2021 Vol. 41, No. 2
Display Method:
Read OL
PDF 
Cited by
2021, 41(2): 021400.
Abstract:
2021, 41(2): 021401.
doi: 10.11883/bzycj-2020-0307
Abstract:
Advances on ultrahigh-velocity launch techniques were introduced, which involving magnetically-driven metallic flyer, metallic foil electrically explosion driven plastic flyer and three-stage light gas gun based on graded density impactor (GDI) driven flyer techniques. The magnetically-driven flyer technique utilizes the Lorentz force produced by the interact of intense current and strong magnetic field to accelerate a metallic flyer shocklessly, and a 25 mm×13 mm×1.0 mm aluminum flyer was launched to 46 km/s on the ZR machnine at Sandia National Laboratory (SNL). This technique has been developed in Institute of Fluid Physics (IFP) since 2008, series compact pulsed power generators such as CQ-1.5, CQ-4, CQ-7 with increasing loading capability in turn, were established and hypervelocity metallic flyer launching experiments were conducted. The shape of the loading electrode for launching a flyer was optimized by using a magnetic hydrodynamic code, and an aluminum flyer with the initial sizes of 10 mm×6 mm×0.33 mm was accelerated to 18 km/s within a distance of up to several millimeters. The metallic foil electrically-explosion driven flyer technique, usually named as electrical gun (EG), uses the high-pressure gas produced by electrical exploding of a metal foil to accelerate a plastic flyer. A Kapton flyer with the sizes of 9.5 mm×9.5 mm×0.3 mm was accelerated to 18 km/s in Lawrence Livermore National Laboratory. The electrical gun technique has been developed in IFP since 2006, series electrical guns with increasing loading capability were established, namely 14.4-kJ EG, 98-kJ EG and 200-kJ EG. A unified numerical simulation program was developed to give insight to the progress of metallic foil electrical explosion and to optimize the experimental designs. By using 98-kJ and 200-kJ electric guns, the Mylar flyers with the sizes of\begin{document}$\varnothing $\end{document} ![]()
![]()
\begin{document}$\varnothing $\end{document} ![]()
![]()
Advances on ultrahigh-velocity launch techniques were introduced, which involving magnetically-driven metallic flyer, metallic foil electrically explosion driven plastic flyer and three-stage light gas gun based on graded density impactor (GDI) driven flyer techniques. The magnetically-driven flyer technique utilizes the Lorentz force produced by the interact of intense current and strong magnetic field to accelerate a metallic flyer shocklessly, and a 25 mm×13 mm×1.0 mm aluminum flyer was launched to 46 km/s on the ZR machnine at Sandia National Laboratory (SNL). This technique has been developed in Institute of Fluid Physics (IFP) since 2008, series compact pulsed power generators such as CQ-1.5, CQ-4, CQ-7 with increasing loading capability in turn, were established and hypervelocity metallic flyer launching experiments were conducted. The shape of the loading electrode for launching a flyer was optimized by using a magnetic hydrodynamic code, and an aluminum flyer with the initial sizes of 10 mm×6 mm×0.33 mm was accelerated to 18 km/s within a distance of up to several millimeters. The metallic foil electrically-explosion driven flyer technique, usually named as electrical gun (EG), uses the high-pressure gas produced by electrical exploding of a metal foil to accelerate a plastic flyer. A Kapton flyer with the sizes of 9.5 mm×9.5 mm×0.3 mm was accelerated to 18 km/s in Lawrence Livermore National Laboratory. The electrical gun technique has been developed in IFP since 2006, series electrical guns with increasing loading capability were established, namely 14.4-kJ EG, 98-kJ EG and 200-kJ EG. A unified numerical simulation program was developed to give insight to the progress of metallic foil electrical explosion and to optimize the experimental designs. By using 98-kJ and 200-kJ electric guns, the Mylar flyers with the sizes of
2021, 41(2): 021402.
doi: 10.11883/bzycj-2020-0396
Abstract:
The electromagnetic radiation from hypervelocity impact is an important physical phenomenon of solid matter under strong impact loadings, and the research results have important application value in fields of deep space exploration, protection design of spacecraft against space debris, assessment of weapon damage, etc. In this paper, the electromagnetic radiation caused by hypervelocity impact was briefly summarized. The time-frequency characteristics of microwave and flash by hypervelocity impact under various collision conditions were respectively provided. The radiation models of microwave generated by hypervelocity impact were analyzed from two aspects of material fragmentation and plasma phase transition. The luminescence mechanisms during hypervelocity impact were described as a whole, and the radiation models of continuous spectrum and line spectrum were performed. The shortcomings and development trend of electromagnetic radiation by hypervelocity impact were pointed out. The results show that the intensity and frequency of microwave and flash are closely dependent on the target thickness, impact material, environmental pressure as well as collisional velocity and angle. The microwave is in the form of pulses lasting from a few to hundreds of microseconds. The intensity of the flash, however, accumulates rapidly and then decays slowly. When the plasma is not accomplished during the hypervelocity impact, the microwave radiation is mainly formed because of the movement of ionized debris. Once the plasma is formed, the effects of the collision radiation in the plasma, namely the bremsstrahlung and recombination radiation, and the expansion of the plasma should also be taken into account, and the specific spectrum lies on the characteristic parameters of plasma. In vacuum, only the gasification and plasma due to the impact are necessary to be considered in the flash spectrum, while the gasification and even plasma phase transition resulted from the ablation between the gas and debris should be involved at high environmental pressure.
