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
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
The severe erosion and inadequate mechanical strength are prominent challenges for high-energy gun propellants.To address it,novel PTW@PDA composites was prepared by polydopamine(PDA)-modifying onto potassium titanate...The severe erosion and inadequate mechanical strength are prominent challenges for high-energy gun propellants.To address it,novel PTW@PDA composites was prepared by polydopamine(PDA)-modifying onto potassium titanate whisker(PTW,K_(2)Ti_(6)O_(13)),and after was incorporated into gun propellant as erosion-reducing and mechanical-reinforcing fillers.The interfacial characterizations results indicated that as-prepared PTW@PDA composites exhibits an enhanced surface compatible with propellant matrix,thereby facilitating their dispersion into propellants more effectively than raw PTW materials.Compared to original propellants,PTW@PDA-modified propellants exhibited significant less erosion,with a Ti-Kbased protective coating being detected on the eroded steel.And 0.5 wt%and 1.0 wt%addition of PTW@PDA significantly improved impact,compressive and tensile strength of propellants.Despite the inevitably reduction in relative force,PTW@PDA slightly increase propellant burning rate while exerting little adverse impact on propellant dynamic activity.This strategy can provide a promising alternative to develop high-energy gun propellant with less erosion and more mechanical strength.展开更多
The feasibility of providing the tank a limited anti helicopter ability with gun launched missile is studied. A type of simulation model of gun launched missile against attack helicopters is established. The simula...The feasibility of providing the tank a limited anti helicopter ability with gun launched missile is studied. A type of simulation model of gun launched missile against attack helicopters is established. The simulation and the parameter optimization of missile control system under various circumstances are done. The gun launched missile can directly hit the helicopters in the typical tracks, all the missdistances are less than 1?m and the maximum overload is less than available overload. Gun launched missile is a feasible choice for tanks against attack helicopters.展开更多
This paper presents the results of a comparative investigation into the effects of the ignition method on the ballistic properties of a single-base gun propellant,as determined via closed vessel tests.Conventional gun...This paper presents the results of a comparative investigation into the effects of the ignition method on the ballistic properties of a single-base gun propellant,as determined via closed vessel tests.Conventional gunpowder ignition and plasma jet ignition methods were used,and differences in the ignition time were analysed.The influence of the ignition method on the dynamic vivacity is discussed.It is shown that this influence is significant in the first phase of the combustion process,and with respect to the low values of the loading density.In the second phase of the combustion process,and for large values of the loading density,the dynamic vivacity plots for the two ignition methods converge.Regarding the burning law,close values of the exponent were obtained for the two ignition methods.The dynamic vivacity plots determined for plasma ignition reveal stronger dependence on the loading density than those determined for gunpowder ignition.The conclusion is that plasma ignition is not a solution to the problems inherent to the process of determining the ballistic properties of propellants,which results in deviation of the burning process from the geometric burning law.展开更多
Distributed X-ray sources comprise a single vacuum chamber containing multiple X-ray sources that are triggered and emit X-rays at a specific time and location. This process facilitates an application for innovative s...Distributed X-ray sources comprise a single vacuum chamber containing multiple X-ray sources that are triggered and emit X-rays at a specific time and location. This process facilitates an application for innovative system concepts in X-ray and computer tomography. This paper proposes a novel electron beam focusing, shaping,and deflection electron gun for distributed X-ray sources.The electron gun uses a dispenser cathode as an electron emitter, a mesh grid to control emission current, and two electrostatic lenses for beam shaping, focusing, and deflection. Novel focusing and deflecting electrodes were designed to increase the number of focal spots in the distributed source. Two identical half-rectangle opening electrodes are controlled by adjusting the potential of the two electrodes to control the electron beam trajectory, and then, multifocal spots are obtained on the anode target. The electron gun can increase the spatial density of the distributed X-ray sources, thereby improving the image quality. The beam experimental results show that the focal spot sizes of the deflected(deflected amplitude 10.5 mm)and non-deflected electron beams at full width at half maximum are 0.80 mm 90.50 mm and 0.55 mm 90.40 mm, respectively(anode voltage 160 kV; beam current 30 mA). The imaging experimental results demonstrate the excellent spatial resolution and time resolution of an imaging system built with the sources, which has an excellent imaging effect on a field-programmable gate array chip and a rotating metal disk.展开更多
