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
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
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
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
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
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 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
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
With the rapid development of flexible electronics,the tactile systems for object recognition are becoming increasingly delicate.This paper presents the design of a tactile glove for object recognition,integrating 243...With the rapid development of flexible electronics,the tactile systems for object recognition are becoming increasingly delicate.This paper presents the design of a tactile glove for object recognition,integrating 243 palm pressure units and 126 finger joint strain units that are implemented by piezoresistive Velostat film.The palm pressure and joint bending strain data from the glove were collected using a two-dimensional resistance array scanning circuit and further converted into tactile images with a resolution of 32×32.To verify the effect of tactile data types on recognition precision,three datasets of tactile images were respectively built by palm pressure data,joint bending strain data,and a tactile data combing of both palm pressure and joint bending strain.An improved residual convolutional neural network(CNN)model,SP-ResNet,was developed by light-weighting ResNet-18 to classify these tactile images.Experimental results show that the data collection method combining palm pressure and joint bending strain demonstrates a 4.33%improvement in recognition precision compared to the best results obtained by using only palm pressure or joint bending strain.The recognition precision of 95.50%for 16 objects can be achieved by the presented tactile glove with SP-ResNet of less computation cost.The presented tactile system can serve as a sensing platform for intelligent prosthetics and robot grippers.展开更多
The effects of various hot deformation states on the evolution of microstructures and mechanical properties in diffusion bonded TC4 alloys were investigated using the hot bending of thick plates.Finite element simulat...The effects of various hot deformation states on the evolution of microstructures and mechanical properties in diffusion bonded TC4 alloys were investigated using the hot bending of thick plates.Finite element simulations were conducted to characterize the deformation states during bending at 750℃ with angles of 17°and 32°.The microstructures and mechanical properties of the bonding interface were then analyzed.The joint subjected to uniaxial stress exhibited the highest ultimate tensile strength,which was attributed to the significant accumulation of dislocation density and the low-angle grain boundaries within the grains.The texture strengthening in the basal{0001}plane was also observed,along with a relatively low Schmid factor corresponding to the primary slip systems aligned with the deformation direction.In contrast,the joint under stress-free conditions showed a slip direction that was less favorable for deformation,resulting in an ultimate tensile strength higher than that of the joint under biaxial stress conditions.展开更多
The fracture behavior of natural fracture in the geological reservoir subjected to filling property,affects the crack initiation and propagation under stress perturbation.Partial filling flaws were intermediate betwee...The fracture behavior of natural fracture in the geological reservoir subjected to filling property,affects the crack initiation and propagation under stress perturbation.Partial filling flaws were intermediate between open fractures and filled fractures,the fracture response may be worth exploring.In this work,the effect of the filling property of sandstone with partial filling flaws on the fracture behavior was systematically investigated based on three-point bending tests and the numerical approach of discrete element method(DEM).In the laboratory,semi-circular three-point bending tests were carried out with partial filling flaws of various filling strengths.Based on this,numerical simulations were used to further investigate the effect of the filling ratio and the inclination of the partial filling flaw on the mechanical and fracture responses,and the effect of the partial filling flaw under mixed-mode loading on the fracture mechanism was elucidated coupled with acoustic emission(AE)characteristics.The obtained results showed that the increase in filling strength and filling ratio of partial filling flaw led to an increase in peak strength,with a decreasing trend in peak strength with the inclination of partial filling flaw.In terms of crack propagation pattern,the increasing filling strength of the partial filling flaw induced the transformation of the fracture mechanism toward deflection,with a tortuosity path,while the filling ratio and inclination of partial filling flaw led to fracture mechanism change from deflection to penetration and attraction,accompanied with a larger AE event source in filler.Accordingly,the b-value based on the Gutenberg-Richter equation fluctuated between 5 and 4 at low filling ratio and inclination and remained around 5 at high filling ratio and inclination of partial filling flaw.Related results may provide an application prospective for reservoir stimulation using the natural fracture system.展开更多
