In this paper, the nonlinear bandings for the orthotropic rectangular thin plates under various supports are studied.The uniformly valid asymptotic solutions of the displacement ? and stress function φ are derived by...In this paper, the nonlinear bandings for the orthotropic rectangular thin plates under various supports are studied.The uniformly valid asymptotic solutions of the displacement ? and stress function φ are derived by the perturbation offered in [1].展开更多
This study investigates the flexural performance of ultra-high performance concrete(UHPC)in reinforced concrete T-beams,focusing on the effects of interfacial treatments.Three concrete T-beam specimens were fabricated...This study investigates the flexural performance of ultra-high performance concrete(UHPC)in reinforced concrete T-beams,focusing on the effects of interfacial treatments.Three concrete T-beam specimens were fabricated and tested:a control beam(RC-T),a UHPC-reinforced beam with a chiseled interface(UN-C-50F),and a UHPC-reinforced beam featuring both a chiseled interface and anchored steel rebars(UN-CS-50F).The test results indicated that both chiseling and the incorporation of anchored rebars effectively created a synergistic combination between the concrete T-beam and the UHPC reinforcement layer,with the UN-CS-50F exhibiting the highest flexural resistance.The cracking load and ultimate load of UN-CS-50F were 221.5%and 40.8%,respectively,higher than those of the RC-T.Finite element(FE)models were developed to provide further insights into the behavior of the UHPCreinforced T-beams,showing a maximumdeviation of just 8%when validated against experimental data.A parametric analysis varied the height,thickness,andmaterial strength of the UHPC reinforcement layer based on the validated FE model,revealing that increasing the UHPC layer thickness from 30 to 50 mm improved the ultimate resistance by 20%while reducing the UHPC reinforcement height from 440 to 300 mm led to a 10%decrease in bending resistance.The interfacial anchoring rebars significantly reduced crack propagation and enhanced stress redistribution,highlighting the importance of strengthening interfacial bonds and optimizing geometric parameters ofUHPCfor improved T-beam performance.These findings offer valuable insights for the design and retrofitting of UHPC-reinforced bridge girders.展开更多
Flexoelectricity refers to the link between electrical polarization and strain gradient fields in piezoelectric materials,particularly at the nano-scale.The present investigation aims to comprehensively focus on the s...Flexoelectricity refers to the link between electrical polarization and strain gradient fields in piezoelectric materials,particularly at the nano-scale.The present investigation aims to comprehensively focus on the static bending analysis of a piezoelectric sandwich functionally graded porous(FGP)double-curved shallow nanoshell based on the flexoelectric effect and nonlocal strain gradient theory.Two coefficients that reduce or increase the stiffness of the nanoshell,including nonlocal and length-scale parameters,are considered to change along the nanoshell thickness direction,and three different porosity rules are novel points in this study.The nanoshell structure is placed on a Pasternak elastic foundation and is made up of three separate layers of material.The outermost layers consist of piezoelectric smart material with flexoelectric effects,while the core layer is composed of FGP material.Hamilton’s principle was used in conjunction with a unique refined higher-order shear deformation theory to derive general equilibrium equations that provide more precise outcomes.The Navier and Galerkin-Vlasov methodology is used to get the static bending characteristics of nanoshells that have various boundary conditions.The program’s correctness is assessed by comparison with published dependable findings in specific instances of the model described in the article.In addition,the influence of parameters such as flexoelectric effect,nonlocal and length scale parameters,elastic foundation stiffness coefficient,porosity coefficient,and boundary conditions on the static bending response of the nanoshell is detected and comprehensively studied.The findings of this study have practical implications for the efficient design and control of comparable systems,such as micro-electromechanical and nano-electromechanical devices.展开更多
This study aimed to investigate the moment redistribution in continuous glass fiber reinforced polymer(GFRP)-concrete composite slabs caused by concrete cracking and steel bar yielding in the negative bending moment z...This study aimed to investigate the moment redistribution in continuous glass fiber reinforced polymer(GFRP)-concrete composite slabs caused by concrete cracking and steel bar yielding in the negative bending moment zone.An experimental bending moment redistribution test was conducted on continuous GFRP-concrete composite slabs,and a calculation method based on the conjugate beam method was proposed.The composite slabs were formed by combining GFRP profiles with a concrete layer and supported on steel beams to create two-span continuous composite slab specimens.Two methods,epoxy resin bonding,and stud connection,were used to connect the composite slabs with the steel beams.The experimental findings showed that the specimen connected with epoxy resin exhibited two moments redistribution phenomena during the loading process:concrete cracking and steel bar yielding at the internal support.In contrast,the composite slab connected with steel beams by studs exhibited only one-moment redistribution phenomenon throughout the loading process.As the concrete at the internal support cracked,the bending moment decreased in the internal support section and increased in the midspan section.When the steel bars yielded,the bending moment further decreased in the internal support section and increased in the mid-span section.Since GFRP profiles do not experience cracking,there was no significant decrease in the bending moment of the mid-span section.All test specimens experienced compressive failure of concrete at the mid-span section.Calculation results showed good agreement between the calculated and experimental values of bending moments in the mid-span section and internal support section.The proposed model can effectively predict the moment redistribution behavior of continuous GFRP-concrete composite slabs.展开更多
When the upper chord beam of the beam-string structure(BSS)is made of concrete-filled steel tube(CFST),its overall stiffness will change greatly with the construction of concrete placement,which will have an impact on ...When the upper chord beam of the beam-string structure(BSS)is made of concrete-filled steel tube(CFST),its overall stiffness will change greatly with the construction of concrete placement,which will have an impact on the design of the tensioning plans and selection of control measures for the BSS.In order to accurately obtain the bending stiffness of CFST beam and clarify its impact on the mechanical properties of composite BSS during con-struction,the influence of some factors such as height-width ratio,wall thickness of steel tube,elasticity modulus of concrete,and friction coefficient on the bending stiffness are analyzed parametrically by the numerical simula-tion technology based on an actual project.The calculation formula of the equivalent bending stiffness of CFST is also established through mathematical statistical simulation.Then,the equivalent bending stiffness is introduced into the construction and use stages of the composite BSS,respectively,and the mechanical properties such as prestress-tensioning control value,structural deformation,and internal force of key members are comparatively analyzed when adopting two different construction plans.Moreover,the optimal construction plan of concrete placementfirst and then prestress-tensioning is proposed.展开更多
