Installing internal bulkheads in a composite bucket foundation alters the rotational symmetry characteristic of a single-compartment bucket foundation,consequently influencing the stress distribution within the bucket...Installing internal bulkheads in a composite bucket foundation alters the rotational symmetry characteristic of a single-compartment bucket foundation,consequently influencing the stress distribution within the bucket and surrounding soil.During the seabed penetration of a spudcan from a jack-up wind turbine installation vessel,an angle may form between the spudcan’s axis and the axis of symmetry of the adjacent composite bucket foundation in the horizontal plane.Such a misalignment may affect load distribution and the non-uniform interaction between the foundation,soil,and spudcan,ultimately influencing the foundation’s stability.This study employs physical model tests to ascertain the trends in end resistance during spudcan penetration in sand,the extent of soil disturbance,and the backflow condition.The finite element coupled Eulerian-Lagrangian method is validated and utilized to determine the range of penetration angles that induce alterations in the maximum vertical displacement and tilt rate of the composite bucket foundation in sand.The differential contact stress distribution at the base of the bucket is analyzed,with qualitative criteria for sand backflow provided.Findings demonstrate that the maximum vertical displacement and tilt rate of the composite bucket foundation display a“wave-like”variation with the increasing spudcan penetration angle,peaking when the angle between the spudcan and bulkhead is the smallest.Stress distribution is predominantly concentrated at the base and apex of the bucket,becoming increasingly uneven as the penetration angle deviates from the foundation’s symmetry axis.The maximum stress gradually shifts to the junction of the bulkhead and bucket bottom on the side with the shortest net distance from the spudcan.Considering the in-place stability and stress state of the composite bucket foundation is therefore imperative,and particular attention should be paid to the foundation’s state when the angle between the spudcan and bulkhead is small.展开更多
A group optimal penetration strategy in complex attack and defense confrontation situation is proposed in this paper to solve the coordinated penetration decision-making problem of endo-atmospheric gliding simultaneou...A group optimal penetration strategy in complex attack and defense confrontation situation is proposed in this paper to solve the coordinated penetration decision-making problem of endo-atmospheric gliding simultaneous multi-missile penetration of interceptors.First,the problem of large search space of multi-missile coordinated penetration maneuvers is fully considered,and the flight corridor of multi-missile coordinated penetration is designed to constrain search space of multi-agent coordinated strategy,comprehensively considering path constraints and anticollision constraints of gliding multi-missile flight.Then,a multi-missile hierarchical coordinated decision-making mechanism based on confrontation situation is proposed,and the swarm penetration strategy is optimized with the goal of maximizing swarm penetration effectiveness.The upper layer plans the swarm penetration formation according to confrontation situation,and generates the swarm coordinated penetration trajectory based on Multi-Agent Deep Deterministic Policy Gradient(MADDPG)method.The lower layer interpolates and smooths penetration trajectory,and generates the penetration guidance command based on Soft Actor-Critic and Extended Proportional Guidance(SAC-EPG)method.Simulation results verify that the proposed multi-missile cooperative penetration method based on hierarchical reinforcement learning converges faster than the penetration method based on MADDPG,and can quickly learn multi-missile cooperative penetration skills.In addition,multi-missile coordination can give full play to the group's detection and maneuverability,and occupy favorable penetration time and space through coordinated ballistic maneuvers.Thus the success rate of group penetration can be improved.展开更多
An experimental and finite element simulation investigation are conducted to study the deformation patterns of steel targets during the penetration process of tungsten alloy long rods,as well as the influence of stren...An experimental and finite element simulation investigation are conducted to study the deformation patterns of steel targets during the penetration process of tungsten alloy long rods,as well as the influence of strength of the target on the deformation patterns.The experimental results revealed slight mass loss in the first layer of the steel target during the transient entrance phase,with an extremely negligible loss in target mass during the quasi-steady penetration phase.The results of macro-analysis,micro-analysis and simulation show that the eroded target material migrated towards the periphery of the crater,causing an increase in the target's thickness,remained within the target,instead of flowing out of the crater.Therefore,the process of long rods penetrating the metal target is considered as a process of backward extrusion.By combining the backward extrusion theory with energy conservation,a penetration depth model for long rods penetrating a metal target,taking into account both the diameter of the crater and the friction coefficient between the rod and the target,has been established.Although the model is not yet perfect,it innovatively applies the principles of solid mechanics to the study of long rod penetration.Additionally,it takes into account the friction coefficient between the rod and the target during the penetration process.Therefore,this model provides a new research direction for future studies on long rod penetration.展开更多
Titanium alloy has the advantages of high strength,strong corrosion resistance,excellent high and low temperature mechanical properties,etc.,and is widely used in aerospace,shipbuilding,weapons and equipment,and other...Titanium alloy has the advantages of high strength,strong corrosion resistance,excellent high and low temperature mechanical properties,etc.,and is widely used in aerospace,shipbuilding,weapons and equipment,and other fields.In recent years,with the continuous increase in demand for medium-thick plate titanium alloys,corresponding welding technologies have also continued to develop.Therefore,this article reviews the research progress of deep penetration welding technology for medium-thick plate titanium alloys,mainly covering traditional arc welding,high-energy beam welding,and other welding technologies.Among many methods,narrow gap welding,hybrid welding,and external energy field assistance welding all contribute to improving the welding efficiency and quality of medium-thick plate titanium alloys.Finally,the development trend of deep penetration welding technology for mediumthick plate titanium alloys is prospected.展开更多
Shaped charge has been widely used for penetrating concrete.However,due to the obvious difference between the propagation of shock waves and explosion products in water and air,the theory governing the formation of sh...Shaped charge has been widely used for penetrating concrete.However,due to the obvious difference between the propagation of shock waves and explosion products in water and air,the theory governing the formation of shaped charge jets in water as well as the underwater penetration effect of concrete need to be studied.In this paper,we introduced a modified forming theory of an underwater hemispherical shaped charge,and investigated the behavior of jet formation and concrete penetration in both air and water experimentally and numerically.The results show that the modified jet forming theory predicts the jet velocity of the hemispherical liner with an error of less than 10%.The underwater jets exhibit at least 3%faster and 11%longer than those in air.Concrete shows different failure modes after penetration in air and water.The depth of penetration deepens at least 18.75%after underwater penetration,accompanied by deeper crater with 65%smaller radius.Moreover,cracks throughout the entire target are formed,whereas cracks exist only near the penetration hole in air.This comprehensive study provides guidance for optimizing the structure of shaped charge and improves the understanding of the permeability effect of concrete in water.展开更多