In the era of Metaverse and virtual reality(VR)/augmented reality(AR),capturing finger motion and force interactions is crucial for immersive human-machine interfaces.This study introduces a flexible electronic skin f...In the era of Metaverse and virtual reality(VR)/augmented reality(AR),capturing finger motion and force interactions is crucial for immersive human-machine interfaces.This study introduces a flexible electronic skin for the index finger,addressing coupled perception of both state and process in dynamic tactile sensing.The device integrates resistive and giant magnetoelastic sensors,enabling detection of surface pressure and finger joint bending.This e-skin identifies three phases of finger action:bending state,dynamic normal force and tangential force(sweeping).The system comprises resistive carbon nanotubes(CNT)/polydimethylsiloxane(PDMS)films for bending sensing and magnetoelastic sensors(NdFeB particles,EcoFlex,and flexible coils)for pressure detection.The inward bending resistive sensor,based on self-assembled microstructures,exhibits directional specificity with a response time under 120 ms and bending sensitivity from 0°to 120°.The magnetoelastic sensors demonstrate specific responses to frequency and deformation magnitude,as well as sensitivity to surface roughness during sliding and material hardness.The system’s capability is demonstrated through tactile-based bread type and condition recognition,achieving 92%accuracy.This intelligent patch shows broad potential in enhancing interactions across various fields,from VR/AR interfaces and medical diagnostics to smart manufacturing and industrial automation.展开更多
Two cross⁃sectional configurations of thin⁃walled square tubes partially filled with lightweight metallic foams are proposed,and termed as double⁃cell configuration partially filled with foam(DC⁃PF)and double⁃tube con...Two cross⁃sectional configurations of thin⁃walled square tubes partially filled with lightweight metallic foams are proposed,and termed as double⁃cell configuration partially filled with foam(DC⁃PF)and double⁃tube configuration partially filled with foam(DT⁃PF),respectively.The bending crashworthiness is investigated based on three⁃point bending tests using finite element ABAQUS/Explicit code.The two key mechanical indicators including Crash Load Efficiency(CLE)and Specific Energy Absorption(SEA)are introduced to evaluate the effect of foams in comparison with empty square tubes and fully filled square tubes.The numerical results show that the two partially filled configurations,especially DT⁃PF,display dramatically excellent bending crashworthiness compared with empty and fully filled square tubes.There exists a foam density threshold,beyond which the CLE of DT⁃PF achieves a maximum constant.In addition,there seems to be another foam density threshold,beyond which the SEA of DT⁃PF gets to the maximum value.It is also shown that the foam density threshold corresponding to the maximum SEA varies with the thickness of thin⁃walled square tubes.展开更多
In clinical work,many soft medical pipelines are located deep within the body,resulting in a lack of feedback regarding bending or folding conditions,which presents significant challenges for medical staff.To solve th...In clinical work,many soft medical pipelines are located deep within the body,resulting in a lack of feedback regarding bending or folding conditions,which presents significant challenges for medical staff.To solve the problem,this study innovatively designs a flexible bending sensor,which can be attached to the medical pipelines and monitor the bending conditions.Based on a flexible substrate with secondary microstructures copied from champagne rose petals,the interdigital electrodes are designed to enhance the sensitivity of the sensor due to the amplifying effect.A high sensitivity of 2.209%?1in a bending strain range of 8.9%,and a stable repeatability for over 6000 cycles under 1.8%bending strain are achieved by the sensor.By integrating the bending sensor,here,the nasogastric tube,femoral vein catheter,and tracheal intubation are used to demonstrate the sensing performance.Additionally,during the measurement,the sensing signals are processed and transformed to the bending angles simultaneously,enabling the direct visualization of the bending conditions of the pipelines.This work proposes innovative applications for bending sensors in medical technology and establishes a foundation for further research on flexible bending sensors.展开更多
Aiming at solve the difficulty and low dimensional accuracy in bending titanium alloy specimens at room temperature,we proposed a compound energy field(CEF)with laser and ultrasonic forming method.Through the conventi...Aiming at solve the difficulty and low dimensional accuracy in bending titanium alloy specimens at room temperature,we proposed a compound energy field(CEF)with laser and ultrasonic forming method.Through the conventional bending,laser-assisted energy field bending and CEF-assisted bending experiments on TC4 titanium alloy,the effects of bending force,laser-assisted energy field and CEF on the springback angle and fillet radius of TC4 titanium alloy specimens in V-shape bending were analyzed.The impact of the CEF-assisted bending process on the microstructure of TC4 titanium alloy was also investigated.The results show that CEF-assisted bending process has the advantages of high energy density,simple operation process and small influence area of the microstructure performances.It is effective in reducing the springback and fillet radius of bending specimens.Thus,CEF-assisted bending effectively improves the formability and surface quality of titanium alloy specimens.展开更多