The electromagnetic radiation from hypervelocity impact is an important physical phenomenon of solid matter under strong impact loadings, and the research results have important application value in fields of deep space exploration, protection design of spacecraft against space debris, assessment of weapon damage, etc. In this paper, the electromagnetic radiation caused by hypervelocity impact was briefly summarized. The time-frequency characteristics of microwave and flash by hypervelocity impact under various collision conditions were respectively provided. The radiation models of microwave generated by hypervelocity impact were analyzed from two aspects of material fragmentation and plasma phase transition. The luminescence mechanisms during hypervelocity impact were described as a whole, and the radiation models of continuous spectrum and line spectrum were performed. The shortcomings and development trend of electromagnetic radiation by hypervelocity impact were pointed out. The results show that the intensity and frequency of microwave and flash are closely dependent on the target thickness, impact material, environmental pressure as well as collisional velocity and angle. The microwave is in the form of pulses lasting from a few to hundreds of microseconds. The intensity of the flash, however, accumulates rapidly and then decays slowly. When the plasma is not accomplished during the hypervelocity impact, the microwave radiation is mainly formed because of the movement of ionized debris. Once the plasma is formed, the effects of the collision radiation in the plasma, namely the bremsstrahlung and recombination radiation, and the expansion of the plasma should also be taken into account, and the specific spectrum lies on the characteristic parameters of plasma. In vacuum, only the gasification and plasma due to the impact are necessary to be considered in the flash spectrum, while the gasification and even plasma phase transition resulted from the ablation between the gas and debris should be involved at high environmental pressure.
2021, 41(2): 021403.
doi: 10.11883/bzycj-2020-0289
Abstract:
Based on the formation mechanism of the debris cloud caused by the projectile hypervelocity impacting onto a thin plate, the Whipple shield can effectively protect the spacecraft from space debris and micrometeoroid. By reviewing the research and development of the Whipple shield, and compares the mechanical effects and protective performance of multilayer, stuffed and sandwich shield. The paper also summarizes the application of numerical simulation methods and their improvement for the hypervelocity impact of protective structures containing materials such as foam and honeycomb, etc. By addressing the results of hypervelocity impact tests and numerical simulations of relevant materials, suggestions are made for the future research of the Whipple shield.
Based on the formation mechanism of the debris cloud caused by the projectile hypervelocity impacting onto a thin plate, the Whipple shield can effectively protect the spacecraft from space debris and micrometeoroid. By reviewing the research and development of the Whipple shield, and compares the mechanical effects and protective performance of multilayer, stuffed and sandwich shield. The paper also summarizes the application of numerical simulation methods and their improvement for the hypervelocity impact of protective structures containing materials such as foam and honeycomb, etc. By addressing the results of hypervelocity impact tests and numerical simulations of relevant materials, suggestions are made for the future research of the Whipple shield.
2021, 41(2): 021404.
doi: 10.11883/bzycj-2020-0310
Abstract:
The typical damage of gas-filled pressure vessel impacted by hypervelocity projectile includes perforation and crack instability, which lead to gas leakage and explosion. The effect of gas pressure on front wall damage is still unclear so far. Experiments and numerical simulations are reported, in which spherical aluminum gas-filled pressure vessels with different inner pressures were impacted by spherical aluminum projectiles traveling at hypervelocity. A two-stage light gas gun was used to launch an aluminum alloy spherical projectile into the pressure vessel at hypervelocity. The size and cross-section morphology of the perforation with different inner pressures were obtained. According to the various purposes of numerical simulation, two kinds of two-dimensional axis symmetric pressure vessel models were established. The numerical model for type A is a whole model which behaves as the actual pressure vessel. The numerical model for type B included a vessel wall on which there was a stress with same value as inner pressure and non-pressure local gas. The numerical results of perforation diameter and morphology, shock wave propagation, and hoop tensile stress on the hole edge were obtained. The effects of gas on the morphology and diameter of holes in the front wall, as well as the hoop stress on the edge of hole were explored. The mechanism of shock wave in the gas affecting the crack instability in the front wall was discussed and supported by a description of the shock wave propagation. It is shown that the inner flanging morphology on the edge of hole is influenced by the gas pressure. It bends more lightly when the gas pressure is higher. It is shown that the influence of gas pressure on the hole diameter is positive, although it is less obvious than that of wall thickness and impact velocity. The hoop tensile stress is affected by not only the reflected shock wave from the back wall, but also the stress wave propagation in the vessel wall, which is in proportion to gas pressure.
The typical damage of gas-filled pressure vessel impacted by hypervelocity projectile includes perforation and crack instability, which lead to gas leakage and explosion. The effect of gas pressure on front wall damage is still unclear so far. Experiments and numerical simulations are reported, in which spherical aluminum gas-filled pressure vessels with different inner pressures were impacted by spherical aluminum projectiles traveling at hypervelocity. A two-stage light gas gun was used to launch an aluminum alloy spherical projectile into the pressure vessel at hypervelocity. The size and cross-section morphology of the perforation with different inner pressures were obtained. According to the various purposes of numerical simulation, two kinds of two-dimensional axis symmetric pressure vessel models were established. The numerical model for type A is a whole model which behaves as the actual pressure vessel. The numerical model for type B included a vessel wall on which there was a stress with same value as inner pressure and non-pressure local gas. The numerical results of perforation diameter and morphology, shock wave propagation, and hoop tensile stress on the hole edge were obtained. The effects of gas on the morphology and diameter of holes in the front wall, as well as the hoop stress on the edge of hole were explored. The mechanism of shock wave in the gas affecting the crack instability in the front wall was discussed and supported by a description of the shock wave propagation. It is shown that the inner flanging morphology on the edge of hole is influenced by the gas pressure. It bends more lightly when the gas pressure is higher. It is shown that the influence of gas pressure on the hole diameter is positive, although it is less obvious than that of wall thickness and impact velocity. The hoop tensile stress is affected by not only the reflected shock wave from the back wall, but also the stress wave propagation in the vessel wall, which is in proportion to gas pressure.
