As binary geological media,soil-rock mixtures(SRMs)exhibit a distinct gradational composition,leading to their unique mechanical behaviors.To appraise the stability of SRM slopes,it is essential to determine equivalen...As binary geological media,soil-rock mixtures(SRMs)exhibit a distinct gradational composition,leading to their unique mechanical behaviors.To appraise the stability of SRM slopes,it is essential to determine equivalent parameters of SRMs,which are typically obtained through experimental and numerical methods.In contrasted to other numerical methods,the numerical manifold method(NMM)is more effective in addressing SRM problems.This is because the high-precision regular mathematical meshes in NMM can be used without aligning with the soil-rock interfaces and boundaries of SRMs.In the current research,the equivalent strength parameters of SRMs,i.e.the equivalent cohesion ce and internal friction angleϕ_(e),are determined using NMM.Initially,an NMM triaxial numerical model is established and validated based on triaxial experiments.Subsequently,the soil and rock parameters are derived through parameter inversion.Moreover,the impacts of rock content,size,shape and rock blocks'major-axis orientation on ce andϕ_(e) of SRMs are thoroughly examined using the NMM triaxial numerical model.Additionally,a fitting function is proposed to linkϕ_(e) to the rock content and size of SRMs.When other influencing factors are fixed,the above fitting model leads to the following conclusions:(1)the predictedϕ_(e) of SRMs increase with the increase of rock content;and(2)SRM samples with smaller rocks display a higher predictedϕ_(e).展开更多
Texture and grain structure evolution during annealing and their effects on tensile strength and anisotropy were studied using XRD,DSC,SEM,EBSD and TEM.The results indicate that elevated rolling temperatures reduce th...Texture and grain structure evolution during annealing and their effects on tensile strength and anisotropy were studied using XRD,DSC,SEM,EBSD and TEM.The results indicate that elevated rolling temperatures reduce the f(g)_(max(Copper))/f(g)_(max(Brass))ratio,increase S-Brass fine bands,and promote S-dispersoid precipitation,leading to finer recrystallized grains.Dominant recrystallization textures transform from Goss+P to Goss and then to Goss+Cube with increasing rolling temperature.Annealing at 350℃shows four tensile strength response stages:fast softening I,rapid strengthening II,slow strengthening III,and slow softening IV.The transition from Stages I to II is driven by the formation of strong Goss and P textures,and Stage IV is linked to enhanced Cube texture.Plates with Goss+Cube textures and fine equiaxed grains exhibit the lowest YS/UTS ratio and minimal anisotropy.展开更多
This study investigates the influences of brazing temperature, brazing time and braz- ing clearance on microstructures and high temperature strength of Inconel superalloy. Bonding is performed in a high vacuum furnace...This study investigates the influences of brazing temperature, brazing time and braz- ing clearance on microstructures and high temperature strength of Inconel superalloy. Bonding is performed in a high vacuum furnace using BNi-2 as filler metal. Brazing temperatures employed in this study are 1080 ℃, 1110 ℃ and 1140 ℃. Holding times at the brazing temperature are 5 min, 15 min and 45 min. At the same time, the investigated brazing clearances are 30μm, 60 μm and 100 pro. Microstructure of the brazed joints is analyzed by means of metallography, scanning electron microscope （SEM）. The high temperature tensile strength and microhardness are evaluated at different brazing parameters. The results show that fracture occurs wholly within the braze metal. Deformation appears to be confined to the braze metal with the base metal, showing very little plastic deformation. Brazing time shows to play the important role in the brazing parameters. The peak of microhardness is at the centerline of braze region. Induction heating has little effect on the base materials.展开更多
In order to research environment parameters and physiological indices of high-quality and high-yield apple trees, two orchards with young and mature apples trees were investigated to explore structural parameter of ap...In order to research environment parameters and physiological indices of high-quality and high-yield apple trees, two orchards with young and mature apples trees were investigated to explore structural parameter of apple tree and community, and some physiological indices in fields and by room measurements. The results showed that tree height of high-quality orchard was in the range of 260 to 290 cm, branch angle in 70°-75°, and orchard coverage rate in 75%-94%, and the connec-tion rates between rows and trees were lower. Furthermore, the total branches of mature orchard reached 1.04 ×106 per hm2, while the young orchard was 8.79 ×105 per hm2; the leaves were thick and chlorophyl content was high, with SPAD value at 58.22. Additional y, the photosynthesis of the orchard was strong, and net photo-synthetic rate was 17.48-21.8 μmolCO2/（m2·s）. The proportions of lateral shoot of bearing part were 81% and 75% respectively.展开更多
Modal parameters can accurately characterize the structural dynamic properties and assess the physical state of the structure.Therefore,it is particularly significant to identify the structural modal parameters accordi...Modal parameters can accurately characterize the structural dynamic properties and assess the physical state of the structure.Therefore,it is particularly significant to identify the structural modal parameters according to the monitoring data information in the structural health monitoring(SHM)system,so as to provide a scientific basis for structural damage identification and dynamic model modification.In view of this,this paper reviews methods for identifying structural modal parameters under environmental excitation and briefly describes how to identify structural damages based on the derived modal parameters.The paper primarily introduces data-driven modal parameter recognition methods(e.g.,time-domain,frequency-domain,and time-frequency-domain methods,etc.),briefly describes damage identification methods based on the variations of modal parameters(e.g.,natural frequency,modal shapes,and curvature modal shapes,etc.)and modal validation methods(e.g.,Stability Diagram and Modal Assurance Criterion,etc.).The current status of the application of artificial intelligence(AI)methods in the direction of modal parameter recognition and damage identification is further discussed.Based on the pre-vious analysis,the main development trends of structural modal parameter recognition and damage identification methods are given to provide scientific references for the optimized design and functional upgrading of SHM systems.展开更多
