It is discussed that a tangential force T induces a self-excited vibration in the motion ofspindle blades of a ring spinning frame.Depending on the relative magnitude of the tangentialforce compared with the tangentia...It is discussed that a tangential force T induces a self-excited vibration in the motion ofspindle blades of a ring spinning frame.Depending on the relative magnitude of the tangentialforce compared with the tangential damping force the motion of blade is either stable orunstable.The chief factors causing the self-excited vibration can also be traced from the charac-ter of the experimental locus.展开更多
In this study,the shell structure of olives in nature was modeled,and a high-porosity bionic olive body-centered cubic structure(BCCO)with reinforcement structures of circular support(BCCR)and triangular support(BCCT)...In this study,the shell structure of olives in nature was modeled,and a high-porosity bionic olive body-centered cubic structure(BCCO)with reinforcement structures of circular support(BCCR)and triangular support(BCCT)with excellent mechanical properties was designed and prepared using selective laser melting technology.The surface morphology,deformation behavior,and energy absorption of BCCO were compared with those of the equivalent uniform body-centered cubic structure(BCC)and analyzed through quasi-static compression experiments and finite element analysis.The olive-shaped structure showed optimal load resistance when the radius of curvature was equal to the edge length of the lattice structure,and outperformed with a larger curvature than with a smaller curvature.With the added support structure,the energy absorption of the BCCR increased by 144.44%compared with that of the conventional BCC structure.The newly designed olive bionic structure has considerable potential for applications in various fields,such as aerospace and medical devices.展开更多
Vacancy defects,as fundamental disruptions in metallic lattices,play an important role in shaping the mechanical and electronic properties of aluminum crystals.However,the influence of vacancy position under coupled t...Vacancy defects,as fundamental disruptions in metallic lattices,play an important role in shaping the mechanical and electronic properties of aluminum crystals.However,the influence of vacancy position under coupled thermomechanical fields remains insufficiently understood.In this study,transmission and scanning electron microscopy were employed to observe dislocation structures and grain boundary heterogeneities in processed aluminum alloys,suggesting stress concentrations and microstructural inhomogeneities associated with vacancy accumulation.To complement these observations,first-principles calculations and molecular dynamics simulations were conducted for seven single-vacancy configurations in face-centered cubic aluminum.The stress response,total energy,density of states(DOS),and differential charge density were examined under varying compressive strain(ε=0–0.1)and temperature(0–600 K).The results indicate that face-centered vacancies tend to reduce mechanical strength and perturb electronic states near the Fermi level,whereas corner and edge vacancies appear to have weaker effects.Elevated temperatures may partially restore electronic uniformity through thermal excitation.Overall,these findings suggest that vacancy position exerts a critical but position-dependent influence on coupled structure-property relationships,offering theoretical insights and preliminary experimental support for defect-engineered aluminum alloy design.展开更多
This study presents a framework involving statistical modeling and machine learning to accurately predict and optimize the mechanical and damping properties of hybrid granite-epoxy(G-E)composites reinforced with cast ...This study presents a framework involving statistical modeling and machine learning to accurately predict and optimize the mechanical and damping properties of hybrid granite-epoxy(G-E)composites reinforced with cast iron(CI)filler particles.Hybrid G-E composite with added cast iron(CI)filler particles enhances stiffness,strength,and vibration damping,offering enhanced performance for vibration-sensitive engineering applications.Unlike conventional approaches,this work simultaneously employs Artificial Neural Networks(ANN)for highaccuracy property prediction and Response Surface Methodology(RSM)for in-depth analysis of factor interactions and optimization.A total of 24 experimental test data sets of varying input factors(granite weight%,epoxy weight%,and CI filler weight%)were utilized to train and test the prediction models using an ANN approach and further analyze the interaction effects using RSM.Mechanical properties,including tensile,compressive,and flexural strength,elastic modulus,density and damping properties measured under various testing conditions,were set as output parameters for prediction.This study analyzed and optimized the performance of the ANN model using Bayesian Regularization and Levenberg-Marquardt algorithms to identify the best performing number of neurons in the hidden layer for achieving the highest prediction accuracy.The proposed ANN framework achieved an exceptional average determination coefficient(R2)exceeding 99%,with Bayesian Regularization demonstrating remarkable stability in the 22-neuron range and minimal variation across all properties.RSM and ANN form a powerful framework for predicting and optimizing hybrid G-E composite properties,enabling efficient design for vibration-critical applications with reduced experimental effort and performance optimization.展开更多
To exploit the combined strengthening effects of nanotwins and carbon nanotubes(CNTs)in Cu matrix composites,the nanotwins with a width ranging from 3 to 30 nm were incorporated into the CNTs-reinforced Cu matrix comp...To exploit the combined strengthening effects of nanotwins and carbon nanotubes(CNTs)in Cu matrix composites,the nanotwins with a width ranging from 3 to 30 nm were incorporated into the CNTs-reinforced Cu matrix composites using cryogenic rolling and optimizing the initial particle size of the raw Cu powders.The formation of nanotwins in the Cu matrix composite reinforced by only 0.2 wt.%CNTs is accompanied by the increased dislocation density and refined Cu grain size,resulting in much better strength−ductility synergy than the referenced composite without significant nanotwins formation.The analysis of strengthening and toughening mechanisms demonstrates that the strength increment mainly derives from grain refinement strengthening,dislocation strengthening,and nanotwin strengthening.The strength increment from the contribution of the nanotwins accounts for 19.9%of the overall strength increment for the composite.Meanwhile,the retention of good tensile ductility can be reasonably explained by the increased dislocation accommodation ability due to the formed nanotwins and the decreased induced dislocation proliferation.展开更多
Producing steel requires large amounts of energy to convert iron ores into steel,which often comes from fossil fuels,leading to carbon emissions and other pollutants.Increasing scrap usage emerges as one of the most e...Producing steel requires large amounts of energy to convert iron ores into steel,which often comes from fossil fuels,leading to carbon emissions and other pollutants.Increasing scrap usage emerges as one of the most effective strategies for addressing these issues.However,typical residual elements(Cu,As,Sn,Sb,Bi,etc.)inherited from scrap could significantly influence the mechanical properties of steel.In this work,we investigate the effects of residual elements on the microstructure evolution and mechanical properties of a quenching and partitioning(Q&P)steel by comparing a commercial QP1180 steel(referred to as QP)to the one containing typical residual elements(Cu+As+Sn+Sb+Bi<0.3wt%)(referred to as QP-R).The results demonstrate that in comparison with the QP steel,the residual elements significantly refine the prior austenite grain(9.7μm vs.14.6μm)due to their strong solute drag effect,leading to a higher volume fraction(13.0%vs.11.8%),a smaller size(473 nm vs.790 nm)and a higher average carbon content(1.26 wt%vs.0.99 wt%)of retained austenite in the QP-R steel.As a result,the QP-R steel exhibits a sustained transformation-induced plasticity(TRIP)effect,leading to an enhanced strain hardening effect and a simultaneous improvement of strength and ductility.Grain boundary segregation of residual elements was not observed at prior austenite grain boundaries in the QP-R steel,primarily due to continuous interface migration during austenitization.This study demonstrates that the residual elements with concentrations comparable to that in scrap result in significant microstructural refinement,causing retained austenite with relatively higher stability and thus offering promising mechanical properties and potential applications.展开更多
