A deep understanding of the internal ballistic process and the factors affecting it is of primary importance to efficiently design a gun system and ensure its safe management. One of the main goals of internal ballist...A deep understanding of the internal ballistic process and the factors affecting it is of primary importance to efficiently design a gun system and ensure its safe management. One of the main goals of internal ballistics is to estimate the gas pressure into the combustion chamber and the projectile muzzle velocity in order to use the propellant to its higher efficiency while avoiding over-pressure phenomena. Dealing with the internal ballistic problem is a complex undertaking since it requires handling the interaction between different constituents during a transient time lapse with very steep rise of pressure and temperature. Several approaches have been proposed in the literature, based on different assumptions and techniques. Generally, depending on the used mathematical framework, they can be classified into two categories: computational fluid dynamics-based models and lumped-parameter ones. By focusing on gun systems, this paper offers a review of the main contributions in the field by mentioning their advantages and drawbacks. An insight into the limitations of the currently available modelling strategies is provided,as well as some considerations on the choice of one model over another. Lumped-parameter models, for example, are a good candidate for performing parametric analysis and optimisation processes of gun systems, given their minimum requirements of computer resources. Conversely, CFD-based models have a better capacity to address more sophisticated phenomena like pressure waves and turbulent flow effects. The performed review also reveals that too little attention has been given to small calibre guns since the majority of currently available models are conceived for medium and large calibre gun systems.Similarly, aspects like wear phenomena, bore deformations or projectile-barrel interactions still need to be adequately addressed and our suggestion is to dedicate more effort on it.展开更多
To accelerate the practicality of electromagnetic railguns,it is necessary to use a combination of threedimensional numerical simulation and experiments to study the mechanism of bore damage.In this paper,a three-dime...To accelerate the practicality of electromagnetic railguns,it is necessary to use a combination of threedimensional numerical simulation and experiments to study the mechanism of bore damage.In this paper,a three-dimensional numerical model of the augmented railgun with four parallel unconventional rails is introduced to simulate the internal ballistic process and realize the multi-physics field coupling calculation of the rail gun,and a test experiment of a medium-caliber electromagnetic launcher powered by pulse formation network(PFN)is carried out.Various test methods such as spectrometer,fiber grating and high-speed camera are used to test several parameters such as muzzle initial velocity,transient magnetic field strength and stress-strain of rail.Combining the simulation results and experimental data,the damage condition of the contact surface is analyzed.展开更多
Brain tissue is one of the softest parts of the human body,composed of white matter and grey matter.The mechanical behavior of the brain tissue plays an essential role in regulating brain morphology and brain function...Brain tissue is one of the softest parts of the human body,composed of white matter and grey matter.The mechanical behavior of the brain tissue plays an essential role in regulating brain morphology and brain function.Besides,traumatic brain injury(TBI)and various brain diseases are also greatly influenced by the brain's mechanical properties.Whether white matter or grey matter,brain tissue contains multiscale structures composed of neurons,glial cells,fibers,blood vessels,etc.,each with different mechanical properties.As such,brain tissue exhibits complex mechanical behavior,usually with strong nonlinearity,heterogeneity,and directional dependence.Building a constitutive law for multiscale brain tissue using traditional function-based approaches can be very challenging.Instead,this paper proposes a data-driven approach to establish the desired mechanical model of brain tissue.We focus on blood vessels with internal pressure embedded in a white or grey matter matrix material to demonstrate our approach.The matrix is described by an isotropic or anisotropic nonlinear elastic model.A representative unit cell(RUC)with blood vessels is built,which is used to generate the stress-strain data under different internal blood pressure and various proportional displacement loading paths.The generated stress-strain data is then used to train a mechanical law using artificial neural networks to predict the macroscopic mechanical response of brain tissue under different internal pressures.Finally,the trained material model is implemented into finite element software to predict the mechanical behavior of a whole brain under intracranial pressure and distributed body forces.Compared with a direct numerical simulation that employs a reference material model,our proposed approach greatly reduces the computational cost and improves modeling efficiency.The predictions made by our trained model demonstrate sufficient accuracy.Specifically,we find that the level of internal blood pressure can greatly influence stress distribution and determine the possible related damage behaviors.展开更多
