In this manuscript,we propose an analytical equivalent linear viscoelastic constitutive model for fiber-reinforced composites,bypassing general computational homogenization.The method is based on the reduced-order hom...In this manuscript,we propose an analytical equivalent linear viscoelastic constitutive model for fiber-reinforced composites,bypassing general computational homogenization.The method is based on the reduced-order homogenization(ROH)approach.The ROH method typically involves solving multiple finite element problems under periodic conditions to evaluate elastic strain and eigenstrain influence functions in an‘off-line’stage,which offers substantial cost savings compared to direct computational homogenization methods.Due to the unique structure of the fibrous unit cell,“off-line”stage calculation can be eliminated by influence functions obtained analytically.Introducing the standard solid model to the ROH method enables the creation of a comprehensive analytical homogeneous viscoelastic constitutive model.This method treats fibrous composite materials as homogeneous,anisotropic viscoelastic materials,significantly reducing computational time due to its analytical nature.This approach also enables precise determination of a homogenized anisotropic relaxation modulus and accurate capture of various viscoelastic responses under different loading conditions.Three sets of numerical examples,including unit cell tests,three-point beam bending tests,and torsion tests,are given to demonstrate the predictive performance of the homogenized viscoelastic model.Furthermore,the model is validated against experimental measurements,confirming its accuracy and reliability.展开更多
Hot compression tests for GH4706 alloy were performed at a true strain of 1.2 within the temperature range of 950-1150℃ and the strain rate range of 0.001-1 s^(-1).The optimal hot deformation temperature and strain r...Hot compression tests for GH4706 alloy were performed at a true strain of 1.2 within the temperature range of 950-1150℃ and the strain rate range of 0.001-1 s^(-1).The optimal hot deformation temperature and strain rate range were determined using nephogram maps of dynamic recrystallization fraction,average grain size,and grain distribution standard deviation.Processing maps at true strains from 0.4 to 0.9 were generated based on flow stress curves to identify the strain corresponding to optimal microstructure homogenization efficiency at various temperatures and strain rates.Results show that within the optimal parameter range,under the conditions of 1150℃ and 0.01 s^(-1),the true strain of about 0.6 results in the optimal microstructure homogenization efficiency.The grain orientation spread maps obtained from the experiment also confirms this conclusion.This study provides an effective method for microstructure homogenization control of GH4706 alloy and an effective reference for the minimum strain threshold of the local part of the forging in engineering.展开更多
The microstructural evolution and composition distribution of an Al-Zn-Cu-Mg-Sc-Zr alloy during homogenization were investigated by optical microscopy（OM）,scanning electron microscopy（SEM）,energy dispersive spectr...The microstructural evolution and composition distribution of an Al-Zn-Cu-Mg-Sc-Zr alloy during homogenization were investigated by optical microscopy（OM）,scanning electron microscopy（SEM）,energy dispersive spectrometry（EDS）,X-ray diffraction（XRD） and differential scanning calorimetry（DSC）.The results show that severe dendritic segregation exists in Al-Zn-Cu-Mg-Sc-Zr alloy ingot.There are a lot of eutectic phases at grain boundary and the distribution of the main elements varies periodically along interdendritic region.The main eutectic phases at grain boundary are Al7Cu2Fe phase and T（Al2Mg3Zn3）.The residual phases are dissolved into the matrix gradually during homogenization with increasing temperature and prolonging holding time,which can be described by a constitutive equation in exponential function.The overburnt temperature of the alloy is 473.9 ℃.The optimum parameters of homogenization are 470 ℃ and 24 h,which is consistent with the result of homogenization kinetic analysis.展开更多
Based on microstructure analysis,diffusion theory,and hot deformation experiments,the solidification microstructure and element segregation of the Alloy 625 Plus ingot,the diffusion kinetics of Ti,Nb,and Mo during hom...Based on microstructure analysis,diffusion theory,and hot deformation experiments,the solidification microstructure and element segregation of the Alloy 625 Plus ingot,the diffusion kinetics of Ti,Nb,and Mo during homogenization and the hot deformation behavior of the homogenized ingot were investigated in this study.The results indicate that:(1)the solidified ingot exhibits a typical dendritic microstructure,and significant element segregation occurs,leading to the presence of Ti,Nb,and Mo-rich precipitates in the interdendritic region;(2)Following homogenization,the degree of element segregation in the ingot is significantly reduced.The diffusion coefficients(D)of Ti,Nb,and Mo under various homogenization conditions were calculated.Subsequently,the diffusion constants(D_(0))and activation energies(Q)of Ti,Nb,and Mo were obtained to be 0.01432,0.00397 and 0.00195 cm^(2)/s and 244.851,230.312,and 222.125 kJ/mol,respectively.Finally,the diffusion kinetics formulas for Ti,Nb,and Mo in Alloy 625 Plus were established.After homogenization at 1220℃for 8 h,the alloy exhibits low deformation resistance,a high degree of recrystallization,and optimal deformation coordination ability.Therefore,this represents a rational single-stage homogenization process.展开更多
The multiscale computational method with asymptotic analysis and reduced-order homogenization(ROH)gives a practical numerical solution for engineering problems,especially composite materials.Under the ROH framework,a ...The multiscale computational method with asymptotic analysis and reduced-order homogenization(ROH)gives a practical numerical solution for engineering problems,especially composite materials.Under the ROH framework,a partition-based unitcell structure at the mesoscale is utilized to give a mechanical state at the macro-scale quadrature point with pre-evaluated influence functions.In the past,the“1-phase,1-partition”rule was usually adopted in numerical analysis,where one constituent phase at the mesoscale formed one partition.The numerical cost then is significantly reduced by introducing an assumption that the mechanical responses are the same all the time at the same constituent,while it also introduces numerical inaccuracy.This study proposes a new partitioning method for fibrous unitcells under a reduced-order homogenization methodology.In this method,the fiber phase remains 1 partition,but the matrix phase is divided into 2 partitions,which refers to the“12”partitioning scheme.Analytical elastic influence+functions are derived by introducing the elastic strain energy equivalence(Hill-Mandel condition).This research also obtains the analytical eigenstrain influence functions by alleviating the so-called“inclusion-locking”phenomenon.In addition,a numerical approach to minimize the error of strain energy density is introduced to determine the partitioning of the matrix phase.Several numerical examples are presented to compare the differences among direct numerical simulation(DNS),“11”,and“12”partitioning schemes.The numerical simulations show improved++numerical accuracy by the“12”partitioning scheme.展开更多
