2007 Vol. 27, No. 4
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2007, 27(4): 289-295.
doi: 10.11883/1001-1455(2007)04-0289-07
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Abstract:
The experimental investigation of TiNi cantilever with circular cross-section under transversal impact loading was conducted by using a revised Hopkinson bar apparatus, and compared to 45 steel cantilever. The purpose of this study is to explore the effect of phase transformation on the dynamic behavior of structures. The results show that at the same impact condition, the energy absorbing efficiency of a TiNi cantilever is better than that of a 45 steel cantilever. It is found that a local transformation hinge (TH) may generate at the inner side of TiNi cantilevers fixed end during impact loading, which changes the resistance characteristic of the cantilever. The TH disappears after unloading and the TiNi cantilever recovers to its original position, however, the 45 steel cantilever has large residual deformation. The impact response of TiNi cantilever is controlled by the thermo-elastic martensite phase transformation and inverse transformation, which differs from the conventional elastic-plastic mechanism.
The experimental investigation of TiNi cantilever with circular cross-section under transversal impact loading was conducted by using a revised Hopkinson bar apparatus, and compared to 45 steel cantilever. The purpose of this study is to explore the effect of phase transformation on the dynamic behavior of structures. The results show that at the same impact condition, the energy absorbing efficiency of a TiNi cantilever is better than that of a 45 steel cantilever. It is found that a local transformation hinge (TH) may generate at the inner side of TiNi cantilevers fixed end during impact loading, which changes the resistance characteristic of the cantilever. The TH disappears after unloading and the TiNi cantilever recovers to its original position, however, the 45 steel cantilever has large residual deformation. The impact response of TiNi cantilever is controlled by the thermo-elastic martensite phase transformation and inverse transformation, which differs from the conventional elastic-plastic mechanism.
2007, 27(4): 296-305.
doi: 10.11883/1001-1455(2007)04-0296-10
Abstract:
The dynamic plastic buckling of earth penetrating weapon(EPW) was experimentally studied. Two failure modes, i.e., crapy buckling and dynamic expansion buckling for different length-diameter-ratio projectiles, were observed in the tests. Different failure modes depend on the geometry of projectile, initial impact conditions and target material. Distinguished from the ductile hole enlarging for rigid sharp projectile impacting metallic target, the buckling failure may induce a sharp projectile to severely deform like blunter nose and perforate the target plate as shear plugging. Critical condition of dynamic plastic buckling of projectile was defined based on the analyses of Euler elastic buckling of hollow slender shell and plastic yielding limit of projectiles. The equivalent condition of steel plate and concrete target was formulated.
The dynamic plastic buckling of earth penetrating weapon(EPW) was experimentally studied. Two failure modes, i.e., crapy buckling and dynamic expansion buckling for different length-diameter-ratio projectiles, were observed in the tests. Different failure modes depend on the geometry of projectile, initial impact conditions and target material. Distinguished from the ductile hole enlarging for rigid sharp projectile impacting metallic target, the buckling failure may induce a sharp projectile to severely deform like blunter nose and perforate the target plate as shear plugging. Critical condition of dynamic plastic buckling of projectile was defined based on the analyses of Euler elastic buckling of hollow slender shell and plastic yielding limit of projectiles. The equivalent condition of steel plate and concrete target was formulated.
2007, 27(4): 306-311.
doi: 10.11883/1001-1455(2007)04-0306-06
Abstract:
The process of rock failure under impact loading was analyzed with mechanics model and the dynamic behavior was described according to hard rock characters. The stress state transfered from elastic state to intrinsic friction state, finally liquid hydrodynamics state. Based on analysis of intrinsic friction state, the deformation near impact loading in rock is similar to one-dimension at deformation near strong impact loading zone. The stress wave from the loading can be regarded as short-wave which is similar to shock wave. Characteristics of the short-wave have sharp varieties in a cabined zone near wave front. According to the stress and the deformation state of rock near the strong impact loading zone, the velocity field was deduced by use of conservation relation of mass. Based on short-wave theory, the stress wave attenuation rule in rock near the strong impact loading was gained.
The process of rock failure under impact loading was analyzed with mechanics model and the dynamic behavior was described according to hard rock characters. The stress state transfered from elastic state to intrinsic friction state, finally liquid hydrodynamics state. Based on analysis of intrinsic friction state, the deformation near impact loading in rock is similar to one-dimension at deformation near strong impact loading zone. The stress wave from the loading can be regarded as short-wave which is similar to shock wave. Characteristics of the short-wave have sharp varieties in a cabined zone near wave front. According to the stress and the deformation state of rock near the strong impact loading zone, the velocity field was deduced by use of conservation relation of mass. Based on short-wave theory, the stress wave attenuation rule in rock near the strong impact loading was gained.