This paper investigates the three-dimensional crack propagation and damage evolution process of metallic column shells under internal explosive loading.The calibration of four typical failure parameters for 40CrMnSiB ...This paper investigates the three-dimensional crack propagation and damage evolution process of metallic column shells under internal explosive loading.The calibration of four typical failure parameters for 40CrMnSiB steel was conducted through experiments and subsequently applied to simulations.The numerical simulation results employing the four failure criteria were compared with the differences and similarities observed in freeze-recovery tests and ultra-high-speed tests.This analysis addressed the critical issue of determining failure criteria for the fracture of a metal shell under internal explosive loads.Building upon this foundation,the damage parameter D_(c),linked to the cumulative crack density,was defined based on the evolution characteristics of a substantial number of cracks.The relationship between the damage parameter and crack velocity over time was established,and the influence of the internal central pressure on the damage parameter and crack velocity was investigated.Variations in the fracture modes were found under different failure criteria,with the principal strain failure criterion proving to be the most effective for simulating 3D crack propagation in a pure shear fracture mode.Through statistical analysis of the shell penetration fracture radius data,it was determined that the fracture radius remained essentially constant during the crack evolution process and could be considered a constant.The propagation velocity of axial cracks ranged between 5300 m/s and 12600 m/s,surpassing the Rayleigh wave velocity of the shell material and decreasing linearly with time.The increase in shell damage exhibited an initial rapid phase,followed by deceleration,demonstrating accelerated damage during the propagation stage of the blast wave and decelerated damage after the arrival of the rarefaction wave.This study provides an effective approach for investigating crack propagation and damage evolution.The derived crack propagation and damage evolution law serves as a valuable reference for the development of crack velocity theory and the construction of shell damage evolution modes.展开更多
You are cordially invited to the 40th Topical Meeting of the International Society of Electrochemistry,which will be held from 15 to 17 August 2025 in Changchun,China.Changchun is a City of Science,Education,and Resor...You are cordially invited to the 40th Topical Meeting of the International Society of Electrochemistry,which will be held from 15 to 17 August 2025 in Changchun,China.Changchun is a City of Science,Education,and Resort with a population of more than 9 million.展开更多
Xiamen,China-June 22-25,2025-The 2nd International Symposium on AI for Electrochemistry(iSAIEC 2025)was grandly held at Xiamen University.The International Society of Electrochemistry(ISE)first joining as a co-organiz...Xiamen,China-June 22-25,2025-The 2nd International Symposium on AI for Electrochemistry(iSAIEC 2025)was grandly held at Xiamen University.The International Society of Electrochemistry(ISE)first joining as a co-organizer supports"Poster Prize"to honor outstanding contributions from young researchers.展开更多
A novel control scheme of active disturbance rejection internal model control(ADRIMC) is proposed to improve the anti-interference ability and robustness for the dead-time process. The active anti-interference concept...A novel control scheme of active disturbance rejection internal model control(ADRIMC) is proposed to improve the anti-interference ability and robustness for the dead-time process. The active anti-interference concept is introduced into the internal model control(IMC) by analyzing the relationship between IMC and disturbance observer control(DOB). Further, a design process of disturbance filter is presented to realize the active anti-interference ability for ADRIMC scheme. The disturbance filter is used to estimate an equivalent disturbance consisting of both external disturbances and internal disturbances caused by model mismatches.Simulation results demonstrate that the proposed method possesses a good disturbance rejection performance, though losing some partial dynamic performance. In other words, the proposed method shows a tradeoff between the dynamic performance and the system robust.展开更多
The new forming process of AA6061 alloy tube, including solution treatment, granule medium internal high-pressure forming and aging treatment, was developed. The AA6061 alloy tube via heat treatment satisfied the form...The new forming process of AA6061 alloy tube, including solution treatment, granule medium internal high-pressure forming and aging treatment, was developed. The AA6061 alloy tube via heat treatment satisfied the forming requirement, and the granule medium internal high pressure forming method for AA6061 alloy tube was also realized by using convenient implementation with low requirement of equipment and flexible design of product. At a solution temperature of 560℃ and time of 120 min, the elongation of the AA6061 extruded tube increases by 300% and the strength and the hardness dramatically decrease too. Therefore, the AA6061 alloy tube meets the requirement of internal high-pressure forming because of the improvement of formability. The experiments shows that the strength and hardness of AA6061 alloy workpiece recover to that of the as-received alloy at an aging temperature of 180℃ and time of 360 min, and the strength of AA6061 alloy workpiece is equal to the base alloy. The typical parts of convex ring tube, stepped shaft tube and hexagonal tube were successfully produced in lab by using the present forming method. The forming tests show that the maximum expansion ratio(MER) of the AA6061 extruded tube increases by 25.5% and the material properties of formed AA6061 alloy tube reached the performance of as-received alloy.展开更多
The desire for increased performance from guns is driving the charge designer towards charges that present challenges to numerical modelling.There is a pressing need for accurate,validated ignition and combustion mode...The desire for increased performance from guns is driving the charge designer towards charges that present challenges to numerical modelling.There is a pressing need for accurate,validated ignition and combustion models that can be used to predict the performance of advanced charges and ensure pressure waves are not developed or,if they are,then they can be managed.This paper describes efforts to model complex charge designs using a two-dimensional axi-symmetric multi-phase flow internal ballistics model.展开更多
