As one of the most widely used personal protective equipment(PPE),body armors play an important role in protecting the human body from the high-velocity impact of bullets or projectiles.The body torso and critical org...As one of the most widely used personal protective equipment(PPE),body armors play an important role in protecting the human body from the high-velocity impact of bullets or projectiles.The body torso and critical organs of the wear may suffer severe behind-armor blunt trauma(BABT)even though the impactor is stopped by the body armor.A type of novel composite material through incorporating shear stiffening gel(STG)into ethylene-vinyl acetate(EVA)foam is developed and used as buffer layers to reduce BABT.In this paper,the protective performance of body armors composed of fabric bulletproof layers and a buffer layer made of foam material is investigated both experimentally and numerically.The effectiveness of STG-modified EVA in damage relief is verified by ballistic tests.In parallel with the experimental study,numerical simulations are conducted by LS-DYNA®to investigate the dynamic response of each component and capture the key mechanical parameters,which are hardly obtained from field tests.To fully describe the material behavior under the transient impact,the selected constitutive models take the failure and strain rate effect into consideration.A good agreement between the experimental observations and numerical results is achieved to prove the validity of the modelling method.The tests and simulations show that the impact-induced deformation on the human body is significantly reduced by using STG-modified EVA as the buffering material.The improvement of protective performance is attributed to better dynamic properties and more outstanding energy absorption capability of the composite foam.展开更多
A convenient approach is proposed for analyzing the ultimate load carrying capacity of concrete filled steel tubular (CFST) arch bridge with stiffening girders. A fiber model beam element is specially used to simulate...A convenient approach is proposed for analyzing the ultimate load carrying capacity of concrete filled steel tubular (CFST) arch bridge with stiffening girders. A fiber model beam element is specially used to simulate the stiffening girder and CFST arch rib. The geometric nonlinearity, material nonlinearity, influence of the construction process and the contribution of prestressing reinforcement are all taken into consideration. The accuracy of this method is validated by comparing its results with experimental results. Finally, the ultimate strength of an abnormal CFST arch bridge with stiffening girders is investigated and the effect of construction method is discussed. It is concluded that the construction process has little effect on the ultimate strength of the bridge.展开更多
Air plasma sprayed thermal barrier coatings(APS-TBCs)saw their wide application in high-temperaturerelated cutting-edge fields.The lamellar structure of APS-TBCs provides a significant advantage on thermal insulation....Air plasma sprayed thermal barrier coatings(APS-TBCs)saw their wide application in high-temperaturerelated cutting-edge fields.The lamellar structure of APS-TBCs provides a significant advantage on thermal insulation.However,short life span is a major headache for APS-TBCs.This is highly related to the property changes and passive behaviors of the coatings during thermal service.Herein,a finite element model was developed to investigate the dynamic stiffening and substrate constraint on total spallation process.Results show that the stiffening accelerates the crack propagation of APS-TBCs.The driving force for crack propagation,which is characterized by strain energy release rate(SERR),is significantly enlarged.Consequently,the crack starts to propagate when the SERR exceeds the fracture toughness.In addition,the changing trends of SERR and crack propagation features are highly associated with temperatures.A higher temperature corresponds to more significant effect of stiffening on substrate constraint.In brief,temperature-dependent stiffening significantly aggravates the substrate constraint effect on APS-TBCs,which is one of the major causes for the spallation.Given that,lowering stiffening degree is essential to maintain high strain tolerance,and to further extend the life span of APS-TBCs.This understanding contributes to the development of advanced TBCs in future applications.展开更多
Electrode stress is one of the main driving forces of electrochemical degradation,which is directly related to battery cycle life,thus attracting great interest.Herein,we propose an in situ method to measure bilayer s...Electrode stress is one of the main driving forces of electrochemical degradation,which is directly related to battery cycle life,thus attracting great interest.Herein,we propose an in situ method to measure bilayer stresses in film-substrate electrodes during electrochemical processes.This method consists of two parts:stress models featuring Li-dependent material modulus and in situ deformation measurements,through which electrode bilayer stresses evolution accompanied by Li-dependent material modulus can be quantitatively characterized.As application of the method,typical silicon-composite and carbon-composite film-substrate electrodes are selected for in situ mechanical measurements and experimental analysis is performed.Results show that silicon material and carbon material exhibit significant,continuous softening and stiffening,respectively.In two film-substrate electrodes,electrode material films experience compressive stress and current collector substrates undergo a tensile-to-compressive conversion across the thickness.Besides,moduli and stresses in both electrodes vary nonlinearly with capacity,presenting non-overlapping paths between lithiation and delithiation.Based on experimental data,we further demonstrate the key role of Li-dependent modulus on electrode stresses,finding that silicon material softening decreases and carbon material stiffening increases electrode stresses.The deficiencies of current stress measurement method based on Stoney equation and the applicability of our method are discussed.展开更多
Stiffening-ribbed-hollow-pipe cast-in place reinforced concrete girderless floor is a new-style hollow girderless floor system. Model experimental researches of simply-supported floor and four-corners bearing floor ha...Stiffening-ribbed-hollow-pipe cast-in place reinforced concrete girderless floor is a new-style hollow girderless floor system. Model experimental researches of simply-supported floor and four-corners bearing floor have been done on this new kind of floor system in this paper. The experiment results show that the floor system has good mechanical property such as high bearing capacity, big rigidity and good tensility. A theoretical method is presented in this paper that the stiffening-ribbed-hollow-pipe girderless floor can be analyzed by being converted equivalently to orthotropic solid slab. It is indicated that the method is correct and reasonable according to the contrast between theoretical calculated results and experimental measured results. The theoretical results coincide with the measured results well.展开更多
