The surrounding rock of roadways exhibits intricate characteristics of discontinuity and heterogeneity.To address these complexities,this study employs non-local Peridynamics(PD)theory and reconstructs the kernel func...The surrounding rock of roadways exhibits intricate characteristics of discontinuity and heterogeneity.To address these complexities,this study employs non-local Peridynamics(PD)theory and reconstructs the kernel function to represent accurately the spatial decline of long-range force.Additionally,modifications to the traditional bondbased PD model are made.By considering the micro-structure of coal-rock materials within a uniform discrete model,heterogeneity characterized by bond random pre-breaking is introduced.This approach facilitates the proposal of a novel model capable of handling the random distribution characteristics of material heterogeneity,rendering the PD model suitable for analyzing the deformation and failure of heterogeneous layered coal-rock mass structures.The established numerical model and simulation method,termed the sub-homogeneous PD model,not only incorporates the support effect but also captures accurately the random heterogeneous micro-structure of roadway surrounding rock.The simulation results obtained using this model show good agreement with field measurements from the Fucun coal mine,effectively validating the model’s capability in accurately reproducing the deformation and failure mode of surrounding rock under bolt-supported(anchor cable).The proposed subhomogeneous PD model presents a valuable and effective simulation tool for studying the deformation and failure of roadway surrounding rock in coal mines,offering new insights and potential advancements.展开更多
The effects of ultrafine WC(WC_(UF),0.5μm) or W(1μm) and C(0.3μm)(W+C)_(UF) additives on the densification,microstructure and mechanical properties of coarse-grained cemented carbides were compared systematically.O...The effects of ultrafine WC(WC_(UF),0.5μm) or W(1μm) and C(0.3μm)(W+C)_(UF) additives on the densification,microstructure and mechanical properties of coarse-grained cemented carbides were compared systematically.Overall,the cemented carbides with WC_(UF)/(W+C)_(UF) additives are almost fully densification to be higher than 99%,and the average grain size is kept above 2.8μm.The WC_(UF) additive assists grains to(truncated)trigonal prism shape by two dimensional(2D) growth,whereas the(W+C)_(UF) additive assists grains to rounded shape by three dimensional(3D) growth,lowers WC contiguity and increases face-centered-cubic Co.The hardness and bending strength of(75WC_(C)-15WC_(UF))-10Co are 86.6 HRA and 2 272 MPa,respectively,both higher than those of(75WC_(C)-15(W+C)_(UF))-10Co,which could be ascribed to the enhanced densification and unblemished grains.However,the fracture toughness of the(75WC_(C)-15(W+C)_(UF))-10Co is 23.5 MPa·m^(1/2),higher than that of the(75WC_(C)-15WC_(UF))-10Co due to the uniform WC-Co structure and flexible binder phase.展开更多
The concept of soft matter was first introduced by P. G. de Gennes in his acceptance speech for the No-bel Physics Prize in 1991. In mechanics community, however, people usually prefer using soft material in-stead of ...The concept of soft matter was first introduced by P. G. de Gennes in his acceptance speech for the No-bel Physics Prize in 1991. In mechanics community, however, people usually prefer using soft material in-stead of soft matter to describe the material whose en-ergy associated with thermal motion is comparative to the interaction energy. Unlike in the conventional con-densed matter, entropy plays an important and even de-terminative role in soft materials.展开更多
Calcareous sand is typically known as a problematic marine sediment because of its diverse morphology and complex inner pore structure.However,the coupling effects of morphology and inner pores on the mechanical prope...Calcareous sand is typically known as a problematic marine sediment because of its diverse morphology and complex inner pore structure.However,the coupling effects of morphology and inner pores on the mechanical properties of calcareous sand particles have rarely been investigated and understood.In this study,apparent contours and internal pore distributions of calcareous sand particles were obtained by three-dimensional(3D)scanning imaging and X-ray micro-computed tomography(X-mCT),respectively.It was revealed that calcareous sand particles with different outer morphologies have different porosities and inner pore distributions because of their original sources and particle transport processes.In addition,a total of 120 photo-related compression tests and 4923D discrete element simulations of four specific shaped particles,i.e.bulky,angular,dendritic and flaky,with variations in the inner pore distribution were conducted.The macroscopic particle strength and Weibull modulus obtained from the physical tests are not positively correlated with the porosity or regularity in shape,indicating the existence of coupling effect of particle shape and pore distribution.The shape effect on the particle strength first increases with the porosity and then decreases.The particle crushing of relatively regular particles is governed by the porosity,but that of extremely irregular particles is governed by the particle shape.The particle strength increases with the uniformity of the pore distribution.Particle fragmentation is mainly dependant on tensile bond strength,and the degree of tensile failure is considerably impacted by the particle shape but limited by the pore distribution.展开更多
In this work,an acoustic topology optimizationmethod for structural surface design covered by porous materials is proposed.The analysis of acoustic problems is performed using the isogeometric boundary elementmethod.T...In this work,an acoustic topology optimizationmethod for structural surface design covered by porous materials is proposed.The analysis of acoustic problems is performed using the isogeometric boundary elementmethod.Taking the element density of porousmaterials as the design variable,the volume of porousmaterials as the constraint,and the minimum sound pressure or maximum scattered sound power as the design goal,the topology optimization is carried out by solid isotropic material with penalization(SIMP)method.To get a limpid 0–1 distribution,a smoothing Heaviside-like function is proposed.To obtain the gradient value of the objective function,a sensitivity analysis method based on the adjoint variable method(AVM)is proposed.To find the optimal solution,the optimization problems are solved by the method of moving asymptotes(MMA)based on gradient information.Numerical examples verify the effectiveness of the proposed topology optimization method in the optimization process of two-dimensional acoustic problems.Furthermore,the optimal distribution of sound-absorbingmaterials is highly frequency-dependent and usually needs to be performed within a frequency band.展开更多
