The optimal guidance problem for an interceptor against a ballistic missile with active defense is investigated in this paper.A class of optimal guidance schemes are proposed based on linear quadratic differential gam...The optimal guidance problem for an interceptor against a ballistic missile with active defense is investigated in this paper.A class of optimal guidance schemes are proposed based on linear quadratic differential game method and numerical solution of Riccati differential equation.By choosing proper parameters, the proposed guidance schemes are able to drive the interceptor to the target and away from the defender simultaneously.Additionally, fuel cost, control saturation,chattering phenomenon and parameters selection were taken into account.Satisfaction of the proposed guidance schemes of the saddle point condition is proven theoretically.Finally, nonlinear numerical examples are included to demonstrate the effectiveness and performance of the developed guidance approaches.Comparison of control performance between different guidance schemes are presented and analysis.展开更多
Ballistic impact test of different-scale casings is an efficient way to demonstrate the casing containment capability at the preliminary design stage of the engine. For the sake of studying the titanium alloy TC4 casi...Ballistic impact test of different-scale casings is an efficient way to demonstrate the casing containment capability at the preliminary design stage of the engine. For the sake of studying the titanium alloy TC4 casing perfonnance, the ballistic tests of flat and curved simulation casing are implemented by using two flat blades of different sizes as the projectile. The impact mechanism and failure of the target are discussed. Impact of the projectile is a highly nonlinear transient process with the large deformation of the target. On the impact, failures of the flat casing and the subscale casing are similar, concluding two parts, the global dish- ing and localized ductile tearing. The main localized failure mode combines plugging （shear） and petaling （shear） if the projectile perforates or penetrates, while crater （shear） if the projectile rebounds. The ballistic limit equation is verified by the test data and the results show that this empirical equation could be a practical way to estimate the critical velocity.展开更多
The wideband electromagnetic characteristics of missile targets in midcourse are the foundation of midcourse attack-defense confrontation. This paper proposes a novel electromagnetic scattering modeling method for mid...The wideband electromagnetic characteristics of missile targets in midcourse are the foundation of midcourse attack-defense confrontation. This paper proposes a novel electromagnetic scattering modeling method for midcourse targets based on a pre- cise scattering center model, in which the nonideal scattering phenomenon, shielding effect and micro-motion are taken into consideration for the first time. Firstly, a precise scattering center model incorporating both the sliding scattering and artist- tropic scattering is established. Then the change rule of the target attitude is generalized, and a checking method of the scatter- ing center shielding effect is proposed for rotationally symmetric targets. Afterwards, a novel dynamic electromagnetic scat- tering model is presented, where the scattering center model updates along with the variation of the target attitude and can characterize the change of the electromagnetic characteristics of midcourse targets exactly. Finally, in light of the established model, the dynamic electromagnetic characteristics within different attitude angle bounds are analyzed by stages, and some useful conclusions are obtained. Experiment results from the measured data in anechoic chamber verify the validity of the proposed modeling method and relevant analysis.展开更多
A conditional boost-phase trajectory estimation method based on ballistic missile （BM） information database and classification is developed to estimate and predict boos-phase BM trajectory. The main uncertain factor...A conditional boost-phase trajectory estimation method based on ballistic missile （BM） information database and classification is developed to estimate and predict boos-phase BM trajectory. The main uncertain factors to describe BM dynamics equation are reduced to the control law of trajectory pitch angle in boost-phase. After the BM mass at the beginning of estimation, the BM attack angle and the modification of engine thrust denoting BM acceleration are modeled reasonably, the boost-phase BM trajectory estimation with ground based radar is well realized. The validity of this estimation method is testified by computer simulation with a typical example.展开更多