To solve the problem that the overlapping parts of a retractable pier column are prone to damage,this paper proposed the reinforcing measure of setting a stiffener ring at the bottom of the steel pipe.To study how the...To solve the problem that the overlapping parts of a retractable pier column are prone to damage,this paper proposed the reinforcing measure of setting a stiffener ring at the bottom of the steel pipe.To study how the stiffener-ring parameters influence the mechanical properties of the pier column.12 scale model specimens(including nine specimens with stiffener-ring widths of 40,50,and 60 mm and three unstiffened comparison specimens)were tested under axial compression.Based on the test results,the specimen load-displacement,load-deflection,and load-strain curves were analyzed,and a finite-element model of a pier column under axial compression was established to determine the optimal stiffener size.The results show that setting a stiffener ring enhances the cooperative working ability between the steel pipe and the internal filling material and restrains the lateral deformation of the pier column,thereby improving the ultimate bearing capacity and overall stability of the pier column.The ultimate bearing capacity of the pier column is related to the width and thickness of the stiffener ring.The optimal size of the stiffener ring of the model pier column is 70 mm in width and 4 mm in thickness.The present research results provide a reference for designing compressible pier columns and column stiffening in mines and have important practical significance.展开更多
A rigid flexible coupling physical model which can represent a flexible spacecraft is investigated in this paper. By applying the mechanics theory in a non-inertial coordinate system,the rigid flexible coupling dynami...A rigid flexible coupling physical model which can represent a flexible spacecraft is investigated in this paper. By applying the mechanics theory in a non-inertial coordinate system,the rigid flexible coupling dynamic model with dynamic stiffening is established via the subsystemmodeling framework. It is clearly elucidated for the first time that,dynamic stiffening is produced by the coupling effect of the centrifugal inertial load distributed on the beamand the transverse vibration deformation of the beam. The modeling approach in this paper successfully avoids problems which are caused by other popular modeling methods nowadays： the derivation process is too complex by using only one dynamic principle; a clearly theoretical explanation for dynamic stiffening can＇t be provided. First,the continuous dynamic models of the flexible beamand the central rigid body are established via structural dynamics and angular momentumtheory respectively. Then,based on the conclusions of orthogonalization about the normal constrained modes,the finite dimensional dynamic model suitable for controller design is obtained. The numerical simulation validations showthat： dynamic stiffening is successfully incorporated into the dynamic characteristics of the first-order model established in this paper,which can indicate the dynamic responses of the rigid flexible coupling system with large overall motion accurately,and has a clear modeling mechanism,concise expressions and a good convergence.展开更多
The dynamics for multi-link spatial flexible manipulator arms is investigated. The system considered here is an N-flexible-link manipulator driven by N DC-motors through N revolute flexiblejoints. The flexibility of e...The dynamics for multi-link spatial flexible manipulator arms is investigated. The system considered here is an N-flexible-link manipulator driven by N DC-motors through N revolute flexiblejoints. The flexibility of each flexible joint is modeled as a linearly elastic torsional spring, and the mass of the joint is also considered. For the flexibility of the link, all of the stretching deformation, bending deformation and the torsional deformation are included. The complete governing equations of motion of the system are derived via the Lagrange equations. The nonlinear description of the deformation field of the flexible link is adopted in the dynamic modeling, and thus the dynamic stiffening effects are captured. Based on this model, a general-purpose software package for dynamic simulation of multi-link spatial flexible manipulator arms is developed. Several illustrative examples are given to validate the algorithm presented in this paper and to indicate that not only dynamic stiffening effects but also the flexibility of the structure has significant influence on the dynamic performance of the manipulator.展开更多
We experienced a very rare complication of colonoscopy,a migration of stiffening tube into the colorectum. We herein introduce a withdrawing method of migrating stiffening tube incidentally inserted into the colorectu...We experienced a very rare complication of colonoscopy,a migration of stiffening tube into the colorectum. We herein introduce a withdrawing method of migrating stiffening tube incidentally inserted into the colorectum.A 65-year-old Japanese woman underwent colonoscopy because of abdominal discomfort. We used stiffening tube to insert the scope to the proximal colon because of her redundant sigmoid colon. When withdrawing the scope,we realized that the tube was fully inside the colorectum.We could not remove the tube instantly, and it reached the splenic flexure, finally. We reinserted the scope through the migrating tube, straightened the scope, and withdrew it holding a slight angle of the scope over the proximal end of the tube. Then, we could safely remove the tube along with the scope through the anus.展开更多
In construction industry, the application of high-performance reinforcement bar is required strongly. Unfortunately, not nearly enough research has been conducted on high-performance steel in comparison with high stre...In construction industry, the application of high-performance reinforcement bar is required strongly. Unfortunately, not nearly enough research has been conducted on high-performance steel in comparison with high strength concrete. This paper describes the effect of high-performance steel as reinforcement steel bar on the tension response and cracking behavior of concrete and fiber-reinforced strain-hardening cement-based composite (SHCC) tension members. High-performance steel is characterized by higher strength in comparison to ASTM A615-06 Grade 60 steel. The tension stiffening effect on high-performance reinforcing bars embedded in cement-based composite prism is investigated experimentally. The variables in the study are types of cement-based composite (conventional concrete, synthetic fiber-reinforced cement composite), yielding strength of steel bars (400MPa and 600MPa), and types of loading (monotonic and repeated tension loading).展开更多