Ti-Mo-O alloys were used to analyze the effect of Mo and O contents on the mechanical compatibility and biocompatibility.The bending modulus,bending yield strength and springback ratio of the alloys were evaluated by ...Ti-Mo-O alloys were used to analyze the effect of Mo and O contents on the mechanical compatibility and biocompatibility.The bending modulus,bending yield strength and springback ratio of the alloys were evaluated by using three-point bending tests and bending load-unloading tests.The biocompatibility was investigated by the adhesion,proliferation and the alkaline phosphatase(ALP)activity of mouse osteoblast-like cells(MC3T3-E1).The results showed that the bending modulus and bending yield strength first were increased and then decreased with the increase in Mo content,while the springback ratio exhibited an opposite trend to the bending modulus.With the increase in O content,the bending modulus remained almost constant,while the bending yield strength was increased.The springback ratio exhibited a similar trend to the bending yield strength.The in vitro biological experiments showed that the Ti-Mo-O alloys had excellent biocompatibility due to the formed stable oxide films on their surface.With the increase in O and Mo contents,the TiO_(2)-MoO_(2)oxide film became denser.Combining with mechanical compatibility and biocompatibility,the Ti-15Mo-0.2O and Ti-15Mo-0.3O alloys were more suitable for the biomedical application of spinal fixation device.展开更多
Fiber Bragg grating(FBG)sensors are extensively used in various sensing applications due to their high sensitivity.However,they are inherently sensitive to both strain and temperature,with a cross-sensitivity problem,...Fiber Bragg grating(FBG)sensors are extensively used in various sensing applications due to their high sensitivity.However,they are inherently sensitive to both strain and temperature,with a cross-sensitivity problem,making it impossible to simultaneously monitor these two parameters using the Bragg wavelength shifts of a single uniform FBG.In this study,we bend the FBG pigtail to cause bending loss.The peak power of the FBG is used as the second characterization quantity.Our experimental results show that the Bragg wavelength sensitivities to strain(K_(ε))and temperature(K_(T))are 0.17 pm/ue and 16.5 pm/℃,respectively.Additionally,the peak power sensitivities to strain(P_(ε))and temperature(P_(T))are-0.00202 dBm/μεand-0.06 dBm/℃,respectively.The linear correlation coefficients for these measurements are all above 0.996.In this way,it is possible to simultaneously measure both strain and temperature using a single uniform FBG.展开更多
The bending collapse and energy absorption of 7003 aluminum alloy bumper beams under four aging conditions(pre-aging,under-aging,peak-aging,and over-aging)were investigated through three-point bending tests.Microstruc...The bending collapse and energy absorption of 7003 aluminum alloy bumper beams under four aging conditions(pre-aging,under-aging,peak-aging,and over-aging)were investigated through three-point bending tests.Microstructural characterization was performed using scanning electron microscopy and transmission electron microscopy.Based on the Swift−Hockett−Sherby constitutive model combined with the Gurson−Tvergaard−Needleman damage model,the plastic response and fracture behavior of the 7003 aluminum alloy under uniaxial tension and three-point bending were accurately predicted.The results showed that the peak bending force of the beams was proportional to the strength under different aging states,while stress triaxiality governed the cracking failure.Pre-aged and under-aged beams resisted cracking until reaching 250 mm displacement due to stress transition from tensile to compression on the bottom surface.The under-aged beam exhibited optimal energy absorption(7.86 kJ)and a higher peak force(38.75 kN).展开更多
Powered fight in birds is reliant on feathers forming an aerodynamic surface that resists air pressures.Many basic aspects of feather functionality are unknown,which hampers our understanding of wing function in birds...Powered fight in birds is reliant on feathers forming an aerodynamic surface that resists air pressures.Many basic aspects of feather functionality are unknown,which hampers our understanding of wing function in birds.This study measured the dimensions of primary and secondaryfight feathers of 19 species of parrots.The maximum force the feathers could withstand from below was also measured to mimic the pressuresexperienced during a downstroke.The analysis tested whether:(1)feather dimensions differed along the wing and among secondary and primary remiges;(2)the force that feathers could withstand varied among the remiges;and(3)there would be isometric relationships with bodymass for feather characteristics.The results show that body mass signifcantly affected vane width,rachis thickness,maximum force,and ultimate bending moment,but the relationship for feather length only approached signifcance.Many of the proximal secondary feathers showedsignifcantly lower values relative to the frst primary,whereas for distal primaries the values were greater.There were isometric relationships forforce measurements of primary and secondary feathers with body mass,but there was positive allometry for feather lengths and vane widths.The forces feathers can withstand vary along the wing may be a proxy for the aerodynamic properties of the feathers in situ.Broader taxonomicstudies that explore these topics are required for other species representing a range of different orders.A better understanding of the functionality of feathers will improve our understanding of how avian fight works particularly considering the variety in fight style and wing shape in birds.展开更多
