2016 Vol. 36, No. 2
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2016, 36(2): 145-152.
doi: 10.11883/1001-1455(2016)02-0145-08
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Abstract:
Using a digital laser dynamic caustics experimental system, the fracture behavior of blast-induced cracks in flawed materials under both ordinary borehole and pre-notched borehole were studied. The results show that the main crack propagating along the pre-notched direction is 10 μs earlier than that along the non-notched direction, which attributes the blast energy release along with the pre-notched direction. The initiation toughness and average speed of the main crack in the pre-notched direction is 0.58 MN/m3/2 and 277 m/s, respectively, corresponding to 54% and 86% of the ordinary blasting. For the pre-notched blasting, The space is large enough for the detonation gas expansion, when the main crack goes through with the pre-crack, and the detonation gas energy moving to the both ends of the pre-crack, leading mainly mode Ⅰ type initiation fracture of the wing crack, with which its mode Ⅰ dynamic stress intensity factor stays between 0.6 MN/m3/2 and 0.8 MN/m3/2 during 60-250 μs, which forms an obvious platform in the histories of mode Ⅰ dynamic stress intensity factor, and the decrease rate of wing crack velocity are also delayed. Eventually, the duration time of the crack propagation and the crack length are increased by 22.7% and 17.8%, respectively, compared with the ordinary borehole blasting.
Using a digital laser dynamic caustics experimental system, the fracture behavior of blast-induced cracks in flawed materials under both ordinary borehole and pre-notched borehole were studied. The results show that the main crack propagating along the pre-notched direction is 10 μs earlier than that along the non-notched direction, which attributes the blast energy release along with the pre-notched direction. The initiation toughness and average speed of the main crack in the pre-notched direction is 0.58 MN/m3/2 and 277 m/s, respectively, corresponding to 54% and 86% of the ordinary blasting. For the pre-notched blasting, The space is large enough for the detonation gas expansion, when the main crack goes through with the pre-crack, and the detonation gas energy moving to the both ends of the pre-crack, leading mainly mode Ⅰ type initiation fracture of the wing crack, with which its mode Ⅰ dynamic stress intensity factor stays between 0.6 MN/m3/2 and 0.8 MN/m3/2 during 60-250 μs, which forms an obvious platform in the histories of mode Ⅰ dynamic stress intensity factor, and the decrease rate of wing crack velocity are also delayed. Eventually, the duration time of the crack propagation and the crack length are increased by 22.7% and 17.8%, respectively, compared with the ordinary borehole blasting.
2016, 36(2): 153-160.
doi: 10.11883/1001-1455(2016)02-0153-08
Abstract:
In this work, by adopting dynamic mesh technology along with the spring based smoothing method and the laying based zone moving method, we have numerically solved the axisymmetric N-S equations, analyzed the flow field mechanism and thermal shock characteristics, identified the thermal environment evaluating and influencing factors that are essential for dealing with problems in decision making of the new land-based concentric canister launcher (CCL) under the high-speed thermal shock load condition, and determined the evaluation index of the thermal environment. The mathematic model was established by optimal Latin hypercube design and radial basis function neural network (RBFNN), thus greatly facilitating the automatic modeling and compensating for the large amount of calculation for CFD. The intelligent decision research of the influencing factors for the missile thermal environment was performed using the RBFNN training method. The numerical results show that the thermal environment of the internal canister and the external cylinder are improved by the cryogenic gas coming from the cylinder port; the approximate model is accurate enough to meet the engineering standards required; the influencing factors for the missile thermal environment load are, according to their ranking from high to low, are the following: The diameter of the cylinder bottom baffle plate, the length of the cylinder bottom baffle plate, the height of the deflector. The research of the influencing factors will lay a solid foundation for the multidisciplinary optimization of the thermal environment.
In this work, by adopting dynamic mesh technology along with the spring based smoothing method and the laying based zone moving method, we have numerically solved the axisymmetric N-S equations, analyzed the flow field mechanism and thermal shock characteristics, identified the thermal environment evaluating and influencing factors that are essential for dealing with problems in decision making of the new land-based concentric canister launcher (CCL) under the high-speed thermal shock load condition, and determined the evaluation index of the thermal environment. The mathematic model was established by optimal Latin hypercube design and radial basis function neural network (RBFNN), thus greatly facilitating the automatic modeling and compensating for the large amount of calculation for CFD. The intelligent decision research of the influencing factors for the missile thermal environment was performed using the RBFNN training method. The numerical results show that the thermal environment of the internal canister and the external cylinder are improved by the cryogenic gas coming from the cylinder port; the approximate model is accurate enough to meet the engineering standards required; the influencing factors for the missile thermal environment load are, according to their ranking from high to low, are the following: The diameter of the cylinder bottom baffle plate, the length of the cylinder bottom baffle plate, the height of the deflector. The research of the influencing factors will lay a solid foundation for the multidisciplinary optimization of the thermal environment.
