Effects of ultrasonic bonding parameters on atomic diffusion, microstructure at the Al-Au interface, and shear strength of Al-Au ultrasonic bonding were investigated by the combining experiments and finite element (FE...Effects of ultrasonic bonding parameters on atomic diffusion, microstructure at the Al-Au interface, and shear strength of Al-Au ultrasonic bonding were investigated by the combining experiments and finite element (FE) simulation. The quantitative model of atomic diffusion, which is related to the ultrasonic bonding parameters, time and distance, is established to calculate the atomic diffusion of the Al-Au interface. The maximum relative error between the calculated and experimental fraction of Al atom is 7.35%, indicating high prediction accuracy of this model. During the process of ultrasonic bonding, Au8Al3 is the main intermetallic compound (IMC) at the Al-Au interface. With larger bonding forces, higher ultrasonic powers and longer bonding time, it is more difficult to remove the oxide particles from the Al-Au interface, which hinders the atomic diffusion. Therefore, the complicated stress state and the existence of oxide particles both promotes the formation of holes. The shear strength of Al-Au ultrasonic bonding increases with increasing bonding force, ultrasonic power and bonding time. However, combined with the presence of holes at especial parameters, the optimal ultrasonic bonding parameter is confirmed to be a bonding force of 23 gf, ultrasonic power of 75 mW and bonding time of 21 ms.展开更多
In order to establish the relationship between the measured dynamic response and the health status of long-span bridges, a double-layer model updating method for steel-concrete composite beam cable-stayed bridges is p...In order to establish the relationship between the measured dynamic response and the health status of long-span bridges, a double-layer model updating method for steel-concrete composite beam cable-stayed bridges is proposed. Measured frequencies are selected as the first-layer reference data, and the mass of the bridge deck, the grid density, the modulus of concrete and the ballast on the side span are modified by using a manual tuning technique. Measured global positioning system （GPS） data is selected as the second-layer reference data, and the degradation of the integral structure stiffness EI of the whole bridge is taken into account for the second-layer model updating by using the finite element iteration algorithm. The Nanpu Bridge in Shanghai is taken as a case to verify the applicability of the proposed model updating method. After the first-layer model updating, the standard deviation of modal frequencies is smaller than 7%. After the second-layer model updating, the error of the deflection of the mid-span is smaller than 10%. The integral structure stiffness of the whole bridge decreases about 20%. The research results show a good agreement between the calculated response and the measured response.展开更多
This article introduces an element diffusion behavior model for a titanium/steel explosive clad plate characterized by a typical curved interface during the heat-treatment process. A series of heat-treatment experimen...This article introduces an element diffusion behavior model for a titanium/steel explosive clad plate characterized by a typical curved interface during the heat-treatment process. A series of heat-treatment experiments were conducted in the temperature range from 750℃ to 950℃, and the effects of heat-treatment parameters on the microstructural evolution and diffusion behavior were investigated by optical microscopy, scanning electron microscopy, X-ray diffraction analysis, and electron-probe microanalysis. Carbon atoms within the steel matrix were observed to diffuse toward the titanium matrix and to aggregate at the bonding interface at 850℃ or lower; in contrast, when the temperature exceeded 850℃, the mutual diffusion of Ti and Fe occurred, along with the diffusion of C atoms, resulting in the for- marion of Ti-Fe intermetallics （Fe2Ti/FeTi）. The diffusion distances of C, Ti, and Fe atoms increased with increasing heating temperature and/or holding time. On the basis of this diffusion behavior, a novel diffusion model was proposed. This model considers the effects of various factors, including the curvature radius of the curved interface, the diffusion coefficient, the heating temperature, and the holding rime. The experimental results show good agreement with the calculated values. The proposed model could clearly provide a general prediction of the elements＇ diffusion at both straight and curved interfaces.展开更多
This review presents a thorough survey of the roll bonding process with a focus on the bimetallic bars/tubes as well as the bonding models and criteria.The review aims to provide insight into cold,hot and cryogenic bo...This review presents a thorough survey of the roll bonding process with a focus on the bimetallic bars/tubes as well as the bonding models and criteria.The review aims to provide insight into cold,hot and cryogenic bonding mechanisms at the micro and atomic scale and act as a guide for researchers working on roll bonding,other joining processes and bonding simulation.Mean-while,the shortcomings of roll bonding processes are presented from the aspect of formable shapes,while bonding models are shown from the aspect of calculation time,convergence,interface behav-ior of dissimilar materials as well as hot bonding status prediction.Two well-accepted numerical methodologies of bonding models,namely the contact algorithm and cohesive zone model(CZM)of bonding models and in simulations of the bonding process are highlighted.Particularly,recent advances and trends in the application of the combination of mechanical interlocking and metallurgical bonding,special energy fields,gradient structure,novel materials,green technology and soft computing method in the roll bonding process are also discussed.The challenges for advancing and prospects of the roll bonding process and bonding model are presented in an attempt to shed some light on the future research direction.展开更多