2021, 41(2): 021405.
doi: 10.11883/bzycj-2020-0299
Abstract:
Graded-impedance shield is a kind of structure against space debris with excellent protection performance verified by experiments. Graded wave impedance material is used as its core buffer. In order to further optimize the design of graded wave impedance material and promote the engineering application of graded-impedance shield, it is necessary to deeply understand the protection mechanism of the shield against hypervelocity impact. The difference of debris cloud characteristics is an important factor affecting the protection performance of shields against space debris. Further study on the debris cloud characteristics of graded-impedance shield and comparison with aluminum alloy Whipple shield with the same areal density can deepen the understanding of the protection mechanism of graded-impedance shield against hypervelocity impact. In this paper, the hypervelocity impact experiments were carried out at 3.5, 5.0 and 6.5 km/s for the graded-impedance shield and aluminum alloy Whipple shield with the same areal density. The characteristics of the debris cloud formed by the projectile impacting the graded wave impedance material and aluminum alloy material with the same areal density were compared after the experiment, and the characteristics of debris cloud fragmentation was quantitatively analyzed and compared through numerical simulation, including the characteristics of cloud mass, quantity and temperature distribution. As results, it is shown that the fragmentation characteristics of projectile fragments in debris cloud structure are obviously different when the projectile impacts the graded wave impedance material and aluminum alloy material, respectively. When the impact wave impedance gradient material is used, the projectile head is broken more fully, and the projectile lateral expansion degree is increased. In the high-speed section (6.5 km/s), due to the joint action of impedance gradient and material melting effect for the graded wave impedance material, the delamination phenomenon appears in the head of debris cloud. The results show that the change of debris cloud characteristics under hypervelocity impact is one of the key factors that the protective performance of graded wave impedance material is better than that of the aluminum alloy with the same areal density.
Graded-impedance shield is a kind of structure against space debris with excellent protection performance verified by experiments. Graded wave impedance material is used as its core buffer. In order to further optimize the design of graded wave impedance material and promote the engineering application of graded-impedance shield, it is necessary to deeply understand the protection mechanism of the shield against hypervelocity impact. The difference of debris cloud characteristics is an important factor affecting the protection performance of shields against space debris. Further study on the debris cloud characteristics of graded-impedance shield and comparison with aluminum alloy Whipple shield with the same areal density can deepen the understanding of the protection mechanism of graded-impedance shield against hypervelocity impact. In this paper, the hypervelocity impact experiments were carried out at 3.5, 5.0 and 6.5 km/s for the graded-impedance shield and aluminum alloy Whipple shield with the same areal density. The characteristics of the debris cloud formed by the projectile impacting the graded wave impedance material and aluminum alloy material with the same areal density were compared after the experiment, and the characteristics of debris cloud fragmentation was quantitatively analyzed and compared through numerical simulation, including the characteristics of cloud mass, quantity and temperature distribution. As results, it is shown that the fragmentation characteristics of projectile fragments in debris cloud structure are obviously different when the projectile impacts the graded wave impedance material and aluminum alloy material, respectively. When the impact wave impedance gradient material is used, the projectile head is broken more fully, and the projectile lateral expansion degree is increased. In the high-speed section (6.5 km/s), due to the joint action of impedance gradient and material melting effect for the graded wave impedance material, the delamination phenomenon appears in the head of debris cloud. The results show that the change of debris cloud characteristics under hypervelocity impact is one of the key factors that the protective performance of graded wave impedance material is better than that of the aluminum alloy with the same areal density.
2021, 41(2): 021406.
doi: 10.11883/bzycj-2020-0266
Abstract:
With the continuous increase of centimeter-scale space debris, the exploration and design of new high-performance shields has become an urgent need. Based on the shield of active materials, the hypervelocity impact experiments with different projectile sizes and impact velocities were carried out by using a two-stage light gas gun. The image characteristics of debris clouds under different impact conditions were obtained and analyzed by laser shadowgraph photography. The damage characteristics of the rear wall of the active Whipple shield were studied. Through the statistical analysis of the number of craters, the influences of active materials on the fragmentation of projectiles under different impact velocities were obtained. Compared with the classical Christiansen ballistic limit equation, the protective performance of energetic active material shield was obtained, and the ballistic limit curve of the new shield was fitted. Analysis suggests that shock initiation characteristics of active materials under impact enhanced the shield performance. When impacted by the space debris, active material shield firstly uses its mechanical strength for primary crushing. During this process, the energetic material shield has an explosive reaction with an instantaneous temperature being as high as 3 800 K, which can promote fragmentation, melting and reduce the size of the space debris. At the same time, the explosion products with high temperature, pressure and high speed motion produce a negative acceleration to the projectile fragments, reducing the axial kinetic energy. The explosion products of the active materials are mostly gaseous, which greatly reduce the number of the fragments with penetration ability in the debris cloud. The penetration failure of the rear plate only comes from the fragments generated by the fragmentation of the projectile. Under the combined action of impact and explosion, the active materials shield can not only fully break and decelerate space debris, but also greatly reduce the number of solid debris in debris cloud, thereby produce a sharp rise in the spacecraft protection ability, and the maximum protection ability can be increased by 45% when the velocity is 2.31 km/s.