2016, 36(2): 161-169.
doi: 10.11883/1001-1455(2016)02-0161-09
Abstract:
Based on damage mechanics theory, a mechanical model for rock blasting was established considering of the rock heterogeneity, in which rock blasting was considered as two consecutive stages: the dynamic stage caused by the stress wave and the static stage caused by explosion gas pressure. The cracks evolution of cutting seam cartridge blasting under different in-situ stress conditions was numerically simulated. The numerical results indicate that the blasting cracks mainly initiate around the cutting seam and propagate along the cutting seam direction. For different in-situ stress fields, the crack propagation will be suppressed when the maximum in-situ stress direction is perpendicular to the cutting seam direction, while promoted when the maximum in-situ stress direction is parallel to the cutting seam direction. The crack direction is controlled by the direction of cutting seam and maximum in-situ stress, while the crack propagation is suppressed by the in-situ stress field.
Based on damage mechanics theory, a mechanical model for rock blasting was established considering of the rock heterogeneity, in which rock blasting was considered as two consecutive stages: the dynamic stage caused by the stress wave and the static stage caused by explosion gas pressure. The cracks evolution of cutting seam cartridge blasting under different in-situ stress conditions was numerically simulated. The numerical results indicate that the blasting cracks mainly initiate around the cutting seam and propagate along the cutting seam direction. For different in-situ stress fields, the crack propagation will be suppressed when the maximum in-situ stress direction is perpendicular to the cutting seam direction, while promoted when the maximum in-situ stress direction is parallel to the cutting seam direction. The crack direction is controlled by the direction of cutting seam and maximum in-situ stress, while the crack propagation is suppressed by the in-situ stress field.
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2016, 36(2): 170-176.
doi: 10.11883/1001-1455(2016)02-0170-07
Abstract:
Based on the blunt projectile impact test of woven Kevlar/Epoxy composite laminates, the deformation and failure modes of the composite laminates subjected to impact load were analyzed. Experimental results show that the deformation and failure behaviors were exhibited in the following ways: the global elastic deformation, the global plastic deformation with local embedded failure on the front surface, and the delaminated failure with fibers tension fracture on the back surface. The finite element software LS-DYNA 971 was employed to analyze the dynamic response of the woven Kevlar/Epoxy composite laminates subject to impact loading. Numerical simulation results show that there is a good agreement of the deformation/failure modes and the back face center-point deflection of the specimens, with those of the experimental results. The failure area on the front face is a circle embedded region, but a square failure region on the back face. The numerical simulation is focused on studying the effects of the number of layers on the dynamic response of the structure. Optimizing the number of the layers can effectively reduce the permanent deflection, increase the energy absorption efficiency and improve the impact resistance performance of the structure within a given range of impulses.
Based on the blunt projectile impact test of woven Kevlar/Epoxy composite laminates, the deformation and failure modes of the composite laminates subjected to impact load were analyzed. Experimental results show that the deformation and failure behaviors were exhibited in the following ways: the global elastic deformation, the global plastic deformation with local embedded failure on the front surface, and the delaminated failure with fibers tension fracture on the back surface. The finite element software LS-DYNA 971 was employed to analyze the dynamic response of the woven Kevlar/Epoxy composite laminates subject to impact loading. Numerical simulation results show that there is a good agreement of the deformation/failure modes and the back face center-point deflection of the specimens, with those of the experimental results. The failure area on the front face is a circle embedded region, but a square failure region on the back face. The numerical simulation is focused on studying the effects of the number of layers on the dynamic response of the structure. Optimizing the number of the layers can effectively reduce the permanent deflection, increase the energy absorption efficiency and improve the impact resistance performance of the structure within a given range of impulses.
2016, 36(2): 177-182.
doi: 10.11883/1001-1455(2016)02-0177-06
Abstract:
In this paper, dynamic behaviors of metal materials driven by collision of head-on sliding detonation waves were diagnosed with pulsed X-ray radiography and DPS, the physical images of free surface ejecta and body fragmentation on Sn and W were obtained, the difference in the dynamic behaviors of Sn and W was analyzed, and its qualitative physical analysis was discussed. The results provide significant experimental data for the study of dynamic behaviors of metal materials driven by collision of head-on sliding detonation waves.
