A newly proposed rapid fracture test in four-point bending was used to evaluate the effect of tempering on the hydrogen embrittlement(HE)susceptibility of an AISI 4135 steel,where it was tempered to four different str...A newly proposed rapid fracture test in four-point bending was used to evaluate the effect of tempering on the hydrogen embrittlement(HE)susceptibility of an AISI 4135 steel,where it was tempered to four different strength(or hardness)levels.It was observed that HE susceptibility increases with the increase in hardness.It was shown that there will be minimal impact of hydrogen(H)on the fracture of materials with hardness 37 HRC and below,even if they are completely saturated with H.On the other hand,H will have similar detrimental effect on fracture properties of quench and tempered(Q and T)steels having hardness higher than 45 HRC.Ductile to brittle transition behavior was observed for a critical hardness(or strength)range as well as for a critical concentration level of H.Additionally,a critical H concentration was observed to exist for each of the strength levels.Fractography was performed in addition to microstructural characterization using transmission electron microscopy(TEM).A very good correlation was observed between the fast fracture test results and fractography.The fast fracture test was further compared with a conventional incremental step load(ISL)test for the evaluation of HE susceptibility.The ISL test results and fracture surface characteristics corroborate very well with the observations from the fast fracture test.This study successfully establishes the fast fracture test as a novel technique to study HE susceptibility and mechanism(s).展开更多
The corrosion failure mechanism of M152 was studied using the neutral salt-spray test to better understand the corrosion behavior of 1Cr12Ni3Mo2VN（M152）, provide a basis for the optimization of material selection, a...The corrosion failure mechanism of M152 was studied using the neutral salt-spray test to better understand the corrosion behavior of 1Cr12Ni3Mo2VN（M152）, provide a basis for the optimization of material selection, and prevent the occurrence of failure. Moreover, the mechanism was investigated using the mass loss method, polarization curves, electrochemical impedance spectroscopy（EIS）, stereology microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy（EDS）. The results show that M152 steel suffers severe corrosion, especially pitting corrosion, in a high-salt-spray environment. In the early stage of the experiment, the color of the corrosion products was mainly orange. The products then gradually evolved into a dense, brown substance, which coincided with a decrease of corrosion rate. Correspondingly, the EIS spectrum of M152 in the late test also exhibited three time constants and presented Warburg impedance at low frequencies.展开更多
With the continuous development of today's science and technology,orthopedic research has also achieved continuous updates in materials and machinery.In this case,the mechanics testing technology of orthopedics al...With the continuous development of today's science and technology,orthopedic research has also achieved continuous updates in materials and machinery.In this case,the mechanics testing technology of orthopedics also needs to be further updated and developed,so that it can effectively meet the requirement for today's orthopedic mechanical testing.Based on this,this article analyzes several advanced orthopedic mechanics testing techniques.It is hoped that this analysis can provide a reference for the good application and development of orthopedic mechanics testing technology.展开更多
Debris flow is one of the major secondary mountain hazards following the earthquake. This study explores the dynamic initiation mechanism of debris flows based on the strength reduction of soils through static and dyn...Debris flow is one of the major secondary mountain hazards following the earthquake. This study explores the dynamic initiation mechanism of debris flows based on the strength reduction of soils through static and dynamic triaxial tests. A series of static and dynamic triaxial tests were conducted on samples in the lab. The samples were prepared according to different grain size distribution, degree of saturation and earthquake magnitudes. The relations of dynamic shear strength, degree of saturation, and number of cycles are summarized through analyzing experimental results. The findings show that the gravelly soil with a wide and continuous gradation has a critical degree of saturation of approximately 87%, above which debris flows will be triggered by rainfall, while the debris flow will be triggered at a critical degree of saturation of about 73% under the effect of rainfall and earthquake(M>6.5). Debris flow initiation is developed in the humidification process, and the earthquake provides energy for triggering debris flows. Debris flows are more likely to be triggered at the relatively low saturation under dynamic loading than under static loading. The resistance of debris flow triggering relies more on internal frication angle than soil cohesion under the effect of rainfall and earthquake. The conclusions provide an experimental analysis method for dynamic initiation mechanism of debris flows.展开更多
Bell tests with entangled light have been performed many times in many ways using linear polarizers, but the same tests have never been done with a circular polarizer. Until recently there has never been a true circul...Bell tests with entangled light have been performed many times in many ways using linear polarizers, but the same tests have never been done with a circular polarizer. Until recently there has never been a true circular polarization beamsplitter—an optical component that separates light directly into left and right handed polarizations. Using a true circular polarization beamsplitter based on birefringent gratings, entangled light has been analyzed with unexpected results.展开更多
The aim of this study is to address the issues associated with traditional magnetorheological fluid(MRF)dampers,such as insufficient damping force after power failure and susceptibility to settlement.In order to achie...The aim of this study is to address the issues associated with traditional magnetorheological fluid(MRF)dampers,such as insufficient damping force after power failure and susceptibility to settlement.In order to achieve this,a bidirectional adjustable MRF damper was designed and developed.Magnetic field simulation analysis was conducted on the damper,along with simulation analysis on its dynamic characteristics.The dynamic characteristics were ultimately validated through experimental testing on the material testing machine,thereby corroborating the theoretical simulation results.Concurrently,this process generated valuable test data for subsequent implementation of the semi-active vibration control system.The simulation and test results demonstrate that the integrated permanent magnet effectively accomplishes bidirectional regulation.The magnetic induction intensity of the damping channel is 0.2 T in the absence of current,increases to 0.5 T when a maximum forward current of 4 A is applied,and becomes 0 T when a maximum reverse current of 3.8 A is applied.When the excitation amplitude is 8 mm and the frequency is 2 Hz,with the applied currents varying,the maximum damping force reaches 8 kN,while the minimum damping force measures at 511 N.Additionally,at zero current,the damping force stands at 2 kN,which aligns closely with simulation results.The present paper can serve as a valuable reference for the design and research of semi-active MRF dampers.展开更多