With the great impetus of energy conservation and emission reduction policies in various countries,the proposal of concepts such as“Sponge City”and“Eco-City”,and the emphasis on restoration and governance of ecolo...With the great impetus of energy conservation and emission reduction policies in various countries,the proposal of concepts such as“Sponge City”and“Eco-City”,and the emphasis on restoration and governance of ecological environment day by day,portland cement porous concrete(PCPC),as a novel building material,has attracted more and more attention from scientific researchers and engineers.PCPC possesses the peculiar pore structure,which owns numerous functions like river embankment protection,vegetation greening as well as air-cleaning,and has been of wide application in different engineering fields.This paper reviews the salient properties of PCPC,detailedly expounds the research progress of domestic and foreign literature about this subject in the past ten years(2010–2020),conducts the statistical analysis of the distribution rule of its major properties around the world,combines with the engineering application to summarize the excellent properties of PCPC,and makes a forecast of future research direction.展开更多
Citric acid(CA)and chitosan(CS)were employed to modify magnesium oxychloride cement(MOC).Multiscale measurements were implemented to study the properties of the modified MOC pastes.Results show that the addition of CA...Citric acid(CA)and chitosan(CS)were employed to modify magnesium oxychloride cement(MOC).Multiscale measurements were implemented to study the properties of the modified MOC pastes.Results show that the addition of CA/CS significantly changes the content of each phase and the microstructure of phase 5.The single addition of CA can effectively increase the compressive strength of MOC after 7 d curing,while CS exerts no obvious effect on the compressive strength.As to the simultaneous addition of CA and CS,the compressive strength of MOC gradually decreases with the increasing content of CS.Interestingly,mixing CA and CS significantly enhances the water resistance of MOC and decreases the degradation rate of MOC in phosphate buffered solution,which can be ascribed to the low specific surface area of the plate-like crystals in the modified MOC and the reduction of pores in the structure.展开更多
In this paper,the effects of different influencing factors and factor interaction on the compressive strength and permeability of recycled aggregate pervious concrete(RAPC)were studied based on the response surface me...In this paper,the effects of different influencing factors and factor interaction on the compressive strength and permeability of recycled aggregate pervious concrete(RAPC)were studied based on the response surface method(RSM).By selecting the maximum aggregate size,water cement ratio and target porosity as design variables,combined with laboratory tests and numerical analysis,the influences of three factors on the compressive strength and permeability coefficient of RAPC were revealed.The regression equation of compressive strength and permeability coefficient of recycled aggregate pervious concrete were established based on RSM,and the response surface model was optimized to determine the optimal ratio of RAPC under the conditions of meeting the mechanical and permeability properties.The results show that the mismatch item of the model is not significant,the model is credible,and the accuracy and reliability of the test are high,but the degree of uncorrelation between the test data and the model is not obvious.The sensitivity of the three factors to the compressive strength is water cement ratio>maximum coarse aggregate particle size>target porosity,and the sensitivity to the permeability coefficient is target porosity>maximum coarse aggregate particle size>water cement ratio.The absolute errors of the model prediction results and the model optimization results are 1.28 MPa and 0.19 mm/s,and the relative errors are 5.06%and 4.19%,respectively.With high accuracy,RSM can match the measured results of compressive strength and permeability coefficient of RAPC.展开更多
A novel three-dimensional-fiber reinforced soft pneumatic actuator(3D-FRSPA)inspired by crab claw and human hand structure that can bend and deform independently in each segment is proposed.It has an omni-directional ...A novel three-dimensional-fiber reinforced soft pneumatic actuator(3D-FRSPA)inspired by crab claw and human hand structure that can bend and deform independently in each segment is proposed.It has an omni-directional bending configuration,and the fibers twined symmetrically on both sides to improve the bending performance of FRSPA.In this paper,the static and kinematic analysis of 3D-FRSPA are carried out in detail.The effects of fiber,pneumatic chamber and segment length,and circular air chamber radius of 3D-FRSPA on the mechanical performance of the actuator are discussed,respectively.The soft mobile robot composed of 3D-FRSPA has the ability to crawl.Finally,the crawling processes of the soft mobile robot on different road conditions are studied,respectively,and the motion mechanism of the mobile actuator is shown.The numerical results show that the soft mobile robots have a good comprehensive performance,which verifies the correctness of the proposedmodel.This work shows that the proposed structures have great potential in complex road conditions,unknown space detection and other operations.展开更多
Isogeometric analysis (IGA) is known to showadvanced features compared to traditional finite element approaches.Using IGA one may accurately obtain the geometrically nonlinear bending behavior of plates with functiona...Isogeometric analysis (IGA) is known to showadvanced features compared to traditional finite element approaches.Using IGA one may accurately obtain the geometrically nonlinear bending behavior of plates with functionalgrading (FG). However, the procedure is usually complex and often is time-consuming. We thus put forward adeep learning method to model the geometrically nonlinear bending behavior of FG plates, bypassing the complexIGA simulation process. A long bidirectional short-term memory (BLSTM) recurrent neural network is trainedusing the load and gradient index as inputs and the displacement responses as outputs. The nonlinear relationshipbetween the outputs and the inputs is constructed usingmachine learning so that the displacements can be directlyestimated by the deep learning network. To provide enough training data, we use S-FSDT Von-Karman IGA andobtain the displacement responses for different loads and gradient indexes. Results show that the recognition erroris low, and demonstrate the feasibility of deep learning technique as a fast and accurate alternative to IGA formodeling the geometrically nonlinear bending behavior of FG plates.展开更多
