2018 Vol. 38, No. 6
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2018, 38(6): 1181-1188.
doi: 10.11883/bzycj-2018-0014
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In order to achieve the time-history curves of chamber pressure conveniently and efficiently at the lab-scale and further to investigate the damage patterns of typical structures and materials during transient high pressure in the chamber, a chamber pressure simulator with an exhaust element to discharge the gas generated due to the propellant combustion in the vessel was developed. A mathematical model which describes the working principle of the simulator was derived according to the propellant combustion theory and the isentropic flow model. The mass flow rate during the depressurization procedure was attained using the software Fluent on the basis of the ideal gas hypothesis, which was compared to theoretical results to determine the discharge coefficient. The performance parameters of the simulator were designed optimally based on the characteristics of time-history curves of chamber pressure for 76 mm and 155 mm guns and the miniaturization design principle. Optimization results show that pressurization and depressurization rates are satisfactory, the peak pressure is about 300 MPa and the duration when the pressure is higher than 30 MPa is longer than 10 ms. Results of verification tests present good repeatability and are coincident with theoretical results, which indicates that the simulator works with high reliability. It is feasible to simulate time-history curves of chamber pressure through exhausting propellant gas directly.
In order to achieve the time-history curves of chamber pressure conveniently and efficiently at the lab-scale and further to investigate the damage patterns of typical structures and materials during transient high pressure in the chamber, a chamber pressure simulator with an exhaust element to discharge the gas generated due to the propellant combustion in the vessel was developed. A mathematical model which describes the working principle of the simulator was derived according to the propellant combustion theory and the isentropic flow model. The mass flow rate during the depressurization procedure was attained using the software Fluent on the basis of the ideal gas hypothesis, which was compared to theoretical results to determine the discharge coefficient. The performance parameters of the simulator were designed optimally based on the characteristics of time-history curves of chamber pressure for 76 mm and 155 mm guns and the miniaturization design principle. Optimization results show that pressurization and depressurization rates are satisfactory, the peak pressure is about 300 MPa and the duration when the pressure is higher than 30 MPa is longer than 10 ms. Results of verification tests present good repeatability and are coincident with theoretical results, which indicates that the simulator works with high reliability. It is feasible to simulate time-history curves of chamber pressure through exhausting propellant gas directly.
2018, 38(6): 1189-1199.
doi: 10.11883/bzycj-2018-0115
Abstract:
Experimental studies of the vertical water entry of projectile with 90° cone-shaped head were conducted by using high speed camera. The pinch-off types and evolutionary process of the cavity were comprehensively discussed at different water entry impact velocities. The variations of cavitation closure time, water depth at the closure point and length of the warhead cavitation with water entry velocities, as well as the cavitation diameter at different water depth positions were analyzed. The jet phenomenon caused by the closure of the water curtain and contraction-rising process of the cavity near undisturbed free surface were studied, as well as the coupled effect between them. The cavity wall fluctuation occurring after the deep seal was discussed. The results show that with the increase of water entry velocity, the quasi-static closure, shallow closure, deep closure and surface closure of the cavitation occurs respectively, and each closure mode corresponds to a velocity range; the critical water entry velocity of forming cavitation is 0.657 m/s. The diameter of the cavitation presents a nonlinear increase along with the water depth. The initial cavity expansion velocity increases, the maximum diameter of the cavity decreases, the expansion section shortens, the contraction section lengthens, and the acceleration of the expansion and contraction of the cavity increases along with the increase of the water depth at the same time. When the water curtain closes, there will be upward and downward jets, and when the downward jet velocity is relatively large, the projectile motion will be affected. The strength of a water jet induced by longitudinal upward contraction of the cavity near free surface is proportional to the volume of cavity and pinch-off depth. A large strength upward water jet is induced by the coupling of the above all water jet. The longitudinal contraction of the cavity around the projectile and the impact effect of downward jet on projectile would cause the force change of the projectile after deep seal. The fluctuation of the projectile's velocity because of its force change brings the velocity change of fluid and then leads to the fluctuation of the cavity wall. The fluctuation of cavity wall follows the principle of independent expansion of cavitation section.
Experimental studies of the vertical water entry of projectile with 90° cone-shaped head were conducted by using high speed camera. The pinch-off types and evolutionary process of the cavity were comprehensively discussed at different water entry impact velocities. The variations of cavitation closure time, water depth at the closure point and length of the warhead cavitation with water entry velocities, as well as the cavitation diameter at different water depth positions were analyzed. The jet phenomenon caused by the closure of the water curtain and contraction-rising process of the cavity near undisturbed free surface were studied, as well as the coupled effect between them. The cavity wall fluctuation occurring after the deep seal was discussed. The results show that with the increase of water entry velocity, the quasi-static closure, shallow closure, deep closure and surface closure of the cavitation occurs respectively, and each closure mode corresponds to a velocity range; the critical water entry velocity of forming cavitation is 0.657 m/s. The diameter of the cavitation presents a nonlinear increase along with the water depth. The initial cavity expansion velocity increases, the maximum diameter of the cavity decreases, the expansion section shortens, the contraction section lengthens, and the acceleration of the expansion and contraction of the cavity increases along with the increase of the water depth at the same time. When the water curtain closes, there will be upward and downward jets, and when the downward jet velocity is relatively large, the projectile motion will be affected. The strength of a water jet induced by longitudinal upward contraction of the cavity near free surface is proportional to the volume of cavity and pinch-off depth. A large strength upward water jet is induced by the coupling of the above all water jet. The longitudinal contraction of the cavity around the projectile and the impact effect of downward jet on projectile would cause the force change of the projectile after deep seal. The fluctuation of the projectile's velocity because of its force change brings the velocity change of fluid and then leads to the fluctuation of the cavity wall. The fluctuation of cavity wall follows the principle of independent expansion of cavitation section.
2018, 38(6): 1200-1217.
doi: 10.11883/bzycj-2018-0173
Abstract:
The hypervelocity kinetic energy weapon that strikes the ground at the speed from 5 Mach to 15 Mach has some unique characteristics of penetration mechanism and damage effects, which cannot be accurately described by ths existing theories.In this paper, the dynamic compressibility behavior of rock, penetration and explosion effects in the near zone is systematically summarized.It is found that the actual stress in the rock impacted under velocity of 5 Mach to 15 Mach is between fluid state and elasto-plasticity state.A theoretical model of hydro-elastoplastic-frictional penetration model is proposed, which fills the gap of stress state between elastic-plastic state and hydro-dynamic state.For the first time, the impedance formula is obtained, which can describe the stress state of whole interaction process between target and projectile.The minimum kinetic energy threshold of solid penetration, pseudofluid penetration and fluid penetration is defined.The methods for calculating hypervelocity impact effects including penetration depth, crater radius and the safety thickness of protective layer are proposed in the paper.In addition, the accuracy of the theoretical formula is verified by a series of penetration tests with the impact speed from 1 100 m/s to 4 200 m/s.