Based on an assumption of parabolic bond stress distribution,a simplified model with quartic polynomial function of the relative slip of steel bar and surrounding concrete for reinforced concrete (RC)tensile member wa...Based on an assumption of parabolic bond stress distribution,a simplified model with quartic polynomial function of the relative slip of steel bar and surrounding concrete for reinforced concrete (RC)tensile member was proposed. The post-cracking behavior as well as tension stiffening effect was considered in the new model. The relative slip of bending member could also be determined through the extension of the new model,which could be applied to obtaining the concentrated rotations at certain sections in order to predict the flexural deformation of RC beam. Several examples of four-point bending RC beams were approached to verify the new model,and the predictions of the flexural deflections of RC beams agreed well with experimental results. The new model can be extended to the application of partially corroded RC beam.展开更多
Compared to the conventional two-tower suspension bridge, the three-tower suspension bridge has obviously different characteristics in structural performance because of the extra middle tower and main span. The constr...Compared to the conventional two-tower suspension bridge, the three-tower suspension bridge has obviously different characteristics in structural performance because of the extra middle tower and main span. The construction sequence for the stiffening girder is significantly different between the three-tower suspension bridge and the two-tower suspension bridge. The tangential angle of the main cable is one of the controlling factors of the stiffening girder erection stage for a suspension bridge. According to 5 feasible cases for the stiffening girder erection scheme in Taizhou Bridge, the research about the tangential angle in each case mentioned above was made, and some factors that should be taken into account for the erection scheme of stiffening girder were pointed out.展开更多
In order to clear constructional design of corner joint, it is necessary to further investi-gate mechanical property of corner joint in gabled frames. Through static test and finite element software analysis of compar...In order to clear constructional design of corner joint, it is necessary to further investi-gate mechanical property of corner joint in gabled frames. Through static test and finite element software analysis of comparing the panel zone with and without inclined stiffener. Some conclusions are given in the article. The load displacement curves show that the capacity of oblique nodes installed within stiffening rib components is enhanced i.e. 40% more than those without stiffening rib nodes. The results reveal that in the gabled frames, the corner node with the inclined stiffening rib can improve the bearing capacity of the specimens. When the extraterritorial flange is tension, the erection of the inclined stiffening rib can prevent structural failure and improve effectually the ductility of the structure.展开更多
Thermal softening is an inevitable process in the physical network.Polyurethane(PU),a typical commercial material,is constructed by physical networks,which undergoes the serious thermal decay on mechanical properties ...Thermal softening is an inevitable process in the physical network.Polyurethane(PU),a typical commercial material,is constructed by physical networks,which undergoes the serious thermal decay on mechanical properties at high temperature.Herein,a physically cross-linked PU with a unique thermal stiffening behavior has been developed by incorporating B–N coordination with reversible B–O bonds.The B–N coordination can significantly improve the mechanical properties of the PU.The reversible B–O bonds(temperature dependent reversible transformation between B–OH and B–O–B)are conducive to constructing more multicoordination macromolecular crosslinking points and more stable B–N coordination bonds at high temperature,endowing the PU with the special thermal stiffening behavior for the first time.Such thermal stiffening behavior compensates for the bond breakage and the network destruction caused by heat,significantly expands the rubbery plateau and delays the entire chain motion of the thermoplastic PU.As a result,the terminal flow occurs at a higher temperature up to 200°C.The modulus retention ratio of the materials is up to 87%even at 145oC,which is much higher than that of the existing PU elastomer with the physical network and even some covalent cross-link PU.Simultaneously,the physical network ensures the recyclability of the PU,and the thermal stiffening behavior is still obtained in recycled PU.This work provides a simple strategy to impart thermal stiffening behavior to the physically crosslinked PU,thereby significantly extending the operating temperature range of thermoplastic PU,which can potentially expand the scopes of PU in applications under harsh conditions.展开更多
In practical design,the joints with outer stiffening ring were used to connect concrete beams and laminated steel tube columns.The seismic behavior of joints with outer stiffening ring with various types was studied b...In practical design,the joints with outer stiffening ring were used to connect concrete beams and laminated steel tube columns.The seismic behavior of joints with outer stiffening ring with various types was studied based on experiments.The bearing capacity,rigidity,ductility,energy dissipation capacity,deformation property and strain distribution of the joints with outer stiffening ring with various types were comprehensively evaluated based on the test results of three specimens under quasistatic cyclic loading and finite element analysis.The test results showed that the failure mode,hysteretic behavior,bearing capacity and rigidity degradation of the joints with outer stiffening ring with various types were nearly identical.Furthermore,the strain distribution of the outer stiffening ring of the three joints was nearly the same.The detailing recommendation for the outer strengthening rings was proposed for the concrete beam-laminated steel tube column joints with outer stiffening ring,in order to ensure the good seismic capacity of the joints.展开更多