Galvanic corrosion behavior of AZ91D alloy/45 steel couple in 3.5 wt.%NaCl solution under 0,0.2 and 0.4 T magnetic field were studied by microstructure observation,immersion test and electrochemical measurement.The mi...Galvanic corrosion behavior of AZ91D alloy/45 steel couple in 3.5 wt.%NaCl solution under 0,0.2 and 0.4 T magnetic field were studied by microstructure observation,immersion test and electrochemical measurement.The mixed potential theory was used to estimate the galvanic current density and the mixed potential of the galvanic corrosion between AZ91D alloy and 45 steel.The results indicated that magnetic field could accelerate the corrosion of AZ91D alloy,and impede the corrosion process of 45 steel.The effect of magnetic field on corrosion sensibility and corrosion rate of these two alloys increased as the intensity rising.The galvanic corrosion rate of the couple was accelerated by magnetic field.With the magnetic field intensity rising,the galvanic corrosion sensibility and corrosion rate of the couple increased.The effects of magnetic field on the galvanic corrosion performance of the couple and the corrosion behavior of AZ91D alloy and 45 steel were due to the appearance of field gradient force and magnetohydrodynamic(MHD)force.The mixed potential theory has a certain accuracy to estimate the Ecouple and icouple values in this work.展开更多
Accurate simulation of the cracking process caused by rust expansion of reinforced concrete(RC)structures plays an intuitive role in revealing the corrosion-induced failure mechanism.Considering the quasi-brittle frac...Accurate simulation of the cracking process caused by rust expansion of reinforced concrete(RC)structures plays an intuitive role in revealing the corrosion-induced failure mechanism.Considering the quasi-brittle fracture of concrete,the fracture phase field driven by the compressive-shear term is constructed and added to the traditional brittle fracture phase field model.The rationality of the proposed model is verified by a mixed fracture example under a shear displacement load.Then,the extended fracture phase model is applied to simulate the corrosion-induced cracking process of RC.The cracking patterns caused by non-uniform corrosion expansion are discussed for RC specimens with homogeneous macroscopically or heterogeneous with different polygonal aggregate distributions at the mesoscopic scale.Then,the effects of the protective layer on the crack propagation trajectory and cracking resistance are investigated,illustrating that the cracking angle and cracking resistance increase with the increase of the protective layer thickness,consistent with the experimental observation.Finally,the corrosion-induced cracking process of concrete specimens with large and small spacing rebars is simulated,and the interaction of multiple corrosion cracking is easily influenced by the reinforcement spacing,which increases with the decrease of the steel bar interval.These conclusions play an important role in the design of engineering anti-corrosion measures.The fracture phase field model can provide strong support for the life assessment of RC structures.展开更多
Foam is utilized in enhanced oil recovery and CO_(2) sequestration.Surfactant-alternating-gas(SAG)is a preferred approach for placing foam into reservoirs,due to it enhances gas injection and minimizes corrosion in fa...Foam is utilized in enhanced oil recovery and CO_(2) sequestration.Surfactant-alternating-gas(SAG)is a preferred approach for placing foam into reservoirs,due to it enhances gas injection and minimizes corrosion in facilities.Our previous studies with similar permeability cores show that during SAG injection,several banks occupy the area near the well where fluid exhibits distinct behaviour.However,underground reservoirs are heterogeneous,often layered.It is crucial to understand the effect of permeability on fluid behaviour and injectivity in a SAG process.In this work,coreflood experiments are conducted in cores with permeabilities ranging from 16 to 2300 mD.We observe the same sequence of banks in cores with different permeabilities.However,the speed at which banks propagate and their overall mobility can vary depending on permeability.At higher permeabilities,the gas-dissolution bank and the forced-imbibition bank progress more rapidly during liquid injection.The total mobilities of both banks decrease with permeability.By utilizing a bank-propagation model,we scale up our experimental findings and compare them to results obtained using the Peaceman equation.Our findings reveal that the liquid injectivity in a SAG foam process is misestimated by conventional simulators based on the Peaceman equation.The lower the formation permeability,the greater the error.展开更多
This paper presents an efficient numerical technique for solving multi-term linear systems of fractional ordinary differential equations(FODEs)which have been widely used in modeling various phenomena in engineering a...This paper presents an efficient numerical technique for solving multi-term linear systems of fractional ordinary differential equations(FODEs)which have been widely used in modeling various phenomena in engineering and science.An approximate solution of the system is sought in the formof the finite series over the Müntz polynomials.By using the collocation procedure in the time interval,one gets the linear algebraic system for the coefficient of the expansion which can be easily solved numerically by a standard procedure.This technique also serves as the basis for solving the time-fractional partial differential equations(PDEs).The modified radial basis functions are used for spatial approximation of the solution.The collocation in the solution domain transforms the equation into a system of fractional ordinary differential equations similar to the one mentioned above.Several examples have verified the performance of the proposed novel technique with high accuracy and efficiency.展开更多
Calcareous sand has distinct characteristics in comparison with silica sand, such as dynamic behavior at high strain rates(HSRs). This is closely related to pile driving, aircraft wheel loading and mining activities. ...Calcareous sand has distinct characteristics in comparison with silica sand, such as dynamic behavior at high strain rates(HSRs). This is closely related to pile driving, aircraft wheel loading and mining activities. To understand the response of calcareous sand at HSRs, a series of dynamic tests is performed using the split Hopkinson pressure bar(SHPB) with steel sleeve, including 6 validation tests of bar-against-bar and 16 comparative tests relevant to the relative density and strain rate of calcareous and silica sands.The apparent dynamic stiffness of calcareous sand is approximately 10% of that for silica sand due to different particle shapes and mineral compositions. The axial stress-strain response of silica sand is mainly governed by the deformation of individual grain and soil skeleton, and particle crushing. However, porous calcareous sand shows yielding and strain-hardening responses that are always followed by particle crushing. As the applied loading increases, the particle crushing of calcareous sand develops from local instability to whole breakage. Calcareous sand has lower viscous flow effects compared with silica sand at HSRs.展开更多