This study investigates the mechanical properties and microstructure of SS304L stainless steel(SS)fabricated via laser powder bed fusion(LPBF)under controlled oxygen levels(0.2%)at both room and cryogenic temperatures...This study investigates the mechanical properties and microstructure of SS304L stainless steel(SS)fabricated via laser powder bed fusion(LPBF)under controlled oxygen levels(0.2%)at both room and cryogenic temperatures(77 K and 4 K).Experimental results show that the LPBF SS304L exhibits significant improvements in yield strength(YS),with an increase of∼336 MPa at room temperature and up to∼398 MPa at 4 K compared to wrought SS304L.Additionally,the current LPBF SS304L demonstrates an extra∼64 MPa YS strengthening over previous LPBF SS304L data at room temperature.These strength enhancements are primarily attributed to oxide dispersion hardening,promoted by the controlled oxygen level,alongside grain boundary strengthening and dislocation hardening,without significant ductility loss.Furthermore,strain-induced martensitic transformation(SIMT)was absent at room temperature and reduced at cryogenic temperatures compared to wrought SS304L,likely due to high dislocation density and nitrogen-stabilized austenite.A jerk flow observed at 4 K is attributed to adiabatic heating from plastic deformation,consistent with the low thermal conductivity.Finite element simulations reveal a short residence time(0.0137 s)for molten material during the LPBF process,with oxide particles forming predominantly through heterogeneous nucleation at the melt pool surface,and uniformly distributed by Marangoni convection.These findings provide key insights into developing LPBF parameters for enhanced mechanical performance of SS304L for cryogenic and ambient temperature applications.展开更多
Control of the columnar to equiaxed transition(CET)is a major challenge in additively manufacturedβtitanium alloys.In this work,the promotion of CET was successfully achieved through in-situ fabrication of Ti-5Cu(wt....Control of the columnar to equiaxed transition(CET)is a major challenge in additively manufacturedβtitanium alloys.In this work,the promotion of CET was successfully achieved through in-situ fabrication of Ti-5Cu(wt.%)alloys with additions of 5,15,and 25 wt.%Nb using elemental Ti,Cu,and Nb powders by employing laser powder bed fusion(LPBF).The alloy containing 5 wt.%Nb consisted ofαlamellae,Ti2 Cu precipitates,and unmeltedβ-Nb inclusions,whereas the 25 wt.%Nb alloy consisted of equiaxedβgrains,ωprecipitates,and Ti2 Cu precipitates at the grain boundaries.In terms of mechanical proper-ties,despite the presence of Nb inclusions and liquation cracks in the 5 wt.%Nb alloy,it showed a yield strength of 1051±40 MPa and an elongation of 5.2%±1.3%.Both the strength and ductility decreased with increasing Nb content,e.g.,the 25 wt.%Nb alloy exhibited a yield strength of 808±53 MPa and an elongation of 1.6%±0.2%.As the Nb content increased from 5 to 25 wt.%,the Young’s modulus decreased from 110 to 65 GPa.The 25 wt.%Nb alloy showed a high ratio of hardness to Young’s mod-ulus(H/E)and yield pressure(H3/E2).However,due to its brittle nature,the material manifested high wear rates.These findings provide a basis for the future development of novel low-modulus isotropicβ-titanium alloys using LPBF.展开更多
The functionally graded materials(FGMs)are obtained by various processes.Although a few FGMs are obtained naturally,such as oyster,pearl,and bamboo,additive manufacturing(AM),known as 3D printing,is a net-shaped manuf...The functionally graded materials(FGMs)are obtained by various processes.Although a few FGMs are obtained naturally,such as oyster,pearl,and bamboo,additive manufacturing(AM),known as 3D printing,is a net-shaped manufacturing process employed to manufacture complex 3D objects without tools,molds,assembly,and joining.Currently,commercial AM techniques mostly use homogeneous composition with simplified geometric descriptions,employing a single material across the entire component to achieve functional graded additive manufacturing(FGAM),in contrast to multi-material FGAM with heterogeneous structures.FGMs are widely used in various fields due to their mechanical property advantages.Because FGM plays a significant role in the industrial production,the characteristics and mechanical behaviour of FGMs prepared by AM were reviewed.In this review,the research on FGMs and AM over the past 30 years was reviewed,suggesting that future researchers should focus on the application of artificial intelligence and machine learning technologies in industry to optimize the process parameters of different gradient systems.展开更多
Graphene nanoplatelets(GNPs)have attracted tremendous interest due to their unique properties and bonding capabilities.This study focuses on the effect of GNP dispersion on the mechanical,thermal,and morphological beh...Graphene nanoplatelets(GNPs)have attracted tremendous interest due to their unique properties and bonding capabilities.This study focuses on the effect of GNP dispersion on the mechanical,thermal,and morphological behavior of GNP/epoxy nanocomposites.This study aims to understand how the dispersion of GNPs affects the properties of epoxy nanocomposite and to identify the best dispersion approach for improving mechanical performance.A solvent mixing technique that includes mechanical stirring and ultrasonication was used for producing the nanocomposites.Fourier transform infrared spectroscopy was used to investigate the interaction between GNPs and the epoxy matrix.The measurements of density and moisture content were used to confirm that GNPs were successfully incorporated into the nanocomposite.The findings showed that GNPs are successfully dispersed in the epoxy matrix by combining mechanical stirring and ultrasonication in a single step,producing well-dispersed nanocomposites with improved mechanical properties.Particularly,the nanocomposites at a low GNP loading of 0.1 wt%,demonstrate superior mechanical strength,as shown by increased tensile properties,including improved Young's modulus(1.86 GPa),strength(57.31 MPa),and elongation at break(4.98).The nanocomposite with 0.25 wt%GNP loading performs better,according to the viscoelastic analysis and flexural properties(113.18 MPa).Except for the nanocomposite with a 0.5 wt%GNP loading,which has a higher thermal breakdown temperature,the thermal characteristics do not significantly alter.The effective dispersion of GNPs in the epoxy matrix and low agglomeration is confirmed by the morphological characterization.The findings help with filler selection and identifying the best dispersion approach,which improves mechanical performance.The effective integration of GNPs and their interaction with the epoxy matrix provides the doorway for additional investigation and the development of sophisticated nanocomposites.In fields like aerospace,automotive,and electronics where higher mechanical performance and functionality are required,GNPs'improved mechanical properties and successful dispersion present exciting potential.展开更多
