Dambreak-induced bed scouring may undermine the foundation of bridge piers and other structures,and that destruction can pose a serious threat.Consequently,this paper aims at exploring the mechanisms of scouring and a...Dambreak-induced bed scouring may undermine the foundation of bridge piers and other structures,and that destruction can pose a serious threat.Consequently,this paper aims at exploring the mechanisms of scouring and armoring.Firstly,the incipient velocity for nonuniform sediment particles was studied,and a formula was derived based on the angle of repose of nonuniform sediment.The results showed that the mechanism of incipient motion for sand and fine gravel differed from that for coarse gravel and cobbles.Also,comparison between experimental and field data shows that the results from the proposed formula agree well with those observed for all conditions.Secondly,a birth-death,immigration-emigration Markov process was developed to describe the bed load transport rate associated with scouring and armoring.The comparison between experimental data and computed results shows that our model can predict the bed load transport rate,although there may be some limitations,the chief of which is that there are many variables in the model to be determined through experiment.This makes its application in river engineering inconvenient.展开更多
Flume experiments were carried out to study bed load transport rate during rive bed scouring and ar- moring.A theoretical differential equation linking the transport rate to the probability of incipient motion of non-...Flume experiments were carried out to study bed load transport rate during rive bed scouring and ar- moring.A theoretical differential equation linking the transport rate to the probability of incipient motion of non-uniform sediment is solved.The transport rate is shown to decrease exponentially with time,according to the theory,which is in good agreement with the experiment data.展开更多
Hard scales in scaly fish species ensure the structural and functional integrity of the inner skin and body,even when subjected to various types of external forces.Mucus and oil secreted from the inner layer of the fi...Hard scales in scaly fish species ensure the structural and functional integrity of the inner skin and body,even when subjected to various types of external forces.Mucus and oil secreted from the inner layer of the fish skin to the surface exhibit resistance to a wide range of liquids,maintaining the antifouling properties of the fish skin surface.Inspired by these biological structures,ultra-sturdy and durable scale-armored-sliding surfaces(SASSs)were fabricated in this study using femtosecond laser electrodeposition(FED).In the FED method,a scaly structure is grown from the substrate across a sliding layer to form an SASS.The unique scale-armored structure offers protection against impact and abrasion while maintaining the performance and integrity of the structure.The mechanical sturdiness of the SASS improved by four orders of magnitude compared to that of the conventional antifouling surface.In addition,the SASS exhibited remarkable chemical durability,excellent hydraulic pressure resistance,liquid repellency,and good corrosion resistance based on characterization using various methods.FED enables the preparation of SASS on several materials,including Cu and Al and more.SASS fabricated using FED has great potential for the application of antifouling surfaces in extremely harsh environments.展开更多
The high cost and low efficiency of full-scale vehicle experiments and numerical simulations limit the efficient development of armored vehicle occupant protection systems.The floor-occupant-seat local simulation mode...The high cost and low efficiency of full-scale vehicle experiments and numerical simulations limit the efficient development of armored vehicle occupant protection systems.The floor-occupant-seat local simulation model provides an alternative solution for quickly evaluating the performance of occupant protection systems.However,the error and rationality of the loading of the thin-walled floor in the local model cannot be ignored.This study proposed an equivalent loading method for the local model,which includes two parts:the dimensionality reduction method for acceleration matrix and the joint optimization framework for equivalent node coordinates.In the dimensionality reduction method,the dimension of the acceleration matrix was reduced based on the improved kernel principal component analysis(KPCA),and a dynamic variable bandwidth was introduced to address the limitation of failing to effectively measure the similarity between acceleration data in conventional KPCA.In addition,a least squares problem with forced displacement constraints was constructed to solve the correction matrix,thereby achieving the scale restoration process of the principal component acceleration matrix.The joint optimization framework for coordinates consists of the error assessment of response time histories(EARTH)and Bayesian optimization.In this framework,the local loading error of the equivalent acceleration matrix is taken as the Bayesian optimization objective,which is quantified and scored by EARTH.The expected improvement acquisition function was used to select the new set of the equivalent acceleration node coordinates for the self-updating optimization of the observation dataset and Gaussian process surrogate model.We reduced the dimension of the acceleration matrix from 2256 to 7,while retaining 91%of the information features.The comprehensive error score of occupant's lower limb response in the local model increased from 58.5%to 80.4%.The proposed equivalent loading method provides a solution for the rapid and reliable development of occupant protection systems.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
This paper proposes a modification of the Forrestal-Warren perforation model aimed at extending its applicability range to intermediately-thick high-hardness armor steel plates.When impacted by armorpiercing projectil...This paper proposes a modification of the Forrestal-Warren perforation model aimed at extending its applicability range to intermediately-thick high-hardness armor steel plates.When impacted by armorpiercing projectiles,these plates tend to fail through adiabatic shear plugging which significantly reduces their ballistic resistance.To address this effect,an approach for determining effective thickness was defined and incorporated into the predictive model.Ballistic impact tests were performed to assess the modification's validity,in which ARMOX 500T steel plates were subjected to perpendicular impacts from 7.62×39 mm steel-cored rounds under various velocities.Frequent target failure by soft plugging was observed,as well as the brittle shatter of the hard steel core.Key properties of the recovered plugs including their mass,length and diameter were measured and reported along with the projectiles'residual velocities.Additionally,independent data from the open literature were included in the analysis for further validation.The original Forrestal-Warren model and the novel effective thickness modification were then used to establish the relationship between impact and residual velocities,as well as to determine the ballistic limit velocity.The comparison revealed that the proposed approach significantly improves the model's accuracy,showing a strong correlation with experimental data and reducing deviations to within a few percent.This enhancement highlights the potential of the effective thickness term,which could also be applied to other predictive models to extend their applicability range.Further exploration into other armor steels and impact conditions is recommended to assess the method's versatility.展开更多
The editor regrets that they inadvertently pasted the wrong figure during the production stage.The correct Fig.7 should be as below:The editor would like to apologise for any inconvenience caused.