Based on current theories of diffusion and creep cavity closure at high temperature, a theoretical analysis of phase transformation diffusion bonding for T8/T8 eutectoid steel is carried out. The diffusion bonding is ...Based on current theories of diffusion and creep cavity closure at high temperature, a theoretical analysis of phase transformation diffusion bonding for T8/T8 eutectoid steel is carried out. The diffusion bonding is mainly described as two-stage process: Ⅰ The interfacial cavity with shape change from diamond to cylinder.Ⅱ The radius of the cylindrical cavity are reduced and eliminated gradually. A new theoretical model is established for the process of transformation superplastic diffusion bonding (TSDB) on the basis of a theoretical model for isothermal superplastic diffusion. The model can predict the bonding quality which is affected by technological parameters, such as limit cycling temperature, the compressive stress, the numbers of thermal cycles and temperature cycling through the phase transformation in the thermal cycling and so on. Results show that the maximum temperature, the compressive stress, the numbers of thermal cycles and the rate of temperature changing speed in the thermal cycling have an important influence on TSDB process. Meanwhile, reasonable technological parameters chosen from theoretical analysis is in good agreement with those obtained from experimental results.展开更多
Based on twin-roll casting, a cast-rolling force model was proposed to predict the rolling force in the bimetal solid-liquid cast-rolling bonding(SLCRB) process. The solid-liquid bonding zone was assumed to be below t...Based on twin-roll casting, a cast-rolling force model was proposed to predict the rolling force in the bimetal solid-liquid cast-rolling bonding(SLCRB) process. The solid-liquid bonding zone was assumed to be below the kiss point(KP). The deformation resistance of the liquid zone was ignored. Then, the calculation model was derived. A 2D thermal-flow coupled simulation was established to provide a basis for the parameters in the model, and then the rolling forces of the Cu/Al clad strip at different rolling speeds were calculated. Meanwhile, through measurement experiments, the accuracy of the model was verified. The influence of the rolling speed, the substrate strip thickness, and the material on the rolling force was obtained. The results indicate that the rolling force decreases with the increase of the rolling speed and increases with the increase of the thickness and thermal conductivity of the substrate strip. The rolling force is closely related to the KP height. Therefore, the formulation of reasonable process parameters to control the KP height is of great significance to the stability of cast-rolling forming.展开更多
This study investigates the bond performance at the interfacial region shared by Ultra-High Performance Concrete(UHPC)and steel tubes through push-out tests.This study examines how changes in steel fiber volumetric ra...This study investigates the bond performance at the interfacial region shared by Ultra-High Performance Concrete(UHPC)and steel tubes through push-out tests.This study examines how changes in steel fiber volumetric ratio and thickness of steel tube influence the bond strength characteristics.The results show that as the enhancement of the steel tube wall thickness,the ultimate bond strength at the interface improves significantly,whereas the initial bond strength exhibits only slight variations.The influence of steel fiber volumetric ratio presents a nonlinear trend,with initial bond strength decreasing at low fiber content and increasing significantly as fiber content rises.Additionally,finite element(FE)simulations were applied to replicate the experimental conditions,and the outcomes showed strong correlation with the experimental data,confirming the exactitude of the FE model in predicting the bond behavior at the UHPC-Steel interface.These findings provide valuable insights for optimizing the design of UHPC-Filled steel tubes in high-performance structure.展开更多
A theoretical model which couples the oscillation of cavitation bubbles with the equation of an acoustic wave is utilized to describe the sound fields in double-layer liquids, which can be used to realize the asymmetr...A theoretical model which couples the oscillation of cavitation bubbles with the equation of an acoustic wave is utilized to describe the sound fields in double-layer liquids, which can be used to realize the asymmetric transmission of acoustic waves. Numerical simulations show that the asymmetry is related to the properties of the host liquids and the input acoustic wave. Asymmetry can be enhanced if the maximum number density or the ambient radius of the cavitation bubbles in the low cavitation threshold liquid increases. Moreover, the direction of rectification will be reversed if the amplitude of the input acoustic wave becomes high enough.展开更多
Bonding quality at the interface of solid propellant grains is crucial for the reliability and safety of solid rocket motors.Although bonding reliability is influenced by numerous factors,the lack of quantitative char...Bonding quality at the interface of solid propellant grains is crucial for the reliability and safety of solid rocket motors.Although bonding reliability is influenced by numerous factors,the lack of quantitative characterization of interface debonding mechanisms and the challenge of identifying key factors have made precise control of process variables difficult,resulting in unpredictable failure risks.This paper presents an improved fuzzy failure probability evaluation method that combines fuzzy fault tree analysis with expert knowledge,transforming process data into fuzzy failure probability to accurately assess debonding probabilities.The predictive model is constructed through a general regression neural network and optimized using the particle swarm optimization algorithm.Sensitivity analysis is conducted to identify key decision variables,including normal force,grain rotation speed,and adhesive weight,which are verified experimentally.Compared with classical models,the maximum error margin of the constructed reliability prediction model is only 0.02%,and it has high stability.The experimental results indicate that the main factors affecting debonding are processing roughness and coating uniformity.Controlling the key decision variable as the median resulted in a maximum increase of 200.7%in bonding strength.The feasibility of the improved method has been verified,confirming that identifying key decision variables has the ability to improve bonding reliability.The proposed method simplifies the evaluation of propellant interface bonding reliability under complex conditions by quantifying the relationship between process parameters and failure risk,enabling targeted management of key decision variables.展开更多