The simulation of compression and fracture of charge bed in chamber is one of the key problems in the study of launch safety of gun propellant charge. A new kind of experimental device that can be used for simulation ...The simulation of compression and fracture of charge bed in chamber is one of the key problems in the study of launch safety of gun propellant charge. A new kind of experimental device that can be used for simulation is given. Its structure and operational principle are introduced. Using a semi-closed vessel as a source of compression force, the device can simulate any kind of dynamic environment in a gun propellant charge. Using the low temperature inert gas （N2） as the compression medium, the device can not only ensure that the simulation is real, but also protect the fragmentized propellant from combustion after experiment. Using the device, many simulation experiments have been accomplished, and dynamic environment of propellant fracture is acquired. With the experiments, fragmentized propellant for the compression and fracture of charge bed is obtained. Results of experiments show that the new device can be used to study the principle of the compression and fracture of charge bed.展开更多
Gradiently denitrated gun propellant(GDGP)prepared by a“gradient denitration”strategy is obviously superior in progressive burning performance to the traditional deterred gun propellant.Currently,the preparation of ...Gradiently denitrated gun propellant(GDGP)prepared by a“gradient denitration”strategy is obviously superior in progressive burning performance to the traditional deterred gun propellant.Currently,the preparation of GDGP employed a tedious two-step method involving organic solvents,which hinders the large-scale preparation of GDGP.In this paper,GDGP was successfully prepared via a novelty and environmentally friendly one-step method.The obtained samples were characterized by FT-IR,Raman,SEM and XPS.The results showed that the content of nitrate groups gradiently increased from the surface to the core in the surface layer of GDGP and the surface layer of GDGP exhibited a higher compaction than that of raw gun propellant,with a well-preserved nitrocellulose structure.The denitration process enabled the propellant surface with regressive energy density and good progressive burning performance,as confirmed by oxygen bomb and closed bomb test.At the same time,the effects of different solvents on the component loss of propellant were compared.The result showed that water caused the least component loss.Finally,the stability of GDGP was confirmed by methyl-violet test.This work not only provided environmentally friendly,simple and economic preparation of GDGP,but also confirmed the stability of GDGP prepared by this method.展开更多
Achieving high hitting accuracy for a main battle tank is challenging while the tank is on the move. This can be reached by proper design of a weapon control and gun system. In order to design an effective gun system ...Achieving high hitting accuracy for a main battle tank is challenging while the tank is on the move. This can be reached by proper design of a weapon control and gun system. In order to design an effective gun system while the tank is moving, better understanding of the dynamic behavior of the gun system is required. In this study, the dynamic behaviour of a gun system is discussed in this respect. Both experimental and numerical applications for the determination of the dynamic behaviour of a tank gun system are investigated. Methods such as the use of muzzle reference system(MRS) and vibration absorbers, and active vibration control technology for the control and the reduction of the muzzle tip deflections are also reviewed. For the existing gun systems without making substantial modifications,MRS could be useful in controlling the deflections of gun barrels with estimation/prediction algorithms.The vibration levels could be cut into half by the use of optimised vibration absorbers for an existing gun.A new gun system with a longer barrel can be as accurate as the one with a short barrel with the appropriate structural modifications.展开更多
In this study,a theoretical nonlinear dynamic model was established for a saddle ring based on a dynamic force analysis of the launching process and the structure according to contact-impact theory.The ADAMS software ...In this study,a theoretical nonlinear dynamic model was established for a saddle ring based on a dynamic force analysis of the launching process and the structure according to contact-impact theory.The ADAMS software was used to build a parameterized dynamic model of the saddle ring.A parameter identification method for the ring was proposed based on the particle swarm optimization algorithm.A loading test was designed and performed several times at different elevation angles.The response histories of the saddle ring with different loads were then obtained.The parameters of the saddle ring dynamic model were identified from statistics generated at a 500 elevation angle to verify the feasibility and accuracy of the proposed method.The actual loading history of the ring at a 70°elevation angle was taken as the model input.The response histories of the ring under these working conditions were obtained through a simulation.The simulation results agreed with the actual response.Thus,the effectiveness and applicability of the proposed dynamic model were verified,and it provides an effective method for modeling saddle rings.展开更多