Oblique perforation of thick metallic plates by rigid projectiles with various nose shapes is studied in this paper. Two perforation mechanisms, i.e., the hole enlargement for a sharp projectile nose and the plugging ...Oblique perforation of thick metallic plates by rigid projectiles with various nose shapes is studied in this paper. Two perforation mechanisms, i.e., the hole enlargement for a sharp projectile nose and the plugging formation for a blunt projectile nose, are considered in the proposed analytical model. It is shown that the perforation of a thick plate is dominated by several non-dimensional numbers, i.e., the impact function, the geometry function of projectile, the non-dimensional thickness of target and the impact obliquity. Explicit formulae are obtained to predict the ballistic limit, residual velocity and directional change for the oblique perforation of thick metallic plates. The proposed model is able to predict the critical condition for the occurrence of ricochet. The proposed model is validated by comparing the predictions with other existing models and independent experimental data.展开更多
Energetic structural materials(ESMs)integrated a high energy density and rapid energy release with the ability to serve as structural materials.Here,a novel triple-phase TiZrHfTa_(0.7)W_(0.3)high-entropy alloy(HEA)was...Energetic structural materials(ESMs)integrated a high energy density and rapid energy release with the ability to serve as structural materials.Here,a novel triple-phase TiZrHfTa_(0.7)W_(0.3)high-entropy alloy(HEA)was fabricated and investigated as a potential ESM.A hierarchical microstructure was obtained with a main metastable body-centered-cubic(BCC)matrix with distributed Ta-W-rich BCC precipitates of various sizes and interwoven hexagonal close-packed(HCP)lamellar nano-plates.The compressive me-chanical properties were tested across a range of strain rates and demonstrated a brittle-to-ductile tran-sition as the strain rate increased while maintaining a high ultimate strength of approximately 2.5 GPa.This was due to the phase transformation from metastable matrix BCC to HCP structures.In addition,during the dynamic deformation,metal combustion originating from the failure surface was observed.Furthermore,the composition of the fragments was studied,and the results indicated that the addition of tungsten promoted combustion.Finally,the potential application of this HEA was evaluated by high-velocity penetration tests,and the results were compared to other typical structural materials for pene-trators and bullets.A comparison was conducted by assessing the geometries of the penetration channel employing two dimensionless parameters normalized by the projectile size,representing longitudinal and lateral damage,respectively.The normalized depth of the TiZrHfTa_(0.7)W_(0.3)HEA projectile was comparable to those of the other investigated materials,but the normalized diameter was the largest,showing an excellent ability to deliver lateral damage.展开更多
Compared with the one-dimensional trajectory correction technology which adjusts longitudinal range, not only does the two-dimensional trajectory correction technology adjust the force in velocity direction, but also ...Compared with the one-dimensional trajectory correction technology which adjusts longitudinal range, not only does the two-dimensional trajectory correction technology adjust the force in velocity direction, but also need to modulate the lateral force or trajectory (perpendicular to the vertical plane of fire direction). Therefore, the structure of control cabin of two-dimensional trajectory correction projectile (TDTCP) is more complicated than that of one-dimensional trajectory correction projectile (ODTCP). To simplify the structure of control cabin of TDTCP and reduce the cost, a scheme of adding a damping disk to the control cabin of ODTCP has been developed recently. The damping disk is unfolded at the right moment during its flight to change the ballistic drift of spin stabilized projectile. For this technical scheme of TDTCP, a fast and accurate impact point prediction method based on extended Kalman filter is presented. An approximate formula for predicting the ballistic drift and trajectory correction quantity is deduced. And the lateral correction capability for different fire angles and its influencing factors are analyzed. All the work is valuable for further research.展开更多