By using the high spatial and temporal resolution Jinan Doppler Weather Radar data and Jinan,Xingtai sounding data,the radar signature and mesocyclone parameters of 54 supercells during 2003-2008 were analyzed.The res...By using the high spatial and temporal resolution Jinan Doppler Weather Radar data and Jinan,Xingtai sounding data,the radar signature and mesocyclone parameters of 54 supercells during 2003-2008 were analyzed.The results showed that the probability of a supercell forming would be higher when SI (showalter index) ≤ -2℃,K (K index) ≥ 30℃ and 0-6 km wind shear>15 m/s.The supercell storms can generally be divided into two categories,namely,type of isolation and mosaic type.To the type of isolation,the max reflectivity,cell-based VIL,max reflectivity height,cell top,mesocyclone base and top were significantly higher than the mosaic type.Isolation-type supercells had significantly higher probability of hail,lower probability of gale than the mosaic category.The mesocyclone attribute differences between isolation-type and mosaic type supercells determined the differences of storm structures and severe weather phenomenon.展开更多
SiC/Al-based composite foams were prepared by a two-step foaming method.The influence of the SiC content and its distribution uniformity on the foaming stability,cell structure,and mechanical properties of the aluminu...SiC/Al-based composite foams were prepared by a two-step foaming method.The influence of the SiC content and its distribution uniformity on the foaming stability,cell structure,and mechanical properties of the aluminum foams was investigated.The macro/micro-features of the aluminum foams were characterized and analyzed.Results demonstrate that an appropriate increase in SiC content and the uniform distribution of SiC can improve the foaming stability,optimize the cell diameter and cell wall thickness,ameliorate the cell distribution,and enhance the hardness and compressive strength of the aluminum foams.However,either insufficient or excessive SiC leads to uneven distribution of SiC particles,which is unfavorable to foaming stability and good cell structure formation.With 6wt%SiC,both the foaming stability and cell structure of the aluminum foam reach the optimal state,resulting in the highest compressive strength and optimal energy absorption capacity.展开更多
China has set its economic growth target for 2026 in the range of 4.5-5 percent.After three consecutive years of aiming for growth of around 5 percent,the slightly adjusted range reflects a prudent assessment of a com...China has set its economic growth target for 2026 in the range of 4.5-5 percent.After three consecutive years of aiming for growth of around 5 percent,the slightly adjusted range reflects a prudent assessment of a complex global environment while still signalling a commitment to stable development.展开更多
In this study,the dynamic characteristics and microstructures of lacustrine soft clays were studied.Dynamic character tests were conducted on undisturbed,remolded,and saturated lacustrine soft clays,using a dynamic tr...In this study,the dynamic characteristics and microstructures of lacustrine soft clays were studied.Dynamic character tests were conducted on undisturbed,remolded,and saturated lacustrine soft clays,using a dynamic triaxial tester.A scanning electron microscope(SEM)was employed to assess the soil samples after dynamic testing.The results indicate that the dynamic characteristics of lacustrine soft clay were significantly affected by confining pressure and water content.A quantitative relationship was established among confining pressures,water content,and the dynamic shear modulus ratio.The dynamic characteristic parameters of undisturbed,remolded and saturated soil are obviously different,and the original structure can enhance the shear strength of soil.By comparing the results with those from other studies,we found that the dynamic characters of soft clays were considerably varied in different regions,and lacustrine soft clays had a larger dynamic shear modulus ratio and a smaller damping ratio when the dynamic shear strain was large.Using IPP software to process the microstructural images,we found that the soil was dominated by small pores and medium particles,and the roundness of pores and particles had an apparently positive correlation with the maximum diameter.Moreover,the pores and particles of the soil showed fractal characteristics and directionality,and the fractal dimensions and probability entropy were strongly correlated with the macrostructural parameters.Finally,we developed a prediction model for macrostructural and microstructural parameters.展开更多
The S38C railway axle undergoes induction hardening,resulting in a gradient-distributed microstructure and mechanical properties.The accurate identification of gradient-distributed plastic parameters for the S38C axle...The S38C railway axle undergoes induction hardening,resulting in a gradient-distributed microstructure and mechanical properties.The accurate identification of gradient-distributed plastic parameters for the S38C axle remains a challenging task.To tackle this challenge,the present study proposes a novel approach for identifying the gradient-distributed plastic parameters for the S38C axle by integrating nano-indentation techniques with the machine learning method.Firstly,nano-indentation tests are conducted along the radial direction of the S38C axle to obtain the gradient-distributed load-displacement curves,nano-hardness,and elastic modulus.Subsequently,the dimensionless analysis is performed to obtain the representative stress,strain,and yield stress from load-displacement curves.These parameters are then incorporated into the machine learning method as physical information to identify the gradient-distributed plastic parameters of the S38C axle.The results indicate that the proposed method based on the physics-informed neural network and multi-fidelity neural network successfully identifies the gradient-distributed plastic parameters of the S38C axles and demonstrates superior prediction accuracy and generalization compared with the purely data-driven machine learning method.展开更多