An adaptive internal mode control is proposed to eliminate effectively periodic disturbance with uncertain frequency caused by input error angle of PIGA （Pendulous Integrating Gyro Accelerometer）. An adaptive algori...An adaptive internal mode control is proposed to eliminate effectively periodic disturbance with uncertain frequency caused by input error angle of PIGA （Pendulous Integrating Gyro Accelerometer）. An adaptive algorithm with periodic disturbance frequency identification on line is applied and the internal model controller parameters are adjusted to eliminate disturbance. Then the convergence of this algorithm and the stability of the system are proved by the averaging method. Simulation results verify the proposed scheme can eliminate periodic disturbance and improve the test precision for PIGA effectively.展开更多
The equations governing wind-induced internal pressure responses for a two-compartment building with a dominant opening and background porosity were derived.The unsteady form of the Bernoulli equation,the law of mass ...The equations governing wind-induced internal pressure responses for a two-compartment building with a dominant opening and background porosity were derived.The unsteady form of the Bernoulli equation,the law of mass conservation,and adiabatic equation were used for the derivation.The precision of the governing equations was verified by a wind tunnel test on a rigid model of a low-rise building.The results show that the governing equations can effectively analyze the wind-induced internal pressure responses.The internal pressure responses in both compartments are suppressed due to the additional damping provided by background porosity.The responses of internal pressure in both compartments,especially in the compartment without an external opening,decrease with increased lumped leakage area.展开更多
Aiming at the issue of sliding ratio,an internal gear pair is proposed which consists of an involute internal gear and a pinion with quadratic curve teeth.Particularly,the contact pattern is point contact and the pini...Aiming at the issue of sliding ratio,an internal gear pair is proposed which consists of an involute internal gear and a pinion with quadratic curve teeth.Particularly,the contact pattern is point contact and the pinion is generated based on an involute gear.The generation method and mathematical models of the gear pair are presented.The sliding ratio is calculated and the general calculation formulas of sliding ratios are developed.Also,the comparison between the involute gear and proposed gear is made.The adaptability of center distance and contact stress are also discussed.In addition,the gear pair was manufactured and inspected according to the exactitude solid model of the gear pair.In order to confirm this model to be effective,the efficiency experiment and the contrast experiment with the involute gear pair were performed.Furthermore,these two types of pinions were analyzed by scanning electron microscope and wear depths were measured by measuring center.The experiment results show that the efficiency of the internal gear pair is stable at a range about 97.1%to 98.6%and wear depth is less than 50%of the involute gear pair.The internal gear pair is expected to have excellent transmission performance.展开更多
This paper presents a combination of experimental and numerical investigations on the dynamic response of scaling cabin structures under internal blast loading.The purpose of this study is to modify the similar relati...This paper presents a combination of experimental and numerical investigations on the dynamic response of scaling cabin structures under internal blast loading.The purpose of this study is to modify the similar relationship between the scaled-down model and the prototype of the cabin structures under internal blast loading.According to the Hopkinson’s scaling law,three sets of cabin structure models with different scaling factors combined with different explosive masses were designed for the experimental study.The dynamic deformation process of the models was recorded by a three-dimensional digital imaging correlation(DIC)method and a 3D scanning technology was used to reconstruct the deformation modes of the specimen.In addition,a finite element model was developed for the modification of the scaling law.The experimental results showed that the final deflection-to-thickness ratio was increased with the increase of the model size despite of the similar trend of their deformation processes.The reason for this inconsistency was discussed based on the traditional scaling law and a modified formula considering of the effects of size and strain-rate was provided.展开更多
Non-cylindrical casings filled with explosives have undergone rapid development in warhead design and explosion control.The fragment spatial distribution of prismatic casings is more complex than that of traditional c...Non-cylindrical casings filled with explosives have undergone rapid development in warhead design and explosion control.The fragment spatial distribution of prismatic casings is more complex than that of traditional cylindrical casings.In this study,numerical and experimental investigations into the fragment spatial distribution of a prismatic casing were conducted.A new numerical method,which adds the Lagrangian marker points to the Eulerian grid,was proposed to track the multi-material interfaces and material dynamic fractures.Physical quantity mappings between the Lagrangian marker points and Eulerian grid were achieved by their topological relationship.Thereafter,the fragment spatial distributions of the prismatic casing with different fragment sizes,fragment shapes,and casing geometries were obtained using the numerical method.Moreover,fragment spatial distribution experiments were conducted on the prismatic casing with different fragment sizes and shapes,and the experimental data were compared with the numerical results.The effects of the fragment and casing geometry on the fragment spatial distributions were determined by analyzing the numerical results and experimental data.Finally,a formula including the casing geometry parameters was fitted to predict the fragment spatial distribution of the prismatic casing under internal explosive loading.展开更多