The oxidation of lignin model compounds to esters via C-C bond cleavage has attracted considerable attention,as esters could be used as important polymer precursors and pharmaceutical intermediates.However,most studie...The oxidation of lignin model compounds to esters via C-C bond cleavage has attracted considerable attention,as esters could be used as important polymer precursors and pharmaceutical intermediates.However,most studies focus on designing homogeneous or noble metal catalysts and conducting the reactions under basic conditions.Here,we report an efficient process for the C-C bond cleavage of lignin model compounds and selectively producing esters over different shaped CeO_(2)(i.e.,nanospheres(S),nanorods(R),nanoparticles(P),and nanocubes(C))under base-free conditions.Specifically,the yield of methyl anisate from the aerobic oxidation of l-(4-methoxyphenyl)ethanol reaches 77.6%over CeO_(2)-S in one hour(91%in 9 h),exhibiting higher performance compared to other evaluated CeO_(2)catalysts(6.4%-40.2%).Extensivecharacterizations and experimental investigations reveal that the density of weak base sites and oxygen vacancies on the CeO_(2)surface is positively correlated with the yield of methyl esters.Furthermore,the reaction pathway is investigated,which confirms that 1-(4-methoxyphenyl)ethanol first undergoes two reactions(i.e.,etherification and dehydrogenation)to produce intermediates of1-methoxy-4-(1-methoxy-ethyl)-benzene and 1-(4-methoxyphenyl)ethanone,respectively,followed by a series of functional group transformations to generate the targeted methyl anisate ultimately.展开更多
Systems with quenched disorder possess complex energy landscapes that are challenging to explore under conventional Monte Carlo methods.In this work,we implement an efficient entropy sampling scheme for accurate compu...Systems with quenched disorder possess complex energy landscapes that are challenging to explore under conventional Monte Carlo methods.In this work,we implement an efficient entropy sampling scheme for accurate computation of the entropy function in low-energy regions.The method is applied to the two-dimensional±J random-bond Ising model,where frustration is controlled by the fraction p of ferromagnetic bonds.We investigate the low-temperature paramagnetic–ferromagnetic phase boundary below the multicritical point at T_(N)=0.9530(4),P_(N)=0.89078(8),as well as the zerotemperature ferromagnetic–spin-glass transition.Finite-size scaling analysis reveals that the phase boundary for T<T_(N) exhibits reentrant behavior.By analyzing the evolution of the magnetizationresolved density of states g(E,M)and ground-state spin configurations against increasing frustration,we provide strong evidence that the zero-temperature transition is a mixed-order.Finite-size scaling conducted on the spin-glass side supports the validity of β=0,whereβis the magnetization exponent,with a correlation length exponentν=1.50(8).Our results provide new insights into the nature of the ferromagnetic-to-spin-glass phase transition in an extensively degenerate ground state.展开更多
Virtual organization is a new production patter and a principal part in advanced manufacturing systems such as agile manufacturing. Manufacturability evaluation is the necessary condition to form the virtual organizat...Virtual organization is a new production patter and a principal part in advanced manufacturing systems such as agile manufacturing. Manufacturability evaluation is the necessary condition to form the virtual organization. A new manufacturability evaluation approach is described in this paper, which is carried out based on every process feature under the double-layer model of manufacturing resources proposed by authors. The manufacturing resources that build up the virtual organization are selected according to the results of manufacturability evaluation.展开更多
The natural clayey soils are usually structural and unsaturated,which makes their mechanical properties quite different from the remolded saturated soils.A structural constitutive model is proposed to simulate the bon...The natural clayey soils are usually structural and unsaturated,which makes their mechanical properties quite different from the remolded saturated soils.A structural constitutive model is proposed to simulate the bonding-breakage micro-mechanism.In this model,the unsaturated soil element is divided into a cementation element and a friction element according to the binary medium theory,and the stress-strain coordination for these two elements is obtained. The cementation element is regarded as elastic,whereas the friction element is regarded as elastoplastic which can be described with the Gallipoli＇s model.The theoretical formulation is verified with the comparative experiments of isotropic compressions on the saturated and unsaturated structural soils.Parametric analyses of the effects of damage variables on the model predictions are further carried out,which show that breakage deformation of natural clayey soils increases with the rising amount of initial defects.展开更多
The particulate discrete element method(DEM) can be employed to capture the response of rock,provided that appropriate bonding models are used to cement the particles to each other.Simulations of laboratory tests are ...The particulate discrete element method(DEM) can be employed to capture the response of rock,provided that appropriate bonding models are used to cement the particles to each other.Simulations of laboratory tests are important to establish the extent to which those models can capture realistic rock behaviors.Hitherto the focus in such comparison studies has either been on homogeneous specimens or use of two-dimensional(2D) models.In situ rock formations are often heterogeneous,thus exploring the ability of this type of models to capture heterogeneous material behavior is important to facilitate their use in design analysis.In situ stress states are basically three-dimensional(3D),and therefore it is important to develop 3D models for this purpose.This paper revisits an earlier experimental study on heterogeneous specimens,of which the relative proportions of weaker material(siltstone) and stronger,harder material(sandstone) were varied in a controlled manner.Using a 3D DEM model with the parallel bond model,virtual heterogeneous specimens were created.The overall responses in terms of variations in strength and stiffness with different percentages of weaker material(siltstone) were shown to agree with the experimental observations.There was also a good qualitative agreement in the failure patterns observed in the experiments and the simulations,suggesting that the DEM data enabled analysis of the initiation of localizations and micro fractures in the specimens.展开更多
