To investigate the influence of coarse aggregate parent rock properties on the elastic modulus of concrete,the mineralogical properties and stress-strain curves of granite and dolomite parent rocks,as well as the stre...To investigate the influence of coarse aggregate parent rock properties on the elastic modulus of concrete,the mineralogical properties and stress-strain curves of granite and dolomite parent rocks,as well as the strength and elastic modulus of mortar and concrete prepared with mechanism aggregates of the corresponding lithology,and the stress-strain curves of concrete were investigated.In this paper,a coarse aggregate and mortar matrix bonding assumption is proposed,and a prediction model for the elastic modulus of mortar is established by considering the lithology of the mechanism sand and the slurry components.An equivalent coarse aggregate elastic modulus model was established by considering factors such as coarse aggregate particle size,volume fraction,and mortar thickness between coarse aggregates.Based on the elastic modulus of the equivalent coarse aggregate and the remaining mortar,a prediction model for the elastic modulus of the two and three components of concrete in series and then in parallel was established,and the predicted values differed from the measured values within 10%.It is proposed that the coarse aggregate elastic modulus in highstrength concrete is the most critical factor affecting the elastic modulus of concrete,and as the coarse aggregate elastic modulus increases by 27.7%,the concrete elastic modulus increases by 19.5%.展开更多
Alkali-free SiO_(2)-Al_(2)O_(3)-CaO-MgO with different SiO_(2)/Al_(2)O_(3)mass ratios was prepared by conventional melt quenching method.The glass network structure,thermodynamic properties and elastic modulus changes...Alkali-free SiO_(2)-Al_(2)O_(3)-CaO-MgO with different SiO_(2)/Al_(2)O_(3)mass ratios was prepared by conventional melt quenching method.The glass network structure,thermodynamic properties and elastic modulus changes with SiO_(2)and Al_(2)O_(3)ratios were investigated using various techniques.It is found that when SiO_(2)is replaced by Al_(2)O_(3),the Q^(4) to Q^(3) transition of silicon-oxygen network decreases while the aluminum-oxygen network increases,which result in the transformation of Si-O-Si bonds to Si-O-Al bonds and an increase in glass network connectivity even though the intermolecular bond strength decreases.The glass transition temperature(T_(g))increases continuously,while the thermal expansion coefficient increases and high-temperature viscosity first decreases and then increases.Meanwhile,the elastic modulus values increase from 93 to 102 GPa.This indicates that the elastic modulus is mainly affected by packing factor and dissociation energy,and elements with higher packing factors and dissociation energies supplant those with lower values,resulting in increased rigidity within the glass.展开更多
Young's modulus and Poisson's ratio are crucial parameters for reservoir characterization and rock brittleness evaluation.Conventional methods often rely on indirect computation or approximations of the Zoeppr...Young's modulus and Poisson's ratio are crucial parameters for reservoir characterization and rock brittleness evaluation.Conventional methods often rely on indirect computation or approximations of the Zoeppritz equations to estimate Young's modulus,which can introduce cumulative errors and reduce the accuracy of inversion results.To address these issues,this paper introduces the analytical solution of the Zoeppritz equation into the inversion process.The equation is re-derived and expressed in terms of Young's modulus,Poisson's ratio,and density.Within the Bayesian framework,we construct an objective function for the joint inversion of PP and PS waves.Traditional gradient-based algorithms often suffer from low precision and the computational complexity.In this study,we address limitations of conventional approaches related to low precision and complicated code by using Circle chaotic mapping,Levy flights,and Gaussian mutation to optimize the quantum particle swarm optimization(QPSO),named improved quantum particle swarm optimization(IQPSO).The IQPSO demonstrates superior global optimization capabilities.We test the proposed inversion method with both synthetic and field data.The test results demonstrate the proposed method's feasibility and effectiveness,indicating an improvement in inversion accuracy over traditional methods.展开更多
Optogenetic has been widely applied in various pathogenesis investigations of neuropathic diseases since its accurate and targeted regulation of neuronal activity.However,due to the mismatch between the soft tissues a...Optogenetic has been widely applied in various pathogenesis investigations of neuropathic diseases since its accurate and targeted regulation of neuronal activity.However,due to the mismatch between the soft tissues and the optical waveguide,the long-term neural regulation within soft tissue(such as brain and spinal cord)by implantable optical fibers is a large challenge.Herein,we designed a modulus selfadaptive hydrogel optical fiber(MSHOF)with tunable mechanical properties(Young’modulus was tunable in the range of 0.32-10.56MPa)and low light attenuation(0.12-0.21 dB/cm,472nm laser light),which adapts to light transmission under soft tissues.These advantages of MSHOF can ensure the effectiveness of optogenetic stimulation meanwhile safeguarding the safety of the brain/materials interaction interface.In addition,this work provides more design possibilities of MSHOF for photogenetic stimuli and has significant application prospects in photomedical therapy.展开更多
Porous designs effectively reduce stress shielding in metallic orthopedic implants.However,current porous structures often fail to adequately meet the needs of patients with osteoporosis and low-modulus body regions.T...Porous designs effectively reduce stress shielding in metallic orthopedic implants.However,current porous structures often fail to adequately meet the needs of patients with osteoporosis and low-modulus body regions.This study proposes a sinusoidal-based lattice structure for an ultralow and widely tunable modulus design,aiming to match diverse bone tissue requirements and enhance biomechanical compatibility.Parametric modeling and finite element analysis were used to evaluate the performance of this structure.Results show that,within the design range suitable for bone growth,the elastic modulus of this lattice structure is tunable over a wide range,from 0.09 to 32.67 GPa,outperforming existing porous structures.The lowest value closely matched the minimum mechanical properties of human cancellous bone among porous structures.Moreover,the structure exhibited distinct anisotropic characteristics,allowing for directional design based on mechanical requirements.The structure’s permeability ranged from 1.19×10^(-8) m^(2) to 2.3×10^(-7) m^(2),making it highly compatible with human cancellous bone and meeting the requirements of orthopedic implants.Samples with porosities ranging from 46% to 87% were successfully fabricated using powder bed fusion additive manufacturing,validating the simulation predictions.This tunable low-modulus lattice structure provides a novel approach for developing personalized orthopedic implants,particularly for patients with specialized needs such as osteoporosis,and can potentially enhance biomechanical compatibility and long-term stability.展开更多