The limited metal-polymer interlaminar property is a significant obstacle to the advancement of Ti/Carbon Fiber(CF)/Polyether Ether Ketone(PEEK)hybrid laminates.We report for the first time a novel method by utilizing...The limited metal-polymer interlaminar property is a significant obstacle to the advancement of Ti/Carbon Fiber(CF)/Polyether Ether Ketone(PEEK)hybrid laminates.We report for the first time a novel method by utilizing the mussel-inspired Polydopamine(PDA)to introduce a strong chemical-physical bonding between titanium and PEEK.The enhanced Fiber-Metal Laminate(FML)exhibits a significant 48.82%enhancement in Interlaminar Shear Strength(ILSS).In addition,it alters the failure mode of the FML from single metal-resin interlaminar delamination to a multi-mechanism,including debonding,delamination of different composite layers,leading to a 28.57%improvement in maximum displacement.展开更多
In this study, to meet the development and application requirements for high-strength and hightoughness energetic structural materials, a representative volume element of a TA15 matrix embedded with a TaZrNb sphere wa...In this study, to meet the development and application requirements for high-strength and hightoughness energetic structural materials, a representative volume element of a TA15 matrix embedded with a TaZrNb sphere was designed and fabricated via diffusion bonding. The mechanisms of the microstructural evolution of the TaZrNb/TA15 interface were investigated via SEM, EBSD, EDS, and XRD.Interface mechanical property tests and in-situ tensile tests were conducted on the sphere-containing structure, and an equivalent tensile-strength model was established for the structure. The results revealed that the TA15 titanium alloy and joint had high density and no pores or cracks. The thickness of the planar joint was approximately 50-60 μm. The average tensile and shear strengths were 767 MPa and 608 MPa, respectively. The thickness of the spherical joint was approximately 60 μm. The Zr and Nb elements in the joint diffused uniformly and formed strong bonds with Ti without forming intermetallic compounds. The interface exhibited submicron grain refinement and a concave-convex interlocking structure. The tensile fracture surface primarily exhibited intergranular fracture combined with some transgranular fracture, which constituted a quasi-brittle fracture mode. The shear fracture surface exhibited brittle fracture with regular arrangements of furrows. Internal fracture occurred along the spherical interface, as revealed by advanced in-situ X-ray microcomputed tomography. The experimental results agreed well with the theoretical predictions, indicating that the high-strength interface contributes to the overall strength and toughness of the sphere-containing structure.展开更多
The small punch test technique facilitates the convenient acquisition of the mechanical properties of in-service equipment materials and the assessment of their remaining service life through sampling.However,the weld...The small punch test technique facilitates the convenient acquisition of the mechanical properties of in-service equipment materials and the assessment of their remaining service life through sampling.However,the weldability of components with thin walls after small punch sampling,such as ethylene cracking furnace tubes,requires further investigation.Therefore,the weldability of in-service ethylene cracking furnace tubes following small punch sampling was investigated through nondestructive testing,microstructural characterization,and mechanical testing.Additionally,the impact of small punch sampling size and residual stress on the creep performance of the specimens was studied using an improved ductility exhaustion model.The results indicate that both the surface and interior of the weld repair areas on new furnace tubes and service-exposed furnace tubes after small-punch sampling are defect-free,exhibiting good weld quality.The strength of the specimens after weld repair was higher than that before sampling,whereas toughness decreased.Weld repair following small punch sampling of furnace tubes is both feasible and necessary.Furthermore,a linear relationship was observed between specimen thickness,diameter,and creep fracture time.The residual stress of welding affects the creep performance of the specimen under different stresses.展开更多
Characterizing the architecture of tree root systems is essential to advance the development of root-inspired anchorage in engineered systems.This study explores the structural root architectures of orchard trees to u...Characterizing the architecture of tree root systems is essential to advance the development of root-inspired anchorage in engineered systems.This study explores the structural root architectures of orchard trees to understand the interplays between the mechanical behavior of roots and the root architecture.Full three-dimensional(3D)models of natural tree root systems,Lovell,Marianna,and Myrobalan,that were extracted from the ground by vertical pullout are reconstructed through photogrammetry and later skeletonized as nodes and root branch segments.Combined analyses of the full 3D models and skeletonized models enable a detailed examination of basic bulk properties and quantification of architectural parameters.While the root segments are divided into three categories,trunk root,main lateral root,and remaining roots,the patterns in branching and diameter distributions show significant differences between the trunk and main laterals versus the remaining lateral roots.In general,the branching angle decreases over the sequence of bifurcations.The main lateral roots near the trunk show significant spreading while the lateral roots near the ends grow roughly parallel to the parent root.For branch length,the roots bifurcate more frequently near the trunk and later they grow longer.Local thickness analysis confirms that the root diameter decays at a higher rate near the trunk than in the remaining lateral roots,while the total cross-sectional area across a bifurcation node remains mostly conserved.The histograms of branching angle,and branch length and thickness gradient can be described using lognormal and exponential distributions,respectively.This unique study presents data to characterize mechanically important structural roots,which may help link root architecture to the mechanical behaviors of root structures.展开更多