The higher risk of vaso-occlusion events and sudden death for sickle-cell trait(SCT)athletes has been speculatively ascribed to SCT red blood cell(RBC)stiffening during strenuous exercise.However,the microenvironmenta...The higher risk of vaso-occlusion events and sudden death for sickle-cell trait(SCT)athletes has been speculatively ascribed to SCT red blood cell(RBC)stiffening during strenuous exercise.However,the microenvironmental changes that could induce the stiffening of SCT RBCs are unknown.To address this question,we measured the mechanical properties of and changes in SCT RBCs under deoxygenated and acidic environments,which are two typical conditions present in the circulation of athletes undertaking strenuous exercise.The results reveal that SCT RBCs are inherently stiffer than RBCs from non-SCT healthy subjects,and a lower pH further stiffens the SCT cells.Furthermore,at both normal and low pH levels,deoxygenation was found to not be the cause of the stiffness of SCT RBCs.This study confirms that the stiffening of SCT RBCs occurs at a low pH and implies that SCT RBC stiffening could be responsible for vaso-occlusion in SCT athletes during strenuous exercise.展开更多
The penetration of ogival-nosed projectiles into ship plates represents a complex impact dynamics issue essential for analyzing structural failuremechanisms.Although stiffenedplates are vital in ship construction,fews...The penetration of ogival-nosed projectiles into ship plates represents a complex impact dynamics issue essential for analyzing structural failuremechanisms.Although stiffenedplates are vital in ship construction,fewstudies have addressed the issue of model equivalence under penetration loading.This study employs numerical simulation to validate an experiment with an ogival-nosed projectile penetrating a Q345 steel plate.Four equivalent stiffened plate methods are proposed based on the area,flexural modulus,moment of inertia,and thickness.The results indicate that thickness equivalence(DM4)is unsuitable for penetration-loaded stiffened plates,except under low-speed,nonpenetrating through impacts,and yields less accuracy than DM1/DM3.DM1,DM2,and DM3 each perform optimally with specific velocity ranges:DM1 at very low(critical)and high velocities,DM3 at low velocities,and DM2 at high speeds.Furthermore,in penetration scenarios,T-shaped stiffeners can be replacedwith rectangular ones,as both exhibit similar failure behaviors and deflection trends,simplifying the design while preserving key structural characteristics.These findings provide valuable insights into the design of protective ship structures.展开更多
The increasing demand to decrease manufacturing costs and weight reduction is driving the aircraft industry to change the use of conventional riveted stiffened panels to integral stiffened panels(ISP)for aircraft fuse...The increasing demand to decrease manufacturing costs and weight reduction is driving the aircraft industry to change the use of conventional riveted stiffened panels to integral stiffened panels(ISP)for aircraft fuselage structures.ISP is a relatively new structure in aircraft industries and is considered the most significant development in a decade.These structures have the potential to replace the conventional stiffened panel due to the emergence of manufacturing technology,including welding,high-speed machining(HSM),extruding,and bonding.Although laser beam welding(LBW)and friction stir welding(FSW)have been applied in aircraft companies,many investigations into ISP continue to be conducted.In this review article,the current state of understanding and advancement of ISP structure is addressed.A particular explanation has been given to(a)buckling performance,(b)fatigue performance of the ISP,(c)modeling and simulation aspects,and(d)the impact of manufacturing decisions in welding processes on the final structural behavior of the ISP during service.Compared to riveted panels,machined ISP had a better compressive buckling load,and FSW integral panels had a lower buckling load than riveted panels.Compressive residual stress decreased the stress intensity factor(SIF)rates,slowing down the growth of fatigue cracks as occurred in FSW and LBW ISP.展开更多
The influences of different factors,including whether the transverse frames are actually built,longitudinal and transverse welding residual stresses,and unloaded edge boundaries,on the ultimate strength and failure mo...The influences of different factors,including whether the transverse frames are actually built,longitudinal and transverse welding residual stresses,and unloaded edge boundaries,on the ultimate strength and failure mode of a real hull bottom full-scale stiffened plate under axial compression and lateral pressure are investigated via numerical analysis.Result shows that the failure mode of the stiffened plate under axial compression is the tripping of the stiffeners.Whether transverse frames are built has little effect on the ultimate strength of the stiffened plate under axial compression,which can be replaced by the degree of freedom constraint.However,when lateral pressure is present,the transverse frame cannot be simply replaced by a free-degree constraint.The longitudinal residual stress has a greater effect on the ultimate strength,whereas the effect of the transverse residual stress is smaller.Stronger unloaded edge boundary conditions can slightly enhance the stiffness and ultimate strength of the stiffened plate.Under combined axial compression and lateral pressure,the failure mode of stiffened plates changes from the tripping of stiffeners to beam-column failure,as the lateral pressure increases.The ability of stiffened plates in which transverse frames are actually built out to resist beam-column shape deformation becomes weaker with lower ultimate strength.Stronger unloaded edge boundary conditions can improve the ability of stiffened plates to resist beam-column deformation and increase the ultimate strength.展开更多
The buckling behavior of stiffened panels is significantly influenced by material and geometric defects,making it a critical factor in ensuring structural integrity and safety.These panels are widely used in mechanica...The buckling behavior of stiffened panels is significantly influenced by material and geometric defects,making it a critical factor in ensuring structural integrity and safety.These panels are widely used in mechanical,aerospace,marine,and civil engineering applications due to their ability to enhance bending stiffness with minimal additional weight.Under high loads or stress concentrations,localized structural failures can initiate global buckling in stiffened panels.This study investigates how such defects affect the critical buckling load,stiffness,and thickness of stiffened panels.Two finite element analyses were conducted:a linear analysis to identify the initial buckling mode and a nonlinear analysis using the Riks algorithm in Abaqus CAE,incorporating localized imperfections.The simulations show that material and geometric defects can reduce buckling resistance depending on their severity.展开更多
基金the National Natural Science Foundation of China(Grant Nos.12072356 and 12232020)the Science and Technology on Transient Impact Laboratory(Grant No.6142606221105)the Beijing Municipal Science and Technology Commission(Grant No.Z221100005822006).