Discrete fracture network(DFN)commonly existing in natural rock masses plays an important role in geological complexity which can influence rock fracturing behaviour during fluid injection.This paper simulated the hyd...Discrete fracture network(DFN)commonly existing in natural rock masses plays an important role in geological complexity which can influence rock fracturing behaviour during fluid injection.This paper simulated the hydraulic fracturing process in lab-scale coal samples with DFNs and the induced seismic activities by the discrete element method(DEM).The effects of DFNs on hydraulic fracturing,induced seismicity and elastic property changes have been concluded.Denser DFNs can comprehensively decrease the peak injection pressure and injection duration.The proportion of strong seismic events increases first and then decreases with increasing DFN density.In addition,the relative modulus of the rock mass is derived innovatively from breakdown pressure,breakdown fracture length and the related initiation time.Increasing DFN densities among large(35–60 degrees)and small(0–30 degrees)fracture dip angles show opposite evolution trends in relative modulus.The transitional point(dip angle)for the opposite trends is also proportionally affected by the friction angle of the rock mass.The modelling results have much practical meaning to infer the density and geometry of pre-existing fractures and the elastic property of rock mass in the field,simply based on the hydraulic fracturing and induced seismicity monitoring data.展开更多
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
The dynamic and static modulus of elasticity （MOE） between bluestained and non-bluestained lumber of Lodgepole pine were tested and analyzed by using three methods of Non-destructive testing （NDT）, Portable Ultras...The dynamic and static modulus of elasticity （MOE） between bluestained and non-bluestained lumber of Lodgepole pine were tested and analyzed by using three methods of Non-destructive testing （NDT）, Portable Ultrasonic Non-destructive Digital Indicating Testing （Pundit）, Metriguard and Fast Fourier Transform （FFT） and the normal bending method. Results showed that the dynamic and static MOE of bluestained wood were higher than those of non-bluestained wood. The significant differences in dynamic MOE and static MOE were found between bulestained and non-bluestained wood, of which, the difference in each of three dynamic MOE （Ep. the ultrasonic wave modulus of elasticity, Ems, the stress wave modulus of elasticity and El, the longitudinal wave modulus of elasticity） between bulestained and non-bluestained wood arrived at the 0.01 significance level, whereas that in the static MOE at the 0.05 significance level. The differences in MOE between bulestained and non-bluestained wood were induced by the variation between sapwood and heartwood and the different densities of bulestained and non-bluestained wood. The correlation between dynamic MOE and static MOE was statistically significant at the 0.01 significance level. Although the dynamic MOE values of Ep, Em, Er were significantly different, there exists a close relationship between them （arriving at the 0.01 correlation level）. Comparative analysis among the three techniques indicated that the accurateness of FFT was higher than that of Pundit and Metriguard. Effect of tree knots on MOE was also investigated. Result showed that the dynamic and static MOE gradually decreased with the increase of knot number, indicating that knot number had significant effect on MOE value.展开更多
Geomechanical properties of rocks vary across different measurement scales,primarily due to heterogeneity.Micro-scale geomechanical tests,including micro-scale“scratch tests”and nano-scale nanoindentation tests,are ...Geomechanical properties of rocks vary across different measurement scales,primarily due to heterogeneity.Micro-scale geomechanical tests,including micro-scale“scratch tests”and nano-scale nanoindentation tests,are attractive at different scales.Each method requires minimal sample volume,is low cost,and includes a relatively rapid measurement turnaround time.However,recent micro-scale test results–including scratch test results and nanoindentation results–exhibit tangible variance and uncertainty,suggesting a need to correlate mineral composition mapping to elastic modulus mapping to isolate the relative impact of specific minerals.Different research labs often utilize different interpretation methods,and it is clear that future micro-mechanical tests may benefit from standardized testing and interpretation procedures.The objectives of this study are to seek options for standardized testing and interpretation procedures,through two specific objectives:(1)Quantify chemical and physical controls on micro-mechanical properties and(2)Quantify the source of uncertainties associated with nanoindentation measurements.To reach these goals,we conducted mechanical tests on three different scales:triaxial compression tests,scratch tests,and nanoindentation tests.We found that mineral phase weight percentage is highly correlated with nanoindentation elastic modulus distribution.Finally,we conclude that nanoindentation testing is a mineralogy and microstructure-based method and generally yields significant uncertainty and overestimation.The uncertainty of the testing method is largely associated with not mapping pore space a priori.Lastly,the uncertainty can be reduced by combining phase mapping and modulus mapping with substantial and random data sampling.展开更多
The successful development of shale oil and gas reservoirs is the biggest technological revolution in the oil and gas industry.Its key technologies are horizontal well drilling and fracturing,which are based on unders...The successful development of shale oil and gas reservoirs is the biggest technological revolution in the oil and gas industry.Its key technologies are horizontal well drilling and fracturing,which are based on understanding the mechanical properties of reservoir rocks.Therefore,it is critical to obtain the reservoir mechanical parameters quickly,efficiently,and inexpensively.In this study,shale samples were collected from three basins in Southwest China,and the elastic modulus of shale in the indentation depth range of 0-5000 nm was obtained by nanoindentation experiments.Experimental results showed that different indentation depths had different physical characteristics.The shallower depths had the mechanical properties of single minerals,while the deeper depths had the mechanical properties of a multi-mineral composite.The difference between the two represented the cementation strength between the mineral particles.The error between the calculation results of the existing equivalent medium theoretical model and experimental data reached 324%.In this study,a weak cementation model was adopted,and three parameters obtained by nanoindentation experiments were considered:the soft component volume content,intergranular cementation strength,and mineral particle size.This solved the problem of assuming rather than calculating the values of some parameters in the existing model and realized the prediction of the macroscopic mechanical parameters of shale.The calculation error was reduced to less than 20%,and the test method and calculation model can be popularized and applied in engineering.展开更多
Magnesium,being the lightest structural metal,faces limitations in alloy development due to its inherently low elastic modulus.Therefore,this study develops high-performance,high-modulus Mg-15Gd-8Y-xAl-0.3Mn(wt.%)(x=6...Magnesium,being the lightest structural metal,faces limitations in alloy development due to its inherently low elastic modulus.Therefore,this study develops high-performance,high-modulus Mg-15Gd-8Y-xAl-0.3Mn(wt.%)(x=6,8,10)alloys and investigates their microstructure and mechanical properties.The findings indicate that the alloys primarily consist of Al_(2)RE andα-Mg phases,with both the amount and size of Al_(2)RE phase increasing as the Al content rises.After extrusion,both the grains and the Al_(2)RE phase are refined.The increased modulus of the alloys is mainly due to the formation of the high-modulus Al_(2)RE phase.When the Al content is 6%,8%,and 10%,the modulus of the alloys is 51.8 GPa,53.8 GPa,and 56.1 GPa,respectively.Additionally,the Al_(2)RE and Mg5RE phases can jointly regulate the microstructure and mechanical properties of the alloys.As the Al content increases,the amount of Al_(2)RE phase increases,consuming the rare earth elements in the alloy and reducing the nano-precipitated Mg5RE phase.Consequently,with the increase in Al content,the recrystallization rate increases,and the recrystallized grains become larger.When the Al content is 6%,the alloy exhibits a bimodal structure with the smallest recrystallized grains,resulting in the highest yield strength of 341 MPa.When the Al content is 8%,the alloy has a fine,fully recrystallized structure,leading to a relatively high elongation of 9.1%.These findings provide valuable insights for designing high-modulus magnesium alloys with optimized yield strength and elongation for structural applications.展开更多
