydrogen Storage”(No.P24197-4)。
文摘Renewable energy storage technologies are critical for transitioning to sustainable energy systems,with salt caverns playing a significant role in large-scale solutions.In water-soluble mining of low-grade salt formations,insoluble impurities and interlayers detach during salt dissolution and accumulate as sediment at the cavern base,thereby reducing the storage capacity and economic viability of salt cavern gas storage(SCGS).This study investigates sediment formation mechanisms,void distribution,and voidage in the Huai'an low-grade salt mine,introducing a novel self-developed physical simulation device for two butted-well horizontal(TWH)caverns that replicates compressed air injection and brine discharge.Experiments comparing“one injection and one discharge”and“two injections and one discharge”modes revealed that(1)compressed air effectively displaces brine from sediment voids,(2)a 0.5 MPa injection pressure corresponds to a 10.3 MPa operational lower limit in practice,aligning with field data,and(3)sediment voidage is approximately 46%,validated via air-brine interface theory.The“two injections and one discharge”mode outperformed in both discharge volume and rate.Additionally,a mathematical model for brine displacement via compressed air was established.These results provide foundational insights for optimizing compressed air energy storage(CAES)in low-grade salt mines,advancing their role in renewable energy integration.
基金supported by the National Natural Science Foundation of China(Grant Nos.12232005 and 12072101).
文摘Large-grain REBa_(2)Cu_(3)O_(7-δ)(REBCO,RE=rare earth)bulk superconductors offer promising magnetic field trapping capabilities due to their high critical current density,making them ideal for many important applications such as trapped field magnets.However,for such large-grain superconductor bulks,there are lots of voids and cracks forming during the process of melting preparation,and some of them can be up to hundreds of microns or even millimeters in size.Consequently,these larger size voids/cracks pose a great threat to the strength of the bulks due to the inherent brittleness of superconductor REBCO materials.In order to ensure the operational safety of related superconducting devices with bulk superconductors,it is firstly important to accurately detect these voids/cracks in them.In this paper,we proposed a method for quantitatively evaluating multiple voids/cracks in bulk superconductors through the magnetic field and displacement response signals at superconductor bulk surface.The proposed method utilizes a damage index constructed from the magnetic field signals and displacement responses to identify the number and preliminary location of multiple defects.By dividing the detection area into subdomains and combining the magnetic field signals with displacement responses within each subdomain,a particle swarm algorithm was employed to evaluate the location and size parameters of the defects.In contrast to other evaluation methods using only magnetic field or displacement response signals,the combined evaluation method using both signals can identify the number of cracks effectively.Numerical studies demonstrate that the morphology of voids and cracks reconstructed using the proposed algorithm ideally matches real defects and is applicable to cases where voids and cracks coexist.This study provides a theoretical basis for the quantitative detection of voids/cracks in bulk superconductors.
基金financially supported by National Natural Science Foundation of China(No.U2241223)Pre-Research Foundation of China(No.909010203-202).
文摘Nano-twinned copper(nt-Cu),with a preferred orientation,is highly promising as interconnect materials in high-density advanced packaging due to its considerable mechanical strength,excellent electrical conductivity,and resistance to thermal migration.However,its application is impeded by sulfur-containing byproducts from the electroplating process,exacerbating the formation of Kirkendall voids within solder joints during thermal aging.Herein,through the incorporation of Zinc(Zn)into the nt-Cu layer,we develop a nt-Cu/Zn composite structure.Our findings provide the first definitive confirmation of the mechanism by which sulfur atoms migrate to the Cu_(3)Sn/nt-Cu interface through interstitial diffusion,thereby reducing the activation energy for vacancy formation.We further demonstrate that Zn effectively an-choring sulfur atoms,forming ZnS within the nt-Cu layer during heat treatment,which increases the vacancy formation energy and inhibits the development of Kirkendall voids.Remarkably,no Kirkendall voids are observed in the modified interconnects even after prolonged aging at 150℃ for 1000 h.The nt-Cu/Zn composite metallization layers significantly decrease the growth rate of interfacial intermetallic compounds by 33.6% and enhance the shear strength of solder interconnections to 228.9%.This research underscores the potential of nt-Cu in advanced electronic packaging,offering new pathways for improving the power density and reliability of electronic devices.
基金supported by the Ministry of Industry and Information Technology of China(grant number TC220A04W-7,203)CNNC Youth Elite Scientific Research Project,the National Key R&D Plan of China(grant number 2020YFB1901600)the National Science Technology Major Project of China(grant numbers 2017ZX06902012 and 2017ZX06901024).