Any product must undergo precise manufacturing before use.The damage incurred during the manufacturing process can significantly impact the residual strength of the product post-manufacturing.However,the relationship ...Any product must undergo precise manufacturing before use.The damage incurred during the manufacturing process can significantly impact the residual strength of the product post-manufacturing.However,the relationship between residual bending strength and manufacturing-induced damage remains unclear,despite being a crucial parameter for assessing material service life and performance,leading to a decrease in product performance reliability.This study focuses on investigating the impact of crack generation on residual bending strength through theoretical and experimental analyses of scratching,grinding,and three-point bending.The research first elucidates the forms and mechanisms of material damage through scratch experiments.Subsequently,using resin-bonded and electroplated wheels as case studies,the influence of different process parameters on grinding damage and residual bending strength is explored.The reduction of brittle removal can lead to a 50%–60%decrease in residual bending strength.Lastly,a model is developed to delineate the relationship between processing parameters and the residual bending strength of the product,with the model exhibiting an error margin of less than 11%.This model clearly reveals the effect of crack generation under different process parameters on residual flexural strength.展开更多
The challenge of solving nonlinear problems in multi-connected domains with high accuracy has garnered significant interest.In this paper,we propose a unified wavelet solution method for accurately solving nonlinear b...The challenge of solving nonlinear problems in multi-connected domains with high accuracy has garnered significant interest.In this paper,we propose a unified wavelet solution method for accurately solving nonlinear boundary value problems on a two-dimensional(2D)arbitrary multi-connected domain.We apply this method to solve large deflection bending problems of complex plates with holes.Our solution method simplifies the treatment of the 2D multi-connected domain by utilizing a natural discretization approach that divides it into a series of one-dimensional(1D)intervals.This approach establishes a fundamental relationship between the highest-order derivative in the governing equation of the problem and the remaining lower-order derivatives.By combining a wavelet high accuracy integral approximation format on 1D intervals,where the convergence order remains constant regardless of the number of integration folds,with the collocation method,we obtain a system of algebraic equations that only includes discrete point values of the highest order derivative.In this process,the boundary conditions are automatically replaced using integration constants,eliminating the need for additional processing.Error estimation and numerical results demonstrate that the accuracy of this method is unaffected by the degree of nonlinearity of the equations.When solving the bending problem of multi-perforated complex-shaped plates under consideration,it is evident that directly using higher-order derivatives as unknown functions significantly improves the accuracy of stress calculation,even when the stress exhibits large gradient variations.Moreover,compared to the finite element method,the wavelet method requires significantly fewer nodes to achieve the same level of accuracy.Ultimately,the method achieves a sixth-order accuracy and resembles the treatment of one-dimensional problems during the solution process,effectively avoiding the need for the complex 2D meshing process typically required by conventional methods when solving problems with multi-connected domains.展开更多
Different stress states have a significant influence on the magnitude of the microscopic plastic strain and result in the development of the microstructure evolution.As a result,a comprehensive understanding of the di...Different stress states have a significant influence on the magnitude of the microscopic plastic strain and result in the development of the microstructure evolution.As a result,a comprehensive understanding of the different scale variation on microstructure evolution during bending deformation is essential.The advanced high strength dual-phase(DP1180)steel was investigated using multiscale microstructure-based 3D representative volume element(RVE)modelling technology with emphasis on understanding the relationship between the microstructure,localised stress-strain evolution as well as the deformation characteristics in the bending process.It is demonstrated that the localised development in bending can be more accurately described by microscopic deformation when taking into account microstructural properties.Microstructure-based 3D RVEs from each chosen bending condition generally have comparable localisation properties,whilst the magnitudes and intensities differ.In addition,the most severe localised bands are predicted to occur close to the ferrite and martensite phase boundaries where the martensite grains are close together or have a somewhat sharp edge.The numerically predicted results for the microstructure evolution,shear bands development and stress and strain distribution after 3-point bending exhibit a good agreement with the relevant experimental observations.展开更多