In this paper, dynamic behaviors of metal materials driven by collision of head-on sliding detonation waves were diagnosed with pulsed X-ray radiography and DPS, the physical images of free surface ejecta and body fragmentation on Sn and W were obtained, the difference in the dynamic behaviors of Sn and W was analyzed, and its qualitative physical analysis was discussed. The results provide significant experimental data for the study of dynamic behaviors of metal materials driven by collision of head-on sliding detonation waves.
2016, 36(2): 183-188.
doi: 10.11883/1001-1455(2016)02-0183-06
Abstract:
The radius of the initial smoke cloud is an essential parameter frequently used when evaluating the smoke shelter efficiency. In this paper, the expansion process and the initial parameters of the smoke cloud were analyzed using theoretical assumptions based on a smoke generating device. The expansion process of smoke clouds were respectively divided into the isentropic expansion stage and the free expansion stage, and differential equations of the smoke cloud expansion were then established through analyzing the expansion process. After that the differential equations were solved using the Runge-Kutta method, and the radius variation with time of the initial smoke cloud was presented. The experiment results prove that this method can be adopted to describe the basic law rules in the expansion of the smoke cloud and to calculate the initial parameters of the smoke generator
The radius of the initial smoke cloud is an essential parameter frequently used when evaluating the smoke shelter efficiency. In this paper, the expansion process and the initial parameters of the smoke cloud were analyzed using theoretical assumptions based on a smoke generating device. The expansion process of smoke clouds were respectively divided into the isentropic expansion stage and the free expansion stage, and differential equations of the smoke cloud expansion were then established through analyzing the expansion process. After that the differential equations were solved using the Runge-Kutta method, and the radius variation with time of the initial smoke cloud was presented. The experiment results prove that this method can be adopted to describe the basic law rules in the expansion of the smoke cloud and to calculate the initial parameters of the smoke generator
2016, 36(2): 189-197.
doi: 10.11883/1001-1455(2016)02-0189-09
Abstract:
Integrating supercritical carbon dioxide jet, known for its capability of reducing the threshold pressure of the rock and protecting the reservoir, with the combined swirling and round jet, known for its capability of enhancing the efficiency of rock erosion owing to its features, we would have a new highly efficient jet technology that may be called as combined swirling and round jet with supercritical carbon dioxide. In order to investigate the law governing its rock erosion, we carried out an experiment aiming at comparing the rock erosion capacity of this method with that of the conventional water jet and studying the effects produced by the of five important factors (the impeller length, the central hole diameter of the impeller, the length of the mixing chamber, the standoff, and the jet pressure) on rock erosion by using the nozzle which has been designed and fabricated especially for this purpose. The result shows that the rock erosion efficiency of this jet method is 42.9% higher than that of the conventional water round jet; the swirling and round jet with supercritical carbon dioxide may lead to the occurrence of rock mass breakaway; with the increase of the impeller length, the length of the mixing chamber and the standoff, the erosion performance tends to slacken after an initial good efficiency; the increase of the central hore diameter of the impeller can result in both a greater erosion depth and a reduced erosion diameter; and erosion efficiency can be enhanced by increasing the jet pressure. The results from the present study can be serve as an experimental basis for further research.
Integrating supercritical carbon dioxide jet, known for its capability of reducing the threshold pressure of the rock and protecting the reservoir, with the combined swirling and round jet, known for its capability of enhancing the efficiency of rock erosion owing to its features, we would have a new highly efficient jet technology that may be called as combined swirling and round jet with supercritical carbon dioxide. In order to investigate the law governing its rock erosion, we carried out an experiment aiming at comparing the rock erosion capacity of this method with that of the conventional water jet and studying the effects produced by the of five important factors (the impeller length, the central hole diameter of the impeller, the length of the mixing chamber, the standoff, and the jet pressure) on rock erosion by using the nozzle which has been designed and fabricated especially for this purpose. The result shows that the rock erosion efficiency of this jet method is 42.9% higher than that of the conventional water round jet; the swirling and round jet with supercritical carbon dioxide may lead to the occurrence of rock mass breakaway; with the increase of the impeller length, the length of the mixing chamber and the standoff, the erosion performance tends to slacken after an initial good efficiency; the increase of the central hore diameter of the impeller can result in both a greater erosion depth and a reduced erosion diameter; and erosion efficiency can be enhanced by increasing the jet pressure. The results from the present study can be serve as an experimental basis for further research.