文摘Nickel-based alloys are the primary structural materials in steam generators of high-temperature gas reactors.To understand the irradiation effect of nickel-based alloys,it is necessary to examine dislocation movement and its interaction with irradiation defects at the microscale.Hardening due to voids and Ni_(3)Al precipitates may significantly impact irradiation damage in nickel-based alloys.This paper employs the molecular dynamics method to analyze the interaction between edge dislocations and irradiation defects(void and Ni_(3)Al precipitates)in face-centered cubic nickel.The effects of temperature and defect size on the interaction are also explored.The results show that the interaction process of the edge dislocation and irradiation defects can be divided into four stages:dislocation free slip,dislocation attracted,dislocation pinned,and dislocation unpinned.Interaction modes include the formation of stair-rod dislocations and the climbing of extended dislocation bundles for voids,as well as the generation of stair-rod dislocation and dislocation shear for precipitates.Besides,the interactions of edge dislocations with voids and Ni_(3)Al precipitates are strongly influenced by temperature and defect size.
基金Supported by the Czech Scientific Foundation (No.106/03/ H150)
文摘Ccanposites are common material constructions for high-tech use now. Mechanical properties of woven reinforced composites are influenced by voids inside the structure. Voids could be classified to the two sections. Long and thin cracks are more dangerous than pores. It is important to find relations between preparation and place of occurrence of voids. This paper classifies defects according to rise mechanism, point of occurrence, orientation, size and affect to the properties. Image analysis was used for observing samples. Future work would be oriented not only to observing real samples, bet also to calculate mechanical properties frwn real and ideal structures in 3D woven reinforced composites.
基金The project supported by the National Natural Science Foundation of China
文摘According to the basic idea of dual-complementarity, in a simple and unified way proposed by the author, various energy principles in theory of elastic materials with voids can be established systematically, In this paper, an important integral relation is given, which can be considered essentially as the generalized pr- inciple of virtual work. Based on this relation, it is possible not only to obtain the principle of virtual work and the reciprocal theorem of work in theory of elastic materials with voids, but also to derive systematically the complementary functionals for the eight-field, six-field, four-field and two-field generalized variational principles, and the principle of minimum potential and complementary energies. Furthermore, with this appro ach, the intrinsic relationship among various principles can be explained clearly.
文摘This paper aims at investigating the effect of voids on the tensile properties of [（±45）4/（0,90）/（±45）2] S and [（±45）/0 4/（±45）（0,90）] S composites.Specimens with void contents in the range of 0.4% to 9.0% were fabricated from carbon/epoxy fabric.The void content was determined by ultrasonic attenuation and optical image analysis,and microscopic inspection was also used to analyze the shape and size of the voids.The influence of voids on the tensile strength and modulus of both stacking sequence is compared in terms of the size and the shape of the voids.The effect of voids on the initiation and propagation of tensile failure of both stacking sequence composite was investigated.
文摘Often in abandoned mine sites are present both underground voids produced by mining and the tailings of treatment plant.An interesting solution for the rehabilitation of the sites would be to place the tailings of the process in the underground mining voids,thus obtaining the reclamation of surface areas and the stabilization of abandoned voids to prevent the dangerous phenomena of subsidence.However,these operations require inert waste,which must not be source of pollution,and the choice of a water/solid optimum to ensure good conditions of pumpability.
文摘The effects of rotation and gravity on an electro-magneto-thermoelastic medium with diffusion and voids in a generalized thermoplastic half-space are studied by using the Lord-Shulman (L-S) model and the dual-phase-lag (DPL) model. The analytical solutions for the displacements, stresses, temperature, diffusion concentration, and volume fraction field with different values of the magnetic field, the rotation, the gravity, and the initial stress are obtained and portrayed graphically. The results indicate that the effects of gravity, rotation, voids, diffusion, initial stress, and electromagnetic field are very pronounced on the physical properties of the material.
基金National Natural Science Foundation of China under Grant Nos.51675525 and 11725211.
文摘A general and new explicit isogeometric topology optimisation approach with moving morphable voids(MMV)is proposed.In this approach,a novel multiresolution scheme with two distinct discretisation levels is developed to obtain high-resolution designs with a relatively low computational cost.Ersatz material model based on Greville abscissae collocation scheme is utilised to represent both the Young’s modulus of the material and the density field.Two benchmark examples are tested to illustrate the effectiveness of the proposed method.Numerical results show that high-resolution designs can be obtained with relatively low computational cost,and the optimisation can be significantly improved without introducing additional DOFs.