The penetration-deflagration coupling damage performance of rod-like reactive shaped charge pene-trator(RRSCP)impacting thick steel plates is investigated by theoretical analysis and experiments.A penetration-deflagra...The penetration-deflagration coupling damage performance of rod-like reactive shaped charge pene-trator(RRSCP)impacting thick steel plates is investigated by theoretical analysis and experiments.A penetration-deflagration coupling damage model is developed to predict the penetration depth and cratering diameter.Four type of aluminum-polytetrafluoroethylene-copper(Al-PTFE-Cu)reactive liners with densities of 2.3,2.7,3.5,and 4.5 g·cm^(-3) are selected to conduct the penetration experiments.The comparison results show that model predictions are in good agreement with the experimental data.By comparing the penetration depth and cratering diameter in the inert penetration mode and the penetration-deflagration coupling mode,the influence mechanism that the penetration-induced chemical response is unfavorable to penetration but has an enhanced cratering effect is revealed.From the formation characteristics,penetration effect and penetration-induced chemical reaction be-haviors,the influence of reactive liner density on the penetration-deflagration performance is further analyzed.The results show that increasing the density of reactive liner significantly increases both the kinetic energy and length of the reactive penetrator,meanwhile effectively reduces the weakened effect of penetration-induced chemical response,resulting in an enhanced penetration capability.However,due to the decreased diameter and potential energy content of reactive penetrator,the cratering capa-bility is weakened significantly.展开更多
The chloride penetration resistance of cement-based grout materials was improved by nano-silica emulsion.Specimens of mixtures containing different nano-silica particles or emulsions were exposed in sodium chloride so...The chloride penetration resistance of cement-based grout materials was improved by nano-silica emulsion.Specimens of mixtures containing different nano-silica particles or emulsions were exposed in sodium chloride solutions of specific concentrations with different test ages.Hardened properties of the mixes were assessed in terms of weight loss and compressive strength.X-ray diffraction(XRD)and scanning electron microscopy(SEM)of mixes were performed to analysis the phase evolution and microstructure.The results demonstrated that the introduction of nano-SiO_(2) emulsion significantly decreased the compressive strength loss and calcium hydroxide(CH)crystal content of hydration production,and then enhanced the resistance of cement-based grouting materials to chloride ion penetration.This improvement derives from the filling and pozzolanic effects of nano-SiO_(2) particles,which were incorporated via an emulsion and attributed to a well dispersion in grouting matrix.展开更多
In this paper,the failure caused by HRAM loads which were generated by high-speed projectile penetration,and protection technology of the fluid-filled structure were explored.A bubble was preset on the projectile traj...In this paper,the failure caused by HRAM loads which were generated by high-speed projectile penetration,and protection technology of the fluid-filled structure were explored.A bubble was preset on the projectile trajectory in a fluid-filled structure.Based on the reflection and transmission phenomena of pressure waves at the gas-liquid interface and the compressibility characteristics of gases,a numerical analysis was conducted on the influence of preset bubble on projectile penetration and structural failure characteristics.The results indicate that the secondary water-entry impact phenomenon occurs when a preset bubble exists on the projectile trajectory,leading to the secondary water entry impact loads.The rarefaction waves reflected on the surface of the preset bubble cause the attenuation ratio of the initial impact pressure peak to reach 68.8%and the total specific impulse attenuation ratio to reach 48.6%.Furthermore,the larger the bubble,the faster the projectile,and the more obvious the attenuation effect.Moreover,due to the compressibility of the bubble,the global deformation attenuation ratio of the front and rear walls can reach over 80%.However,the larger the bubble size,the faster the projectile velocity,the smaller the local deformation attenuation effect of the rear wall,and the more severe the failure at the perforation of the rear wall.展开更多
Numerous former military sites worldwide require environmental cleanup from buried unexploded ordnance(UxO)that pose hazards such as leaching toxic chemicals and explosion risks.However,selecting the appropriate mitig...Numerous former military sites worldwide require environmental cleanup from buried unexploded ordnance(UxO)that pose hazards such as leaching toxic chemicals and explosion risks.However,selecting the appropriate mitigation technology relies on prior knowledge of UxO depth of burial(DoB)at specific sites.This study utilizes numerical simulations,employing large deformation explicit finite element(LDEFE)analysis and the Coupled Eulerian-Lagrangian(CEL)approach,to model the penetration of ordnances into clay targets.A modified Tresca constitutive model is implemented in ABAQUS software to capture key features of clay behavior under high strain rate(HSR)loading.The role of various parameters on DoB is investigated,including undrained shear strength,stiffness,and density of the soil.The findings highlight the paramount importance of undrained shear strength in clayey soil penetrability,in addition to the role of soil stiffness,and density.The simulations were employed to calibrate model parameters for Young's empirical penetration model,as well as the Poncelet phenomenological penetration model,demonstrating the efficacy of the numerical simulations in extrapolating its findings within the relevant parameter space.In particular,the calibrated parameters of Young's and Poncelet's models can be identified as a direct function of the various discussed soil properties,which was previously unavailable.展开更多
The study aims to explore the damage characteristics and protection technologies of liquid-filled structures under high-speed projectile impact.A series of penetration impact experiments were conducted by focusing on ...The study aims to explore the damage characteristics and protection technologies of liquid-filled structures under high-speed projectile impact.A series of penetration impact experiments were conducted by focusing on different air layer configurations.By using high-speed camera and dynamic measurement systems,the effects of air layers on the projectile penetration,pressure wave propagation,cavitation evolution,and structural dynamic responses were analyzed.The results showed that the rarefaction wave reflected from the air-liquid interface significantly reduced the peak and specific impulse of the initial pressure wave,thereby diminishing the impact load on the structure.Additionally,the compressibility of air layers also attenuated the cavitation extrusion load.Both front and rear plates exhibited superimposed deformation modes,i.e.,local deformation or petal fracture with global deformation.Air layers effectively mitigated global deformation.However,when the air layer was positioned on the projectile's trajectory,it split the water-entry process and velocity attenuation of the projectile into two relatively independent phases.And the secondary water entry pressure wave caused more severe local deformation and petal fractures on the rear plate.展开更多
The motion characteristics of projectile during oblique penetration into concrete were studied using a three-dimensional meso-scale model.The finite element model validation and parameter chosen were conducted by comp...The motion characteristics of projectile during oblique penetration into concrete were studied using a three-dimensional meso-scale model.The finite element model validation and parameter chosen were conducted by comparing the experimental data,with computational efficiency enhanced through improved mesh refinement.Penetration simulations involving deformable projectiles at various incident angles analyzed the effects of aggregate volume fraction and particle size on ballistic trajectory and terminal deflection.Sensitivity analysis reveals a strong power-law relationship between aggregate content and the projectile's deflection angle.The increase in aggregate content will enhance the confinement effect,shorten the intrusion distance of the projectile,and lead to a decrease in the deflection angle of the projectile.The effect of aggregate particle size on the projectile deflection angle follows a Gaussian distribution.The maximum deflection angle occurs when the aggregate particle size is between 2.7 and 3.1 times the projectile diameter.An increase in particle size reduces the number of aggregate-mortar interfaces at the same aggregate volume fraction,leading to an enlargement of the damage zone in concrete,a decrease in the number of cracks,and an increase in crack length.These findings enhance the understanding of concrete penetration mechanisms and offers valuable insights for engineering structure protection.展开更多