Lithium-rich manganese-based oxides(LRMOs;xLi_(2)MnO_(3)(1−x)LiMO_(2);M=transition metal,0<x<1)with excellent specific capacity(>300 mAh/g)and high operating voltage(≥4.8V)are the preferred cathode materials...Lithium-rich manganese-based oxides(LRMOs;xLi_(2)MnO_(3)(1−x)LiMO_(2);M=transition metal,0<x<1)with excellent specific capacity(>300 mAh/g)and high operating voltage(≥4.8V)are the preferred cathode materials for high-specific-energy lithium metal batteries(LMBs)[1].However,LRMOs face a series of serious problems such as irreversible lattice oxygen loss,transition metal(TM)migration,phase transfer,and interfacial side reactions at high voltages,resulting in rapid decay of capacity and voltage[2,3].In situ generating well-functional CEI through electrolyte engineering can effectively address these challenges[4].展开更多
Despite numerous research investigations to understand the influences of various structural parameters,to the authors'knowledge,no research has been the effect of different angles of incidence on stab response and...Despite numerous research investigations to understand the influences of various structural parameters,to the authors'knowledge,no research has been the effect of different angles of incidence on stab response and performance of different types of protective textiles.Three distinct structures of 3D woven textiles and 2D plain weave fabric made with similar high-performance fiber and areal density were designed and manufactured to be tested.Two samples,one composed of a single and the other of 4-panel layers,from each fabric type structure,were prepared,and tested against stabbing at[0○],[22.5○],and[45○]angle of incidence.A new stabbing experimental setup that entertained testing of the specimens at various angles of incidence was engineered and utilized.The stabbing bench is also equipped with magnetic sensors and a UK Home Office Scientific Development Branch(HOSDB)/P1/B sharpness engineered knives to measure the impact velocity and exerted impact energy respectively.A silicon compound was utilized to imprint the Back Face Signature(BFS)on the backing material after every specimen test.Each silicon print was then scanned,digitized,and precisely measured to evaluate the stab response and performance of the specimen based on different performance variables,including Depth of Trauma(DOT),Depth of Penetration(DOP),and Length of Penetration(LOP).Besides,the post-impact surface failure modes of the fabrics were also measured using Image software and analyzed at the microscale level.The results show stab angle of incidence greatly influences the stab response and performance of protective textiles.The outcome of the study could provide not only valuable insights into understanding the stab response and capabilities of protective textiles under different angle of incidence,but also provide valuable information for protective textile manufacturer,armor developer and stab testing and standardizing organizations to consider the angle of incidence while developing,testing,optimizing,and using protective textiles in various applications.展开更多
Passive daytime radiative cooling(PDRC)technology is emerging as one of the most promising solutions to the global problem of spacing cooling,but its practical application is limited due to reduced cooling effectivene...Passive daytime radiative cooling(PDRC)technology is emerging as one of the most promising solutions to the global problem of spacing cooling,but its practical application is limited due to reduced cooling effectiveness caused by daily wear and tear,as well as dirt contamination.To tackle this problem,we report a novel strategy by introducing a renewable armor structure for prolonging the anti-fouling and cooling effectiveness properties of the PDRC coatings.The armor structure is designed by decorating fluorinated hollow glass microspheres(HGM)inside rigid resin composite matrices.The HGM serve triple purposes,including providing isolated cavities for enhanced solar reflectance,reinforcing the matrices to form robust armored structures,and increasing thermal emittance.When the coatings are worn,the HGM on the surface expose their concave cavities with numerous hydrophobic fragments,generating a highly rough surface that guarantee the superhydrophobic function.The coatings show a high sunlight reflectance(0.93)and thermal emittance(0.94)in the long-wave infrared window,leading to a cooling of 5℃ below ambient temperature under high solar flux(∼900 W/m^(2)).When anti-fouling functions are reduced,they can be regenerated more than 100 cycles without compromising the PDRC function by simple wearing treatment.Furthermore,these coatings can be easily prepared using a one-pot spray method with low-cost materials,exhibit strong adhesion to a variety of substrates,and demonstrate exceptional environmental stability.Therefore,we anticipate their immediate application opportunities for spacing cooling.展开更多