Cloud environments are essential for modern computing,but are increasingly vulnerable to Side-Channel Attacks(SCAs),which exploit indirect information to compromise sensitive data.To address this critical challenge,we...Cloud environments are essential for modern computing,but are increasingly vulnerable to Side-Channel Attacks(SCAs),which exploit indirect information to compromise sensitive data.To address this critical challenge,we propose SecureCons Framework(SCF),a novel consensus-based cryptographic framework designed to enhance resilience against SCAs in cloud environments.SCF integrates a dual-layer approach combining lightweight cryptographic algorithms with a blockchain-inspired consensus mechanism to secure data exchanges and thwart potential side-channel exploits.The framework includes adaptive anomaly detection models,cryptographic obfuscation techniques,and real-time monitoring to identify and mitigate vulnerabilities proactively.Experimental evaluations demonstrate the framework's robustness,achieving over 95%resilience against advanced SCAs with minimal computational overhead.SCF provides a scalable,secure,and efficient solution,setting a new benchmark for side-channel attack mitigation in cloud ecosystems.展开更多
The effects of some intercritical annealing parameters including heating rate, soaking temperature, soaking time, and quench media on the microstructure and mechanical properties of cold-rolled dual phase steel were s...The effects of some intercritical annealing parameters including heating rate, soaking temperature, soaking time, and quench media on the microstructure and mechanical properties of cold-rolled dual phase steel were studied. The microstructure of specimens quenched after each annealing stage was analyzed using optical microscope. The tensile properties, determined for specimens submitted to complete annealing cycles, were influenced by the volume fractions of multiphases （originated from martensite, bainite, and retained austenite）, which depend on the annealing process parameters. The results obtained showed that the yield strength and the ultimate tensile strength increase with increasing the intercritical temperature and cooling rate. This can be explained by higher martensite volume ratio with the increased volume fraction of austenite formed at the higher temperatures and cooling rates.展开更多
In industrial application,unintentional manufacturing line troubles often consequence in heating raw materials excessively,in terms of either time or temperature.One of the effects of such occurrence is a product with...In industrial application,unintentional manufacturing line troubles often consequence in heating raw materials excessively,in terms of either time or temperature.One of the effects of such occurrence is a product with a variation of prior austenite grain size,even if after the heat treatment the end result is the same,martensite.The variation of the prior austenite grain size is believed to vary the end results of the martensite.This undesirable variation includes the variation of fatigue resistance,impact strength,yield strength,hardness,etc.This research studies the effect of the prior austenite grain size on the morphology of the martensite microstructure.The results show that within the typical industrial application of temperature and holding time set up,as holding time or the temperature increases,the prior austenite average diameter increases.The block and packet sizes in the martensite also increase.The variation of mechanical property dependence on the grain size is indeed due to the different characteristics reflected in the martensite morphology.With respect to the same area,smaller grain has more blocks and packets,which agrees with higher dislocation density verified with transmission electron microscopic evaluation.展开更多
Ultra-high-temperature materials have applications in aerospace and nuclear industry.They are usually subjected to complex thermal environments during service.The mechanical properties of materials in ultra-high-tempe...Ultra-high-temperature materials have applications in aerospace and nuclear industry.They are usually subjected to complex thermal environments during service.The mechanical properties of materials in ultra-high-temperature environments have been attracted increasing attentions.However,the characterization and evaluation of ultra-high-temperature mechanical properties of materials are still challenging work.This article presents a review on the mechanical properties of materials at elevated temperatures.The experimental results and techniques on the ultra-high-temperature mechanical properties of materials are reviewed.The constitutive models of materials at elevated temperatures are discussed.The recent research progress on the quantitative theoretical characterization models for the temperature-dependent fracture strength of advanced ceramics and their composites is also given,and the emphasis is placed on the applications of the force-heat equivalence energy density principle.The thermal–mechanical-oxygen coupled computational mechanics of materials are discussed.Furthermore,the outlook and concluding remarks are highlighted.展开更多
Friction Stir Welding(FSW)is the most promising solid-state metals joining method introduced in this era.Compared to the conventional fusion welding methods,this FSW can produce joints with higher mechanical and metal...Friction Stir Welding(FSW)is the most promising solid-state metals joining method introduced in this era.Compared to the conventional fusion welding methods,this FSW can produce joints with higher mechanical and metallurgi-cal properties.Formerly,FSW was adopted for low melting metals like aluminum alloys.In recent years it has made significant progress in friction stir welding of steels since unfavourable phase transformations occurred in welds due to the melting of the parent and filler metals in fusion welding can be eliminated.The main advantage of FSW over traditional fusion welding is the reduction in the heat-affected zone(HAZ),and the joints exhibit excellent mechanical and corrosion resistance properties.This article reviews the progress in the relevant issues such as the FSW tool mate-rials and tool profiles for joining steels,microstructure and mechanical properties of steels joints,special problems in joining dissimilar steels.Moreover,in-situ heating sources was used to overcome the main limitations in FSW of hard metals and their alloys,i.e.,tool damages and insufficient heat generation.Different in-situ heating sources like laser,induction heat,gas tungsten arc welding assisted FSW for various types of steels are introduced in this review.On the basis of the up-to-date status,some problems that need further investigation are put forward.展开更多