Mg-Y-Zn alloys with long period stacking ordered(LPSO)structure have received much attention recently and exhibit great potential in applications such as automotive,aerospace and in bio-medical fields.This paper aimed...Mg-Y-Zn alloys with long period stacking ordered(LPSO)structure have received much attention recently and exhibit great potential in applications such as automotive,aerospace and in bio-medical fields.This paper aimed to investigate the effect of different phase constitution of LPSO structures on corrosion rate of bio-medical Mg-Y-Zn alloys.The results showed that as-cast Mg98.5Y1Zn0.5 alloys containing only 18R structure exhibited the highest corrosion resistance with the corrosion rate of 2.78 mm/year.The precipitation of 14H lamellas within a-Mg grains during solid solution treatment introduced the crystallographic orientation corrosion by accelerating micro-galvanic corrosion.The increase of 18R/14H interfaces deteriorated the corrosion resistance,and the grain boundaries also suffered from severe electrochemical dissolution.This work suggested that Mg-Y-Zn alloys with single LPSO structure(either 18R or 14H)exhibited better corrosion resistance than alloys with co-existence 18R and I4H LPSO structures.展开更多
A model of Suzhou water resources carrying capacity （WRCC） was set up using the method of system dynamics （SD）. In the model, three different water resources utilization programs were adopted： （1） continuity of...A model of Suzhou water resources carrying capacity （WRCC） was set up using the method of system dynamics （SD）. In the model, three different water resources utilization programs were adopted： （1） continuity of existing water utilization, （2） water conservation/saving, and （3） water exploitation. The dynamic variation of the Suzhou WRCC was simulated with the supply-decided principle for the time period of 2001 to 2030, and the results were characterized based on socio-economic factors. The corresponding Suzhou WRCC values for several target years were calculated by the model. Based on these results, proper ways to improve the Suzhou WRCC are proposed. The model also produced an optimized plan, which can provide a scientific basis for the sustainable utilization of Suzhou water resources and for the coordinated development of the society, economy, and water resources.展开更多
In this work,a high-strength Mg–10Gd–6Y–1.5Zn–0.5Zr(wt.%)alloy was fabricated by successive multi-pass equal channel angular pressing(ECAP).The microstructure and mechanical property of as-cast and ECAP alloys wer...In this work,a high-strength Mg–10Gd–6Y–1.5Zn–0.5Zr(wt.%)alloy was fabricated by successive multi-pass equal channel angular pressing(ECAP).The microstructure and mechanical property of as-cast and ECAP alloys were systematically researched by X-ray diffractometer,scanning electron microscopy,transmission electron microscopy and compression test.The results show that the microstructure of as-cast alloy consists ofα-Mg grains,Mg24Y5 networks,18R blocks,fine 14H lamellas,and fewY-rich particles.After 8 passes ECAP,dynamic recrystallization ofα-Mg is developed and their average grain size decreases to about 1μm.The network Mg_(24)Y_(5) phase at grain boundaries is broken into small particles with average diameter lower than 0.5μm.Moreover,18R blocks are kinked and delaminated,or broken into small particles and blended with Mg24Y5 particles.14H lamellas grow gradually or are dynamically precipitated within certainα-Mg grains.Compression tests indicate that 8p ECAP alloy exhibits excellent mechanical property with compressive strength of 537 MPa and fracture strain of 17.0%.The significant improvement for both strength and ductility of deformed alloy could be ascribed to DRX grains,refined Mg24Y5 particles,18R kinking and dynamical precipitation of 14H.展开更多
A liquid sloshing experimental rig driven by a wave-maker is designed and built to study liquid sloshing problems in a rectangular liquid tank with perforated baffle. A series of experiments are conducted in this expe...A liquid sloshing experimental rig driven by a wave-maker is designed and built to study liquid sloshing problems in a rectangular liquid tank with perforated baffle. A series of experiments are conducted in this experimental rig to estimate the free surface fluctuation and pressure distribution by changing external excitation frequency of the shaking table. An in-house CFD code is also used in this study to simulate the liquid sloshing in three-dimensional （3D） rectangular tank with perforated baffle. Good agreements of free surface elevation and pressure between the numerical results and the experimental data are obtained and presented. Spectral analysis of the time history of free surface elevation is conducted by using the fast Fourier transformation.展开更多
In the present work,AZ91 alloy was successfully processed by equal channel angular pressing(ECAP)for up to 16 passes and rolling(R)for multiple passes with a total reduction of 75%in addition to a combination method w...In the present work,AZ91 alloy was successfully processed by equal channel angular pressing(ECAP)for up to 16 passes and rolling(R)for multiple passes with a total reduction of 75%in addition to a combination method with ECAP plus rolling(ECAP+R).The effects of various processes(ECAP,R and ECAP+R)on microstructure evolution were analyzed and the influence of ECAP process on the rolling performance was examined.The result shows that ECAP contributed to a homogenous grain structure and formed a texture with higher Schmidt factors that was easy for rolling.A plate with smoother surface and reduced edge cracks was observed in the ECAP+R process than in the single R process.Although the microstructure of the alloy was similar after ECAP+R and R process,the sample of ECAP+R was more refined and had stronger second phase precipitation than the sample of R,which resulted in better rolling characteristics,along with the external surfaces.展开更多
基金supported by the National Natural Science Foundation of China(Nos.12302264,52104004,12072170,and 12202225)the Natural Science Foundation of Shandong Province(No.ZR2021QA042)Special Fund for Taishan Scholar Project(No.Tsqn202211180).