The hypervelocity kinetic energy weapon that strikes the ground at the speed from 5 Mach to 15 Mach has some unique characteristics of penetration mechanism and damage effects, which cannot be accurately described by ths existing theories.In this paper, the dynamic compressibility behavior of rock, penetration and explosion effects in the near zone is systematically summarized.It is found that the actual stress in the rock impacted under velocity of 5 Mach to 15 Mach is between fluid state and elasto-plasticity state.A theoretical model of hydro-elastoplastic-frictional penetration model is proposed, which fills the gap of stress state between elastic-plastic state and hydro-dynamic state.For the first time, the impedance formula is obtained, which can describe the stress state of whole interaction process between target and projectile.The minimum kinetic energy threshold of solid penetration, pseudofluid penetration and fluid penetration is defined.The methods for calculating hypervelocity impact effects including penetration depth, crater radius and the safety thickness of protective layer are proposed in the paper.In addition, the accuracy of the theoretical formula is verified by a series of penetration tests with the impact speed from 1 100 m/s to 4 200 m/s.
2018, 38(6): 1218-1230.
doi: 10.11883/bzycj-2017-0122
Abstract:
Expanding the advantages of flattened ring geometry, a new test specimen geometry with a longer fracture path was advised to investigate the complete dynamic fracture process.This geometry was cracked eccentrically holed flattened disc (CEHFD) which was more conducive to study the unstable dynamic crack propagation and dynamic crack arrest.In order to study the mode Ⅰ (opening mode) dynamic fracture process of a rock, CEHFD specimens with strain gauges and crack propagation gauge glued on the specimen's surface were diametrically impacted by a split Hopkinson pressure bar.The experiment investigated crack initiation, rapid crack propagation, and crack arrest, all in one specimen.In a single complete fracture event, the crack accelerated after initiating and decelerated before arresting.The process monitored by the laboratory is completely consistent with the whole process of the dynamic rupture of faults in earthquake.A hybrid experimental-numerical-analytical method was used to determine the dynamic stress intensity factor that increased with increasing time.The dynamic fracture toughness was obtained with the fracture time information.Crack propagation velocity was first increased and then decreased with the time, and the dynamic propagation toughness had the same variation tendency with time as it was the function of velocity.The dynamic arrest toughness was smaller than the dynamic initiation toughness, and decreased when the maximum crack propagation speed increased.
Expanding the advantages of flattened ring geometry, a new test specimen geometry with a longer fracture path was advised to investigate the complete dynamic fracture process.This geometry was cracked eccentrically holed flattened disc (CEHFD) which was more conducive to study the unstable dynamic crack propagation and dynamic crack arrest.In order to study the mode Ⅰ (opening mode) dynamic fracture process of a rock, CEHFD specimens with strain gauges and crack propagation gauge glued on the specimen's surface were diametrically impacted by a split Hopkinson pressure bar.The experiment investigated crack initiation, rapid crack propagation, and crack arrest, all in one specimen.In a single complete fracture event, the crack accelerated after initiating and decelerated before arresting.The process monitored by the laboratory is completely consistent with the whole process of the dynamic rupture of faults in earthquake.A hybrid experimental-numerical-analytical method was used to determine the dynamic stress intensity factor that increased with increasing time.The dynamic fracture toughness was obtained with the fracture time information.Crack propagation velocity was first increased and then decreased with the time, and the dynamic propagation toughness had the same variation tendency with time as it was the function of velocity.The dynamic arrest toughness was smaller than the dynamic initiation toughness, and decreased when the maximum crack propagation speed increased.
2018, 38(6): 1231-1240.
doi: 10.11883/bzycj-2017-0413
Abstract:
To achieve excellent penetration performance with high-quality utilization ratio, the symmetrical grooved-nose projectile is proposed between the ogive-nose projectile and conical-nose projectile.Aiming to provide insight into the penetration performance of symmetrical grooved-nose projectile, comparative penetration tests are conducted from moderate to low velocities.Based on the experimental study, the localized interaction model for symmetrical grooved-nose projectile penetrating into semi-infinite aluminum target is derived.Combined with the phenomenon of target damage, the normal stresses acting on the localized surface of the symmetrical grooved-nose are proposed and then the penetration depth of symmetrical grooved-nose projectile can be calculated.The results of experiment and theoretical model prove that the symmetrical grooved-nose projectile has a more excellent penetration performance than the ogive-nose projectile.The reasons of increasing penetration depth for symmetrical grooved-nose projectile are the increasement of specific kinetic energy of cross section of the projectile head and the target weakening effect during penetration, and the decisive factor is the target weakening effect.
To achieve excellent penetration performance with high-quality utilization ratio, the symmetrical grooved-nose projectile is proposed between the ogive-nose projectile and conical-nose projectile.Aiming to provide insight into the penetration performance of symmetrical grooved-nose projectile, comparative penetration tests are conducted from moderate to low velocities.Based on the experimental study, the localized interaction model for symmetrical grooved-nose projectile penetrating into semi-infinite aluminum target is derived.Combined with the phenomenon of target damage, the normal stresses acting on the localized surface of the symmetrical grooved-nose are proposed and then the penetration depth of symmetrical grooved-nose projectile can be calculated.The results of experiment and theoretical model prove that the symmetrical grooved-nose projectile has a more excellent penetration performance than the ogive-nose projectile.The reasons of increasing penetration depth for symmetrical grooved-nose projectile are the increasement of specific kinetic energy of cross section of the projectile head and the target weakening effect during penetration, and the decisive factor is the target weakening effect.
2018, 38(6): 1241-1246.
doi: 10.11883/bzycj-2017-0154
Abstract:
Non-linear dynamical finite element software AUTODYN was used to simulate the shock initiation of steel-covered charge impacted by high-velocity fragments. The interlayer effect was studied based on the pressure history of initiation when different materials and thickness interlayers were used. The results show that the interlayer material is an important factor affecting pressure history and run-to-detonation of explosives, the thickness of interlayer has the same effects. The initiation of explosives can be effectively prevented with changing the thickness and material of the interlayer.
Non-linear dynamical finite element software AUTODYN was used to simulate the shock initiation of steel-covered charge impacted by high-velocity fragments. The interlayer effect was studied based on the pressure history of initiation when different materials and thickness interlayers were used. The results show that the interlayer material is an important factor affecting pressure history and run-to-detonation of explosives, the thickness of interlayer has the same effects. The initiation of explosives can be effectively prevented with changing the thickness and material of the interlayer.