Toarcian claystone such as that of the Callovo-Oxfordian is a qualified multiphase material. The claystone samples tested in this study are composed of four main mineral phases: silicates(clay minerals, quartz,feldspa...Toarcian claystone such as that of the Callovo-Oxfordian is a qualified multiphase material. The claystone samples tested in this study are composed of four main mineral phases: silicates(clay minerals, quartz,feldspars, micas)(z86%), sulphides(pyrite)(z3%), carbonates(calcite, dolomite)(z10%) and organic kerogen(z1%). Three sets of measurements of the modulus of deformability were compared as determined in(i) nanoindentation tests with a constant indentation depth of 2 mm,(ii) micro-indentation tests with a constant indentation depth of 20 mm, and(iii) meso-compression tests with a constant displacement of 200 mm. These three experimental methods have already been validated in earlier studies. The main objective of this study is to demonstrate the influence of the scaling effect on the modulus of deformability of the material. Different frequency distributions of the modulus of deformability were obtained at the different sample scales:(i) in nano-indentation tests, the distribution was spread between 15 GPa and 90 GPa and contained one peak at34 GPa and another at 51 GPa;(ii) in the micro-indentation tests, the distribution was spread between 25 GPa and 60 GPa and displayed peaks at 26 GPa and 37 GPa; and(iii) in the meso-compression tests, a narrow frequency distribution was obtained, ranging from 25 GPa to 50 GPa and with a maximum at around 35 GPa.展开更多
The spatial and temproal evolution of strain. fault displacement and acoustic emissions during deformation of fault systems with different geometrical textures are studied experimentally under biaxial compresison, and...The spatial and temproal evolution of strain. fault displacement and acoustic emissions during deformation of fault systems with different geometrical textures are studied experimentally under biaxial compresison, and the characteristics of typical instability events are analysed. The results show that fault systems with different geometrical textures have different evolutional images of physical field during deformation. Based on the characteristics of physical field and the deformation mechanism, various types of instability - two types of stick-slip, fracturing type and mixed type instability can be recognized. Different types of instability differ clearly in their precursors, and the instability type is closely related with the geometrical texture and the deformation stage of the fault system. Therefore, it is very significant for earthquake prediction and precursor analysis to investigatethe geometrical textures of natural active faults.展开更多
The heterogeneity of coal was studied by mechanical tests. Probability plots of experimental data show that the mechanical parameters of heterogeneous coal follow a Weibull distribution. Based on elasto-plastic mechan...The heterogeneity of coal was studied by mechanical tests. Probability plots of experimental data show that the mechanical parameters of heterogeneous coal follow a Weibull distribution. Based on elasto-plastic mechanics and gas dynamics, the model of coupled gas flow＇ and deformation process of heterogeneous coal was presented and the effects of heterogeneity of coal on gas flow and failure of coal wcrc investigated. Major findings include： The effect of the heterogeneity of coal on gas flow and mechanical thilure of coal can be considered by the model in this paper. Failure of coal has a great effect on gas flow.展开更多
Many structures and materials in nature and physiology have important ＂meso-scale＂ structures at the micron lengthscale whose tensile responses have proven difficult to characterize mechanically. Although techniques...Many structures and materials in nature and physiology have important ＂meso-scale＂ structures at the micron lengthscale whose tensile responses have proven difficult to characterize mechanically. Although techniques such as atomic force microscopy and micro- and nano-identation are mature for compression and indentation testing at the nano-scale, and standard uniaxial and shear rheometry techniques exist for the macroscale, few techniques are applicable for tensile-testing at the micrometre-scale, leaving a gap in our understanding of hierarchical biomaterials. Here, we present a novel magnetic mechanical testing （MMT） system that enables viscoelastic tensile testing at this critical length scale. The MMT system applies non-contact loading, avoiding gripping and surface interaction effects. We demonstrate application of the MMT system to the first analyses of the pure tensile responses of several native and engineered tissue systems at the mesoscale, showing the broad potential of the system for exploring micro- and meso-scale analysis of structured and hierarchical biological systems.展开更多
Titanium matrix composite reinforced by graphene nanoplatelets(GNPs)was fabricated via powder metallurgy route.Hot isostatic pressing and hot extrusion were used to consolidate the mixed powder of GNPs and TC4 titaniu...Titanium matrix composite reinforced by graphene nanoplatelets(GNPs)was fabricated via powder metallurgy route.Hot isostatic pressing and hot extrusion were used to consolidate the mixed powder of GNPs and TC4 titanium(Ti)alloy.The microstructures,mechanical properties and sliding wear performance of Ti/GNPs composite had been researched to evaluate the rein forcing effect of GNPs on tita nium matrix.Microstructure observation indicates that GNPs could restrain grai n growth slightly in titanium matrix.Titanium matrix and graphene exhibit a clean and firm interface formed by means of metallurgical bonding on atomic scale.Compared with the monolithic titanium alloy,the composite with 1.2 vol.%GNPs exhibits significantly improved elastic modulus and strength.The sliding wear test shows that there is an obvious enhancement in the tribological performance of Ti/GNPs composite with 1.2 vol.%GNPs.The results of this work indicate that GNP is an efficient reinforcenient material in titanium matrix.The strengthening mechanism including precipitates strengthening,load transfer and grain refinement mechanism of GNPs in titanium matrix was discussed.A modified shear-lag model was used to analyze the reinforcement contribution of the stress transfer mechanism.The calculation shows that the stress load mechanism constitutes the main strengthening mechanism in Ti/GNPs composite.展开更多
基金This work was financially supported by the Government of Canada through Natural Sciences and Engineering Research Council(NSERC),and the industrial collaborators led by Industrial Fasteners Institute(USA),Canadian Fasteners Institute(CFI),Boeing Company(USA),Infasco(Canada)and the Research Council on Structural Connections(RCSC).
