The use of a shaped liner driven by electromagnetic force is a new means of forming jets. To study the mechanism of jet formation driven by electromagnetic force, we considered the current skin effect and the characte...The use of a shaped liner driven by electromagnetic force is a new means of forming jets. To study the mechanism of jet formation driven by electromagnetic force, we considered the current skin effect and the characteristics of electromagnetic loading and established a coupling model of "ElectriceMagnetic eForce" and the theoretical model of jet formation under electromagnetic force. The jet formation and penetration of conical and trumpet liners have been calculated. Then, a numerical simulation of liner collapse under electromagnetic force, jet generation, and the stretching motion were performed using an ANSYS multiphysics processor. The calculated jet velocity, jet shape, and depth of penetration were consistent with the experimental results, with a relative error of less than 10%. In addition, we calculated the jet formation of different curvature trumpet liners driven by the same loading condition and obtained the influence rule of the curvature of the liner on jet formation. Results show that the theoretical model and the ANSYS multiphysics numerical method can effectively calculate the jet formation of liners driven by electromagnetic force, and in a certain range, the greater the curvature of the liner is, the greater the jet velocity is.展开更多
The bore-center annular shaped charge(BCASC)is a new type of shaped charge which can generate a larger-diameter hole in steel targets than classical shaped charges.In this paper,the influence of three liner materials,...The bore-center annular shaped charge(BCASC)is a new type of shaped charge which can generate a larger-diameter hole in steel targets than classical shaped charges.In this paper,the influence of three liner materials,i.e.molybdenum,nickel and copper,on BCASC formation and penetrating into steel targets was investigated by experiment and numerical simulation.The simulation results were well consistent with the experimental results.This study showed that,at 0.50D standoff distance,the axial velocity of the molybdenum projectile was lower than that of the nickel and copper projectiles.The nickel and copper projectiles had almost the same head velocity.The absolute values of the radial velocity of the molybdenum projectile head was lower than that of the nickel and copper projectiles.However,at 0.75D standoff distance,the absolute values of the radial velocity of the molybdenum projectile head became much greater than that of the nickel and copper projectile heads.The projectile formed by BCASC with the molybdenum liner had the highest penetration depth of 61.5 mm,which was 10.0%and 21.3%higher than that generated by the copper and nickel projectiles.展开更多
To ensure safe flight of multiple fixed-wing unmanned aerial vehicles(UAVs)formation,considering trajectory planning and formation control together,a leader trajectory planning method based on the sparse A*algorithm i...To ensure safe flight of multiple fixed-wing unmanned aerial vehicles(UAVs)formation,considering trajectory planning and formation control together,a leader trajectory planning method based on the sparse A*algorithm is introduced.Firstly,a formation controller based on prescribed performance theory is designed to control the transient and steady formation configuration,as well as the formation forming time,which not only can form the designated formation configuration but also can guarantee collision avoidance and terrain avoidance theoretically.Next,considering the constraints caused by formation controller on trajectory planning such as the safe distance,turn angle and step length,as well as the constraint of formation shape,a leader trajectory planning method based on sparse A^(*)algorithm is proposed.Simulation results show that the UAV formation can arrive at the destination safely with a short trajectory no matter keeping the formation or encountering formation transformation.展开更多