An intelligent endo-atmospheric penetration strategy based on generative adversarialreinforcement learning is proposed in this manuscript.Firstly,attack and defense adversarial mod-els are established,and missile mane...An intelligent endo-atmospheric penetration strategy based on generative adversarialreinforcement learning is proposed in this manuscript.Firstly,attack and defense adversarial mod-els are established,and missile maneuver penetration problem is transformed into an optimal con-trol problem,considering penetration,handover position and mid-terminal guidance velocityconstraints.Then,Radau Pseudospectral method is adopted to generate data samples consideringrandom perturbations.Furthermore,Generative Adversarial Imitation Learning Combined withDeep Deterministic Policy Gradient method(GAIL-DDPG)is designed,with internal processreward signals constructed to tackle long-term sparse reward in missile manuver penetration prob-lem.Finally,penetration strategy is trained and verified.Simulation shows that using generativeadversarial reinforcement learning,with sample library to learn expert experience in training earlystage,the proposed method can quickly converge.Also,performance is further optimized with rein-forcement learning exploration strategy in the later stage of training.Simulation shows that the pro-posed method has better engineering application ability compared with traditional reinforcementlearning method.展开更多
Offshore drilling costs are high,and the downhole environment is even more complex.Improving the rate of penetration(ROP)can effectively shorten offshore drilling cycles and improve economic benefits.It is difficult f...Offshore drilling costs are high,and the downhole environment is even more complex.Improving the rate of penetration(ROP)can effectively shorten offshore drilling cycles and improve economic benefits.It is difficult for the current ROP models to guarantee the prediction accuracy and the robustness of the models at the same time.To address the current issues,a new ROP prediction model was developed in this study,which considers ROP as a time series signal(ROP signal).The model is based on the time convolutional network(TCN)framework and integrates ensemble empirical modal decomposition(EEMD)and Bayesian network causal inference(BN),the model is named EEMD-BN-TCN.Within the proposed model,the EEMD decomposes the original ROP signal into multiple sets of sub-signals.The BN determines the causal relationship between the sub-signals and the key physical parameters(weight on bit and revolutions per minute)and carries out preliminary reconstruction of the sub-signals based on the causal relationship.The TCN predicts signals reconstructed by BN.When applying this model to an actual production well,the average absolute percentage error of the EEMD-BN-TCN prediction decreased from 18.4%with TCN to 9.2%.In addition,compared with other models,the EEMD-BN-TCN can improve the decomposition signal of ROP by regulating weight on bit and revolutions per minute,ultimately enhancing ROP.展开更多
The non-scaling effect on the penetration depth of rigid projectiles is an important issue that must be considered when extending the results of scaled experiments to prototype scenes.In this study,the evolution of th...The non-scaling effect on the penetration depth of rigid projectiles is an important issue that must be considered when extending the results of scaled experiments to prototype scenes.In this study,the evolution of the stress and strain of the target under penetration was analyzed.Expressions for the penetration resistance and penetration depth were obtained based on the conservation equation and continuity condition of the target.The penetration coefficients that characterize the nose shape,target resistance,and non-scaling effect were defined.Simplified calculation methods for the coefficients within the range of rigid projectile penetration were developed.Two methods for estimating the target parameters are proposed.The results show that the non-scaling effect is related to the failure process of the target and depends on the ratio of cavity radius to comminuted region radius.The nose shape coefficient can be approximated as a linear function of the length-to-diameter ratio of the nose.The noseshape coefficient of a flat-nosed projectile is 0.57.The caliber coefficient is related to the projectile diameter and reflects the non-scaling effect,which increases with the projectile diameter.A practical formula for calculating the penetration depth of rigid projectiles considering the non-scaling effect is also proposed.This formula is in good agreement with penetration experiments on rock and concrete.展开更多
Penetration testing plays a critical role in ensuring security in an increasingly interconnected world. Despite advancements in technology leading to smaller, more portable devices, penetration testing remains reliant...Penetration testing plays a critical role in ensuring security in an increasingly interconnected world. Despite advancements in technology leading to smaller, more portable devices, penetration testing remains reliant on traditional laptops and computers, which, while portable, lack true ultra-portability. This paper explores the potential impact of developing a dedicated, ultra-portable, low-cost device for on-the-go penetration testing. Such a device could replicate the core functionalities of advanced penetration testing tools, including those found in Kali Linux, within a compact form factor that fits easily into a pocket. By offering the convenience and portability akin to a smartphone, this innovative device could redefine the way penetration testers operate, enabling them to carry essential tools wherever they go and ensuring they are always prepared to conduct security assessments efficiently. This approach aims to revolutionize penetration testing by merging high functionality with unparalleled portability.展开更多
With the application of hypervelocity weapons in warfare,comprehensively evaluating their destructive effects is of particular interest for protective engineering.Existing studies mostly focused on the depth of penetr...With the application of hypervelocity weapons in warfare,comprehensively evaluating their destructive effects is of particular interest for protective engineering.Existing studies mostly focused on the depth of penetration by hypervelocity projectile,while investigation on stress waves associated with hypervelocity penetration was very limited.To clarify the generation and propagation of stress waves in concrete targets induced by hypervelocity projectile penetration,in the present study,six spherical projectile penetration tests on concrete targets were firstly conducted with projectile velocity ranged from 1875 m/s to 3940 m/s,in which the stress waves were carefully measured by the PVDF transducers.Then corresponding numerical models were developed and validated,and based on the validated numerical model the mechanisms of generation and propagation of stress waves were clarified.It was found that the stress waves observed during hypervelocity penetration are generated by the continuous interactions of projectile and target during penetration,and have unique characteristics such as the directionality and the"two peaks"phenomenon when compared with the stress waves generated by charge explosion.Finally,the effects of projectile velocity,projectile material,and target strength on the stress waves below the penetration depth we re numerically investigated,and two important indexes for evaluating the stress waves by hypervelocity penetration were proposed.展开更多