Compared to conventional thermomechanical processing,additive manufacturing offers the advantage of producing a strong <100> texture in β-Ti alloys for a low elastic modulus.Further reducing the elastic modulus...Compared to conventional thermomechanical processing,additive manufacturing offers the advantage of producing a strong <100> texture in β-Ti alloys for a low elastic modulus.Further reducing the elastic modulus of these additively manufactured alloys to values closer to that of bone tissue would be beneficial for practical applications.In this work,a β-type Ti-24Nb-4Zr-8Sn alloy was fabricated via electron beam melting to investigate its microstructure and mechanical properties.The results indicate that samples built vertically relative to the build orientation can achieve a dynamic elastic modulus of 39.5 GPa,which is about 15 GPa lower than those of the most additively manufactured titanium alloys.This is coupled with a high strength-to-modulus ratio of 1.7% and an elongation exceeding 30%.These favorable properties are attributed to a strong <100> texture of the β-phase matrix combined with an electron-to-atom ratio of 4.15,which is close to the elastic stability limit of the bodycentered cubic crystal.Aided by its orientation-dependent elastic moduli of single crystals,a model was established to evaluate the elastic anisotropy of the as-manufactured samples and to get a method to further reduce the elastic modulus.These results would be helpful for additively manufactured titanium alloys to further reduce elastic modulus and improve biomechanical compatibility.展开更多
We proposed a microscopic mechanical model for the effective elastic modulus of resin mineral composites based on the Mori-Tanaka method and equivalent inclusion theory to predict the elastic modulus of these material...We proposed a microscopic mechanical model for the effective elastic modulus of resin mineral composites based on the Mori-Tanaka method and equivalent inclusion theory to predict the elastic modulus of these materials.The model-predicted values were compared with the experimental results.The results show that when the resin dosage is lower than 10 wt%,the predicted value is lower than the measured value,and the decrease in porosity is obvious;when the resin dosage is higher than 10 wt%,the predicted value is higher than the measured value,the maximum error is 7.95%,and the decrease of porosity is not obvious.The model can predict the trend of the change of elastic modulus.The elastic modulus of resin mineral composites decreases with the increase of porosity.Therefore,the resin dosage should be controlled within 10 wt%when designing the experiments,which provides a guiding direction for the mechanical properties of resin mineral composites to be improved afterward.展开更多
As an emerging multifunctional metal with the lowest melting point except for mercury,gallium combines a wide range of metallic and non-metallic elements to form advanced semiconductors critically important in cutting...As an emerging multifunctional metal with the lowest melting point except for mercury,gallium combines a wide range of metallic and non-metallic elements to form advanced semiconductors critically important in cutting-edge technologies.However,due to its low melting point and poor machinability,it is quite difficult to simultaneously characterize gallium’s elastic properties and damping characteristics using conventional methods,which is es-sential in designing and evaluating gallium-based structures.Therefore,developing effective methods to achieve accurate and efficient measurements of Young’s modulus and corresponding internal friction of gallium is of great significance.This letter studies simultaneous measurements of the variations in Young’s modulus and internal friction of gallium at varying temperatures by employing the modified piezoelectric ultrasonic composite oscil-lator technique.Combining the explicit theoretical formulas with the measured resonance and anti-resonance frequencies,it has been discovered that Young’s modulus undergoes an approximately linear decrease as the temperature rises,declining from 83.84 GPa at -70℃ to 79.37 GPa at 20℃.Moreover,like aluminum in the same Group ⅢA of the Periodic Table of Elements and exhibits a grain-boundary internal friction peak,gallium displays a longitudinal internal friction peak at approximately-12°C,with the peak value reaching 1.77×10^(-3).This basic research on gallium’s elastic properties and damping characteristics under low-temperature condi-tions will inspire further explorations of the mechanical properties of a diverse spectrum of low-melting-point functional materials and facilitate applications of gallium-based structures under complex conditions.展开更多
The reduced elastic modulus Er and indentation hardness HIT of various brittle solids including ceramics,semiconductors,glasses,single crystals,and laser material were evaluated using nanoindentation.Various analysis ...The reduced elastic modulus Er and indentation hardness HIT of various brittle solids including ceramics,semiconductors,glasses,single crystals,and laser material were evaluated using nanoindentation.Various analysis procedures were compared such as Oliver&Pharr and nominal hardness-based methods,which require area function of the indenter,and other methods based on energy,displacement,contact depth,and contact stiffness,which do not require calibration of the indenter.Elastic recovery of the imprint by the Knoop indenter was also utilized to evaluate elastic moduli of brittle solids.Expressions relating HIT/Er and dimensionless nanoindentation variables(e.g.,the ratio of elastic work over total work and the ratio of permanent displacement over maximum displacement)are found to be nonlinear rather than linear for brittle solids.The plastic hardness Hp of brittle solids(except traditional glasses)extracted based on Er is found to be proportional to E_(r)√H_(IT).展开更多
Rubberized concrete is one of the most studied applications of discarded tires and offers a promising approach to developing materials with enhanced properties.The rubberized concrete mixture results in a reduced modu...Rubberized concrete is one of the most studied applications of discarded tires and offers a promising approach to developing materials with enhanced properties.The rubberized concrete mixture results in a reduced modulus of elasticity and a reduced compressive and tensile strength compared to traditional concrete.This study employs finite element simulations to investigate the elastic properties of rubberized mortar(RuM),considering the influence of inclusion stiffness and interfacial debonding.Different homogenization schemes,including Voigt,Reuss,and mean-field approaches,are implemented using DIGIMAT and ANSYS.Furthermore,the influence of the interfacial transition zone(ITZ)between mortar and rubber is analyzed by periodic homogenization.Subsequently,the influence of the ITZ is examined through a linear fracture analysis with the stress intensity factor as a key parameter,using the ANSYS SMART crack growth tool.Finally,a non-linear study in FEniCS is carried out to predict the strength of the composite material through a compression test.Comparisons with high density polyethylene(HDPE)and gravel inclusions show that increasing inclusion stiffness enhances compressive strength far more effectively than simply improving the mortar/rubber bond.Indeed,when the inclusions are much softer than the surrounding matrix,any benefit gained on the elastic modulus or strength from stronger interfacial adhesion becomes almost negligible.This study provide numerical evidence that tailoring the rubber’s intrinsic stiffness—not merely strengthening the rubber/mortar interface—is a decisive factor for improving the mechanical performance of RuM.展开更多