This study investigates the influence of initial crystallographic texture on the deformation mechanisms during three-point bending of AZ31 Mg alloy sheets.Three distinct orientations are examined by using the followin...This study investigates the influence of initial crystallographic texture on the deformation mechanisms during three-point bending of AZ31 Mg alloy sheets.Three distinct orientations are examined by using the following bending specimens:(i)the normal direction(ND)sample,where the c-axes are predominantly aligned along the specimen thickness,(ii)the rolling direction(RD)sample,where the c-axes are mostly aligned along the longitudinal direction,and(iii)the 45 sample,where the c-axes are tilted at approximately 45°from both the thickness and longitudinal directions.The bending properties vary significantly depending on the initial texture,thereby affecting the strain accommodation and dominant deformation modes.The ND sample exhibits the lowest bendability due to its unfavorable orientation for{10–12}extension twinning and basal slip,which results in poor strain accommodation and early crack initiation in the outer tensile side.By comparison,the RD sample demonstrates an approximately 22.1%improvement,with extensive{10–12}extension twinning in the outer tensile zone.Meanwhile,the 45 sample exhibits the highest bendability(approximately 75.7%greater than that of the ND sample)due to sustained activation of both basal slip and{10–12}extension twinning,promoting uniform strain distribution and delaying fracture.Detailed electron backscatter diffraction analysis reveals that the 45 sample retains favorable crystallographic orientations for basal slip throughout bending,minimizing strain localization and enhancing the bendability.These findings highlight the importance of tailoring the initial texture in order to optimize the bending properties of Mg alloy sheets,and provide valuable insights for improving the manufacturability of Mg-based structural components.展开更多
To improve the rigidity and flexibility of conventional grouting materials,one visionary approach is to replace Portland cement with a composite cementitious system containing circulating fluidized bed fly ash(CFBFA)a...To improve the rigidity and flexibility of conventional grouting materials,one visionary approach is to replace Portland cement with a composite cementitious system containing circulating fluidized bed fly ash(CFBFA)and calcium carbide slag(CS),while adding ethylene-vinyl acetate(EVA)copolymer and CO_(2)as modifiers to enhance its properties.In this research,CFBFA and CS assumed the role of cementitious constituents,with EVA and CO_(2)serving as the modifying agent.A comprehensive exploration of the mechanism underlying the CO_(2)+EVA modified composite cementitious system was undertaken,delving into the differences of its compressive,bending,and flexural strengths.The addition of CO_(2)further improved the flexibility and rigidity of the materials and effectively improve the material's microstructure.It was worth noting that when CO_(2)+EVA co-modified CFBFA-CS composite cementitious materials,the flexibility and rigidity of the cementitious materials were significantly enhanced,and the bending strength,flexural strength and compressive strength were significantly increased by 48.76%,166.7%and 40.56%,respectively,and the 28 d density was reduced by 6.91%.These results provided a theoretical basis for the realization of avant-garde cementitious materials with functional properties.展开更多
This research investigates the bending response of folded multi-celled tubes(FMTs)fabricated by folded metal sheets.A three-point bending test for FMTs with circular and square sections is designed and introduced.The ...This research investigates the bending response of folded multi-celled tubes(FMTs)fabricated by folded metal sheets.A three-point bending test for FMTs with circular and square sections is designed and introduced.The base numerical models are correlated with physical experiments and a static crashworthiness analysis of six FMT configurations to assess their energy absorption characteristics.The influences of thickness,sectional shape,and load direction on the bending response are studied.Results indicate that increasing the thickness of the tube and radian of the inner tube enhances the crashworthiness performance of FMT,yielding a 20.50%increase in mean crushing force,a 55.53%increase in specific energy absorption,and an 18.05%decrease in peak crushing force compared to traditional multi-celled tubes(TMTs).A theoretical analysis of the specific energy absorption indicates that FMTs outperform TMTs,particularly when the peak crushing force is prominent.This study highlights the innovative and practical potential of FMTs to improve the crashworthiness of thin-walled structures.展开更多
The present study investigates the non-isothermal flow and energy distribution through a loosely bent rectangular duct using a spectral-based numerical approach over a wide range of the Dean number 0<Dn≤3000.Unlik...The present study investigates the non-isothermal flow and energy distribution through a loosely bent rectangular duct using a spectral-based numerical approach over a wide range of the Dean number 0<Dn≤3000.Unlike previous research,this work offers novel insights by conducting a grid-point-specific velocity analysis and identifying new bifurcation structures.The study reveals how centrifugal and buoyancy forces interact to produce steady,periodic,and chaotic flow regimes significantly influencing heat transfer performance.The Newton-Raphson method is employed to explore four asymmetric steady branches,with vortex solutions ranging from 2-to 12 vortices.Unsteady flow characteristics are analyzed exquisitely by performing time-advancement of the solutions and the flow regimes are shown as a percentage of total flow with longitudinal vortex generation.Axial flow,secondary flow,and temperature profiles have been depicted in accordance with Dn to wander the flow pattern,and it is predicted that the time-dependent flow(TDF)consists of asymmetric 2-to 10-vortex solutions.The significant findings of this study include the axial displacement of the circulations due to the influence of the time-varying temperature dispersal applied along the wall.Chaotic flows,which dominate the higher Dean number range,are shown to enhance heat convection due to increased fluid mixing.A detailed comparison with prior research demonstrates the advantages of this approach,particularly in capturing complex non-linear behaviors.The findings of this study provide practical guidelines for optimizing duct designs to maximize heat transfer and suggest future research directions,such as using nanofluids or studying Magneto-hydrodynamics in the same configuration.展开更多
The relatively insufficient knowledge of the deformation behavior has limited the wide application of the lightest structure material-Mg alloys.Among others,bending behavior is of great importance because it is unavoi...The relatively insufficient knowledge of the deformation behavior has limited the wide application of the lightest structure material-Mg alloys.Among others,bending behavior is of great importance because it is unavoidably involved in various forming processes,such as folding,stamping,etc.The hexagonal close-packed structure makes it even a strong texture-dependent behavior and even hard to capture and predict.In this regard,the bending behaviors are investigated in terms of both experiments and simulations in the current work.Bending samples with longitudinal directions inclined from the transverse direction by different angles have been prepared from an extruded AZ31 plate,respectively.The moment-curvature curves and strain distribution have been recorded in the four-point bending tests assisted with an in-situ digital image correlation(DIC)system.A crystal-plasticity-based bending-specific approach named EVPSC-BEND was applied to bridge the mechanical response to the microstructure evolution and underlying deformation mechanisms.The flow stress,texture,twin volume fraction,stress distribution,and strain distribution evolve differently from sample to sample,manifesting strong texture-dependent bending behaviors.The underlying mechanisms associated with this texture dependency,especially the occurrence of both twinning and detwinning during the monotonic bending,are carefully discussed.Besides,the simulation has been conducted to reveal the moment-inclination angle relation of the investigated AZ31 extruded plate in terms of the polar coordinate,which intuitively shows the texture-dependent behaviors.Specifically,the samples with longitudinal directions parallel to the extruded direction bear the biggest initial yielding moment.展开更多