Water storage in the Three Gorges Reservoir in China has increased the regional microseismicity.Bedding-rock landslides,one of the most common slope structures in the Three Gorges Reservoir,are highly prone to sliding...Water storage in the Three Gorges Reservoir in China has increased the regional microseismicity.Bedding-rock landslides,one of the most common slope structures in the Three Gorges Reservoir,are highly prone to sliding under seismic loading.Existing research primarily focuses on the stability of bedding rock landslides under strong earthquakes,while studies on the cumulative damage and long-term stability of bedding rock landslides under high-frequency microseismicity remain immature.In this study,we considered bedding rock landslides under high-frequency microseismicity in the Three Gorges Reservoir area as the research subject and equivalent microseismicity as pre-peak cyclic loading.First,we analyzed the shear strength deterioration of rock mass structural planes under pre-peak cyclic loading conditions and found that the deformation and failure of structural planes involve contact and damage effects.The shear strength of the rock mass structural planes under pre-peak cyclic loading conditions is affected by the confining pressure,loading rate,loading amplitude,and number of loading cycles.Among these factors,the shear strength of the structural planes was the most sensitive to the number of loading cycles.As the number of cycles increased,the rock mass structural planes underwent three stages:stress adjustment(increase in shear strength),fatigue damage(gradual decrease in shear strength),and structural failure(rapid decrease in shear strength).The stability of bedding rock landslides under high-frequency microseismicity was analyzed,revealing that the stability of bedding rock landslides under high-frequency microseismicity can be divided into three stages:short-term enhancement,gradual degradation,and rapid deterioration,exhibiting characteristics of gradual and sudden changes.展开更多
This study investigates the thermo–mechanical behavior of C40 concrete and reinforced concrete subjected to elevated temperatures up to 700℃by integrating experimental testing and advanced numerical modeling.A tempe...This study investigates the thermo–mechanical behavior of C40 concrete and reinforced concrete subjected to elevated temperatures up to 700℃by integrating experimental testing and advanced numerical modeling.A temperature-indexed Concrete Damage Plasticity(CDP)framework incorporating bond–slip effects was developed in Abaqus to capture both global stress–strain responses and localized damage evolution.Uniaxial compression tests on thermally exposed cylinders provided residual strength data and failure observations for model calibration and validation.Results demonstrated a distinct two-stage degradation regime:moderate stiffness and strength reduction up to~400℃,followed by sharp deterioration beyond 500℃–600℃,with residual capacity at 700℃reduced to~20%–25%of the ambient value.Strain–damage analyses revealed the formation of a peripheral tensile strain band,which thickened and propagated inward with increasing temperature,governing crack initiation and cover spalling.Supplemental analyses highlighted that transverse reinforcement improved ductility and damage distribution at moderate temperatures(~300℃),but bond deterioration and steel softening beyond~600℃substantially diminished confinement effectiveness.The proposed CDP model accurately reproduced experimental stress–strain curves(R^(2)≈0.94–0.98 up to 600℃;≈0.90 at 700℃),with peak stress errors within 7%–10%and energy absorption captured within~12%.These findings confirm the robustness of the temperature-indexed CDP framework for simulating fire-damaged reinforced concrete and provide practical guidelines for post-fire assessment,spalling detection,and fire-resilient design of structural members.展开更多
With a more complex pore structure system compared with clastic rocks, carbonate rocks have not yet been well described by existing conventional rock physical models concerning the pore structure vagary as well as the...With a more complex pore structure system compared with clastic rocks, carbonate rocks have not yet been well described by existing conventional rock physical models concerning the pore structure vagary as well as the influence on elastic rock properties. We start with a discussion and an analysis about carbonate rock pore structure utilizing rock slices. Then, given appropriate assumptions, we introduce a new approach to modeling carbonate rocks and construct a pore structure algorithm to identify pore structure mutation with a basis on the Gassmann equation and the Eshelby-Walsh ellipsoid inclusion crack theory. Finally, we compute a single well＇s porosity using this new approach with full wave log data and make a comparison with the predicted result of traditional method and simultaneously invert for reservoir parameters. The study results reveal that the rock pore structure can significantly influence the rocks＇ elastic properties and the predicted porosity error of the new modeling approach is merely 0.74%. Therefore, the approach we introduce can effectively decrease the predicted error of reservoir parameters.展开更多
The trade-off between strength and ductility remains a significant challenge in titanium alloy development.Micro structural engineering is a cost-effective alternative to balance strength and ductility.In this study,t...The trade-off between strength and ductility remains a significant challenge in titanium alloy development.Micro structural engineering is a cost-effective alternative to balance strength and ductility.In this study,three micro structures were produced in low-cost titanium alloys via solution treatment,and the alloys withα,α'-martensite,andβphases exhibited an optimal strengthductility combination.The hierarchical phase structure,α'-martensite reorientation,multi-oriented nanotwins,and dislocation interactions collectively contributed to its high yield strength(~1015 MPa),ultimate tensile strength(~1307 MPa),and satisfactory ductility(~13%).Importantly,this study reveals a new pathway for nanotwin formation inα'phases and provides key insights for optimizing the mechanical properties of low-cost titanium alloys.展开更多
Compositionally-complex alloys(CCAs)with the face-centered cubic(fcc)structure exhibit excellent frac-ture toughness and stable mechanical property across a broad temperature range from cryogenic to room temperatures....Compositionally-complex alloys(CCAs)with the face-centered cubic(fcc)structure exhibit excellent frac-ture toughness and stable mechanical property across a broad temperature range from cryogenic to room temperatures.However,yield strength of those alloys is usually low,making them difficult to meet the demands of practical engineering application.In a prototype CCA with the nominal chemical composition of Co10Cr10Fe49Mn30N1(atom percent),a multi-scaled heterostructure from sample to atomic scales was obtained by performing triaxial cyclic compression and short-term annealing on the blocky alloy.The ma-terial exhibits a heterogeneous distribution of strain at the sample scale.At the grain scale,dense twins and twin-twin network,laths featured with local chemical order as well as dislocation cells jointly hinder plastic deformation.At the nanoscale,the chemical order within grains also impedes dislocation motion.During plastic deformation,different sample positions within the heterogeneous material and various regions at each position undergo coordinated deformation,resulting in significant hetero-deformation in-duced strengthening.Simultaneously,the continuously activated dislocations,stacking faults and nano-twins lead to a high yield strength of 1020 MPa in the material while maintaining a fracture elongation of 30%.This study provides new insights for the design and development of high-performance metallic materials.展开更多