This study investigates the impact of welding heat input on weldments of modified 9Cr-1Mo(P91)steel,a high-strength material that requires high-energy welding processes like submerged arc welding.In the as-welded cond...This study investigates the impact of welding heat input on weldments of modified 9Cr-1Mo(P91)steel,a high-strength material that requires high-energy welding processes like submerged arc welding.In the as-welded condition,P91 steel welds primarily consist of untempered martensite,which transforms into tempered martensite during post-weld heat treatment(PWHT).Electron spectro-scopy analysis reveals the presence of M_(23)C_(6) and MX carbonitride precipitates at grain boundaries.Increasing the heat input leads to greater quantities of precipitates in the prior austenite grain boundaries,which can affect material properties.Weldment hardness profiles exhibit modest improvements,while ultimate tensile strength and toughness decrease with higher welding heat input,poten-tially due to the formation of a ferritic phase.Residual stress distributions are noticeably influenced by the welding heat input level.展开更多
Nuclear DNA, which is essential for the transmission of genetic information, is constantly damaged by external stresses and is subsequently repaired by the removal of the damaged region, followed by resynthesis of the...Nuclear DNA, which is essential for the transmission of genetic information, is constantly damaged by external stresses and is subsequently repaired by the removal of the damaged region, followed by resynthesis of the excised region. Accumulation of DNA damage with failure of repair processes leads to fatal diseases such as cancer. Recent studies have suggested that intra- and extra-nuclear environments play essential roles in DNA damage. However, numerous questions regarding the role of the nuclear mechanical environment in DNA damage remain unanswered. In this study, we investigated the effects of cell confluency (cell crowding) on the morphology of cell nuclei, and cytoskeletal structures, and DNA damage in NIH3T3 skin fibroblasts and HeLa cervical cancer cells. Although nuclear downsizing was observed in both NIH3T3 and HeLa cells with cell crowding, intracellular mechanical changes in the two cell types displayed opposite tendencies. Cell crowding in NIH3T3 cells induced reinforcement of actin filament structures, cell stiffening, and nuclear downsizing, resulting in a significant decrease in endogenous DNA damage, whereas cell crowding in HeLa cells caused partial depolymerization of actin filaments and cell softening, inducing endogenous DNA damage. Ultraviolet (UV) radiation significantly increased DNA damage in NIH3T3;however, this response did not change with cell crowding. In contrast, UV radiation did not cause DNA damage in HeLa cells under either sparse or confluent conditions. These results suggested that cell crowding significantly influenced endogenous DNA damage in cells and was quite different in NIH3T3 and HeLa cells. However, cell crowding did not affect the UV-induced DNA damage in either cell type.展开更多
The precise computation of nanoelectromechanical switches’(NEMS)multi-physical interactions requires advanced numerical models and is a crucial part of the development of micro-and nano-systems.This paper presents a ...The precise computation of nanoelectromechanical switches’(NEMS)multi-physical interactions requires advanced numerical models and is a crucial part of the development of micro-and nano-systems.This paper presents a novel compound numerical method to study the instability of a functionally graded(FG)beam-type NEMS,considering surface elasticity effects as stated by Gurtin-Murdoch theory in an Euler-Bernoulli beam.The presented method is based on a combination of the Method of Adjoints(MoA)together with the Bézier-based multistep technique.By utilizing the MoA,a boundary value problem(BVP)is turned into an initial value problem(IVP).The resulting IVP is then solved by employing a cost-efficient multi-step process.It is demonstrated that the mentioned method can arrive at a high level of accuracy.Furthermore,it is revealed that the stability of the presented methodology is far better than that of other common multi-step methods,such as Adams-Bashforth,particularly at higher step sizes.Finally,the effects of axially functionally graded(FG)properties on the pull-in phenomenon and the main design parameters of NEMS,including the detachment length,are inspected.It was shown that the main parameter of design is the modulus of elasticity of the material,as Silver(Ag),which had better mechanical properties,showed almost a 6%improvement compared to aluminum(Al).However,by applying the correct amount of material with sturdier surface parameters,such as Aluminum(Al),at certain points,the nanobeams’functionality can be improved even further by around 1.5%.展开更多
The mechanical behaviour of Titanium-based Fiber Metal Laminates(FMLs)reinforced with Kevlar,Jute and the novel woven(Kevlar+Jute)fiber mat were evaluated through tensile,flexural,Charpy impact,and drop-weight tests.T...The mechanical behaviour of Titanium-based Fiber Metal Laminates(FMLs)reinforced with Kevlar,Jute and the novel woven(Kevlar+Jute)fiber mat were evaluated through tensile,flexural,Charpy impact,and drop-weight tests.The FMLs were fabricated with various stacking configurations(2/1,3/2,4/3,and 5/4)to examine their influence on mechanical properties.Kevlar-reinforced laminates consistently demonstrated superior tensile and flexural strengths,with the highest tensile strength of 772 MPa observed in the 3/2 configuration,attributed to Kevlar's excellent load-bearing capacity.Jute-reinforced laminates exhibited lower performance due to poor bonding and early delamination,while the FMLs reinforced with woven(Kevlar+Jute)fiber mat achieved a balance between mechanical strength and cost-effectiveness by attaining a tensile strength of 718 MPa in the 3/2 configuration.Impact energy absorption results revealed that Kevlar-reinforced FMLs provided the highest energy absorption under Charpy tests,reaching 13.5 J in the 3/2 configuration.The 4/3 configu ration exhibited superior resistance under drop-weight impacts,absorbing 104.7 J of energy.Failure analysis using SEM revealed key mechanisms such as fiber debonding,delamination,and fiber pull-out,with increased severity observed in laminates with a higher number of fiber-epoxy layers,especially in the 5/4 configuration.This study highlights the potential of Kevlar-Jute hybrid fiber-reinforced FMLs for applications requiring high mechanical performance and impact resistance.Future research should explore advanced surface treatments and the environmental durability of these laminates for aerospace and automotive applications.展开更多
In this study,the effect of Tin(Sn)addition on the microstructure,mechanical properties,and wear resistance of pure magnesium(Mg)was examined.Mg-Sn alloys were synthesized using stir casting technique with Sn concentr...In this study,the effect of Tin(Sn)addition on the microstructure,mechanical properties,and wear resistance of pure magnesium(Mg)was examined.Mg-Sn alloys were synthesized using stir casting technique with Sn concentrations of 2.5%,5%,and 7.5% by weight.The specimens were prepared as per ASTM standards for their evaluation.Higher Sn concentrations result in a reduced volume fraction of the eutectic phase,while Mg_(2)Sn precipitates are observed in alloys with 5% or more Sn.Scanning electron microscopy(SEM)analysis of the Mg-7.5wt.%Sn alloy reveals the presence of Mg(OH)_(2),with X-ray diffraction(XRD)confirming an oxygen content of 18% by weight.The addition of Sn minimizes casting porosity,enhancing the quality of the alloys.The findings demonstrate a positive correlation between increasing Sn content and enhanced strength and wear resistance.The Mg-7.5wt.%Sn alloy exhibits significantly enhanced tensile properties attributed to grain refinement and the formation of well-defined grain boundaries compared to alloys with lower Sn additions(2.5% and 5%),although a slight reduction in microhardness is observed.Tribological evaluation indicates reduced wear and friction,suggesting better surface performance.This research underscores the complex interplay between Sn content,microstructural evolution,and the resulting mechanical and tribological performance of Mg-Sn alloys.展开更多