With the continuous increase of centimeter-scale space debris, the exploration and design of new high-performance shields has become an urgent need. Based on the shield of active materials, the hypervelocity impact experiments with different projectile sizes and impact velocities were carried out by using a two-stage light gas gun. The image characteristics of debris clouds under different impact conditions were obtained and analyzed by laser shadowgraph photography. The damage characteristics of the rear wall of the active Whipple shield were studied. Through the statistical analysis of the number of craters, the influences of active materials on the fragmentation of projectiles under different impact velocities were obtained. Compared with the classical Christiansen ballistic limit equation, the protective performance of energetic active material shield was obtained, and the ballistic limit curve of the new shield was fitted. Analysis suggests that shock initiation characteristics of active materials under impact enhanced the shield performance. When impacted by the space debris, active material shield firstly uses its mechanical strength for primary crushing. During this process, the energetic material shield has an explosive reaction with an instantaneous temperature being as high as 3 800 K, which can promote fragmentation, melting and reduce the size of the space debris. At the same time, the explosion products with high temperature, pressure and high speed motion produce a negative acceleration to the projectile fragments, reducing the axial kinetic energy. The explosion products of the active materials are mostly gaseous, which greatly reduce the number of the fragments with penetration ability in the debris cloud. The penetration failure of the rear plate only comes from the fragments generated by the fragmentation of the projectile. Under the combined action of impact and explosion, the active materials shield can not only fully break and decelerate space debris, but also greatly reduce the number of solid debris in debris cloud, thereby produce a sharp rise in the spacecraft protection ability, and the maximum protection ability can be increased by 45% when the velocity is 2.31 km/s.
2021, 41(2): 021407.
doi: 10.11883/bzycj-2020-0304
Abstract:
To investigate the hypervelocity impact mechanism of a tungsten alloy projectile on a concrete target, a new dynamic plasticity-based failure model for metal was developed by introducing Lode angle, dynamic enhancement factor, temperature softening term and stress triaxiality, and a new constitutive model for concrete was proposed by introducing strain rate effect, pressure dependence, Lode angle and free water effect. The advanced measurement technologies were introduced to determine the dynamic mechanical behaviors of materials, then the materials parameters were used to numerically simulate the hypervelocity penetration of a tungsten alloy projectile into a concrete target. Based on a 57/10 two-stage light gas gun, the experiments were carried out on the hypervelocity impact of the tungsten alloy projectile on the concrete target. And according to the computed tomography scanning images of the damaged concrete targets, the crater characteristics in the targets were analyzed. Then the relationships of the total penetration depth and the residual length of the projectile with the initial impact velocity of the projectile were obtained. The penetration of the projectile and the stress wave propagation in the concrete target were analyzed by the theoretical method. The achieved results are as follows. (1) By utilizing the new constitutive models for the metal and concrete, the failure morphology of the concrete derived from numerical simulation is consistent with that from the experiment. (2) The craters are structured by spalling areas and projectile holes, the transverse failure effect shows a significant advantage over low-velocity penetration, and the volume of craters is approximately proportional to the kinetic energy of projectiles. (3) The penetration depth increases at first and then decreases with the increase of the impact velocities, the decrease of the penetration depth under high velocity is due to the decrease of the rigid penetration stage after the erosive penetration stage. (4) A theoretical penetration model is proposed, which can be used to predict the depth of penetration, the residual length of the projectile and the diameter of the mushroom-like head, et al. (5) A theoretical stress wave propagation model is developed and the theoretical results of stress waves are in good agreement with the experimental ones.
To investigate the hypervelocity impact mechanism of a tungsten alloy projectile on a concrete target, a new dynamic plasticity-based failure model for metal was developed by introducing Lode angle, dynamic enhancement factor, temperature softening term and stress triaxiality, and a new constitutive model for concrete was proposed by introducing strain rate effect, pressure dependence, Lode angle and free water effect. The advanced measurement technologies were introduced to determine the dynamic mechanical behaviors of materials, then the materials parameters were used to numerically simulate the hypervelocity penetration of a tungsten alloy projectile into a concrete target. Based on a 57/10 two-stage light gas gun, the experiments were carried out on the hypervelocity impact of the tungsten alloy projectile on the concrete target. And according to the computed tomography scanning images of the damaged concrete targets, the crater characteristics in the targets were analyzed. Then the relationships of the total penetration depth and the residual length of the projectile with the initial impact velocity of the projectile were obtained. The penetration of the projectile and the stress wave propagation in the concrete target were analyzed by the theoretical method. The achieved results are as follows. (1) By utilizing the new constitutive models for the metal and concrete, the failure morphology of the concrete derived from numerical simulation is consistent with that from the experiment. (2) The craters are structured by spalling areas and projectile holes, the transverse failure effect shows a significant advantage over low-velocity penetration, and the volume of craters is approximately proportional to the kinetic energy of projectiles. (3) The penetration depth increases at first and then decreases with the increase of the impact velocities, the decrease of the penetration depth under high velocity is due to the decrease of the rigid penetration stage after the erosive penetration stage. (4) A theoretical penetration model is proposed, which can be used to predict the depth of penetration, the residual length of the projectile and the diameter of the mushroom-like head, et al. (5) A theoretical stress wave propagation model is developed and the theoretical results of stress waves are in good agreement with the experimental ones.