In this research,a detailed multi-physics study has been carried out by numerically simulating a solid fractured gun barrel for 20 thermo-mechanical cycles.The numerical model is based on thermal effects,mechanical st...In this research,a detailed multi-physics study has been carried out by numerically simulating a solid fractured gun barrel for 20 thermo-mechanical cycles.The numerical model is based on thermal effects,mechanical stress fields and fatigue crack mechanics.Elastic-plastic material data of modified AISI 4340 at temperatures ranging from 25 to 1200℃and at strain rates of 4,16,32 and 48 s^(-1) was acquired from high-temperature compression tests.This was used as material property data in the simulation model.The boundary conditions applied are kept similar to the working gun barrel during continuous firing.A methodology has been provided to define thermo-mechanically active surface-to-surface type interface between the crack faces for a better approximation of stresses at the crack tip.Comparison of results from non-autofrettaged and autofrettaged simulation models provide useful information about the evolution of strains and stresses in the barrel at different points under combined thermo-mechanical loading cycles in both cases.The effect of thermal fatigue under already induced compressive yield due to autofrettage and the progressive degradation of the accumulated stresses due to thermo-mechanical cyclic loads on the internal surface of the gun barrel(mimicking the continuous firing scenario)has been analyzed.Comparison between energy release rate at tips of varying crack lengths due to cyclic thermo-mechanical loading in the non-autofrettaged and autofrettaged gun has been carried out.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
Very high frequency(VHF) photocathode guns have excellent performance and are being increasingly selected as electron sources for high-repetition-rate X-ray free-electron lasers. As a highly loaded quality factor cavi...Very high frequency(VHF) photocathode guns have excellent performance and are being increasingly selected as electron sources for high-repetition-rate X-ray free-electron lasers. As a highly loaded quality factor cavity, the VHF gun requires high stability in the amplitude and phase of the cavity field. However, the gun is microwave powered by two solid-state power sources through two separate power couplers. The input difference between the two power couplers will influence the stability of the cavity field. To systematically study this influence and obtain measurement formulae, a multi-port VHF gun LCR circuit model is built and analyzed. During the warm-up condition, the cavity structure will be deformed due to the large-scale change in the cavity temperature. Then, the deformation will result in cavity resonant frequency changes. To prevent the mechanic tuner from suffering damages due to the frequent and long-distance movement for correcting the cavity resonant frequency, a self-excited loop(SEL) control system is considered for changing the loop phase and make the loop frequency follow the resonant frequency. In this study, a steady-state model of the VHF gun cavity is built for obtaining the optimal input coupler coefficient and the stability requirement of the forward voltage. Then, the generator-driven resonator and SEL control system, which combine with the VHF multiport modeling, are modeled and simulated. The simulated results show that the SEL system can perfectly operate in the process of condition and warm-up.展开更多
A hypersonic aerodynamics analysis of an electromagnetic gun(EM gun) launched projectile configuration is undertaken in order to ameliorate the basic aerodynamic characteristics in comparison with the regular projecti...A hypersonic aerodynamics analysis of an electromagnetic gun(EM gun) launched projectile configuration is undertaken in order to ameliorate the basic aerodynamic characteristics in comparison with the regular projectile layout.Static margin and pendulum motion analysis models have been applied to evaluate the flight stability of a new airframe configuration.With a steady state computational fluid dynamics(CFD) simulation,the basic density,pressure and velocity contours of the EM gun projectile flow field at Mach number 5.0,6.0 and 7.0(angle of attack=0°) have been analyzed.Furthermore,the static margin values are enhanced dramatically for the EM gun projectile with configuration optimization.Drag,lift and pitch property variations are all illustrated with the changes of Mach number and angle of attack.A particle ballistic calculation was completed for the pendulum analysis.The results show that the configuration optimized projectile,launched from the EM gun at Mach number 5.0 to 7.0,acts in a much more stable way than the projectiles with regular aerodynamic layout.展开更多