By focusing on the nonlinear bending behavior of functionally graded carbon nanotube-reinforced(FG-CNTR)curved nanobeams under thermal loads while considering size effects,this paper fills the apparent void by compreh...By focusing on the nonlinear bending behavior of functionally graded carbon nanotube-reinforced(FG-CNTR)curved nanobeams under thermal loads while considering size effects,this paper fills the apparent void by comprehensively incorporating the Chen-Yao surface elasticity theory and modified couple-stress theory.A tri-parameter elastic substrate model is introduced,and the temperature dependence of material properties is considered.Through a two-step perturbation technique,the asymptotic solutions for the temperature-deflection relationship are obtained.After that,novel numerical results are provided to explore the impacts of temperature,size effects,geometric characteristics of the curved beams,elastic substrates,properties of the CNT reinforcements,and boundary conditions.The results indicate that surface effects,couple stress effects,and the elastic foundation enhance the bending stiffness of FG-CNTR curved nanobeams.By considering both size effect theories,this study provides a more comprehensive and precise description of the nonlinear bending of FG-CNTR curved nanobeams under thermal loads.展开更多
The effects of deep cryogenic-cycling treatment(DCT)on the mechanical properties,soft magnetic properties,and atomic scale structure of the Fe_(73.5)Si_(13.5)B_(9)Nb_(3)Cu_(1)amorphous nanocrystalline alloy were inves...The effects of deep cryogenic-cycling treatment(DCT)on the mechanical properties,soft magnetic properties,and atomic scale structure of the Fe_(73.5)Si_(13.5)B_(9)Nb_(3)Cu_(1)amorphous nanocrystalline alloy were investigated.The DCT samples were obtained by subjecting the as-annealed samples to a thermal cycling process between the temperature of the supercooled liquid zone and the temperature of liquid nitrogen.Through flat plate bending testing,hardness measurements,and nanoindentation experiment,it is found that the bending toughness of the DCT samples is improved and the soft magnetic properties are also slightly enhanced.These are attributed to the rejuvenation behavior of the DCT samples,which demonstrate a higher enthalpy of relaxation.Therefore,DCT is an effective method to enhance the bending toughness of Fe-based amorphous nanocrystalline alloys without degrading the soft magnetic properties.展开更多
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).
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.
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 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 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.
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supported by the Key Research and Development Program of Shaanxi Province(No.2024 GX-YBXM-178)the Shaanxi Province Qinchuangyuan“Scientists+Engineers”Team Development(No.2022KXJ032)。
文摘With the rapid development of flexible electronics,the tactile systems for object recognition are becoming increasingly delicate.This paper presents the design of a tactile glove for object recognition,integrating 243 palm pressure units and 126 finger joint strain units that are implemented by piezoresistive Velostat film.The palm pressure and joint bending strain data from the glove were collected using a two-dimensional resistance array scanning circuit and further converted into tactile images with a resolution of 32×32.To verify the effect of tactile data types on recognition precision,three datasets of tactile images were respectively built by palm pressure data,joint bending strain data,and a tactile data combing of both palm pressure and joint bending strain.An improved residual convolutional neural network(CNN)model,SP-ResNet,was developed by light-weighting ResNet-18 to classify these tactile images.Experimental results show that the data collection method combining palm pressure and joint bending strain demonstrates a 4.33%improvement in recognition precision compared to the best results obtained by using only palm pressure or joint bending strain.The recognition precision of 95.50%for 16 objects can be achieved by the presented tactile glove with SP-ResNet of less computation cost.The presented tactile system can serve as a sensing platform for intelligent prosthetics and robot grippers.
基金the financial support from Fundamental Research Funds for the Central Universities,China(No.YWF-23-L-1012)the National Natural Science Foundation of China(No.52005020).
文摘The effects of various hot deformation states on the evolution of microstructures and mechanical properties in diffusion bonded TC4 alloys were investigated using the hot bending of thick plates.Finite element simulations were conducted to characterize the deformation states during bending at 750℃ with angles of 17°and 32°.The microstructures and mechanical properties of the bonding interface were then analyzed.The joint subjected to uniaxial stress exhibited the highest ultimate tensile strength,which was attributed to the significant accumulation of dislocation density and the low-angle grain boundaries within the grains.The texture strengthening in the basal{0001}plane was also observed,along with a relatively low Schmid factor corresponding to the primary slip systems aligned with the deformation direction.In contrast,the joint under stress-free conditions showed a slip direction that was less favorable for deformation,resulting in an ultimate tensile strength higher than that of the joint under biaxial stress conditions.