The thermal elasto-hydrodynamic lubrication characteristics of the internal meshing gears in a planetary gear train under vibrations were examined considering the influence of the modification coefficient and time-var...The thermal elasto-hydrodynamic lubrication characteristics of the internal meshing gears in a planetary gear train under vibrations were examined considering the influence of the modification coefficient and time-varying meshing stiffness.Based on dynamic theory of the gear system,a dynamic model of the planetary gear train was established.The lubrication performances of modified gear systems under vibrations and static loads were analyzed.Compared with other transmission types,the best lubrication effect could be produced by the positive transmission.A thicker lubricating oil film could be formed,and the friction coefficient and oil film flash temperature are the smallest.Increasing modification coefficient improves the lubrication performance continuously but intensifies the engage-in and tooth-change impact.For the planetary and inner gears,the increase in the modification coefficient also leads a decrease in the oil film stiffness.展开更多
The start-up of external circulationadded internal circulation(IC) reactor was finished in 26 d, 32 d fewer than that of IC reactor. To evaluate the influence of the added external circulation on the development of gr...The start-up of external circulationadded internal circulation(IC) reactor was finished in 26 d, 32 d fewer than that of IC reactor. To evaluate the influence of the added external circulation on the development of granular sludge, the characteristics of the granular sludge taken from the two tested laboratory-scale reactors during start-up were studied. The results show that the added external circulation can enhance biomass granulation, accelerate granule development and improve sludge characteristics. At the end of start-up, the granular size of sludge in external circulation-added IC reactor greatly increases with a size distribution much better than that of sludge in IC reactor. The granular sludge originated from external circulationadded IC reactor contains more extracellular polymers and has a greater settling velocity than that from IC reactor. Methanogenic activity of the granular sludge from the external circulationadded IC reactor started 26 d ago reaches 358.23mL·g -1 ·d -1 , 1.66 and 1.20 times as great as that of the sludge from the IC reactor started 26 d and 58 d ago respectively.展开更多
The basic difference non-equal interval model GM(1,1) in grey theory was used to fit and forecast data series with non-equal lengths and different inertias, acquired from oil monitoring of internal combustion engines....The basic difference non-equal interval model GM(1,1) in grey theory was used to fit and forecast data series with non-equal lengths and different inertias, acquired from oil monitoring of internal combustion engines. The fitted and forecasted results show that the length or inertia of a sequence affects its precision very much, i.e. the bigger the inertia of a sequence is, or the shorter the length of a series is, the less the errors of fitted and forecasted results are. Based on the research results, it is suggested that short series should be applied to be fitted and forecasted; for longer series, the newer datum should be applied instead of the older datum to be analyzed by non- equalinterval GM(1,1) to improve the forecasted and fitted precision, and that data sequence should be verified to satisfy the conditions of grey forecasting.展开更多
For rigid-flexible coupling multi-body with variable topology,such as the system of internally carried air-launched or heavy cargo airdrop,in order to construct a dynamic model with unified form,avoid redundancy in th...For rigid-flexible coupling multi-body with variable topology,such as the system of internally carried air-launched or heavy cargo airdrop,in order to construct a dynamic model with unified form,avoid redundancy in the modeling process and make the solution independent,a method based on the equivalent rigidization model was proposed.It divides a system into independent subsystems by cutting off the joints,of which types are changed with the operation process of the system.And models of different subsystems can be constructed via selecting suitable modeling methods.Subsystem models with flexible bodies are on the basis of the equivalent rigidization model which replaces the flexible bodies with the virtual rigid bodies.And the solution for sanction,which is based on the constraints force algorithm(CFA)and vector mechanics,can be independent on the state equations.The internally carried air-launched system was taken as an example for verifying validity and feasibility of the method and theory.The dynamic model of aircraft-rocket-parachute system in the entire phase was constructed.Comparing the modeling method with the others,the modeling process was programmed;and form of the model is unified and simple.The model,method and theory can be used to analyze other similar systems such as heavy cargo airdrop system and capsule parachute recovery system.展开更多
A dynamical moving pressure structural numerical calculation model using the internal ballistics calculation pressure-time results was constituted and the vicinity of the internal ballistics and quasiinternal ballisti...A dynamical moving pressure structural numerical calculation model using the internal ballistics calculation pressure-time results was constituted and the vicinity of the internal ballistics and quasiinternal ballistics structural model was checked. The Von Mises stresses obtained by the dynamical structural numerical model calculations and the Von Mises stresses calculated from the shot test strain measurements were compared. The difference for the worse case was 20% and for the best case was 0.1%.Furthermore, the model gave better agreement for the higher charge masses. The numerical structural quasi-internal ballistics computation model created was verified for the top charge mass which represents the highest stress condition and used in a gun barrel design.展开更多
基金the support provided by the Royal Higher Institute for Defence (RHID) of the Belgian Defence, which has contributed to the progress of this ongoing research.