Very-high-frequency(VHF)gun photoinjectors,capable of producing high-brightness and high-repetitionrate electron bunches,are some of the best electron sources for driving MHz-class repetition-rate free-electron lasers...Very-high-frequency(VHF)gun photoinjectors,capable of producing high-brightness and high-repetitionrate electron bunches,are some of the best electron sources for driving MHz-class repetition-rate free-electron lasers.In this study,the beam dynamics optimization of a VHF gun photoinjector for Shanghai HIgh Repetition Rate X-ray Free Electron Laser and Extreme Light Facility(SHINE)is systematically demonstrated using a genetic algorithm.Through the inclusion of the solenoid geometry as an optimization variable into the genetic algorithm,the optimum projected normalized emittance for 100 pC bunches with bunch length of 1 mm rms is reduced to 0.1 mm mrad for 100%of the particles and 0.075 mm mrad for 95%of the particles,proving that sub-100 nm emittance can be achieved in the SHINE injector using a single-cell Tsinghua University(THU)VHF gun.This emittance fulfills the requirements not only of SHINE and Linac Coherent Light Source(LCLS)-II but also of LCLS-II-High Energy(LCLS-II-HE).We demonstrate that the optimal emittance in the VHF gun injector is reduced via the optimization of the solenoid geometry,thereby reducing solenoid spherical aberration.Through the inclusion of high-order(H.O.)energy spread among the optimization objectives,the H.O.energy spread can be reduced by a factor of nearly six using a high-harmonic cavity despite a 38%emittance growth.Finally,the beam dynamics in the SHINE main accelerator show that reducing the H.O.energy spread in the injector is of great significance to improving compression efficiency and reducing bunch current spike.展开更多
As one of the most important key technologies for future advanced light source based on the energy recovery linac, a photocathode dc electron gun is supported by Institute of High Energy Physics （IHEP） to address th...As one of the most important key technologies for future advanced light source based on the energy recovery linac, a photocathode dc electron gun is supported by Institute of High Energy Physics （IHEP） to address the technical challenges of producing very low ernittance beams at high average current. Construction of the dc gun is completed and a preliminary high voltage conditioning is carried out up to 440 k V. The design, construction and preliminary HV conditioning results for the dc gun are described.展开更多
One-dimensional simulations with a detailed hydrogen-oxygen reaction mechanism have been performed to investigate detonation phenomenon in a combustion light gas gun(CLGG).Convection fluxes of the Navier-Stokes equati...One-dimensional simulations with a detailed hydrogen-oxygen reaction mechanism have been performed to investigate detonation phenomenon in a combustion light gas gun(CLGG).Convection fluxes of the Navier-Stokes equations are solved using the WAF(weighted average flux)scheme HLLC Riemann solver.A high resolution fifth-order WENO scheme for the variable extrapolation at the volume interface and a fourth-order Runge-Kutta scheme for the time advancement are used.Validation tests of the stoichiometric hydrogen-oxygen deflagration to detonation transition process shows good agreement between the computed results and the analytical and documented solutions,demonstrating the reliability on the detonation simulation of the current scheme.Simulation results of the interior ballistic process of the CLGG show that the flame propagation experiences three distinct stages.The blast detonation wave causes a high-pressure shock and hazardous oscillations in the chamber and makes the projectile accelerate with fluctuations,but has only a small improvement to the muzzle velocity.展开更多
Shell-feeding velocity is an important factor affecting naval gun shooting capacity. An agile shell-feeding system was designed to ensure quick implementation of the shell-feeding task. Based on composition of the agi...Shell-feeding velocity is an important factor affecting naval gun shooting capacity. An agile shell-feeding system was designed to ensure quick implementation of the shell-feeding task. Based on composition of the agile shell-feeding system, hoist technology was studied. Working principles were discussed and the hydraulic pressure system of the hoist was constructed. The hydraulic pressure cylinder and the accumulator were analyzed and calculated. Finally, PRO/E and ADAMS were used to simulate the hoist and its hydraulic system. It was found that this type of virtual prototype provides a good method to actualize a physical prototype.展开更多
Finite element method is used to study the formations of the penetration jet,the bulge,and the burr in the designed reusable perforating gun.The attached layer of the soft metal on the perforator is studied for the co...Finite element method is used to study the formations of the penetration jet,the bulge,and the burr in the designed reusable perforating gun.The attached layer of the soft metal on the perforator is studied for the controlling of the bulge height on the casing of the reusable perforating gun.Results indicate that the shaped charge jet is initially formed in the center of the shaped charge liner and then the material of the liner is driven to the centerline of the liner by the detonation wave.The attachment of the soft metal layer to the cartridge of the perforator can be beneficial to control the bulge height.The design on the blind holes on the casing can affect the burr height formed by the collision between the jet and the casing.With the increase in the liner angle,the penetration width on the cement wall of the wellbore is increased.展开更多
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.