Industrial applications of aluminium and its alloys are restricted because of their poor tribological properties. Thermal spraying, laser surfacing, electron beam welding are the most widely used techniques to alter t...Industrial applications of aluminium and its alloys are restricted because of their poor tribological properties. Thermal spraying, laser surfacing, electron beam welding are the most widely used techniques to alter the surface morphology of base metal. Preliminary studies reveal that the coating and layering of aluminium alloys with ceramic particles enhance the ballistic resistance. Furthermore, among aluminium alloys,7075 aluminium alloy exhibits high strength which can be compared to that of steels and has profound applications in the designing of lightweight fortification structures and integrated protection systems. Having limitations such as poor bond integrity, formation of detrimental phases and interfacial reaction between reinforcement and substrate using fusion route to deposit hard particles paves the way to adopt friction stir processing for fabricating surface composites using different sizes of boron carbide particles as reinforcement on armour grade 7075 aluminium alloy as matrix in the present investigation. Wear and ballistic tests were carried out to assess the performance of friction stir processed AA7075 alloy. Significant improvement in wear resistance of friction stir processed surface composites is attributed to the change in wear mechanism from abrasion to adhesion. It has also been observed that the surface metal matrix composites have shown better ballistic resistance compared to the substrate AA7075 alloy. Addition of solid lubricant Mo S2 has reduced the depth of penetration of the projectile to half that of base metal AA7075 alloy. For the first time, the friction stir processing technique was successfully used to improve the wear and ballistic resistances of armour grade high strength AA7075 alloy.展开更多
The present experimental study investigates shock wave mitigation capability of potentially new personal protective equipment(PPE) suspension pads made from polyurea and shear thickening fluid(STF).The shock tube test...The present experimental study investigates shock wave mitigation capability of potentially new personal protective equipment(PPE) suspension pads made from polyurea and shear thickening fluid(STF).The shock tube test results show that when placed behind Twaron fabric systems with thickness ranging from 2 mm to 18 mm, the replacement of conventional flexible foam pad with STF and STF-infused foam pads with the same thickness of 20 mm greatly reduces the normalized peak pressure(by about 72% for each pad). However, this benefit is partially offset by a large increase in the normalized impulse(by about78% for the STF pad and 131% for the STF-infused foam pad) which may cause the shock wave mitigation performance of these two pads to become less effective. Interestingly, the use of 4 mm thick polyurea pad can greatly reduce the normalized peak pressure and impulse as well(by about 74% and 49%, respectively). These results reveal that among the potentially new suspension pads tested, the polyurea pad displays the best shock wave mitigation performance. Therefore, polyurea has potential for use as a suspension pad in personal protective equipment requiring shock wave mitigation capability such as fabric ballistic vests, bomb suits and combat helmets.展开更多
Kevlar is the most commonly used material as armour for protection against bullets used in hand guns because of its impact resistance, high strength and low weight. These properties make Kevlar an ideal material to be...Kevlar is the most commonly used material as armour for protection against bullets used in hand guns because of its impact resistance, high strength and low weight. These properties make Kevlar an ideal material to be used in bullet-proof vests as compared to other materials. In the present study, different numbers of layers of Kevlar with different weights are tested to determine the weights and the number of layers needed to design a safe bullet-proof vest. For this purpose, several ballistic tests were performed on combinations of ballistic gel and Kevlar layers of different weights. Ballistic impacts are generated by 9 mm Parabellum ammunition. The objective is to assess the characteristics of high-speed ballistic penetration into a combination of a gel and Kevlar and determine the number of layers needed to safely stop the 9 mm bullet and thereby contribute to the design of safe bullet-proof vests. The tests provide information on the distances the bullets can travel in a gel/Kevlar medium before they are stopped and to identify the resistance capabilities of Kevlar of different grams per square meter(GSM). The tests were conducted with the use of a chronograph in a controlled test environment. Specifically, results identify the number of layers of Kevlar required to stop a 9 mm Parabellum projectile, and the effectiveness of using different number of layers of GSM Kevlar material.展开更多