基金supported by the National Key R&D Program of China(Grant No.2022YFE0128300).
文摘The fracture behavior of natural fracture in the geological reservoir subjected to filling property,affects the crack initiation and propagation under stress perturbation.Partial filling flaws were intermediate between open fractures and filled fractures,the fracture response may be worth exploring.In this work,the effect of the filling property of sandstone with partial filling flaws on the fracture behavior was systematically investigated based on three-point bending tests and the numerical approach of discrete element method(DEM).In the laboratory,semi-circular three-point bending tests were carried out with partial filling flaws of various filling strengths.Based on this,numerical simulations were used to further investigate the effect of the filling ratio and the inclination of the partial filling flaw on the mechanical and fracture responses,and the effect of the partial filling flaw under mixed-mode loading on the fracture mechanism was elucidated coupled with acoustic emission(AE)characteristics.The obtained results showed that the increase in filling strength and filling ratio of partial filling flaw led to an increase in peak strength,with a decreasing trend in peak strength with the inclination of partial filling flaw.In terms of crack propagation pattern,the increasing filling strength of the partial filling flaw induced the transformation of the fracture mechanism toward deflection,with a tortuosity path,while the filling ratio and inclination of partial filling flaw led to fracture mechanism change from deflection to penetration and attraction,accompanied with a larger AE event source in filler.Accordingly,the b-value based on the Gutenberg-Richter equation fluctuated between 5 and 4 at low filling ratio and inclination and remained around 5 at high filling ratio and inclination of partial filling flaw.Related results may provide an application prospective for reservoir stimulation using the natural fracture system.
基金supported by the National Natural Science Foundation of China(Grant No.12204271)Shenzhen Science and Technology Program(Grant No.JCYJ20220530141014032)Guangdong Basic and Applied Basic Research Foundation program(Grant No.2022A1515011526),China.
文摘In the era of Metaverse and virtual reality(VR)/augmented reality(AR),capturing finger motion and force interactions is crucial for immersive human-machine interfaces.This study introduces a flexible electronic skin for the index finger,addressing coupled perception of both state and process in dynamic tactile sensing.The device integrates resistive and giant magnetoelastic sensors,enabling detection of surface pressure and finger joint bending.This e-skin identifies three phases of finger action:bending state,dynamic normal force and tangential force(sweeping).The system comprises resistive carbon nanotubes(CNT)/polydimethylsiloxane(PDMS)films for bending sensing and magnetoelastic sensors(NdFeB particles,EcoFlex,and flexible coils)for pressure detection.The inward bending resistive sensor,based on self-assembled microstructures,exhibits directional specificity with a response time under 120 ms and bending sensitivity from 0°to 120°.The magnetoelastic sensors demonstrate specific responses to frequency and deformation magnitude,as well as sensitivity to surface roughness during sliding and material hardness.The system’s capability is demonstrated through tactile-based bread type and condition recognition,achieving 92%accuracy.This intelligent patch shows broad potential in enhancing interactions across various fields,from VR/AR interfaces and medical diagnostics to smart manufacturing and industrial automation.
基金Sponsored by National Natural Science Foundation of China (Grant Nos.12272064 and 12101086)University Natural Science Research Project of Anhui Province (Grant No.KJ2018A0481)+2 种基金Major Project of Basic Science (Natural Science) Research in Jiangsu Universities (Grant Nos.22KJA460001,23KJA580001)Changzhou Science and Technology Plan Project (Grant No.CE20235049)Changzhou Leading Innovative Talents C ultivation Project (Grant No.CQ20220092).
文摘Two cross⁃sectional configurations of thin⁃walled square tubes partially filled with lightweight metallic foams are proposed,and termed as double⁃cell configuration partially filled with foam(DC⁃PF)and double⁃tube configuration partially filled with foam(DT⁃PF),respectively.The bending crashworthiness is investigated based on three⁃point bending tests using finite element ABAQUS/Explicit code.The two key mechanical indicators including Crash Load Efficiency(CLE)and Specific Energy Absorption(SEA)are introduced to evaluate the effect of foams in comparison with empty square tubes and fully filled square tubes.The numerical results show that the two partially filled configurations,especially DT⁃PF,display dramatically excellent bending crashworthiness compared with empty and fully filled square tubes.There exists a foam density threshold,beyond which the CLE of DT⁃PF achieves a maximum constant.In addition,there seems to be another foam density threshold,beyond which the SEA of DT⁃PF gets to the maximum value.It is also shown that the foam density threshold corresponding to the maximum SEA varies with the thickness of thin⁃walled square tubes.