Although the existence of glass–glass interfaces(GGIs)enables improved ductility of metallic nanoglasses(NGs),the excess free volumes at GGIs would cause the NGs to have a much-reduced mechanical strength.Herein,entr...Although the existence of glass–glass interfaces(GGIs)enables improved ductility of metallic nanoglasses(NGs),the excess free volumes at GGIs would cause the NGs to have a much-reduced mechanical strength.Herein,entropy-stabilized GGIs have been in-vestigated in Co–Fe–Ni–Zn–P NGs,which have a large entropy of mixing(1.32R,where R is the gas constant)and could be in a new glass phase,different from that of glassy grain interiors.Through quantitatively determining the activation energy of glass transition sep-arately for the GGIs and glassy grain interiors,the excess free volumes at GGIs are found to be reduced in comparison with those in the glassy grain interiors.The thermodynamically stable GGIs could be associated with increasing entropy of mixing in the GGI regions,which stabilizes the atomic structures of GGIs and enhances the glass forming ability of Co–Fe–Ni–Zn–P NGs.The influences of entropy-stabilized GGIs on the mechanical properties of Co–Fe–Ni–Zn–P NGs are further investigated by nanoindentation and creep tests under tensile deformation,demonstrating that there are notable enhancements in the ductility and mechanical strength for Co–Fe–Ni–Zn–P NGs.This work contributes to an in-depth understanding on the GGI phase in NGs and offers an alternative method for strengthening NGs through GGI engineering.展开更多
A detailed comparative examination of the Weibull and Gaussian statistical methods is offered to analyze the mechanical properties of natural date palm fibers. Tensile tests were conducted on 35 fiber samples using a ...A detailed comparative examination of the Weibull and Gaussian statistical methods is offered to analyze the mechanical properties of natural date palm fibers. Tensile tests were conducted on 35 fiber samples using a universal testing machine to gather data on stress, strain, and Young's modulus. This data was then analyzed through both statistical approaches to evaluate their ability to model important mechanical characteristics, including tensile strength, strain at break, and Young's modulus. The study identifies the strengths and weaknesses of each statistical method when it is applied to natural fibers, emphasizing their suitability for modeling different mechanical properties. The results of this analysis provide important insights that can guide the selection of the most appropriate statistical method, depending on the type of mechanical property being studied and the specific characteristics of the data. This research makes significant contributions to advancing the understanding of natural fiber mechanics and improving the methods used for their characterization.展开更多
Silicon(Si)-based anodes,where Si serves as the active material,have garnered significant attention due to their potential to achieve high electric capacity in lithium-ion batteries(LIBs).A key challenge with Si-based...Silicon(Si)-based anodes,where Si serves as the active material,have garnered significant attention due to their potential to achieve high electric capacity in lithium-ion batteries(LIBs).A key challenge with Si-based anodes is their susceptibility to create in-plane cracks caused by stresses from the manufacturing process and cyclic charging,which ultimately shortens battery life and reduces the overall electrochemical capacity.To address this issue,a refined microstructural design of the active material layer is in pressing need to enhance both the performance and longevity of LIBs.We successfully applied the Oyane failure criterion,which models ductile failure under stress triaxiality,to simulate crack initiation and propagation in the binder matrix containing Si particles in the finite element modeling.Given the non-linear plastic deformation of the binder,this criterion was formulated based on cumulative strain increments.The computational results of microcrack formation within the active material layer under uniaxial tension were then validated by the experimental observations.Furthermore,we developed several models with varied particle arrangements,comparing each simulated crack path to actual microstructural images obtained via scanning electron microscopy.The findings confirm the accuracy of the model,underlying its promising application in optimizing the microstructure of Si-based anodes for enhanced LIB performance and durability.展开更多
In the present study,the mechanical and ballistic properties of friction stir welded(FSW)aluminum alloy(AA5754)samples were investigated,both untreated and cryogenically treated,when impacted by a 7.62 mm armour-pierc...In the present study,the mechanical and ballistic properties of friction stir welded(FSW)aluminum alloy(AA5754)samples were investigated,both untreated and cryogenically treated,when impacted by a 7.62 mm armour-piercing(AP)bullet at an impact velocity of 682±20 m/s.The FSW technique was used to prepare the welded samples for AA5754,with an axial force of 7 kN,a feed rate of 20 mm/min,and a speed of 1200 rpm.The cryogenic treatments performed after welding,including deep cryogenic treatment(DCT)at196℃ and shallow cryogenic treatment(SCT)at80℃,for 6 and 72 h,respectively.The microstructure and mechanical characteristics of cryogenically treated and untreated joints were examined.The cryogenic treatment refined the grain size(1.05 μm)and enhanced the microhardness(93 Hv).Moreover,DCT-FSW significantly improved the tensile strength(13.93%)and impact strength(8.45%)compared to untreated FSW sample.Additionally,in untreated FSW samples,the fracture behaviour varied:the impact fracture mode primarily exhibited ductile failure,while the tensile fracture exhibited a mixed fracture mode.In contrast,the tensile and impact fracture modes of the DCT-FSWwere dominated by a ductile failure mode.The DCT-FSW target demonstrated a lower depth of penetration(DOP)of 31 mm compared to the SCT-FSWand untreated FSW targets.Post-ballistic SEM analysis in the crater region of all three zones revealed the formation of frictional grooves,small cracks,and adiabatic shear bands(ASBs).展开更多
High-entropy perovskite ferroelectric materials have attracted significant attention due to their remarkably low remnant polarizations and narrow hysteresis.Thus,these materials offer high-energy density and efficienc...High-entropy perovskite ferroelectric materials have attracted significant attention due to their remarkably low remnant polarizations and narrow hysteresis.Thus,these materials offer high-energy density and efficiency,making them suitable for energy storage applications.Despite significant advancements in experimental research,understanding of the properties associated with structure remains incomplete.This study aims to study the structural,electric,and mechanical performances at various scales of the high-entropy(Na_(0.2)Bi_(0.2)Ca_(0.2)Sr_(0.2)Ba_(0.2))TiO_(3)(NBCSB)material.The results of first-principles calculations indicated that the pseudo-intralayer distortion was obviously smaller compared to the interlayer distortion.Among the various bonds,Bi-O,Ca-O,and Na-O experienced the greatest displacement.Similarly,the hybridization between O 2p and Ti 3d states with Bi 6p states was particularly strong,affecting both the ferroelectric polarization and relaxor behavior.The NBCSB materials produced using a typical solid-state process demonstrated exceptional performance in energy storage with a recoverable density of 1.53 J·cm^(-3)and a high efficiency of 89%when subjected to a small electric field of 120 kV·cm^(-1).In addition,these ceramics displayed a remarkable hardness of around 7.23 GPa.NBCSB ceramics exhibited exceptional relaxation characteristics with minimal hysteresis and low remanent polarization due to its nanoscale high dynamic polarization configuration with diverse symmetries(rhombohedral,tetragonal,and cubic)resulting from randomly dispersed A-site ions.The excellent mechanical property is related to the dislocation-blocking effect,solid solution strengthening effect,and domain boundary effect.The findings of this study offer a comprehensive and novel perspective on A-site disordered high-entropy relaxor ferroelectric ceramics.展开更多
文摘It is discussed that a tangential force T induces a self-excited vibration in the motion ofspindle blades of a ring spinning frame.Depending on the relative magnitude of the tangentialforce compared with the tangential damping force the motion of blade is either stable orunstable.The chief factors causing the self-excited vibration can also be traced from the charac-ter of the experimental locus.