This study examines the penetration of 12.7 mm armor piercing incendiary projectiles into SiC ceramic-fiber composite target plates.By observing the recovered projectile and the overall damage morphology of the cerami...This study examines the penetration of 12.7 mm armor piercing incendiary projectiles into SiC ceramic-fiber composite target plates.By observing the recovered projectile and the overall damage morphology of the ceramic-fiber composite target plates.Additionally,multi-level screening and weighing of the recovered projectile and ceramic fragments revealed that the mass distribution of the projectile and ceramic fragments under different backing structures conforms to a powerlaw distribution.Experimental results indicate that for single laminate as the backing,the fragmentation of the projectile and ceramics is highest when T300 is the material.Incorporating a T300 transition layer between the SiC ceramic and aramid fibers(Kevlar)or ultra-high molecular weight polyethylene(UHMWPE)increases the fragmentation of the projectile and ceramics,leading to increased energy absorption.The projectile’s head mainly exhibits pulverized abrasive fragmentation,while larger projectile fragments primarily result from shear and tensile stress-induced shear-tensile failure fractures.The primary damage mode of ceramics under high-speed impact is the expansion of ceramic cones and radial cracks.The main form of damage in UHMWPE laminate is interlayer separation caused by tensile waves,permanent plastic deformation at the back protrusion,and perforation failure primarily due to shear waves.The damage mode of Kevlar laminate is similar to that of UHMWPE,with the distinction being that Kevlar laminate primarily exhibits perforation failure caused by tensile waves.Carbon fiber T300 laminate damage mainly consists of cross-shaped brittle fractures caused by shear waves.展开更多
A philosophy for the design of novel,lightweight,multi-layered armor,referred to as Composite Armor Philosophy(CAP),which can adapt to the passive protection of light-,medium-,and heavy-armored vehicles,is presented i...A philosophy for the design of novel,lightweight,multi-layered armor,referred to as Composite Armor Philosophy(CAP),which can adapt to the passive protection of light-,medium-,and heavy-armored vehicles,is presented in this study.CAP can serve as a guiding principle to assist designers in comprehending the distinct roles fulfilled by each component.The CAP proposal comprises four functional layers,organized in a suggested hierarchy of materials.Particularly notable is the inclusion of a ceramic-composite principle,representing an advanced and innovative solution in the field of armor design.This paper showcases real-world defense industry applications,offering case studies that demonstrate the effectiveness of this advanced approach.CAP represents a significant milestone in the history of passive protection,marking an evolutionary leap in the field.This philosophical approach provides designers with a powerful toolset with which to enhance the protection capabilities of military vehicles,making them more resilient and better equipped to meet the challenges of modern warfare.展开更多
The abalone shell,a composite material whose cross-section is composed of inorganic and organic layers,has high strength and toughness.Inspired by the abalone shell,several multi-layer composite plates with different ...The abalone shell,a composite material whose cross-section is composed of inorganic and organic layers,has high strength and toughness.Inspired by the abalone shell,several multi-layer composite plates with different layer sequences and thicknesses are studied as bullet-proof material in this paper.To investigate the ballistic performance of this multi-layer structure,the complete characterization model and related material parameters of large deformation,failure and fracture ofAl_(2)O_(3)ceramics andCarbon Fiber Reinforced Polymer(CFRP)are studied.Then,3D finite element models of the proposed composite plates with different layer sequences and thicknesses impacted by a 12.7 mm armor-piercing incendiary(API)are built using Abaqus to predict failure.The simulation results show that the CFRP/Al2O3 ceramic/Ultrahigh Molecular Weight Polyethylene(UHMWPE)/CFRP(1 mm/4 mm/4 mm/1 mm)composite is the optimized stack of layers.The simulation results under specified layer sequence and thickness have a reasonable correlation with the experimental results and reflect the failure and fracture of the multi-layer composite protective armor.展开更多
To enhance the protective performance of ceramic composite armor,ballistic penetration experiments were conducted on Al_(2)O_(3) ceramic-ultra-high molecular weight polyethylene(UHMWPE)composite armor with different t...To enhance the protective performance of ceramic composite armor,ballistic penetration experiments were conducted on Al_(2)O_(3) ceramic-ultra-high molecular weight polyethylene(UHMWPE)composite armor with different thickness configurations.The damage and failure modes of hard projectiles and ceramic-fiber composite targets were analyzed.The recovered projectiles and ceramic fragments were sieved and weighed at multiple stages,revealing a positive correlation between the degree of fragmentation of the projectiles and ceramics and the overall ballistic resistance of the composite targets.Numerical simulations were performed using the LS-DYNA finite element software,and the simulation results showed high consistency with the experimental results,confirming the validity of the material parameters.The results indicate that the projectile