Enhancing homogenization efficiency and hot-workability is the key issue for wrought superalloys in the industry.A novel approach for simultaneous accelerating the homogenization kinetics and improving hot-workability...Enhancing homogenization efficiency and hot-workability is the key issue for wrought superalloys in the industry.A novel approach for simultaneous accelerating the homogenization kinetics and improving hot-workability via a simple way of prior hot-deformation was proposed,which was not widely accepted for wrought superalloys.The homogenization efficiency is increased by 40%-70%via performing 10%-20%prior hot-deformation.Both theoretical and experimental analyses revealed that the increment in homogenization efficiency is mainly attributed to the decrease in interdendritic-segregation spacing,and thus the necessary diffusion distance,rather than that of dislocations.In addition,dynamic and static recrystallizations occurred during the prior hot-deformation and diffusion-annealing processes,and the grains were significantly refined even after the homogenization.Furthermore,the size of the precipitates was refined as well.These enhanced the hot-workability of the homogenized ingot for the subsequent cogging process.展开更多
This study conducts a thorough examination of honeycomb sandwich panels with a lattice core,adopting advanced computational techniques for their modeling.The research extends its analysis to investigate the natural fr...This study conducts a thorough examination of honeycomb sandwich panels with a lattice core,adopting advanced computational techniques for their modeling.The research extends its analysis to investigate the natural frequency behavior of sandwich panels,encompassing the comprehensive assessment of the entire panel structure.At its core,the research applies the Representative Volume Element(RVE)theory to establish the equivalent material properties,thereby enhancing the predictive capabilities of lattice structure simulations.Themethodology applies these properties in the core of infinite panels,which are modeled using double periodic boundary conditions to explore their natural frequencies.Expanding beyond mere material characterization,the study introduces a novel approach to defining the material within the panel cores.By incorporating alternate materials such as steel and AlSiC,and by strategically modifying their ratios,the research streamlines the process of material variation without resorting to repetitive 3D operations on the constituent cells.This optimizes not only the computational resources but also offers insights into the structural response under diverse material compositions.Furthermore,the investigation extends its scope to analyze the influence of curvature on the structural behavior of lattice structures.Panels are modeled with varying degrees of curvature,ranging from single to double curvatures,including cylindrical and spherical configurations,across a spectrum of radii.A rigorous analysis is performed to study the effect of curvature on the mechanical performance and stability of lattice structures,offering valuable insights for design optimization and structural engineering applications.By building upon the existing knowledge and introducing innovative methodologies,this study contributes to improving the understanding of lattice structures and their applicability in diverse engineering contexts.展开更多
Fish gelatin films have emerged as eco-friendly packaging materials due to their biodegradability and excellent film-forming properties.This study investigated the effects of varying homogenization rates(0,6500,9500,1...Fish gelatin films have emerged as eco-friendly packaging materials due to their biodegradability and excellent film-forming properties.This study investigated the effects of varying homogenization rates(0,6500,9500,13,500,17,500,and 21,500 rpm)on the functional and structural properties of fish gelatin films enriched with cinnamon essential oil(CEO).Homogenization reduced droplet sizes and narrowed droplet size distributions in the film-forming emulsion(FFE).At a homogenization rate of 9500 rpm,the films exhibited excellent mechan-ical extensibility,reduced surface irregularities,and enhanced smoothness.The highest(p<0.05)tensile strength and elongation at break were observed at this rate,showing increases of 57%and 14%,respectively,compared to the control film made from non-homogenized FFE.However,further increases in homogenization rates signifi-cantly increased(p<0.05)water vapor permeability and caused CEO droplets aggregation,leading to increased surface irregularities and the formation of pores in the film microstructure.These structural changes were observed through confocal laser scanning microscopy(CLSM),scanning electron microscopy(SEM),and atomic force microscopy(AFM).These findings indicate that the film properties were significantly influenced by the homogenization rate,highlighting its role in tailoring the mechanical and barrier properties of fish gelatin/CEO films for food packaging applications.展开更多
As primary load-bearing components extensively utilized in engineering applications,beam structures necessitate the design of their microstructural configurations to achieve lightweight objectives while satisfying div...As primary load-bearing components extensively utilized in engineering applications,beam structures necessitate the design of their microstructural configurations to achieve lightweight objectives while satisfying diverse mechanical performance requirements.Combining topology optimization with fully coupled homogenization beam theory,we provide a highly efficient design tool to access desirable periodic microstructures for beams.The present optimization framework comprehensively takes into account for key deformation modes,including tension,bending,torsion,and shear deformation,all within a unified formulation.Several numerical results prove that our method can be used to handle kinds of microstructure design for beam-like structures,e.g.,extreme tension(compression)-torsion stiffness,maximization of minimum critical buckling load,and minimization of structural compliance.When optimizing microstructures for macroscopic performance,we emphasize investigating the influence of shear stiffness on the optimized results.The novel chiral beam-like structures are fabricated and tested.The experimental results indicate that the optimized tension(compression)-torsion structure has excellent buffer characteristics,as compared with the traditional square tube.This proposed optimization framework can be further extended to other physical problems of Timoshenko beams.展开更多