基金Supported by Key Technologies Research and Development Program of China(Grant No.2022YFC2406004).
文摘In this study,the shell structure of olives in nature was modeled,and a high-porosity bionic olive body-centered cubic structure(BCCO)with reinforcement structures of circular support(BCCR)and triangular support(BCCT)with excellent mechanical properties was designed and prepared using selective laser melting technology.The surface morphology,deformation behavior,and energy absorption of BCCO were compared with those of the equivalent uniform body-centered cubic structure(BCC)and analyzed through quasi-static compression experiments and finite element analysis.The olive-shaped structure showed optimal load resistance when the radius of curvature was equal to the edge length of the lattice structure,and outperformed with a larger curvature than with a smaller curvature.With the added support structure,the energy absorption of the BCCR increased by 144.44%compared with that of the conventional BCC structure.The newly designed olive bionic structure has considerable potential for applications in various fields,such as aerospace and medical devices.
基金supported by the Research Project on Strengthening the Construction of an Important Ecological Security Barrier in Northern China by Higher Education Institutions in the Inner Mongolia Autonomous Region(STAQZX202313)the Inner Mongolia Autonomous Region Education Science‘14th Five-Year Plan’2024 Annual Research Project(NGJGH2024635).
文摘Vacancy defects,as fundamental disruptions in metallic lattices,play an important role in shaping the mechanical and electronic properties of aluminum crystals.However,the influence of vacancy position under coupled thermomechanical fields remains insufficiently understood.In this study,transmission and scanning electron microscopy were employed to observe dislocation structures and grain boundary heterogeneities in processed aluminum alloys,suggesting stress concentrations and microstructural inhomogeneities associated with vacancy accumulation.To complement these observations,first-principles calculations and molecular dynamics simulations were conducted for seven single-vacancy configurations in face-centered cubic aluminum.The stress response,total energy,density of states(DOS),and differential charge density were examined under varying compressive strain(ε=0–0.1)and temperature(0–600 K).The results indicate that face-centered vacancies tend to reduce mechanical strength and perturb electronic states near the Fermi level,whereas corner and edge vacancies appear to have weaker effects.Elevated temperatures may partially restore electronic uniformity through thermal excitation.Overall,these findings suggest that vacancy position exerts a critical but position-dependent influence on coupled structure-property relationships,offering theoretical insights and preliminary experimental support for defect-engineered aluminum alloy design.
文摘This study presents a framework involving statistical modeling and machine learning to accurately predict and optimize the mechanical and damping properties of hybrid granite-epoxy(G-E)composites reinforced with cast iron(CI)filler particles.Hybrid G-E composite with added cast iron(CI)filler particles enhances stiffness,strength,and vibration damping,offering enhanced performance for vibration-sensitive engineering applications.Unlike conventional approaches,this work simultaneously employs Artificial Neural Networks(ANN)for highaccuracy property prediction and Response Surface Methodology(RSM)for in-depth analysis of factor interactions and optimization.A total of 24 experimental test data sets of varying input factors(granite weight%,epoxy weight%,and CI filler weight%)were utilized to train and test the prediction models using an ANN approach and further analyze the interaction effects using RSM.Mechanical properties,including tensile,compressive,and flexural strength,elastic modulus,density and damping properties measured under various testing conditions,were set as output parameters for prediction.This study analyzed and optimized the performance of the ANN model using Bayesian Regularization and Levenberg-Marquardt algorithms to identify the best performing number of neurons in the hidden layer for achieving the highest prediction accuracy.The proposed ANN framework achieved an exceptional average determination coefficient(R2)exceeding 99%,with Bayesian Regularization demonstrating remarkable stability in the 22-neuron range and minimal variation across all properties.RSM and ANN form a powerful framework for predicting and optimizing hybrid G-E composite properties,enabling efficient design for vibration-critical applications with reduced experimental effort and performance optimization.
基金financially supported by the Fundamental Research Funds for the Central Universities,China(No.21624408)the Guangdong Basic and Applied Basic Research Foundation,China(Nos.2023A1515012850,2024A1515010416)+2 种基金Guangzhou Science and Technology Planning Project,China(No.2024A04J9966)the National Natural Science Foundation of China(Nos.52271132,52004101)the Key Laboratory of Advanced Materials of Yunnan Province,China(No.2024KF02)。
文摘To exploit the combined strengthening effects of nanotwins and carbon nanotubes(CNTs)in Cu matrix composites,the nanotwins with a width ranging from 3 to 30 nm were incorporated into the CNTs-reinforced Cu matrix composites using cryogenic rolling and optimizing the initial particle size of the raw Cu powders.The formation of nanotwins in the Cu matrix composite reinforced by only 0.2 wt.%CNTs is accompanied by the increased dislocation density and refined Cu grain size,resulting in much better strength−ductility synergy than the referenced composite without significant nanotwins formation.The analysis of strengthening and toughening mechanisms demonstrates that the strength increment mainly derives from grain refinement strengthening,dislocation strengthening,and nanotwin strengthening.The strength increment from the contribution of the nanotwins accounts for 19.9%of the overall strength increment for the composite.Meanwhile,the retention of good tensile ductility can be reasonably explained by the increased dislocation accommodation ability due to the formed nanotwins and the decreased induced dislocation proliferation.
基金financially supported by the National Natural Science Foundation of China(Nos.52293395 and 52293393)the Xiongan Science and Technology Innovation Talent Project of MOST,China(No.2022XACX0500).
文摘Producing steel requires large amounts of energy to convert iron ores into steel,which often comes from fossil fuels,leading to carbon emissions and other pollutants.Increasing scrap usage emerges as one of the most effective strategies for addressing these issues.However,typical residual elements(Cu,As,Sn,Sb,Bi,etc.)inherited from scrap could significantly influence the mechanical properties of steel.In this work,we investigate the effects of residual elements on the microstructure evolution and mechanical properties of a quenching and partitioning(Q&P)steel by comparing a commercial QP1180 steel(referred to as QP)to the one containing typical residual elements(Cu+As+Sn+Sb+Bi<0.3wt%)(referred to as QP-R).The results demonstrate that in comparison with the QP steel,the residual elements significantly refine the prior austenite grain(9.7μm vs.14.6μm)due to their strong solute drag effect,leading to a higher volume fraction(13.0%vs.11.8%),a smaller size(473 nm vs.790 nm)and a higher average carbon content(1.26 wt%vs.0.99 wt%)of retained austenite in the QP-R steel.As a result,the QP-R steel exhibits a sustained transformation-induced plasticity(TRIP)effect,leading to an enhanced strain hardening effect and a simultaneous improvement of strength and ductility.Grain boundary segregation of residual elements was not observed at prior austenite grain boundaries in the QP-R steel,primarily due to continuous interface migration during austenitization.This study demonstrates that the residual elements with concentrations comparable to that in scrap result in significant microstructural refinement,causing retained austenite with relatively higher stability and thus offering promising mechanical properties and potential applications.