Ballistic behaviour of different zones of post-weld heat-treated(PWHT)magnesium alloy(AZ31B)target against 7.62 mm×39 mm armour-piercing(AP)projectile with a striking velocity of(430±20)m/s was determined.Ma...Ballistic behaviour of different zones of post-weld heat-treated(PWHT)magnesium alloy(AZ31B)target against 7.62 mm×39 mm armour-piercing(AP)projectile with a striking velocity of(430±20)m/s was determined.Magnesium alloy(AZ31B)welded joints were prepared by using friction stir welding(FSW)process and subjected to different heat treatment conditions.The microhardness values of non-heat-treated and heat-treated FSW joints were investigated.The results indicated that PWHT process(250°C,1 h)has improved the microhardness of heat-treated FSW joints.Scanning electron microscope(SEM)microstructure showed that heat treatment has caused the formation of fineα-Mg grains and tiny precipitates and made the dissolution ofβ-Mg17Al12 phase into the Mg matrix.The ballistic behaviour of PWHT zones was estimated by measuring the depth of penetration(DOP)of the projectile.Lower DOP value was observed for the base metal zone(BMZ)of a heat-treated welded joint.Post ballistic SEM examinations on the cross-section of all three zones of crater region showed the formation of adiabatic shear band(ASB).展开更多
文摘The optimal guidance problem for an interceptor against a ballistic missile with active defense is investigated in this paper.A class of optimal guidance schemes are proposed based on linear quadratic differential game method and numerical solution of Riccati differential equation.By choosing proper parameters, the proposed guidance schemes are able to drive the interceptor to the target and away from the defender simultaneously.Additionally, fuel cost, control saturation,chattering phenomenon and parameters selection were taken into account.Satisfaction of the proposed guidance schemes of the saddle point condition is proven theoretically.Finally, nonlinear numerical examples are included to demonstrate the effectiveness and performance of the developed guidance approaches.Comparison of control performance between different guidance schemes are presented and analysis.
文摘Ballistic impact test of different-scale casings is an efficient way to demonstrate the casing containment capability at the preliminary design stage of the engine. For the sake of studying the titanium alloy TC4 casing perfonnance, the ballistic tests of flat and curved simulation casing are implemented by using two flat blades of different sizes as the projectile. The impact mechanism and failure of the target are discussed. Impact of the projectile is a highly nonlinear transient process with the large deformation of the target. On the impact, failures of the flat casing and the subscale casing are similar, concluding two parts, the global dish- ing and localized ductile tearing. The main localized failure mode combines plugging （shear） and petaling （shear） if the projectile perforates or penetrates, while crater （shear） if the projectile rebounds. The ballistic limit equation is verified by the test data and the results show that this empirical equation could be a practical way to estimate the critical velocity.
基金supported by the National Science Fund for Distinguished Young Scholars of China (Grant No. 61025006)
文摘The wideband electromagnetic characteristics of missile targets in midcourse are the foundation of midcourse attack-defense confrontation. This paper proposes a novel electromagnetic scattering modeling method for midcourse targets based on a pre- cise scattering center model, in which the nonideal scattering phenomenon, shielding effect and micro-motion are taken into consideration for the first time. Firstly, a precise scattering center model incorporating both the sliding scattering and artist- tropic scattering is established. Then the change rule of the target attitude is generalized, and a checking method of the scatter- ing center shielding effect is proposed for rotationally symmetric targets. Afterwards, a novel dynamic electromagnetic scat- tering model is presented, where the scattering center model updates along with the variation of the target attitude and can characterize the change of the electromagnetic characteristics of midcourse targets exactly. Finally, in light of the established model, the dynamic electromagnetic characteristics within different attitude angle bounds are analyzed by stages, and some useful conclusions are obtained. Experiment results from the measured data in anechoic chamber verify the validity of the proposed modeling method and relevant analysis.
文摘A conditional boost-phase trajectory estimation method based on ballistic missile （BM） information database and classification is developed to estimate and predict boos-phase BM trajectory. The main uncertain factors to describe BM dynamics equation are reduced to the control law of trajectory pitch angle in boost-phase. After the BM mass at the beginning of estimation, the BM attack angle and the modification of engine thrust denoting BM acceleration are modeled reasonably, the boost-phase BM trajectory estimation with ground based radar is well realized. The validity of this estimation method is testified by computer simulation with a typical example.