基金the National Natural Science Foundation of China(Nos.51461135001 and 51741804)the Natural Science Foundation of Hunan Province,China(No.2017JJ2066)the Scientific Research Project of Education Department,Hunan Province,China(No.17A054)
文摘Four cellulose ethers（CEs） were compared for their effects on the pore structure of cement paste using mercury intrusion porosimetry. The experimental results show that the total pore volume and porosity of cement pastes containing the four cellulose ethers are significantly higher than that of the pure cement pastes and the total pore volume and porosity of cement pastes containing HEC（hydroxyethyl cellulose ether） or low viscosity cellulose ethers are low in four CEs. By changing the surface tension and viscosity of liquid phase and the strengthening of liquid film between air voids in cement pastes, CEs affect the formation, diameter evolution and upward movement of air voids and the pore structure of hardening cement paste. For the four CEs, the pore volume of cement pastes containing HEC or low viscosity cellulose ethers is higher with the diameter of 30-70 nm while lower with the diameter larger than 70 nm. CEs affect the pore structure of cement paste mainly through their effects on the evolvement of the small air voids into bigger ones when the pore diameter is below 70 nm and their effects on the entrainment and stabilization of air voids when the pore diameter is above 70 nm.
基金Projects(51275178,51405162,51205135) supported by the National Natural Science Foundation of ChinaProjects(20110172110003,20130172120055) supported by the Doctoral Program of Higher Education of China
文摘The formation and growth of Kirkendall voids in a binary alloy system during deformation process were investigated byphase field crystal model.The simulation results show that Kirkendall voids nucleate preferentially at the interface,and the averagesize of the voids increases with both the time and strain rate.There is an obvious coalescence of the voids at a large strain rate whenthe deformation is applied along the interface under both constant and cyclic strain rate conditions.For the cyclic strain rate appliedalong the interface,the growth exponent of Kirkendall voids increases with increasing the strain rate when the strain rate is largerthan1.0×10-6,while it increases initially and then decreases when the strain rate is smaller than9.0×10?7.The growth exponent ofKirkendall voids increases initially and then decreases gradually with increasing the length of cyclic period under a square-waveform constant strain rate.
基金The authors acknowledge the support of Swiss Federal Railways with the experimental measurements.
文摘The deterioration of the sleeper support on the ballasted track begins with the accumulation of sleeper voids.The increased dynamic loading in the voided zone and the ballast contact conditions cause the accelerated growth of the settlements in the voided zones,which results in the appearance of local instabilities like ballast breakdown,white spots,subgrade defects,etc.The recent detection and quantification of the sleeper voids with track-side and onboard monitoring can help to avoid or delay the development of local instabilities.The present paper is devoted to the study of the dynamic behavior of railway track with sleeper voids in the ballast breakdown zone.The result of the experimental track-side measurements of rail acceleration and deflection is presented.The analysis shows the existence of the dynamic impact during wheel entry in the voided zone.However,the measured dynamic impact is subjected to the bias of the track-side measurement method.Both the mechanism of the impact and the measurement aspects are explained by using the one-beam model on viscoelastic foundation.The void features in the dynamic behavior are analyzed for the purpose of track-side and onboard monitoring.A practical method of the void parameter quantification is proposed.
基金Funded by Technology Innovation Demonstration Project of the Transportation Department of Yunnan Province (Science and Technology Education Section of Transport Department of Yunnan Province [2019](No.14)。
文摘The distribution characteristics of air voids in ultrathin asphalt friction course(UAFC) samples with different gradations and compaction methods were statistically analyzed using X-ray computed tomography(CT) and image analysis techniques. Based on the results, compared with the AC-5 sample, the OGFC-5mixture has a higher air void ratio, a larger air void size and a greater number of air voids, with the distribution of internal air voids being more uniform and their shapes being more rounded. The two-parameter Weibull function was applied to fit the gradation of air voids. The fitting results is good, and the function parameters are sensitive to changes in both mineral gradation and compaction method. Moreover, two homogeneity indices were proposed to evaluate the compaction uniformity of UAFC samples. Compared with the Marshall method,the SGC method is more conducive to improve the compaction uniformity of UAFC samples. The compaction method significantly influences the air void distribution characteristics and compaction uniformity of AC-5sample, but has a less significant impact on OGFC-5 sample. The experimental results in the study provides a solid foundation for further explorations on the internal structure and mixture design of UAFC.