2021, 41(2): 021408.
doi: 10.11883/bzycj-2020-0303
Abstract:
In order to research the penetration characteristics and damage mechanism of multi-layer targets under hypervelocity impact, experiments and numerical simulations were carried out on a rod-shaped 93W projectile impacting a multi-layer Q345 steel target. A gram-order rod-shaped 93W projectile together with a sabot was launched by a 57/10 mm two-stage light gas gun to penetrate into a ten-layer Q345 target. The damage photos of the target after penetration were transformed into binary images by a Matlab processing software. The equivalent diameter of the center hole, the number and total areas of the holes, the diameters of damage circles of the ten-layer target were summed up and analyzed. The AUTODYN software was used to perform the smoothed particle hydrodynamics simulation. Then the microscopical data of the target plates were obtained by scanning electron microscopy (SEM) and optical microscopy to analyze the microstructure and element composition. Results show that a rod-shaped 93W projectile could penetrate 8 or 9 layers of a ten-layer Q345 target under different initial impact velocities. Perforated lips, petal-shaped plastic deformation, tearing, cratering and bulging were formed in target plates. These failure modes are attributed to plastic expanding failure and shear tearing under shear stress. The damage mode of the first three layers of the target is dominated by hypervelocity perforation due to the high impact velocity, with many holes but small area, while the holes in the later layers are few, but the diameter increases first and then decreases as the masses and velocities of fragments decrease. The simulation results were verified by the experimental results. They are in good agreement with the experimental results. Micro analysis shows that the materials of the target and projectile are melt, while the grains are broken up, refined, melt and recrystallized in the target plates. There are aggregated micropores and microcracks formed during the penetration process. The micro analysis results show that the damage failure is mainly caused by the combined effects of thermal stress during the cooling process of the molten mixture and shear tearing under the shear stress, which is consistent with the macro-scopical results.
In order to research the penetration characteristics and damage mechanism of multi-layer targets under hypervelocity impact, experiments and numerical simulations were carried out on a rod-shaped 93W projectile impacting a multi-layer Q345 steel target. A gram-order rod-shaped 93W projectile together with a sabot was launched by a 57/10 mm two-stage light gas gun to penetrate into a ten-layer Q345 target. The damage photos of the target after penetration were transformed into binary images by a Matlab processing software. The equivalent diameter of the center hole, the number and total areas of the holes, the diameters of damage circles of the ten-layer target were summed up and analyzed. The AUTODYN software was used to perform the smoothed particle hydrodynamics simulation. Then the microscopical data of the target plates were obtained by scanning electron microscopy (SEM) and optical microscopy to analyze the microstructure and element composition. Results show that a rod-shaped 93W projectile could penetrate 8 or 9 layers of a ten-layer Q345 target under different initial impact velocities. Perforated lips, petal-shaped plastic deformation, tearing, cratering and bulging were formed in target plates. These failure modes are attributed to plastic expanding failure and shear tearing under shear stress. The damage mode of the first three layers of the target is dominated by hypervelocity perforation due to the high impact velocity, with many holes but small area, while the holes in the later layers are few, but the diameter increases first and then decreases as the masses and velocities of fragments decrease. The simulation results were verified by the experimental results. They are in good agreement with the experimental results. Micro analysis shows that the materials of the target and projectile are melt, while the grains are broken up, refined, melt and recrystallized in the target plates. There are aggregated micropores and microcracks formed during the penetration process. The micro analysis results show that the damage failure is mainly caused by the combined effects of thermal stress during the cooling process of the molten mixture and shear tearing under the shear stress, which is consistent with the macro-scopical results.
2021, 41(2): 021409.
doi: 10.11883/bzycj-2020-0323
Abstract:
In order to study the feasibility and effectiveness of the shield with separated rear wall (SRW), both the hypervelocity experiments and simulations were performed to investigate the performances of shields with different separated rear walls. The effect of impact velocity on the shielding performance was also studied. Three kinds of shields were designed, including a Whipple shield and two kinds of SRW shields. The AUTODYN software was based on to numerically simulate the penetration of 6.0-mm-diameter aluminum projectiles with the initial impact velocities of 5.0, 6.0, 7.0 and 8.3 km/s, respectively, into the shields. By comparing the damages in the backs of the rear walls among the three kinds of shields, the preliminary conclusion was drawn that the performances of the SRW shields were better than that of the Whipple shield. And the higher the impact velocity, the more obvious the advantage of the SRW shields. The tests were carried out in the hypervelocity ballistic range of China Aerodynamics Research and Development Center. The diameter of an aluminum projectile is 6.0 mm, and the impact velocity is about 8.3 km/s. The perforation and spall characteristics of the rear walls in the tests are consistent with the simulated results. The experiments not only prove the effectiveness of the simulation method, but also prove that the SRW shields have better protecting performances. Compared with the complete aluminum plate, a new free interface is added inside the structures of the SRW shields, which will reflect the shock wave generated in the impact process. Thus the strength of the shock wave that spreads to the second plate is reduced, and the damage in the SRW shields is alleviated. As the impact velocity increases, the main damage mode on the rear wall will change from the penetration damage mode to the impact damage mode, and the propagation of shock wave will be the main reason for the damage of the rear wall, which leads to better protecting performance of the SRW shields at higher impact velocities.