Metastable β titanium alloy is an ideal material for lightweight and high strength due to its excellent comprehensive mechanical properties.However,overcoming the trade-off relation between strength and ductility rem...Metastable β titanium alloy is an ideal material for lightweight and high strength due to its excellent comprehensive mechanical properties.However,overcoming the trade-off relation between strength and ductility remains a significant challenge.In this study,the mechanical properties of Ti-38644 alloy were optimized by introducing a heterogeneous bi-grain bi-lamella(BG-BL)structure through a well-designed combination of rolling,drawing and heat treatment.The results demonstrate that the present BG-BL Ti-38644 alloy shows a tensile strength of~1500 MPa and a total elongation of 18%.In particular,the high strength-elongation combination of the BG-BL Ti-38644 alloy breakthroughs the trade-off relation in all the titanium alloys available.The recrystallized grains with low dislocation enhance the ductility of the Ti-38644 alloy,while the highly distorted elongated grains mainly contribute to the high strength.The present study provides a new principle for designing Ti alloys with superior strength and ductility.展开更多
This paper employs the Direct Finite Element Squared(DFE2)method to develop Sparse Polynomial Chaos Expansions(SPCE)models for analyzing the electromechanical properties of multiscale piezoelectric structures.By incor...This paper employs the Direct Finite Element Squared(DFE2)method to develop Sparse Polynomial Chaos Expansions(SPCE)models for analyzing the electromechanical properties of multiscale piezoelectric structures.By incorporating variations in piezoelectric and elastic constants,the DFE2 method is utilized to simulate the statistical characteristics—such as expected values and standard deviations—of electromechanical properties,including Mises stress,maximum in-plane principal strain,electric potential gradient,and electric potential,under varying parameters.This approach achieves a balance between computational efficiency and accuracy.Different SPCE models are used to investigate the influence of piezoelectric and elastic constants on multiscale piezoelectric materials.Additionally,the multiscale parameterization study investigates how microscale material properties affect the macroscopic response of these structures and materials.展开更多
Coke is the only solid charge component in the lower part of the blast furnace,and its strength is crucial to its production.Si and Al are the two most abundant elements in coke ash.The influences of these oxides on t...Coke is the only solid charge component in the lower part of the blast furnace,and its strength is crucial to its production.Si and Al are the two most abundant elements in coke ash.The influences of these oxides on the tensile strength of the coke matrix were studied by splitting tests.According to the Weibull analysis,with increasing Si and Al oxide concentrations,the fracture stress range of the coke widened,the upper and lower limits decreased,the probability of fracture under the same stress conditions increased,and the randomness and dispersion of strength increased.These results can be attributed to the inhibitory effect of ash during coal pyrolysis.Ash impedes the growth and contact of mesophase,leading to a decrease in graphitic carbon structures and an increase in edge carbon and aliphatic carbon structures in the resulting coke.Consequently,the overall ordering of the carbon structure is reduced.Moreover,SiO_(2)and Al_(2)O_(3)promoted the development of coke pores,thinned the coke pore wall,and significantly increased the proportion of large pores(>500μm).Moreover,Al_(2)O_(3)had more significant influences on the coke strength,carbon structure and stomatal ratio than SiO_(2).In addition,the position where the ash particles bonded to the carbon matrix easily produced cracks and holes,and the sharp edge of the matrix was likely to produce stress concentration points when subjected to an external force,leading to structural damage.Therefore,controlling the concentration of ash could effectively reduce the number of structural defects inside coke,which is conducive to improving the strength.展开更多
The effects of different Al_(2)O_(3)/SiO_(2)(Al/Si)ratios on the structure and tensile strength of Na_(2)O-CaO-MgO-Al_(2)O_(3)-SiO_(2)glass fiber were investigated by Raman,tensile strength tests and molecular dynamic...The effects of different Al_(2)O_(3)/SiO_(2)(Al/Si)ratios on the structure and tensile strength of Na_(2)O-CaO-MgO-Al_(2)O_(3)-SiO_(2)glass fiber were investigated by Raman,tensile strength tests and molecular dynamics simulation.The results showed that Al^(3+)mainly existed in the form of[AlO_(4)]within the glass network.With the increase of Al/Si ratio,the Si-O-Al linkage gradually became the main connection mode of glass network.The increase of bridging oxygen content and variation of Q^(n) indicated that a higher degree of network polymerization was formed.The tensile strength of the glass fibers obtained through experiments increased from 2653.56 to 2856.83 MPa,which was confirmed by the corresponding molecular dynamics simulation.During the stretching process,the Si-O bonds in the Si-O-Al linkage tended to break regardless of the compositional changes,and the increase of fractured Si-O-Al and Al-O-Al linkage absorbed more energy to resist the destroy.展开更多
The low strength of Mg-Li alloys sets a limit to lightweight applications.Introducing crystal defects(twins,dislocations,and SFs)is a distinctive strategy for maintaining good mechanical properties of metallic materia...The low strength of Mg-Li alloys sets a limit to lightweight applications.Introducing crystal defects(twins,dislocations,and SFs)is a distinctive strategy for maintaining good mechanical properties of metallic materials.A lamellar-structured Mg-4Li-3Al-0.4Ca alloy with high performance was prepared by hot extrusion and rotary swaging.The as-swaged alloy exhibits excellent mechanical properties with tensile strength,yield strength,elongation to failure,and specific strength of 391 MPa,312 MPa,14.2%,and 238.4 kN m kg^(-1),respectively.The average grain size of the as-swaged alloy is 160±23 nm,and the microstructure is mainly composed of lamellar structures,twins,ultrafine grains,and nano-grains.The abundant lamellar structures and twins promote the storage of dislocations and SFs,leading to the formation of twin-twin interactions and enhancing strain hardening.The formation of UFG and NG by dynamic recrystallization further improves the yield strength.Shearable second phases play a critical role in enhancing the yield strength and ductility.More importantly,extensive planar dislocation glide and(c+a)dislocations efficiently relax the local stress concentrations,and thus improve the ductility.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12272393 and 52130905).