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.
基金the support of the instrument and equipment fund of the Key Laboratory of Special Energy,Ministry of Education,Nanjing University of Science and Technology,China.
文摘The severe erosion and inadequate mechanical strength are prominent challenges for high-energy gun propellants.To address it,novel PTW@PDA composites was prepared by polydopamine(PDA)-modifying onto potassium titanate whisker(PTW,K_(2)Ti_(6)O_(13)),and after was incorporated into gun propellant as erosion-reducing and mechanical-reinforcing fillers.The interfacial characterizations results indicated that as-prepared PTW@PDA composites exhibits an enhanced surface compatible with propellant matrix,thereby facilitating their dispersion into propellants more effectively than raw PTW materials.Compared to original propellants,PTW@PDA-modified propellants exhibited significant less erosion,with a Ti-Kbased protective coating being detected on the eroded steel.And 0.5 wt%and 1.0 wt%addition of PTW@PDA significantly improved impact,compressive and tensile strength of propellants.Despite the inevitably reduction in relative force,PTW@PDA slightly increase propellant burning rate while exerting little adverse impact on propellant dynamic activity.This strategy can provide a promising alternative to develop high-energy gun propellant with less erosion and more mechanical strength.
文摘The feasibility of providing the tank a limited anti helicopter ability with gun launched missile is studied. A type of simulation model of gun launched missile against attack helicopters is established. The simulation and the parameter optimization of missile control system under various circumstances are done. The gun launched missile can directly hit the helicopters in the typical tracks, all the missdistances are less than 1?m and the maximum overload is less than available overload. Gun launched missile is a feasible choice for tanks against attack helicopters.
基金supported by the National Research Centre,Poland [grant number DOB-BIO8/05/01/2016]the Ministry of Defence of Poland [grant number GBMON/13-988/2018/WAT]
文摘This paper presents the results of a comparative investigation into the effects of the ignition method on the ballistic properties of a single-base gun propellant,as determined via closed vessel tests.Conventional gunpowder ignition and plasma jet ignition methods were used,and differences in the ignition time were analysed.The influence of the ignition method on the dynamic vivacity is discussed.It is shown that this influence is significant in the first phase of the combustion process,and with respect to the low values of the loading density.In the second phase of the combustion process,and for large values of the loading density,the dynamic vivacity plots for the two ignition methods converge.Regarding the burning law,close values of the exponent were obtained for the two ignition methods.The dynamic vivacity plots determined for plasma ignition reveal stronger dependence on the loading density than those determined for gunpowder ignition.The conclusion is that plasma ignition is not a solution to the problems inherent to the process of determining the ballistic properties of propellants,which results in deviation of the burning process from the geometric burning law.
文摘Distributed X-ray sources comprise a single vacuum chamber containing multiple X-ray sources that are triggered and emit X-rays at a specific time and location. This process facilitates an application for innovative system concepts in X-ray and computer tomography. This paper proposes a novel electron beam focusing, shaping,and deflection electron gun for distributed X-ray sources.The electron gun uses a dispenser cathode as an electron emitter, a mesh grid to control emission current, and two electrostatic lenses for beam shaping, focusing, and deflection. Novel focusing and deflecting electrodes were designed to increase the number of focal spots in the distributed source. Two identical half-rectangle opening electrodes are controlled by adjusting the potential of the two electrodes to control the electron beam trajectory, and then, multifocal spots are obtained on the anode target. The electron gun can increase the spatial density of the distributed X-ray sources, thereby improving the image quality. The beam experimental results show that the focal spot sizes of the deflected(deflected amplitude 10.5 mm)and non-deflected electron beams at full width at half maximum are 0.80 mm 90.50 mm and 0.55 mm 90.40 mm, respectively(anode voltage 160 kV; beam current 30 mA). The imaging experimental results demonstrate the excellent spatial resolution and time resolution of an imaging system built with the sources, which has an excellent imaging effect on a field-programmable gate array chip and a rotating metal disk.