Only two macroscopic parameters are needed to describe the mechanical properties of linear elastic solids, i.e. the Poisson＇s ratio and Young＇s modulus. Correspondingly, there should be two microscopic parameters to...Only two macroscopic parameters are needed to describe the mechanical properties of linear elastic solids, i.e. the Poisson＇s ratio and Young＇s modulus. Correspondingly, there should be two microscopic parameters to determine the mechanical properties of material if the macroscopic mechanical properties of linear elastic solids are derived from the microscopic level. Enlightened by this idea, a multiscale mechanical model for material, the virtual multi-dimensional internal bonds （VMIB） model, is proposed by incorporating a shear bond into the virtual internal bond （VIB） model. By this modification, the VMIB model associates the macro mechanical properties of material with the microscopic mechanical properties of discrete structure and the corresponding relationship between micro and macro parameters is derived. The tensor quality of the energy density function, which contains coordinate vector, is mathematically proved. From the point of view of VMIB, the macroscopic nonlinear behaviors of material could be attributed to the evolution of virtual bond distribution density induced by the imposed deformation. With this theoretical hypothesis, as an application example, a uniaxial compressive failure of brittle material is simulated. Good agreement between the experimental results and the simulated ones is found.展开更多
This paper seeks to outline a novel three-layer model and a new birth-dteath element solution technique to evaluate static strength of notched metallic panel repaired with bonded com- posite patch and to optimize mate...This paper seeks to outline a novel three-layer model and a new birth-dteath element solution technique to evaluate static strength of notched metallic panel repaired with bonded com- posite patch and to optimize material parameters. The higher order 3D, 8-node isotropic solid ele- ment and 8-node anisotropic layered solid element with three degrees of freedom per node are respectively implemented to model substrate panel, adhesive layer and composite patch to establish three-layer model of repaired panel. The new solving technique based on birth-death element is developed to allow solution of the stress pattern of repaired panel for identifying failure mode. The new model and its solution are used to model failure mode and residual strength of repaired panel, and the obtained results have a good agreement with the experimental findings. Finally, the influences of material parameter of adhesive layer and composite patch on the residual strength of repaired panel are investigated for optimizing material properties to meet operational and envi- ronmental constraints.展开更多
This paper studies the critical behaviours and magnetic properties of three-dimensional bond and anisotropy dilution Blume-Capel model （BCM） in the presence of an applied field within the effective field theory. The...This paper studies the critical behaviours and magnetic properties of three-dimensional bond and anisotropy dilution Blume-Capel model （BCM） in the presence of an applied field within the effective field theory. The trajectory of tricritical point, reentrant transitions and degenerate patterns of anisotropy are obtained both for the bond and the anisotropy dilutions. The global phase diagrams demonstrate unusually reentrant phenomena. The temperature dependences of magnetization curves undergo remarkable spin glass behaviour at low temperatures, and transform from ferromagnetism to paramagnetism at high temperature in applied fields. Temperature dependence of magnetic susceptibility curve is in qualitative agreement with experimental result.展开更多
The velocity structures of flow through vertically double-layered vegetation(VDLV)as well as single-layered rigid vegetation(SLV)were investigated computationally with a three-dimensional(3D)Reynolds stress turbulence...The velocity structures of flow through vertically double-layered vegetation(VDLV)as well as single-layered rigid vegetation(SLV)were investigated computationally with a three-dimensional(3D)Reynolds stress turbulence model,using the computational fluid dynamics(CFD)code FLUENT.The detailed velocity distribution was explored with a varying initial Froude number(Fr),with consideration of the steady subcritical flow conditions of an inland tsunami.In VDLV flows,the numerical model successfully captured the inflection point in the profiles of mean streamwise velocities in the mixing-layer region around the top of short submerged vegetation.An upward and downward movement of flow occurred at the positions located just behind the tall and short vegetation,respectively.Overall,higher streamwise velocities were observed in the upper vegetation layer due to high porosity,with Pr=98%(sparse vegetation,where Pr is the porosity),as compared to those in the lower vegetation layer,which had comparatively low porosity,with Pr=91%(dense vegetation).A rising trend of velocities was found as the flow passed through the vegetation region,followed by a clear sawtooth distribution,as compared to the regions just upstream and downstream of vegetation where the flow was almost uniform.In VDLV flows,a rising trend in the flow resistance was observed with the increase in the initial Froude number,i.e.,Fr?0.67,0.70,and 0.73.However,the flow resistance in the case of SLV was relatively very low.The numerical results also show the flow structures within the vicinity of short and tall vegetation,which are difficult to attain through experimental measurements.展开更多
In this study,an overcasting process followed by a low-temperature(200°C)annealing schedule has been developed to bond magnesium to aluminum alloys.ProCAST software was used to optimize the process parameters dur...In this study,an overcasting process followed by a low-temperature(200°C)annealing schedule has been developed to bond magnesium to aluminum alloys.ProCAST software was used to optimize the process parameters during the overcasting process which lead to Mg/Al bimetallic structures to be successfully produced without formation of Mg-Al intermetallic phases.Detailed microstructure evolution during annealing,including the formation and growth of Al-Mg interdiffusion layer and intermetallic phases(Al12Mg17 and Al3Mg2),was experimentally observed for the first time with direct evidence,and predicted using Calculation of Phase Diagrams(CALPHAD)modeling.Maximum interfacial strength was achieved when the interdiffusion layer formed at the Mg/Al interface reached a maximum thickness the without formation of brittle intermetallic compounds.The precise diffusion modeling of the Mg/Al interface provides an efficient way to optimize and control the interfacial microstructure of Mg/Al bimetallic structures for improved interfacial bonding.展开更多