文摘A deep understanding of the internal ballistic process and the factors affecting it is of primary importance to efficiently design a gun system and ensure its safe management. One of the main goals of internal ballistics is to estimate the gas pressure into the combustion chamber and the projectile muzzle velocity in order to use the propellant to its higher efficiency while avoiding over-pressure phenomena. Dealing with the internal ballistic problem is a complex undertaking since it requires handling the interaction between different constituents during a transient time lapse with very steep rise of pressure and temperature. Several approaches have been proposed in the literature, based on different assumptions and techniques. Generally, depending on the used mathematical framework, they can be classified into two categories: computational fluid dynamics-based models and lumped-parameter ones. By focusing on gun systems, this paper offers a review of the main contributions in the field by mentioning their advantages and drawbacks. An insight into the limitations of the currently available modelling strategies is provided,as well as some considerations on the choice of one model over another. Lumped-parameter models, for example, are a good candidate for performing parametric analysis and optimisation processes of gun systems, given their minimum requirements of computer resources. Conversely, CFD-based models have a better capacity to address more sophisticated phenomena like pressure waves and turbulent flow effects. The performed review also reveals that too little attention has been given to small calibre guns since the majority of currently available models are conceived for medium and large calibre gun systems.Similarly, aspects like wear phenomena, bore deformations or projectile-barrel interactions still need to be adequately addressed and our suggestion is to dedicate more effort on it.
文摘To accelerate the practicality of electromagnetic railguns,it is necessary to use a combination of threedimensional numerical simulation and experiments to study the mechanism of bore damage.In this paper,a three-dimensional numerical model of the augmented railgun with four parallel unconventional rails is introduced to simulate the internal ballistic process and realize the multi-physics field coupling calculation of the rail gun,and a test experiment of a medium-caliber electromagnetic launcher powered by pulse formation network(PFN)is carried out.Various test methods such as spectrometer,fiber grating and high-speed camera are used to test several parameters such as muzzle initial velocity,transient magnetic field strength and stress-strain of rail.Combining the simulation results and experimental data,the damage condition of the contact surface is analyzed.
文摘Brain tissue is one of the softest parts of the human body,composed of white matter and grey matter.The mechanical behavior of the brain tissue plays an essential role in regulating brain morphology and brain function.Besides,traumatic brain injury(TBI)and various brain diseases are also greatly influenced by the brain's mechanical properties.Whether white matter or grey matter,brain tissue contains multiscale structures composed of neurons,glial cells,fibers,blood vessels,etc.,each with different mechanical properties.As such,brain tissue exhibits complex mechanical behavior,usually with strong nonlinearity,heterogeneity,and directional dependence.Building a constitutive law for multiscale brain tissue using traditional function-based approaches can be very challenging.Instead,this paper proposes a data-driven approach to establish the desired mechanical model of brain tissue.We focus on blood vessels with internal pressure embedded in a white or grey matter matrix material to demonstrate our approach.The matrix is described by an isotropic or anisotropic nonlinear elastic model.A representative unit cell(RUC)with blood vessels is built,which is used to generate the stress-strain data under different internal blood pressure and various proportional displacement loading paths.The generated stress-strain data is then used to train a mechanical law using artificial neural networks to predict the macroscopic mechanical response of brain tissue under different internal pressures.Finally,the trained material model is implemented into finite element software to predict the mechanical behavior of a whole brain under intracranial pressure and distributed body forces.Compared with a direct numerical simulation that employs a reference material model,our proposed approach greatly reduces the computational cost and improves modeling efficiency.The predictions made by our trained model demonstrate sufficient accuracy.Specifically,we find that the level of internal blood pressure can greatly influence stress distribution and determine the possible related damage behaviors.