文摘The simulation of compression and fracture of charge bed in chamber is one of the key problems in the study of launch safety of gun propellant charge. A new kind of experimental device that can be used for simulation is given. Its structure and operational principle are introduced. Using a semi-closed vessel as a source of compression force, the device can simulate any kind of dynamic environment in a gun propellant charge. Using the low temperature inert gas （N2） as the compression medium, the device can not only ensure that the simulation is real, but also protect the fragmentized propellant from combustion after experiment. Using the device, many simulation experiments have been accomplished, and dynamic environment of propellant fracture is acquired. With the experiments, fragmentized propellant for the compression and fracture of charge bed is obtained. Results of experiments show that the new device can be used to study the principle of the compression and fracture of charge bed.
文摘Gradiently denitrated gun propellant(GDGP)prepared by a“gradient denitration”strategy is obviously superior in progressive burning performance to the traditional deterred gun propellant.Currently,the preparation of GDGP employed a tedious two-step method involving organic solvents,which hinders the large-scale preparation of GDGP.In this paper,GDGP was successfully prepared via a novelty and environmentally friendly one-step method.The obtained samples were characterized by FT-IR,Raman,SEM and XPS.The results showed that the content of nitrate groups gradiently increased from the surface to the core in the surface layer of GDGP and the surface layer of GDGP exhibited a higher compaction than that of raw gun propellant,with a well-preserved nitrocellulose structure.The denitration process enabled the propellant surface with regressive energy density and good progressive burning performance,as confirmed by oxygen bomb and closed bomb test.At the same time,the effects of different solvents on the component loss of propellant were compared.The result showed that water caused the least component loss.Finally,the stability of GDGP was confirmed by methyl-violet test.This work not only provided environmentally friendly,simple and economic preparation of GDGP,but also confirmed the stability of GDGP prepared by this method.
文摘Achieving high hitting accuracy for a main battle tank is challenging while the tank is on the move. This can be reached by proper design of a weapon control and gun system. In order to design an effective gun system while the tank is moving, better understanding of the dynamic behavior of the gun system is required. In this study, the dynamic behaviour of a gun system is discussed in this respect. Both experimental and numerical applications for the determination of the dynamic behaviour of a tank gun system are investigated. Methods such as the use of muzzle reference system(MRS) and vibration absorbers, and active vibration control technology for the control and the reduction of the muzzle tip deflections are also reviewed. For the existing gun systems without making substantial modifications,MRS could be useful in controlling the deflections of gun barrels with estimation/prediction algorithms.The vibration levels could be cut into half by the use of optimised vibration absorbers for an existing gun.A new gun system with a longer barrel can be as accurate as the one with a short barrel with the appropriate structural modifications.
基金supported by National Natural Science Foundation of China(11472137)the Natural Science Foundation of Jiangsu Province,China(BK20140773)。
文摘In this study,a theoretical nonlinear dynamic model was established for a saddle ring based on a dynamic force analysis of the launching process and the structure according to contact-impact theory.The ADAMS software was used to build a parameterized dynamic model of the saddle ring.A parameter identification method for the ring was proposed based on the particle swarm optimization algorithm.A loading test was designed and performed several times at different elevation angles.The response histories of the saddle ring with different loads were then obtained.The parameters of the saddle ring dynamic model were identified from statistics generated at a 500 elevation angle to verify the feasibility and accuracy of the proposed method.The actual loading history of the ring at a 70°elevation angle was taken as the model input.The response histories of the ring under these working conditions were obtained through a simulation.The simulation results agreed with the actual response.Thus,the effectiveness and applicability of the proposed dynamic model were verified,and it provides an effective method for modeling saddle rings.