The acuurate prediction of the time-dependent mechanical behavior and deformation mechanisms of second-phase reinforced alloys under size effects is critical for the development of high-strength ductile metals and all...The acuurate prediction of the time-dependent mechanical behavior and deformation mechanisms of second-phase reinforced alloys under size effects is critical for the development of high-strength ductile metals and alloys for dynamic applications.However,solving their responses using high-fidelity numerical methods is computationally expensive and,in many cases,impractical.To address this issue,a dual-scale incremental variational formulation is proposed that incorporates the influence of plastic gradients on plastic evolution characteristics,integrating a strain-rate-dependent strain gradient plasticity model and including plastic gradients in the inelastic dissipation potential.Subsequently,two minimization problems based on the energy dissipation mechanisms of strain gradient plasticity,corresponding to the macroscopic and microscopic structures,are solved,leading to the development of a homogenization-based dual-scale solution algorithm.Finally,the effectiveness of the variational model and tangent algorithm is validated through a series of numerical simulations.The contributions of this work are as follows:first,it advances the theory of self-consistent computational homogenization modeling based on the energy dissipation mechanisms of plastic strain rates and their gradients,along with the development of a rigorous multi-level finite element method(FE2)solution procedure;second,the proposed algorithm provides an efficient and accurate method for evaluating the time-dependent mechanical behavior of second-phase reinforced alloys under strain gradient effects,exploring how these effects vary with the strain rate,and investigating their potential interactions.展开更多
The microstructures of a Ti−5Al−5Mo−5V−1Cr−1Fe alloy with a strain gradient from 0.1 to 1 were obtained by double-cone compression experiments.The deformation microstructures were analyzed by EBSD and TEM.The results ...The microstructures of a Ti−5Al−5Mo−5V−1Cr−1Fe alloy with a strain gradient from 0.1 to 1 were obtained by double-cone compression experiments.The deformation microstructures were analyzed by EBSD and TEM.The results show that the deformation mechanism is dynamic recovery when the strain is less than 0.42.In the strain range of 0.42−0.88,the deformation mechanism is dynamic recrystallization.When the strain exceeds 0.88,the deformation bands appear.The deformation mechanism map combined with the homogenization degree of the microstructure was constructed.The more homogeneous deformed microstructure was obtained at the strain of 0.6 and the temperature of 860°C.The dynamic recrystallization forms new grains and reduces the size difference between the grains,which improves the homogenization degree of the microstructure.展开更多
In recent years,the rapid expansion of heritage tourism within China’s ethnic minority regions has been accompanied by a significant challenge:the homogenization of cultural tourism imagery and experiences.This pheno...In recent years,the rapid expansion of heritage tourism within China’s ethnic minority regions has been accompanied by a significant challenge:the homogenization of cultural tourism imagery and experiences.This phenomenon adversely affects the sustainable development of local tourism industries.To foster the effective integration,preservation,and development of heritage tourism and ethnic cultures,this study presents a case analysis of Xijiang Qianhu Miao Village in Guizhou Province.Drawing upon field research and systematic analysis,the paper critically examines manifestations of homogenization across four key dimensions:cultural image representation,commercial operational models,experiential tourism methodologies,and the depth of cultural engagement.Based on these findings,the study proposes targeted strategies to optimize the cultural tourism experience within this specific context.展开更多
High-pressure homogenization （HPH） technology was applied as a pretreatment to disintegrate sewage sludge. The effects of homogenization pressure, homogenization cycle number, and total solid content on sludge disin...High-pressure homogenization （HPH） technology was applied as a pretreatment to disintegrate sewage sludge. The effects of homogenization pressure, homogenization cycle number, and total solid content on sludge disintegration were investigated. The sludge disintegration degree （DDCOD）, protein concentration, and polysaccharide concentration increased with the increase of homogenization pressure and homogenization cycle number, and decreased with the increase of sludge total solid （TS） content. The maximum DDCOD of 43.94% was achieved at 80 MPa with four homogenization cycles for a 9.58 g/L TS sludge sample. A HPH sludge disintegration model of DDCOD= kNaPb was established by multivariable linear regression to quantify the effects of homogenization parameters. The homogenization cycle exponent a and homogenization pressure exponent b were 0.4763 and 0.7324 respectively, showing that the effect of homogenization pressure （P） was more significant than that of homogenization cycle number （N）. The value of the rate constant k decreased with the increase of sludge total solid content. The specific energy consumption increased with the increment of sludge disintegration efficiency. Lower specific energy consumption was required for higher total solid content sludge.展开更多
Quantitative analysis was employed to establish reasonable and practical homogenization model of INCONEL718 superalloy. Metallographic method was applied to determining the incipient melting temperature. The result sh...Quantitative analysis was employed to establish reasonable and practical homogenization model of INCONEL718 superalloy. Metallographic method was applied to determining the incipient melting temperature. The result shows that the incipient melting temperature of d406 mm INCONEL718 ingot is situated between 1 170 ℃ and 1 180 ℃. In order to predict the elimination process of Laves phase in quantity, a time and temperature dependent homogenization model was proposed. Among all the elements in the as-cast microstructure, Nb and Ti are the most positive segregated elements. The diffusion coefficients of alloying elements at 1 140 ℃ were obtained by fitting the linear relationship between In δ （δ residual segregation index） and time. The calculation results of diffusion coefficients were compared with other two commercial Nb-bearing superalloys.展开更多