基金supported by the National Natural Science Foundation of China (Grant No.12302437)Natural Science Foundation of Jiangsu Province (BK20230939)China Postdoctoral Science Foundation (2021M701710)。
文摘This paper investigates the three-dimensional crack propagation and damage evolution process of metallic column shells under internal explosive loading.The calibration of four typical failure parameters for 40CrMnSiB steel was conducted through experiments and subsequently applied to simulations.The numerical simulation results employing the four failure criteria were compared with the differences and similarities observed in freeze-recovery tests and ultra-high-speed tests.This analysis addressed the critical issue of determining failure criteria for the fracture of a metal shell under internal explosive loads.Building upon this foundation,the damage parameter D_(c),linked to the cumulative crack density,was defined based on the evolution characteristics of a substantial number of cracks.The relationship between the damage parameter and crack velocity over time was established,and the influence of the internal central pressure on the damage parameter and crack velocity was investigated.Variations in the fracture modes were found under different failure criteria,with the principal strain failure criterion proving to be the most effective for simulating 3D crack propagation in a pure shear fracture mode.Through statistical analysis of the shell penetration fracture radius data,it was determined that the fracture radius remained essentially constant during the crack evolution process and could be considered a constant.The propagation velocity of axial cracks ranged between 5300 m/s and 12600 m/s,surpassing the Rayleigh wave velocity of the shell material and decreasing linearly with time.The increase in shell damage exhibited an initial rapid phase,followed by deceleration,demonstrating accelerated damage during the propagation stage of the blast wave and decelerated damage after the arrival of the rarefaction wave.This study provides an effective approach for investigating crack propagation and damage evolution.The derived crack propagation and damage evolution law serves as a valuable reference for the development of crack velocity theory and the construction of shell damage evolution modes.
文摘You are cordially invited to the 40th Topical Meeting of the International Society of Electrochemistry,which will be held from 15 to 17 August 2025 in Changchun,China.Changchun is a City of Science,Education,and Resort with a population of more than 9 million.
文摘Xiamen,China-June 22-25,2025-The 2nd International Symposium on AI for Electrochemistry(iSAIEC 2025)was grandly held at Xiamen University.The International Society of Electrochemistry(ISE)first joining as a co-organizer supports"Poster Prize"to honor outstanding contributions from young researchers.
基金Project(61273132)supported by the National Natural Foundation of ChinaProject(20110010010)supported by Higher School Specialized Research Fund for the Doctoral Program,China
文摘A novel control scheme of active disturbance rejection internal model control(ADRIMC) is proposed to improve the anti-interference ability and robustness for the dead-time process. The active anti-interference concept is introduced into the internal model control(IMC) by analyzing the relationship between IMC and disturbance observer control(DOB). Further, a design process of disturbance filter is presented to realize the active anti-interference ability for ADRIMC scheme. The disturbance filter is used to estimate an equivalent disturbance consisting of both external disturbances and internal disturbances caused by model mismatches.Simulation results demonstrate that the proposed method possesses a good disturbance rejection performance, though losing some partial dynamic performance. In other words, the proposed method shows a tradeoff between the dynamic performance and the system robust.
基金Project(51305386)supported by the National Natural Science Foundation of ChinaProject(E2013203093)supported by the Natural Science Foundation of Hebei Province,China
文摘The new forming process of AA6061 alloy tube, including solution treatment, granule medium internal high-pressure forming and aging treatment, was developed. The AA6061 alloy tube via heat treatment satisfied the forming requirement, and the granule medium internal high pressure forming method for AA6061 alloy tube was also realized by using convenient implementation with low requirement of equipment and flexible design of product. At a solution temperature of 560℃ and time of 120 min, the elongation of the AA6061 extruded tube increases by 300% and the strength and the hardness dramatically decrease too. Therefore, the AA6061 alloy tube meets the requirement of internal high-pressure forming because of the improvement of formability. The experiments shows that the strength and hardness of AA6061 alloy workpiece recover to that of the as-received alloy at an aging temperature of 180℃ and time of 360 min, and the strength of AA6061 alloy workpiece is equal to the base alloy. The typical parts of convex ring tube, stepped shaft tube and hexagonal tube were successfully produced in lab by using the present forming method. The forming tests show that the maximum expansion ratio(MER) of the AA6061 extruded tube increases by 25.5% and the material properties of formed AA6061 alloy tube reached the performance of as-received alloy.