Lithium-sulfur(Li-S)batteries exhibit exceptional high theoretical energy density.However,their practical application is hindered by premature termination of discharge,which severely limits the discharge capacity and ...Lithium-sulfur(Li-S)batteries exhibit exceptional high theoretical energy density.However,their practical application is hindered by premature termination of discharge,which severely limits the discharge capacity and achievable energy density even at low discharge rates.This contribution identifies blocked mass transfer as the primary limitation through relaxation analysis.Both X-ray computed tomography and finite element simulation manifest that the preferential solid deposition at the working cathode surface obstructs the mass transfer pathway and triggers premature discharge termination.The Thiele modulus of a thick cathode is utilized to elucidate the disparity between electrochemical reaction and mass transfer rates,underscoring internal diffusion limitations as the root cause.This understanding affords a theoretical framework for optimizing cathode structures.By reducing the Thiele modulus,an enhanced energy density of 436 Wh kg^(-1)is achieved in Li-S pouch cells.This work advances the understanding of multi-phase reactions in Li-S batteries and offers insights to electrochemical systems involving multi-phase conversions.展开更多
Bulk modulus is a constant that measures the incompressibility of materials, which can be obtained in high pressure experiment by fitting the equations of state(EOS), like third-order Birch–Murnaghan EOS(BM EOS) and ...Bulk modulus is a constant that measures the incompressibility of materials, which can be obtained in high pressure experiment by fitting the equations of state(EOS), like third-order Birch–Murnaghan EOS(BM EOS) and Vinet EOS. Bulk modulus reflects the intermolecular interaction inside molecular crystals, making it useful for researchers to design novel high pressure materials. This review systematically examines bulk moduli of various molecular crystals, including rare-gas solids, di-atom and triplet-atom molecules, saturated organic molecules, and aromatic organic crystals. Comparisons with ionic crystals are presented, along with an analysis of connections between bulk modulus and crystal structures.展开更多
Silver paste is widely used in power electronics as a die-attach material owing to its low-temperature sinterability,high melting point,and excellent electrical and thermal conductivities in sintered joints.However,ow...Silver paste is widely used in power electronics as a die-attach material owing to its low-temperature sinterability,high melting point,and excellent electrical and thermal conductivities in sintered joints.However,owing to the mismatch in the coefficient of thermal expansion(CTE)between the joints and chip,the high Young's modulus of sintered silver hinders the mitigation of the high thermal stress generated during the operation of power modules,which increases the susceptibility of sintered joints to cracking,thereby leading to potential failure.This study developed a facile approach to synthesizing bayberry-like Ag microparticles(AgMPs)through the in situ assembly of silver nanorods,resulting in a uniform distribution of nanoscale structures and mesopores on the particle surface.These particles exhibited a high specific surface area of 2.5389 m^(2)·g^(-1),which enhanced theirsintering activity,enabling sintering to occur at 149.7℃.Furthermore,the porous structure of the AgMPs effectively reduced the density of joints formed by sintering AgMP paste,thereby lowering the Young's modulus of the joints.The small grain size and intricate internal substructure of the joints yielded high shear strength,which reached112.50 MPa at 250℃.The Young's modulus could be adjusted,and the pores provided by the AgMPs maintained the Young's modulus within a low range(15.11-29.61GPa),effectively mitigating thermal stress.These new bayberry-like porous AgMPs offer a promising option for die-attach materials in electronic packaging.展开更多
The elastic properties of membranes are typically characterized by a few phenomenological parameters,including bending and Gaussian curvature moduli measuring the membrane rigidity against its deformation and topologi...The elastic properties of membranes are typically characterized by a few phenomenological parameters,including bending and Gaussian curvature moduli measuring the membrane rigidity against its deformation and topological change,as well as spontaneous curvature arising from the asymmetry between the two leaflets in the lipid bilayers.Though tether-based and fluctuationbased experiments are commonly utilized to measure the bending modulus,measuring the Gaussian curvature modulus and the spontaneous curvature of the membrane is considered to be much more difficult.In this paper,we study the buckling process of a circular membrane with nonzero spontaneous curvature under compressive stresses.It is found that when the stress exceeds a critical value,the circular membrane will transform from a spherical cap to a buckled shape,with its buckling degree enhanced with the increase of stress until its base is constricted to almost zero.As the stress-strain relationship of the buckled membrane strongly depends on the Gaussian curvature modulus and the spontaneous curvature,we therefore propose a method to determine the Gaussian curvature modulus and the spontaneous curvature simultaneously by measuring its stress-strain relationship during a buckling process.展开更多
基金Funded by State Railway Administration Research Project(No.2023JS007)National Natural Science Foundation of China(No.52438002)+1 种基金Research and Development Programs for Science and Technology of China Railways Corporation(No.J2023G003)New Cornerstone Science Foundation through the XPLORER PRIZE。
文摘To investigate the influence of coarse aggregate parent rock properties on the elastic modulus of concrete,the mineralogical properties and stress-strain curves of granite and dolomite parent rocks,as well as the strength and elastic modulus of mortar and concrete prepared with mechanism aggregates of the corresponding lithology,and the stress-strain curves of concrete were investigated.In this paper,a coarse aggregate and mortar matrix bonding assumption is proposed,and a prediction model for the elastic modulus of mortar is established by considering the lithology of the mechanism sand and the slurry components.An equivalent coarse aggregate elastic modulus model was established by considering factors such as coarse aggregate particle size,volume fraction,and mortar thickness between coarse aggregates.Based on the elastic modulus of the equivalent coarse aggregate and the remaining mortar,a prediction model for the elastic modulus of the two and three components of concrete in series and then in parallel was established,and the predicted values differed from the measured values within 10%.It is proposed that the coarse aggregate elastic modulus in highstrength concrete is the most critical factor affecting the elastic modulus of concrete,and as the coarse aggregate elastic modulus increases by 27.7%,the concrete elastic modulus increases by 19.5%.