基金Project(2022YFB3707201) supported by the National Key R&D Program of ChinaProject(U2341254) supported by the Ye Qisun Science Foundation of National Natural Science Foundation of China+1 种基金Projects(0604022GH0202143,0604022SH0201143) supported by the NPU Aoxiang Distinguished Young Scholars,ChinaProject supported by the Funding of Young Top-notch Talent of the National Ten Thousand Talent Program,China。
文摘Effects of ultrasonic bonding parameters on atomic diffusion, microstructure at the Al-Au interface, and shear strength of Al-Au ultrasonic bonding were investigated by the combining experiments and finite element (FE) simulation. The quantitative model of atomic diffusion, which is related to the ultrasonic bonding parameters, time and distance, is established to calculate the atomic diffusion of the Al-Au interface. The maximum relative error between the calculated and experimental fraction of Al atom is 7.35%, indicating high prediction accuracy of this model. During the process of ultrasonic bonding, Au8Al3 is the main intermetallic compound (IMC) at the Al-Au interface. With larger bonding forces, higher ultrasonic powers and longer bonding time, it is more difficult to remove the oxide particles from the Al-Au interface, which hinders the atomic diffusion. Therefore, the complicated stress state and the existence of oxide particles both promotes the formation of holes. The shear strength of Al-Au ultrasonic bonding increases with increasing bonding force, ultrasonic power and bonding time. However, combined with the presence of holes at especial parameters, the optimal ultrasonic bonding parameter is confirmed to be a bonding force of 23 gf, ultrasonic power of 75 mW and bonding time of 21 ms.
基金The Special Project of the Ministry of Construction ofChina (No.20060909).
文摘In order to establish the relationship between the measured dynamic response and the health status of long-span bridges, a double-layer model updating method for steel-concrete composite beam cable-stayed bridges is proposed. Measured frequencies are selected as the first-layer reference data, and the mass of the bridge deck, the grid density, the modulus of concrete and the ballast on the side span are modified by using a manual tuning technique. Measured global positioning system （GPS） data is selected as the second-layer reference data, and the degradation of the integral structure stiffness EI of the whole bridge is taken into account for the second-layer model updating by using the finite element iteration algorithm. The Nanpu Bridge in Shanghai is taken as a case to verify the applicability of the proposed model updating method. After the first-layer model updating, the standard deviation of modal frequencies is smaller than 7%. After the second-layer model updating, the error of the deflection of the mid-span is smaller than 10%. The integral structure stiffness of the whole bridge decreases about 20%. The research results show a good agreement between the calculated response and the measured response.
文摘This article introduces an element diffusion behavior model for a titanium/steel explosive clad plate characterized by a typical curved interface during the heat-treatment process. A series of heat-treatment experiments were conducted in the temperature range from 750℃ to 950℃, and the effects of heat-treatment parameters on the microstructural evolution and diffusion behavior were investigated by optical microscopy, scanning electron microscopy, X-ray diffraction analysis, and electron-probe microanalysis. Carbon atoms within the steel matrix were observed to diffuse toward the titanium matrix and to aggregate at the bonding interface at 850℃ or lower; in contrast, when the temperature exceeded 850℃, the mutual diffusion of Ti and Fe occurred, along with the diffusion of C atoms, resulting in the for- marion of Ti-Fe intermetallics （Fe2Ti/FeTi）. The diffusion distances of C, Ti, and Fe atoms increased with increasing heating temperature and/or holding time. On the basis of this diffusion behavior, a novel diffusion model was proposed. This model considers the effects of various factors, including the curvature radius of the curved interface, the diffusion coefficient, the heating temperature, and the holding rime. The experimental results show good agreement with the calculated values. The proposed model could clearly provide a general prediction of the elements＇ diffusion at both straight and curved interfaces.
基金supported by the National Key R&D Program of China(No.:2018YFA0707300)National Natural Science Foundation of China(No.:51905372)+1 种基金Major Program of National Natural Science Foundation of China(No.:U1710254)Fundamental Research Program of Shanxi Province(No.:20210302124115).
文摘This review presents a thorough survey of the roll bonding process with a focus on the bimetallic bars/tubes as well as the bonding models and criteria.The review aims to provide insight into cold,hot and cryogenic bonding mechanisms at the micro and atomic scale and act as a guide for researchers working on roll bonding,other joining processes and bonding simulation.Mean-while,the shortcomings of roll bonding processes are presented from the aspect of formable shapes,while bonding models are shown from the aspect of calculation time,convergence,interface behav-ior of dissimilar materials as well as hot bonding status prediction.Two well-accepted numerical methodologies of bonding models,namely the contact algorithm and cohesive zone model(CZM)of bonding models and in simulations of the bonding process are highlighted.Particularly,recent advances and trends in the application of the combination of mechanical interlocking and metallurgical bonding,special energy fields,gradient structure,novel materials,green technology and soft computing method in the roll bonding process are also discussed.The challenges for advancing and prospects of the roll bonding process and bonding model are presented in an attempt to shed some light on the future research direction.