The shear characteristics of bolted rock joints are crucial for the stability of tunneling and mining,particularly in deep underground engineering,where rock bolt materials are exposed to high stress,water pressure,an...The shear characteristics of bolted rock joints are crucial for the stability of tunneling and mining,particularly in deep underground engineering,where rock bolt materials are exposed to high stress,water pressure,and engineering disturbance.However,due to the complex interaction between bolted rock joints and various geological contexts,many challenges and unsolved problems arise.Therefore,more investigation is needed to understand the shear performance of bolted joints in the field of deep underground engineering.This study presents a comprehensive review of research findings on the responses of bolted joints subjected to shearing under different conditions.As is revealed,the average shear strength of bolted rock joints increases linearly with the normal stress and increases with the compressive strength of rock until it reaches a stable value.The joint roughness coefficient(JRC)affects the contact area,friction force,shear strength,bending angle,and axial force of bolted rock joints.A mathematical function is proposed to model the relationship between JRC,normal load,and shear strength.The normal stress level also influences the deformation model,load-carrying capacity,and energy absorption ratio of bolts within bolted rock joints,and can be effectively characterized by a two-phase exponential equation.Additionally,the angle of the bolts affects the ratio of tensile and shear strength of the bolts,as well as the mechanical behavior of both bolted rock joints and surrounding rock,which favors smaller angles.This comprehensive review of experimental data on the shear behavior of bolted rock joints offers valuable theoretical insights for the development of advanced shear devices and further pertinent investigations.展开更多
Piezoelectric active vibration control holds paramount importance in space structures.An embedded piezoelectric actuator with a sandwich configuration is proposed,which enhances control accuracy by integrating various...Piezoelectric active vibration control holds paramount importance in space structures.An embedded piezoelectric actuator with a sandwich configuration is proposed,which enhances control accuracy by integrating various components.Firstly,the electromechanical coupling characteristics of the actuator are revealed,and the model is established.Secondly,the equivalent model of a cylindrical cantilever beam is investigated as the object,and the feasibility of the vibration control of the actuator is verified by simulation.Finally,the prototype comprised of two actuators,which respectively use the proposed embedded actuators for producing the vibration and suppressing the vibration,is developed,and the measurement system is constructed.Experimental results demonstrate the excellent control efficiency in two orthogonal directions,achieving a minimum vibration amplitude control of 0.00102 mm and a maximum vibration control of-42.74 d B.The integrated structure offers fast response,lightness,adaptability,and high control efficiency,which is conducive to enhancing the vibration control.展开更多
Buckling failure in submarine cables presents a prevalent challenge in ocean engineering.This work aims to explore the buckling behavior of umbilical cables with damaged sheaths subjected to compression and bending cy...Buckling failure in submarine cables presents a prevalent challenge in ocean engineering.This work aims to explore the buckling behavior of umbilical cables with damaged sheaths subjected to compression and bending cyclic loads.A finite element model is devised,incorporating a singular armor wire,a rigid core,and a damaged sheath.To scrutinize the buckling progression and corresponding deformation,axial compression and bending cyclic loads are introduced.The observations reveal that a reduction in axial compression results in a larger number of cycles before buckling ensues and progressively shifts the buckling position toward the extrados and fixed end.Decreasing the bending radius precipitates a reduction in the buckling cycle number and minimizes the deformation in the armor wire.Furthermore,an empirical model is presented to predict the occurrence of birdcage buckling,providing a means to anticipate buckling events and to estimate the requisite number of cycles leading to buckling.展开更多
Piezoelectric ceramic bending actuators play a pivotal role in various high-tech applications.As a new strategy for fabricating bending actuators,constructing defect dipole concentration gradient has emerged as an eff...Piezoelectric ceramic bending actuators play a pivotal role in various high-tech applications.As a new strategy for fabricating bending actuators,constructing defect dipole concentration gradient has emerged as an effective strategy for boosting electro-bending displacement,yet achieving reproducibility remains challenging due to the uncontrollable alkali volatilization.Herein we propose a new strategy to fabricate barium-doped(K,Na)NbO_(3) piezoelectric bending actuators with controllable gradient distribution of highly stable<110>-oriented(V_(K/Na)'-V_(O)··)defect dipoles,achieving a centimeter-level displacement performance of 1.2 cm under±200 V sinusoidal AC excitations.Samples with defect gradient design but lower oxygen vacancy content exhibit larger bending displacement and excellent fatigue stability without leakage conduction,confirming that the defect dipole concentration gradient,rather than oxygen vacancy migration drives the large bending deformation.Experimental analysis combined with phase-field simulations uncovers that the delicate concentration design of<110>-oriented defect dipoles within orthorhombic stripe domains plays crucial roles in controllable and stable displacement output.We validate the feasibility of the bending actuators in piezoelectric haptic feedback and piezoelectric micro-pump applications,providing new insights into the design of piezoceramic actuators.展开更多
文摘In this paper, the nonlinear bandings for the orthotropic rectangular thin plates under various supports are studied.The uniformly valid asymptotic solutions of the displacement ? and stress function φ are derived by the perturbation offered in [1].