In order to study the feasibility and effectiveness of the shield with separated rear wall (SRW), both the hypervelocity experiments and simulations were performed to investigate the performances of shields with different separated rear walls. The effect of impact velocity on the shielding performance was also studied. Three kinds of shields were designed, including a Whipple shield and two kinds of SRW shields. The AUTODYN software was based on to numerically simulate the penetration of 6.0-mm-diameter aluminum projectiles with the initial impact velocities of 5.0, 6.0, 7.0 and 8.3 km/s, respectively, into the shields. By comparing the damages in the backs of the rear walls among the three kinds of shields, the preliminary conclusion was drawn that the performances of the SRW shields were better than that of the Whipple shield. And the higher the impact velocity, the more obvious the advantage of the SRW shields. The tests were carried out in the hypervelocity ballistic range of China Aerodynamics Research and Development Center. The diameter of an aluminum projectile is 6.0 mm, and the impact velocity is about 8.3 km/s. The perforation and spall characteristics of the rear walls in the tests are consistent with the simulated results. The experiments not only prove the effectiveness of the simulation method, but also prove that the SRW shields have better protecting performances. Compared with the complete aluminum plate, a new free interface is added inside the structures of the SRW shields, which will reflect the shock wave generated in the impact process. Thus the strength of the shock wave that spreads to the second plate is reduced, and the damage in the SRW shields is alleviated. As the impact velocity increases, the main damage mode on the rear wall will change from the penetration damage mode to the impact damage mode, and the propagation of shock wave will be the main reason for the damage of the rear wall, which leads to better protecting performance of the SRW shields at higher impact velocities.
2021, 41(2): 023301.
doi: 10.11883/bzycj-2020-0181
Abstract:
Amorphous alloys have attracted wide interest from from domestic and foreign research scholars in recent years. In order to explore the deformation behavior and high-speed penetration performance of Hf-based bulk amorphous alloys, the static (10−3 s−1) and dynamic (102−104 s−1) mechanical properties tests of Hf-based bulk amorphous alloy materials were carried out. Based on the structure of the jacketed rod, penetration experiments were performed as well. Two kinds of jacketed rod projectiles, in Hf-based bulk amorphous alloy and 45 steel, penetrated into the semi-infinite 45 steel targets with velocities in the range of 1000−1500 m/s. The experimental results show that the Hf-based bulk amorphous alloy has a high fracture strength of 1.69 GPa under quasi-static compression (10−3 s−1), and 1.15 GPa under dynamic compression (102−104 s−1). The fracture of Hf-based bulk amorphous alloy is accompanied by a energy release phenomenon. The process of Hf-based bulk amorphous alloy jacketed rod projectiles penetrating the steel target can be divided into three stages: pit opening stage, penetration stage of the jacketed rod structure and remaining projectile penetration. The Hf amorphous alloy has an obvious energy-releasing reaction during the penetration process. The energy-releasing reaction of the Hf-based bulk amorphous alloy enhanced the damage effect of the projectile significantly by enlarging the diameter of the penetration bullet hole, and increasing the penetration depth and bullet hole volume. Compared with the 45 steel jacketed rod within the tested kinetic energy range, the range of increase in the diameter of the penetration single hole, the penetration depth and the volume of penetration bullet holes are 14.4%−23.8%, 5.2%−13.1%, and 12.9%−54.3%, respectively. In conclusion, the Hf-based bulk amorphous alloy jacketed rod projectile exhibits excellent penetration performance, which can provide new ideas for the application of amorphous alloy materials in the field of efficient damage.
Amorphous alloys have attracted wide interest from from domestic and foreign research scholars in recent years. In order to explore the deformation behavior and high-speed penetration performance of Hf-based bulk amorphous alloys, the static (10−3 s−1) and dynamic (102−104 s−1) mechanical properties tests of Hf-based bulk amorphous alloy materials were carried out. Based on the structure of the jacketed rod, penetration experiments were performed as well. Two kinds of jacketed rod projectiles, in Hf-based bulk amorphous alloy and 45 steel, penetrated into the semi-infinite 45 steel targets with velocities in the range of 1000−1500 m/s. The experimental results show that the Hf-based bulk amorphous alloy has a high fracture strength of 1.69 GPa under quasi-static compression (10−3 s−1), and 1.15 GPa under dynamic compression (102−104 s−1). The fracture of Hf-based bulk amorphous alloy is accompanied by a energy release phenomenon. The process of Hf-based bulk amorphous alloy jacketed rod projectiles penetrating the steel target can be divided into three stages: pit opening stage, penetration stage of the jacketed rod structure and remaining projectile penetration. The Hf amorphous alloy has an obvious energy-releasing reaction during the penetration process. The energy-releasing reaction of the Hf-based bulk amorphous alloy enhanced the damage effect of the projectile significantly by enlarging the diameter of the penetration bullet hole, and increasing the penetration depth and bullet hole volume. Compared with the 45 steel jacketed rod within the tested kinetic energy range, the range of increase in the diameter of the penetration single hole, the penetration depth and the volume of penetration bullet holes are 14.4%−23.8%, 5.2%−13.1%, and 12.9%−54.3%, respectively. In conclusion, the Hf-based bulk amorphous alloy jacketed rod projectile exhibits excellent penetration performance, which can provide new ideas for the application of amorphous alloy materials in the field of efficient damage.
2021, 41(2): 023302.
doi: 10.11883/bzycj-2020-0057
Abstract:
For ideal long-rod penetration, by analyzing the approximate solutions of the Alekseevskii-Tate model for long-rod penetration, it is pointed out that the single deceleration index α is not sufficient to fully describle the quasi-steady process of long-rod penetration. This paper redefines two dimensionless parameters, namely Johnson demage parameter ΦJp and characteristic time parameter β, and α=β/ΦJp. The analysis shows that two characteristic parameters ΦJp and β (or α and β) can completely characterize the impact velocity of the projectile tail in the quasi-steady process of long-rod penetration. If the dimensionless critical impact velocity vc* is introduced, the quasi-steady process of long-rod penetration can be fully characterized. In addition, this paper strictly proves that the degree of deviation from the steady state in the penetration process can be determined by α, and confirms that by determining ΦJp and β (or α and β), the design of long-rod penetration can be guided for offensive and defensive needs.