The microstructure evolution of Al-Cu-Li-Mn-Zr-Ti alloy during homogenization was investigated by optical microscopy （OM）, scanning electron microscopy （SEM）, energy dispersive X-ray spectrometry （EDX）, and diff...The microstructure evolution of Al-Cu-Li-Mn-Zr-Ti alloy during homogenization was investigated by optical microscopy （OM）, scanning electron microscopy （SEM）, energy dispersive X-ray spectrometry （EDX）, and differential scanning calorimeter （DSC） methods. The results show that severe dendritic segregation exists in the experimental alloy ingot. Numerous eutectic phases can be observed in the grain boundary, and the distribution of the main elements along the interdendritic region varies periodically. The main secondary phase is Al2Cu. The overburnt temperature of the alloy is 520 °C. The second phases are gradually dissolved into the matrix, and the grain boundaries become spare and thin during homogenization with increasing temperature or prolonging holding time. Homogenization can be described by a constitutive equation in exponential function. The suitable homogenization treatment for the alloy is （510 °C, 18 h）, which agrees well with the results of homogenization kinetic analysis.展开更多
The homogenization on microstructure and mechanical properties of 2A50 aluminum alloy prepared by liquid forging was investigated.Wheel hubs were produced using direct and compound loading.The results show that the mi...The homogenization on microstructure and mechanical properties of 2A50 aluminum alloy prepared by liquid forging was investigated.Wheel hubs were produced using direct and compound loading.The results show that the microstructure and mechanical properties are inhomogeneous in direct forged samples.The microstructure of the wall is coarser than that of the base,and the mechanical properties are lower and some defects are detected at the wheel corner.Using compound loading,the microstructure and mechanical properties of the wall are improved evidently.With increasing feeding amount,the microstructure and mechanical properties become more homogeneous.The defects disappear when the feeding amount is 4 mm.The forged wheel hubs could obtain fine and homogeneous microstructure with grain size of 20-30 μm,tensile strength of 355 MPa and elongation of 10% when the feeding amount is 10 mm.The microstructure and mechanical properties of liquid forged workpieces could be controlled and homogenized using compound loading.展开更多
The billets of Al-Zn-Mg-Cu-Zr and Al-Zn-Mg-Cu-Zr-0.5Er alloys were prepared by semi-continuous direct chill casting （DCC）.The effects of trace Er on microstructure of Al-Zn-Mg-Cu-Zr alloy under as-cast and homogeniz...The billets of Al-Zn-Mg-Cu-Zr and Al-Zn-Mg-Cu-Zr-0.5Er alloys were prepared by semi-continuous direct chill casting （DCC）.The effects of trace Er on microstructure of Al-Zn-Mg-Cu-Zr alloy under as-cast and homogenization conditions were studied.The results show that the grain morphology is large dendritic structure and the grain size increases obviously by the addition of 0.5% Er.Moreover,most of Er element in the alloy segregates at grain boundary during solidification,resulting in ternary Al8Cu4Er phase.After homogenization,most of the MgZn2 phase at grain boundary has dissolved back to Al matrix in the two alloys.In the Er-containing alloy,the dissolution temperature of Al8Cu4Er phase is about 575 °C.Therefore,the homogenization treatment cannot eliminate Al8Cu4Er phase validity.展开更多
The microstructural evolution of a Mg, Ag and Zn micro-alloyed Al?3.8Cu?1.28Li (mass fraction, %) alloy ingot during two-step homogenization was examined in detail by optical microscopy (OM), differential scanning cal...The microstructural evolution of a Mg, Ag and Zn micro-alloyed Al?3.8Cu?1.28Li (mass fraction, %) alloy ingot during two-step homogenization was examined in detail by optical microscopy (OM), differential scanning calorimetry (DSC), electron probe micro-analysis (EPMA) and X-ray diffraction (XRD) methods. The results show that severe dendritic segregation exists in the as-cast ingot. There are many secondary phases, includingTB(Al7Cu4Li),θ(Al2Cu),R(Al5CuLi3) andS(Al2CuMg) phases, and a small amount of (Mg+Ag+Zn)-containing and AlCuFeMn phases. The fractions of intermetallic phases decrease sharply after 2 h of second-step homogenization. By prolonging the second-step homogenization time, theTB,θ,R,S and (Mg+Ag+Zn)-containing phases completely dissolve into the matrix. The dendritic segregation is eliminated, and the homogenization kinetics can be described by a constitutive equation in exponential function. However, it seems that the AlCuFeMn phase is separated into Al7Cu2Fe and AlCuMn phases, and the size of Al7Cu2Fe phase exhibits nearly no change when the second-step homogenization time is longer than 2 h.展开更多
The effect of homogenization time on quench sensitivity of a cast 7085 aluminum alloy was investigated by means of end-quenching test, optical microscope （OM）, scanning electron microscope （SEM） and transmission e...The effect of homogenization time on quench sensitivity of a cast 7085 aluminum alloy was investigated by means of end-quenching test, optical microscope （OM）, scanning electron microscope （SEM） and transmission electron microscope （TEM）. The results show that with the increase of homogenization time from 48 h to 384 h, quench sensitivity increased slightly as the largest difference in the hardness was increased from 5.2% to 6.9% in the end-quenched and aged specimens. Prolonging homogenization had little effect on the grain structure, but improved the dissolution of soluble T phase and resulted in larger Al3Zr dispersoids with a low number density. Some small quench-induced η phase particles on Al3Zr dispersoids were observed inside grains during slow quenching, which decreased hardness after subsequent aging. The change in the character of Al3Zr dispersoids exerted slight influence on quench sensitivity.展开更多
The mechanical properties of 3104 aluminum alloy processed by different combinations of cryogenic and homogenization treatments were studied. The 3104 aluminum alloy processed by the cryogenic treatment followed by ho...The mechanical properties of 3104 aluminum alloy processed by different combinations of cryogenic and homogenization treatments were studied. The 3104 aluminum alloy processed by the cryogenic treatment followed by homogenization exhibited an enhancement in the tensile strength, yield strength, and elongation by 29%, 41%, and 11%, respectively, as compared with a sample processed by the conventional homogenization treatment. The stress-strain curve of the sample processed by the homogenization treatment exhibited the Portevin-Le Chatelier effect, whereas the sample processed by the cryogenic treatment did not. Further, the cryogenic treatment could accelerate the precipitation of secondary phase particles for the sample processed by a deep cryogenic treatment, followed by a homogenization treatment, which enhanced the dislocation pinning effect of the solvent atoms and thus improved the critical strain.展开更多
基金support by the National Key R&D Program of China(Grant No.2023YFA1008901)the National Natural Science Foundation of China(Grant Nos.11988102,12172009)is gratefully acknowledged.