文摘Based on current theories of diffusion and creep cavity closure at high temperature, a theoretical analysis of phase transformation diffusion bonding for T8/T8 eutectoid steel is carried out. The diffusion bonding is mainly described as two-stage process: Ⅰ The interfacial cavity with shape change from diamond to cylinder.Ⅱ The radius of the cylindrical cavity are reduced and eliminated gradually. A new theoretical model is established for the process of transformation superplastic diffusion bonding (TSDB) on the basis of a theoretical model for isothermal superplastic diffusion. The model can predict the bonding quality which is affected by technological parameters, such as limit cycling temperature, the compressive stress, the numbers of thermal cycles and temperature cycling through the phase transformation in the thermal cycling and so on. Results show that the maximum temperature, the compressive stress, the numbers of thermal cycles and the rate of temperature changing speed in the thermal cycling have an important influence on TSDB process. Meanwhile, reasonable technological parameters chosen from theoretical analysis is in good agreement with those obtained from experimental results.
基金The authors are grateful for the financial supports from the National Natural Science Foundation of China(51974278)the Distinguished Young Fund of Natural Science Foundation of Hebei Province,China(E2018203446).
文摘Based on twin-roll casting, a cast-rolling force model was proposed to predict the rolling force in the bimetal solid-liquid cast-rolling bonding(SLCRB) process. The solid-liquid bonding zone was assumed to be below the kiss point(KP). The deformation resistance of the liquid zone was ignored. Then, the calculation model was derived. A 2D thermal-flow coupled simulation was established to provide a basis for the parameters in the model, and then the rolling forces of the Cu/Al clad strip at different rolling speeds were calculated. Meanwhile, through measurement experiments, the accuracy of the model was verified. The influence of the rolling speed, the substrate strip thickness, and the material on the rolling force was obtained. The results indicate that the rolling force decreases with the increase of the rolling speed and increases with the increase of the thickness and thermal conductivity of the substrate strip. The rolling force is closely related to the KP height. Therefore, the formulation of reasonable process parameters to control the KP height is of great significance to the stability of cast-rolling forming.
基金supported by grants from the Natural Science Foundation of Fujian Province(2021J011062)Minjiang Scholars Funding(GY-633Z21067).
文摘This study investigates the bond performance at the interfacial region shared by Ultra-High Performance Concrete(UHPC)and steel tubes through push-out tests.This study examines how changes in steel fiber volumetric ratio and thickness of steel tube influence the bond strength characteristics.The results show that as the enhancement of the steel tube wall thickness,the ultimate bond strength at the interface improves significantly,whereas the initial bond strength exhibits only slight variations.The influence of steel fiber volumetric ratio presents a nonlinear trend,with initial bond strength decreasing at low fiber content and increasing significantly as fiber content rises.Additionally,finite element(FE)simulations were applied to replicate the experimental conditions,and the outcomes showed strong correlation with the experimental data,confirming the exactitude of the FE model in predicting the bond behavior at the UHPC-Steel interface.These findings provide valuable insights for optimizing the design of UHPC-Filled steel tubes in high-performance structure.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11334005,11574150 and 11564006
文摘A theoretical model which couples the oscillation of cavitation bubbles with the equation of an acoustic wave is utilized to describe the sound fields in double-layer liquids, which can be used to realize the asymmetric transmission of acoustic waves. Numerical simulations show that the asymmetry is related to the properties of the host liquids and the input acoustic wave. Asymmetry can be enhanced if the maximum number density or the ambient radius of the cavitation bubbles in the low cavitation threshold liquid increases. Moreover, the direction of rectification will be reversed if the amplitude of the input acoustic wave becomes high enough.
基金supported in part by the Equipment Development Pre-research Project funded by Equipment Development Department,PRC under Grant No.50923010501Fundamental Research Program of Shenyang Institute of Automation(SIA),Chinese Academy of Sciencess under Grant No.355060201。
文摘Bonding quality at the interface of solid propellant grains is crucial for the reliability and safety of solid rocket motors.Although bonding reliability is influenced by numerous factors,the lack of quantitative characterization of interface debonding mechanisms and the challenge of identifying key factors have made precise control of process variables difficult,resulting in unpredictable failure risks.This paper presents an improved fuzzy failure probability evaluation method that combines fuzzy fault tree analysis with expert knowledge,transforming process data into fuzzy failure probability to accurately assess debonding probabilities.The predictive model is constructed through a general regression neural network and optimized using the particle swarm optimization algorithm.Sensitivity analysis is conducted to identify key decision variables,including normal force,grain rotation speed,and adhesive weight,which are verified experimentally.Compared with classical models,the maximum error margin of the constructed reliability prediction model is only 0.02%,and it has high stability.The experimental results indicate that the main factors affecting debonding are processing roughness and coating uniformity.Controlling the key decision variable as the median resulted in a maximum increase of 200.7%in bonding strength.The feasibility of the improved method has been verified,confirming that identifying key decision variables has the ability to improve bonding reliability.The proposed method simplifies the evaluation of propellant interface bonding reliability under complex conditions by quantifying the relationship between process parameters and failure risk,enabling targeted management of key decision variables.