基金The project supported by the Foundation of Zhongshan University Advanced Research Center
文摘According to the basic idea of dual-complementarity,in a simple and unified way proposed by the author,some basic principles in dynamic theory of elastic materials with voids can be established sys- tematically.In this paper, an important integral relation in terms of convolutions is given,which can be con- sidered as the generalized principle of virtual work in mechanics.Based on this relation,it is possible not on- ly to obtain the principle of virtual work and the reciprocal theorem in dynamic theory of elastic materials with voids,but also to derive systematically the complementary functionals for the eight-field,six-field, four-field and two-field simplified Gurtin-type variational principles.Furthermore,with this approach,the in- trinsic relationship among various principles can be explained clearly.
文摘From the Boltzmann's constitutive law of viscoelastic materials and the linear theory of elastic materials with voids, a constitutive model of generalized force fields for viscoelastic solids with voids was given. By using the variational integral method, the convolution-type functional was given and the corresponding generalized variational principles and potential energy principle of viscoelastic solids with voids were presented. It can be shown that the variational principles correspond to the differential equations and the initial and boundary conditions of viscoelastic body with voids. As an application, a generalized variational principle of viscoelastic Timoshenko beams with damage was obtained which corresponds to the differential equations of generalized motion and the initial and boundary conditions of beams. The variational principles provide a way for solving problems of viscoelastic solids with voids.
文摘The development of pores in a clastic reservoir is one of the most important research subjects in oil-gas exploration and development, whereas the many reasons for the formation of secondary porosity have increased the degree of difficulty in such research. Thus the research aims are to discover the controlling factors of solutional voids in feldspars and to predict favorable regions for these voids. Macroscopic and systematic researches into the relationship between the kaolinite content in the feldspar solutional void developed area of the Chang 2 reservoir group of the Triassic Yanchang Formation in the Midwest Ordos Basin and the solutional void in feldspar have been made, and from this it can be determined that the kaolinite content has an indicative function to the distribution of the solutional void in feldspar. Solutional void in feldspar is relatively well developed at the area where kaolinite content is high. Although the factors affecting kaolinite content are complicated, yet that of the research area is mainly affected by the impact of the leaching atmospheric water acting on the palaeogeomorphology. Three favorable zone belts for the development of solutional voids in feldspars are forecasted on the basis of restoration of palaeogeomorphology.
基金The project supported by the National Natural Science Foundation of China
文摘A mechanism of plastic how localization in ductile matter near microvoids is studied. The voids with the size-scale of micromillimeter exist in sheet specimens under tensile loading, and the plastic strain held around voids is obtained by digital image processing of deformed grids. The size growth of the microvoids, the spacing change of the neighboring voids, and the development of shear bands in the ligament between the voids, are presented by experimental results accompanied with the plastic strain distribution, that gives good interpretation to the process of void growth and coalescence with the how localization in the ligaments.
基金the National Key Research and Development Program of China(Grant No.2017YFB0404100)the National Natural Science Foundation of China(Grant Nos.61827813,61974144,and 62004127)+2 种基金the Key Research Program of the Chinese Academy of Sciences(Grant No.XDPB22)the Key-Area Research and Development Program of Guangdong Province,China(Grant Nos.2020B010169001 and 2020B010174003)the Science and Technology Foundation of Shenzhen(Grant No.JSGG20191129114216474)。
文摘Introducing voids into AlN layer at a certain height using a simple method is meaningful but challenging.In this work,the AlN/sapphire template with AlN interlayer structure was designed and grown by metal-organic chemical vapor deposition.Then,the AlN template was annealed at 1700℃for an hour to introduce the voids.It was found that voids were formed in the AlN layer after high-temperature annealing and they were mainly distributed around the AlN interlayer.Meanwhile,the dislocation density of the AlN template decreased from 5.26×10^(9)cm^(-2)to 5.10×10^(8)cm^(-2).This work provides a possible method to introduce voids into AlN layer at a designated height,which will benefit the design of AlN-based devices.
文摘This work aims at designing a set of curing pressure routes to produce laminates with various void contents. The effects of various consolidation pressures resulting in different void contents on mechanical strength of carbon/epoxy laminates have been examined. Characterization of the voids, in terms of void volume fraction, void distribution, size, and shape, was performed by standard test, ultrasonic inspection and metallographic analysis. The interlaminar shear strength was measured by the short-beam method. An empirical model was used to predict the strength vs porosity. The predicted strengths conform well with the experimental data and voids were found to be uniformly distributed throughout the laminate.