文摘Oblique perforation of thick metallic plates by rigid projectiles with various nose shapes is studied in this paper. Two perforation mechanisms, i.e., the hole enlargement for a sharp projectile nose and the plugging formation for a blunt projectile nose, are considered in the proposed analytical model. It is shown that the perforation of a thick plate is dominated by several non-dimensional numbers, i.e., the impact function, the geometry function of projectile, the non-dimensional thickness of target and the impact obliquity. Explicit formulae are obtained to predict the ballistic limit, residual velocity and directional change for the oblique perforation of thick metallic plates. The proposed model is able to predict the critical condition for the occurrence of ricochet. The proposed model is validated by comparing the predictions with other existing models and independent experimental data.
基金supported by the National Natu-ral Science Foundation of China(Nos.51401028,51271193 and 11790292)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB22040303)the Innovation Pro-gram(No.237099000000170004).
文摘Energetic structural materials(ESMs)integrated a high energy density and rapid energy release with the ability to serve as structural materials.Here,a novel triple-phase TiZrHfTa_(0.7)W_(0.3)high-entropy alloy(HEA)was fabricated and investigated as a potential ESM.A hierarchical microstructure was obtained with a main metastable body-centered-cubic(BCC)matrix with distributed Ta-W-rich BCC precipitates of various sizes and interwoven hexagonal close-packed(HCP)lamellar nano-plates.The compressive me-chanical properties were tested across a range of strain rates and demonstrated a brittle-to-ductile tran-sition as the strain rate increased while maintaining a high ultimate strength of approximately 2.5 GPa.This was due to the phase transformation from metastable matrix BCC to HCP structures.In addition,during the dynamic deformation,metal combustion originating from the failure surface was observed.Furthermore,the composition of the fragments was studied,and the results indicated that the addition of tungsten promoted combustion.Finally,the potential application of this HEA was evaluated by high-velocity penetration tests,and the results were compared to other typical structural materials for pene-trators and bullets.A comparison was conducted by assessing the geometries of the penetration channel employing two dimensionless parameters normalized by the projectile size,representing longitudinal and lateral damage,respectively.The normalized depth of the TiZrHfTa_(0.7)W_(0.3)HEA projectile was comparable to those of the other investigated materials,but the normalized diameter was the largest,showing an excellent ability to deliver lateral damage.
文摘Compared with the one-dimensional trajectory correction technology which adjusts longitudinal range, not only does the two-dimensional trajectory correction technology adjust the force in velocity direction, but also need to modulate the lateral force or trajectory (perpendicular to the vertical plane of fire direction). Therefore, the structure of control cabin of two-dimensional trajectory correction projectile (TDTCP) is more complicated than that of one-dimensional trajectory correction projectile (ODTCP). To simplify the structure of control cabin of TDTCP and reduce the cost, a scheme of adding a damping disk to the control cabin of ODTCP has been developed recently. The damping disk is unfolded at the right moment during its flight to change the ballistic drift of spin stabilized projectile. For this technical scheme of TDTCP, a fast and accurate impact point prediction method based on extended Kalman filter is presented. An approximate formula for predicting the ballistic drift and trajectory correction quantity is deduced. And the lateral correction capability for different fire angles and its influencing factors are analyzed. All the work is valuable for further research.
基金Financial assistance from Armament Research Board, New Delhi, India
文摘Industrial applications of aluminium and its alloys are restricted because of their poor tribological properties. Thermal spraying, laser surfacing, electron beam welding are the most widely used techniques to alter the surface morphology of base metal. Preliminary studies reveal that the coating and layering of aluminium alloys with ceramic particles enhance the ballistic resistance. Furthermore, among aluminium alloys,7075 aluminium alloy exhibits high strength which can be compared to that of steels and has profound applications in the designing of lightweight fortification structures and integrated protection systems. Having limitations such as poor bond integrity, formation of detrimental phases and interfacial reaction between reinforcement and substrate using fusion route to deposit hard particles paves the way to adopt friction stir processing for fabricating surface composites using different sizes of boron carbide particles as reinforcement on armour grade 7075 aluminium alloy as matrix in the present investigation. Wear and ballistic tests were carried out to assess the performance of friction stir processed AA7075 alloy. Significant improvement in wear resistance of friction stir processed surface composites is attributed to the change in wear mechanism from abrasion to adhesion. It has also been observed that the surface metal matrix composites have shown better ballistic resistance compared to the substrate AA7075 alloy. Addition of solid lubricant Mo S2 has reduced the depth of penetration of the projectile to half that of base metal AA7075 alloy. For the first time, the friction stir processing technique was successfully used to improve the wear and ballistic resistances of armour grade high strength AA7075 alloy.