基金supported financially by Fundamental Research Program of the Korea Institute of Materials Science(No.PNKA320)the Korea Institute of Energy Technology Evaluation and Planning(KETEP)and the Ministry of Trade,Industry&Energy(MOTIE)of the Republic of Korea(RS-2024-00435433).
文摘This study investigates the mechanical properties and microstructure of SS304L stainless steel(SS)fabricated via laser powder bed fusion(LPBF)under controlled oxygen levels(0.2%)at both room and cryogenic temperatures(77 K and 4 K).Experimental results show that the LPBF SS304L exhibits significant improvements in yield strength(YS),with an increase of∼336 MPa at room temperature and up to∼398 MPa at 4 K compared to wrought SS304L.Additionally,the current LPBF SS304L demonstrates an extra∼64 MPa YS strengthening over previous LPBF SS304L data at room temperature.These strength enhancements are primarily attributed to oxide dispersion hardening,promoted by the controlled oxygen level,alongside grain boundary strengthening and dislocation hardening,without significant ductility loss.Furthermore,strain-induced martensitic transformation(SIMT)was absent at room temperature and reduced at cryogenic temperatures compared to wrought SS304L,likely due to high dislocation density and nitrogen-stabilized austenite.A jerk flow observed at 4 K is attributed to adiabatic heating from plastic deformation,consistent with the low thermal conductivity.Finite element simulations reveal a short residence time(0.0137 s)for molten material during the LPBF process,with oxide particles forming predominantly through heterogeneous nucleation at the melt pool surface,and uniformly distributed by Marangoni convection.These findings provide key insights into developing LPBF parameters for enhanced mechanical performance of SS304L for cryogenic and ambient temperature applications.
基金the National Natural Science Foun-dation of China(Grant Nos.12374022,U23A20540)the Natu-ral Science Foundation of Hunan Province for Distinguished Young Scholars(Grant No.2023JJ10075)+3 种基金the China Postdoctoral Science Foundation(Grant Nos.GZC20241335,2024MD753962)the YueLuShan Center Industrial Innovation(Grant No.2024YCII0106)the Scientific and Technological Project of Yunnan Precious Met-als Laboratory(Grant No.YPML-2023050247)the Central South University Research Programme of Advanced Interdisci-plinary Studies(Grant No.2023QYJC039).
文摘Control of the columnar to equiaxed transition(CET)is a major challenge in additively manufacturedβtitanium alloys.In this work,the promotion of CET was successfully achieved through in-situ fabrication of Ti-5Cu(wt.%)alloys with additions of 5,15,and 25 wt.%Nb using elemental Ti,Cu,and Nb powders by employing laser powder bed fusion(LPBF).The alloy containing 5 wt.%Nb consisted ofαlamellae,Ti2 Cu precipitates,and unmeltedβ-Nb inclusions,whereas the 25 wt.%Nb alloy consisted of equiaxedβgrains,ωprecipitates,and Ti2 Cu precipitates at the grain boundaries.In terms of mechanical proper-ties,despite the presence of Nb inclusions and liquation cracks in the 5 wt.%Nb alloy,it showed a yield strength of 1051±40 MPa and an elongation of 5.2%±1.3%.Both the strength and ductility decreased with increasing Nb content,e.g.,the 25 wt.%Nb alloy exhibited a yield strength of 808±53 MPa and an elongation of 1.6%±0.2%.As the Nb content increased from 5 to 25 wt.%,the Young’s modulus decreased from 110 to 65 GPa.The 25 wt.%Nb alloy showed a high ratio of hardness to Young’s mod-ulus(H/E)and yield pressure(H3/E2).However,due to its brittle nature,the material manifested high wear rates.These findings provide a basis for the future development of novel low-modulus isotropicβ-titanium alloys using LPBF.
文摘The functionally graded materials(FGMs)are obtained by various processes.Although a few FGMs are obtained naturally,such as oyster,pearl,and bamboo,additive manufacturing(AM),known as 3D printing,is a net-shaped manufacturing process employed to manufacture complex 3D objects without tools,molds,assembly,and joining.Currently,commercial AM techniques mostly use homogeneous composition with simplified geometric descriptions,employing a single material across the entire component to achieve functional graded additive manufacturing(FGAM),in contrast to multi-material FGAM with heterogeneous structures.FGMs are widely used in various fields due to their mechanical property advantages.Because FGM plays a significant role in the industrial production,the characteristics and mechanical behaviour of FGMs prepared by AM were reviewed.In this review,the research on FGMs and AM over the past 30 years was reviewed,suggesting that future researchers should focus on the application of artificial intelligence and machine learning technologies in industry to optimize the process parameters of different gradient systems.
基金the Puncak RM for the project under the grant 6733204-13069 to carry out the experiments。
文摘Graphene nanoplatelets(GNPs)have attracted tremendous interest due to their unique properties and bonding capabilities.This study focuses on the effect of GNP dispersion on the mechanical,thermal,and morphological behavior of GNP/epoxy nanocomposites.This study aims to understand how the dispersion of GNPs affects the properties of epoxy nanocomposite and to identify the best dispersion approach for improving mechanical performance.A solvent mixing technique that includes mechanical stirring and ultrasonication was used for producing the nanocomposites.Fourier transform infrared spectroscopy was used to investigate the interaction between GNPs and the epoxy matrix.The measurements of density and moisture content were used to confirm that GNPs were successfully incorporated into the nanocomposite.The findings showed that GNPs are successfully dispersed in the epoxy matrix by combining mechanical stirring and ultrasonication in a single step,producing well-dispersed nanocomposites with improved mechanical properties.Particularly,the nanocomposites at a low GNP loading of 0.1 wt%,demonstrate superior mechanical strength,as shown by increased tensile properties,including improved Young's modulus(1.86 GPa),strength(57.31 MPa),and elongation at break(4.98).The nanocomposite with 0.25 wt%GNP loading performs better,according to the viscoelastic analysis and flexural properties(113.18 MPa).Except for the nanocomposite with a 0.5 wt%GNP loading,which has a higher thermal breakdown temperature,the thermal characteristics do not significantly alter.The effective dispersion of GNPs in the epoxy matrix and low agglomeration is confirmed by the morphological characterization.The findings help with filler selection and identifying the best dispersion approach,which improves mechanical performance.The effective integration of GNPs and their interaction with the epoxy matrix provides the doorway for additional investigation and the development of sophisticated nanocomposites.In fields like aerospace,automotive,and electronics where higher mechanical performance and functionality are required,GNPs'improved mechanical properties and successful dispersion present exciting potential.