文摘A newly proposed rapid fracture test in four-point bending was used to evaluate the effect of tempering on the hydrogen embrittlement(HE)susceptibility of an AISI 4135 steel,where it was tempered to four different strength(or hardness)levels.It was observed that HE susceptibility increases with the increase in hardness.It was shown that there will be minimal impact of hydrogen(H)on the fracture of materials with hardness 37 HRC and below,even if they are completely saturated with H.On the other hand,H will have similar detrimental effect on fracture properties of quench and tempered(Q and T)steels having hardness higher than 45 HRC.Ductile to brittle transition behavior was observed for a critical hardness(or strength)range as well as for a critical concentration level of H.Additionally,a critical H concentration was observed to exist for each of the strength levels.Fractography was performed in addition to microstructural characterization using transmission electron microscopy(TEM).A very good correlation was observed between the fast fracture test results and fractography.The fast fracture test was further compared with a conventional incremental step load(ISL)test for the evaluation of HE susceptibility.The ISL test results and fracture surface characteristics corroborate very well with the observations from the fast fracture test.This study successfully establishes the fast fracture test as a novel technique to study HE susceptibility and mechanism(s).
基金financially supported by the Major State Basic Research Development Program of China (No. 2014CB643300)
文摘The corrosion failure mechanism of M152 was studied using the neutral salt-spray test to better understand the corrosion behavior of 1Cr12Ni3Mo2VN（M152）, provide a basis for the optimization of material selection, and prevent the occurrence of failure. Moreover, the mechanism was investigated using the mass loss method, polarization curves, electrochemical impedance spectroscopy（EIS）, stereology microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy（EDS）. The results show that M152 steel suffers severe corrosion, especially pitting corrosion, in a high-salt-spray environment. In the early stage of the experiment, the color of the corrosion products was mainly orange. The products then gradually evolved into a dense, brown substance, which coincided with a decrease of corrosion rate. Correspondingly, the EIS spectrum of M152 in the late test also exhibited three time constants and presented Warburg impedance at low frequencies.
文摘With the continuous development of today's science and technology,orthopedic research has also achieved continuous updates in materials and machinery.In this case,the mechanics testing technology of orthopedics also needs to be further updated and developed,so that it can effectively meet the requirement for today's orthopedic mechanical testing.Based on this,this article analyzes several advanced orthopedic mechanics testing techniques.It is hoped that this analysis can provide a reference for the good application and development of orthopedic mechanics testing technology.
基金sponsored by Natural Science Foundation of China (Grant No. 51269012)Major Projects of Natural Science Foundation of Inner Mongolia Autonomous Region (Grant No. ZD0602)+2 种基金part of National Project 973 "Wenchuan Earthquake Mountain Hazards Formation Mechanism and Risk Control" (Grant No. 2008CB425800)funded by "New Century Excellent Talents" of University of Ministry of Education of China (Grant No. NCET-11-1016)China Scholarship Council
文摘Debris flow is one of the major secondary mountain hazards following the earthquake. This study explores the dynamic initiation mechanism of debris flows based on the strength reduction of soils through static and dynamic triaxial tests. A series of static and dynamic triaxial tests were conducted on samples in the lab. The samples were prepared according to different grain size distribution, degree of saturation and earthquake magnitudes. The relations of dynamic shear strength, degree of saturation, and number of cycles are summarized through analyzing experimental results. The findings show that the gravelly soil with a wide and continuous gradation has a critical degree of saturation of approximately 87%, above which debris flows will be triggered by rainfall, while the debris flow will be triggered at a critical degree of saturation of about 73% under the effect of rainfall and earthquake(M>6.5). Debris flow initiation is developed in the humidification process, and the earthquake provides energy for triggering debris flows. Debris flows are more likely to be triggered at the relatively low saturation under dynamic loading than under static loading. The resistance of debris flow triggering relies more on internal frication angle than soil cohesion under the effect of rainfall and earthquake. The conclusions provide an experimental analysis method for dynamic initiation mechanism of debris flows.
文摘Bell tests with entangled light have been performed many times in many ways using linear polarizers, but the same tests have never been done with a circular polarizer. Until recently there has never been a true circular polarization beamsplitter—an optical component that separates light directly into left and right handed polarizations. Using a true circular polarization beamsplitter based on birefringent gratings, entangled light has been analyzed with unexpected results.