基金the DAAD Faculty Development for Ph.D.Candidates(Balochistan)2016(57245990)-HRDI-UESTP’s/UET’s funding scheme in cooperation with the Higher Education Commission of Pakistan(HEC)for sponsoring the stay at IMF TU Freiberg,Germany.
文摘In this research,a detailed multi-physics study has been carried out by numerically simulating a solid fractured gun barrel for 20 thermo-mechanical cycles.The numerical model is based on thermal effects,mechanical stress fields and fatigue crack mechanics.Elastic-plastic material data of modified AISI 4340 at temperatures ranging from 25 to 1200℃and at strain rates of 4,16,32 and 48 s^(-1) was acquired from high-temperature compression tests.This was used as material property data in the simulation model.The boundary conditions applied are kept similar to the working gun barrel during continuous firing.A methodology has been provided to define thermo-mechanically active surface-to-surface type interface between the crack faces for a better approximation of stresses at the crack tip.Comparison of results from non-autofrettaged and autofrettaged simulation models provide useful information about the evolution of strains and stresses in the barrel at different points under combined thermo-mechanical loading cycles in both cases.The effect of thermal fatigue under already induced compressive yield due to autofrettage and the progressive degradation of the accumulated stresses due to thermo-mechanical cyclic loads on the internal surface of the gun barrel(mimicking the continuous firing scenario)has been analyzed.Comparison between energy release rate at tips of varying crack lengths due to cyclic thermo-mechanical loading in the non-autofrettaged and autofrettaged gun has been carried out.
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Very high frequency(VHF) photocathode guns have excellent performance and are being increasingly selected as electron sources for high-repetition-rate X-ray free-electron lasers. As a highly loaded quality factor cavity, the VHF gun requires high stability in the amplitude and phase of the cavity field. However, the gun is microwave powered by two solid-state power sources through two separate power couplers. The input difference between the two power couplers will influence the stability of the cavity field. To systematically study this influence and obtain measurement formulae, a multi-port VHF gun LCR circuit model is built and analyzed. During the warm-up condition, the cavity structure will be deformed due to the large-scale change in the cavity temperature. Then, the deformation will result in cavity resonant frequency changes. To prevent the mechanic tuner from suffering damages due to the frequent and long-distance movement for correcting the cavity resonant frequency, a self-excited loop(SEL) control system is considered for changing the loop phase and make the loop frequency follow the resonant frequency. In this study, a steady-state model of the VHF gun cavity is built for obtaining the optimal input coupler coefficient and the stability requirement of the forward voltage. Then, the generator-driven resonator and SEL control system, which combine with the VHF multiport modeling, are modeled and simulated. The simulated results show that the SEL system can perfectly operate in the process of condition and warm-up.
基金supported by Youth Science and Technology Research FundShanxi Province Applied Basic Research Projectgrant number 201801D221039+2 种基金Science Foundation of North University of China grant number XJJ201813Scientific and Technologial Innovation Programs of Higher Education Institutions in Shanxi grant number 2019L0570Aeronautical Science Foundation of China grant number 2019020U0002。
文摘A hypersonic aerodynamics analysis of an electromagnetic gun(EM gun) launched projectile configuration is undertaken in order to ameliorate the basic aerodynamic characteristics in comparison with the regular projectile layout.Static margin and pendulum motion analysis models have been applied to evaluate the flight stability of a new airframe configuration.With a steady state computational fluid dynamics(CFD) simulation,the basic density,pressure and velocity contours of the EM gun projectile flow field at Mach number 5.0,6.0 and 7.0(angle of attack=0°) have been analyzed.Furthermore,the static margin values are enhanced dramatically for the EM gun projectile with configuration optimization.Drag,lift and pitch property variations are all illustrated with the changes of Mach number and angle of attack.A particle ballistic calculation was completed for the pendulum analysis.The results show that the configuration optimized projectile,launched from the EM gun at Mach number 5.0 to 7.0,acts in a much more stable way than the projectiles with regular aerodynamic layout.