文摘This study investigates the impact of welding heat input on weldments of modified 9Cr-1Mo(P91)steel,a high-strength material that requires high-energy welding processes like submerged arc welding.In the as-welded condition,P91 steel welds primarily consist of untempered martensite,which transforms into tempered martensite during post-weld heat treatment(PWHT).Electron spectro-scopy analysis reveals the presence of M_(23)C_(6) and MX carbonitride precipitates at grain boundaries.Increasing the heat input leads to greater quantities of precipitates in the prior austenite grain boundaries,which can affect material properties.Weldment hardness profiles exhibit modest improvements,while ultimate tensile strength and toughness decrease with higher welding heat input,poten-tially due to the formation of a ferritic phase.Residual stress distributions are noticeably influenced by the welding heat input level.
文摘Nuclear DNA, which is essential for the transmission of genetic information, is constantly damaged by external stresses and is subsequently repaired by the removal of the damaged region, followed by resynthesis of the excised region. Accumulation of DNA damage with failure of repair processes leads to fatal diseases such as cancer. Recent studies have suggested that intra- and extra-nuclear environments play essential roles in DNA damage. However, numerous questions regarding the role of the nuclear mechanical environment in DNA damage remain unanswered. In this study, we investigated the effects of cell confluency (cell crowding) on the morphology of cell nuclei, and cytoskeletal structures, and DNA damage in NIH3T3 skin fibroblasts and HeLa cervical cancer cells. Although nuclear downsizing was observed in both NIH3T3 and HeLa cells with cell crowding, intracellular mechanical changes in the two cell types displayed opposite tendencies. Cell crowding in NIH3T3 cells induced reinforcement of actin filament structures, cell stiffening, and nuclear downsizing, resulting in a significant decrease in endogenous DNA damage, whereas cell crowding in HeLa cells caused partial depolymerization of actin filaments and cell softening, inducing endogenous DNA damage. Ultraviolet (UV) radiation significantly increased DNA damage in NIH3T3;however, this response did not change with cell crowding. In contrast, UV radiation did not cause DNA damage in HeLa cells under either sparse or confluent conditions. These results suggested that cell crowding significantly influenced endogenous DNA damage in cells and was quite different in NIH3T3 and HeLa cells. However, cell crowding did not affect the UV-induced DNA damage in either cell type.
文摘The precise computation of nanoelectromechanical switches’(NEMS)multi-physical interactions requires advanced numerical models and is a crucial part of the development of micro-and nano-systems.This paper presents a novel compound numerical method to study the instability of a functionally graded(FG)beam-type NEMS,considering surface elasticity effects as stated by Gurtin-Murdoch theory in an Euler-Bernoulli beam.The presented method is based on a combination of the Method of Adjoints(MoA)together with the Bézier-based multistep technique.By utilizing the MoA,a boundary value problem(BVP)is turned into an initial value problem(IVP).The resulting IVP is then solved by employing a cost-efficient multi-step process.It is demonstrated that the mentioned method can arrive at a high level of accuracy.Furthermore,it is revealed that the stability of the presented methodology is far better than that of other common multi-step methods,such as Adams-Bashforth,particularly at higher step sizes.Finally,the effects of axially functionally graded(FG)properties on the pull-in phenomenon and the main design parameters of NEMS,including the detachment length,are inspected.It was shown that the main parameter of design is the modulus of elasticity of the material,as Silver(Ag),which had better mechanical properties,showed almost a 6%improvement compared to aluminum(Al).However,by applying the correct amount of material with sturdier surface parameters,such as Aluminum(Al),at certain points,the nanobeams’functionality can be improved even further by around 1.5%.
基金the aid of Research and Development Fund-Seed Money provided by Vel Tech Rangarajan Dr.Sagunthala R&D Institute of Science and Technology。
文摘The mechanical behaviour of Titanium-based Fiber Metal Laminates(FMLs)reinforced with Kevlar,Jute and the novel woven(Kevlar+Jute)fiber mat were evaluated through tensile,flexural,Charpy impact,and drop-weight tests.The FMLs were fabricated with various stacking configurations(2/1,3/2,4/3,and 5/4)to examine their influence on mechanical properties.Kevlar-reinforced laminates consistently demonstrated superior tensile and flexural strengths,with the highest tensile strength of 772 MPa observed in the 3/2 configuration,attributed to Kevlar's excellent load-bearing capacity.Jute-reinforced laminates exhibited lower performance due to poor bonding and early delamination,while the FMLs reinforced with woven(Kevlar+Jute)fiber mat achieved a balance between mechanical strength and cost-effectiveness by attaining a tensile strength of 718 MPa in the 3/2 configuration.Impact energy absorption results revealed that Kevlar-reinforced FMLs provided the highest energy absorption under Charpy tests,reaching 13.5 J in the 3/2 configuration.The 4/3 configu ration exhibited superior resistance under drop-weight impacts,absorbing 104.7 J of energy.Failure analysis using SEM revealed key mechanisms such as fiber debonding,delamination,and fiber pull-out,with increased severity observed in laminates with a higher number of fiber-epoxy layers,especially in the 5/4 configuration.This study highlights the potential of Kevlar-Jute hybrid fiber-reinforced FMLs for applications requiring high mechanical performance and impact resistance.Future research should explore advanced surface treatments and the environmental durability of these laminates for aerospace and automotive applications.
文摘In this study,the effect of Tin(Sn)addition on the microstructure,mechanical properties,and wear resistance of pure magnesium(Mg)was examined.Mg-Sn alloys were synthesized using stir casting technique with Sn concentrations of 2.5%,5%,and 7.5% by weight.The specimens were prepared as per ASTM standards for their evaluation.Higher Sn concentrations result in a reduced volume fraction of the eutectic phase,while Mg_(2)Sn precipitates are observed in alloys with 5% or more Sn.Scanning electron microscopy(SEM)analysis of the Mg-7.5wt.%Sn alloy reveals the presence of Mg(OH)_(2),with X-ray diffraction(XRD)confirming an oxygen content of 18% by weight.The addition of Sn minimizes casting porosity,enhancing the quality of the alloys.The findings demonstrate a positive correlation between increasing Sn content and enhanced strength and wear resistance.The Mg-7.5wt.%Sn alloy exhibits significantly enhanced tensile properties attributed to grain refinement and the formation of well-defined grain boundaries compared to alloys with lower Sn additions(2.5% and 5%),although a slight reduction in microhardness is observed.Tribological evaluation indicates reduced wear and friction,suggesting better surface performance.This research underscores the complex interplay between Sn content,microstructural evolution,and the resulting mechanical and tribological performance of Mg-Sn alloys.
基金This work has been endorsed by the Chengdu Guangming Paite Precious Metal Co.,Ltd.,the CDGM Glass Co.,Ltd.,China,and the Research Grants Council of Hong Kong Special Administrative Region,China(No.15233823).