基金supported by the National Natural Science Foundation of China(52105299,52175271,52375287)Science and Technology Development Plan Project of Jilin Province(20240101036JJ)+1 种基金Scientific Research Project of the Education Department of Jilin Province(JJKH20241269KJ)China Postdoctoral Science Foundation(2024M751086).
文摘In clinical work,many soft medical pipelines are located deep within the body,resulting in a lack of feedback regarding bending or folding conditions,which presents significant challenges for medical staff.To solve the problem,this study innovatively designs a flexible bending sensor,which can be attached to the medical pipelines and monitor the bending conditions.Based on a flexible substrate with secondary microstructures copied from champagne rose petals,the interdigital electrodes are designed to enhance the sensitivity of the sensor due to the amplifying effect.A high sensitivity of 2.209%?1in a bending strain range of 8.9%,and a stable repeatability for over 6000 cycles under 1.8%bending strain are achieved by the sensor.By integrating the bending sensor,here,the nasogastric tube,femoral vein catheter,and tracheal intubation are used to demonstrate the sensing performance.Additionally,during the measurement,the sensing signals are processed and transformed to the bending angles simultaneously,enabling the direct visualization of the bending conditions of the pipelines.This work proposes innovative applications for bending sensors in medical technology and establishes a foundation for further research on flexible bending sensors.
基金Funded by the National Natural Science Foundation of China(Nos.52075347,51575364)the Natural Science Foundation of Liaoning Provincial(No.2022-MS-295)。
文摘Aiming at solve the difficulty and low dimensional accuracy in bending titanium alloy specimens at room temperature,we proposed a compound energy field(CEF)with laser and ultrasonic forming method.Through the conventional bending,laser-assisted energy field bending and CEF-assisted bending experiments on TC4 titanium alloy,the effects of bending force,laser-assisted energy field and CEF on the springback angle and fillet radius of TC4 titanium alloy specimens in V-shape bending were analyzed.The impact of the CEF-assisted bending process on the microstructure of TC4 titanium alloy was also investigated.The results show that CEF-assisted bending process has the advantages of high energy density,simple operation process and small influence area of the microstructure performances.It is effective in reducing the springback and fillet radius of bending specimens.Thus,CEF-assisted bending effectively improves the formability and surface quality of titanium alloy specimens.
基金Supported by National Key Research and Development Program of China(Grant No.2023YFB3711100)National Natural Science Foundation of China(Grant Nos.52275458,52275207)Tianjin Municipal Natural Science Foundation(Grant No.22JCZDJC00050)。
文摘Any product must undergo precise manufacturing before use.The damage incurred during the manufacturing process can significantly impact the residual strength of the product post-manufacturing.However,the relationship between residual bending strength and manufacturing-induced damage remains unclear,despite being a crucial parameter for assessing material service life and performance,leading to a decrease in product performance reliability.This study focuses on investigating the impact of crack generation on residual bending strength through theoretical and experimental analyses of scratching,grinding,and three-point bending.The research first elucidates the forms and mechanisms of material damage through scratch experiments.Subsequently,using resin-bonded and electroplated wheels as case studies,the influence of different process parameters on grinding damage and residual bending strength is explored.The reduction of brittle removal can lead to a 50%–60%decrease in residual bending strength.Lastly,a model is developed to delineate the relationship between processing parameters and the residual bending strength of the product,with the model exhibiting an error margin of less than 11%.This model clearly reveals the effect of crack generation under different process parameters on residual flexural strength.
基金supported by the National Natural Science Foundation of China(Grant No.11925204).