基金supported by the Ministry of Education,Singapore(R265000533112)
文摘The present experimental study investigates shock wave mitigation capability of potentially new personal protective equipment(PPE) suspension pads made from polyurea and shear thickening fluid(STF).The shock tube test results show that when placed behind Twaron fabric systems with thickness ranging from 2 mm to 18 mm, the replacement of conventional flexible foam pad with STF and STF-infused foam pads with the same thickness of 20 mm greatly reduces the normalized peak pressure(by about 72% for each pad). However, this benefit is partially offset by a large increase in the normalized impulse(by about78% for the STF pad and 131% for the STF-infused foam pad) which may cause the shock wave mitigation performance of these two pads to become less effective. Interestingly, the use of 4 mm thick polyurea pad can greatly reduce the normalized peak pressure and impulse as well(by about 74% and 49%, respectively). These results reveal that among the potentially new suspension pads tested, the polyurea pad displays the best shock wave mitigation performance. Therefore, polyurea has potential for use as a suspension pad in personal protective equipment requiring shock wave mitigation capability such as fabric ballistic vests, bomb suits and combat helmets.
基金partially funded by the National Research Foundation
文摘Kevlar is the most commonly used material as armour for protection against bullets used in hand guns because of its impact resistance, high strength and low weight. These properties make Kevlar an ideal material to be used in bullet-proof vests as compared to other materials. In the present study, different numbers of layers of Kevlar with different weights are tested to determine the weights and the number of layers needed to design a safe bullet-proof vest. For this purpose, several ballistic tests were performed on combinations of ballistic gel and Kevlar layers of different weights. Ballistic impacts are generated by 9 mm Parabellum ammunition. The objective is to assess the characteristics of high-speed ballistic penetration into a combination of a gel and Kevlar and determine the number of layers needed to safely stop the 9 mm bullet and thereby contribute to the design of safe bullet-proof vests. The tests provide information on the distances the bullets can travel in a gel/Kevlar medium before they are stopped and to identify the resistance capabilities of Kevlar of different grams per square meter(GSM). The tests were conducted with the use of a chronograph in a controlled test environment. Specifically, results identify the number of layers of Kevlar required to stop a 9 mm Parabellum projectile, and the effectiveness of using different number of layers of GSM Kevlar material.
文摘Ballistic behaviour of different zones of post-weld heat-treated(PWHT)magnesium alloy(AZ31B)target against 7.62 mm×39 mm armour-piercing(AP)projectile with a striking velocity of(430±20)m/s was determined.Magnesium alloy(AZ31B)welded joints were prepared by using friction stir welding(FSW)process and subjected to different heat treatment conditions.The microhardness values of non-heat-treated and heat-treated FSW joints were investigated.The results indicated that PWHT process(250°C,1 h)has improved the microhardness of heat-treated FSW joints.Scanning electron microscope(SEM)microstructure showed that heat treatment has caused the formation of fineα-Mg grains and tiny precipitates and made the dissolution ofβ-Mg17Al12 phase into the Mg matrix.The ballistic behaviour of PWHT zones was estimated by measuring the depth of penetration(DOP)of the projectile.Lower DOP value was observed for the base metal zone(BMZ)of a heat-treated welded joint.Post ballistic SEM examinations on the cross-section of all three zones of crater region showed the formation of adiabatic shear band(ASB).