文摘As one of the most widely used personal protective equipment(PPE),body armors play an important role in protecting the human body from the high-velocity impact of bullets or projectiles.The body torso and critical organs of the wear may suffer severe behind-armor blunt trauma(BABT)even though the impactor is stopped by the body armor.A type of novel composite material through incorporating shear stiffening gel(STG)into ethylene-vinyl acetate(EVA)foam is developed and used as buffer layers to reduce BABT.In this paper,the protective performance of body armors composed of fabric bulletproof layers and a buffer layer made of foam material is investigated both experimentally and numerically.The effectiveness of STG-modified EVA in damage relief is verified by ballistic tests.In parallel with the experimental study,numerical simulations are conducted by LS-DYNA®to investigate the dynamic response of each component and capture the key mechanical parameters,which are hardly obtained from field tests.To fully describe the material behavior under the transient impact,the selected constitutive models take the failure and strain rate effect into consideration.A good agreement between the experimental observations and numerical results is achieved to prove the validity of the modelling method.The tests and simulations show that the impact-induced deformation on the human body is significantly reduced by using STG-modified EVA as the buffering material.The improvement of protective performance is attributed to better dynamic properties and more outstanding energy absorption capability of the composite foam.
文摘A convenient approach is proposed for analyzing the ultimate load carrying capacity of concrete filled steel tubular (CFST) arch bridge with stiffening girders. A fiber model beam element is specially used to simulate the stiffening girder and CFST arch rib. The geometric nonlinearity, material nonlinearity, influence of the construction process and the contribution of prestressing reinforcement are all taken into consideration. The accuracy of this method is validated by comparing its results with experimental results. Finally, the ultimate strength of an abnormal CFST arch bridge with stiffening girders is investigated and the effect of construction method is discussed. It is concluded that the construction process has little effect on the ultimate strength of the bridge.
基金financially supported by the National Science and Technology Major Project(2017-VII-0012-0107)the China Postdoctoral Science Foundation(Nos.2019T120903 and 2018M631151)+5 种基金the Natural Science Foundation of Shaanxi Province(No.2019JQ-165)the Domain Foundation of Equipment Advance Research of 13th Five-year Plan(No.JZX7Y20190262062001)the Postdoctoral Science Foundation of Shaanxi Province(No.2018BSHYDZZ59)the opening foundation from Science and Technology on Plasma Dynamics Laboratory in Air Force Engineering University of China(No.61422020701)the Young Talent fund of University Association for Science and Technology in Shaanxi,China(No.20190403)The financial support from China Scholarship Council(CSC)to be a postdoctoral researcher in Forschungszentrum Jülich would be greatly appreciated by Dr.G.R.Li(No.201806285079)。
文摘Air plasma sprayed thermal barrier coatings(APS-TBCs)saw their wide application in high-temperaturerelated cutting-edge fields.The lamellar structure of APS-TBCs provides a significant advantage on thermal insulation.However,short life span is a major headache for APS-TBCs.This is highly related to the property changes and passive behaviors of the coatings during thermal service.Herein,a finite element model was developed to investigate the dynamic stiffening and substrate constraint on total spallation process.Results show that the stiffening accelerates the crack propagation of APS-TBCs.The driving force for crack propagation,which is characterized by strain energy release rate(SERR),is significantly enlarged.Consequently,the crack starts to propagate when the SERR exceeds the fracture toughness.In addition,the changing trends of SERR and crack propagation features are highly associated with temperatures.A higher temperature corresponds to more significant effect of stiffening on substrate constraint.In brief,temperature-dependent stiffening significantly aggravates the substrate constraint effect on APS-TBCs,which is one of the major causes for the spallation.Given that,lowering stiffening degree is essential to maintain high strain tolerance,and to further extend the life span of APS-TBCs.This understanding contributes to the development of advanced TBCs in future applications.
文摘Electrode stress is one of the main driving forces of electrochemical degradation,which is directly related to battery cycle life,thus attracting great interest.Herein,we propose an in situ method to measure bilayer stresses in film-substrate electrodes during electrochemical processes.This method consists of two parts:stress models featuring Li-dependent material modulus and in situ deformation measurements,through which electrode bilayer stresses evolution accompanied by Li-dependent material modulus can be quantitatively characterized.As application of the method,typical silicon-composite and carbon-composite film-substrate electrodes are selected for in situ mechanical measurements and experimental analysis is performed.Results show that silicon material and carbon material exhibit significant,continuous softening and stiffening,respectively.In two film-substrate electrodes,electrode material films experience compressive stress and current collector substrates undergo a tensile-to-compressive conversion across the thickness.Besides,moduli and stresses in both electrodes vary nonlinearly with capacity,presenting non-overlapping paths between lithiation and delithiation.Based on experimental data,we further demonstrate the key role of Li-dependent modulus on electrode stresses,finding that silicon material softening decreases and carbon material stiffening increases electrode stresses.The deficiencies of current stress measurement method based on Stoney equation and the applicability of our method are discussed.