2018, 38(6): 1247-1254.
doi: 10.11883/bzycj-2017-0132
Abstract:
In this work, we proposed a specimen with a new configuration specimen, i.e.double inclined bottom central cracked specimen (DIBCC) to explore a more suitable configuration specimen for the study of the behavior of Mode Ⅰ crack under impacts, by conducting tests using a middle-low speed drop hammer impact test device, and by driving the initiation and propagation of the prefabricated crack inside the DIBCC specimens using stress waves.Meanwhile, we measured the crack initiation time using a strain gauge test system and carried out the corresponding numerical simulation using the AUTODYN finite difference code.Then we calculated the dynamic stress intensity factors and determined the initiation toughness of the specimens using the initiation time measured from the experiments.The results show that, under the action of the reflected tensile waves, the prefabricated crack surfaces have outward displacements perpendicular to the crack surface, making the prefabricated crack expand and thus induce the crack to initiate, and that the numerical result of the crack propagation path agrees well with the test result, indicating that the DIBCC configuration specimen proposed is effective and can be used to test the fracture toughness under impacts.
In this work, we proposed a specimen with a new configuration specimen, i.e.double inclined bottom central cracked specimen (DIBCC) to explore a more suitable configuration specimen for the study of the behavior of Mode Ⅰ crack under impacts, by conducting tests using a middle-low speed drop hammer impact test device, and by driving the initiation and propagation of the prefabricated crack inside the DIBCC specimens using stress waves.Meanwhile, we measured the crack initiation time using a strain gauge test system and carried out the corresponding numerical simulation using the AUTODYN finite difference code.Then we calculated the dynamic stress intensity factors and determined the initiation toughness of the specimens using the initiation time measured from the experiments.The results show that, under the action of the reflected tensile waves, the prefabricated crack surfaces have outward displacements perpendicular to the crack surface, making the prefabricated crack expand and thus induce the crack to initiate, and that the numerical result of the crack propagation path agrees well with the test result, indicating that the DIBCC configuration specimen proposed is effective and can be used to test the fracture toughness under impacts.
2018, 38(6): 1255-1261.
doi: 10.11883/bzycj-2017-0219
Abstract:
In this study, using a split Hopkinson pressure bar (SHPB), we assembled a fast-responding infrared temperature measurement system, capable of simultaneously obtaining the superficial temperature change of the HTPB propellant in impact experiments, to investigate the energy dissipation pattern of HTPB propellant under impact loading. The results show that the HTPB propellant exhibited visco-hyper elastic properties, and experienced significant temperature rise in high speed deformation. Based on the visco-hyper elastic constitutive model, we also introduced a heat softening function to more accurately describe the thermodynamic response of the HTPB propellant at high strain rates. Our results provide support for the analysis of thermo mechanical coupling of the solid composite propellant under impact loading.
In this study, using a split Hopkinson pressure bar (SHPB), we assembled a fast-responding infrared temperature measurement system, capable of simultaneously obtaining the superficial temperature change of the HTPB propellant in impact experiments, to investigate the energy dissipation pattern of HTPB propellant under impact loading. The results show that the HTPB propellant exhibited visco-hyper elastic properties, and experienced significant temperature rise in high speed deformation. Based on the visco-hyper elastic constitutive model, we also introduced a heat softening function to more accurately describe the thermodynamic response of the HTPB propellant at high strain rates. Our results provide support for the analysis of thermo mechanical coupling of the solid composite propellant under impact loading.
2018, 38(6): 1262-1270.
doi: 10.11883/bzycj-2017-0179
Abstract:
This paper conducted 11 split Hopkinson pressure bar (SHPB) tests on the calcareous sand sampled from a calcareous reef in China and silica sand sampled from Fujian Provence of China. The relative density is 90%. The strain-rate history, strain history, and stress-strain curves were obtained for sand specimens with three thicknesses including 10 mm, 30 mm and 50 mm. It is found that test error can be reduced by standard procedure in sand preparation. The stress equilibrium and constant strain rate can be achieved by changing the thickness of specimen, the length of striker and the pulse shaper. With an identical relative density and loading condition, the volumetric modulus and shear modulus of calcareous sand is approximately 10% of the silica sand; and the strength of the calcareous sand is approximately 30% of the silica sand. Therefore, the results of existing silica sand can not be directly applied to calcareous sand because of their large discrepancies.
This paper conducted 11 split Hopkinson pressure bar (SHPB) tests on the calcareous sand sampled from a calcareous reef in China and silica sand sampled from Fujian Provence of China. The relative density is 90%. The strain-rate history, strain history, and stress-strain curves were obtained for sand specimens with three thicknesses including 10 mm, 30 mm and 50 mm. It is found that test error can be reduced by standard procedure in sand preparation. The stress equilibrium and constant strain rate can be achieved by changing the thickness of specimen, the length of striker and the pulse shaper. With an identical relative density and loading condition, the volumetric modulus and shear modulus of calcareous sand is approximately 10% of the silica sand; and the strength of the calcareous sand is approximately 30% of the silica sand. Therefore, the results of existing silica sand can not be directly applied to calcareous sand because of their large discrepancies.
2018, 38(6): 1271-1277.
doi: 10.11883/bzycj-2017-0201
Abstract:
Rock mass is a geological body with a complex hierarchical structure. Based on Sadovsky's concept of block hierarchy, and considering that there are two stable invariants of λ and μ△ existing in rock mass, a simplified analytical model is established to study the space-limited rotation and translation under the effect of blast shock waves. With the neglected conditions of Kocharyan's works in calculating scales of activated blocks, the calculation formula of irreversible deformation region radius under large-scale underground explosion is re-derived.
Rock mass is a geological body with a complex hierarchical structure. Based on Sadovsky's concept of block hierarchy, and considering that there are two stable invariants of λ and μ△ existing in rock mass, a simplified analytical model is established to study the space-limited rotation and translation under the effect of blast shock waves. With the neglected conditions of Kocharyan's works in calculating scales of activated blocks, the calculation formula of irreversible deformation region radius under large-scale underground explosion is re-derived.
2018, 38(6): 1278-1285.
doi: 10.11883/bzycj-2017-0210
Abstract:
In the present study, we performed theoretical calculation, numerical simulation and experimental test to investigate the ricochet performance of cylindrical fragments. The fragment, 5.7 mm in diameter and 6.7 mm in length, impacted aluminum plates 2-10 mm in thickness at speeds of 800-1 200 m/s. A theoretical model of the ricochet was established, the relation between the critical angle and the initial velocity and the thickness of the target plate were obtained. The results of theoretical calculation agreed well with both the simulation and experiment. The results show that the higher the impacting velocity, the larger the critical ricochet angle; and the thicker the target, the smaller the critical ricochet angle. When a fragment impacts a 2 mm target plate at 800-1 200 m/s, the critical ricochet angle is 81°-81.25°; when a fragment impacts a 4 mm target plate at 800-1 200 m/s, the critical ricochet angle is72.5°-76.25°.