文摘As binary geological media,soil-rock mixtures(SRMs)exhibit a distinct gradational composition,leading to their unique mechanical behaviors.To appraise the stability of SRM slopes,it is essential to determine equivalent parameters of SRMs,which are typically obtained through experimental and numerical methods.In contrasted to other numerical methods,the numerical manifold method(NMM)is more effective in addressing SRM problems.This is because the high-precision regular mathematical meshes in NMM can be used without aligning with the soil-rock interfaces and boundaries of SRMs.In the current research,the equivalent strength parameters of SRMs,i.e.the equivalent cohesion ce and internal friction angleϕ_(e),are determined using NMM.Initially,an NMM triaxial numerical model is established and validated based on triaxial experiments.Subsequently,the soil and rock parameters are derived through parameter inversion.Moreover,the impacts of rock content,size,shape and rock blocks'major-axis orientation on ce andϕ_(e) of SRMs are thoroughly examined using the NMM triaxial numerical model.Additionally,a fitting function is proposed to linkϕ_(e) to the rock content and size of SRMs.When other influencing factors are fixed,the above fitting model leads to the following conclusions:(1)the predictedϕ_(e) of SRMs increase with the increase of rock content;and(2)SRM samples with smaller rocks display a higher predictedϕ_(e).
基金financial support from the National Key Research and Development Program of China(No.2016YFB0300900)the National Key Fundamental Research Project of China(No.2012CB619506-3)the National Natural Science Foundation of China(No.51171209)。
文摘Texture and grain structure evolution during annealing and their effects on tensile strength and anisotropy were studied using XRD,DSC,SEM,EBSD and TEM.The results indicate that elevated rolling temperatures reduce the f(g)_(max(Copper))/f(g)_(max(Brass))ratio,increase S-Brass fine bands,and promote S-dispersoid precipitation,leading to finer recrystallized grains.Dominant recrystallization textures transform from Goss+P to Goss and then to Goss+Cube with increasing rolling temperature.Annealing at 350℃shows four tensile strength response stages:fast softening I,rapid strengthening II,slow strengthening III,and slow softening IV.The transition from Stages I to II is driven by the formation of strong Goss and P textures,and Stage IV is linked to enhanced Cube texture.Plates with Goss+Cube textures and fine equiaxed grains exhibit the lowest YS/UTS ratio and minimal anisotropy.
基金supported by the National Natural Science Foundation of China(No.50875160)Shanghai Leading Academic Discipline Project (No.J51402)Natural Science Foundation of Shanghai of China (No.10ZR1412900)
文摘This study investigates the influences of brazing temperature, brazing time and braz- ing clearance on microstructures and high temperature strength of Inconel superalloy. Bonding is performed in a high vacuum furnace using BNi-2 as filler metal. Brazing temperatures employed in this study are 1080 ℃, 1110 ℃ and 1140 ℃. Holding times at the brazing temperature are 5 min, 15 min and 45 min. At the same time, the investigated brazing clearances are 30μm, 60 μm and 100 pro. Microstructure of the brazed joints is analyzed by means of metallography, scanning electron microscope （SEM）. The high temperature tensile strength and microhardness are evaluated at different brazing parameters. The results show that fracture occurs wholly within the braze metal. Deformation appears to be confined to the braze metal with the base metal, showing very little plastic deformation. Brazing time shows to play the important role in the brazing parameters. The peak of microhardness is at the centerline of braze region. Induction heating has little effect on the base materials.
基金Supported by Special Fund for Modern Agricultural Industry Technology System(CARS-28)~~
文摘In order to research environment parameters and physiological indices of high-quality and high-yield apple trees, two orchards with young and mature apples trees were investigated to explore structural parameter of apple tree and community, and some physiological indices in fields and by room measurements. The results showed that tree height of high-quality orchard was in the range of 260 to 290 cm, branch angle in 70°-75°, and orchard coverage rate in 75%-94%, and the connec-tion rates between rows and trees were lower. Furthermore, the total branches of mature orchard reached 1.04 ×106 per hm2, while the young orchard was 8.79 ×105 per hm2; the leaves were thick and chlorophyl content was high, with SPAD value at 58.22. Additional y, the photosynthesis of the orchard was strong, and net photo-synthetic rate was 17.48-21.8 μmolCO2/（m2·s）. The proportions of lateral shoot of bearing part were 81% and 75% respectively.
基金supported by the Innovation Foundation of Provincial Education Department of Gansu(2024B-005)the Gansu Province National Science Foundation(22YF7GA182)the Fundamental Research Funds for the Central Universities(No.lzujbky2022-kb01)。
文摘Modal parameters can accurately characterize the structural dynamic properties and assess the physical state of the structure.Therefore,it is particularly significant to identify the structural modal parameters according to the monitoring data information in the structural health monitoring(SHM)system,so as to provide a scientific basis for structural damage identification and dynamic model modification.In view of this,this paper reviews methods for identifying structural modal parameters under environmental excitation and briefly describes how to identify structural damages based on the derived modal parameters.The paper primarily introduces data-driven modal parameter recognition methods(e.g.,time-domain,frequency-domain,and time-frequency-domain methods,etc.),briefly describes damage identification methods based on the variations of modal parameters(e.g.,natural frequency,modal shapes,and curvature modal shapes,etc.)and modal validation methods(e.g.,Stability Diagram and Modal Assurance Criterion,etc.).The current status of the application of artificial intelligence(AI)methods in the direction of modal parameter recognition and damage identification is further discussed.Based on the pre-vious analysis,the main development trends of structural modal parameter recognition and damage identification methods are given to provide scientific references for the optimized design and functional upgrading of SHM systems.