heads primarily exhibited crushing and abrasive fragmentation.Larger projectile fragments mainly resulted from tensile and shear stress-induced failure.The failure modes of the composite targets included the formation of ceramic cones and radial cracks under high-velocity impacts.The UHMWPE laminated plates exhibited interlayer separation caused by tensile waves,permanent plastic deformation of the rear surface bulging,and perforation failure primarily due to shear forces.Through extended numerical simulations,while maintaining the same areal density and configuration of9 mm Al_(2)O_(3) ceramic+12 mm UHMWPE laminated composite armor,the thickness configurations of the Al_(2)O_(3) ceramic and UHMWPE laminated backplates were varied,and various thicknesses of UHMWPE laminates were simulated as the cover layer for the ceramic panels.The simulation results indicated that the composite armor configuration of 10 mm Al_(2)O_(3) ceramic+8 mm UHMWPE composite armor increased energy absorption by13.48%.When altering the cover layer thickness,a 4 mm UHMWPE+9 mm Al_(2)O_(3)+8 mm UHMWPE composite armor demonstrated a 27.11%improvement in energy absorption,showing a relatively significant enhancement.展开更多
The Altomani&Sons Collection owns a remarkable newly discovered portrait of Guidobaldo II della Rovere,Duke of Urbino(1514-1574),a historical military figure who was a condottiere,ruler of Urbino,Commander-in-chie...The Altomani&Sons Collection owns a remarkable newly discovered portrait of Guidobaldo II della Rovere,Duke of Urbino(1514-1574),a historical military figure who was a condottiere,ruler of Urbino,Commander-in-chief of the Papal Estate,and Perfect of Rome,as well as a collector and patron of the Fine Arts.Camilla Guerrieri Nati(1628-1694),a seventeenth-century Italian painter from Fossombrone(in the province of Pesaro and Urbino),portrayed this heroic personage surrounded by emblems associated with his military courage and leadership,including his plumed burgonet helmet,metal gilded armor,a necklace with the golden fleece,and batons of secular and religious dominions.This oil painting on copper-considered a precious metal at the time-emphasizes the importance of the commission.The material and technique also reveals a unique artistic achievement in that it provides the painting with a smooth,reflective surface and vibrant coloration,symbolizing precious imagery.展开更多
In order to restrain the high pumping voltage of braking procedure which is harmful to the system of electric armored vehicle. Based on the analysis of pumping voltage of the braking procedure, the relation between pu...In order to restrain the high pumping voltage of braking procedure which is harmful to the system of electric armored vehicle. Based on the analysis of pumping voltage of the braking procedure, the relation between pumping voltage and PWM ratio is derived and a new digital control method to restrain the pumping voltage by changing PWM ratio is put forward. Because the capacitance is decreased effectively, the volume of controller is reduced and the performance to price ratio is improved. The results of computer simulation and experiment proved that this method is feasible and valid.展开更多
A numerical model to simulate the bed degradation process in a straight alluvial channel with respect to time and distance is introduced. The simulation takes into account the effect of non uniformity of the bed ma...A numerical model to simulate the bed degradation process in a straight alluvial channel with respect to time and distance is introduced. The simulation takes into account the effect of non uniformity of the bed material, and variations in the dimension of bed forms. The model predicts the changes in the grain size distribution with the time and space during degradation process. The numerical model proposes that the armoring process in degrading channels does not depend only on hydraulic characteristics of the flow but also on variation in the grain size distribution of sediments on the bed. The model was applied and compared with the results obtained from experiments conducted in 24 m recirculating flume for two sizes of sand; a good agreement was found between observed and calculated values.展开更多
Sandy inlets are in a dynamic equilibrium between wave-driven littoral drift acting to close them,and tidal flows keeping them open.Their beds are in a continual state of suspension and deposition,so their bathymetry ...Sandy inlets are in a dynamic equilibrium between wave-driven littoral drift acting to close them,and tidal flows keeping them open.Their beds are in a continual state of suspension and deposition,so their bathymetry and even location are always in flux.Even so,a nearly linear relationship between an inlet’s cross-sectional flow area and the inshore tidal prism is maintained-except when major wind and/or runoff events act to close or widen an inlet.Inlet location can be stabilized by jetties,but dredging may still be necessary to maintain a navigable channel.Armoring with rock large enough to resist erosion can protect an inlet bed or river mouth from excessive storm flow erosion.Armoring can also be used as a stratagem to close inlets.展开更多
基金supported by 973 Program (2008CB425803)the National Natural Science Foundation of China (Grant No. 50979064)