By using LS-DYNA simulation software,the influences of some structure parameters,such as top cone angle,wall thickness,liner height and height ratio of top cone,of double-angle liner on the jet formation were studied ...By using LS-DYNA simulation software,the influences of some structure parameters,such as top cone angle,wall thickness,liner height and height ratio of top cone,of double-angle liner on the jet formation were studied respectively.Their influences on jet tip velocity,tail velocity and penetration depth were revealed.The simulation results show that the formation is better if the top cone angle is selected as 28°,the wall is 2.6mm,the liner height is 140mm,and the height ratio of top cone is 60%.In large stand-off distance,the jet has a higher tip velocity,and the tip does not break.With the stand-off distance of 8 times of the charge diameter,the experiment penetrating steel target was carried out.The experiment and simulation results are in good agreement.展开更多
四川盆地震旦系灯影组是重要的油气勘探开发层系,复杂的成岩演化和多期流体活动导致多种类型的白云岩形成。揭示震旦系白云岩的形成时代和成因不仅可以为四川盆地震旦系下一步的油气勘探提供更加充实的科学依据,也可为理解全球大规模存...四川盆地震旦系灯影组是重要的油气勘探开发层系,复杂的成岩演化和多期流体活动导致多种类型的白云岩形成。揭示震旦系白云岩的形成时代和成因不仅可以为四川盆地震旦系下一步的油气勘探提供更加充实的科学依据,也可为理解全球大规模存在前寒武纪白云岩的原因提供有益启示。本文针对川中地区震旦系灯影组“葡萄花边”白云岩的形成时代和成因进行了综合研究。岩相学研究表明,“葡萄花边”白云岩充填于藻白云岩的孔隙内,向内对称生长,结晶程度明显好于藻白云岩。在岩相学的基础上,利用激光剥蚀-电感耦合等离子体质谱(LA-ICP-MS)微区原位U-Pb定年确定其形成时代,研究结果表明:川中地区震旦系灯影组“葡萄花边”白云岩形成时代为530±12Ma~502±12Ma,略新于灯影组地层年代。结合微量元素分析以及碳-氧-锶同位素数据,对川中地区震旦系灯影组“葡萄花边”白云岩进行成因分析。结果表明,其稀土元素总量(∑REE)相对较低(0.680×10^(-6)~8.963×10^(-6)),δ13 C VPDB(-0.1‰~1.7‰)略低于与同时期海水沉积白云岩的碳同位素值,δ18 O VPDB(-2.3‰~1.4‰)略高于与同时期海水达到氧同位素平衡的白云岩氧同位素值,87 Sr/86 Sr值(0.70876~0.70909)基本落入同时期海水范围。稀土元素配分总体为水平的模式,所有样品表现出Ce负异常。表明其形成环境既非海水沉积环境,也不完全是表生大气水岩溶条件。综合上述特征,推断川中地区震旦系灯影组“葡萄花边”白云岩是在震旦纪末-寒武纪早期海平面高频低幅度波动这一背景下,灯影组地层多次暴露与淹没,形成岩溶裂缝和孔洞的同时在溶蚀空间内结晶形成。残留孔洞为其后流体活动、油气充注提供了储集空间。本研究为认识川中地区震旦系灯影组“葡萄花边”白云岩成因、震旦纪末-寒武纪早期水化学条件、及超深层油气勘探开发提供了有益参考。展开更多
基金supported by the Natural Science Funds for Distinguished Young Scholar (Grant No. 11602110)Jiangsu Province Graduate Research and Practice Innovation Program (No.KY CX180471)。
文摘The use of a shaped liner driven by electromagnetic force is a new means of forming jets. To study the mechanism of jet formation driven by electromagnetic force, we considered the current skin effect and the characteristics of electromagnetic loading and established a coupling model of "ElectriceMagnetic eForce" and the theoretical model of jet formation under electromagnetic force. The jet formation and penetration of conical and trumpet liners have been calculated. Then, a numerical simulation of liner collapse under electromagnetic force, jet generation, and the stretching motion were performed using an ANSYS multiphysics processor. The calculated jet velocity, jet shape, and depth of penetration were consistent with the experimental results, with a relative error of less than 10%. In addition, we calculated the jet formation of different curvature trumpet liners driven by the same loading condition and obtained the influence rule of the curvature of the liner on jet formation. Results show that the theoretical model and the ANSYS multiphysics numerical method can effectively calculate the jet formation of liners driven by electromagnetic force, and in a certain range, the greater the curvature of the liner is, the greater the jet velocity is.
基金supported by the National Natural Science Foundation of China(No.11732003)Beijing Natural Science Foundation(No.8182050)+1 种基金Science Challenge Project(No.TZ2016001)National Key R&D Program of China(No.2017YFC0804700)
文摘The bore-center annular shaped charge(BCASC)is a new type of shaped charge which can generate a larger-diameter hole in steel targets than classical shaped charges.In this paper,the influence of three liner materials,i.e.molybdenum,nickel and copper,on BCASC formation and penetrating into steel targets was investigated by experiment and numerical simulation.The simulation results were well consistent with the experimental results.This study showed that,at 0.50D standoff distance,the axial velocity of the molybdenum projectile was lower than that of the nickel and copper projectiles.The nickel and copper projectiles had almost the same head velocity.The absolute values of the radial velocity of the molybdenum projectile head was lower than that of the nickel and copper projectiles.However,at 0.75D standoff distance,the absolute values of the radial velocity of the molybdenum projectile head became much greater than that of the nickel and copper projectile heads.The projectile formed by BCASC with the molybdenum liner had the highest penetration depth of 61.5 mm,which was 10.0%and 21.3%higher than that generated by the copper and nickel projectiles.