文摘The aim of this study is to address the issues associated with traditional magnetorheological fluid(MRF)dampers,such as insufficient damping force after power failure and susceptibility to settlement.In order to achieve this,a bidirectional adjustable MRF damper was designed and developed.Magnetic field simulation analysis was conducted on the damper,along with simulation analysis on its dynamic characteristics.The dynamic characteristics were ultimately validated through experimental testing on the material testing machine,thereby corroborating the theoretical simulation results.Concurrently,this process generated valuable test data for subsequent implementation of the semi-active vibration control system.The simulation and test results demonstrate that the integrated permanent magnet effectively accomplishes bidirectional regulation.The magnetic induction intensity of the damping channel is 0.2 T in the absence of current,increases to 0.5 T when a maximum forward current of 4 A is applied,and becomes 0 T when a maximum reverse current of 3.8 A is applied.When the excitation amplitude is 8 mm and the frequency is 2 Hz,with the applied currents varying,the maximum damping force reaches 8 kN,while the minimum damping force measures at 511 N.Additionally,at zero current,the damping force stands at 2 kN,which aligns closely with simulation results.The present paper can serve as a valuable reference for the design and research of semi-active MRF dampers.
基金the financial supports of Fundamental Research Funds for the Central Universities,China(Nos.YWF-23-L-1012,YWF-22-L-1017)。
文摘The limited metal-polymer interlaminar property is a significant obstacle to the advancement of Ti/Carbon Fiber(CF)/Polyether Ether Ketone(PEEK)hybrid laminates.We report for the first time a novel method by utilizing the mussel-inspired Polydopamine(PDA)to introduce a strong chemical-physical bonding between titanium and PEEK.The enhanced Fiber-Metal Laminate(FML)exhibits a significant 48.82%enhancement in Interlaminar Shear Strength(ILSS).In addition,it alters the failure mode of the FML from single metal-resin interlaminar delamination to a multi-mechanism,including debonding,delamination of different composite layers,leading to a 28.57%improvement in maximum displacement.
基金supported by the National Natural Science Foundation of China(Grant No.12372351).
文摘In this study, to meet the development and application requirements for high-strength and hightoughness energetic structural materials, a representative volume element of a TA15 matrix embedded with a TaZrNb sphere was designed and fabricated via diffusion bonding. The mechanisms of the microstructural evolution of the TaZrNb/TA15 interface were investigated via SEM, EBSD, EDS, and XRD.Interface mechanical property tests and in-situ tensile tests were conducted on the sphere-containing structure, and an equivalent tensile-strength model was established for the structure. The results revealed that the TA15 titanium alloy and joint had high density and no pores or cracks. The thickness of the planar joint was approximately 50-60 μm. The average tensile and shear strengths were 767 MPa and 608 MPa, respectively. The thickness of the spherical joint was approximately 60 μm. The Zr and Nb elements in the joint diffused uniformly and formed strong bonds with Ti without forming intermetallic compounds. The interface exhibited submicron grain refinement and a concave-convex interlocking structure. The tensile fracture surface primarily exhibited intergranular fracture combined with some transgranular fracture, which constituted a quasi-brittle fracture mode. The shear fracture surface exhibited brittle fracture with regular arrangements of furrows. Internal fracture occurred along the spherical interface, as revealed by advanced in-situ X-ray microcomputed tomography. The experimental results agreed well with the theoretical predictions, indicating that the high-strength interface contributes to the overall strength and toughness of the sphere-containing structure.
基金supports provided by the National Natural Science Foundation of China(No.52372330).
文摘The small punch test technique facilitates the convenient acquisition of the mechanical properties of in-service equipment materials and the assessment of their remaining service life through sampling.However,the weldability of components with thin walls after small punch sampling,such as ethylene cracking furnace tubes,requires further investigation.Therefore,the weldability of in-service ethylene cracking furnace tubes following small punch sampling was investigated through nondestructive testing,microstructural characterization,and mechanical testing.Additionally,the impact of small punch sampling size and residual stress on the creep performance of the specimens was studied using an improved ductility exhaustion model.The results indicate that both the surface and interior of the weld repair areas on new furnace tubes and service-exposed furnace tubes after small-punch sampling are defect-free,exhibiting good weld quality.The strength of the specimens after weld repair was higher than that before sampling,whereas toughness decreased.Weld repair following small punch sampling of furnace tubes is both feasible and necessary.Furthermore,a linear relationship was observed between specimen thickness,diameter,and creep fracture time.The residual stress of welding affects the creep performance of the specimen under different stresses.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIT)(RS-2024-00340851)the Engineering Research Center Program of the National Science Foundation(NSF)under NSF Cooperative Agreement EEC-1449501.