文摘In this manuscript,we propose an analytical equivalent linear viscoelastic constitutive model for fiber-reinforced composites,bypassing general computational homogenization.The method is based on the reduced-order homogenization(ROH)approach.The ROH method typically involves solving multiple finite element problems under periodic conditions to evaluate elastic strain and eigenstrain influence functions in an‘off-line’stage,which offers substantial cost savings compared to direct computational homogenization methods.Due to the unique structure of the fibrous unit cell,“off-line”stage calculation can be eliminated by influence functions obtained analytically.Introducing the standard solid model to the ROH method enables the creation of a comprehensive analytical homogeneous viscoelastic constitutive model.This method treats fibrous composite materials as homogeneous,anisotropic viscoelastic materials,significantly reducing computational time due to its analytical nature.This approach also enables precise determination of a homogenized anisotropic relaxation modulus and accurate capture of various viscoelastic responses under different loading conditions.Three sets of numerical examples,including unit cell tests,three-point beam bending tests,and torsion tests,are given to demonstrate the predictive performance of the homogenized viscoelastic model.Furthermore,the model is validated against experimental measurements,confirming its accuracy and reliability.
基金National Key R&D Program Project(2022YFB3705103)。
文摘Hot compression tests for GH4706 alloy were performed at a true strain of 1.2 within the temperature range of 950-1150℃ and the strain rate range of 0.001-1 s^(-1).The optimal hot deformation temperature and strain rate range were determined using nephogram maps of dynamic recrystallization fraction,average grain size,and grain distribution standard deviation.Processing maps at true strains from 0.4 to 0.9 were generated based on flow stress curves to identify the strain corresponding to optimal microstructure homogenization efficiency at various temperatures and strain rates.Results show that within the optimal parameter range,under the conditions of 1150℃ and 0.01 s^(-1),the true strain of about 0.6 results in the optimal microstructure homogenization efficiency.The grain orientation spread maps obtained from the experiment also confirms this conclusion.This study provides an effective method for microstructure homogenization control of GH4706 alloy and an effective reference for the minimum strain threshold of the local part of the forging in engineering.
基金Project (2006AA03Z523) supported by the National High-tech Research and Development Program of China
文摘The microstructural evolution and composition distribution of an Al-Zn-Cu-Mg-Sc-Zr alloy during homogenization were investigated by optical microscopy（OM）,scanning electron microscopy（SEM）,energy dispersive spectrometry（EDS）,X-ray diffraction（XRD） and differential scanning calorimetry（DSC）.The results show that severe dendritic segregation exists in Al-Zn-Cu-Mg-Sc-Zr alloy ingot.There are a lot of eutectic phases at grain boundary and the distribution of the main elements varies periodically along interdendritic region.The main eutectic phases at grain boundary are Al7Cu2Fe phase and T（Al2Mg3Zn3）.The residual phases are dissolved into the matrix gradually during homogenization with increasing temperature and prolonging holding time,which can be described by a constitutive equation in exponential function.The overburnt temperature of the alloy is 473.9 ℃.The optimum parameters of homogenization are 470 ℃ and 24 h,which is consistent with the result of homogenization kinetic analysis.
基金Project(52174303)supported by the National Natural Science Foundation of ChinaProject(2023JH2/101700302)supported by the Joint Program of Science and Technology Plans in Liaoning Province,China。
文摘Based on microstructure analysis,diffusion theory,and hot deformation experiments,the solidification microstructure and element segregation of the Alloy 625 Plus ingot,the diffusion kinetics of Ti,Nb,and Mo during homogenization and the hot deformation behavior of the homogenized ingot were investigated in this study.The results indicate that:(1)the solidified ingot exhibits a typical dendritic microstructure,and significant element segregation occurs,leading to the presence of Ti,Nb,and Mo-rich precipitates in the interdendritic region;(2)Following homogenization,the degree of element segregation in the ingot is significantly reduced.The diffusion coefficients(D)of Ti,Nb,and Mo under various homogenization conditions were calculated.Subsequently,the diffusion constants(D_(0))and activation energies(Q)of Ti,Nb,and Mo were obtained to be 0.01432,0.00397 and 0.00195 cm^(2)/s and 244.851,230.312,and 222.125 kJ/mol,respectively.Finally,the diffusion kinetics formulas for Ti,Nb,and Mo in Alloy 625 Plus were established.After homogenization at 1220℃for 8 h,the alloy exhibits low deformation resistance,a high degree of recrystallization,and optimal deformation coordination ability.Therefore,this represents a rational single-stage homogenization process.
基金funded by the National Key R&D Program of China(Grant No.2023YFA1008901)the National Natural Science Foundation of China(Grant Nos.11988102,12172009)“The Fundamental Research Funds for the Central Universities,Peking University”.