2007, 27(4): 312-318.
doi: 10.11883/1001-1455(2007)04-0312-07
Abstract:
The cell sizes caused by fuel-air cloud detonation were investigated by smoked foil in a vertical shock tube. It indicates that the relationship of the cell sizes and equivalence ratios shows a U-curve, The minimal cell size is obtained when equivalence ratio is slightly larger than 1. This result is similar to that in gaseous detonation. A more complex celluar structure takes place with the enhancement of ignition energy. The cell size of hydrocarbon-air cloud increases with the number of carbon atoms, and the ratio of its length to width is less than that of the gaseous fuel. Experimental results are helpful to understand the detonation nature of hydrocarbon fuel-air mixtures.
The cell sizes caused by fuel-air cloud detonation were investigated by smoked foil in a vertical shock tube. It indicates that the relationship of the cell sizes and equivalence ratios shows a U-curve, The minimal cell size is obtained when equivalence ratio is slightly larger than 1. This result is similar to that in gaseous detonation. A more complex celluar structure takes place with the enhancement of ignition energy. The cell size of hydrocarbon-air cloud increases with the number of carbon atoms, and the ratio of its length to width is less than that of the gaseous fuel. Experimental results are helpful to understand the detonation nature of hydrocarbon fuel-air mixtures.
2007, 27(4): 319-324.
doi: 10.11883/1001-1455(2007)04-0319-06
Abstract:
By the ANSYS/LS-DYNA code, two new projectiles were designed based on the homemade 9 mm handgun projectile. The two new projectiles with soft and empty tines have the capability of high execution and low inbreaking. The velocity attenuation, displacement, relative kinetic energy variation curves and the instantaneous cavum were obtained by simulating the three projectiles entering the water. The acquired velocity attenuation curve is almost the same to the experimental velocity attenuation curve. Comparisons of the results reveal that capabilities of high execution and low inbreaking of the projectile with empty tine are better than those of the projectile with soft tine. Calculations show that the ballistic trajectory will motion in the process of the projectile with empty tine entering the water with oblique angle.
By the ANSYS/LS-DYNA code, two new projectiles were designed based on the homemade 9 mm handgun projectile. The two new projectiles with soft and empty tines have the capability of high execution and low inbreaking. The velocity attenuation, displacement, relative kinetic energy variation curves and the instantaneous cavum were obtained by simulating the three projectiles entering the water. The acquired velocity attenuation curve is almost the same to the experimental velocity attenuation curve. Comparisons of the results reveal that capabilities of high execution and low inbreaking of the projectile with empty tine are better than those of the projectile with soft tine. Calculations show that the ballistic trajectory will motion in the process of the projectile with empty tine entering the water with oblique angle.
2007, 27(4): 325-330.
doi: 10.11883/1001-1455(2007)04-0325-06
Abstract:
The local normal detonation speed Dn of insensitive high explosive is closely relative to the local total curvature . To investigate the nonideal detonation of JB-9014 rate sticks(95wt.%TATB+5wt.% binder) at low temperature, series experiments were carried out at 30 ℃ with diameters of 10, 12.5, 15 and 30 mm respectively and compared with those at 24 ℃. Wave shape data were fitted with an analytic form, by which Dn() curves were calculated. The results show that for each diameter, wave shapes is slightly flatter in hotter charges than colder ones. For each temperature, waves propagate more ideally as charge diameter increases. When is smaller than 0.05, Dn() curves are concave upward and trace nearly a common path for any diameter and any temperature. When is larger than 0.05, Dn varies with curvature, diameter, temperature and Dn() curves diverge.
The local normal detonation speed Dn of insensitive high explosive is closely relative to the local total curvature . To investigate the nonideal detonation of JB-9014 rate sticks(95wt.%TATB+5wt.% binder) at low temperature, series experiments were carried out at 30 ℃ with diameters of 10, 12.5, 15 and 30 mm respectively and compared with those at 24 ℃. Wave shape data were fitted with an analytic form, by which Dn() curves were calculated. The results show that for each diameter, wave shapes is slightly flatter in hotter charges than colder ones. For each temperature, waves propagate more ideally as charge diameter increases. When is smaller than 0.05, Dn() curves are concave upward and trace nearly a common path for any diameter and any temperature. When is larger than 0.05, Dn varies with curvature, diameter, temperature and Dn() curves diverge.