文摘Characterizing the architecture of tree root systems is essential to advance the development of root-inspired anchorage in engineered systems.This study explores the structural root architectures of orchard trees to understand the interplays between the mechanical behavior of roots and the root architecture.Full three-dimensional(3D)models of natural tree root systems,Lovell,Marianna,and Myrobalan,that were extracted from the ground by vertical pullout are reconstructed through photogrammetry and later skeletonized as nodes and root branch segments.Combined analyses of the full 3D models and skeletonized models enable a detailed examination of basic bulk properties and quantification of architectural parameters.While the root segments are divided into three categories,trunk root,main lateral root,and remaining roots,the patterns in branching and diameter distributions show significant differences between the trunk and main laterals versus the remaining lateral roots.In general,the branching angle decreases over the sequence of bifurcations.The main lateral roots near the trunk show significant spreading while the lateral roots near the ends grow roughly parallel to the parent root.For branch length,the roots bifurcate more frequently near the trunk and later they grow longer.Local thickness analysis confirms that the root diameter decays at a higher rate near the trunk than in the remaining lateral roots,while the total cross-sectional area across a bifurcation node remains mostly conserved.The histograms of branching angle,and branch length and thickness gradient can be described using lognormal and exponential distributions,respectively.This unique study presents data to characterize mechanically important structural roots,which may help link root architecture to the mechanical behaviors of root structures.
文摘Cloud environments are essential for modern computing,but are increasingly vulnerable to Side-Channel Attacks(SCAs),which exploit indirect information to compromise sensitive data.To address this critical challenge,we propose SecureCons Framework(SCF),a novel consensus-based cryptographic framework designed to enhance resilience against SCAs in cloud environments.SCF integrates a dual-layer approach combining lightweight cryptographic algorithms with a blockchain-inspired consensus mechanism to secure data exchanges and thwart potential side-channel exploits.The framework includes adaptive anomaly detection models,cryptographic obfuscation techniques,and real-time monitoring to identify and mitigate vulnerabilities proactively.Experimental evaluations demonstrate the framework's robustness,achieving over 95%resilience against advanced SCAs with minimal computational overhead.SCF provides a scalable,secure,and efficient solution,setting a new benchmark for side-channel attack mitigation in cloud ecosystems.
基金Item Sponsored by Prime Ministry State Planning Organization of Turkey(5045003)
文摘The effects of some intercritical annealing parameters including heating rate, soaking temperature, soaking time, and quench media on the microstructure and mechanical properties of cold-rolled dual phase steel were studied. The microstructure of specimens quenched after each annealing stage was analyzed using optical microscope. The tensile properties, determined for specimens submitted to complete annealing cycles, were influenced by the volume fractions of multiphases （originated from martensite, bainite, and retained austenite）, which depend on the annealing process parameters. The results obtained showed that the yield strength and the ultimate tensile strength increase with increasing the intercritical temperature and cooling rate. This can be explained by higher martensite volume ratio with the increased volume fraction of austenite formed at the higher temperatures and cooling rates.
文摘In industrial application,unintentional manufacturing line troubles often consequence in heating raw materials excessively,in terms of either time or temperature.One of the effects of such occurrence is a product with a variation of prior austenite grain size,even if after the heat treatment the end result is the same,martensite.The variation of the prior austenite grain size is believed to vary the end results of the martensite.This undesirable variation includes the variation of fatigue resistance,impact strength,yield strength,hardness,etc.This research studies the effect of the prior austenite grain size on the morphology of the martensite microstructure.The results show that within the typical industrial application of temperature and holding time set up,as holding time or the temperature increases,the prior austenite average diameter increases.The block and packet sizes in the martensite also increase.The variation of mechanical property dependence on the grain size is indeed due to the different characteristics reflected in the martensite morphology.With respect to the same area,smaller grain has more blocks and packets,which agrees with higher dislocation density verified with transmission electron microscopic evaluation.
文摘Ultra-high-temperature materials have applications in aerospace and nuclear industry.They are usually subjected to complex thermal environments during service.The mechanical properties of materials in ultra-high-temperature environments have been attracted increasing attentions.However,the characterization and evaluation of ultra-high-temperature mechanical properties of materials are still challenging work.This article presents a review on the mechanical properties of materials at elevated temperatures.The experimental results and techniques on the ultra-high-temperature mechanical properties of materials are reviewed.The constitutive models of materials at elevated temperatures are discussed.The recent research progress on the quantitative theoretical characterization models for the temperature-dependent fracture strength of advanced ceramics and their composites is also given,and the emphasis is placed on the applications of the force-heat equivalence energy density principle.The thermal–mechanical-oxygen coupled computational mechanics of materials are discussed.Furthermore,the outlook and concluding remarks are highlighted.
基金Supported by National Natural Science Foundation of China(Grant No.51842507).
文摘Friction Stir Welding(FSW)is the most promising solid-state metals joining method introduced in this era.Compared to the conventional fusion welding methods,this FSW can produce joints with higher mechanical and metallurgi-cal properties.Formerly,FSW was adopted for low melting metals like aluminum alloys.In recent years it has made significant progress in friction stir welding of steels since unfavourable phase transformations occurred in welds due to the melting of the parent and filler metals in fusion welding can be eliminated.The main advantage of FSW over traditional fusion welding is the reduction in the heat-affected zone(HAZ),and the joints exhibit excellent mechanical and corrosion resistance properties.This article reviews the progress in the relevant issues such as the FSW tool mate-rials and tool profiles for joining steels,microstructure and mechanical properties of steels joints,special problems in joining dissimilar steels.Moreover,in-situ heating sources was used to overcome the main limitations in FSW of hard metals and their alloys,i.e.,tool damages and insufficient heat generation.Different in-situ heating sources like laser,induction heat,gas tungsten arc welding assisted FSW for various types of steels are introduced in this review.On the basis of the up-to-date status,some problems that need further investigation are put forward.