文摘The multiscale computational method with asymptotic analysis and reduced-order homogenization(ROH)gives a practical numerical solution for engineering problems,especially composite materials.Under the ROH framework,a partition-based unitcell structure at the mesoscale is utilized to give a mechanical state at the macro-scale quadrature point with pre-evaluated influence functions.In the past,the“1-phase,1-partition”rule was usually adopted in numerical analysis,where one constituent phase at the mesoscale formed one partition.The numerical cost then is significantly reduced by introducing an assumption that the mechanical responses are the same all the time at the same constituent,while it also introduces numerical inaccuracy.This study proposes a new partitioning method for fibrous unitcells under a reduced-order homogenization methodology.In this method,the fiber phase remains 1 partition,but the matrix phase is divided into 2 partitions,which refers to the“12”partitioning scheme.Analytical elastic influence+functions are derived by introducing the elastic strain energy equivalence(Hill-Mandel condition).This research also obtains the analytical eigenstrain influence functions by alleviating the so-called“inclusion-locking”phenomenon.In addition,a numerical approach to minimize the error of strain energy density is introduced to determine the partitioning of the matrix phase.Several numerical examples are presented to compare the differences among direct numerical simulation(DNS),“11”,and“12”partitioning schemes.The numerical simulations show improved++numerical accuracy by the“12”partitioning scheme.
基金supported by the National Natural Science Foundation of China(No.51804232)Beijing Municipal Natural Science Foundation(No.2212041)+1 种基金supported by the Interdisciplinary Research Project for Young Teachers of USTB(Fundamental Research Funds for the Central Universities)(FRF-IDRY-20-020)GIMRT Program of the Institute for Materials Research,Tohoku University(202303-RDKGE-0518).
文摘Enhancing homogenization efficiency and hot-workability is the key issue for wrought superalloys in the industry.A novel approach for simultaneous accelerating the homogenization kinetics and improving hot-workability via a simple way of prior hot-deformation was proposed,which was not widely accepted for wrought superalloys.The homogenization efficiency is increased by 40%-70%via performing 10%-20%prior hot-deformation.Both theoretical and experimental analyses revealed that the increment in homogenization efficiency is mainly attributed to the decrease in interdendritic-segregation spacing,and thus the necessary diffusion distance,rather than that of dislocations.In addition,dynamic and static recrystallizations occurred during the prior hot-deformation and diffusion-annealing processes,and the grains were significantly refined even after the homogenization.Furthermore,the size of the precipitates was refined as well.These enhanced the hot-workability of the homogenized ingot for the subsequent cogging process.
文摘This study conducts a thorough examination of honeycomb sandwich panels with a lattice core,adopting advanced computational techniques for their modeling.The research extends its analysis to investigate the natural frequency behavior of sandwich panels,encompassing the comprehensive assessment of the entire panel structure.At its core,the research applies the Representative Volume Element(RVE)theory to establish the equivalent material properties,thereby enhancing the predictive capabilities of lattice structure simulations.Themethodology applies these properties in the core of infinite panels,which are modeled using double periodic boundary conditions to explore their natural frequencies.Expanding beyond mere material characterization,the study introduces a novel approach to defining the material within the panel cores.By incorporating alternate materials such as steel and AlSiC,and by strategically modifying their ratios,the research streamlines the process of material variation without resorting to repetitive 3D operations on the constituent cells.This optimizes not only the computational resources but also offers insights into the structural response under diverse material compositions.Furthermore,the investigation extends its scope to analyze the influence of curvature on the structural behavior of lattice structures.Panels are modeled with varying degrees of curvature,ranging from single to double curvatures,including cylindrical and spherical configurations,across a spectrum of radii.A rigorous analysis is performed to study the effect of curvature on the mechanical performance and stability of lattice structures,offering valuable insights for design optimization and structural engineering applications.By building upon the existing knowledge and introducing innovative methodologies,this study contributes to improving the understanding of lattice structures and their applicability in diverse engineering contexts.
文摘Fish gelatin films have emerged as eco-friendly packaging materials due to their biodegradability and excellent film-forming properties.This study investigated the effects of varying homogenization rates(0,6500,9500,13,500,17,500,and 21,500 rpm)on the functional and structural properties of fish gelatin films enriched with cinnamon essential oil(CEO).Homogenization reduced droplet sizes and narrowed droplet size distributions in the film-forming emulsion(FFE).At a homogenization rate of 9500 rpm,the films exhibited excellent mechan-ical extensibility,reduced surface irregularities,and enhanced smoothness.The highest(p<0.05)tensile strength and elongation at break were observed at this rate,showing increases of 57%and 14%,respectively,compared to the control film made from non-homogenized FFE.However,further increases in homogenization rates signifi-cantly increased(p<0.05)water vapor permeability and caused CEO droplets aggregation,leading to increased surface irregularities and the formation of pores in the film microstructure.These structural changes were observed through confocal laser scanning microscopy(CLSM),scanning electron microscopy(SEM),and atomic force microscopy(AFM).These findings indicate that the film properties were significantly influenced by the homogenization rate,highlighting its role in tailoring the mechanical and barrier properties of fish gelatin/CEO films for food packaging applications.
基金supported by the National Natural Science Foundation of China(grant number 11902015)the Open Fund of Deceleration and Landing Laboratory of the Fifth Academy of Aerospace Science and Technology Group(grant number EDL19092138)the Ministry of Education Chunhui Plan(HZKY20220014).
文摘As primary load-bearing components extensively utilized in engineering applications,beam structures necessitate the design of their microstructural configurations to achieve lightweight objectives while satisfying diverse mechanical performance requirements.Combining topology optimization with fully coupled homogenization beam theory,we provide a highly efficient design tool to access desirable periodic microstructures for beams.The present optimization framework comprehensively takes into account for key deformation modes,including tension,bending,torsion,and shear deformation,all within a unified formulation.Several numerical results prove that our method can be used to handle kinds of microstructure design for beam-like structures,e.g.,extreme tension(compression)-torsion stiffness,maximization of minimum critical buckling load,and minimization of structural compliance.When optimizing microstructures for macroscopic performance,we emphasize investigating the influence of shear stiffness on the optimized results.The novel chiral beam-like structures are fabricated and tested.The experimental results indicate that the optimized tension(compression)-torsion structure has excellent buffer characteristics,as compared with the traditional square tube.This proposed optimization framework can be further extended to other physical problems of Timoshenko beams.