Boron neutron capture therapy(BNCT)has emerged as a promising treatment for cancers,offering a unique approach to selectively target tumor cells while sparing healthy tissues.Despite its clinical utility,the widesprea...Boron neutron capture therapy(BNCT)has emerged as a promising treatment for cancers,offering a unique approach to selectively target tumor cells while sparing healthy tissues.Despite its clinical utility,the widespread use of fructose-BPA(F-BPA)has been hampered by its limited ability to penetrate the blood-brain barrier(BBB)and potential risks for patients with certain complications such as diabetes,hyperuricemia,and gout,particularly with substantial dosages.Herein,a series of novel BPA derivatives were synthesized.After the primary screening,geniposide-BPA(G-BPA)and salidroside-BPA(S-BPA)exhibited high water solubility,low cytotoxicity and safe profiles for intravenous injection.Furthermore,both G-BPA and S-BPA had demonstrated superior efficacy in vitro against the 4T1 cell line compared with F-BPA.Notably,S-BPA displayed optimal BBB penetration capability,as evidenced by in vitro BBB models and glioblastoma models in vivo,surpassing all other BPA derivative candidates.Meanwhile,GBPA also exhibited enhanced performance relative to the clinical drug F-BPA.In brief,G-BPA and S-BPA,as novel BPA derivatives,demonstrated notable safety profiles and remarkable boron delivery capabilities,thereby offering promising therapeutic options for BNCT in the clinic.展开更多
Drilling optimization requires accurate drill bit rate-of-penetration(ROP)predictions.ROP decreases drilling time and costs and increases rig productivity.This study employs random forest(RF),gradient boosting modelin...Drilling optimization requires accurate drill bit rate-of-penetration(ROP)predictions.ROP decreases drilling time and costs and increases rig productivity.This study employs random forest(RF),gradient boosting modeling(GBM),extreme gradient boosting(XGBoost),and adaptive boosting(Adaboost)models to generate ROP pre-dictions.The models use well data from a 3200-m segment across the stratigraphic column(Dibdibba to Zubair formations)of the large West Qurna oil field in Southern Iraq,penetrating 19 formations and four oil reservoirs.The reservoir sections are between 40 and 440 m thick and consist of both carbonate and clastic lithologies.The ROP predictive models were developed using 14 operational parameters:TVD,weight on bit(WOB),torque,effective circulating density(ECD),drilling rotation per minute(RPM),flow rate,standpipe pressure(SPP),bit size,total RPM,D exponent,gamma ray(GR),density,neutron,caliper,and discrete lithology distribution.Training and validation of the ROP models involves data compiled from three development wells.Applying Random subsampling,the compiled dataset was split into 85%for training and 15%for validation and testing.The test subgroup’s measured and predicted ROP mismatch was assessed using root mean square error(RMSE)and coefficient of correlation(R^(2)).The RF,GBM,and XGBoost models provide ROP predictions versus depth with low errors.Models with cross-validation that integrate data from three wells deliver more accurate ROP pre-dictions than datasets from single well.The input variables’influences on ROP optimization identify the optimal value ranges for 14 operating parameters that help to increase drilling speed and reduce cost.展开更多
To investigate the dynamic response of the cylindrical shell targets to supercavitating projectile transmedium penetration and the penetration mechanism,experiments and numerical simulations were conducted.Simulations...To investigate the dynamic response of the cylindrical shell targets to supercavitating projectile transmedium penetration and the penetration mechanism,experiments and numerical simulations were conducted.Simulations examined the effects of entry water velocity and impact angle on penetration behavior.The results indicate that,upon water entry,the supercavitating projectile transfers its kinetic energy to the surrounding water medium,causing a sudden rise in local pressure.This creates an approximately hemispherical pressure field in the water medium ahead of the nose of the projectile,where the pressure distribution and magnitude are positively correlated with the velocity of the projectile.As the pressure field approaches the cylindrical shell,the area around the impact point experiences pre-stress and deformation due to the hydrodynamic pressure,which is known as the hydrodynamic ram effect.The deformation of the cylindrical shell caused by the hydrodynamic ram effect increases with increasing velocity of the projectile and exhibits a non-linear relationship with the impact angle,first decreasing and then increasing as the impact angle rises.Additionally,the hydrodynamic ram effect leads to greater local deformation and higher peak stresses in the cylindrical shell,which reduces the penetration drag force faced by the projectile in water compared to air,indicating a lower ballistic limit for underwater targets.During the penetration process,as the impact angle increases,the supercavitating projectile undergoes repetitive bending deformation and even brittle fracture,while the failure mode of the target is characterized by ductile hole expansion.Furthermore,the critical penetration velocity required to perforate the cylindrical shell target increases with increasing impact angle.展开更多
The impact of high-velocity penetrators into liquid-filled containers can generate hydrodynamic ram effects,potentially causing catastrophic structural damage to the container.Previous studies have primarily focused o...The impact of high-velocity penetrators into liquid-filled containers can generate hydrodynamic ram effects,potentially causing catastrophic structural damage to the container.Previous studies have primarily focused on undeformed penetrators,such as fragments or bullets,with limited attention directed toward shaped charge jets.This study investigates the penetration characteristics of shaped charge jets impacting behind-armor liquid-filled containers,with particular emphasis on jet-liquid interactions.A theoretical penetration model incorporating material compressibility and jet stretching was developed based on the virtual origin theory.A high-speed imaging experimental system was designed to capture the jet motion within the container.The impact process was numerically reproduced using ANSYS/LSDYNA,and the effects of standoff and overmatch on jet penetration were analyzed.The results reveal that jet stretching induced by increased standoff enhances the penetration velocity of the jet.A proportional relationship between the stretching factor(λ)and the overmatch parameter(I)was identified,withλranging from approximately 1.22 to 1.38 times I across the studied standoff range(80-220 mm).The findings offer a basis for future studies on the pressure distribution in the liquid and the structural response of containers.展开更多
文摘Installing internal bulkheads in a composite bucket foundation alters the rotational symmetry characteristic of a single-compartment bucket foundation,consequently influencing the stress distribution within the bucket and surrounding soil.During the seabed penetration of a spudcan from a jack-up wind turbine installation vessel,an angle may form between the spudcan’s axis and the axis of symmetry of the adjacent composite bucket foundation in the horizontal plane.Such a misalignment may affect load distribution and the non-uniform interaction between the foundation,soil,and spudcan,ultimately influencing the foundation’s stability.This study employs physical model tests to ascertain the trends in end resistance during spudcan penetration in sand,the extent of soil disturbance,and the backflow condition.The finite element coupled Eulerian-Lagrangian method is validated and utilized to determine the range of penetration angles that induce alterations in the maximum vertical displacement and tilt rate of the composite bucket foundation in sand.The differential contact stress distribution at the base of the bucket is analyzed,with qualitative criteria for sand backflow provided.Findings demonstrate that the maximum vertical displacement and tilt rate of the composite bucket foundation display a“wave-like”variation with the increasing spudcan penetration angle,peaking when the angle between the spudcan and bulkhead is the smallest.Stress distribution is predominantly concentrated at the base and apex of the bucket,becoming increasingly uneven as the penetration angle deviates from the foundation’s symmetry axis.The maximum stress gradually shifts to the junction of the bulkhead and bucket bottom on the side with the shortest net distance from the spudcan.Considering the in-place stability and stress state of the composite bucket foundation is therefore imperative,and particular attention should be paid to the foundation’s state when the angle between the spudcan and bulkhead is small.