基金The National Natural Science Foundation of China(Grant#52278161)the Science and Technology Project of Guangzhou(Grant#2024A04J9888)the Guangdong Basic and Applied Basic Research Foundation(Grant#2023A1515010535).
文摘This study investigates the flexural performance of ultra-high performance concrete(UHPC)in reinforced concrete T-beams,focusing on the effects of interfacial treatments.Three concrete T-beam specimens were fabricated and tested:a control beam(RC-T),a UHPC-reinforced beam with a chiseled interface(UN-C-50F),and a UHPC-reinforced beam featuring both a chiseled interface and anchored steel rebars(UN-CS-50F).The test results indicated that both chiseling and the incorporation of anchored rebars effectively created a synergistic combination between the concrete T-beam and the UHPC reinforcement layer,with the UN-CS-50F exhibiting the highest flexural resistance.The cracking load and ultimate load of UN-CS-50F were 221.5%and 40.8%,respectively,higher than those of the RC-T.Finite element(FE)models were developed to provide further insights into the behavior of the UHPCreinforced T-beams,showing a maximumdeviation of just 8%when validated against experimental data.A parametric analysis varied the height,thickness,andmaterial strength of the UHPC reinforcement layer based on the validated FE model,revealing that increasing the UHPC layer thickness from 30 to 50 mm improved the ultimate resistance by 20%while reducing the UHPC reinforcement height from 440 to 300 mm led to a 10%decrease in bending resistance.The interfacial anchoring rebars significantly reduced crack propagation and enhanced stress redistribution,highlighting the importance of strengthening interfacial bonds and optimizing geometric parameters ofUHPCfor improved T-beam performance.These findings offer valuable insights for the design and retrofitting of UHPC-reinforced bridge girders.
基金This work was supported by the Le Quy Don Technical University Research Fund(Grant No.23.1.11).
文摘Flexoelectricity refers to the link between electrical polarization and strain gradient fields in piezoelectric materials,particularly at the nano-scale.The present investigation aims to comprehensively focus on the static bending analysis of a piezoelectric sandwich functionally graded porous(FGP)double-curved shallow nanoshell based on the flexoelectric effect and nonlocal strain gradient theory.Two coefficients that reduce or increase the stiffness of the nanoshell,including nonlocal and length-scale parameters,are considered to change along the nanoshell thickness direction,and three different porosity rules are novel points in this study.The nanoshell structure is placed on a Pasternak elastic foundation and is made up of three separate layers of material.The outermost layers consist of piezoelectric smart material with flexoelectric effects,while the core layer is composed of FGP material.Hamilton’s principle was used in conjunction with a unique refined higher-order shear deformation theory to derive general equilibrium equations that provide more precise outcomes.The Navier and Galerkin-Vlasov methodology is used to get the static bending characteristics of nanoshells that have various boundary conditions.The program’s correctness is assessed by comparison with published dependable findings in specific instances of the model described in the article.In addition,the influence of parameters such as flexoelectric effect,nonlocal and length scale parameters,elastic foundation stiffness coefficient,porosity coefficient,and boundary conditions on the static bending response of the nanoshell is detected and comprehensively studied.The findings of this study have practical implications for the efficient design and control of comparable systems,such as micro-electromechanical and nano-electromechanical devices.
基金supported by National Natural Science Foundation of China(Project No.51878156,received by Wen-Wei Wang) and EPC Innovation Consulting Project for Longkou Nanshan LNG Phase I Receiving Terminal(Z2000LGENT0399,received by Wen-Wei Wang and ZhaoJun Zhang).
文摘This study aimed to investigate the moment redistribution in continuous glass fiber reinforced polymer(GFRP)-concrete composite slabs caused by concrete cracking and steel bar yielding in the negative bending moment zone.An experimental bending moment redistribution test was conducted on continuous GFRP-concrete composite slabs,and a calculation method based on the conjugate beam method was proposed.The composite slabs were formed by combining GFRP profiles with a concrete layer and supported on steel beams to create two-span continuous composite slab specimens.Two methods,epoxy resin bonding,and stud connection,were used to connect the composite slabs with the steel beams.The experimental findings showed that the specimen connected with epoxy resin exhibited two moments redistribution phenomena during the loading process:concrete cracking and steel bar yielding at the internal support.In contrast,the composite slab connected with steel beams by studs exhibited only one-moment redistribution phenomenon throughout the loading process.As the concrete at the internal support cracked,the bending moment decreased in the internal support section and increased in the midspan section.When the steel bars yielded,the bending moment further decreased in the internal support section and increased in the mid-span section.Since GFRP profiles do not experience cracking,there was no significant decrease in the bending moment of the mid-span section.All test specimens experienced compressive failure of concrete at the mid-span section.Calculation results showed good agreement between the calculated and experimental values of bending moments in the mid-span section and internal support section.The proposed model can effectively predict the moment redistribution behavior of continuous GFRP-concrete composite slabs.
基金supported by the Project on Excellent Post-Graduate Dissertation of Hohai University,Nanjing,China(422003508)the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(SJCX23_0187+2 种基金422003287)the National Natural Science Foundation of China(52250410359)Young Elite Scientists Sponsorship Program by Jiangsu Provincial Association for Science and Technology(TJ-2023-043).