文摘The surrounding rock of roadways exhibits intricate characteristics of discontinuity and heterogeneity.To address these complexities,this study employs non-local Peridynamics(PD)theory and reconstructs the kernel function to represent accurately the spatial decline of long-range force.Additionally,modifications to the traditional bondbased PD model are made.By considering the micro-structure of coal-rock materials within a uniform discrete model,heterogeneity characterized by bond random pre-breaking is introduced.This approach facilitates the proposal of a novel model capable of handling the random distribution characteristics of material heterogeneity,rendering the PD model suitable for analyzing the deformation and failure of heterogeneous layered coal-rock mass structures.The established numerical model and simulation method,termed the sub-homogeneous PD model,not only incorporates the support effect but also captures accurately the random heterogeneous micro-structure of roadway surrounding rock.The simulation results obtained using this model show good agreement with field measurements from the Fucun coal mine,effectively validating the model’s capability in accurately reproducing the deformation and failure mode of surrounding rock under bolt-supported(anchor cable).The proposed subhomogeneous PD model presents a valuable and effective simulation tool for studying the deformation and failure of roadway surrounding rock in coal mines,offering new insights and potential advancements.
基金Funded by the Technology Innovation Leading Program of Shaanxi(No.2022QFY08-02)。
文摘The effects of ultrafine WC(WC_(UF),0.5μm) or W(1μm) and C(0.3μm)(W+C)_(UF) additives on the densification,microstructure and mechanical properties of coarse-grained cemented carbides were compared systematically.Overall,the cemented carbides with WC_(UF)/(W+C)_(UF) additives are almost fully densification to be higher than 99%,and the average grain size is kept above 2.8μm.The WC_(UF) additive assists grains to(truncated)trigonal prism shape by two dimensional(2D) growth,whereas the(W+C)_(UF) additive assists grains to rounded shape by three dimensional(3D) growth,lowers WC contiguity and increases face-centered-cubic Co.The hardness and bending strength of(75WC_(C)-15WC_(UF))-10Co are 86.6 HRA and 2 272 MPa,respectively,both higher than those of(75WC_(C)-15(W+C)_(UF))-10Co,which could be ascribed to the enhanced densification and unblemished grains.However,the fracture toughness of the(75WC_(C)-15(W+C)_(UF))-10Co is 23.5 MPa·m^(1/2),higher than that of the(75WC_(C)-15WC_(UF))-10Co due to the uniform WC-Co structure and flexible binder phase.
文摘The concept of soft matter was first introduced by P. G. de Gennes in his acceptance speech for the No-bel Physics Prize in 1991. In mechanics community, however, people usually prefer using soft material in-stead of soft matter to describe the material whose en-ergy associated with thermal motion is comparative to the interaction energy. Unlike in the conventional con-densed matter, entropy plays an important and even de-terminative role in soft materials.
基金the Fundamental Research Funds for the Central Universities,China(Grant No.B210203032)the National Natural Science Foundation of China(Grant No.52279097)the Green and Blue Project of Jiangsu Province,China.
文摘Calcareous sand is typically known as a problematic marine sediment because of its diverse morphology and complex inner pore structure.However,the coupling effects of morphology and inner pores on the mechanical properties of calcareous sand particles have rarely been investigated and understood.In this study,apparent contours and internal pore distributions of calcareous sand particles were obtained by three-dimensional(3D)scanning imaging and X-ray micro-computed tomography(X-mCT),respectively.It was revealed that calcareous sand particles with different outer morphologies have different porosities and inner pore distributions because of their original sources and particle transport processes.In addition,a total of 120 photo-related compression tests and 4923D discrete element simulations of four specific shaped particles,i.e.bulky,angular,dendritic and flaky,with variations in the inner pore distribution were conducted.The macroscopic particle strength and Weibull modulus obtained from the physical tests are not positively correlated with the porosity or regularity in shape,indicating the existence of coupling effect of particle shape and pore distribution.The shape effect on the particle strength first increases with the porosity and then decreases.The particle crushing of relatively regular particles is governed by the porosity,but that of extremely irregular particles is governed by the particle shape.The particle strength increases with the uniformity of the pore distribution.Particle fragmentation is mainly dependant on tensile bond strength,and the degree of tensile failure is considerably impacted by the particle shape but limited by the pore distribution.
基金sponsored by Natural Science Foundation of Henan under Grant No.222300420498.
文摘In this work,an acoustic topology optimizationmethod for structural surface design covered by porous materials is proposed.The analysis of acoustic problems is performed using the isogeometric boundary elementmethod.Taking the element density of porousmaterials as the design variable,the volume of porousmaterials as the constraint,and the minimum sound pressure or maximum scattered sound power as the design goal,the topology optimization is carried out by solid isotropic material with penalization(SIMP)method.To get a limpid 0–1 distribution,a smoothing Heaviside-like function is proposed.To obtain the gradient value of the objective function,a sensitivity analysis method based on the adjoint variable method(AVM)is proposed.To find the optimal solution,the optimization problems are solved by the method of moving asymptotes(MMA)based on gradient information.Numerical examples verify the effectiveness of the proposed topology optimization method in the optimization process of two-dimensional acoustic problems.Furthermore,the optimal distribution of sound-absorbingmaterials is highly frequency-dependent and usually needs to be performed within a frequency band.
基金supported by the Jiangsu Water Conservancy Science and Technology Project of China(2016036).
文摘With the great impetus of energy conservation and emission reduction policies in various countries,the proposal of concepts such as“Sponge City”and“Eco-City”,and the emphasis on restoration and governance of ecological environment day by day,portland cement porous concrete(PCPC),as a novel building material,has attracted more and more attention from scientific researchers and engineers.PCPC possesses the peculiar pore structure,which owns numerous functions like river embankment protection,vegetation greening as well as air-cleaning,and has been of wide application in different engineering fields.This paper reviews the salient properties of PCPC,detailedly expounds the research progress of domestic and foreign literature about this subject in the past ten years(2010–2020),conducts the statistical analysis of the distribution rule of its major properties around the world,combines with the engineering application to summarize the excellent properties of PCPC,and makes a forecast of future research direction.