基金Supported by the National Key Research Program(No.2024-1129-954-112)National Natural Science Foundation of China(No.52372033)Guangxi Science and Technology Major Program(No.AA24263054)。
文摘Alkali-free SiO_(2)-Al_(2)O_(3)-CaO-MgO with different SiO_(2)/Al_(2)O_(3)mass ratios was prepared by conventional melt quenching method.The glass network structure,thermodynamic properties and elastic modulus changes with SiO_(2)and Al_(2)O_(3)ratios were investigated using various techniques.It is found that when SiO_(2)is replaced by Al_(2)O_(3),the Q^(4) to Q^(3) transition of silicon-oxygen network decreases while the aluminum-oxygen network increases,which result in the transformation of Si-O-Si bonds to Si-O-Al bonds and an increase in glass network connectivity even though the intermolecular bond strength decreases.The glass transition temperature(T_(g))increases continuously,while the thermal expansion coefficient increases and high-temperature viscosity first decreases and then increases.Meanwhile,the elastic modulus values increase from 93 to 102 GPa.This indicates that the elastic modulus is mainly affected by packing factor and dissociation energy,and elements with higher packing factors and dissociation energies supplant those with lower values,resulting in increased rigidity within the glass.
基金supported by Fundamental Research Funds for the Central Universities,CHD300102264715National Key Research and Development Program of China under Grant 2021YFA0716902Natural Science Basic Research Program of Shaanxi 2024JCYBMS-199。
文摘Young's modulus and Poisson's ratio are crucial parameters for reservoir characterization and rock brittleness evaluation.Conventional methods often rely on indirect computation or approximations of the Zoeppritz equations to estimate Young's modulus,which can introduce cumulative errors and reduce the accuracy of inversion results.To address these issues,this paper introduces the analytical solution of the Zoeppritz equation into the inversion process.The equation is re-derived and expressed in terms of Young's modulus,Poisson's ratio,and density.Within the Bayesian framework,we construct an objective function for the joint inversion of PP and PS waves.Traditional gradient-based algorithms often suffer from low precision and the computational complexity.In this study,we address limitations of conventional approaches related to low precision and complicated code by using Circle chaotic mapping,Levy flights,and Gaussian mutation to optimize the quantum particle swarm optimization(QPSO),named improved quantum particle swarm optimization(IQPSO).The IQPSO demonstrates superior global optimization capabilities.We test the proposed inversion method with both synthetic and field data.The test results demonstrate the proposed method's feasibility and effectiveness,indicating an improvement in inversion accuracy over traditional methods.
基金supported by the National Key Research and Development Program of China(Nos.2021YFA1201302 and 2021YFA1201300)the National Natural Science Foundation of China(Nos.52303033,52173029)+1 种基金Shanghai Sailing Program(No.23YF1400400)the Natural Science Foundation of Shanghai(No.21ZR1400500).
文摘Optogenetic has been widely applied in various pathogenesis investigations of neuropathic diseases since its accurate and targeted regulation of neuronal activity.However,due to the mismatch between the soft tissues and the optical waveguide,the long-term neural regulation within soft tissue(such as brain and spinal cord)by implantable optical fibers is a large challenge.Herein,we designed a modulus selfadaptive hydrogel optical fiber(MSHOF)with tunable mechanical properties(Young’modulus was tunable in the range of 0.32-10.56MPa)and low light attenuation(0.12-0.21 dB/cm,472nm laser light),which adapts to light transmission under soft tissues.These advantages of MSHOF can ensure the effectiveness of optogenetic stimulation meanwhile safeguarding the safety of the brain/materials interaction interface.In addition,this work provides more design possibilities of MSHOF for photogenetic stimuli and has significant application prospects in photomedical therapy.
基金supported by National Key R&D Program of China(Grant No.2022YFB4600500)Fundamental Research Funds for the Central Universities,and the Program for Innovation Team of Shaanxi Province(Grant No.2023-CX-TD-17).
文摘Porous designs effectively reduce stress shielding in metallic orthopedic implants.However,current porous structures often fail to adequately meet the needs of patients with osteoporosis and low-modulus body regions.This study proposes a sinusoidal-based lattice structure for an ultralow and widely tunable modulus design,aiming to match diverse bone tissue requirements and enhance biomechanical compatibility.Parametric modeling and finite element analysis were used to evaluate the performance of this structure.Results show that,within the design range suitable for bone growth,the elastic modulus of this lattice structure is tunable over a wide range,from 0.09 to 32.67 GPa,outperforming existing porous structures.The lowest value closely matched the minimum mechanical properties of human cancellous bone among porous structures.Moreover,the structure exhibited distinct anisotropic characteristics,allowing for directional design based on mechanical requirements.The structure’s permeability ranged from 1.19×10^(-8) m^(2) to 2.3×10^(-7) m^(2),making it highly compatible with human cancellous bone and meeting the requirements of orthopedic implants.Samples with porosities ranging from 46% to 87% were successfully fabricated using powder bed fusion additive manufacturing,validating the simulation predictions.This tunable low-modulus lattice structure provides a novel approach for developing personalized orthopedic implants,particularly for patients with specialized needs such as osteoporosis,and can potentially enhance biomechanical compatibility and long-term stability.
基金Australian Research Council Linkage Program(LP200301404)for sponsoring this researchthe financial support provided by the State Key Laboratory of Geohazard Prevention and Geoenvironment Protection(Chengdu University of Technology,SKLGP2021K002)National Natural Science Foundation of China(52374101,32111530138).