文摘Dambreak-induced bed scouring may undermine the foundation of bridge piers and other structures,and that destruction can pose a serious threat.Consequently,this paper aims at exploring the mechanisms of scouring and armoring.Firstly,the incipient velocity for nonuniform sediment particles was studied,and a formula was derived based on the angle of repose of nonuniform sediment.The results showed that the mechanism of incipient motion for sand and fine gravel differed from that for coarse gravel and cobbles.Also,comparison between experimental and field data shows that the results from the proposed formula agree well with those observed for all conditions.Secondly,a birth-death,immigration-emigration Markov process was developed to describe the bed load transport rate associated with scouring and armoring.The comparison between experimental data and computed results shows that our model can predict the bed load transport rate,although there may be some limitations,the chief of which is that there are many variables in the model to be determined through experiment.This makes its application in river engineering inconvenient.
文摘Flume experiments were carried out to study bed load transport rate during rive bed scouring and ar- moring.A theoretical differential equation linking the transport rate to the probability of incipient motion of non-uniform sediment is solved.The transport rate is shown to decrease exponentially with time,according to the theory,which is in good agreement with the experiment data.
基金supported by the National Science Foundation of China(12127806 and 62175195)the International Joint Research Laboratory for Micro/Nano Manufacturing and Measurement Technologies.
文摘Hard scales in scaly fish species ensure the structural and functional integrity of the inner skin and body,even when subjected to various types of external forces.Mucus and oil secreted from the inner layer of the fish skin to the surface exhibit resistance to a wide range of liquids,maintaining the antifouling properties of the fish skin surface.Inspired by these biological structures,ultra-sturdy and durable scale-armored-sliding surfaces(SASSs)were fabricated in this study using femtosecond laser electrodeposition(FED).In the FED method,a scaly structure is grown from the substrate across a sliding layer to form an SASS.The unique scale-armored structure offers protection against impact and abrasion while maintaining the performance and integrity of the structure.The mechanical sturdiness of the SASS improved by four orders of magnitude compared to that of the conventional antifouling surface.In addition,the SASS exhibited remarkable chemical durability,excellent hydraulic pressure resistance,liquid repellency,and good corrosion resistance based on characterization using various methods.FED enables the preparation of SASS on several materials,including Cu and Al and more.SASS fabricated using FED has great potential for the application of antifouling surfaces in extremely harsh environments.
基金supported by the National Natural Science Foundation of China(Grant Nos.52272437 and 52272370)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX24_0635)。
文摘The high cost and low efficiency of full-scale vehicle experiments and numerical simulations limit the efficient development of armored vehicle occupant protection systems.The floor-occupant-seat local simulation model provides an alternative solution for quickly evaluating the performance of occupant protection systems.However,the error and rationality of the loading of the thin-walled floor in the local model cannot be ignored.This study proposed an equivalent loading method for the local model,which includes two parts:the dimensionality reduction method for acceleration matrix and the joint optimization framework for equivalent node coordinates.In the dimensionality reduction method,the dimension of the acceleration matrix was reduced based on the improved kernel principal component analysis(KPCA),and a dynamic variable bandwidth was introduced to address the limitation of failing to effectively measure the similarity between acceleration data in conventional KPCA.In addition,a least squares problem with forced displacement constraints was constructed to solve the correction matrix,thereby achieving the scale restoration process of the principal component acceleration matrix.The joint optimization framework for coordinates consists of the error assessment of response time histories(EARTH)and Bayesian optimization.In this framework,the local loading error of the equivalent acceleration matrix is taken as the Bayesian optimization objective,which is quantified and scored by EARTH.The expected improvement acquisition function was used to select the new set of the equivalent acceleration node coordinates for the self-updating optimization of the observation dataset and Gaussian process surrogate model.We reduced the dimension of the acceleration matrix from 2256 to 7,while retaining 91%of the information features.The comprehensive error score of occupant's lower limb response in the local model increased from 58.5%to 80.4%.The proposed equivalent loading method provides a solution for the rapid and reliable development of occupant protection systems.