基金Project supported by the National Natural Science Foundation of China(Nos.11922206,11702089,12272132)the Postgraduate Scientific Research Innovation Project of Hunan Province(No.CX20240388)。
文摘The acuurate prediction of the time-dependent mechanical behavior and deformation mechanisms of second-phase reinforced alloys under size effects is critical for the development of high-strength ductile metals and alloys for dynamic applications.However,solving their responses using high-fidelity numerical methods is computationally expensive and,in many cases,impractical.To address this issue,a dual-scale incremental variational formulation is proposed that incorporates the influence of plastic gradients on plastic evolution characteristics,integrating a strain-rate-dependent strain gradient plasticity model and including plastic gradients in the inelastic dissipation potential.Subsequently,two minimization problems based on the energy dissipation mechanisms of strain gradient plasticity,corresponding to the macroscopic and microscopic structures,are solved,leading to the development of a homogenization-based dual-scale solution algorithm.Finally,the effectiveness of the variational model and tangent algorithm is validated through a series of numerical simulations.The contributions of this work are as follows:first,it advances the theory of self-consistent computational homogenization modeling based on the energy dissipation mechanisms of plastic strain rates and their gradients,along with the development of a rigorous multi-level finite element method(FE2)solution procedure;second,the proposed algorithm provides an efficient and accurate method for evaluating the time-dependent mechanical behavior of second-phase reinforced alloys under strain gradient effects,exploring how these effects vary with the strain rate,and investigating their potential interactions.
基金supported by the National Natural Science Foundation of China(Nos.52441410,52020105013)the State Key Laboratory for Powder Metallurgy,China(No.2022)。
文摘The microstructures of a Ti−5Al−5Mo−5V−1Cr−1Fe alloy with a strain gradient from 0.1 to 1 were obtained by double-cone compression experiments.The deformation microstructures were analyzed by EBSD and TEM.The results show that the deformation mechanism is dynamic recovery when the strain is less than 0.42.In the strain range of 0.42−0.88,the deformation mechanism is dynamic recrystallization.When the strain exceeds 0.88,the deformation bands appear.The deformation mechanism map combined with the homogenization degree of the microstructure was constructed.The more homogeneous deformed microstructure was obtained at the strain of 0.6 and the temperature of 860°C.The dynamic recrystallization forms new grains and reduces the size difference between the grains,which improves the homogenization degree of the microstructure.
基金supported by Beijing Institute of Graphic Communication Research Platform Construction Project(KYCPT202501).
文摘In recent years,the rapid expansion of heritage tourism within China’s ethnic minority regions has been accompanied by a significant challenge:the homogenization of cultural tourism imagery and experiences.This phenomenon adversely affects the sustainable development of local tourism industries.To foster the effective integration,preservation,and development of heritage tourism and ethnic cultures,this study presents a case analysis of Xijiang Qianhu Miao Village in Guizhou Province.Drawing upon field research and systematic analysis,the paper critically examines manifestations of homogenization across four key dimensions:cultural image representation,commercial operational models,experiential tourism methodologies,and the depth of cultural engagement.Based on these findings,the study proposes targeted strategies to optimize the cultural tourism experience within this specific context.
基金supported by the China-Israel Joint Research Program, MOST of Chinathe National Natural Science Foundation of China (No. 51178047)the Foundation of Key Laboratory for Solid Waste Management and Environment Safety,Ministry of Education of China (No. SWMES 2010-2)
文摘High-pressure homogenization （HPH） technology was applied as a pretreatment to disintegrate sewage sludge. The effects of homogenization pressure, homogenization cycle number, and total solid content on sludge disintegration were investigated. The sludge disintegration degree （DDCOD）, protein concentration, and polysaccharide concentration increased with the increase of homogenization pressure and homogenization cycle number, and decreased with the increase of sludge total solid （TS） content. The maximum DDCOD of 43.94% was achieved at 80 MPa with four homogenization cycles for a 9.58 g/L TS sludge sample. A HPH sludge disintegration model of DDCOD= kNaPb was established by multivariable linear regression to quantify the effects of homogenization parameters. The homogenization cycle exponent a and homogenization pressure exponent b were 0.4763 and 0.7324 respectively, showing that the effect of homogenization pressure （P） was more significant than that of homogenization cycle number （N）. The value of the rate constant k decreased with the increase of sludge total solid content. The specific energy consumption increased with the increment of sludge disintegration efficiency. Lower specific energy consumption was required for higher total solid content sludge.
基金Project (08dj1400402) supported by the Major Program for the Fundamental Research of Shanghai Committee of Science and Technology,China
文摘Quantitative analysis was employed to establish reasonable and practical homogenization model of INCONEL718 superalloy. Metallographic method was applied to determining the incipient melting temperature. The result shows that the incipient melting temperature of d406 mm INCONEL718 ingot is situated between 1 170 ℃ and 1 180 ℃. In order to predict the elimination process of Laves phase in quantity, a time and temperature dependent homogenization model was proposed. Among all the elements in the as-cast microstructure, Nb and Ti are the most positive segregated elements. The diffusion coefficients of alloying elements at 1 140 ℃ were obtained by fitting the linear relationship between In δ （δ residual segregation index） and time. The calculation results of diffusion coefficients were compared with other two commercial Nb-bearing superalloys.