文摘Discrete fracture network(DFN)commonly existing in natural rock masses plays an important role in geological complexity which can influence rock fracturing behaviour during fluid injection.This paper simulated the hydraulic fracturing process in lab-scale coal samples with DFNs and the induced seismic activities by the discrete element method(DEM).The effects of DFNs on hydraulic fracturing,induced seismicity and elastic property changes have been concluded.Denser DFNs can comprehensively decrease the peak injection pressure and injection duration.The proportion of strong seismic events increases first and then decreases with increasing DFN density.In addition,the relative modulus of the rock mass is derived innovatively from breakdown pressure,breakdown fracture length and the related initiation time.Increasing DFN densities among large(35–60 degrees)and small(0–30 degrees)fracture dip angles show opposite evolution trends in relative modulus.The transitional point(dip angle)for the opposite trends is also proportionally affected by the friction angle of the rock mass.The modelling results have much practical meaning to infer the density and geometry of pre-existing fractures and the elastic property of rock mass in the field,simply based on the hydraulic fracturing and induced seismicity monitoring data.
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This paper was supported by "Wood-inorganic Res-toration Material" in "Technique Introduction and Innovation of Bio-macromolecule New Material" of Introducing Overseas Advanced Forest Technology Innovation Program of China ("948" Innovation Pro-ject, Number: 2006-4-C03)
文摘The dynamic and static modulus of elasticity （MOE） between bluestained and non-bluestained lumber of Lodgepole pine were tested and analyzed by using three methods of Non-destructive testing （NDT）, Portable Ultrasonic Non-destructive Digital Indicating Testing （Pundit）, Metriguard and Fast Fourier Transform （FFT） and the normal bending method. Results showed that the dynamic and static MOE of bluestained wood were higher than those of non-bluestained wood. The significant differences in dynamic MOE and static MOE were found between bulestained and non-bluestained wood, of which, the difference in each of three dynamic MOE （Ep. the ultrasonic wave modulus of elasticity, Ems, the stress wave modulus of elasticity and El, the longitudinal wave modulus of elasticity） between bulestained and non-bluestained wood arrived at the 0.01 significance level, whereas that in the static MOE at the 0.05 significance level. The differences in MOE between bulestained and non-bluestained wood were induced by the variation between sapwood and heartwood and the different densities of bulestained and non-bluestained wood. The correlation between dynamic MOE and static MOE was statistically significant at the 0.01 significance level. Although the dynamic MOE values of Ep, Em, Er were significantly different, there exists a close relationship between them （arriving at the 0.01 correlation level）. Comparative analysis among the three techniques indicated that the accurateness of FFT was higher than that of Pundit and Metriguard. Effect of tree knots on MOE was also investigated. Result showed that the dynamic and static MOE gradually decreased with the increase of knot number, indicating that knot number had significant effect on MOE value.
基金support of this project through the Southwest Regional Partnership on Carbon Sequestration(Grant No.DE-FC26-05NT42591)Improving Production in the Emerging Paradox Oil Play(Grant No.DE-FE0031775).
文摘Geomechanical properties of rocks vary across different measurement scales,primarily due to heterogeneity.Micro-scale geomechanical tests,including micro-scale“scratch tests”and nano-scale nanoindentation tests,are attractive at different scales.Each method requires minimal sample volume,is low cost,and includes a relatively rapid measurement turnaround time.However,recent micro-scale test results–including scratch test results and nanoindentation results–exhibit tangible variance and uncertainty,suggesting a need to correlate mineral composition mapping to elastic modulus mapping to isolate the relative impact of specific minerals.Different research labs often utilize different interpretation methods,and it is clear that future micro-mechanical tests may benefit from standardized testing and interpretation procedures.The objectives of this study are to seek options for standardized testing and interpretation procedures,through two specific objectives:(1)Quantify chemical and physical controls on micro-mechanical properties and(2)Quantify the source of uncertainties associated with nanoindentation measurements.To reach these goals,we conducted mechanical tests on three different scales:triaxial compression tests,scratch tests,and nanoindentation tests.We found that mineral phase weight percentage is highly correlated with nanoindentation elastic modulus distribution.Finally,we conclude that nanoindentation testing is a mineralogy and microstructure-based method and generally yields significant uncertainty and overestimation.The uncertainty of the testing method is largely associated with not mapping pore space a priori.Lastly,the uncertainty can be reduced by combining phase mapping and modulus mapping with substantial and random data sampling.
基金supported by the Key R&D Program Project of Xinjiang Province(2024B01013)the National Key Research and Development Program of China(2022YFE0129800).
文摘The successful development of shale oil and gas reservoirs is the biggest technological revolution in the oil and gas industry.Its key technologies are horizontal well drilling and fracturing,which are based on understanding the mechanical properties of reservoir rocks.Therefore,it is critical to obtain the reservoir mechanical parameters quickly,efficiently,and inexpensively.In this study,shale samples were collected from three basins in Southwest China,and the elastic modulus of shale in the indentation depth range of 0-5000 nm was obtained by nanoindentation experiments.Experimental results showed that different indentation depths had different physical characteristics.The shallower depths had the mechanical properties of single minerals,while the deeper depths had the mechanical properties of a multi-mineral composite.The difference between the two represented the cementation strength between the mineral particles.The error between the calculation results of the existing equivalent medium theoretical model and experimental data reached 324%.In this study,a weak cementation model was adopted,and three parameters obtained by nanoindentation experiments were considered:the soft component volume content,intergranular cementation strength,and mineral particle size.This solved the problem of assuming rather than calculating the values of some parameters in the existing model and realized the prediction of the macroscopic mechanical parameters of shale.The calculation error was reduced to less than 20%,and the test method and calculation model can be popularized and applied in engineering.
基金supported by the National Key Research&Development Program of China(Grant Nos.2021YFB3703300)the National Natural Science Foundation of China(Grant Nos.52201115,52301142,52371107)the Shanxi Provincial Science and Technology Major Special Project plan of“Taking the lead in unveiling the list”(Grant Nos.202201050201012).