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 Ministry of Science,Technological Development and Innovation of the Republic of Serbia,through the Contract no.451-03-65/2024-03/200105
文摘This paper proposes a modification of the Forrestal-Warren perforation model aimed at extending its applicability range to intermediately-thick high-hardness armor steel plates.When impacted by armorpiercing projectiles,these plates tend to fail through adiabatic shear plugging which significantly reduces their ballistic resistance.To address this effect,an approach for determining effective thickness was defined and incorporated into the predictive model.Ballistic impact tests were performed to assess the modification's validity,in which ARMOX 500T steel plates were subjected to perpendicular impacts from 7.62×39 mm steel-cored rounds under various velocities.Frequent target failure by soft plugging was observed,as well as the brittle shatter of the hard steel core.Key properties of the recovered plugs including their mass,length and diameter were measured and reported along with the projectiles'residual velocities.Additionally,independent data from the open literature were included in the analysis for further validation.The original Forrestal-Warren model and the novel effective thickness modification were then used to establish the relationship between impact and residual velocities,as well as to determine the ballistic limit velocity.The comparison revealed that the proposed approach significantly improves the model's accuracy,showing a strong correlation with experimental data and reducing deviations to within a few percent.This enhancement highlights the potential of the effective thickness term,which could also be applied to other predictive models to extend their applicability range.Further exploration into other armor steels and impact conditions is recommended to assess the method's versatility.
文摘The editor regrets that they inadvertently pasted the wrong figure during the production stage.The correct Fig.7 should be as below:The editor would like to apologise for any inconvenience caused.
文摘Lithium-rich manganese-based oxides(LRMOs;xLi_(2)MnO_(3)(1−x)LiMO_(2);M=transition metal,0<x<1)with excellent specific capacity(>300 mAh/g)and high operating voltage(≥4.8V)are the preferred cathode materials for high-specific-energy lithium metal batteries(LMBs)[1].However,LRMOs face a series of serious problems such as irreversible lattice oxygen loss,transition metal(TM)migration,phase transfer,and interfacial side reactions at high voltages,resulting in rapid decay of capacity and voltage[2,3].In situ generating well-functional CEI through electrolyte engineering can effectively address these challenges[4].
文摘Despite numerous research investigations to understand the influences of various structural parameters,to the authors'knowledge,no research has been the effect of different angles of incidence on stab response and performance of different types of protective textiles.Three distinct structures of 3D woven textiles and 2D plain weave fabric made with similar high-performance fiber and areal density were designed and manufactured to be tested.Two samples,one composed of a single and the other of 4-panel layers,from each fabric type structure,were prepared,and tested against stabbing at[0○],[22.5○],and[45○]angle of incidence.A new stabbing experimental setup that entertained testing of the specimens at various angles of incidence was engineered and utilized.The stabbing bench is also equipped with magnetic sensors and a UK Home Office Scientific Development Branch(HOSDB)/P1/B sharpness engineered knives to measure the impact velocity and exerted impact energy respectively.A silicon compound was utilized to imprint the Back Face Signature(BFS)on the backing material after every specimen test.Each silicon print was then scanned,digitized,and precisely measured to evaluate the stab response and performance of the specimen based on different performance variables,including Depth of Trauma(DOT),Depth of Penetration(DOP),and Length of Penetration(LOP).Besides,the post-impact surface failure modes of the fabrics were also measured using Image software and analyzed at the microscale level.The results show stab angle of incidence greatly influences the stab response and performance of protective textiles.The outcome of the study could provide not only valuable insights into understanding the stab response and capabilities of protective textiles under different angle of incidence,but also provide valuable information for protective textile manufacturer,armor developer and stab testing and standardizing organizations to consider the angle of incidence while developing,testing,optimizing,and using protective textiles in various applications.
基金supported by the National Natural Science Foundation of China(Nos.52003035,52203135 and 51973023)the CHN Energy Group Project(No.GJNY-21-183).