文摘The desire for increased performance from guns is driving the charge designer towards charges that present challenges to numerical modelling.There is a pressing need for accurate,validated ignition and combustion models that can be used to predict the performance of advanced charges and ensure pressure waves are not developed or,if they are,then they can be managed.This paper describes efforts to model complex charge designs using a two-dimensional axi-symmetric multi-phase flow internal ballistics model.
文摘An adaptive internal mode control is proposed to eliminate effectively periodic disturbance with uncertain frequency caused by input error angle of PIGA （Pendulous Integrating Gyro Accelerometer）. An adaptive algorithm with periodic disturbance frequency identification on line is applied and the internal model controller parameters are adjusted to eliminate disturbance. Then the convergence of this algorithm and the stability of the system are proved by the averaging method. Simulation results verify the proposed scheme can eliminate periodic disturbance and improve the test precision for PIGA effectively.
基金Project(90715040) supported by the Major Research Program of the National Natural Science Foundation of ChinaProject(50878159) supported by the General Program of the National Natural Science Foundation of China
文摘The equations governing wind-induced internal pressure responses for a two-compartment building with a dominant opening and background porosity were derived.The unsteady form of the Bernoulli equation,the law of mass conservation,and adiabatic equation were used for the derivation.The precision of the governing equations was verified by a wind tunnel test on a rigid model of a low-rise building.The results show that the governing equations can effectively analyze the wind-induced internal pressure responses.The internal pressure responses in both compartments are suppressed due to the additional damping provided by background porosity.The responses of internal pressure in both compartments,especially in the compartment without an external opening,decrease with increased lumped leakage area.
基金Project(51575062)supported by the National Natural Science Foundation of ChinaProject(SM2014D202)supported by the Fund of Shanghai Key Laboratory of Spacecraft Mechanism,China
文摘Aiming at the issue of sliding ratio,an internal gear pair is proposed which consists of an involute internal gear and a pinion with quadratic curve teeth.Particularly,the contact pattern is point contact and the pinion is generated based on an involute gear.The generation method and mathematical models of the gear pair are presented.The sliding ratio is calculated and the general calculation formulas of sliding ratios are developed.Also,the comparison between the involute gear and proposed gear is made.The adaptability of center distance and contact stress are also discussed.In addition,the gear pair was manufactured and inspected according to the exactitude solid model of the gear pair.In order to confirm this model to be effective,the efficiency experiment and the contrast experiment with the involute gear pair were performed.Furthermore,these two types of pinions were analyzed by scanning electron microscope and wear depths were measured by measuring center.The experiment results show that the efficiency of the internal gear pair is stable at a range about 97.1%to 98.6%and wear depth is less than 50%of the involute gear pair.The internal gear pair is expected to have excellent transmission performance.
基金the support from the National Natural Science Foundation of China under Grant No. 11902031,No. 11802030 , No. 11802031Beijing Municipal Science and Technology Project Management Approach under No. Z181100004118002
文摘This paper presents a combination of experimental and numerical investigations on the dynamic response of scaling cabin structures under internal blast loading.The purpose of this study is to modify the similar relationship between the scaled-down model and the prototype of the cabin structures under internal blast loading.According to the Hopkinson’s scaling law,three sets of cabin structure models with different scaling factors combined with different explosive masses were designed for the experimental study.The dynamic deformation process of the models was recorded by a three-dimensional digital imaging correlation(DIC)method and a 3D scanning technology was used to reconstruct the deformation modes of the specimen.In addition,a finite element model was developed for the modification of the scaling law.The experimental results showed that the final deflection-to-thickness ratio was increased with the increase of the model size despite of the similar trend of their deformation processes.The reason for this inconsistency was discussed based on the traditional scaling law and a modified formula considering of the effects of size and strain-rate was provided.
基金supported by the National Natural Science Foundation of China(Grant No.11822203and 11702026)。
文摘Non-cylindrical casings filled with explosives have undergone rapid development in warhead design and explosion control.The fragment spatial distribution of prismatic casings is more complex than that of traditional cylindrical casings.In this study,numerical and experimental investigations into the fragment spatial distribution of a prismatic casing were conducted.A new numerical method,which adds the Lagrangian marker points to the Eulerian grid,was proposed to track the multi-material interfaces and material dynamic fractures.Physical quantity mappings between the Lagrangian marker points and Eulerian grid were achieved by their topological relationship.Thereafter,the fragment spatial distributions of the prismatic casing with different fragment sizes,fragment shapes,and casing geometries were obtained using the numerical method.Moreover,fragment spatial distribution experiments were conducted on the prismatic casing with different fragment sizes and shapes,and the experimental data were compared with the numerical results.The effects of the fragment and casing geometry on the fragment spatial distributions were determined by analyzing the numerical results and experimental data.Finally,a formula including the casing geometry parameters was fitted to predict the fragment spatial distribution of the prismatic casing under internal explosive loading.