基金financially supported by the National Key Research and Development Program of China(No.2023YFD2200505)the National Natural Science Foundation of China(No.22202105)+3 种基金the Natural Science Foundation of Jiangsu Higher Education Institutions of China(No.21KJA150003)the Innovation and Entrepreneurship Team Program of Jiangsu Province(No.JSSCTD202345)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX23_1163)the China Postdoctoral Science Foundation(Nos.2023M731703 and 2024T170415)
文摘The oxidation of lignin model compounds to esters via C-C bond cleavage has attracted considerable attention,as esters could be used as important polymer precursors and pharmaceutical intermediates.However,most studies focus on designing homogeneous or noble metal catalysts and conducting the reactions under basic conditions.Here,we report an efficient process for the C-C bond cleavage of lignin model compounds and selectively producing esters over different shaped CeO_(2)(i.e.,nanospheres(S),nanorods(R),nanoparticles(P),and nanocubes(C))under base-free conditions.Specifically,the yield of methyl anisate from the aerobic oxidation of l-(4-methoxyphenyl)ethanol reaches 77.6%over CeO_(2)-S in one hour(91%in 9 h),exhibiting higher performance compared to other evaluated CeO_(2)catalysts(6.4%-40.2%).Extensivecharacterizations and experimental investigations reveal that the density of weak base sites and oxygen vacancies on the CeO_(2)surface is positively correlated with the yield of methyl esters.Furthermore,the reaction pathway is investigated,which confirms that 1-(4-methoxyphenyl)ethanol first undergoes two reactions(i.e.,etherification and dehydrogenation)to produce intermediates of1-methoxy-4-(1-methoxy-ethyl)-benzene and 1-(4-methoxyphenyl)ethanone,respectively,followed by a series of functional group transformations to generate the targeted methyl anisate ultimately.
基金supported by NKRDPC-2022YFA1402802,NSFC-92165204the Research Grants Council of the HKSAR under Grant Nos.12304020 and 12301723+2 种基金Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices under Grant No.2022B1212010008Guangdong Fundamental Research Center for Magnetoelectric Physics under Grant No.2024B0303390001Guangdong Provincial Quantum Science Strategic Initiative under Grant No.GDZX2401010。
文摘Systems with quenched disorder possess complex energy landscapes that are challenging to explore under conventional Monte Carlo methods.In this work,we implement an efficient entropy sampling scheme for accurate computation of the entropy function in low-energy regions.The method is applied to the two-dimensional±J random-bond Ising model,where frustration is controlled by the fraction p of ferromagnetic bonds.We investigate the low-temperature paramagnetic–ferromagnetic phase boundary below the multicritical point at T_(N)=0.9530(4),P_(N)=0.89078(8),as well as the zerotemperature ferromagnetic–spin-glass transition.Finite-size scaling analysis reveals that the phase boundary for T<T_(N) exhibits reentrant behavior.By analyzing the evolution of the magnetizationresolved density of states g(E,M)and ground-state spin configurations against increasing frustration,we provide strong evidence that the zero-temperature transition is a mixed-order.Finite-size scaling conducted on the spin-glass side supports the validity of β=0,whereβis the magnetization exponent,with a correlation length exponentν=1.50(8).Our results provide new insights into the nature of the ferromagnetic-to-spin-glass phase transition in an extensively degenerate ground state.
文摘Virtual organization is a new production patter and a principal part in advanced manufacturing systems such as agile manufacturing. Manufacturability evaluation is the necessary condition to form the virtual organization. A new manufacturability evaluation approach is described in this paper, which is carried out based on every process feature under the double-layer model of manufacturing resources proposed by authors. The manufacturing resources that build up the virtual organization are selected according to the results of manufacturability evaluation.
基金supported by the National Natural Science Foundation of China(50778013)the National Basic Research Program of China(973 Program)(2010CB732100)Beijing Municipal Natural Science Foundation(8082020).
文摘The natural clayey soils are usually structural and unsaturated,which makes their mechanical properties quite different from the remolded saturated soils.A structural constitutive model is proposed to simulate the bonding-breakage micro-mechanism.In this model,the unsaturated soil element is divided into a cementation element and a friction element according to the binary medium theory,and the stress-strain coordination for these two elements is obtained. The cementation element is regarded as elastic,whereas the friction element is regarded as elastoplastic which can be described with the Gallipoli＇s model.The theoretical formulation is verified with the comparative experiments of isotropic compressions on the saturated and unsaturated structural soils.Parametric analyses of the effects of damage variables on the model predictions are further carried out,which show that breakage deformation of natural clayey soils increases with the rising amount of initial defects.
文摘The particulate discrete element method(DEM) can be employed to capture the response of rock,provided that appropriate bonding models are used to cement the particles to each other.Simulations of laboratory tests are important to establish the extent to which those models can capture realistic rock behaviors.Hitherto the focus in such comparison studies has either been on homogeneous specimens or use of two-dimensional(2D) models.In situ rock formations are often heterogeneous,thus exploring the ability of this type of models to capture heterogeneous material behavior is important to facilitate their use in design analysis.In situ stress states are basically three-dimensional(3D),and therefore it is important to develop 3D models for this purpose.This paper revisits an earlier experimental study on heterogeneous specimens,of which the relative proportions of weaker material(siltstone) and stronger,harder material(sandstone) were varied in a controlled manner.Using a 3D DEM model with the parallel bond model,virtual heterogeneous specimens were created.The overall responses in terms of variations in strength and stiffness with different percentages of weaker material(siltstone) were shown to agree with the experimental observations.There was also a good qualitative agreement in the failure patterns observed in the experiments and the simulations,suggesting that the DEM data enabled analysis of the initiation of localizations and micro fractures in the specimens.