基金Supported by The Project from Department of Science and Technology of Shandong Province Under Grant No. 2007GG20008001 and 2010GSF10805
文摘By using the high spatial and temporal resolution Jinan Doppler Weather Radar data and Jinan,Xingtai sounding data,the radar signature and mesocyclone parameters of 54 supercells during 2003-2008 were analyzed.The results showed that the probability of a supercell forming would be higher when SI (showalter index) ≤ -2℃,K (K index) ≥ 30℃ and 0-6 km wind shear>15 m/s.The supercell storms can generally be divided into two categories,namely,type of isolation and mosaic type.To the type of isolation,the max reflectivity,cell-based VIL,max reflectivity height,cell top,mesocyclone base and top were significantly higher than the mosaic type.Isolation-type supercells had significantly higher probability of hail,lower probability of gale than the mosaic category.The mesocyclone attribute differences between isolation-type and mosaic type supercells determined the differences of storm structures and severe weather phenomenon.
基金Doctoral Startup Fund(20192066,20212028)Laijin Excellent Doctoral Fund(20202021)+1 种基金Scientific and Technological Innovation of Colleges and Universities in Shanxi Province(2020L0342)Fundamental Research Program of Shanxi Province(202303021222178)。
文摘SiC/Al-based composite foams were prepared by a two-step foaming method.The influence of the SiC content and its distribution uniformity on the foaming stability,cell structure,and mechanical properties of the aluminum foams was investigated.The macro/micro-features of the aluminum foams were characterized and analyzed.Results demonstrate that an appropriate increase in SiC content and the uniform distribution of SiC can improve the foaming stability,optimize the cell diameter and cell wall thickness,ameliorate the cell distribution,and enhance the hardness and compressive strength of the aluminum foams.However,either insufficient or excessive SiC leads to uneven distribution of SiC particles,which is unfavorable to foaming stability and good cell structure formation.With 6wt%SiC,both the foaming stability and cell structure of the aluminum foam reach the optimal state,resulting in the highest compressive strength and optimal energy absorption capacity.
文摘China has set its economic growth target for 2026 in the range of 4.5-5 percent.After three consecutive years of aiming for growth of around 5 percent,the slightly adjusted range reflects a prudent assessment of a complex global environment while still signalling a commitment to stable development.
基金National Natural Science Foundation of China under Grant No.52278340Natural Science Foundation of Hebei Province under Grant No.E2023202028。
文摘In this study,the dynamic characteristics and microstructures of lacustrine soft clays were studied.Dynamic character tests were conducted on undisturbed,remolded,and saturated lacustrine soft clays,using a dynamic triaxial tester.A scanning electron microscope(SEM)was employed to assess the soil samples after dynamic testing.The results indicate that the dynamic characteristics of lacustrine soft clay were significantly affected by confining pressure and water content.A quantitative relationship was established among confining pressures,water content,and the dynamic shear modulus ratio.The dynamic characteristic parameters of undisturbed,remolded and saturated soil are obviously different,and the original structure can enhance the shear strength of soil.By comparing the results with those from other studies,we found that the dynamic characters of soft clays were considerably varied in different regions,and lacustrine soft clays had a larger dynamic shear modulus ratio and a smaller damping ratio when the dynamic shear strain was large.Using IPP software to process the microstructural images,we found that the soil was dominated by small pores and medium particles,and the roundness of pores and particles had an apparently positive correlation with the maximum diameter.Moreover,the pores and particles of the soil showed fractal characteristics and directionality,and the fractal dimensions and probability entropy were strongly correlated with the macrostructural parameters.Finally,we developed a prediction model for macrostructural and microstructural parameters.
基金supported by the National Key Research and Development Plan(Grant No.2022YFB3401901)the National Natural Science Foundation of China(Grant Nos.12192210,12192214,12072295,and 12222209)+1 种基金Independent Project of State Key Laboratory of Rail Transit Vehicle System(Grant No.2023TPL-T03)Fundamental Research Funds for the Central Universities(Grant No.2682023CG004).
文摘The S38C railway axle undergoes induction hardening,resulting in a gradient-distributed microstructure and mechanical properties.The accurate identification of gradient-distributed plastic parameters for the S38C axle remains a challenging task.To tackle this challenge,the present study proposes a novel approach for identifying the gradient-distributed plastic parameters for the S38C axle by integrating nano-indentation techniques with the machine learning method.Firstly,nano-indentation tests are conducted along the radial direction of the S38C axle to obtain the gradient-distributed load-displacement curves,nano-hardness,and elastic modulus.Subsequently,the dimensionless analysis is performed to obtain the representative stress,strain,and yield stress from load-displacement curves.These parameters are then incorporated into the machine learning method as physical information to identify the gradient-distributed plastic parameters of the S38C axle.The results indicate that the proposed method based on the physics-informed neural network and multi-fidelity neural network successfully identifies the gradient-distributed plastic parameters of the S38C axles and demonstrates superior prediction accuracy and generalization compared with the purely data-driven machine learning method.
基金sponsored by the General Program of the National Natural Science Foundation of China(Grant No.42407221)the Open Fund of State Key Laboratory of Geohazard Prevention and Geoenvironment Protection(Grant No.SKLGP2024K009)the Hubei Provincial Natural Science Foun-dation,China(Grant No.2023AFB567).
文摘Water storage in the Three Gorges Reservoir in China has increased the regional microseismicity.Bedding-rock landslides,one of the most common slope structures in the Three Gorges Reservoir,are highly prone to sliding under seismic loading.Existing research primarily focuses on the stability of bedding rock landslides under strong earthquakes,while studies on the cumulative damage and long-term stability of bedding rock landslides under high-frequency microseismicity remain immature.In this study,we considered bedding rock landslides under high-frequency microseismicity in the Three Gorges Reservoir area as the research subject and equivalent microseismicity as pre-peak cyclic loading.First,we analyzed the shear strength deterioration of rock mass structural planes under pre-peak cyclic loading conditions and found that the deformation and failure of structural planes involve contact and damage effects.The shear strength of the rock mass structural planes under pre-peak cyclic loading conditions is affected by the confining pressure,loading rate,loading amplitude,and number of loading cycles.Among these factors,the shear strength of the structural planes was the most sensitive to the number of loading cycles.As the number of cycles increased,the rock mass structural planes underwent three stages:stress adjustment(increase in shear strength),fatigue damage(gradual decrease in shear strength),and structural failure(rapid decrease in shear strength).The stability of bedding rock landslides under high-frequency microseismicity was analyzed,revealing that the stability of bedding rock landslides under high-frequency microseismicity can be divided into three stages:short-term enhancement,gradual degradation,and rapid deterioration,exhibiting characteristics of gradual and sudden changes.