文摘Passive daytime radiative cooling(PDRC)technology is emerging as one of the most promising solutions to the global problem of spacing cooling,but its practical application is limited due to reduced cooling effectiveness caused by daily wear and tear,as well as dirt contamination.To tackle this problem,we report a novel strategy by introducing a renewable armor structure for prolonging the anti-fouling and cooling effectiveness properties of the PDRC coatings.The armor structure is designed by decorating fluorinated hollow glass microspheres(HGM)inside rigid resin composite matrices.The HGM serve triple purposes,including providing isolated cavities for enhanced solar reflectance,reinforcing the matrices to form robust armored structures,and increasing thermal emittance.When the coatings are worn,the HGM on the surface expose their concave cavities with numerous hydrophobic fragments,generating a highly rough surface that guarantee the superhydrophobic function.The coatings show a high sunlight reflectance(0.93)and thermal emittance(0.94)in the long-wave infrared window,leading to a cooling of 5℃ below ambient temperature under high solar flux(∼900 W/m^(2)).When anti-fouling functions are reduced,they can be regenerated more than 100 cycles without compromising the PDRC function by simple wearing treatment.Furthermore,these coatings can be easily prepared using a one-pot spray method with low-cost materials,exhibit strong adhesion to a variety of substrates,and demonstrate exceptional environmental stability.Therefore,we anticipate their immediate application opportunities for spacing cooling.
文摘This study examines the penetration of 12.7 mm armor piercing incendiary projectiles into SiC ceramic-fiber composite target plates.By observing the recovered projectile and the overall damage morphology of the ceramic-fiber composite target plates.Additionally,multi-level screening and weighing of the recovered projectile and ceramic fragments revealed that the mass distribution of the projectile and ceramic fragments under different backing structures conforms to a powerlaw distribution.Experimental results indicate that for single laminate as the backing,the fragmentation of the projectile and ceramics is highest when T300 is the material.Incorporating a T300 transition layer between the SiC ceramic and aramid fibers(Kevlar)or ultra-high molecular weight polyethylene(UHMWPE)increases the fragmentation of the projectile and ceramics,leading to increased energy absorption.The projectile’s head mainly exhibits pulverized abrasive fragmentation,while larger projectile fragments primarily result from shear and tensile stress-induced shear-tensile failure fractures.The primary damage mode of ceramics under high-speed impact is the expansion of ceramic cones and radial cracks.The main form of damage in UHMWPE laminate is interlayer separation caused by tensile waves,permanent plastic deformation at the back protrusion,and perforation failure primarily due to shear waves.The damage mode of Kevlar laminate is similar to that of UHMWPE,with the distinction being that Kevlar laminate primarily exhibits perforation failure caused by tensile waves.Carbon fiber T300 laminate damage mainly consists of cross-shaped brittle fractures caused by shear waves.
基金co-financed by the European Regional Development Fund of the European UnionGreek national funds through the Operational Program Competitiveness,Entrepreneurship and Innovation,under the call RESEARCH-CREATE-INNOVATE(project code:T1EDK-04429)。
文摘A philosophy for the design of novel,lightweight,multi-layered armor,referred to as Composite Armor Philosophy(CAP),which can adapt to the passive protection of light-,medium-,and heavy-armored vehicles,is presented in this study.CAP can serve as a guiding principle to assist designers in comprehending the distinct roles fulfilled by each component.The CAP proposal comprises four functional layers,organized in a suggested hierarchy of materials.Particularly notable is the inclusion of a ceramic-composite principle,representing an advanced and innovative solution in the field of armor design.This paper showcases real-world defense industry applications,offering case studies that demonstrate the effectiveness of this advanced approach.CAP represents a significant milestone in the history of passive protection,marking an evolutionary leap in the field.This philosophical approach provides designers with a powerful toolset with which to enhance the protection capabilities of military vehicles,making them more resilient and better equipped to meet the challenges of modern warfare.
基金funded by the National Natural Science Foundation of China(W.Zhang,Grant No.12220101002)Shaanxi Provincial Key Science and Technology Innovation Team(Y.Xu,Grant No.2023-CX-TD-14)+1 种基金the Young Talent Fund of Association for Science and Technology in Shaanxi,China(D.Jia,Grant No.20230240)the Chinese Studentship Council(D.Jia,Grant No.201908060224).
文摘The abalone shell,a composite material whose cross-section is composed of inorganic and organic layers,has high strength and toughness.Inspired by the abalone shell,several multi-layer composite plates with different layer sequences and thicknesses are studied as bullet-proof material in this paper.To investigate the ballistic performance of this multi-layer structure,the complete characterization model and related material parameters of large deformation,failure and fracture ofAl_(2)O_(3)ceramics andCarbon Fiber Reinforced Polymer(CFRP)are studied.Then,3D finite element models of the proposed composite plates with different layer sequences and thicknesses impacted by a 12.7 mm armor-piercing incendiary(API)are built using Abaqus to predict failure.The simulation results show that the CFRP/Al2O3 ceramic/Ultrahigh Molecular Weight Polyethylene(UHMWPE)/CFRP(1 mm/4 mm/4 mm/1 mm)composite is the optimized stack of layers.The simulation results under specified layer sequence and thickness have a reasonable correlation with the experimental results and reflect the failure and fracture of the multi-layer composite protective armor.