文摘Magnesium,being the lightest structural metal,faces limitations in alloy development due to its inherently low elastic modulus.Therefore,this study develops high-performance,high-modulus Mg-15Gd-8Y-xAl-0.3Mn(wt.%)(x=6,8,10)alloys and investigates their microstructure and mechanical properties.The findings indicate that the alloys primarily consist of Al_(2)RE andα-Mg phases,with both the amount and size of Al_(2)RE phase increasing as the Al content rises.After extrusion,both the grains and the Al_(2)RE phase are refined.The increased modulus of the alloys is mainly due to the formation of the high-modulus Al_(2)RE phase.When the Al content is 6%,8%,and 10%,the modulus of the alloys is 51.8 GPa,53.8 GPa,and 56.1 GPa,respectively.Additionally,the Al_(2)RE and Mg5RE phases can jointly regulate the microstructure and mechanical properties of the alloys.As the Al content increases,the amount of Al_(2)RE phase increases,consuming the rare earth elements in the alloy and reducing the nano-precipitated Mg5RE phase.Consequently,with the increase in Al content,the recrystallization rate increases,and the recrystallized grains become larger.When the Al content is 6%,the alloy exhibits a bimodal structure with the smallest recrystallized grains,resulting in the highest yield strength of 341 MPa.When the Al content is 8%,the alloy has a fine,fully recrystallized structure,leading to a relatively high elongation of 9.1%.These findings provide valuable insights for designing high-modulus magnesium alloys with optimized yield strength and elongation for structural applications.
基金financially supported by the National Natural Science Foundation of China(Nos.U2341259,52401254 and 52321001)the National Key Research and Development Program of China(No.2023YFC2412600)+1 种基金the China Postdoctoral Science Foundation(No.2024M753297 and GZC20241759)the Liaoning Outstanding Youth Foundation(No.2024JH3/50100015)
文摘Compared to conventional thermomechanical processing,additive manufacturing offers the advantage of producing a strong <100> texture in β-Ti alloys for a low elastic modulus.Further reducing the elastic modulus of these additively manufactured alloys to values closer to that of bone tissue would be beneficial for practical applications.In this work,a β-type Ti-24Nb-4Zr-8Sn alloy was fabricated via electron beam melting to investigate its microstructure and mechanical properties.The results indicate that samples built vertically relative to the build orientation can achieve a dynamic elastic modulus of 39.5 GPa,which is about 15 GPa lower than those of the most additively manufactured titanium alloys.This is coupled with a high strength-to-modulus ratio of 1.7% and an elongation exceeding 30%.These favorable properties are attributed to a strong <100> texture of the β-phase matrix combined with an electron-to-atom ratio of 4.15,which is close to the elastic stability limit of the bodycentered cubic crystal.Aided by its orientation-dependent elastic moduli of single crystals,a model was established to evaluate the elastic anisotropy of the as-manufactured samples and to get a method to further reduce the elastic modulus.These results would be helpful for additively manufactured titanium alloys to further reduce elastic modulus and improve biomechanical compatibility.
基金Funded by Demonstration Platform for the Production and Application of Key Materials for High-grade CNC Machine Tools(No.2020-370104-34-03-043952)。
文摘We proposed a microscopic mechanical model for the effective elastic modulus of resin mineral composites based on the Mori-Tanaka method and equivalent inclusion theory to predict the elastic modulus of these materials.The model-predicted values were compared with the experimental results.The results show that when the resin dosage is lower than 10 wt%,the predicted value is lower than the measured value,and the decrease in porosity is obvious;when the resin dosage is higher than 10 wt%,the predicted value is higher than the measured value,the maximum error is 7.95%,and the decrease of porosity is not obvious.The model can predict the trend of the change of elastic modulus.The elastic modulus of resin mineral composites decreases with the increase of porosity.Therefore,the resin dosage should be controlled within 10 wt%when designing the experiments,which provides a guiding direction for the mechanical properties of resin mineral composites to be improved afterward.
基金financially supported by the National Key R&D Program of China(Grant No.2023YFF0716800)the National Natural Science Foundation of China(Grant No.12074160)the Natural Science Foundation of Liaoning Province of China(Grant No.2024-MS-181).
文摘As an emerging multifunctional metal with the lowest melting point except for mercury,gallium combines a wide range of metallic and non-metallic elements to form advanced semiconductors critically important in cutting-edge technologies.However,due to its low melting point and poor machinability,it is quite difficult to simultaneously characterize gallium’s elastic properties and damping characteristics using conventional methods,which is es-sential in designing and evaluating gallium-based structures.Therefore,developing effective methods to achieve accurate and efficient measurements of Young’s modulus and corresponding internal friction of gallium is of great significance.This letter studies simultaneous measurements of the variations in Young’s modulus and internal friction of gallium at varying temperatures by employing the modified piezoelectric ultrasonic composite oscil-lator technique.Combining the explicit theoretical formulas with the measured resonance and anti-resonance frequencies,it has been discovered that Young’s modulus undergoes an approximately linear decrease as the temperature rises,declining from 83.84 GPa at -70℃ to 79.37 GPa at 20℃.Moreover,like aluminum in the same Group ⅢA of the Periodic Table of Elements and exhibits a grain-boundary internal friction peak,gallium displays a longitudinal internal friction peak at approximately-12°C,with the peak value reaching 1.77×10^(-3).This basic research on gallium’s elastic properties and damping characteristics under low-temperature condi-tions will inspire further explorations of the mechanical properties of a diverse spectrum of low-melting-point functional materials and facilitate applications of gallium-based structures under complex conditions.
基金supported by the National Natural Science Foundation of China (Grant No.51705082)Fujian Provincial Minjiang Scholar Program (Grant No.0020-510759)+1 种基金Qishan Sholar program in Fuzhou University (Grant No.0020-650289)Fuzhou University Testing Fund of precious apparatus (Grant No.2023T018).
文摘The reduced elastic modulus Er and indentation hardness HIT of various brittle solids including ceramics,semiconductors,glasses,single crystals,and laser material were evaluated using nanoindentation.Various analysis procedures were compared such as Oliver&Pharr and nominal hardness-based methods,which require area function of the indenter,and other methods based on energy,displacement,contact depth,and contact stiffness,which do not require calibration of the indenter.Elastic recovery of the imprint by the Knoop indenter was also utilized to evaluate elastic moduli of brittle solids.Expressions relating HIT/Er and dimensionless nanoindentation variables(e.g.,the ratio of elastic work over total work and the ratio of permanent displacement over maximum displacement)are found to be nonlinear rather than linear for brittle solids.The plastic hardness Hp of brittle solids(except traditional glasses)extracted based on Er is found to be proportional to E_(r)√H_(IT).