文摘The challenge of solving nonlinear problems in multi-connected domains with high accuracy has garnered significant interest.In this paper,we propose a unified wavelet solution method for accurately solving nonlinear boundary value problems on a two-dimensional(2D)arbitrary multi-connected domain.We apply this method to solve large deflection bending problems of complex plates with holes.Our solution method simplifies the treatment of the 2D multi-connected domain by utilizing a natural discretization approach that divides it into a series of one-dimensional(1D)intervals.This approach establishes a fundamental relationship between the highest-order derivative in the governing equation of the problem and the remaining lower-order derivatives.By combining a wavelet high accuracy integral approximation format on 1D intervals,where the convergence order remains constant regardless of the number of integration folds,with the collocation method,we obtain a system of algebraic equations that only includes discrete point values of the highest order derivative.In this process,the boundary conditions are automatically replaced using integration constants,eliminating the need for additional processing.Error estimation and numerical results demonstrate that the accuracy of this method is unaffected by the degree of nonlinearity of the equations.When solving the bending problem of multi-perforated complex-shaped plates under consideration,it is evident that directly using higher-order derivatives as unknown functions significantly improves the accuracy of stress calculation,even when the stress exhibits large gradient variations.Moreover,compared to the finite element method,the wavelet method requires significantly fewer nodes to achieve the same level of accuracy.Ultimately,the method achieves a sixth-order accuracy and resembles the treatment of one-dimensional problems during the solution process,effectively avoiding the need for the complex 2D meshing process typically required by conventional methods when solving problems with multi-connected domains.
基金supported by HBIS Group under the Grant No.IRIS 200506003.
文摘Different stress states have a significant influence on the magnitude of the microscopic plastic strain and result in the development of the microstructure evolution.As a result,a comprehensive understanding of the different scale variation on microstructure evolution during bending deformation is essential.The advanced high strength dual-phase(DP1180)steel was investigated using multiscale microstructure-based 3D representative volume element(RVE)modelling technology with emphasis on understanding the relationship between the microstructure,localised stress-strain evolution as well as the deformation characteristics in the bending process.It is demonstrated that the localised development in bending can be more accurately described by microscopic deformation when taking into account microstructural properties.Microstructure-based 3D RVEs from each chosen bending condition generally have comparable localisation properties,whilst the magnitudes and intensities differ.In addition,the most severe localised bands are predicted to occur close to the ferrite and martensite phase boundaries where the martensite grains are close together or have a somewhat sharp edge.The numerically predicted results for the microstructure evolution,shear bands development and stress and strain distribution after 3-point bending exhibit a good agreement with the relevant experimental observations.
基金supports from the National Natural Science Foundation of China(12102085)the Postdoctoral Science Foundation of China(2023M730504)the Sichuan Province Regional Innovation and Cooperation Project(2024YFHZ0210).
文摘By focusing on the nonlinear bending behavior of functionally graded carbon nanotube-reinforced(FG-CNTR)curved nanobeams under thermal loads while considering size effects,this paper fills the apparent void by comprehensively incorporating the Chen-Yao surface elasticity theory and modified couple-stress theory.A tri-parameter elastic substrate model is introduced,and the temperature dependence of material properties is considered.Through a two-step perturbation technique,the asymptotic solutions for the temperature-deflection relationship are obtained.After that,novel numerical results are provided to explore the impacts of temperature,size effects,geometric characteristics of the curved beams,elastic substrates,properties of the CNT reinforcements,and boundary conditions.The results indicate that surface effects,couple stress effects,and the elastic foundation enhance the bending stiffness of FG-CNTR curved nanobeams.By considering both size effect theories,this study provides a more comprehensive and precise description of the nonlinear bending of FG-CNTR curved nanobeams under thermal loads.
基金supported by Liaoning Joint Fund of NSFC(No.U1908219)。
文摘The effects of deep cryogenic-cycling treatment(DCT)on the mechanical properties,soft magnetic properties,and atomic scale structure of the Fe_(73.5)Si_(13.5)B_(9)Nb_(3)Cu_(1)amorphous nanocrystalline alloy were investigated.The DCT samples were obtained by subjecting the as-annealed samples to a thermal cycling process between the temperature of the supercooled liquid zone and the temperature of liquid nitrogen.Through flat plate bending testing,hardness measurements,and nanoindentation experiment,it is found that the bending toughness of the DCT samples is improved and the soft magnetic properties are also slightly enhanced.These are attributed to the rejuvenation behavior of the DCT samples,which demonstrate a higher enthalpy of relaxation.Therefore,DCT is an effective method to enhance the bending toughness of Fe-based amorphous nanocrystalline alloys without degrading the soft magnetic properties.