基金Project supported by the National Basic Research Program of China (973 Project) (No. 2002CB412704).
文摘Only two macroscopic parameters are needed to describe the mechanical properties of linear elastic solids, i.e. the Poisson＇s ratio and Young＇s modulus. Correspondingly, there should be two microscopic parameters to determine the mechanical properties of material if the macroscopic mechanical properties of linear elastic solids are derived from the microscopic level. Enlightened by this idea, a multiscale mechanical model for material, the virtual multi-dimensional internal bonds （VMIB） model, is proposed by incorporating a shear bond into the virtual internal bond （VIB） model. By this modification, the VMIB model associates the macro mechanical properties of material with the microscopic mechanical properties of discrete structure and the corresponding relationship between micro and macro parameters is derived. The tensor quality of the energy density function, which contains coordinate vector, is mathematically proved. From the point of view of VMIB, the macroscopic nonlinear behaviors of material could be attributed to the evolution of virtual bond distribution density induced by the imposed deformation. With this theoretical hypothesis, as an application example, a uniaxial compressive failure of brittle material is simulated. Good agreement between the experimental results and the simulated ones is found.
基金supported by the National Natural Science Foundation (No. 51075019)Aeronautical Science Foundation of China (No. 20095251024)
文摘This paper seeks to outline a novel three-layer model and a new birth-dteath element solution technique to evaluate static strength of notched metallic panel repaired with bonded com- posite patch and to optimize material parameters. The higher order 3D, 8-node isotropic solid ele- ment and 8-node anisotropic layered solid element with three degrees of freedom per node are respectively implemented to model substrate panel, adhesive layer and composite patch to establish three-layer model of repaired panel. The new solving technique based on birth-death element is developed to allow solution of the stress pattern of repaired panel for identifying failure mode. The new model and its solution are used to model failure mode and residual strength of repaired panel, and the obtained results have a good agreement with the experimental findings. Finally, the influences of material parameter of adhesive layer and composite patch on the residual strength of repaired panel are investigated for optimizing material properties to meet operational and envi- ronmental constraints.
基金Project supported by the Education Bureau Key Natural Science Foundation of Jiangsu Province （Grant No 03KJA140117） and by the 0pen Foundation of Jiangsu Key Laboratory of Thin Film （Grant No K2022）.
文摘This paper studies the critical behaviours and magnetic properties of three-dimensional bond and anisotropy dilution Blume-Capel model （BCM） in the presence of an applied field within the effective field theory. The trajectory of tricritical point, reentrant transitions and degenerate patterns of anisotropy are obtained both for the bond and the anisotropy dilutions. The global phase diagrams demonstrate unusually reentrant phenomena. The temperature dependences of magnetization curves undergo remarkable spin glass behaviour at low temperatures, and transform from ferromagnetism to paramagnetism at high temperature in applied fields. Temperature dependence of magnetic susceptibility curve is in qualitative agreement with experimental result.
文摘The velocity structures of flow through vertically double-layered vegetation(VDLV)as well as single-layered rigid vegetation(SLV)were investigated computationally with a three-dimensional(3D)Reynolds stress turbulence model,using the computational fluid dynamics(CFD)code FLUENT.The detailed velocity distribution was explored with a varying initial Froude number(Fr),with consideration of the steady subcritical flow conditions of an inland tsunami.In VDLV flows,the numerical model successfully captured the inflection point in the profiles of mean streamwise velocities in the mixing-layer region around the top of short submerged vegetation.An upward and downward movement of flow occurred at the positions located just behind the tall and short vegetation,respectively.Overall,higher streamwise velocities were observed in the upper vegetation layer due to high porosity,with Pr=98%(sparse vegetation,where Pr is the porosity),as compared to those in the lower vegetation layer,which had comparatively low porosity,with Pr=91%(dense vegetation).A rising trend of velocities was found as the flow passed through the vegetation region,followed by a clear sawtooth distribution,as compared to the regions just upstream and downstream of vegetation where the flow was almost uniform.In VDLV flows,a rising trend in the flow resistance was observed with the increase in the initial Froude number,i.e.,Fr?0.67,0.70,and 0.73.However,the flow resistance in the case of SLV was relatively very low.The numerical results also show the flow structures within the vicinity of short and tall vegetation,which are difficult to attain through experimental measurements.
基金the National Natural Science Foundation of China[grant number 51571080].
文摘In this study,an overcasting process followed by a low-temperature(200°C)annealing schedule has been developed to bond magnesium to aluminum alloys.ProCAST software was used to optimize the process parameters during the overcasting process which lead to Mg/Al bimetallic structures to be successfully produced without formation of Mg-Al intermetallic phases.Detailed microstructure evolution during annealing,including the formation and growth of Al-Mg interdiffusion layer and intermetallic phases(Al12Mg17 and Al3Mg2),was experimentally observed for the first time with direct evidence,and predicted using Calculation of Phase Diagrams(CALPHAD)modeling.Maximum interfacial strength was achieved when the interdiffusion layer formed at the Mg/Al interface reached a maximum thickness the without formation of brittle intermetallic compounds.The precise diffusion modeling of the Mg/Al interface provides an efficient way to optimize and control the interfacial microstructure of Mg/Al bimetallic structures for improved interfacial bonding.