For ideal long-rod penetration, by analyzing the approximate solutions of the Alekseevskii-Tate model for long-rod penetration, it is pointed out that the single deceleration index α is not sufficient to fully describle the quasi-steady process of long-rod penetration. This paper redefines two dimensionless parameters, namely Johnson demage parameter ΦJp and characteristic time parameter β, and α=β/ΦJp. The analysis shows that two characteristic parameters ΦJp and β (or α and β) can completely characterize the impact velocity of the projectile tail in the quasi-steady process of long-rod penetration. If the dimensionless critical impact velocity vc* is introduced, the quasi-steady process of long-rod penetration can be fully characterized. In addition, this paper strictly proves that the degree of deviation from the steady state in the penetration process can be determined by α, and confirms that by determining ΦJp and β (or α and β), the design of long-rod penetration can be guided for offensive and defensive needs.
2021, 41(2): 023303.
doi: 10.11883/bzycj-2020-0090
Abstract:
Q420 circular steel tubes are widely used to build large-scale steel structures. Such buildings serving in mountain areas are subject to atmospheric corrosion and impact load. In order to study the effect of atmospheric corrosion on the crashworthiness of Q420 steel tube members during service, a material model considering corrosion damage was proposed which treated corrosion damage as a change in material parameters. Specifically, a damage factor ω was introduced to modify the Voce constitutive equation based on the one-dimensional damage theory. A constitutive equation for low alloy steel varied with the degree of corrosion was deduced, these model parameters were determined through accelerated corrosion test that used acidic solution to accelerate steel corrosion and used static force to stretch the specimens. Based on the proposed constitutive method, relevant material properties were defined by utilizing the ABAQUS software to establish the finite element model of the Q420 steel tubes. A number of 0.84 meters long Q420 steel tube member models within different degrees of corrosion were developed, and these pipes were impacted at their mid-span by a flat-headed impactor with a certain mass and initial velocity. An explicit dynamic algorithm has been used for the simulation to analyze impact response law of rigid impactor and corroded steel pipes under various initial conditions. In addition, a series of impact tests were conducted to compare the behaviour of pre-corroded Q420 steel tubes subjected to lateral impact by drop hammers falling through changing initial height. The weight loss of pipes respectively was 0%, 10%, 20%, 30% and 40%, and the speed of moving hammers was 4.00, 5.79 and 7.43 m/s. Steel tube specimens were subjected to a constant axial pressure, without considering the effect of the axial force on test results. Numerical results were compared with test results to verify the rationality of the established models. According to numerical and experimental results, it demonstrates that atmospheric corrosion leads to a decrease in the nominal strength of the materials, which has a significant effect on the impact resistance of Q420 steel tubes and causes variation in the time history curve of impact force. With increase of corrosion degree of specimens, the yield strength and ultimate tensile strength of Q420 steel materials show a downward trend. As weight loss of Q420 steel tube increases, peak value of impact force decreases and duration and depth of impact increases. It indicates the decline of lateral impact resistance of Q420 steel tubes affected by atmospheric corrosion that impact stiffness of Q420 steel tubes decreases and overall deformation energy consumption of these components increases after corroded. The initial conditions of impactor have different effects on collision process under same kinetic energy increment. Compared with the increase of the initial mass, increase in the peak value of impact force obtained by increasing the initial velocity of impactor is greater, while the increase of duration is smaller.
Q420 circular steel tubes are widely used to build large-scale steel structures. Such buildings serving in mountain areas are subject to atmospheric corrosion and impact load. In order to study the effect of atmospheric corrosion on the crashworthiness of Q420 steel tube members during service, a material model considering corrosion damage was proposed which treated corrosion damage as a change in material parameters. Specifically, a damage factor ω was introduced to modify the Voce constitutive equation based on the one-dimensional damage theory. A constitutive equation for low alloy steel varied with the degree of corrosion was deduced, these model parameters were determined through accelerated corrosion test that used acidic solution to accelerate steel corrosion and used static force to stretch the specimens. Based on the proposed constitutive method, relevant material properties were defined by utilizing the ABAQUS software to establish the finite element model of the Q420 steel tubes. A number of 0.84 meters long Q420 steel tube member models within different degrees of corrosion were developed, and these pipes were impacted at their mid-span by a flat-headed impactor with a certain mass and initial velocity. An explicit dynamic algorithm has been used for the simulation to analyze impact response law of rigid impactor and corroded steel pipes under various initial conditions. In addition, a series of impact tests were conducted to compare the behaviour of pre-corroded Q420 steel tubes subjected to lateral impact by drop hammers falling through changing initial height. The weight loss of pipes respectively was 0%, 10%, 20%, 30% and 40%, and the speed of moving hammers was 4.00, 5.79 and 7.43 m/s. Steel tube specimens were subjected to a constant axial pressure, without considering the effect of the axial force on test results. Numerical results were compared with test results to verify the rationality of the established models. According to numerical and experimental results, it demonstrates that atmospheric corrosion leads to a decrease in the nominal strength of the materials, which has a significant effect on the impact resistance of Q420 steel tubes and causes variation in the time history curve of impact force. With increase of corrosion degree of specimens, the yield strength and ultimate tensile strength of Q420 steel materials show a downward trend. As weight loss of Q420 steel tube increases, peak value of impact force decreases and duration and depth of impact increases. It indicates the decline of lateral impact resistance of Q420 steel tubes affected by atmospheric corrosion that impact stiffness of Q420 steel tubes decreases and overall deformation energy consumption of these components increases after corroded. The initial conditions of impactor have different effects on collision process under same kinetic energy increment. Compared with the increase of the initial mass, increase in the peak value of impact force obtained by increasing the initial velocity of impactor is greater, while the increase of duration is smaller.