In the present study, we performed theoretical calculation, numerical simulation and experimental test to investigate the ricochet performance of cylindrical fragments. The fragment, 5.7 mm in diameter and 6.7 mm in length, impacted aluminum plates 2-10 mm in thickness at speeds of 800-1 200 m/s. A theoretical model of the ricochet was established, the relation between the critical angle and the initial velocity and the thickness of the target plate were obtained. The results of theoretical calculation agreed well with both the simulation and experiment. The results show that the higher the impacting velocity, the larger the critical ricochet angle; and the thicker the target, the smaller the critical ricochet angle. When a fragment impacts a 2 mm target plate at 800-1 200 m/s, the critical ricochet angle is 81°-81.25°; when a fragment impacts a 4 mm target plate at 800-1 200 m/s, the critical ricochet angle is72.5°-76.25°.
2018, 38(6): 1286-1394.
doi: 10.11883/bzycj-2017-0215
Abstract:
WALE LES model coupled with Zimont premixed combustion model were applied to study the characteristics of the flame of gasoline-air mixture explosions. Results by LES simulation, RNG k-ε model and experiments were compared with each other, and the conclusions show that:(1) LES is more accurate than RNG k-ε turbulence model in predicting gasoline-air mixture explosion overpressure, flame propagation speed and the variation of flame shape, and it can show more refined structure of flow field; (2) The obstacles induce a turbulent flow field in the pipeline, which can cause the flame to produce wrinkle and bend deformation, increase the flame surface area and accelerate the flame propagation; (3) The explosion overpressure, the flame propagation speed and the flame surface area are closely related. They have significant coupling and show nearly the same changing tendency.
WALE LES model coupled with Zimont premixed combustion model were applied to study the characteristics of the flame of gasoline-air mixture explosions. Results by LES simulation, RNG k-ε model and experiments were compared with each other, and the conclusions show that:(1) LES is more accurate than RNG k-ε turbulence model in predicting gasoline-air mixture explosion overpressure, flame propagation speed and the variation of flame shape, and it can show more refined structure of flow field; (2) The obstacles induce a turbulent flow field in the pipeline, which can cause the flame to produce wrinkle and bend deformation, increase the flame surface area and accelerate the flame propagation; (3) The explosion overpressure, the flame propagation speed and the flame surface area are closely related. They have significant coupling and show nearly the same changing tendency.
2018, 38(6): 1295-1302.
doi: 10.11883/bzycj-2017-0197
Abstract:
In this work, to forestall the domino effects resulting from the container explosion that may lead to serious damages to equipments and devices in a chemical industry park impacted by explosion fragments, we obtained the penetrating morphology, penetration energy and perforation diameter, of small-size tanks with different wall thicknesses that were impacted by conical projectiles at different axial impact angles, with the following results achieved:that the front penetrating morphology is nearly circular when the axial impact angle is 0°, and is nearly oval with two flangings when the axial impact angle is 15°, 30°, and 45°; that their backs are both dehiscent like petals; the larger the axial impact angle and tank wall thickness, the more penetration energy is needed; and that the axial impact angle and tank wall thickness have significant influence on the axial diameter of the perforation, but barely affect the circumferential diameter of the perforation. Also, based on the mechanics of perforation and the laws of conservation of momentum, we derived the residual velocity formula of conical projectiles suitable for axial impact angles ranging from 0 to 45 degrees.
In this work, to forestall the domino effects resulting from the container explosion that may lead to serious damages to equipments and devices in a chemical industry park impacted by explosion fragments, we obtained the penetrating morphology, penetration energy and perforation diameter, of small-size tanks with different wall thicknesses that were impacted by conical projectiles at different axial impact angles, with the following results achieved:that the front penetrating morphology is nearly circular when the axial impact angle is 0°, and is nearly oval with two flangings when the axial impact angle is 15°, 30°, and 45°; that their backs are both dehiscent like petals; the larger the axial impact angle and tank wall thickness, the more penetration energy is needed; and that the axial impact angle and tank wall thickness have significant influence on the axial diameter of the perforation, but barely affect the circumferential diameter of the perforation. Also, based on the mechanics of perforation and the laws of conservation of momentum, we derived the residual velocity formula of conical projectiles suitable for axial impact angles ranging from 0 to 45 degrees.
2018, 38(6): 1303-1309.
doi: 10.11883/bzycj-2017-0185
Abstract:
Via self-designed detonation tube, the detonation characteristics of hydrocarbon fuels were studied, and the conditions of low temperature and vacuum were considered. After systematic experiments, the relationship between detonation characteristics and ambient conditions were obtained and compared with that of normal condition. The results showed that the influence of the initial pressure played a more important role than the initial temperature, and when the initial pressure decreased to half of the barometric pressure, the detonation of hydrocarbon fuel was in critical condition. The achievements will be a complement and support the prediction of weapon performance for fuel-air explosives.
Via self-designed detonation tube, the detonation characteristics of hydrocarbon fuels were studied, and the conditions of low temperature and vacuum were considered. After systematic experiments, the relationship between detonation characteristics and ambient conditions were obtained and compared with that of normal condition. The results showed that the influence of the initial pressure played a more important role than the initial temperature, and when the initial pressure decreased to half of the barometric pressure, the detonation of hydrocarbon fuel was in critical condition. The achievements will be a complement and support the prediction of weapon performance for fuel-air explosives.
2018, 38(6): 1310-1316.
doi: 10.11883/bzycj-2018-0049
Abstract:
Based on the Hopkinson pressure bar and digital image correlation (DIC) techniques, a new Lagrangian inverse analysis experimental method was proposed to study the dynamic constitutive relation of brittle materials. A series of speckle images of long specimen deformation were recorded by an ultra-high-speed camera. The speckle images were processed by DIC to derive the velocity fields and strain fields on the surface of a long specimen. Based on the multi-particles velocity history curves measured by DIC, the whole velocity fields were constructed by many path lines. Then, a Lagrangian inverse analysis method was established for the dynamic constitutive relation of brittle rate-dependent PMMA materials by numerical solution. The results were compared with those of Hopkinson pressure bar test and quasi-static compression test, which display the characteristics of viscoelastic constitutive response of PMMA under the condition of small strain.
Based on the Hopkinson pressure bar and digital image correlation (DIC) techniques, a new Lagrangian inverse analysis experimental method was proposed to study the dynamic constitutive relation of brittle materials. A series of speckle images of long specimen deformation were recorded by an ultra-high-speed camera. The speckle images were processed by DIC to derive the velocity fields and strain fields on the surface of a long specimen. Based on the multi-particles velocity history curves measured by DIC, the whole velocity fields were constructed by many path lines. Then, a Lagrangian inverse analysis method was established for the dynamic constitutive relation of brittle rate-dependent PMMA materials by numerical solution. The results were compared with those of Hopkinson pressure bar test and quasi-static compression test, which display the characteristics of viscoelastic constitutive response of PMMA under the condition of small strain.