文摘A group optimal penetration strategy in complex attack and defense confrontation situation is proposed in this paper to solve the coordinated penetration decision-making problem of endo-atmospheric gliding simultaneous multi-missile penetration of interceptors.First,the problem of large search space of multi-missile coordinated penetration maneuvers is fully considered,and the flight corridor of multi-missile coordinated penetration is designed to constrain search space of multi-agent coordinated strategy,comprehensively considering path constraints and anticollision constraints of gliding multi-missile flight.Then,a multi-missile hierarchical coordinated decision-making mechanism based on confrontation situation is proposed,and the swarm penetration strategy is optimized with the goal of maximizing swarm penetration effectiveness.The upper layer plans the swarm penetration formation according to confrontation situation,and generates the swarm coordinated penetration trajectory based on Multi-Agent Deep Deterministic Policy Gradient(MADDPG)method.The lower layer interpolates and smooths penetration trajectory,and generates the penetration guidance command based on Soft Actor-Critic and Extended Proportional Guidance(SAC-EPG)method.Simulation results verify that the proposed multi-missile cooperative penetration method based on hierarchical reinforcement learning converges faster than the penetration method based on MADDPG,and can quickly learn multi-missile cooperative penetration skills.In addition,multi-missile coordination can give full play to the group's detection and maneuverability,and occupy favorable penetration time and space through coordinated ballistic maneuvers.Thus the success rate of group penetration can be improved.
基金supported by the National Natural Science Foundation of China(Grant Nos.12102201,U2341244).
文摘An experimental and finite element simulation investigation are conducted to study the deformation patterns of steel targets during the penetration process of tungsten alloy long rods,as well as the influence of strength of the target on the deformation patterns.The experimental results revealed slight mass loss in the first layer of the steel target during the transient entrance phase,with an extremely negligible loss in target mass during the quasi-steady penetration phase.The results of macro-analysis,micro-analysis and simulation show that the eroded target material migrated towards the periphery of the crater,causing an increase in the target's thickness,remained within the target,instead of flowing out of the crater.Therefore,the process of long rods penetrating the metal target is considered as a process of backward extrusion.By combining the backward extrusion theory with energy conservation,a penetration depth model for long rods penetrating a metal target,taking into account both the diameter of the crater and the friction coefficient between the rod and the target,has been established.Although the model is not yet perfect,it innovatively applies the principles of solid mechanics to the study of long rod penetration.Additionally,it takes into account the friction coefficient between the rod and the target during the penetration process.Therefore,this model provides a new research direction for future studies on long rod penetration.
基金financially supported by the Key Research and Development Program of Ningbo(Grant No.2023Z098)Natural Science Foundation of Inner Mongolia(Grant No.2023MS05040)+1 种基金Shenyang Collaborative Innovation Center Project for Multiple Energy Fields Composite Processing of Special Materials(Grant No.JG210027)Shenyang Key Technology Special Project of The Open Competition Mechanism to Select the Best Solution(Grant Nos.2022210101000827,2022-0-43-048).
文摘Titanium alloy has the advantages of high strength,strong corrosion resistance,excellent high and low temperature mechanical properties,etc.,and is widely used in aerospace,shipbuilding,weapons and equipment,and other fields.In recent years,with the continuous increase in demand for medium-thick plate titanium alloys,corresponding welding technologies have also continued to develop.Therefore,this article reviews the research progress of deep penetration welding technology for medium-thick plate titanium alloys,mainly covering traditional arc welding,high-energy beam welding,and other welding technologies.Among many methods,narrow gap welding,hybrid welding,and external energy field assistance welding all contribute to improving the welding efficiency and quality of medium-thick plate titanium alloys.Finally,the development trend of deep penetration welding technology for mediumthick plate titanium alloys is prospected.
基金supported by the National Science Foundation of China(Grant Nos.12372361,12102427,12372335 and 12102202)the Fundamental Research Funds for the Central Universities(Grant No.30923010908)Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX23_0520).
文摘Shaped charge has been widely used for penetrating concrete.However,due to the obvious difference between the propagation of shock waves and explosion products in water and air,the theory governing the formation of shaped charge jets in water as well as the underwater penetration effect of concrete need to be studied.In this paper,we introduced a modified forming theory of an underwater hemispherical shaped charge,and investigated the behavior of jet formation and concrete penetration in both air and water experimentally and numerically.The results show that the modified jet forming theory predicts the jet velocity of the hemispherical liner with an error of less than 10%.The underwater jets exhibit at least 3%faster and 11%longer than those in air.Concrete shows different failure modes after penetration in air and water.The depth of penetration deepens at least 18.75%after underwater penetration,accompanied by deeper crater with 65%smaller radius.Moreover,cracks throughout the entire target are formed,whereas cracks exist only near the penetration hole in air.This comprehensive study provides guidance for optimizing the structure of shaped charge and improves the understanding of the permeability effect of concrete in water.