文摘Although the existence of glass–glass interfaces(GGIs)enables improved ductility of metallic nanoglasses(NGs),the excess free volumes at GGIs would cause the NGs to have a much-reduced mechanical strength.Herein,entropy-stabilized GGIs have been in-vestigated in Co–Fe–Ni–Zn–P NGs,which have a large entropy of mixing(1.32R,where R is the gas constant)and could be in a new glass phase,different from that of glassy grain interiors.Through quantitatively determining the activation energy of glass transition sep-arately for the GGIs and glassy grain interiors,the excess free volumes at GGIs are found to be reduced in comparison with those in the glassy grain interiors.The thermodynamically stable GGIs could be associated with increasing entropy of mixing in the GGI regions,which stabilizes the atomic structures of GGIs and enhances the glass forming ability of Co–Fe–Ni–Zn–P NGs.The influences of entropy-stabilized GGIs on the mechanical properties of Co–Fe–Ni–Zn–P NGs are further investigated by nanoindentation and creep tests under tensile deformation,demonstrating that there are notable enhancements in the ductility and mechanical strength for Co–Fe–Ni–Zn–P NGs.This work contributes to an in-depth understanding on the GGI phase in NGs and offers an alternative method for strengthening NGs through GGI engineering.
文摘A detailed comparative examination of the Weibull and Gaussian statistical methods is offered to analyze the mechanical properties of natural date palm fibers. Tensile tests were conducted on 35 fiber samples using a universal testing machine to gather data on stress, strain, and Young's modulus. This data was then analyzed through both statistical approaches to evaluate their ability to model important mechanical characteristics, including tensile strength, strain at break, and Young's modulus. The study identifies the strengths and weaknesses of each statistical method when it is applied to natural fibers, emphasizing their suitability for modeling different mechanical properties. The results of this analysis provide important insights that can guide the selection of the most appropriate statistical method, depending on the type of mechanical property being studied and the specific characteristics of the data. This research makes significant contributions to advancing the understanding of natural fiber mechanics and improving the methods used for their characterization.
基金support of JSPS KAKENHI(Grant No.21H01217)from the Japan Society for the Promotion of Science.
文摘Silicon(Si)-based anodes,where Si serves as the active material,have garnered significant attention due to their potential to achieve high electric capacity in lithium-ion batteries(LIBs).A key challenge with Si-based anodes is their susceptibility to create in-plane cracks caused by stresses from the manufacturing process and cyclic charging,which ultimately shortens battery life and reduces the overall electrochemical capacity.To address this issue,a refined microstructural design of the active material layer is in pressing need to enhance both the performance and longevity of LIBs.We successfully applied the Oyane failure criterion,which models ductile failure under stress triaxiality,to simulate crack initiation and propagation in the binder matrix containing Si particles in the finite element modeling.Given the non-linear plastic deformation of the binder,this criterion was formulated based on cumulative strain increments.The computational results of microcrack formation within the active material layer under uniaxial tension were then validated by the experimental observations.Furthermore,we developed several models with varied particle arrangements,comparing each simulated crack path to actual microstructural images obtained via scanning electron microscopy.The findings confirm the accuracy of the model,underlying its promising application in optimizing the microstructure of Si-based anodes for enhanced LIB performance and durability.
文摘In the present study,the mechanical and ballistic properties of friction stir welded(FSW)aluminum alloy(AA5754)samples were investigated,both untreated and cryogenically treated,when impacted by a 7.62 mm armour-piercing(AP)bullet at an impact velocity of 682±20 m/s.The FSW technique was used to prepare the welded samples for AA5754,with an axial force of 7 kN,a feed rate of 20 mm/min,and a speed of 1200 rpm.The cryogenic treatments performed after welding,including deep cryogenic treatment(DCT)at196℃ and shallow cryogenic treatment(SCT)at80℃,for 6 and 72 h,respectively.The microstructure and mechanical characteristics of cryogenically treated and untreated joints were examined.The cryogenic treatment refined the grain size(1.05 μm)and enhanced the microhardness(93 Hv).Moreover,DCT-FSW significantly improved the tensile strength(13.93%)and impact strength(8.45%)compared to untreated FSW sample.Additionally,in untreated FSW samples,the fracture behaviour varied:the impact fracture mode primarily exhibited ductile failure,while the tensile fracture exhibited a mixed fracture mode.In contrast,the tensile and impact fracture modes of the DCT-FSWwere dominated by a ductile failure mode.The DCT-FSW target demonstrated a lower depth of penetration(DOP)of 31 mm compared to the SCT-FSWand untreated FSW targets.Post-ballistic SEM analysis in the crater region of all three zones revealed the formation of frictional grooves,small cracks,and adiabatic shear bands(ASBs).
基金supported by Guangdong Basic and Applied Basic Research Foundation and Project of General Colleges and Universities in Guangdong Province(Nos.2022A1515140002 and 2019GKQNCX127)the Special Innovation Projects of Department of Education’s of Guangdong Provincial(No.2018KTSCX220)+4 种基金the International Cooperation Project of Guangdong Province(No.2019A050510049)the Program for Innovative Research Team of Guangdong Province&Huizhou University(IRTHZU)Indigenous Innovation’s Capability Development Program of Huizhou University(No.HZU202014)the Open Project Program of Guangdong Provincial Key Laboratory of Electronic Functional Materials and Devices,Huizhou University(No.EFMD2022015M)the National Natural Science Foundation of China(No.12102068).
文摘High-entropy perovskite ferroelectric materials have attracted significant attention due to their remarkably low remnant polarizations and narrow hysteresis.Thus,these materials offer high-energy density and efficiency,making them suitable for energy storage applications.Despite significant advancements in experimental research,understanding of the properties associated with structure remains incomplete.This study aims to study the structural,electric,and mechanical performances at various scales of the high-entropy(Na_(0.2)Bi_(0.2)Ca_(0.2)Sr_(0.2)Ba_(0.2))TiO_(3)(NBCSB)material.The results of first-principles calculations indicated that the pseudo-intralayer distortion was obviously smaller compared to the interlayer distortion.Among the various bonds,Bi-O,Ca-O,and Na-O experienced the greatest displacement.Similarly,the hybridization between O 2p and Ti 3d states with Bi 6p states was particularly strong,affecting both the ferroelectric polarization and relaxor behavior.The NBCSB materials produced using a typical solid-state process demonstrated exceptional performance in energy storage with a recoverable density of 1.53 J·cm^(-3)and a high efficiency of 89%when subjected to a small electric field of 120 kV·cm^(-1).In addition,these ceramics displayed a remarkable hardness of around 7.23 GPa.NBCSB ceramics exhibited exceptional relaxation characteristics with minimal hysteresis and low remanent polarization due to its nanoscale high dynamic polarization configuration with diverse symmetries(rhombohedral,tetragonal,and cubic)resulting from randomly dispersed A-site ions.The excellent mechanical property is related to the dislocation-blocking effect,solid solution strengthening effect,and domain boundary effect.The findings of this study offer a comprehensive and novel perspective on A-site disordered high-entropy relaxor ferroelectric ceramics.