文摘This study investigates the thermo–mechanical behavior of C40 concrete and reinforced concrete subjected to elevated temperatures up to 700℃by integrating experimental testing and advanced numerical modeling.A temperature-indexed Concrete Damage Plasticity(CDP)framework incorporating bond–slip effects was developed in Abaqus to capture both global stress–strain responses and localized damage evolution.Uniaxial compression tests on thermally exposed cylinders provided residual strength data and failure observations for model calibration and validation.Results demonstrated a distinct two-stage degradation regime:moderate stiffness and strength reduction up to~400℃,followed by sharp deterioration beyond 500℃–600℃,with residual capacity at 700℃reduced to~20%–25%of the ambient value.Strain–damage analyses revealed the formation of a peripheral tensile strain band,which thickened and propagated inward with increasing temperature,governing crack initiation and cover spalling.Supplemental analyses highlighted that transverse reinforcement improved ductility and damage distribution at moderate temperatures(~300℃),but bond deterioration and steel softening beyond~600℃substantially diminished confinement effectiveness.The proposed CDP model accurately reproduced experimental stress–strain curves(R^(2)≈0.94–0.98 up to 600℃;≈0.90 at 700℃),with peak stress errors within 7%–10%and energy absorption captured within~12%.These findings confirm the robustness of the temperature-indexed CDP framework for simulating fire-damaged reinforced concrete and provide practical guidelines for post-fire assessment,spalling detection,and fire-resilient design of structural members.
基金sponsored by the National Nature Science Foundation of China (Grant No.40904034 and 40839905)
文摘With a more complex pore structure system compared with clastic rocks, carbonate rocks have not yet been well described by existing conventional rock physical models concerning the pore structure vagary as well as the influence on elastic rock properties. We start with a discussion and an analysis about carbonate rock pore structure utilizing rock slices. Then, given appropriate assumptions, we introduce a new approach to modeling carbonate rocks and construct a pore structure algorithm to identify pore structure mutation with a basis on the Gassmann equation and the Eshelby-Walsh ellipsoid inclusion crack theory. Finally, we compute a single well＇s porosity using this new approach with full wave log data and make a comparison with the predicted result of traditional method and simultaneously invert for reservoir parameters. The study results reveal that the rock pore structure can significantly influence the rocks＇ elastic properties and the predicted porosity error of the new modeling approach is merely 0.74%. Therefore, the approach we introduce can effectively decrease the predicted error of reservoir parameters.
基金financially supported by the National Key Research and Development Program of China(No.2022YFB3705601)the National Natural Science Foundation of China(No.52371092)the China Postdoctoral Science Foundation(No.2024M762659)
文摘The trade-off between strength and ductility remains a significant challenge in titanium alloy development.Micro structural engineering is a cost-effective alternative to balance strength and ductility.In this study,three micro structures were produced in low-cost titanium alloys via solution treatment,and the alloys withα,α'-martensite,andβphases exhibited an optimal strengthductility combination.The hierarchical phase structure,α'-martensite reorientation,multi-oriented nanotwins,and dislocation interactions collectively contributed to its high yield strength(~1015 MPa),ultimate tensile strength(~1307 MPa),and satisfactory ductility(~13%).Importantly,this study reveals a new pathway for nanotwin formation inα'phases and provides key insights for optimizing the mechanical properties of low-cost titanium alloys.
基金supported by the National Key Research and Development Program of China(No.2021YFA1200203)the National Natural Science Foundation of China(Nos.52371097,51922026,and 52301136).
文摘Compositionally-complex alloys(CCAs)with the face-centered cubic(fcc)structure exhibit excellent frac-ture toughness and stable mechanical property across a broad temperature range from cryogenic to room temperatures.However,yield strength of those alloys is usually low,making them difficult to meet the demands of practical engineering application.In a prototype CCA with the nominal chemical composition of Co10Cr10Fe49Mn30N1(atom percent),a multi-scaled heterostructure from sample to atomic scales was obtained by performing triaxial cyclic compression and short-term annealing on the blocky alloy.The ma-terial exhibits a heterogeneous distribution of strain at the sample scale.At the grain scale,dense twins and twin-twin network,laths featured with local chemical order as well as dislocation cells jointly hinder plastic deformation.At the nanoscale,the chemical order within grains also impedes dislocation motion.During plastic deformation,different sample positions within the heterogeneous material and various regions at each position undergo coordinated deformation,resulting in significant hetero-deformation in-duced strengthening.Simultaneously,the continuously activated dislocations,stacking faults and nano-twins lead to a high yield strength of 1020 MPa in the material while maintaining a fracture elongation of 30%.This study provides new insights for the design and development of high-performance metallic materials.
基金financially supported by the National Natural Science Foundation of China(Nos.52321001,52322105,52130002,U2241245,52261135634 and 52371084)the Youth Innovation Promotion Association(CAS,No.2021192)the IMR Innovation Fund(No.2023-ZD01).