文摘Stiffening-ribbed-hollow-pipe cast-in place reinforced concrete girderless floor is a new-style hollow girderless floor system. Model experimental researches of simply-supported floor and four-corners bearing floor have been done on this new kind of floor system in this paper. The experiment results show that the floor system has good mechanical property such as high bearing capacity, big rigidity and good tensility. A theoretical method is presented in this paper that the stiffening-ribbed-hollow-pipe girderless floor can be analyzed by being converted equivalently to orthotropic solid slab. It is indicated that the method is correct and reasonable according to the contrast between theoretical calculated results and experimental measured results. The theoretical results coincide with the measured results well.
文摘To solve the problem that the overlapping parts of a retractable pier column are prone to damage,this paper proposed the reinforcing measure of setting a stiffener ring at the bottom of the steel pipe.To study how the stiffener-ring parameters influence the mechanical properties of the pier column.12 scale model specimens(including nine specimens with stiffener-ring widths of 40,50,and 60 mm and three unstiffened comparison specimens)were tested under axial compression.Based on the test results,the specimen load-displacement,load-deflection,and load-strain curves were analyzed,and a finite-element model of a pier column under axial compression was established to determine the optimal stiffener size.The results show that setting a stiffener ring enhances the cooperative working ability between the steel pipe and the internal filling material and restrains the lateral deformation of the pier column,thereby improving the ultimate bearing capacity and overall stability of the pier column.The ultimate bearing capacity of the pier column is related to the width and thickness of the stiffener ring.The optimal size of the stiffener ring of the model pier column is 70 mm in width and 4 mm in thickness.The present research results provide a reference for designing compressible pier columns and column stiffening in mines and have important practical significance.
文摘A rigid flexible coupling physical model which can represent a flexible spacecraft is investigated in this paper. By applying the mechanics theory in a non-inertial coordinate system,the rigid flexible coupling dynamic model with dynamic stiffening is established via the subsystemmodeling framework. It is clearly elucidated for the first time that,dynamic stiffening is produced by the coupling effect of the centrifugal inertial load distributed on the beamand the transverse vibration deformation of the beam. The modeling approach in this paper successfully avoids problems which are caused by other popular modeling methods nowadays： the derivation process is too complex by using only one dynamic principle; a clearly theoretical explanation for dynamic stiffening can＇t be provided. First,the continuous dynamic models of the flexible beamand the central rigid body are established via structural dynamics and angular momentumtheory respectively. Then,based on the conclusions of orthogonalization about the normal constrained modes,the finite dimensional dynamic model suitable for controller design is obtained. The numerical simulation validations showthat： dynamic stiffening is successfully incorporated into the dynamic characteristics of the first-order model established in this paper,which can indicate the dynamic responses of the rigid flexible coupling system with large overall motion accurately,and has a clear modeling mechanism,concise expressions and a good convergence.
基金supported by the National Natural Science Foundations of China (10772085,11272155 and 11132007)333 Project of Jiangsu Province,China(BRA2011172)NUST Research Funding,China(2011YBXM32)
文摘The dynamics for multi-link spatial flexible manipulator arms is investigated. The system considered here is an N-flexible-link manipulator driven by N DC-motors through N revolute flexiblejoints. The flexibility of each flexible joint is modeled as a linearly elastic torsional spring, and the mass of the joint is also considered. For the flexibility of the link, all of the stretching deformation, bending deformation and the torsional deformation are included. The complete governing equations of motion of the system are derived via the Lagrange equations. The nonlinear description of the deformation field of the flexible link is adopted in the dynamic modeling, and thus the dynamic stiffening effects are captured. Based on this model, a general-purpose software package for dynamic simulation of multi-link spatial flexible manipulator arms is developed. Several illustrative examples are given to validate the algorithm presented in this paper and to indicate that not only dynamic stiffening effects but also the flexibility of the structure has significant influence on the dynamic performance of the manipulator.
文摘We experienced a very rare complication of colonoscopy,a migration of stiffening tube into the colorectum. We herein introduce a withdrawing method of migrating stiffening tube incidentally inserted into the colorectum.A 65-year-old Japanese woman underwent colonoscopy because of abdominal discomfort. We used stiffening tube to insert the scope to the proximal colon because of her redundant sigmoid colon. When withdrawing the scope,we realized that the tube was fully inside the colorectum.We could not remove the tube instantly, and it reached the splenic flexure, finally. We reinserted the scope through the migrating tube, straightened the scope, and withdrew it holding a slight angle of the scope over the proximal end of the tube. Then, we could safely remove the tube along with the scope through the anus.
文摘In construction industry, the application of high-performance reinforcement bar is required strongly. Unfortunately, not nearly enough research has been conducted on high-performance steel in comparison with high strength concrete. This paper describes the effect of high-performance steel as reinforcement steel bar on the tension response and cracking behavior of concrete and fiber-reinforced strain-hardening cement-based composite (SHCC) tension members. High-performance steel is characterized by higher strength in comparison to ASTM A615-06 Grade 60 steel. The tension stiffening effect on high-performance reinforcing bars embedded in cement-based composite prism is investigated experimentally. The variables in the study are types of cement-based composite (conventional concrete, synthetic fiber-reinforced cement composite), yielding strength of steel bars (400MPa and 600MPa), and types of loading (monotonic and repeated tension loading).