基金supported by the National Natural Science Foundation of China(Grant No.12172052)the Foundation of State Key Laboratory of Explosion Science and Safety Protection(Grant No.QKKT24-02).
文摘The penetration-deflagration coupling damage performance of rod-like reactive shaped charge pene-trator(RRSCP)impacting thick steel plates is investigated by theoretical analysis and experiments.A penetration-deflagration coupling damage model is developed to predict the penetration depth and cratering diameter.Four type of aluminum-polytetrafluoroethylene-copper(Al-PTFE-Cu)reactive liners with densities of 2.3,2.7,3.5,and 4.5 g·cm^(-3) are selected to conduct the penetration experiments.The comparison results show that model predictions are in good agreement with the experimental data.By comparing the penetration depth and cratering diameter in the inert penetration mode and the penetration-deflagration coupling mode,the influence mechanism that the penetration-induced chemical response is unfavorable to penetration but has an enhanced cratering effect is revealed.From the formation characteristics,penetration effect and penetration-induced chemical reaction be-haviors,the influence of reactive liner density on the penetration-deflagration performance is further analyzed.The results show that increasing the density of reactive liner significantly increases both the kinetic energy and length of the reactive penetrator,meanwhile effectively reduces the weakened effect of penetration-induced chemical response,resulting in an enhanced penetration capability.However,due to the decreased diameter and potential energy content of reactive penetrator,the cratering capa-bility is weakened significantly.
基金Funded by a Science and Technology Project from the Ministry of Housing and Urban-Rural Development of the People’s Republic of China(No.2019-K-047)Yangzhou Government-Yangzhou University Cooperative Platform Project for Science and Technology Innovation(No.YZ2020262)。
文摘The chloride penetration resistance of cement-based grout materials was improved by nano-silica emulsion.Specimens of mixtures containing different nano-silica particles or emulsions were exposed in sodium chloride solutions of specific concentrations with different test ages.Hardened properties of the mixes were assessed in terms of weight loss and compressive strength.X-ray diffraction(XRD)and scanning electron microscopy(SEM)of mixes were performed to analysis the phase evolution and microstructure.The results demonstrated that the introduction of nano-SiO_(2) emulsion significantly decreased the compressive strength loss and calcium hydroxide(CH)crystal content of hydration production,and then enhanced the resistance of cement-based grouting materials to chloride ion penetration.This improvement derives from the filling and pozzolanic effects of nano-SiO_(2) particles,which were incorporated via an emulsion and attributed to a well dispersion in grouting matrix.
文摘In this paper,the failure caused by HRAM loads which were generated by high-speed projectile penetration,and protection technology of the fluid-filled structure were explored.A bubble was preset on the projectile trajectory in a fluid-filled structure.Based on the reflection and transmission phenomena of pressure waves at the gas-liquid interface and the compressibility characteristics of gases,a numerical analysis was conducted on the influence of preset bubble on projectile penetration and structural failure characteristics.The results indicate that the secondary water-entry impact phenomenon occurs when a preset bubble exists on the projectile trajectory,leading to the secondary water entry impact loads.The rarefaction waves reflected on the surface of the preset bubble cause the attenuation ratio of the initial impact pressure peak to reach 68.8%and the total specific impulse attenuation ratio to reach 48.6%.Furthermore,the larger the bubble,the faster the projectile,and the more obvious the attenuation effect.Moreover,due to the compressibility of the bubble,the global deformation attenuation ratio of the front and rear walls can reach over 80%.However,the larger the bubble size,the faster the projectile velocity,the smaller the local deformation attenuation effect of the rear wall,and the more severe the failure at the perforation of the rear wall.
基金the support of the Strategic Environmental Research and Development Program(SERDP)of the United States of America(Grant No.MR23-3855).
文摘Numerous former military sites worldwide require environmental cleanup from buried unexploded ordnance(UxO)that pose hazards such as leaching toxic chemicals and explosion risks.However,selecting the appropriate mitigation technology relies on prior knowledge of UxO depth of burial(DoB)at specific sites.This study utilizes numerical simulations,employing large deformation explicit finite element(LDEFE)analysis and the Coupled Eulerian-Lagrangian(CEL)approach,to model the penetration of ordnances into clay targets.A modified Tresca constitutive model is implemented in ABAQUS software to capture key features of clay behavior under high strain rate(HSR)loading.The role of various parameters on DoB is investigated,including undrained shear strength,stiffness,and density of the soil.The findings highlight the paramount importance of undrained shear strength in clayey soil penetrability,in addition to the role of soil stiffness,and density.The simulations were employed to calibrate model parameters for Young's empirical penetration model,as well as the Poncelet phenomenological penetration model,demonstrating the efficacy of the numerical simulations in extrapolating its findings within the relevant parameter space.In particular,the calibrated parameters of Young's and Poncelet's models can be identified as a direct function of the various discussed soil properties,which was previously unavailable.
基金the financial support provided by National Natural Science Foundation of China(Grant Nos.52271338,52371342 and 51979277).
文摘The study aims to explore the damage characteristics and protection technologies of liquid-filled structures under high-speed projectile impact.A series of penetration impact experiments were conducted by focusing on different air layer configurations.By using high-speed camera and dynamic measurement systems,the effects of air layers on the projectile penetration,pressure wave propagation,cavitation evolution,and structural dynamic responses were analyzed.The results showed that the rarefaction wave reflected from the air-liquid interface significantly reduced the peak and specific impulse of the initial pressure wave,thereby diminishing the impact load on the structure.Additionally,the compressibility of air layers also attenuated the cavitation extrusion load.Both front and rear plates exhibited superimposed deformation modes,i.e.,local deformation or petal fracture with global deformation.Air layers effectively mitigated global deformation.However,when the air layer was positioned on the projectile's trajectory,it split the water-entry process and velocity attenuation of the projectile into two relatively independent phases.And the secondary water entry pressure wave caused more severe local deformation and petal fractures on the rear plate.