文摘When the upper chord beam of the beam-string structure(BSS)is made of concrete-filled steel tube(CFST),its overall stiffness will change greatly with the construction of concrete placement,which will have an impact on the design of the tensioning plans and selection of control measures for the BSS.In order to accurately obtain the bending stiffness of CFST beam and clarify its impact on the mechanical properties of composite BSS during con-struction,the influence of some factors such as height-width ratio,wall thickness of steel tube,elasticity modulus of concrete,and friction coefficient on the bending stiffness are analyzed parametrically by the numerical simula-tion technology based on an actual project.The calculation formula of the equivalent bending stiffness of CFST is also established through mathematical statistical simulation.Then,the equivalent bending stiffness is introduced into the construction and use stages of the composite BSS,respectively,and the mechanical properties such as prestress-tensioning control value,structural deformation,and internal force of key members are comparatively analyzed when adopting two different construction plans.Moreover,the optimal construction plan of concrete placementfirst and then prestress-tensioning is proposed.
基金supported by the National Natural Science Foundation of China(Grant No.52071051)the(Key)Foundation of Xi'an Key Laboratory of High-Performance Titanium Alloy(No.NIN-HTL-2022-ZD01).
文摘Ti-Mo-O alloys were used to analyze the effect of Mo and O contents on the mechanical compatibility and biocompatibility.The bending modulus,bending yield strength and springback ratio of the alloys were evaluated by using three-point bending tests and bending load-unloading tests.The biocompatibility was investigated by the adhesion,proliferation and the alkaline phosphatase(ALP)activity of mouse osteoblast-like cells(MC3T3-E1).The results showed that the bending modulus and bending yield strength first were increased and then decreased with the increase in Mo content,while the springback ratio exhibited an opposite trend to the bending modulus.With the increase in O content,the bending modulus remained almost constant,while the bending yield strength was increased.The springback ratio exhibited a similar trend to the bending yield strength.The in vitro biological experiments showed that the Ti-Mo-O alloys had excellent biocompatibility due to the formed stable oxide films on their surface.With the increase in O and Mo contents,the TiO_(2)-MoO_(2)oxide film became denser.Combining with mechanical compatibility and biocompatibility,the Ti-15Mo-0.2O and Ti-15Mo-0.3O alloys were more suitable for the biomedical application of spinal fixation device.
基金supported by the Fundamental Research Funds for the Central Universities(No.2024JBZX017)。
文摘Fiber Bragg grating(FBG)sensors are extensively used in various sensing applications due to their high sensitivity.However,they are inherently sensitive to both strain and temperature,with a cross-sensitivity problem,making it impossible to simultaneously monitor these two parameters using the Bragg wavelength shifts of a single uniform FBG.In this study,we bend the FBG pigtail to cause bending loss.The peak power of the FBG is used as the second characterization quantity.Our experimental results show that the Bragg wavelength sensitivities to strain(K_(ε))and temperature(K_(T))are 0.17 pm/ue and 16.5 pm/℃,respectively.Additionally,the peak power sensitivities to strain(P_(ε))and temperature(P_(T))are-0.00202 dBm/μεand-0.06 dBm/℃,respectively.The linear correlation coefficients for these measurements are all above 0.996.In this way,it is possible to simultaneously measure both strain and temperature using a single uniform FBG.
基金supported by the National Natural Science Foundation of China(Nos.52272362,U20A20275)the Technology Innovation and Application Development Special Key Project of Chongqing City,China(No.CSTB2022TIAD-KPX0035).
文摘The bending collapse and energy absorption of 7003 aluminum alloy bumper beams under four aging conditions(pre-aging,under-aging,peak-aging,and over-aging)were investigated through three-point bending tests.Microstructural characterization was performed using scanning electron microscopy and transmission electron microscopy.Based on the Swift−Hockett−Sherby constitutive model combined with the Gurson−Tvergaard−Needleman damage model,the plastic response and fracture behavior of the 7003 aluminum alloy under uniaxial tension and three-point bending were accurately predicted.The results showed that the peak bending force of the beams was proportional to the strength under different aging states,while stress triaxiality governed the cracking failure.Pre-aged and under-aged beams resisted cracking until reaching 250 mm displacement due to stress transition from tensile to compression on the bottom surface.The under-aged beam exhibited optimal energy absorption(7.86 kJ)and a higher peak force(38.75 kN).
文摘Powered fight in birds is reliant on feathers forming an aerodynamic surface that resists air pressures.Many basic aspects of feather functionality are unknown,which hampers our understanding of wing function in birds.This study measured the dimensions of primary and secondaryfight feathers of 19 species of parrots.The maximum force the feathers could withstand from below was also measured to mimic the pressuresexperienced during a downstroke.The analysis tested whether:(1)feather dimensions differed along the wing and among secondary and primary remiges;(2)the force that feathers could withstand varied among the remiges;and(3)there would be isometric relationships with bodymass for feather characteristics.The results show that body mass signifcantly affected vane width,rachis thickness,maximum force,and ultimate bending moment,but the relationship for feather length only approached signifcance.Many of the proximal secondary feathers showedsignifcantly lower values relative to the frst primary,whereas for distal primaries the values were greater.There were isometric relationships forforce measurements of primary and secondary feathers with body mass,but there was positive allometry for feather lengths and vane widths.The forces feathers can withstand vary along the wing may be a proxy for the aerodynamic properties of the feathers in situ.Broader taxonomicstudies that explore these topics are required for other species representing a range of different orders.A better understanding of the functionality of feathers will improve our understanding of how avian fight works particularly considering the variety in fight style and wing shape in birds.
基金supported by the National Research Foundation of Korea(NRF)grants funded by the Korea government(MSIT)(nos.RS-2024-00351052 and 202300212657).