2016, 36(2): 198-209.
doi: 10.11883/1001-1455(2016)02-0198-12
Abstract:
In order to study the evolution of dynamic overpressure of deflagration, a simulation was carried out in an open end pipe. It was found that the dynamic pressure was closely correlated with the gas velocity so that they always arrive at the peak value at the same time. In addition, the first positive peak of the dynamic pressure was almost several times greater than that of the second. This may indicate that the blast wave has a greater influence on the dynamic pressure than the flame does. An empirical prediction equation was given to calculate the first and second positive peaks based on the propagation time. Maximum dynamic pressures were increased with the propagation distance in all the three directions (x, y and z), and so was with time. The maximum dynamic pressure value in the x direction was almost several thousand times greater than those in the other two directions. Compared with the explosive overpressure, the influence on the explosive damage by the dynamic pressure in the y and z direction was quite small. Three empirical formulas were given to calculate the maximum dynamic pressures in different directions. The relationship between the dynamic pressure and the square of the gas velocity was verified. An empirical formula of the dynamic overpressure was also given based on the length-diameter ratio and the gas velocity. The results may provide a reference for the study on the gas explosion in the limited spaces.
In order to study the evolution of dynamic overpressure of deflagration, a simulation was carried out in an open end pipe. It was found that the dynamic pressure was closely correlated with the gas velocity so that they always arrive at the peak value at the same time. In addition, the first positive peak of the dynamic pressure was almost several times greater than that of the second. This may indicate that the blast wave has a greater influence on the dynamic pressure than the flame does. An empirical prediction equation was given to calculate the first and second positive peaks based on the propagation time. Maximum dynamic pressures were increased with the propagation distance in all the three directions (x, y and z), and so was with time. The maximum dynamic pressure value in the x direction was almost several thousand times greater than those in the other two directions. Compared with the explosive overpressure, the influence on the explosive damage by the dynamic pressure in the y and z direction was quite small. Three empirical formulas were given to calculate the maximum dynamic pressures in different directions. The relationship between the dynamic pressure and the square of the gas velocity was verified. An empirical formula of the dynamic overpressure was also given based on the length-diameter ratio and the gas velocity. The results may provide a reference for the study on the gas explosion in the limited spaces.
2016, 36(2): 210-217.
doi: 10.11883/1001-1455(2016)02-0210-08
Abstract:
Aiming at solving the problem of the double ring-stiffened cylindrical shell structure collided by multiple bodies, a numerical simulation and a dynamic model test were carried out to explore the structural deformation, the impact force change and the energy conversion by using MSC.Dytran. Compared with the model tests, it is found that the double ring-stiffened cylindrical shell impacted by multiple bodies is a transient dynamic response process. Under enormous impact loading, shell plates in collision region will quickly generate plastic deformation; the shell impacted by multiple bodies will result in a damage to a certain degree; the impact forces will interfere with each other and then lead to the nonlinearity becoming even more significant. The results show that the external shell of the double ring-stiffened cylindrical shell can provide a better protection for the inner shell. The deformation of the structure will absorb most of the impact energy. So by optimizing the external shell's energy-absorbing efficiency a better protection against the impact can be achieved.
Aiming at solving the problem of the double ring-stiffened cylindrical shell structure collided by multiple bodies, a numerical simulation and a dynamic model test were carried out to explore the structural deformation, the impact force change and the energy conversion by using MSC.Dytran. Compared with the model tests, it is found that the double ring-stiffened cylindrical shell impacted by multiple bodies is a transient dynamic response process. Under enormous impact loading, shell plates in collision region will quickly generate plastic deformation; the shell impacted by multiple bodies will result in a damage to a certain degree; the impact forces will interfere with each other and then lead to the nonlinearity becoming even more significant. The results show that the external shell of the double ring-stiffened cylindrical shell can provide a better protection for the inner shell. The deformation of the structure will absorb most of the impact energy. So by optimizing the external shell's energy-absorbing efficiency a better protection against the impact can be achieved.
2016, 36(2): 218-223.
doi: 10.11883/1001-1455(2016)02-0218-06
Abstract:
In order to study the gas explosion hazards under different initial temperatures and high pressures, an experimental study was conducted on methane/air explosion under high temperatures and pressures with a special environmental testing system for studying explosion characteristics, with which the explosion limits were obtained under high temperatures (25-200℃) and high pressures (0.1-1.0 MPa) and so were the maximum explosion pressure and ignition delay time were also under high initial temperatures (25-200 ℃). The experimental results show that with the initial temperature and pressure rising up, the upper gas explosive limit increases, its lower limit decreases, resulting in a widened range of explosive limits. Compared with the narrower range of explosive limits under ordinary temperatures and pressures, the width of the explosive range at 200 ℃ and 1.0 MPa was increased by 101.77% so that the gas explosive probability increases. With the initial temperature rising up, the maximum gas explosive pressure decreases. Compared with the maximum explosive pressure at 25 ℃ and 0.1 MPa, the one at 200 ℃ and 0.1 MPa decreases by 35.89%. When the initial temperature increases, the ignition delay time of gas explosion is shortened. Based on the analysis of the experimental results and the reference of safety principles, a preliminary assessment method of the gas explosion hazard is put forward, which provides a certain basis for the prevention and treatment of gas explosion.