基金supported by the National Natural Science Foundation of China(11502019).
文摘To ensure safe flight of multiple fixed-wing unmanned aerial vehicles(UAVs)formation,considering trajectory planning and formation control together,a leader trajectory planning method based on the sparse A*algorithm is introduced.Firstly,a formation controller based on prescribed performance theory is designed to control the transient and steady formation configuration,as well as the formation forming time,which not only can form the designated formation configuration but also can guarantee collision avoidance and terrain avoidance theoretically.Next,considering the constraints caused by formation controller on trajectory planning such as the safe distance,turn angle and step length,as well as the constraint of formation shape,a leader trajectory planning method based on sparse A^(*)algorithm is proposed.Simulation results show that the UAV formation can arrive at the destination safely with a short trajectory no matter keeping the formation or encountering formation transformation.
文摘By using LS-DYNA simulation software,the influences of some structure parameters,such as top cone angle,wall thickness,liner height and height ratio of top cone,of double-angle liner on the jet formation were studied respectively.Their influences on jet tip velocity,tail velocity and penetration depth were revealed.The simulation results show that the formation is better if the top cone angle is selected as 28°,the wall is 2.6mm,the liner height is 140mm,and the height ratio of top cone is 60%.In large stand-off distance,the jet has a higher tip velocity,and the tip does not break.With the stand-off distance of 8 times of the charge diameter,the experiment penetrating steel target was carried out.The experiment and simulation results are in good agreement.
文摘四川盆地震旦系灯影组是重要的油气勘探开发层系,复杂的成岩演化和多期流体活动导致多种类型的白云岩形成。揭示震旦系白云岩的形成时代和成因不仅可以为四川盆地震旦系下一步的油气勘探提供更加充实的科学依据,也可为理解全球大规模存在前寒武纪白云岩的原因提供有益启示。本文针对川中地区震旦系灯影组“葡萄花边”白云岩的形成时代和成因进行了综合研究。岩相学研究表明,“葡萄花边”白云岩充填于藻白云岩的孔隙内,向内对称生长,结晶程度明显好于藻白云岩。在岩相学的基础上,利用激光剥蚀-电感耦合等离子体质谱(LA-ICP-MS)微区原位U-Pb定年确定其形成时代,研究结果表明:川中地区震旦系灯影组“葡萄花边”白云岩形成时代为530±12Ma~502±12Ma,略新于灯影组地层年代。结合微量元素分析以及碳-氧-锶同位素数据,对川中地区震旦系灯影组“葡萄花边”白云岩进行成因分析。结果表明,其稀土元素总量(∑REE)相对较低(0.680×10^(-6)~8.963×10^(-6)),δ13 C VPDB(-0.1‰~1.7‰)略低于与同时期海水沉积白云岩的碳同位素值,δ18 O VPDB(-2.3‰~1.4‰)略高于与同时期海水达到氧同位素平衡的白云岩氧同位素值,87 Sr/86 Sr值(0.70876~0.70909)基本落入同时期海水范围。稀土元素配分总体为水平的模式,所有样品表现出Ce负异常。表明其形成环境既非海水沉积环境,也不完全是表生大气水岩溶条件。综合上述特征,推断川中地区震旦系灯影组“葡萄花边”白云岩是在震旦纪末-寒武纪早期海平面高频低幅度波动这一背景下,灯影组地层多次暴露与淹没,形成岩溶裂缝和孔洞的同时在溶蚀空间内结晶形成。残留孔洞为其后流体活动、油气充注提供了储集空间。本研究为认识川中地区震旦系灯影组“葡萄花边”白云岩成因、震旦纪末-寒武纪早期水化学条件、及超深层油气勘探开发提供了有益参考。