文摘The microstructure evolution of Al-Cu-Li-Mn-Zr-Ti alloy during homogenization was investigated by optical microscopy （OM）, scanning electron microscopy （SEM）, energy dispersive X-ray spectrometry （EDX）, and differential scanning calorimeter （DSC） methods. The results show that severe dendritic segregation exists in the experimental alloy ingot. Numerous eutectic phases can be observed in the grain boundary, and the distribution of the main elements along the interdendritic region varies periodically. The main secondary phase is Al2Cu. The overburnt temperature of the alloy is 520 °C. The second phases are gradually dissolved into the matrix, and the grain boundaries become spare and thin during homogenization with increasing temperature or prolonging holding time. Homogenization can be described by a constitutive equation in exponential function. The suitable homogenization treatment for the alloy is （510 °C, 18 h）, which agrees well with the results of homogenization kinetic analysis.
基金Projects (50774026, 50875059) supported by the National Natural Science Foundation of ChinaProject (20070420023) supported by the China Postdoctoral Science FoundationProject (2008AA03A239) supported by the National High-tech Research and Development Program of China
文摘The homogenization on microstructure and mechanical properties of 2A50 aluminum alloy prepared by liquid forging was investigated.Wheel hubs were produced using direct and compound loading.The results show that the microstructure and mechanical properties are inhomogeneous in direct forged samples.The microstructure of the wall is coarser than that of the base,and the mechanical properties are lower and some defects are detected at the wheel corner.Using compound loading,the microstructure and mechanical properties of the wall are improved evidently.With increasing feeding amount,the microstructure and mechanical properties become more homogeneous.The defects disappear when the feeding amount is 4 mm.The forged wheel hubs could obtain fine and homogeneous microstructure with grain size of 20-30 μm,tensile strength of 355 MPa and elongation of 10% when the feeding amount is 10 mm.The microstructure and mechanical properties of liquid forged workpieces could be controlled and homogenized using compound loading.
基金Project(50875031) supported by the National Natural Science Foundation of ChinaProject(2005CB623705) supported by National Basic Research Program of China
文摘The billets of Al-Zn-Mg-Cu-Zr and Al-Zn-Mg-Cu-Zr-0.5Er alloys were prepared by semi-continuous direct chill casting （DCC）.The effects of trace Er on microstructure of Al-Zn-Mg-Cu-Zr alloy under as-cast and homogenization conditions were studied.The results show that the grain morphology is large dendritic structure and the grain size increases obviously by the addition of 0.5% Er.Moreover,most of Er element in the alloy segregates at grain boundary during solidification,resulting in ternary Al8Cu4Er phase.After homogenization,most of the MgZn2 phase at grain boundary has dissolved back to Al matrix in the two alloys.In the Er-containing alloy,the dissolution temperature of Al8Cu4Er phase is about 575 °C.Therefore,the homogenization treatment cannot eliminate Al8Cu4Er phase validity.
基金Project(2013JSJJ0001)supported by Teachers’Research Found,ChinaProject(2013AA032401)supported by the National High Technology Research and Development Program of ChinaProject supported by the Nonferrous Metal Oriented Advanced Structural Materials and Manufacturing Cooperative Innovation Center,China
文摘The microstructural evolution of a Mg, Ag and Zn micro-alloyed Al?3.8Cu?1.28Li (mass fraction, %) alloy ingot during two-step homogenization was examined in detail by optical microscopy (OM), differential scanning calorimetry (DSC), electron probe micro-analysis (EPMA) and X-ray diffraction (XRD) methods. The results show that severe dendritic segregation exists in the as-cast ingot. There are many secondary phases, includingTB(Al7Cu4Li),θ(Al2Cu),R(Al5CuLi3) andS(Al2CuMg) phases, and a small amount of (Mg+Ag+Zn)-containing and AlCuFeMn phases. The fractions of intermetallic phases decrease sharply after 2 h of second-step homogenization. By prolonging the second-step homogenization time, theTB,θ,R,S and (Mg+Ag+Zn)-containing phases completely dissolve into the matrix. The dendritic segregation is eliminated, and the homogenization kinetics can be described by a constitutive equation in exponential function. However, it seems that the AlCuFeMn phase is separated into Al7Cu2Fe and AlCuMn phases, and the size of Al7Cu2Fe phase exhibits nearly no change when the second-step homogenization time is longer than 2 h.
基金Project(2012CB619500)supported by the National Basic Research Program of ChinaProject supported by Yuying Project of Central South University
文摘The effect of homogenization time on quench sensitivity of a cast 7085 aluminum alloy was investigated by means of end-quenching test, optical microscope （OM）, scanning electron microscope （SEM） and transmission electron microscope （TEM）. The results show that with the increase of homogenization time from 48 h to 384 h, quench sensitivity increased slightly as the largest difference in the hardness was increased from 5.2% to 6.9% in the end-quenched and aged specimens. Prolonging homogenization had little effect on the grain structure, but improved the dissolution of soluble T phase and resulted in larger Al3Zr dispersoids with a low number density. Some small quench-induced η phase particles on Al3Zr dispersoids were observed inside grains during slow quenching, which decreased hardness after subsequent aging. The change in the character of Al3Zr dispersoids exerted slight influence on quench sensitivity.
基金Project(2011BAC10B02)supported by the National Key Technology R&D Program of China
文摘The mechanical properties of 3104 aluminum alloy processed by different combinations of cryogenic and homogenization treatments were studied. The 3104 aluminum alloy processed by the cryogenic treatment followed by homogenization exhibited an enhancement in the tensile strength, yield strength, and elongation by 29%, 41%, and 11%, respectively, as compared with a sample processed by the conventional homogenization treatment. The stress-strain curve of the sample processed by the homogenization treatment exhibited the Portevin-Le Chatelier effect, whereas the sample processed by the cryogenic treatment did not. Further, the cryogenic treatment could accelerate the precipitation of secondary phase particles for the sample processed by a deep cryogenic treatment, followed by a homogenization treatment, which enhanced the dislocation pinning effect of the solvent atoms and thus improved the critical strain.