基金supported by the National Natural Science Foundation of China(Grant Nos.12172179,U2341244,and 11772160)。
文摘To enhance the protective performance of ceramic composite armor,ballistic penetration experiments were conducted on Al_(2)O_(3) ceramic-ultra-high molecular weight polyethylene(UHMWPE)composite armor with different thickness configurations.The damage and failure modes of hard projectiles and ceramic-fiber composite targets were analyzed.The recovered projectiles and ceramic fragments were sieved and weighed at multiple stages,revealing a positive correlation between the degree of fragmentation of the projectiles and ceramics and the overall ballistic resistance of the composite targets.Numerical simulations were performed using the LS-DYNA finite element software,and the simulation results showed high consistency with the experimental results,confirming the validity of the material parameters.The results indicate that the projectile heads primarily exhibited crushing and abrasive fragmentation.Larger projectile fragments mainly resulted from tensile and shear stress-induced failure.The failure modes of the composite targets included the formation of ceramic cones and radial cracks under high-velocity impacts.The UHMWPE laminated plates exhibited interlayer separation caused by tensile waves,permanent plastic deformation of the rear surface bulging,and perforation failure primarily due to shear forces.Through extended numerical simulations,while maintaining the same areal density and configuration of9 mm Al_(2)O_(3) ceramic+12 mm UHMWPE laminated composite armor,the thickness configurations of the Al_(2)O_(3) ceramic and UHMWPE laminated backplates were varied,and various thicknesses of UHMWPE laminates were simulated as the cover layer for the ceramic panels.The simulation results indicated that the composite armor configuration of 10 mm Al_(2)O_(3) ceramic+8 mm UHMWPE composite armor increased energy absorption by13.48%.When altering the cover layer thickness,a 4 mm UHMWPE+9 mm Al_(2)O_(3)+8 mm UHMWPE composite armor demonstrated a 27.11%improvement in energy absorption,showing a relatively significant enhancement.
文摘The Altomani&Sons Collection owns a remarkable newly discovered portrait of Guidobaldo II della Rovere,Duke of Urbino(1514-1574),a historical military figure who was a condottiere,ruler of Urbino,Commander-in-chief of the Papal Estate,and Perfect of Rome,as well as a collector and patron of the Fine Arts.Camilla Guerrieri Nati(1628-1694),a seventeenth-century Italian painter from Fossombrone(in the province of Pesaro and Urbino),portrayed this heroic personage surrounded by emblems associated with his military courage and leadership,including his plumed burgonet helmet,metal gilded armor,a necklace with the golden fleece,and batons of secular and religious dominions.This oil painting on copper-considered a precious metal at the time-emphasizes the importance of the commission.The material and technique also reveals a unique artistic achievement in that it provides the painting with a smooth,reflective surface and vibrant coloration,symbolizing precious imagery.
文摘In order to restrain the high pumping voltage of braking procedure which is harmful to the system of electric armored vehicle. Based on the analysis of pumping voltage of the braking procedure, the relation between pumping voltage and PWM ratio is derived and a new digital control method to restrain the pumping voltage by changing PWM ratio is put forward. Because the capacitance is decreased effectively, the volume of controller is reduced and the performance to price ratio is improved. The results of computer simulation and experiment proved that this method is feasible and valid.
文摘A numerical model to simulate the bed degradation process in a straight alluvial channel with respect to time and distance is introduced. The simulation takes into account the effect of non uniformity of the bed material, and variations in the dimension of bed forms. The model predicts the changes in the grain size distribution with the time and space during degradation process. The numerical model proposes that the armoring process in degrading channels does not depend only on hydraulic characteristics of the flow but also on variation in the grain size distribution of sediments on the bed. The model was applied and compared with the results obtained from experiments conducted in 24 m recirculating flume for two sizes of sand; a good agreement was found between observed and calculated values.
文摘Sandy inlets are in a dynamic equilibrium between wave-driven littoral drift acting to close them,and tidal flows keeping them open.Their beds are in a continual state of suspension and deposition,so their bathymetry and even location are always in flux.Even so,a nearly linear relationship between an inlet’s cross-sectional flow area and the inshore tidal prism is maintained-except when major wind and/or runoff events act to close or widen an inlet.Inlet location can be stabilized by jetties,but dredging may still be necessary to maintain a navigable channel.Armoring with rock large enough to resist erosion can protect an inlet bed or river mouth from excessive storm flow erosion.Armoring can also be used as a stratagem to close inlets.