基金National Key Basic Research and Development Program(973Program),China(No.2002CB412709)
文摘Based on an assumption of parabolic bond stress distribution,a simplified model with quartic polynomial function of the relative slip of steel bar and surrounding concrete for reinforced concrete (RC)tensile member was proposed. The post-cracking behavior as well as tension stiffening effect was considered in the new model. The relative slip of bending member could also be determined through the extension of the new model,which could be applied to obtaining the concentrated rotations at certain sections in order to predict the flexural deformation of RC beam. Several examples of four-point bending RC beams were approached to verify the new model,and the predictions of the flexural deflections of RC beams agreed well with experimental results. The new model can be extended to the application of partially corroded RC beam.
基金National Science and Technology Support Program of China(No.2009BAG15B02)Key Programs for Science and Technology Development of Chinese Transportation Industry(No.2008-353-332-190)
文摘Compared to the conventional two-tower suspension bridge, the three-tower suspension bridge has obviously different characteristics in structural performance because of the extra middle tower and main span. The construction sequence for the stiffening girder is significantly different between the three-tower suspension bridge and the two-tower suspension bridge. The tangential angle of the main cable is one of the controlling factors of the stiffening girder erection stage for a suspension bridge. According to 5 feasible cases for the stiffening girder erection scheme in Taizhou Bridge, the research about the tangential angle in each case mentioned above was made, and some factors that should be taken into account for the erection scheme of stiffening girder were pointed out.
文摘In order to clear constructional design of corner joint, it is necessary to further investi-gate mechanical property of corner joint in gabled frames. Through static test and finite element software analysis of comparing the panel zone with and without inclined stiffener. Some conclusions are given in the article. The load displacement curves show that the capacity of oblique nodes installed within stiffening rib components is enhanced i.e. 40% more than those without stiffening rib nodes. The results reveal that in the gabled frames, the corner node with the inclined stiffening rib can improve the bearing capacity of the specimens. When the extraterritorial flange is tension, the erection of the inclined stiffening rib can prevent structural failure and improve effectually the ductility of the structure.
基金supported by the National Natural Science Foundation of China(52203064 and 52373061)the China Postdoctoral Science Foundation(2023M732415)+1 种基金the Fundamental Research Funds for the Central Universities(2022SCU12011)the State Key Laboratory of Polymer Materials Engineering,Sichuan University。
文摘Thermal softening is an inevitable process in the physical network.Polyurethane(PU),a typical commercial material,is constructed by physical networks,which undergoes the serious thermal decay on mechanical properties at high temperature.Herein,a physically cross-linked PU with a unique thermal stiffening behavior has been developed by incorporating B–N coordination with reversible B–O bonds.The B–N coordination can significantly improve the mechanical properties of the PU.The reversible B–O bonds(temperature dependent reversible transformation between B–OH and B–O–B)are conducive to constructing more multicoordination macromolecular crosslinking points and more stable B–N coordination bonds at high temperature,endowing the PU with the special thermal stiffening behavior for the first time.Such thermal stiffening behavior compensates for the bond breakage and the network destruction caused by heat,significantly expands the rubbery plateau and delays the entire chain motion of the thermoplastic PU.As a result,the terminal flow occurs at a higher temperature up to 200°C.The modulus retention ratio of the materials is up to 87%even at 145oC,which is much higher than that of the existing PU elastomer with the physical network and even some covalent cross-link PU.Simultaneously,the physical network ensures the recyclability of the PU,and the thermal stiffening behavior is still obtained in recycled PU.This work provides a simple strategy to impart thermal stiffening behavior to the physically crosslinked PU,thereby significantly extending the operating temperature range of thermoplastic PU,which can potentially expand the scopes of PU in applications under harsh conditions.
基金supported by Twelfth"Five-Year"Plan Major Projects supported by the National Science and Technology Pillar Program of China(Grant No.2011BAJ09B01)Tsinghua University Initiative Scientific Research Program(Grant No.2010Z03078)
文摘In practical design,the joints with outer stiffening ring were used to connect concrete beams and laminated steel tube columns.The seismic behavior of joints with outer stiffening ring with various types was studied based on experiments.The bearing capacity,rigidity,ductility,energy dissipation capacity,deformation property and strain distribution of the joints with outer stiffening ring with various types were comprehensively evaluated based on the test results of three specimens under quasistatic cyclic loading and finite element analysis.The test results showed that the failure mode,hysteretic behavior,bearing capacity and rigidity degradation of the joints with outer stiffening ring with various types were nearly identical.Furthermore,the strain distribution of the outer stiffening ring of the three joints was nearly the same.The detailing recommendation for the outer strengthening rings was proposed for the concrete beam-laminated steel tube column joints with outer stiffening ring,in order to ensure the good seismic capacity of the joints.
基金Financial support from the Natural Sciences and Engineering Research Council of Canada(NSERC)through a Steacie Fellowship,from Grand Challenges of Canada,and from the Canada Research Chairs Program is acknowledged.