2018, 38(6): 1317-1324.
doi: 10.11883/bzycj-2017-0181
Abstract:
In this study, based on SPH and using AUTODYN-2D, we analyzed the hyper velocity penetration of tungsten rod into four types of layered shielding structures consisting of granite shielding layer, air/sand distribution layer and concrete structure layer, and obtained the structures' damage and energy distribution, with the following results achieved:(1) Although raising the striking velocity increased the damage of the shielding layer and the distributing layer, the penetration depth into the structure layer decreased within a certain velocity range; (2) The ratio of the energy conducted to the structure layer generally decreased with increasing of the striking velocity, and this could be attributed to the transverse propagation of the impact energy within the shielding layer and distributing layer; (3) Under certain conditions, addition of an air layer could reduce the penetration depth into the structure layer, the ratio and absolute value of the energy conducted to the structure layer.
In this study, based on SPH and using AUTODYN-2D, we analyzed the hyper velocity penetration of tungsten rod into four types of layered shielding structures consisting of granite shielding layer, air/sand distribution layer and concrete structure layer, and obtained the structures' damage and energy distribution, with the following results achieved:(1) Although raising the striking velocity increased the damage of the shielding layer and the distributing layer, the penetration depth into the structure layer decreased within a certain velocity range; (2) The ratio of the energy conducted to the structure layer generally decreased with increasing of the striking velocity, and this could be attributed to the transverse propagation of the impact energy within the shielding layer and distributing layer; (3) Under certain conditions, addition of an air layer could reduce the penetration depth into the structure layer, the ratio and absolute value of the energy conducted to the structure layer.
2018, 38(6): 1325-1332.
doi: 10.11883/bzycj-2017-0163
Abstract:
In this paper, we conducted quasi-static and dynamic tensile tests on Q235 steel at different temperatures using the Instron tensile strength tester and the split Hopkinson bar and studied the effects of temperature, strain rates and stress triaxiality on the steel's failure strains of Q235. The results show that Q235 steel's failure strains increase with a rise in temperature but decrease with a rise the strain rates while, with a rise in the stress triaxiality, they decrease at first but then increase. Based on these results and combining them with numerical simulation, we modified the item of temperature effects and proposed a revised three-section failure criterion of stress triaxiality for J-C failure model, with relevant parameters determined and verified using Taylor impacting experiments and corresponding numerical simulations. The experimental results accord well with those from simulation.
In this paper, we conducted quasi-static and dynamic tensile tests on Q235 steel at different temperatures using the Instron tensile strength tester and the split Hopkinson bar and studied the effects of temperature, strain rates and stress triaxiality on the steel's failure strains of Q235. The results show that Q235 steel's failure strains increase with a rise in temperature but decrease with a rise the strain rates while, with a rise in the stress triaxiality, they decrease at first but then increase. Based on these results and combining them with numerical simulation, we modified the item of temperature effects and proposed a revised three-section failure criterion of stress triaxiality for J-C failure model, with relevant parameters determined and verified using Taylor impacting experiments and corresponding numerical simulations. The experimental results accord well with those from simulation.
2018, 38(6): 1333-1343.
doi: 10.11883/bzycj-2017-0144
Abstract:
Aiming at solving the difficult problem of simulating the ejection crater and loose bulging under underground explosion, a method of vacuum chamber for simulating underground explosion effects is presented based on the similarity theory, and a testing apparatus is developed. The core assemblies of this apparatus consist of pressure vessel, fast-open door enclosed mechanism, explosive source simulation system with accurate burst control, vacuum pump air-removal system and instrumentation system. This set of apparatus could model the underground explosions with the equivalent of 0.1-100 kt TNT and the buried depth of 20-400 m, and it also could simulate the large-scale explosions with different charge schemes under complicated geological conditions. The typical modeling experimental results show that the apparatus is accurately adjusted and technically controllable, and that the experimental results are reliable. The testing apparatus for large-scale underground cratering explosions could provide assistances for both the damage effect analysis of the ejection explosions subject to earth-penetrating nuclear weapons and the prediction and forecast of the large-scale engineering blasting, and fill the shot of centrifuge cratering experiment which cannot model the large-scale underground explosions.
Aiming at solving the difficult problem of simulating the ejection crater and loose bulging under underground explosion, a method of vacuum chamber for simulating underground explosion effects is presented based on the similarity theory, and a testing apparatus is developed. The core assemblies of this apparatus consist of pressure vessel, fast-open door enclosed mechanism, explosive source simulation system with accurate burst control, vacuum pump air-removal system and instrumentation system. This set of apparatus could model the underground explosions with the equivalent of 0.1-100 kt TNT and the buried depth of 20-400 m, and it also could simulate the large-scale explosions with different charge schemes under complicated geological conditions. The typical modeling experimental results show that the apparatus is accurately adjusted and technically controllable, and that the experimental results are reliable. The testing apparatus for large-scale underground cratering explosions could provide assistances for both the damage effect analysis of the ejection explosions subject to earth-penetrating nuclear weapons and the prediction and forecast of the large-scale engineering blasting, and fill the shot of centrifuge cratering experiment which cannot model the large-scale underground explosions.
2018, 38(6): 1344-1352.
doi: 10.11883/bzycj-2017-0142
Abstract:
In order to study the scattering problems of SH-wave by elliptical inclusion with partial debond curve and circular cavity in half space. The method of "conformal mapping" is used to map the elliptical inclusions into circular inclusions. The displacement field and the stress field of the elliptical inclusion and circular cavity are obtained by Green's function method with the ridding of image method. Secondly, infinite system of linear equations are established by boundary conditions, which are continuous around the elliptical inclusion with the displacement and stress, and then the unknown coefficients of wave function are solved by the free around circular cavity with stress. Finally, the "partial debond curve model" is constructed, the equal stress with opposite direction is applied in the partial debond curve. By which we obtain the total displacement field of the elliptical inclusion with a partially debond curve and circular in the half space. Numerical examples show that the dynamic stress concentration factor (DSCF) is influenced by the incident angle, the frequency of incident wave, the distance of the defect, the depth of inclusion and the partial debond curve angle.
In order to study the scattering problems of SH-wave by elliptical inclusion with partial debond curve and circular cavity in half space. The method of "conformal mapping" is used to map the elliptical inclusions into circular inclusions. The displacement field and the stress field of the elliptical inclusion and circular cavity are obtained by Green's function method with the ridding of image method. Secondly, infinite system of linear equations are established by boundary conditions, which are continuous around the elliptical inclusion with the displacement and stress, and then the unknown coefficients of wave function are solved by the free around circular cavity with stress. Finally, the "partial debond curve model" is constructed, the equal stress with opposite direction is applied in the partial debond curve. By which we obtain the total displacement field of the elliptical inclusion with a partially debond curve and circular in the half space. Numerical examples show that the dynamic stress concentration factor (DSCF) is influenced by the incident angle, the frequency of incident wave, the distance of the defect, the depth of inclusion and the partial debond curve angle.