文摘This study investigates the influence of initial crystallographic texture on the deformation mechanisms during three-point bending of AZ31 Mg alloy sheets.Three distinct orientations are examined by using the following bending specimens:(i)the normal direction(ND)sample,where the c-axes are predominantly aligned along the specimen thickness,(ii)the rolling direction(RD)sample,where the c-axes are mostly aligned along the longitudinal direction,and(iii)the 45 sample,where the c-axes are tilted at approximately 45°from both the thickness and longitudinal directions.The bending properties vary significantly depending on the initial texture,thereby affecting the strain accommodation and dominant deformation modes.The ND sample exhibits the lowest bendability due to its unfavorable orientation for{10–12}extension twinning and basal slip,which results in poor strain accommodation and early crack initiation in the outer tensile side.By comparison,the RD sample demonstrates an approximately 22.1%improvement,with extensive{10–12}extension twinning in the outer tensile zone.Meanwhile,the 45 sample exhibits the highest bendability(approximately 75.7%greater than that of the ND sample)due to sustained activation of both basal slip and{10–12}extension twinning,promoting uniform strain distribution and delaying fracture.Detailed electron backscatter diffraction analysis reveals that the 45 sample retains favorable crystallographic orientations for basal slip throughout bending,minimizing strain localization and enhancing the bendability.These findings highlight the importance of tailoring the initial texture in order to optimize the bending properties of Mg alloy sheets,and provide valuable insights for improving the manufacturability of Mg-based structural components.
基金funded by National Natural Science Foundation of China(22378241)。
文摘To improve the rigidity and flexibility of conventional grouting materials,one visionary approach is to replace Portland cement with a composite cementitious system containing circulating fluidized bed fly ash(CFBFA)and calcium carbide slag(CS),while adding ethylene-vinyl acetate(EVA)copolymer and CO_(2)as modifiers to enhance its properties.In this research,CFBFA and CS assumed the role of cementitious constituents,with EVA and CO_(2)serving as the modifying agent.A comprehensive exploration of the mechanism underlying the CO_(2)+EVA modified composite cementitious system was undertaken,delving into the differences of its compressive,bending,and flexural strengths.The addition of CO_(2)further improved the flexibility and rigidity of the materials and effectively improve the material's microstructure.It was worth noting that when CO_(2)+EVA co-modified CFBFA-CS composite cementitious materials,the flexibility and rigidity of the cementitious materials were significantly enhanced,and the bending strength,flexural strength and compressive strength were significantly increased by 48.76%,166.7%and 40.56%,respectively,and the 28 d density was reduced by 6.91%.These results provided a theoretical basis for the realization of avant-garde cementitious materials with functional properties.
基金supported by the National Natural Science Foundation of China(Grant No.52475277)2022 Guangxi University Young and Middle-aged Teachers’Basic Research Ability Improvement Project(Grant No.2022KY0781)Scientific Research Funds of Guilin University of Aerospace Technology(Grant No.XJ22KT29).
文摘This research investigates the bending response of folded multi-celled tubes(FMTs)fabricated by folded metal sheets.A three-point bending test for FMTs with circular and square sections is designed and introduced.The base numerical models are correlated with physical experiments and a static crashworthiness analysis of six FMT configurations to assess their energy absorption characteristics.The influences of thickness,sectional shape,and load direction on the bending response are studied.Results indicate that increasing the thickness of the tube and radian of the inner tube enhances the crashworthiness performance of FMT,yielding a 20.50%increase in mean crushing force,a 55.53%increase in specific energy absorption,and an 18.05%decrease in peak crushing force compared to traditional multi-celled tubes(TMTs).A theoretical analysis of the specific energy absorption indicates that FMTs outperform TMTs,particularly when the peak crushing force is prominent.This study highlights the innovative and practical potential of FMTs to improve the crashworthiness of thin-walled structures.
文摘The present study investigates the non-isothermal flow and energy distribution through a loosely bent rectangular duct using a spectral-based numerical approach over a wide range of the Dean number 0<Dn≤3000.Unlike previous research,this work offers novel insights by conducting a grid-point-specific velocity analysis and identifying new bifurcation structures.The study reveals how centrifugal and buoyancy forces interact to produce steady,periodic,and chaotic flow regimes significantly influencing heat transfer performance.The Newton-Raphson method is employed to explore four asymmetric steady branches,with vortex solutions ranging from 2-to 12 vortices.Unsteady flow characteristics are analyzed exquisitely by performing time-advancement of the solutions and the flow regimes are shown as a percentage of total flow with longitudinal vortex generation.Axial flow,secondary flow,and temperature profiles have been depicted in accordance with Dn to wander the flow pattern,and it is predicted that the time-dependent flow(TDF)consists of asymmetric 2-to 10-vortex solutions.The significant findings of this study include the axial displacement of the circulations due to the influence of the time-varying temperature dispersal applied along the wall.Chaotic flows,which dominate the higher Dean number range,are shown to enhance heat convection due to increased fluid mixing.A detailed comparison with prior research demonstrates the advantages of this approach,particularly in capturing complex non-linear behaviors.The findings of this study provide practical guidelines for optimizing duct designs to maximize heat transfer and suggest future research directions,such as using nanofluids or studying Magneto-hydrodynamics in the same configuration.
基金supported by State Key Laboratory for Geo Mechanics and Deep Underground Engineering,China University of Mining&Technology,Beijing(XD2021021)the National Natural Science Foundation of China(Nos.52075325,51975365,and 52011540403)。
文摘The relatively insufficient knowledge of the deformation behavior has limited the wide application of the lightest structure material-Mg alloys.Among others,bending behavior is of great importance because it is unavoidably involved in various forming processes,such as folding,stamping,etc.The hexagonal close-packed structure makes it even a strong texture-dependent behavior and even hard to capture and predict.In this regard,the bending behaviors are investigated in terms of both experiments and simulations in the current work.Bending samples with longitudinal directions inclined from the transverse direction by different angles have been prepared from an extruded AZ31 plate,respectively.The moment-curvature curves and strain distribution have been recorded in the four-point bending tests assisted with an in-situ digital image correlation(DIC)system.A crystal-plasticity-based bending-specific approach named EVPSC-BEND was applied to bridge the mechanical response to the microstructure evolution and underlying deformation mechanisms.The flow stress,texture,twin volume fraction,stress distribution,and strain distribution evolve differently from sample to sample,manifesting strong texture-dependent bending behaviors.The underlying mechanisms associated with this texture dependency,especially the occurrence of both twinning and detwinning during the monotonic bending,are carefully discussed.Besides,the simulation has been conducted to reveal the moment-inclination angle relation of the investigated AZ31 extruded plate in terms of the polar coordinate,which intuitively shows the texture-dependent behaviors.Specifically,the samples with longitudinal directions parallel to the extruded direction bear the biggest initial yielding moment.