基金funded by the National Natural Science Foundation of China(Grant Nos.12472390 and 12102292)the special fund for Science and Technology Innovation Teams of Shanxi Province(Grant No.202204051002006)。
文摘The motion characteristics of projectile during oblique penetration into concrete were studied using a three-dimensional meso-scale model.The finite element model validation and parameter chosen were conducted by comparing the experimental data,with computational efficiency enhanced through improved mesh refinement.Penetration simulations involving deformable projectiles at various incident angles analyzed the effects of aggregate volume fraction and particle size on ballistic trajectory and terminal deflection.Sensitivity analysis reveals a strong power-law relationship between aggregate content and the projectile's deflection angle.The increase in aggregate content will enhance the confinement effect,shorten the intrusion distance of the projectile,and lead to a decrease in the deflection angle of the projectile.The effect of aggregate particle size on the projectile deflection angle follows a Gaussian distribution.The maximum deflection angle occurs when the aggregate particle size is between 2.7 and 3.1 times the projectile diameter.An increase in particle size reduces the number of aggregate-mortar interfaces at the same aggregate volume fraction,leading to an enlargement of the damage zone in concrete,a decrease in the number of cracks,and an increase in crack length.These findings enhance the understanding of concrete penetration mechanisms and offers valuable insights for engineering structure protection.
文摘An intelligent endo-atmospheric penetration strategy based on generative adversarialreinforcement learning is proposed in this manuscript.Firstly,attack and defense adversarial mod-els are established,and missile maneuver penetration problem is transformed into an optimal con-trol problem,considering penetration,handover position and mid-terminal guidance velocityconstraints.Then,Radau Pseudospectral method is adopted to generate data samples consideringrandom perturbations.Furthermore,Generative Adversarial Imitation Learning Combined withDeep Deterministic Policy Gradient method(GAIL-DDPG)is designed,with internal processreward signals constructed to tackle long-term sparse reward in missile manuver penetration prob-lem.Finally,penetration strategy is trained and verified.Simulation shows that using generativeadversarial reinforcement learning,with sample library to learn expert experience in training earlystage,the proposed method can quickly converge.Also,performance is further optimized with rein-forcement learning exploration strategy in the later stage of training.Simulation shows that the pro-posed method has better engineering application ability compared with traditional reinforcementlearning method.
基金the financial support by the National Natural Science Foundation of China(Grant No.U24B2029)the Key Projects of the National Natural Science Foundation of China(Grant No.52334001)+1 种基金the Strategic Cooperation Technology Projects of CNPC and CUPB(Grand No.ZLZX2020-02)the China University of Petroleum,Beijing(Grand No.ZX20230042)。
文摘Offshore drilling costs are high,and the downhole environment is even more complex.Improving the rate of penetration(ROP)can effectively shorten offshore drilling cycles and improve economic benefits.It is difficult for the current ROP models to guarantee the prediction accuracy and the robustness of the models at the same time.To address the current issues,a new ROP prediction model was developed in this study,which considers ROP as a time series signal(ROP signal).The model is based on the time convolutional network(TCN)framework and integrates ensemble empirical modal decomposition(EEMD)and Bayesian network causal inference(BN),the model is named EEMD-BN-TCN.Within the proposed model,the EEMD decomposes the original ROP signal into multiple sets of sub-signals.The BN determines the causal relationship between the sub-signals and the key physical parameters(weight on bit and revolutions per minute)and carries out preliminary reconstruction of the sub-signals based on the causal relationship.The TCN predicts signals reconstructed by BN.When applying this model to an actual production well,the average absolute percentage error of the EEMD-BN-TCN prediction decreased from 18.4%with TCN to 9.2%.In addition,compared with other models,the EEMD-BN-TCN can improve the decomposition signal of ROP by regulating weight on bit and revolutions per minute,ultimately enhancing ROP.
基金the National Natural Science Foundation of China(Grant Nos.52422808,52378401)to provide funds for this research。
文摘The non-scaling effect on the penetration depth of rigid projectiles is an important issue that must be considered when extending the results of scaled experiments to prototype scenes.In this study,the evolution of the stress and strain of the target under penetration was analyzed.Expressions for the penetration resistance and penetration depth were obtained based on the conservation equation and continuity condition of the target.The penetration coefficients that characterize the nose shape,target resistance,and non-scaling effect were defined.Simplified calculation methods for the coefficients within the range of rigid projectile penetration were developed.Two methods for estimating the target parameters are proposed.The results show that the non-scaling effect is related to the failure process of the target and depends on the ratio of cavity radius to comminuted region radius.The nose shape coefficient can be approximated as a linear function of the length-to-diameter ratio of the nose.The noseshape coefficient of a flat-nosed projectile is 0.57.The caliber coefficient is related to the projectile diameter and reflects the non-scaling effect,which increases with the projectile diameter.A practical formula for calculating the penetration depth of rigid projectiles considering the non-scaling effect is also proposed.This formula is in good agreement with penetration experiments on rock and concrete.
文摘Penetration testing plays a critical role in ensuring security in an increasingly interconnected world. Despite advancements in technology leading to smaller, more portable devices, penetration testing remains reliant on traditional laptops and computers, which, while portable, lack true ultra-portability. This paper explores the potential impact of developing a dedicated, ultra-portable, low-cost device for on-the-go penetration testing. Such a device could replicate the core functionalities of advanced penetration testing tools, including those found in Kali Linux, within a compact form factor that fits easily into a pocket. By offering the convenience and portability akin to a smartphone, this innovative device could redefine the way penetration testers operate, enabling them to carry essential tools wherever they go and ensuring they are always prepared to conduct security assessments efficiently. This approach aims to revolutionize penetration testing by merging high functionality with unparalleled portability.
基金supported by the National Natural Science Foundation of China(Grant Nos.52178515 and 12472399)。
文摘With the application of hypervelocity weapons in warfare,comprehensively evaluating their destructive effects is of particular interest for protective engineering.Existing studies mostly focused on the depth of penetration by hypervelocity projectile,while investigation on stress waves associated with hypervelocity penetration was very limited.To clarify the generation and propagation of stress waves in concrete targets induced by hypervelocity projectile penetration,in the present study,six spherical projectile penetration tests on concrete targets were firstly conducted with projectile velocity ranged from 1875 m/s to 3940 m/s,in which the stress waves were carefully measured by the PVDF transducers.Then corresponding numerical models were developed and validated,and based on the validated numerical model the mechanisms of generation and propagation of stress waves were clarified.It was found that the stress waves observed during hypervelocity penetration are generated by the continuous interactions of projectile and target during penetration,and have unique characteristics such as the directionality and the"two peaks"phenomenon when compared with the stress waves generated by charge explosion.Finally,the effects of projectile velocity,projectile material,and target strength on the stress waves below the penetration depth we re numerically investigated,and two important indexes for evaluating the stress waves by hypervelocity penetration were proposed.