2018, 38(6): 1353-1363.
doi: 10.11883/bzycj-2017-0131
Abstract:
Dynamic experiments on skarn were conducted with a modified one-dimensional coupled static and dynamic loads based on SHPB device. The variations of dynamic deformation modulus of skarn under different axial pressures and frequent dynamic disturbance are studied when confining pressure was unloaded at the 1 MPa/s rate to 50% of initial value. The results show that high axial pressure promotes the formation and propagation of microcracks in rocks and reduces the resisting ability under external shocks. The lateral restraint of confining pressure hinders the transverse propagation of cracks inside the rock, but it will aggravate the damage when confining pressure is unloaded. This is because, under high axial pressure, unloading of confining pressure results in redistribution of stress inside rock. The axial pressure and confining unloading pressure affect the dynamic deformation modulus of rock under impact. Base on the variation analysis of dynamic deformation modulus by the energy dissipation of rock under impact, some significant understanding of deep rock excavation failure mechanism are drawn.
Dynamic experiments on skarn were conducted with a modified one-dimensional coupled static and dynamic loads based on SHPB device. The variations of dynamic deformation modulus of skarn under different axial pressures and frequent dynamic disturbance are studied when confining pressure was unloaded at the 1 MPa/s rate to 50% of initial value. The results show that high axial pressure promotes the formation and propagation of microcracks in rocks and reduces the resisting ability under external shocks. The lateral restraint of confining pressure hinders the transverse propagation of cracks inside the rock, but it will aggravate the damage when confining pressure is unloaded. This is because, under high axial pressure, unloading of confining pressure results in redistribution of stress inside rock. The axial pressure and confining unloading pressure affect the dynamic deformation modulus of rock under impact. Base on the variation analysis of dynamic deformation modulus by the energy dissipation of rock under impact, some significant understanding of deep rock excavation failure mechanism are drawn.
2018, 38(6): 1364-1371.
doi: 10.11883/bzycj-2017-0123
Abstract:
In order to study the penetration law of the mesoscale concrete target, The LS-DYNA software is used to simulate the penetration of rigid projectiles into two-phase concrete target. The results show that the main factors affecting the penetration resistance of the target are mortar type, coarse aggregate type and coarse aggregate volume fraction. The resistance of mortar in concrete target is close to the same part of mortar in mortar target. The resistance of coarse aggregate in concrete target is much lower than the same part of rock in rock target. By extending the Forrestal resistance equation, the penetration depth model of mesoscale concrete is established, which is in good agreement with the numerical simulation.
In order to study the penetration law of the mesoscale concrete target, The LS-DYNA software is used to simulate the penetration of rigid projectiles into two-phase concrete target. The results show that the main factors affecting the penetration resistance of the target are mortar type, coarse aggregate type and coarse aggregate volume fraction. The resistance of mortar in concrete target is close to the same part of mortar in mortar target. The resistance of coarse aggregate in concrete target is much lower than the same part of rock in rock target. By extending the Forrestal resistance equation, the penetration depth model of mesoscale concrete is established, which is in good agreement with the numerical simulation.
2018, 38(6): 1372-1377.
doi: 10.11883/bzycj-2017-0127
Abstract:
With the experimental study of underwater explosion for confined and unconfined in free field water, the characteristic parameters of explosion, such as the peak pressure of shock wave, the specific shock wave energy, the specific bubble energy, the total specific energy and the relative total energy of the explosives were compared and analyzed. The results showed that the peak pressure are, different for thermoplastic TNT-RDX-Al explosive, fusing TNT-RDX-Al explosive, composite PBX and TNT, Other parameters are, composite PBX, thermoplastic TNT-RDX-Al explosive, fusing TNT-RDX-Al explosive, TNT, The specific shock wave energy, the specific bubble energy, the total specific energy of warhead with shell decreased compared to warhead without shell. The total specific energy decreased 25%, 21%, 15% and 15%. It is obvious that shell is important for underwater explosion effects. Therefore, the influence of shell must be considered and can't be simplified for energy effects of underwater weapons.
With the experimental study of underwater explosion for confined and unconfined in free field water, the characteristic parameters of explosion, such as the peak pressure of shock wave, the specific shock wave energy, the specific bubble energy, the total specific energy and the relative total energy of the explosives were compared and analyzed. The results showed that the peak pressure are, different for thermoplastic TNT-RDX-Al explosive, fusing TNT-RDX-Al explosive, composite PBX and TNT, Other parameters are, composite PBX, thermoplastic TNT-RDX-Al explosive, fusing TNT-RDX-Al explosive, TNT, The specific shock wave energy, the specific bubble energy, the total specific energy of warhead with shell decreased compared to warhead without shell. The total specific energy decreased 25%, 21%, 15% and 15%. It is obvious that shell is important for underwater explosion effects. Therefore, the influence of shell must be considered and can't be simplified for energy effects of underwater weapons.
2018, 38(6): 1378-1385.
doi: 10.11883/bzycj-2017-0125
Abstract:
Based on a verified finite element model, numerical model of H beams subjected to lateral impact was established by ABAQUS. The accuracy of finite element models was validated against existing experimental results. The failure process of H beams and the influences of width-to-thickness ratios on the dynamic behaviors of H beams were systematically investigated. Then, the effects of flange thickness and web thickness on the stable impact forces, peak impact forces and energy dissipation were accurately analyzed. The results show that the failure mode of both side pin-ended steel beam subjected to transverse impact was global bending failure. Under certain impact energy the stable impact forces were mainly affected by the flange thickness and the peak impact forces. Furthermore, the effect of flange thickness on the dynamic behaviors of H beams was more obvious than the effect of the web thickness. In addition, the results of numerical analysis provided a basis and reference for the design of resisting impact of H beams.
Based on a verified finite element model, numerical model of H beams subjected to lateral impact was established by ABAQUS. The accuracy of finite element models was validated against existing experimental results. The failure process of H beams and the influences of width-to-thickness ratios on the dynamic behaviors of H beams were systematically investigated. Then, the effects of flange thickness and web thickness on the stable impact forces, peak impact forces and energy dissipation were accurately analyzed. The results show that the failure mode of both side pin-ended steel beam subjected to transverse impact was global bending failure. Under certain impact energy the stable impact forces were mainly affected by the flange thickness and the peak impact forces. Furthermore, the effect of flange thickness on the dynamic behaviors of H beams was more obvious than the effect of the web thickness. In addition, the results of numerical analysis provided a basis and reference for the design of resisting impact of H beams.