基金Open Fund of Badong National Observation and Research Station of Geohazards,Grant/Award Number:BNORSG202315Key R&D Program of Xinjiang Uygur Autonomous Region,Grant/Award Number:2021B03004-3+1 种基金National Natural Science Foundation of China,Grant/Award Numbers:42207169,U22A20569Natural Science Foundation of Jiangsu Province,Grant/Award Number:BK20221126。
文摘The shear characteristics of bolted rock joints are crucial for the stability of tunneling and mining,particularly in deep underground engineering,where rock bolt materials are exposed to high stress,water pressure,and engineering disturbance.However,due to the complex interaction between bolted rock joints and various geological contexts,many challenges and unsolved problems arise.Therefore,more investigation is needed to understand the shear performance of bolted joints in the field of deep underground engineering.This study presents a comprehensive review of research findings on the responses of bolted joints subjected to shearing under different conditions.As is revealed,the average shear strength of bolted rock joints increases linearly with the normal stress and increases with the compressive strength of rock until it reaches a stable value.The joint roughness coefficient(JRC)affects the contact area,friction force,shear strength,bending angle,and axial force of bolted rock joints.A mathematical function is proposed to model the relationship between JRC,normal load,and shear strength.The normal stress level also influences the deformation model,load-carrying capacity,and energy absorption ratio of bolts within bolted rock joints,and can be effectively characterized by a two-phase exponential equation.Additionally,the angle of the bolts affects the ratio of tensile and shear strength of the bolts,as well as the mechanical behavior of both bolted rock joints and surrounding rock,which favors smaller angles.This comprehensive review of experimental data on the shear behavior of bolted rock joints offers valuable theoretical insights for the development of advanced shear devices and further pertinent investigations.
基金supported by the National Natural Science Foundation of China(Nos.52275022,52175015 and U2037603)the Natural Science Foundation of Jiangsu Province,China(Nos.BK20222011 and BK20230093)the State Key Laboratory of Mechanics and Control for Aerospace Structures,China(No.MCAS-S-0223G01)。
文摘Piezoelectric active vibration control holds paramount importance in space structures.An embedded piezoelectric actuator with a sandwich configuration is proposed,which enhances control accuracy by integrating various components.Firstly,the electromechanical coupling characteristics of the actuator are revealed,and the model is established.Secondly,the equivalent model of a cylindrical cantilever beam is investigated as the object,and the feasibility of the vibration control of the actuator is verified by simulation.Finally,the prototype comprised of two actuators,which respectively use the proposed embedded actuators for producing the vibration and suppressing the vibration,is developed,and the measurement system is constructed.Experimental results demonstrate the excellent control efficiency in two orthogonal directions,achieving a minimum vibration amplitude control of 0.00102 mm and a maximum vibration control of-42.74 d B.The integrated structure offers fast response,lightness,adaptability,and high control efficiency,which is conducive to enhancing the vibration control.
基金financially supported by the National Natural Science Foundation of China(Grant No.52471301)the Fujian Province Transportation Science and Technology Project(Grant No.JC202302)the Zhejiang Provincial Natural Science Foundation of China(Grant No.LY24E090003).
文摘Buckling failure in submarine cables presents a prevalent challenge in ocean engineering.This work aims to explore the buckling behavior of umbilical cables with damaged sheaths subjected to compression and bending cyclic loads.A finite element model is devised,incorporating a singular armor wire,a rigid core,and a damaged sheath.To scrutinize the buckling progression and corresponding deformation,axial compression and bending cyclic loads are introduced.The observations reveal that a reduction in axial compression results in a larger number of cycles before buckling ensues and progressively shifts the buckling position toward the extrados and fixed end.Decreasing the bending radius precipitates a reduction in the buckling cycle number and minimizes the deformation in the armor wire.Furthermore,an empirical model is presented to predict the occurrence of birdcage buckling,providing a means to anticipate buckling events and to estimate the requisite number of cycles leading to buckling.
基金financially supported by the National Natural Science Foundation of China(Nos.62474107 and 52032012)the National Key Research and Development Program of China(Nos.2022YFA1205300 and 2022YFA1205304).
文摘Piezoelectric ceramic bending actuators play a pivotal role in various high-tech applications.As a new strategy for fabricating bending actuators,constructing defect dipole concentration gradient has emerged as an effective strategy for boosting electro-bending displacement,yet achieving reproducibility remains challenging due to the uncontrollable alkali volatilization.Herein we propose a new strategy to fabricate barium-doped(K,Na)NbO_(3) piezoelectric bending actuators with controllable gradient distribution of highly stable<110>-oriented(V_(K/Na)'-V_(O)··)defect dipoles,achieving a centimeter-level displacement performance of 1.2 cm under±200 V sinusoidal AC excitations.Samples with defect gradient design but lower oxygen vacancy content exhibit larger bending displacement and excellent fatigue stability without leakage conduction,confirming that the defect dipole concentration gradient,rather than oxygen vacancy migration drives the large bending deformation.Experimental analysis combined with phase-field simulations uncovers that the delicate concentration design of<110>-oriented defect dipoles within orthorhombic stripe domains plays crucial roles in controllable and stable displacement output.We validate the feasibility of the bending actuators in piezoelectric haptic feedback and piezoelectric micro-pump applications,providing new insights into the design of piezoceramic actuators.