基金Funded by the National Natural Science Foundation of China(No.52071130)the Natural Science Foundation of Jiangsu Province(No.BK20211204)the Project of Outstanding Leading Talents in Gansu Province。
文摘Citric acid(CA)and chitosan(CS)were employed to modify magnesium oxychloride cement(MOC).Multiscale measurements were implemented to study the properties of the modified MOC pastes.Results show that the addition of CA/CS significantly changes the content of each phase and the microstructure of phase 5.The single addition of CA can effectively increase the compressive strength of MOC after 7 d curing,while CS exerts no obvious effect on the compressive strength.As to the simultaneous addition of CA and CS,the compressive strength of MOC gradually decreases with the increasing content of CS.Interestingly,mixing CA and CS significantly enhances the water resistance of MOC and decreases the degradation rate of MOC in phosphate buffered solution,which can be ascribed to the low specific surface area of the plate-like crystals in the modified MOC and the reduction of pores in the structure.
基金supported by the Jiangsu Water Conservancy Science and Technology Project of China(2016036).
文摘In this paper,the effects of different influencing factors and factor interaction on the compressive strength and permeability of recycled aggregate pervious concrete(RAPC)were studied based on the response surface method(RSM).By selecting the maximum aggregate size,water cement ratio and target porosity as design variables,combined with laboratory tests and numerical analysis,the influences of three factors on the compressive strength and permeability coefficient of RAPC were revealed.The regression equation of compressive strength and permeability coefficient of recycled aggregate pervious concrete were established based on RSM,and the response surface model was optimized to determine the optimal ratio of RAPC under the conditions of meeting the mechanical and permeability properties.The results show that the mismatch item of the model is not significant,the model is credible,and the accuracy and reliability of the test are high,but the degree of uncorrelation between the test data and the model is not obvious.The sensitivity of the three factors to the compressive strength is water cement ratio>maximum coarse aggregate particle size>target porosity,and the sensitivity to the permeability coefficient is target porosity>maximum coarse aggregate particle size>water cement ratio.The absolute errors of the model prediction results and the model optimization results are 1.28 MPa and 0.19 mm/s,and the relative errors are 5.06%and 4.19%,respectively.With high accuracy,RSM can match the measured results of compressive strength and permeability coefficient of RAPC.
基金work is supported by the Fundamental Research Funds for the Central Universities(Grant No.B230205021)the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(GrantNo.KYCX22_0592).The financial supports are gratefully acknowl-edged.
文摘A novel three-dimensional-fiber reinforced soft pneumatic actuator(3D-FRSPA)inspired by crab claw and human hand structure that can bend and deform independently in each segment is proposed.It has an omni-directional bending configuration,and the fibers twined symmetrically on both sides to improve the bending performance of FRSPA.In this paper,the static and kinematic analysis of 3D-FRSPA are carried out in detail.The effects of fiber,pneumatic chamber and segment length,and circular air chamber radius of 3D-FRSPA on the mechanical performance of the actuator are discussed,respectively.The soft mobile robot composed of 3D-FRSPA has the ability to crawl.Finally,the crawling processes of the soft mobile robot on different road conditions are studied,respectively,and the motion mechanism of the mobile actuator is shown.The numerical results show that the soft mobile robots have a good comprehensive performance,which verifies the correctness of the proposedmodel.This work shows that the proposed structures have great potential in complex road conditions,unknown space detection and other operations.
基金the National Natural Science Foundation of China(NSFC)under Grant Nos.12272124 and 11972146.
文摘Isogeometric analysis (IGA) is known to showadvanced features compared to traditional finite element approaches.Using IGA one may accurately obtain the geometrically nonlinear bending behavior of plates with functionalgrading (FG). However, the procedure is usually complex and often is time-consuming. We thus put forward adeep learning method to model the geometrically nonlinear bending behavior of FG plates, bypassing the complexIGA simulation process. A long bidirectional short-term memory (BLSTM) recurrent neural network is trainedusing the load and gradient index as inputs and the displacement responses as outputs. The nonlinear relationshipbetween the outputs and the inputs is constructed usingmachine learning so that the displacements can be directlyestimated by the deep learning network. To provide enough training data, we use S-FSDT Von-Karman IGA andobtain the displacement responses for different loads and gradient indexes. Results show that the recognition erroris low, and demonstrate the feasibility of deep learning technique as a fast and accurate alternative to IGA formodeling the geometrically nonlinear bending behavior of FG plates.
基金funded by“National Science Foundation of China(51909071)Natural Science Foundation of Jiangsu Province(BK20190493)+1 种基金the Fundamental Research Funds for the Central Universities(B220202040)Open Fund of Jiangsu Technical Center for Wind Energy Engineering(ZK22-03-08).”。
文摘Galvanic corrosion behavior of AZ91D alloy/45 steel couple in 3.5 wt.%NaCl solution under 0,0.2 and 0.4 T magnetic field were studied by microstructure observation,immersion test and electrochemical measurement.The mixed potential theory was used to estimate the galvanic current density and the mixed potential of the galvanic corrosion between AZ91D alloy and 45 steel.The results indicated that magnetic field could accelerate the corrosion of AZ91D alloy,and impede the corrosion process of 45 steel.The effect of magnetic field on corrosion sensibility and corrosion rate of these two alloys increased as the intensity rising.The galvanic corrosion rate of the couple was accelerated by magnetic field.With the magnetic field intensity rising,the galvanic corrosion sensibility and corrosion rate of the couple increased.The effects of magnetic field on the galvanic corrosion performance of the couple and the corrosion behavior of AZ91D alloy and 45 steel were due to the appearance of field gradient force and magnetohydrodynamic(MHD)force.The mixed potential theory has a certain accuracy to estimate the Ecouple and icouple values in this work.