2018, 38(6): 1386-1393.
doi: 10.11883/bzycj-2017-0130
Abstract:
The load-bearing capacity and shock response of a state-of-the-art non-fracture super-zip separation device have been analyzed. Based on the static load-bearing analysis, the relationship between the meshing angle and the load-bearing capacity of the non-fracture super-zip separation device has been obtained. The results show that load-bearing capacity is inversely proportional to the angle of meshing teeth and that the critical meshing angle for reliable load-bearing is the self-locking angle of meshing teeth when the friction coefficient of the contact surfaces is constant. By means of the dynamic response analysis, the separation shock responses of the separation devices with different configurations have been gotten. The results show that the two kinds of non-fracture separation devices with different meshing angle can be separated under lower inner pressure compared with the conventional super-zip separation device, and that the peak values of the acceleration history curves of the non-fracture separation device with 5.7° meshing angle configuration are smaller than those of the conventional super-zip separation device at the same measuring points in all three directions.
The load-bearing capacity and shock response of a state-of-the-art non-fracture super-zip separation device have been analyzed. Based on the static load-bearing analysis, the relationship between the meshing angle and the load-bearing capacity of the non-fracture super-zip separation device has been obtained. The results show that load-bearing capacity is inversely proportional to the angle of meshing teeth and that the critical meshing angle for reliable load-bearing is the self-locking angle of meshing teeth when the friction coefficient of the contact surfaces is constant. By means of the dynamic response analysis, the separation shock responses of the separation devices with different configurations have been gotten. The results show that the two kinds of non-fracture separation devices with different meshing angle can be separated under lower inner pressure compared with the conventional super-zip separation device, and that the peak values of the acceleration history curves of the non-fracture separation device with 5.7° meshing angle configuration are smaller than those of the conventional super-zip separation device at the same measuring points in all three directions.
2018, 38(6): 1394-1403.
doi: 10.11883/bzycj-2017-0128
Abstract:
Aiming at the safety problem of existing large oil tank under near base blasting excavation, the dynamic response of large oil tank is analyzed by numerical simulation method, based on the implicit-to-explicit sequential solution procedure and the fluid solid coupling algorithm of ANSYS/LS-DYNA. different positions are obtained, by which it is not appropriate to determine the dangerous point of the tank wall because the distributions of the particle vibration velocities are very complex. The dynamic stress distribution on the tank wall is summarized, and the results show that the influence of blasting vibration on the oil tank is mainly concentrated on the lower part of the explosion side, and that the elephant foot buckling deformation is most likely produced at the height of 3 meters on the detonation side of tank wall; The particle vibration velocity of the tank wall under different frequency of blasting vibration is analyzed. The results show that in the main frequency range of blasting vibration, the particle vibration velocity on the tank wall decreases with the decrease of blasting vibration frequency if the load frequency is much larger than the natural frequency of the tank; The relationship between the particle vibration velocity and the liquid level in the tank is established, and the results show that lowering the height of liquid level can effectively improve the safety threshold of blasting vibration of the oil tank, and the storage liquid height of adjacent storage tanks should not be higher than 10 m for blasting operations.
Aiming at the safety problem of existing large oil tank under near base blasting excavation, the dynamic response of large oil tank is analyzed by numerical simulation method, based on the implicit-to-explicit sequential solution procedure and the fluid solid coupling algorithm of ANSYS/LS-DYNA. different positions are obtained, by which it is not appropriate to determine the dangerous point of the tank wall because the distributions of the particle vibration velocities are very complex. The dynamic stress distribution on the tank wall is summarized, and the results show that the influence of blasting vibration on the oil tank is mainly concentrated on the lower part of the explosion side, and that the elephant foot buckling deformation is most likely produced at the height of 3 meters on the detonation side of tank wall; The particle vibration velocity of the tank wall under different frequency of blasting vibration is analyzed. The results show that in the main frequency range of blasting vibration, the particle vibration velocity on the tank wall decreases with the decrease of blasting vibration frequency if the load frequency is much larger than the natural frequency of the tank; The relationship between the particle vibration velocity and the liquid level in the tank is established, and the results show that lowering the height of liquid level can effectively improve the safety threshold of blasting vibration of the oil tank, and the storage liquid height of adjacent storage tanks should not be higher than 10 m for blasting operations.
2018, 38(6): 1404-1411.
doi: 10.11883/bzycj-2017-0160
Abstract:
To find out about the wounding mechanisms of bullets penetrating human bodies, we simulated in this work the processes of bullets penetrating ballistic gelatin using the ballistic model. By taking the root mean squares of the theoretical errors of the horizontal displacements, the vertical displacements, the lateral displacements, the pitch angles and the yaw angles as the objective functions, treating the undetermined initial parameters of the bullet and the force coefficients in the ballistic model as the optimization variables, and using the Gamultiobj method, one of the multi-objective algorithms, we successfully found the set of the Pareto solutions to the objective functions, and selected the optimum solution to the optimization variables through the TOPSIS strategy from the Pareto solutions. Our studies show that the optimum solution is reliable and can present precise simulation of the motions of the 7.62 mm rifle bullet.
To find out about the wounding mechanisms of bullets penetrating human bodies, we simulated in this work the processes of bullets penetrating ballistic gelatin using the ballistic model. By taking the root mean squares of the theoretical errors of the horizontal displacements, the vertical displacements, the lateral displacements, the pitch angles and the yaw angles as the objective functions, treating the undetermined initial parameters of the bullet and the force coefficients in the ballistic model as the optimization variables, and using the Gamultiobj method, one of the multi-objective algorithms, we successfully found the set of the Pareto solutions to the objective functions, and selected the optimum solution to the optimization variables through the TOPSIS strategy from the Pareto solutions. Our studies show that the optimum solution is reliable and can present precise simulation of the motions of the 7.62 mm rifle bullet.
Characteristics of draging period cavity formation in liquid filling container by fragment impacting
2018, 38(6): 1412-1418.
doi: 10.11883/bzycj-2017-0188
Abstract:
To study the characteristics of the cavities formed by the fragment impacting liquid filling container, the forming process of the cavities in the liquid-filled containers was studied through numerical and experimental studies. In addition, the effects of the impacting velocity and the liquid medium of the cavity were analyzed. The results show that the cavity formed in the liquid is approximate a cone, the maximum diameter, length and length-diameter ratio of the cavity increase with fragment moving. The ratio of length to diameter eventually approches a certain value, and the value is approximate 3.9. The maximum diameter of the cavity increases with the increase of the fragment impact velocity. The maximum diameter and the length-diameter ratio of the cavity in the diesel medium are similar to those in the water medium, and the length-diameter ratio of the cavity approches 4.25.The maximum diameter and the length-diameter ratio in the diesel medium are larger than those in the water medium.