文摘Metastable β titanium alloy is an ideal material for lightweight and high strength due to its excellent comprehensive mechanical properties.However,overcoming the trade-off relation between strength and ductility remains a significant challenge.In this study,the mechanical properties of Ti-38644 alloy were optimized by introducing a heterogeneous bi-grain bi-lamella(BG-BL)structure through a well-designed combination of rolling,drawing and heat treatment.The results demonstrate that the present BG-BL Ti-38644 alloy shows a tensile strength of~1500 MPa and a total elongation of 18%.In particular,the high strength-elongation combination of the BG-BL Ti-38644 alloy breakthroughs the trade-off relation in all the titanium alloys available.The recrystallized grains with low dislocation enhance the ductility of the Ti-38644 alloy,while the highly distorted elongated grains mainly contribute to the high strength.The present study provides a new principle for designing Ti alloys with superior strength and ductility.
基金supported by the Zhumadian 2023 Major Science and Technology Special Project(Grant No.ZMDSZDZX2023002)the Postgraduate Education Reform and Quality Improvement Project of Henan Province(Grant No.YJS2023JD52).
文摘This paper employs the Direct Finite Element Squared(DFE2)method to develop Sparse Polynomial Chaos Expansions(SPCE)models for analyzing the electromechanical properties of multiscale piezoelectric structures.By incorporating variations in piezoelectric and elastic constants,the DFE2 method is utilized to simulate the statistical characteristics—such as expected values and standard deviations—of electromechanical properties,including Mises stress,maximum in-plane principal strain,electric potential gradient,and electric potential,under varying parameters.This approach achieves a balance between computational efficiency and accuracy.Different SPCE models are used to investigate the influence of piezoelectric and elastic constants on multiscale piezoelectric materials.Additionally,the multiscale parameterization study investigates how microscale material properties affect the macroscopic response of these structures and materials.
基金supported by the National Natural Science Foundation of China(No.51974212)the China Baowu Low Carbon Metallurgy Innovation Foundation(No.BWLCF202116)+2 种基金the Science and Technology Major Project of Wuhan(No.2023020302020572)the Postdoctor Project of Hubei Province(No.2024HBBHCXA074)the Foundation of Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education(No.FMRUlab23-04).
文摘Coke is the only solid charge component in the lower part of the blast furnace,and its strength is crucial to its production.Si and Al are the two most abundant elements in coke ash.The influences of these oxides on the tensile strength of the coke matrix were studied by splitting tests.According to the Weibull analysis,with increasing Si and Al oxide concentrations,the fracture stress range of the coke widened,the upper and lower limits decreased,the probability of fracture under the same stress conditions increased,and the randomness and dispersion of strength increased.These results can be attributed to the inhibitory effect of ash during coal pyrolysis.Ash impedes the growth and contact of mesophase,leading to a decrease in graphitic carbon structures and an increase in edge carbon and aliphatic carbon structures in the resulting coke.Consequently,the overall ordering of the carbon structure is reduced.Moreover,SiO_(2)and Al_(2)O_(3)promoted the development of coke pores,thinned the coke pore wall,and significantly increased the proportion of large pores(>500μm).Moreover,Al_(2)O_(3)had more significant influences on the coke strength,carbon structure and stomatal ratio than SiO_(2).In addition,the position where the ash particles bonded to the carbon matrix easily produced cracks and holes,and the sharp edge of the matrix was likely to produce stress concentration points when subjected to an external force,leading to structural damage.Therefore,controlling the concentration of ash could effectively reduce the number of structural defects inside coke,which is conducive to improving the strength.
基金Funded by National Natural Science Foundation of China(No.52172019)Shandong Provincial Youth Innovation Team Development Plan of Colleges and Universities(No.2022KJ100)。
文摘The effects of different Al_(2)O_(3)/SiO_(2)(Al/Si)ratios on the structure and tensile strength of Na_(2)O-CaO-MgO-Al_(2)O_(3)-SiO_(2)glass fiber were investigated by Raman,tensile strength tests and molecular dynamics simulation.The results showed that Al^(3+)mainly existed in the form of[AlO_(4)]within the glass network.With the increase of Al/Si ratio,the Si-O-Al linkage gradually became the main connection mode of glass network.The increase of bridging oxygen content and variation of Q^(n) indicated that a higher degree of network polymerization was formed.The tensile strength of the glass fibers obtained through experiments increased from 2653.56 to 2856.83 MPa,which was confirmed by the corresponding molecular dynamics simulation.During the stretching process,the Si-O bonds in the Si-O-Al linkage tended to break regardless of the compositional changes,and the increase of fractured Si-O-Al and Al-O-Al linkage absorbed more energy to resist the destroy.
基金supported by the National Natural Science Foundation of China(Nos.52371093 and 52171104)the National Key Research and Development Program of China(No.2021YFB3701100)the Chongqing Research Program of Basic Research and Frontier Technology,China(Nos.CSTB2023NSCQ-BSX0036 and cstc2021ycjh-bgzxm0086).
文摘The low strength of Mg-Li alloys sets a limit to lightweight applications.Introducing crystal defects(twins,dislocations,and SFs)is a distinctive strategy for maintaining good mechanical properties of metallic materials.A lamellar-structured Mg-4Li-3Al-0.4Ca alloy with high performance was prepared by hot extrusion and rotary swaging.The as-swaged alloy exhibits excellent mechanical properties with tensile strength,yield strength,elongation to failure,and specific strength of 391 MPa,312 MPa,14.2%,and 238.4 kN m kg^(-1),respectively.The average grain size of the as-swaged alloy is 160±23 nm,and the microstructure is mainly composed of lamellar structures,twins,ultrafine grains,and nano-grains.The abundant lamellar structures and twins promote the storage of dislocations and SFs,leading to the formation of twin-twin interactions and enhancing strain hardening.The formation of UFG and NG by dynamic recrystallization further improves the yield strength.Shearable second phases play a critical role in enhancing the yield strength and ductility.More importantly,extensive planar dislocation glide and(c+a)dislocations efficiently relax the local stress concentrations,and thus improve the ductility.