In order to study the gas explosion hazards under different initial temperatures and high pressures, an experimental study was conducted on methane/air explosion under high temperatures and pressures with a special environmental testing system for studying explosion characteristics, with which the explosion limits were obtained under high temperatures (25-200℃) and high pressures (0.1-1.0 MPa) and so were the maximum explosion pressure and ignition delay time were also under high initial temperatures (25-200 ℃). The experimental results show that with the initial temperature and pressure rising up, the upper gas explosive limit increases, its lower limit decreases, resulting in a widened range of explosive limits. Compared with the narrower range of explosive limits under ordinary temperatures and pressures, the width of the explosive range at 200 ℃ and 1.0 MPa was increased by 101.77% so that the gas explosive probability increases. With the initial temperature rising up, the maximum gas explosive pressure decreases. Compared with the maximum explosive pressure at 25 ℃ and 0.1 MPa, the one at 200 ℃ and 0.1 MPa decreases by 35.89%. When the initial temperature increases, the ignition delay time of gas explosion is shortened. Based on the analysis of the experimental results and the reference of safety principles, a preliminary assessment method of the gas explosion hazard is put forward, which provides a certain basis for the prevention and treatment of gas explosion.
2016, 36(2): 224-229.
doi: 10.11883/1001-1455(2016)02-0224-06
Abstract:
The explosive fracturing technique is often adopted to produce and expand fractures due to its great shock waves, thus improving the low permeability of oil reservoirs. Based on the distribution characteristics of the explosive fracturing network and applying the Laplace transform and the Stehfest numerical inversion, this paper presents a new analytic mathematical production model for the complex-flow to an explosive fracturing well and obtains the formulas for the oil output under the constant pressure in different boundary conditions. On the basis of the model validation, this paper investigates the influence of the fracture network parameters on the output and the optimal design of the explosive fracturing. It is shown that the permeability of the fracture network exerts a great influence on the production. In addition, this paper offers an optimal design for explosive fracturing. The results from this study are expected to be significantly helpful for the optimal design of explosive fracturing and provide a rational design about the explosive quantity in low permeable reservoirs.
The explosive fracturing technique is often adopted to produce and expand fractures due to its great shock waves, thus improving the low permeability of oil reservoirs. Based on the distribution characteristics of the explosive fracturing network and applying the Laplace transform and the Stehfest numerical inversion, this paper presents a new analytic mathematical production model for the complex-flow to an explosive fracturing well and obtains the formulas for the oil output under the constant pressure in different boundary conditions. On the basis of the model validation, this paper investigates the influence of the fracture network parameters on the output and the optimal design of the explosive fracturing. It is shown that the permeability of the fracture network exerts a great influence on the production. In addition, this paper offers an optimal design for explosive fracturing. The results from this study are expected to be significantly helpful for the optimal design of explosive fracturing and provide a rational design about the explosive quantity in low permeable reservoirs.
2016, 36(2): 230-235.
doi: 10.11883/1001-1455(2016)02-0230-06
Abstract:
The pressure history curves of aluminum fiber explosive and traditional aluminized explosives were measured by air blast experiments, and then the peak pressure, the secondary shock wave, the time of positive phase and the impulse were obtained by analyzing the curves. The result show that the peak pressure of the aluminum fiber explosive is not improved obviously with regard to the matrix explosives (RDX). The pressure decay rate of the aluminum fiber explosive is slower than that of RDX, resulting in that the time of the positive phase of the aluminum fiber explosive is longer than that of RDX. Compared with RDX, the impulse of the aluminum fiber explosive increases on the average by 18%, close to that of the traditional aluminized explosive. The amplitude and the occurrence of the secondary shock wave of the aluminum fiber explosive are the same as the traditional aluminized explosives and the secondary shock wave of aluminum fiber explosive occurs earlier than the matrix explosives (RDX), which shows that the amplitude and the occurrence time of the secondary shock wave are correlated with the types of explosive.