基金financial support from the Chilean National Agency for Research and Development(ANID),National Doctorate No.21212028financial support from ANID,FONDECYT Regular Research Project No.1221793.
文摘Rubberized concrete is one of the most studied applications of discarded tires and offers a promising approach to developing materials with enhanced properties.The rubberized concrete mixture results in a reduced modulus of elasticity and a reduced compressive and tensile strength compared to traditional concrete.This study employs finite element simulations to investigate the elastic properties of rubberized mortar(RuM),considering the influence of inclusion stiffness and interfacial debonding.Different homogenization schemes,including Voigt,Reuss,and mean-field approaches,are implemented using DIGIMAT and ANSYS.Furthermore,the influence of the interfacial transition zone(ITZ)between mortar and rubber is analyzed by periodic homogenization.Subsequently,the influence of the ITZ is examined through a linear fracture analysis with the stress intensity factor as a key parameter,using the ANSYS SMART crack growth tool.Finally,a non-linear study in FEniCS is carried out to predict the strength of the composite material through a compression test.Comparisons with high density polyethylene(HDPE)and gravel inclusions show that increasing inclusion stiffness enhances compressive strength far more effectively than simply improving the mortar/rubber bond.Indeed,when the inclusions are much softer than the surrounding matrix,any benefit gained on the elastic modulus or strength from stronger interfacial adhesion becomes almost negligible.This study provide numerical evidence that tailoring the rubber’s intrinsic stiffness—not merely strengthening the rubber/mortar interface—is a decisive factor for improving the mechanical performance of RuM.
基金supported by the National Key Research and Development Program of China(2024YFE0209500)Relevant National Projects,the National Natural Science Foundation of China(22409116)+1 种基金the Seed Fund of Shanxi Research Institute for Clean Energy(SXKYJF015)the Shuimu Tsinghua Scholar Program of Tsinghua University。
文摘Lithium-sulfur(Li-S)batteries exhibit exceptional high theoretical energy density.However,their practical application is hindered by premature termination of discharge,which severely limits the discharge capacity and achievable energy density even at low discharge rates.This contribution identifies blocked mass transfer as the primary limitation through relaxation analysis.Both X-ray computed tomography and finite element simulation manifest that the preferential solid deposition at the working cathode surface obstructs the mass transfer pathway and triggers premature discharge termination.The Thiele modulus of a thick cathode is utilized to elucidate the disparity between electrochemical reaction and mass transfer rates,underscoring internal diffusion limitations as the root cause.This understanding affords a theoretical framework for optimizing cathode structures.By reducing the Thiele modulus,an enhanced energy density of 436 Wh kg^(-1)is achieved in Li-S pouch cells.This work advances the understanding of multi-phase reactions in Li-S batteries and offers insights to electrochemical systems involving multi-phase conversions.
基金Project supported by the National Key Research and Development Program of China (Grant Nos. 2019YFA0708502 and 2023YFA1406200)the National Natural Science Foundation of China (Grant No. 22022101)。
文摘Bulk modulus is a constant that measures the incompressibility of materials, which can be obtained in high pressure experiment by fitting the equations of state(EOS), like third-order Birch–Murnaghan EOS(BM EOS) and Vinet EOS. Bulk modulus reflects the intermolecular interaction inside molecular crystals, making it useful for researchers to design novel high pressure materials. This review systematically examines bulk moduli of various molecular crystals, including rare-gas solids, di-atom and triplet-atom molecules, saturated organic molecules, and aromatic organic crystals. Comparisons with ionic crystals are presented, along with an analysis of connections between bulk modulus and crystal structures.
基金financially supported by the National Natural Science Foundation of China(Nos.52075125 and 52105331)Guangdong Basic and Applied Basic Research Foundation(No.2023A1515010591)Shenzhen Science and Technology Innovation Committee(Nos.JCYJ20210324124203009,JSGG20201102154600003,GXWD20231130103814001,GXWD20220721182229001)
文摘Silver paste is widely used in power electronics as a die-attach material owing to its low-temperature sinterability,high melting point,and excellent electrical and thermal conductivities in sintered joints.However,owing to the mismatch in the coefficient of thermal expansion(CTE)between the joints and chip,the high Young's modulus of sintered silver hinders the mitigation of the high thermal stress generated during the operation of power modules,which increases the susceptibility of sintered joints to cracking,thereby leading to potential failure.This study developed a facile approach to synthesizing bayberry-like Ag microparticles(AgMPs)through the in situ assembly of silver nanorods,resulting in a uniform distribution of nanoscale structures and mesopores on the particle surface.These particles exhibited a high specific surface area of 2.5389 m^(2)·g^(-1),which enhanced theirsintering activity,enabling sintering to occur at 149.7℃.Furthermore,the porous structure of the AgMPs effectively reduced the density of joints formed by sintering AgMP paste,thereby lowering the Young's modulus of the joints.The small grain size and intricate internal substructure of the joints yielded high shear strength,which reached112.50 MPa at 250℃.The Young's modulus could be adjusted,and the pores provided by the AgMPs maintained the Young's modulus within a low range(15.11-29.61GPa),effectively mitigating thermal stress.These new bayberry-like porous AgMPs offer a promising option for die-attach materials in electronic packaging.
基金the financial support from the National Natural Science Foundation of China under Grant Nos.12174323 and 12474199Fundamental Research Funds for Central Universities of China under Grant No.20720240144(RM)111 project B16029。
文摘The elastic properties of membranes are typically characterized by a few phenomenological parameters,including bending and Gaussian curvature moduli measuring the membrane rigidity against its deformation and topological change,as well as spontaneous curvature arising from the asymmetry between the two leaflets in the lipid bilayers.Though tether-based and fluctuationbased experiments are commonly utilized to measure the bending modulus,measuring the Gaussian curvature modulus and the spontaneous curvature of the membrane is considered to be much more difficult.In this paper,we study the buckling process of a circular membrane with nonzero spontaneous curvature under compressive stresses.It is found that when the stress exceeds a critical value,the circular membrane will transform from a spherical cap to a buckled shape,with its buckling degree enhanced with the increase of stress until its base is constricted to almost zero.As the stress-strain relationship of the buckled membrane strongly depends on the Gaussian curvature modulus and the spontaneous curvature,we therefore propose a method to determine the Gaussian curvature modulus and the spontaneous curvature simultaneously by measuring its stress-strain relationship during a buckling process.