基金the National Natural Science Foundation of China(Qing Zhang,Nos.11932006,U1934206,12172121)the Fundamental Research Funds for the Central Universities(Xin Gu,No.B210201031).
文摘Accurate simulation of the cracking process caused by rust expansion of reinforced concrete(RC)structures plays an intuitive role in revealing the corrosion-induced failure mechanism.Considering the quasi-brittle fracture of concrete,the fracture phase field driven by the compressive-shear term is constructed and added to the traditional brittle fracture phase field model.The rationality of the proposed model is verified by a mixed fracture example under a shear displacement load.Then,the extended fracture phase model is applied to simulate the corrosion-induced cracking process of RC.The cracking patterns caused by non-uniform corrosion expansion are discussed for RC specimens with homogeneous macroscopically or heterogeneous with different polygonal aggregate distributions at the mesoscopic scale.Then,the effects of the protective layer on the crack propagation trajectory and cracking resistance are investigated,illustrating that the cracking angle and cracking resistance increase with the increase of the protective layer thickness,consistent with the experimental observation.Finally,the corrosion-induced cracking process of concrete specimens with large and small spacing rebars is simulated,and the interaction of multiple corrosion cracking is easily influenced by the reinforcement spacing,which increases with the decrease of the steel bar interval.These conclusions play an important role in the design of engineering anti-corrosion measures.The fracture phase field model can provide strong support for the life assessment of RC structures.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.U2240210,52279098)the Natural Science Foundation of Jiangsu Province(Grant No.BK20200525)the Fundamental Research Funds for the Central Universities(Grant No.B230201021).We express our gratitude to PETRONAS and Shell Global Solution International B.V.for their support of this work.
文摘Foam is utilized in enhanced oil recovery and CO_(2) sequestration.Surfactant-alternating-gas(SAG)is a preferred approach for placing foam into reservoirs,due to it enhances gas injection and minimizes corrosion in facilities.Our previous studies with similar permeability cores show that during SAG injection,several banks occupy the area near the well where fluid exhibits distinct behaviour.However,underground reservoirs are heterogeneous,often layered.It is crucial to understand the effect of permeability on fluid behaviour and injectivity in a SAG process.In this work,coreflood experiments are conducted in cores with permeabilities ranging from 16 to 2300 mD.We observe the same sequence of banks in cores with different permeabilities.However,the speed at which banks propagate and their overall mobility can vary depending on permeability.At higher permeabilities,the gas-dissolution bank and the forced-imbibition bank progress more rapidly during liquid injection.The total mobilities of both banks decrease with permeability.By utilizing a bank-propagation model,we scale up our experimental findings and compare them to results obtained using the Peaceman equation.Our findings reveal that the liquid injectivity in a SAG foam process is misestimated by conventional simulators based on the Peaceman equation.The lower the formation permeability,the greater the error.
基金funded by the National Key Research and Development Program of China(No.2021YFB2600704)the National Natural Science Foundation of China(No.52171272)the Significant Science and Technology Project of the Ministry of Water Resources of China(No.SKS-2022112).
文摘This paper presents an efficient numerical technique for solving multi-term linear systems of fractional ordinary differential equations(FODEs)which have been widely used in modeling various phenomena in engineering and science.An approximate solution of the system is sought in the formof the finite series over the Müntz polynomials.By using the collocation procedure in the time interval,one gets the linear algebraic system for the coefficient of the expansion which can be easily solved numerically by a standard procedure.This technique also serves as the basis for solving the time-fractional partial differential equations(PDEs).The modified radial basis functions are used for spatial approximation of the solution.The collocation in the solution domain transforms the equation into a system of fractional ordinary differential equations similar to the one mentioned above.Several examples have verified the performance of the proposed novel technique with high accuracy and efficiency.
基金the support of the National Natural Science Foundation of China(Grant Nos.51779264and 51408607)the Natural Science Foundation of Jiangsu Province(Grant No.BK20171399)+1 种基金the Hong Kong Scholars Program(Grant No.2016QNRC001)the Young Elite Scientist Sponsorship(Grant No.17-JCJQ-QT-021)
文摘Calcareous sand has distinct characteristics in comparison with silica sand, such as dynamic behavior at high strain rates(HSRs). This is closely related to pile driving, aircraft wheel loading and mining activities. To understand the response of calcareous sand at HSRs, a series of dynamic tests is performed using the split Hopkinson pressure bar(SHPB) with steel sleeve, including 6 validation tests of bar-against-bar and 16 comparative tests relevant to the relative density and strain rate of calcareous and silica sands.The apparent dynamic stiffness of calcareous sand is approximately 10% of that for silica sand due to different particle shapes and mineral compositions. The axial stress-strain response of silica sand is mainly governed by the deformation of individual grain and soil skeleton, and particle crushing. However, porous calcareous sand shows yielding and strain-hardening responses that are always followed by particle crushing. As the applied loading increases, the particle crushing of calcareous sand develops from local instability to whole breakage. Calcareous sand has lower viscous flow effects compared with silica sand at HSRs.
基金the National Natural Science Foundation of China(Grant Nos.51774109 and 51979099)the Fundamental Research Funds for the Central Universities(Grant No.2018B48414 and 2018B690X14)+3 种基金Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX18_0570)The Key Research and Development Project of Jiangsu Province of China(Grant No.BE2017148)Postgraduate Education Reform Project of Jiangsu Province(JGLX19_027)Natural Science Foundation of China(Grant No.51979099).