The pressure history curves of aluminum fiber explosive and traditional aluminized explosives were measured by air blast experiments, and then the peak pressure, the secondary shock wave, the time of positive phase and the impulse were obtained by analyzing the curves. The result show that the peak pressure of the aluminum fiber explosive is not improved obviously with regard to the matrix explosives (RDX). The pressure decay rate of the aluminum fiber explosive is slower than that of RDX, resulting in that the time of the positive phase of the aluminum fiber explosive is longer than that of RDX. Compared with RDX, the impulse of the aluminum fiber explosive increases on the average by 18%, close to that of the traditional aluminized explosive. The amplitude and the occurrence of the secondary shock wave of the aluminum fiber explosive are the same as the traditional aluminized explosives and the secondary shock wave of aluminum fiber explosive occurs earlier than the matrix explosives (RDX), which shows that the amplitude and the occurrence time of the secondary shock wave are correlated with the types of explosive.
2016, 36(2): 236-241.
doi: 10.11883/1001-1455(2016)02-0236-06
Abstract:
To evaluate the work capability of the aluminum fiber explosive, the field test of explosion cavity expansion in soil by aluminum fiber explosive was performed, and the numerical simulation analysis using the software of ANSYS/LS-DYNA was carried out for further investigation. The relationship between the radius of the explosion cavity and the explosive charge was obtained. Our results reveal that both of the two methods provide a fairly good characterization of the law of expansion during the explosion cavity process in soil of aluminum fiber explosive, and the characteristics the aluminum fiber explosive exhibit are better than those of the emulsion explosive in modelling and work ability, which offers a promising application when used in complicated environments and provides a reference for similar engineering projects.
To evaluate the work capability of the aluminum fiber explosive, the field test of explosion cavity expansion in soil by aluminum fiber explosive was performed, and the numerical simulation analysis using the software of ANSYS/LS-DYNA was carried out for further investigation. The relationship between the radius of the explosion cavity and the explosive charge was obtained. Our results reveal that both of the two methods provide a fairly good characterization of the law of expansion during the explosion cavity process in soil of aluminum fiber explosive, and the characteristics the aluminum fiber explosive exhibit are better than those of the emulsion explosive in modelling and work ability, which offers a promising application when used in complicated environments and provides a reference for similar engineering projects.
2016, 36(2): 242-247.
doi: 10.11883/1001-1455(2016)02-0242-06
Abstract:
In order to study the power capability of RDX-based PBX and determine the parameters of the JWL equation of state, the ∅50 mm standard cylinder test of RDX-based PBX and TNT were carried out, the expansion distance-time curve and velocity-time curve of the cylinder wall were obtained. Compared with the TNT, PBX had obviously a higher power capability. Based on the theory of energy conservation and the nonlinear fitting of the experimental data, the parameters of the JWL equation of state were obtained. Compared with the known software parameters and by numerical simulation of the cylinder test by AUTODYN, a fairly good agreement was reached between the experimental value and the actual test results, proving that this method for obtaining the JWL parameters is viable.
In order to study the power capability of RDX-based PBX and determine the parameters of the JWL equation of state, the ∅50 mm standard cylinder test of RDX-based PBX and TNT were carried out, the expansion distance-time curve and velocity-time curve of the cylinder wall were obtained. Compared with the TNT, PBX had obviously a higher power capability. Based on the theory of energy conservation and the nonlinear fitting of the experimental data, the parameters of the JWL equation of state were obtained. Compared with the known software parameters and by numerical simulation of the cylinder test by AUTODYN, a fairly good agreement was reached between the experimental value and the actual test results, proving that this method for obtaining the JWL parameters is viable.
2016, 36(2): 248-252.
doi: 10.11883/1001-1455(2016)02-0248-05
Abstract:
Aim to optimize the design of MEMS copper azide fuze and investgate the mechanism underlying the process of the copper azide explosive-driven flyer plate. According to the actual design of the micro-charge fuze and its related experiments, the process of the copper azide explosive-driven flyer plate was simulated adopting the fluid-solid coupling algorithm in LS-DYNA program. The influences of the barrel's length on the flyer's velocity and integrity were studied and the relationship between the micro-charge size and the flyer's velocity were discussed. Our research results indicate that the barrel's length has a major impact on the flyer's velocity and integrity. It is found that, when it is accelerated in a long barrel, the flyer is likely to be more fragile and cannot achieve maximal driving velocity. The size of the micro-charge is uniquely related with the flyer's velocity in that the flyer's maximum velocity is significantly affected by the charge's diameter. With the increase of the thickness of the charge, the average velocity and the maximal velocity were raised gradually. When the charge diameter is above 0.8 mm, its influence on the flyer's maximal velocity is not remarkable.