2021, 41(2): 024201.
doi: 10.11883/bzycj-2020-0118
Abstract:
It is necessary to study the erosive wear caused by conveying granules, but it is difficult to track particles trajectories which are required for erosion prediction, especially in shot blasting experiments. In an erosion test, marine sand grains are ejected from a sand-blasting gun and impact Q235 steel plate. The impinging velocities and impinging locations of the sand grains with different inlet air pressure are measured statistically. The two-way coupling process inside or outside the blast nozzle between sand grains and high-speed compressible air are numerically simulated to numerically describe the trajectories of particles. In this simulation case, some approaches are studied and compared with the experimental results. Considering the influence of compressible air on the boundary flow separation of the sand, a new drag law, for the case that the relative Mach number of irregularly shaped particles is approximate to 1, is proposed by making drag coefficient change with the relative Mach number. Local slopes, the angle of which is random, are assumed on the wall to simulating the rough wall rebound effect. The mean value of the slope angles is 0º and the standard deviation is 20º. Magnus lift force is also integrated into the numerical simulation to enlarge the jet angle of particles and make the erosive scar larger. By combining the nonpherical high Mach number drag law, rough wall model and Magnus lift force model, the simulation achieves satisfying result, in which the velocity magnitudes and impinging location distribution of particles agree well with the experimental data. It indicates that the particles trajectories in simulation are also roughly coincident with the real ones in experiment. This work proves tracking approaches affect the particles trajectories significantly and provides a valid tool to summarize and verify the erosion formula or to predict erosive wear.
It is necessary to study the erosive wear caused by conveying granules, but it is difficult to track particles trajectories which are required for erosion prediction, especially in shot blasting experiments. In an erosion test, marine sand grains are ejected from a sand-blasting gun and impact Q235 steel plate. The impinging velocities and impinging locations of the sand grains with different inlet air pressure are measured statistically. The two-way coupling process inside or outside the blast nozzle between sand grains and high-speed compressible air are numerically simulated to numerically describe the trajectories of particles. In this simulation case, some approaches are studied and compared with the experimental results. Considering the influence of compressible air on the boundary flow separation of the sand, a new drag law, for the case that the relative Mach number of irregularly shaped particles is approximate to 1, is proposed by making drag coefficient change with the relative Mach number. Local slopes, the angle of which is random, are assumed on the wall to simulating the rough wall rebound effect. The mean value of the slope angles is 0º and the standard deviation is 20º. Magnus lift force is also integrated into the numerical simulation to enlarge the jet angle of particles and make the erosive scar larger. By combining the nonpherical high Mach number drag law, rough wall model and Magnus lift force model, the simulation achieves satisfying result, in which the velocity magnitudes and impinging location distribution of particles agree well with the experimental data. It indicates that the particles trajectories in simulation are also roughly coincident with the real ones in experiment. This work proves tracking approaches affect the particles trajectories significantly and provides a valid tool to summarize and verify the erosion formula or to predict erosive wear.
2021, 41(2): 025401.
doi: 10.11883/bzycj-2020-0093
Abstract:
To explore the explosion characteristics of methane-air mixtures with low concentration of methane at various humidities, a device for producing and containing water-saturated air was developed. The temperature and flow of pipes, air bag and explosion vessel were controlled to obtain methane-air mixture with variable humidity. The 20 L spherical explosion vessel was employed to analyze the effect of relative humidity and methane concentration on methane explosion characteristics (i.e., maximum explosion pressure, maximum rate of pressure rise, lower explosion limit and laminar burning velocity). It is concluded that the maximum explosion pressure and maximum rate of pressure rise show a linear decrease with an increasing value of humidity. As the humidity of gas mixture changes from 27.7% to 80.1%, the lower explosion limit of methane in air increases from 5.15% to 5.25% with a rising rate of 1.9%. The laminar burning velocity performs a similar linear downtrend with the increase of relative humidity. Under the given circumstances, the relative humidity has no significant influence on the explosion characteristic of methane-air mixture, which can be ascribed to the low value of partial pressure of water vapor at ambient condition. However, this influence cannot be neglected as the water vapor increases to a certain extent level at high temperatures and high pressures.
To explore the explosion characteristics of methane-air mixtures with low concentration of methane at various humidities, a device for producing and containing water-saturated air was developed. The temperature and flow of pipes, air bag and explosion vessel were controlled to obtain methane-air mixture with variable humidity. The 20 L spherical explosion vessel was employed to analyze the effect of relative humidity and methane concentration on methane explosion characteristics (i.e., maximum explosion pressure, maximum rate of pressure rise, lower explosion limit and laminar burning velocity). It is concluded that the maximum explosion pressure and maximum rate of pressure rise show a linear decrease with an increasing value of humidity. As the humidity of gas mixture changes from 27.7% to 80.1%, the lower explosion limit of methane in air increases from 5.15% to 5.25% with a rising rate of 1.9%. The laminar burning velocity performs a similar linear downtrend with the increase of relative humidity. Under the given circumstances, the relative humidity has no significant influence on the explosion characteristic of methane-air mixture, which can be ascribed to the low value of partial pressure of water vapor at ambient condition. However, this influence cannot be neglected as the water vapor increases to a certain extent level at high temperatures and high pressures.