文摘Toarcian claystone such as that of the Callovo-Oxfordian is a qualified multiphase material. The claystone samples tested in this study are composed of four main mineral phases: silicates(clay minerals, quartz,feldspars, micas)(z86%), sulphides(pyrite)(z3%), carbonates(calcite, dolomite)(z10%) and organic kerogen(z1%). Three sets of measurements of the modulus of deformability were compared as determined in(i) nanoindentation tests with a constant indentation depth of 2 mm,(ii) micro-indentation tests with a constant indentation depth of 20 mm, and(iii) meso-compression tests with a constant displacement of 200 mm. These three experimental methods have already been validated in earlier studies. The main objective of this study is to demonstrate the influence of the scaling effect on the modulus of deformability of the material. Different frequency distributions of the modulus of deformability were obtained at the different sample scales:(i) in nano-indentation tests, the distribution was spread between 15 GPa and 90 GPa and contained one peak at34 GPa and another at 51 GPa;(ii) in the micro-indentation tests, the distribution was spread between 25 GPa and 60 GPa and displayed peaks at 26 GPa and 37 GPa; and(iii) in the meso-compression tests, a narrow frequency distribution was obtained, ranging from 25 GPa to 50 GPa and with a maximum at around 35 GPa.
文摘The spatial and temproal evolution of strain. fault displacement and acoustic emissions during deformation of fault systems with different geometrical textures are studied experimentally under biaxial compresison, and the characteristics of typical instability events are analysed. The results show that fault systems with different geometrical textures have different evolutional images of physical field during deformation. Based on the characteristics of physical field and the deformation mechanism, various types of instability - two types of stick-slip, fracturing type and mixed type instability can be recognized. Different types of instability differ clearly in their precursors, and the instability type is closely related with the geometrical texture and the deformation stage of the fault system. Therefore, it is very significant for earthquake prediction and precursor analysis to investigatethe geometrical textures of natural active faults.
基金Supported by the Key National Natural Science Foundation of China （50434020） the Natural Science Foundation of Hebei Province, China （E2010000872, Z2009315）
文摘The heterogeneity of coal was studied by mechanical tests. Probability plots of experimental data show that the mechanical parameters of heterogeneous coal follow a Weibull distribution. Based on elasto-plastic mechanics and gas dynamics, the model of coupled gas flow＇ and deformation process of heterogeneous coal was presented and the effects of heterogeneity of coal on gas flow and failure of coal wcrc investigated. Major findings include： The effect of the heterogeneity of coal on gas flow and mechanical thilure of coal can be considered by the model in this paper. Failure of coal has a great effect on gas flow.
基金partially supported by the National Natural Science Foundation of China(Grants 11532009,11372243,and 11522219)the China Postdoctoral Science Foundation(Grant 2016M602810)This project was also supported by the Initiative Postdocs Supporting Program(Grant BX201600121)
文摘Many structures and materials in nature and physiology have important ＂meso-scale＂ structures at the micron lengthscale whose tensile responses have proven difficult to characterize mechanically. Although techniques such as atomic force microscopy and micro- and nano-identation are mature for compression and indentation testing at the nano-scale, and standard uniaxial and shear rheometry techniques exist for the macroscale, few techniques are applicable for tensile-testing at the micrometre-scale, leaving a gap in our understanding of hierarchical biomaterials. Here, we present a novel magnetic mechanical testing （MMT） system that enables viscoelastic tensile testing at this critical length scale. The MMT system applies non-contact loading, avoiding gripping and surface interaction effects. We demonstrate application of the MMT system to the first analyses of the pure tensile responses of several native and engineered tissue systems at the mesoscale, showing the broad potential of the system for exploring micro- and meso-scale analysis of structured and hierarchical biological systems.
基金National Natural Science Foundation of China(51802296)Beijing Municipal Science and Technology Commission(Z171100002017016,Z191100005619006).
文摘Titanium matrix composite reinforced by graphene nanoplatelets(GNPs)was fabricated via powder metallurgy route.Hot isostatic pressing and hot extrusion were used to consolidate the mixed powder of GNPs and TC4 titanium(Ti)alloy.The microstructures,mechanical properties and sliding wear performance of Ti/GNPs composite had been researched to evaluate the rein forcing effect of GNPs on tita nium matrix.Microstructure observation indicates that GNPs could restrain grai n growth slightly in titanium matrix.Titanium matrix and graphene exhibit a clean and firm interface formed by means of metallurgical bonding on atomic scale.Compared with the monolithic titanium alloy,the composite with 1.2 vol.%GNPs exhibits significantly improved elastic modulus and strength.The sliding wear test shows that there is an obvious enhancement in the tribological performance of Ti/GNPs composite with 1.2 vol.%GNPs.The results of this work indicate that GNP is an efficient reinforcenient material in titanium matrix.The strengthening mechanism including precipitates strengthening,load transfer and grain refinement mechanism of GNPs in titanium matrix was discussed.A modified shear-lag model was used to analyze the reinforcement contribution of the stress transfer mechanism.The calculation shows that the stress load mechanism constitutes the main strengthening mechanism in Ti/GNPs composite.