Aim to optimize the design of MEMS copper azide fuze and investgate the mechanism underlying the process of the copper azide explosive-driven flyer plate. According to the actual design of the micro-charge fuze and its related experiments, the process of the copper azide explosive-driven flyer plate was simulated adopting the fluid-solid coupling algorithm in LS-DYNA program. The influences of the barrel's length on the flyer's velocity and integrity were studied and the relationship between the micro-charge size and the flyer's velocity were discussed. Our research results indicate that the barrel's length has a major impact on the flyer's velocity and integrity. It is found that, when it is accelerated in a long barrel, the flyer is likely to be more fragile and cannot achieve maximal driving velocity. The size of the micro-charge is uniquely related with the flyer's velocity in that the flyer's maximum velocity is significantly affected by the charge's diameter. With the increase of the thickness of the charge, the average velocity and the maximal velocity were raised gradually. When the charge diameter is above 0.8 mm, its influence on the flyer's maximal velocity is not remarkable.
2016, 36(2): 253-258.
doi: 10.11883/1001-1455(2016)02-0253-06
Abstract:
To study the hexagonal honeycomb shelter's penetration-resistance performance, a series of experiments were done using a kind of projectile with a diameter of 15 mm. Compared with the steel reinforced concrete shelter, the penetration damage done to the honeycomb shelter occurs inside the hexagonal component element, the damaged area is relatively smaller, and the angle of the yaw in the honeycomb shelter is larger than the one found in the steel reinforced concrete shelter. Analyzing the experimental results based on the theory of the stress wave propagation, we studied the mechanism of the shelter's strength enhancement and found that, due to the steel pipe's restriction and countercheck, the compressive strength of the concrete and the resistance of the projectile were amplified in the process of the projectile's penetration, thus reducing the projectile's damaging effect on the honeycomb shelter.
To study the hexagonal honeycomb shelter's penetration-resistance performance, a series of experiments were done using a kind of projectile with a diameter of 15 mm. Compared with the steel reinforced concrete shelter, the penetration damage done to the honeycomb shelter occurs inside the hexagonal component element, the damaged area is relatively smaller, and the angle of the yaw in the honeycomb shelter is larger than the one found in the steel reinforced concrete shelter. Analyzing the experimental results based on the theory of the stress wave propagation, we studied the mechanism of the shelter's strength enhancement and found that, due to the steel pipe's restriction and countercheck, the compressive strength of the concrete and the resistance of the projectile were amplified in the process of the projectile's penetration, thus reducing the projectile's damaging effect on the honeycomb shelter.
2016, 36(2): 259-268.
doi: 10.11883/1001-1455(2016)02-0259-10
Abstract:
The pyroshock environment of satellite-rocket separation is the severest mechanical environment during launching, which is characterized by transient high acceleration and high frequency. While it does not necessarily cause a satellite any structural damage, pyroshock may incur most serious damages on a satellite's precision electronic equipments containing crystals and brittle materials, resulting in either the failure of the entire mission or even catastrophic accidents. Therefore, during the development of a new spacecraft, an accurate prediction of the pyroshock environment and a reasonable specification and determination for components are essential. In this paper, a research review of ground simulation test methods and the pyroshock response prediction is presented, and the technological gap between China and countries highly developed in field is pointed out. In addition to that, according to the requirements of China's domestic space engineering, the main research directions in the pyroshock are proposed.
The pyroshock environment of satellite-rocket separation is the severest mechanical environment during launching, which is characterized by transient high acceleration and high frequency. While it does not necessarily cause a satellite any structural damage, pyroshock may incur most serious damages on a satellite's precision electronic equipments containing crystals and brittle materials, resulting in either the failure of the entire mission or even catastrophic accidents. Therefore, during the development of a new spacecraft, an accurate prediction of the pyroshock environment and a reasonable specification and determination for components are essential. In this paper, a research review of ground simulation test methods and the pyroshock response prediction is presented, and the technological gap between China and countries highly developed in field is pointed out. In addition to that, according to the requirements of China's domestic space engineering, the main research directions in the pyroshock are proposed.
2016, 36(2): 269-278.
doi: 10.11883/1001-1455(2016)02-0269-10
Abstract:
Studies on buildings and structures subjected to aircraft impact have been of greater concern, because malicious aircraft crash is one of the major means adopted in terrorist attacks due to the disastrous consequences and extremely bad influences involved. As the aircraft impact is related with multiple scientific issues, in this paper, the latest developments in the study of buildings and structures subjected to aircraft impact at home and aboard are summarized from three respects covered by test study, theoretical analysis, and numerical simulation, with special focus on difficulties and problems in research as well as the future research direction and trend, including firstly the system research and validation for scale model test, secondly the impact force model and local damage calculation formulas research, thirdly the establishment of the refined model of aircraft, buildings and structures, fourthly the vibration characteristics of buildings and structures subjected to aircraft impact, fifthly the coupling damage effect of impact load and fire load, and finally the comparative analysis of results calculated by the general model and the refined model, decoupling and coupling method, and various numerical simulation programs.