文摘Very-high-frequency(VHF)gun photoinjectors,capable of producing high-brightness and high-repetitionrate electron bunches,are some of the best electron sources for driving MHz-class repetition-rate free-electron lasers.In this study,the beam dynamics optimization of a VHF gun photoinjector for Shanghai HIgh Repetition Rate X-ray Free Electron Laser and Extreme Light Facility(SHINE)is systematically demonstrated using a genetic algorithm.Through the inclusion of the solenoid geometry as an optimization variable into the genetic algorithm,the optimum projected normalized emittance for 100 pC bunches with bunch length of 1 mm rms is reduced to 0.1 mm mrad for 100%of the particles and 0.075 mm mrad for 95%of the particles,proving that sub-100 nm emittance can be achieved in the SHINE injector using a single-cell Tsinghua University(THU)VHF gun.This emittance fulfills the requirements not only of SHINE and Linac Coherent Light Source(LCLS)-II but also of LCLS-II-High Energy(LCLS-II-HE).We demonstrate that the optimal emittance in the VHF gun injector is reduced via the optimization of the solenoid geometry,thereby reducing solenoid spherical aberration.Through the inclusion of high-order(H.O.)energy spread among the optimization objectives,the H.O.energy spread can be reduced by a factor of nearly six using a high-harmonic cavity despite a 38%emittance growth.Finally,the beam dynamics in the SHINE main accelerator show that reducing the H.O.energy spread in the injector is of great significance to improving compression efficiency and reducing bunch current spike.
基金Supported by the Innovation and Technology Fund of Institute of High Energy Physics
文摘As one of the most important key technologies for future advanced light source based on the energy recovery linac, a photocathode dc electron gun is supported by Institute of High Energy Physics （IHEP） to address the technical challenges of producing very low ernittance beams at high average current. Construction of the dc gun is completed and a preliminary high voltage conditioning is carried out up to 440 k V. The design, construction and preliminary HV conditioning results for the dc gun are described.
基金supported by the Foundation of National Key Laboratory of Shock Wave and Detonation Physics(Grant No.6142A0302020517)。
文摘One-dimensional simulations with a detailed hydrogen-oxygen reaction mechanism have been performed to investigate detonation phenomenon in a combustion light gas gun(CLGG).Convection fluxes of the Navier-Stokes equations are solved using the WAF(weighted average flux)scheme HLLC Riemann solver.A high resolution fifth-order WENO scheme for the variable extrapolation at the volume interface and a fourth-order Runge-Kutta scheme for the time advancement are used.Validation tests of the stoichiometric hydrogen-oxygen deflagration to detonation transition process shows good agreement between the computed results and the analytical and documented solutions,demonstrating the reliability on the detonation simulation of the current scheme.Simulation results of the interior ballistic process of the CLGG show that the flame propagation experiences three distinct stages.The blast detonation wave causes a high-pressure shock and hazardous oscillations in the chamber and makes the projectile accelerate with fluctuations,but has only a small improvement to the muzzle velocity.
文摘Shell-feeding velocity is an important factor affecting naval gun shooting capacity. An agile shell-feeding system was designed to ensure quick implementation of the shell-feeding task. Based on composition of the agile shell-feeding system, hoist technology was studied. Working principles were discussed and the hydraulic pressure system of the hoist was constructed. The hydraulic pressure cylinder and the accumulator were analyzed and calculated. Finally, PRO/E and ADAMS were used to simulate the hoist and its hydraulic system. It was found that this type of virtual prototype provides a good method to actualize a physical prototype.
基金financially supported by the National Natural Science Foundation of China(11572074)Liaoning Provincial Natural Science Foundation(2019-KF-05-07)。
文摘Finite element method is used to study the formations of the penetration jet,the bulge,and the burr in the designed reusable perforating gun.The attached layer of the soft metal on the perforator is studied for the controlling of the bulge height on the casing of the reusable perforating gun.Results indicate that the shaped charge jet is initially formed in the center of the shaped charge liner and then the material of the liner is driven to the centerline of the liner by the detonation wave.The attachment of the soft metal layer to the cartridge of the perforator can be beneficial to control the bulge height.The design on the blind holes on the casing can affect the burr height formed by the collision between the jet and the casing.With the increase in the liner angle,the penetration width on the cement wall of the wellbore is increased.