To study the characteristics of the cavities formed by the fragment impacting liquid filling container, the forming process of the cavities in the liquid-filled containers was studied through numerical and experimental studies. In addition, the effects of the impacting velocity and the liquid medium of the cavity were analyzed. The results show that the cavity formed in the liquid is approximate a cone, the maximum diameter, length and length-diameter ratio of the cavity increase with fragment moving. The ratio of length to diameter eventually approches a certain value, and the value is approximate 3.9. The maximum diameter of the cavity increases with the increase of the fragment impact velocity. The maximum diameter and the length-diameter ratio of the cavity in the diesel medium are similar to those in the water medium, and the length-diameter ratio of the cavity approches 4.25.The maximum diameter and the length-diameter ratio in the diesel medium are larger than those in the water medium.
2018, 38(6): 1419-1428.
doi: 10.11883/bzycj-2017-0209
Abstract:
To improve the calculation efficiency and describe the failure process of concrete under blast loading, a coupled SPH-FEM algorithm was used to simulate blast crater of concrete in this study. First, based on the partial Holmquist-Johnson-Cook(HJC) constitutive parameters of C30 concrete, and the remaining parameters determined via theoretical derivation, the numerical calculation was performed and the results were then compared with the measured data by taking the parameters into the numerical model. The sensitivities of 21 parameters for the HJC model were finally analyzed with peak pressure and peak acceleration. The results show that the coupled SPH-FEM algorithm can simulate the whole process of blast crater under the blast loading, and it may accurately deal with the SPH boundary problem. Based on the parameters of C30 concrete HJC model, the calculated results of the coupled algorithm agree well with the experimental ones, which demonstrates the rationality of the determining method for HJC constitutive parameters. In addition, the parameters have different sensitivities to the results of blast problem, and these parameters significantly influencing the peak pressure and peak acceleration should be paid enough attention in the process of its determination.
To improve the calculation efficiency and describe the failure process of concrete under blast loading, a coupled SPH-FEM algorithm was used to simulate blast crater of concrete in this study. First, based on the partial Holmquist-Johnson-Cook(HJC) constitutive parameters of C30 concrete, and the remaining parameters determined via theoretical derivation, the numerical calculation was performed and the results were then compared with the measured data by taking the parameters into the numerical model. The sensitivities of 21 parameters for the HJC model were finally analyzed with peak pressure and peak acceleration. The results show that the coupled SPH-FEM algorithm can simulate the whole process of blast crater under the blast loading, and it may accurately deal with the SPH boundary problem. Based on the parameters of C30 concrete HJC model, the calculated results of the coupled algorithm agree well with the experimental ones, which demonstrates the rationality of the determining method for HJC constitutive parameters. In addition, the parameters have different sensitivities to the results of blast problem, and these parameters significantly influencing the peak pressure and peak acceleration should be paid enough attention in the process of its determination.
2018, 38(6): 1429-1434.
doi: 10.11883/bzycj-2017-0170
Abstract:
In order to estimate the quasi-static pressure of TNT when it explodes in closed space, the calculation model of the quasi-static pressure is derived basing on the theoretical analysis. Moreover, a series of TNT's internal explosion tests are performed, these tests take the explosion vessel and explosion chamber as the closed container. The results show that the quasi-static pressure increases accompanied by multiple reflections of shockwave and the pressure reaches to the maximum when the reflection is over. The ratio of charge quality and volume is the main factor influenting quasi-static pressure. The peak and increasing rate of quasi-static pressure will increase with the growth of the ratio of charge quality and volume. According to the experimental data of TNT's internal explosion, the empirical formula of the peak for the quasi-static pressure is fitted, The formula can be used to calculate of quasi-static pressure's peak value and assess the lethality of internal explosion.
In order to estimate the quasi-static pressure of TNT when it explodes in closed space, the calculation model of the quasi-static pressure is derived basing on the theoretical analysis. Moreover, a series of TNT's internal explosion tests are performed, these tests take the explosion vessel and explosion chamber as the closed container. The results show that the quasi-static pressure increases accompanied by multiple reflections of shockwave and the pressure reaches to the maximum when the reflection is over. The ratio of charge quality and volume is the main factor influenting quasi-static pressure. The peak and increasing rate of quasi-static pressure will increase with the growth of the ratio of charge quality and volume. According to the experimental data of TNT's internal explosion, the empirical formula of the peak for the quasi-static pressure is fitted, The formula can be used to calculate of quasi-static pressure's peak value and assess the lethality of internal explosion.
2018, 38(6): 1435-1440.
doi: 10.11883/bzycj-2017-0167
Abstract:
In this paper, five kinds of hydrocarbon gaseous mixture were selected as working medium. By using high voltage spark ignition method and optical fiber probe, the propagation velocity of detonation wave in pipeline was measured near failure state condition. Experiments were conducted based on a self-made detonation pipeline, which includes a drive section and three different test sections with 1.5-mm, 3.2-mm and 12.7-mm inner diameter, respectively. Experimental results reverified that there are six different propagation modes, which are steady detonation, rapid fluctuation detonation, stuttering detonation, galloping detonation, low velocity detonation and detonation failure, respectively for pipeline detonation. Among them, gaseous mixtures C2H2+2.5O2+70%Ar and C2H2+2.5O2+85%Ar (both have low activation energy), have only three propagating modes, i.e. steady, rapid fluctuation and failure modes; while for other three gaseous mixtures C3H8+5O2, C2H2+5N2O and CH4+2O2 (with higher activation energy), there are six different propagating modes. The results show that besides gas composition and initial pressure, the activation energy of gaseous mixture may also affect the propagation state of detonation wave in pipeline.
In this paper, five kinds of hydrocarbon gaseous mixture were selected as working medium. By using high voltage spark ignition method and optical fiber probe, the propagation velocity of detonation wave in pipeline was measured near failure state condition. Experiments were conducted based on a self-made detonation pipeline, which includes a drive section and three different test sections with 1.5-mm, 3.2-mm and 12.7-mm inner diameter, respectively. Experimental results reverified that there are six different propagation modes, which are steady detonation, rapid fluctuation detonation, stuttering detonation, galloping detonation, low velocity detonation and detonation failure, respectively for pipeline detonation. Among them, gaseous mixtures C2H2+2.5O2+70%Ar and C2H2+2.5O2+85%Ar (both have low activation energy), have only three propagating modes, i.e. steady, rapid fluctuation and failure modes; while for other three gaseous mixtures C3H8+5O2, C2H2+5N2O and CH4+2O2 (with higher activation energy), there are six different propagating modes. The results show that besides gas composition and initial pressure, the activation energy of gaseous mixture may also affect the propagation state of detonation wave in pipeline.