Studies on buildings and structures subjected to aircraft impact have been of greater concern, because malicious aircraft crash is one of the major means adopted in terrorist attacks due to the disastrous consequences and extremely bad influences involved. As the aircraft impact is related with multiple scientific issues, in this paper, the latest developments in the study of buildings and structures subjected to aircraft impact at home and aboard are summarized from three respects covered by test study, theoretical analysis, and numerical simulation, with special focus on difficulties and problems in research as well as the future research direction and trend, including firstly the system research and validation for scale model test, secondly the impact force model and local damage calculation formulas research, thirdly the establishment of the refined model of aircraft, buildings and structures, fourthly the vibration characteristics of buildings and structures subjected to aircraft impact, fifthly the coupling damage effect of impact load and fire load, and finally the comparative analysis of results calculated by the general model and the refined model, decoupling and coupling method, and various numerical simulation programs.
2016, 36(2): 279-284.
doi: 10.11883/1001-1455(2016)02-0279-06
Abstract:
In order to investigate the influence of polyester fiber on impact characteristics of permeable asphalt concrete, ∅74 mm steel SHPB apparatus is adopted to conduct impact compressive test with various strain rates and different polyester fiber contents. The results of specimens under static condition and dynamic conditions with four strain rates show that the permeable polyester fiber asphalt concrete is a material sensitive to the change of the strain rate and exhibits a significant strain rate effect. It has good ductility and dynamic stress-strain curve that is characterized by three stages: Elastic deformation, plastic deformation and failure. When the strain rate remains the same, the impact compressive strength of permeable asphalt concrete first increases and then declines with the increase of the polyester fiber content. At this time it shows an optimum polyester fiber content of 0.40% and its impact compressive strength reaches its maximum. The impact compressive strength is about 8-13 times as large as the static compressive strength.
In order to investigate the influence of polyester fiber on impact characteristics of permeable asphalt concrete, ∅74 mm steel SHPB apparatus is adopted to conduct impact compressive test with various strain rates and different polyester fiber contents. The results of specimens under static condition and dynamic conditions with four strain rates show that the permeable polyester fiber asphalt concrete is a material sensitive to the change of the strain rate and exhibits a significant strain rate effect. It has good ductility and dynamic stress-strain curve that is characterized by three stages: Elastic deformation, plastic deformation and failure. When the strain rate remains the same, the impact compressive strength of permeable asphalt concrete first increases and then declines with the increase of the polyester fiber content. At this time it shows an optimum polyester fiber content of 0.40% and its impact compressive strength reaches its maximum. The impact compressive strength is about 8-13 times as large as the static compressive strength.
2016, 36(2): 285-288.
doi: 10.11883/1001-1455(2016)02-0285-04
Abstract:
The quasi-static and dynamic compression behavior of beryllium was investigated by using MTS and SHPB at different temperatures. Investigated results show that beryllium exhibits excellent plasticity under compression. Sensitive to the changes in temperature and strain rate, the yield point and flow stress of beryllium have an marked tendency to increase with the increase of the strain rate, and to decrease gradually with the rise of temperatures. At the same time, the work hardening behavior of beryllium exhibits a piecewise hardening feature as the strain increases at room temperature, and tends to become smooth as the temperature rises. Finally, a modified Johnson-Cook constitutive model was developed to predict the deformation behavior of beryllium over a wide range of temperatures and strain rates. The calculation results of the model are in good agreement with those achieved from the experiment.
The quasi-static and dynamic compression behavior of beryllium was investigated by using MTS and SHPB at different temperatures. Investigated results show that beryllium exhibits excellent plasticity under compression. Sensitive to the changes in temperature and strain rate, the yield point and flow stress of beryllium have an marked tendency to increase with the increase of the strain rate, and to decrease gradually with the rise of temperatures. At the same time, the work hardening behavior of beryllium exhibits a piecewise hardening feature as the strain increases at room temperature, and tends to become smooth as the temperature rises. Finally, a modified Johnson-Cook constitutive model was developed to predict the deformation behavior of beryllium over a wide range of temperatures and strain rates. The calculation results of the model are in good agreement with those achieved from the experiment.