文摘Mg-Y-Zn alloys with long period stacking ordered(LPSO)structure have received much attention recently and exhibit great potential in applications such as automotive,aerospace and in bio-medical fields.This paper aimed to investigate the effect of different phase constitution of LPSO structures on corrosion rate of bio-medical Mg-Y-Zn alloys.The results showed that as-cast Mg98.5Y1Zn0.5 alloys containing only 18R structure exhibited the highest corrosion resistance with the corrosion rate of 2.78 mm/year.The precipitation of 14H lamellas within a-Mg grains during solid solution treatment introduced the crystallographic orientation corrosion by accelerating micro-galvanic corrosion.The increase of 18R/14H interfaces deteriorated the corrosion resistance,and the grain boundaries also suffered from severe electrochemical dissolution.This work suggested that Mg-Y-Zn alloys with single LPSO structure(either 18R or 14H)exhibited better corrosion resistance than alloys with co-existence 18R and I4H LPSO structures.
基金supported by the National Natural Science Foundation of China (Grant No.50638020)
文摘A model of Suzhou water resources carrying capacity （WRCC） was set up using the method of system dynamics （SD）. In the model, three different water resources utilization programs were adopted： （1） continuity of existing water utilization, （2） water conservation/saving, and （3） water exploitation. The dynamic variation of the Suzhou WRCC was simulated with the supply-decided principle for the time period of 2001 to 2030, and the results were characterized based on socio-economic factors. The corresponding Suzhou WRCC values for several target years were calculated by the model. Based on these results, proper ways to improve the Suzhou WRCC are proposed. The model also produced an optimized plan, which can provide a scientific basis for the sustainable utilization of Suzhou water resources and for the coordinated development of the society, economy, and water resources.
基金the Natural Science Foundation of Jiangsu Province of China(No.BK20160869)the financial support from the Nantong Science and Technology Project(No.GY12015009)+1 种基金the Fundamental Research Funds for the Central Universities(No.2015B01314)the National Natural Science Foundation of China(No.51501039).
文摘In this work,a high-strength Mg–10Gd–6Y–1.5Zn–0.5Zr(wt.%)alloy was fabricated by successive multi-pass equal channel angular pressing(ECAP).The microstructure and mechanical property of as-cast and ECAP alloys were systematically researched by X-ray diffractometer,scanning electron microscopy,transmission electron microscopy and compression test.The results show that the microstructure of as-cast alloy consists ofα-Mg grains,Mg24Y5 networks,18R blocks,fine 14H lamellas,and fewY-rich particles.After 8 passes ECAP,dynamic recrystallization ofα-Mg is developed and their average grain size decreases to about 1μm.The network Mg_(24)Y_(5) phase at grain boundaries is broken into small particles with average diameter lower than 0.5μm.Moreover,18R blocks are kinked and delaminated,or broken into small particles and blended with Mg24Y5 particles.14H lamellas grow gradually or are dynamically precipitated within certainα-Mg grains.Compression tests indicate that 8p ECAP alloy exhibits excellent mechanical property with compressive strength of 537 MPa and fracture strain of 17.0%.The significant improvement for both strength and ductility of deformed alloy could be ascribed to DRX grains,refined Mg24Y5 particles,18R kinking and dynamical precipitation of 14H.
基金supported by the China Postdoctoral Science Foundation(Grant No.2012M511192)the National Natural Science Foundation of China(Grant Nos.51209080 and 51061130547+5 种基金Open Fund of State Key Laboratory of Coastaland Off shore Engineering(Grant No.LP1207the Open Fund of State Key Laboratory of Hydraulics and Mountain River Engineering(Grant No.1213)Qing Lan Project and 333 Project of Jiangsu Province(Grant No.BRA2012130)the Fundamental Research Funds for the Central Universities(Hohai University,Grant No.2012B06514the 111 Project(Grant No.B12032)Research Fund for the Doctoral Program of Higher Education of China(Grant No.20120181110084)
文摘A liquid sloshing experimental rig driven by a wave-maker is designed and built to study liquid sloshing problems in a rectangular liquid tank with perforated baffle. A series of experiments are conducted in this experimental rig to estimate the free surface fluctuation and pressure distribution by changing external excitation frequency of the shaking table. An in-house CFD code is also used in this study to simulate the liquid sloshing in three-dimensional （3D） rectangular tank with perforated baffle. Good agreements of free surface elevation and pressure between the numerical results and the experimental data are obtained and presented. Spectral analysis of the time history of free surface elevation is conducted by using the fast Fourier transformation.
基金This study was supported by the National Natural Science Foundation of China(51774109 and 51501039)the Key Research and Development Project of Jiangsu Province(BE2017148)+2 种基金the Postgraduate Research&Practice Innovation Program of Jiangsu Province of China(KYLX16_0701)the Fundamental Research Funds for the Central Universities(HHU2016B45314&2018B48414)Q.X.is grateful for the support from the China Scholarship Council and the W.M.Keck Center for Advanced Microscopy and Micr1oanalysis at University of Delaware.
文摘In the present work,AZ91 alloy was successfully processed by equal channel angular pressing(ECAP)for up to 16 passes and rolling(R)for multiple passes with a total reduction of 75%in addition to a combination method with ECAP plus rolling(ECAP+R).The effects of various processes(ECAP,R and ECAP+R)on microstructure evolution were analyzed and the influence of ECAP process on the rolling performance was examined.The result shows that ECAP contributed to a homogenous grain structure and formed a texture with higher Schmidt factors that was easy for rolling.A plate with smoother surface and reduced edge cracks was observed in the ECAP+R process than in the single R process.Although the microstructure of the alloy was similar after ECAP+R and R process,the sample of ECAP+R was more refined and had stronger second phase precipitation than the sample of R,which resulted in better rolling characteristics,along with the external surfaces.