基金supported by Guangdong Basic and Applied Basic Research Foundation(No.2021B1515120065)National Natural Science Foundation of China(Nos.82202339,32271420,82202307)+3 种基金China Postdoctoral Science Foundation(Nos.2022M711527,2021M701640)Science Fund for Creative Research Groups of Nature Science Foundation of Hebei Province(No.B2021201038)National High-End Foreign Expert Recruitment Plan(No.G2022003007L)Natural Science Foundation of Hebei Province(No.B2023201108).
文摘Boron neutron capture therapy(BNCT)has emerged as a promising treatment for cancers,offering a unique approach to selectively target tumor cells while sparing healthy tissues.Despite its clinical utility,the widespread use of fructose-BPA(F-BPA)has been hampered by its limited ability to penetrate the blood-brain barrier(BBB)and potential risks for patients with certain complications such as diabetes,hyperuricemia,and gout,particularly with substantial dosages.Herein,a series of novel BPA derivatives were synthesized.After the primary screening,geniposide-BPA(G-BPA)and salidroside-BPA(S-BPA)exhibited high water solubility,low cytotoxicity and safe profiles for intravenous injection.Furthermore,both G-BPA and S-BPA had demonstrated superior efficacy in vitro against the 4T1 cell line compared with F-BPA.Notably,S-BPA displayed optimal BBB penetration capability,as evidenced by in vitro BBB models and glioblastoma models in vivo,surpassing all other BPA derivative candidates.Meanwhile,GBPA also exhibited enhanced performance relative to the clinical drug F-BPA.In brief,G-BPA and S-BPA,as novel BPA derivatives,demonstrated notable safety profiles and remarkable boron delivery capabilities,thereby offering promising therapeutic options for BNCT in the clinic.
文摘Drilling optimization requires accurate drill bit rate-of-penetration(ROP)predictions.ROP decreases drilling time and costs and increases rig productivity.This study employs random forest(RF),gradient boosting modeling(GBM),extreme gradient boosting(XGBoost),and adaptive boosting(Adaboost)models to generate ROP pre-dictions.The models use well data from a 3200-m segment across the stratigraphic column(Dibdibba to Zubair formations)of the large West Qurna oil field in Southern Iraq,penetrating 19 formations and four oil reservoirs.The reservoir sections are between 40 and 440 m thick and consist of both carbonate and clastic lithologies.The ROP predictive models were developed using 14 operational parameters:TVD,weight on bit(WOB),torque,effective circulating density(ECD),drilling rotation per minute(RPM),flow rate,standpipe pressure(SPP),bit size,total RPM,D exponent,gamma ray(GR),density,neutron,caliper,and discrete lithology distribution.Training and validation of the ROP models involves data compiled from three development wells.Applying Random subsampling,the compiled dataset was split into 85%for training and 15%for validation and testing.The test subgroup’s measured and predicted ROP mismatch was assessed using root mean square error(RMSE)and coefficient of correlation(R^(2)).The RF,GBM,and XGBoost models provide ROP predictions versus depth with low errors.Models with cross-validation that integrate data from three wells deliver more accurate ROP pre-dictions than datasets from single well.The input variables’influences on ROP optimization identify the optimal value ranges for 14 operating parameters that help to increase drilling speed and reduce cost.
基金funded by National Natural Science Foundation of China(Grant Nos.12102202,12372361)the Fundamental Research Funds for the Central Universities(Grant No.30924010833).
文摘To investigate the dynamic response of the cylindrical shell targets to supercavitating projectile transmedium penetration and the penetration mechanism,experiments and numerical simulations were conducted.Simulations examined the effects of entry water velocity and impact angle on penetration behavior.The results indicate that,upon water entry,the supercavitating projectile transfers its kinetic energy to the surrounding water medium,causing a sudden rise in local pressure.This creates an approximately hemispherical pressure field in the water medium ahead of the nose of the projectile,where the pressure distribution and magnitude are positively correlated with the velocity of the projectile.As the pressure field approaches the cylindrical shell,the area around the impact point experiences pre-stress and deformation due to the hydrodynamic pressure,which is known as the hydrodynamic ram effect.The deformation of the cylindrical shell caused by the hydrodynamic ram effect increases with increasing velocity of the projectile and exhibits a non-linear relationship with the impact angle,first decreasing and then increasing as the impact angle rises.Additionally,the hydrodynamic ram effect leads to greater local deformation and higher peak stresses in the cylindrical shell,which reduces the penetration drag force faced by the projectile in water compared to air,indicating a lower ballistic limit for underwater targets.During the penetration process,as the impact angle increases,the supercavitating projectile undergoes repetitive bending deformation and even brittle fracture,while the failure mode of the target is characterized by ductile hole expansion.Furthermore,the critical penetration velocity required to perforate the cylindrical shell target increases with increasing impact angle.
基金the financial support from the National Natural Science Foundation of China(Grant No.11572159)。
文摘The impact of high-velocity penetrators into liquid-filled containers can generate hydrodynamic ram effects,potentially causing catastrophic structural damage to the container.Previous studies have primarily focused on undeformed penetrators,such as fragments or bullets,with limited attention directed toward shaped charge jets.This study investigates the penetration characteristics of shaped charge jets impacting behind-armor liquid-filled containers,with particular emphasis on jet-liquid interactions.A theoretical penetration model incorporating material compressibility and jet stretching was developed based on the virtual origin theory.A high-speed imaging experimental system was designed to capture the jet motion within the container.The impact process was numerically reproduced using ANSYS/LSDYNA,and the effects of standoff and overmatch on jet penetration were analyzed.The results reveal that jet stretching induced by increased standoff enhances the penetration velocity of the jet.A proportional relationship between the stretching factor(λ)and the overmatch parameter(I)was identified,withλranging from approximately 1.22 to 1.38 times I across the studied standoff range(80-220 mm).The findings offer a basis for future studies on the pressure distribution in the liquid and the structural response of containers.