基金Projects(51575289,51705270)supported by the National Natural Science Foundation of China。
文摘The thermal elasto-hydrodynamic lubrication characteristics of the internal meshing gears in a planetary gear train under vibrations were examined considering the influence of the modification coefficient and time-varying meshing stiffness.Based on dynamic theory of the gear system,a dynamic model of the planetary gear train was established.The lubrication performances of modified gear systems under vibrations and static loads were analyzed.Compared with other transmission types,the best lubrication effect could be produced by the positive transmission.A thicker lubricating oil film could be formed,and the friction coefficient and oil film flash temperature are the smallest.Increasing modification coefficient improves the lubrication performance continuously but intensifies the engage-in and tooth-change impact.For the planetary and inner gears,the increase in the modification coefficient also leads a decrease in the oil film stiffness.
文摘The start-up of external circulationadded internal circulation(IC) reactor was finished in 26 d, 32 d fewer than that of IC reactor. To evaluate the influence of the added external circulation on the development of granular sludge, the characteristics of the granular sludge taken from the two tested laboratory-scale reactors during start-up were studied. The results show that the added external circulation can enhance biomass granulation, accelerate granule development and improve sludge characteristics. At the end of start-up, the granular size of sludge in external circulation-added IC reactor greatly increases with a size distribution much better than that of sludge in IC reactor. The granular sludge originated from external circulationadded IC reactor contains more extracellular polymers and has a greater settling velocity than that from IC reactor. Methanogenic activity of the granular sludge from the external circulationadded IC reactor started 26 d ago reaches 358.23mL·g -1 ·d -1 , 1.66 and 1.20 times as great as that of the sludge from the IC reactor started 26 d and 58 d ago respectively.
文摘The basic difference non-equal interval model GM(1,1) in grey theory was used to fit and forecast data series with non-equal lengths and different inertias, acquired from oil monitoring of internal combustion engines. The fitted and forecasted results show that the length or inertia of a sequence affects its precision very much, i.e. the bigger the inertia of a sequence is, or the shorter the length of a series is, the less the errors of fitted and forecasted results are. Based on the research results, it is suggested that short series should be applied to be fitted and forecasted; for longer series, the newer datum should be applied instead of the older datum to be analyzed by non- equalinterval GM(1,1) to improve the forecasted and fitted precision, and that data sequence should be verified to satisfy the conditions of grey forecasting.
文摘For rigid-flexible coupling multi-body with variable topology,such as the system of internally carried air-launched or heavy cargo airdrop,in order to construct a dynamic model with unified form,avoid redundancy in the modeling process and make the solution independent,a method based on the equivalent rigidization model was proposed.It divides a system into independent subsystems by cutting off the joints,of which types are changed with the operation process of the system.And models of different subsystems can be constructed via selecting suitable modeling methods.Subsystem models with flexible bodies are on the basis of the equivalent rigidization model which replaces the flexible bodies with the virtual rigid bodies.And the solution for sanction,which is based on the constraints force algorithm(CFA)and vector mechanics,can be independent on the state equations.The internally carried air-launched system was taken as an example for verifying validity and feasibility of the method and theory.The dynamic model of aircraft-rocket-parachute system in the entire phase was constructed.Comparing the modeling method with the others,the modeling process was programmed;and form of the model is unified and simple.The model,method and theory can be used to analyze other similar systems such as heavy cargo airdrop system and capsule parachute recovery system.
基金Ministry of Science, Industry, and Technology which supported this project under the Industrial Thesis Support Program
文摘A dynamical moving pressure structural numerical calculation model using the internal ballistics calculation pressure-time results was constituted and the vicinity of the internal ballistics and quasiinternal ballistics structural model was checked. The Von Mises stresses obtained by the dynamical structural numerical model calculations and the Von Mises stresses calculated from the shot test strain measurements were compared. The difference for the worse case was 20% and for the best case was 0.1%.Furthermore, the model gave better agreement for the higher charge masses. The numerical structural quasi-internal ballistics computation model created was verified for the top charge mass which represents the highest stress condition and used in a gun barrel design.