文摘The higher risk of vaso-occlusion events and sudden death for sickle-cell trait(SCT)athletes has been speculatively ascribed to SCT red blood cell(RBC)stiffening during strenuous exercise.However,the microenvironmental changes that could induce the stiffening of SCT RBCs are unknown.To address this question,we measured the mechanical properties of and changes in SCT RBCs under deoxygenated and acidic environments,which are two typical conditions present in the circulation of athletes undertaking strenuous exercise.The results reveal that SCT RBCs are inherently stiffer than RBCs from non-SCT healthy subjects,and a lower pH further stiffens the SCT cells.Furthermore,at both normal and low pH levels,deoxygenation was found to not be the cause of the stiffness of SCT RBCs.This study confirms that the stiffening of SCT RBCs occurs at a low pH and implies that SCT RBC stiffening could be responsible for vaso-occlusion in SCT athletes during strenuous exercise.
基金supported by Natural Science Foundation of Fujian Province(2022I0019)Scientific Research Foundation for Jimei University(ZQ2024041,ZQ2024042).
文摘The penetration of ogival-nosed projectiles into ship plates represents a complex impact dynamics issue essential for analyzing structural failuremechanisms.Although stiffenedplates are vital in ship construction,fewstudies have addressed the issue of model equivalence under penetration loading.This study employs numerical simulation to validate an experiment with an ogival-nosed projectile penetrating a Q345 steel plate.Four equivalent stiffened plate methods are proposed based on the area,flexural modulus,moment of inertia,and thickness.The results indicate that thickness equivalence(DM4)is unsuitable for penetration-loaded stiffened plates,except under low-speed,nonpenetrating through impacts,and yields less accuracy than DM1/DM3.DM1,DM2,and DM3 each perform optimally with specific velocity ranges:DM1 at very low(critical)and high velocities,DM3 at low velocities,and DM2 at high speeds.Furthermore,in penetration scenarios,T-shaped stiffeners can be replacedwith rectangular ones,as both exhibit similar failure behaviors and deflection trends,simplifying the design while preserving key structural characteristics.These findings provide valuable insights into the design of protective ship structures.
基金The authors express their gratitude to Universiti Pura Malaysia(UPM),Malaysia for granting Putra IPS vote number 9742900.
文摘The increasing demand to decrease manufacturing costs and weight reduction is driving the aircraft industry to change the use of conventional riveted stiffened panels to integral stiffened panels(ISP)for aircraft fuselage structures.ISP is a relatively new structure in aircraft industries and is considered the most significant development in a decade.These structures have the potential to replace the conventional stiffened panel due to the emergence of manufacturing technology,including welding,high-speed machining(HSM),extruding,and bonding.Although laser beam welding(LBW)and friction stir welding(FSW)have been applied in aircraft companies,many investigations into ISP continue to be conducted.In this review article,the current state of understanding and advancement of ISP structure is addressed.A particular explanation has been given to(a)buckling performance,(b)fatigue performance of the ISP,(c)modeling and simulation aspects,and(d)the impact of manufacturing decisions in welding processes on the final structural behavior of the ISP during service.Compared to riveted panels,machined ISP had a better compressive buckling load,and FSW integral panels had a lower buckling load than riveted panels.Compressive residual stress decreased the stress intensity factor(SIF)rates,slowing down the growth of fatigue cracks as occurred in FSW and LBW ISP.
基金financially supported by the National Natural Science Foundation of China(Grant No.52001040),the Natural Science Foundation Project of Chongqing,Chongqing Science and Technology Commission(Grant No.cstc2021jcyj-msxmX0944)the Science and Technology Research Program of Chongqing Municipal Education Commission(Grant No.KJZD-K202300710).
文摘The influences of different factors,including whether the transverse frames are actually built,longitudinal and transverse welding residual stresses,and unloaded edge boundaries,on the ultimate strength and failure mode of a real hull bottom full-scale stiffened plate under axial compression and lateral pressure are investigated via numerical analysis.Result shows that the failure mode of the stiffened plate under axial compression is the tripping of the stiffeners.Whether transverse frames are built has little effect on the ultimate strength of the stiffened plate under axial compression,which can be replaced by the degree of freedom constraint.However,when lateral pressure is present,the transverse frame cannot be simply replaced by a free-degree constraint.The longitudinal residual stress has a greater effect on the ultimate strength,whereas the effect of the transverse residual stress is smaller.Stronger unloaded edge boundary conditions can slightly enhance the stiffness and ultimate strength of the stiffened plate.Under combined axial compression and lateral pressure,the failure mode of stiffened plates changes from the tripping of stiffeners to beam-column failure,as the lateral pressure increases.The ability of stiffened plates in which transverse frames are actually built out to resist beam-column shape deformation becomes weaker with lower ultimate strength.Stronger unloaded edge boundary conditions can improve the ability of stiffened plates to resist beam-column deformation and increase the ultimate strength.
文摘The buckling behavior of stiffened panels is significantly influenced by material and geometric defects,making it a critical factor in ensuring structural integrity and safety.These panels are widely used in mechanical,aerospace,marine,and civil engineering applications due to their ability to enhance bending stiffness with minimal additional weight.Under high loads or stress concentrations,localized structural failures can initiate global buckling in stiffened panels.This study investigates how such defects affect the critical buckling load,stiffness,and thickness of stiffened panels.Two finite element analyses were conducted:a linear analysis to identify the initial buckling mode and a nonlinear analysis using the Riks algorithm in Abaqus CAE,incorporating localized imperfections.The simulations show that material and geometric defects can reduce buckling resistance depending on their severity.