2007, 27(4): 331-338.
doi: 10.11883/1001-1455(2007)04-0331-08
Abstract:
The rigid-perfectly plastic dynamic response of a slender projectile penetrating into a semi-infinte concrete target with a oblique angle was presented based on the theory of free-free beam subjected to impulsive lateral loading. The lateral and axial loading was given by dynamic cavity expansion theory. The distribution of compressive stress conducted by bending moment and axial inertial load was presented which indicated that slender EPW was sensitive to the effect of lateral impulsive loading resulted from non-ideal impact. A criterion expression, for the minimum thickness of the cartridges and the maximum oblique angle of projectile, without any bending failure and damage, were formulated in the case of hollow and slender missiles penetrating into semi-infinite concrete targets at different initial velocities and length-to-diameter ratio.
The rigid-perfectly plastic dynamic response of a slender projectile penetrating into a semi-infinte concrete target with a oblique angle was presented based on the theory of free-free beam subjected to impulsive lateral loading. The lateral and axial loading was given by dynamic cavity expansion theory. The distribution of compressive stress conducted by bending moment and axial inertial load was presented which indicated that slender EPW was sensitive to the effect of lateral impulsive loading resulted from non-ideal impact. A criterion expression, for the minimum thickness of the cartridges and the maximum oblique angle of projectile, without any bending failure and damage, were formulated in the case of hollow and slender missiles penetrating into semi-infinite concrete targets at different initial velocities and length-to-diameter ratio.
2007, 27(4): 339-344.
doi: 10.11883/1001-1455(2007)04-0339-06
Abstract:
Dynamic model of mix-refrigerant including flammable components leaking from vapor and liquid space was established. The influence of leakages on the flammability of mix-refrigerant was analyzed. A new method judging the burnable fatalness of mix-refrigerant increase or decrease in the process of leakages was put forward. Rresults can be useful to evaluate and forecast leakage accidents in the process of manufacturing, storing and transporting flammable, explosive mix-refrigerants.
Dynamic model of mix-refrigerant including flammable components leaking from vapor and liquid space was established. The influence of leakages on the flammability of mix-refrigerant was analyzed. A new method judging the burnable fatalness of mix-refrigerant increase or decrease in the process of leakages was put forward. Rresults can be useful to evaluate and forecast leakage accidents in the process of manufacturing, storing and transporting flammable, explosive mix-refrigerants.
2007, 27(4): 345-351.
doi: 10.11883/1001-1455(2007)04-0345-07
Abstract:
The propagation characteristics of stress waves in the solids with variable section was dissection. Based on the one-dimensional longitudinal wave motion theory and the harmonic analysis, the rules of the dispersion of the wave shape and the change of the wave amplitude which are due to the variation of the section are obtained, the wave evolution factor combined with the variable section is deduced, and the two-dimensional effect, such as the geometry dispersion due to the variation of the section, is discussed. The rules how the geometry parameters and section shape functions effect the evolution of stress waves in the solids are also calculated and discussed.
The propagation characteristics of stress waves in the solids with variable section was dissection. Based on the one-dimensional longitudinal wave motion theory and the harmonic analysis, the rules of the dispersion of the wave shape and the change of the wave amplitude which are due to the variation of the section are obtained, the wave evolution factor combined with the variable section is deduced, and the two-dimensional effect, such as the geometry dispersion due to the variation of the section, is discussed. The rules how the geometry parameters and section shape functions effect the evolution of stress waves in the solids are also calculated and discussed.
2007, 27(4): 352-357.
doi: 10.11883/1001-1455(2007)04-0352-06
Abstract:
The constitutive model was described based on the theory formwork of elastic-plastic hydrodynamics for saturated soil under the explosive loading, including the relation of pressure and volumetric strain and the relation of pressure and failure surface. The explosion wave propagation and the interaction between media and structure were simulated numerically by using LS-dyna software, the results of numerical simulation is in close agreement with that of foregone experimental investigation. The reappearance of some special phenomena for saturated soil makes clear that the constitutive model is usable.
The constitutive model was described based on the theory formwork of elastic-plastic hydrodynamics for saturated soil under the explosive loading, including the relation of pressure and volumetric strain and the relation of pressure and failure surface. The explosion wave propagation and the interaction between media and structure were simulated numerically by using LS-dyna software, the results of numerical simulation is in close agreement with that of foregone experimental investigation. The reappearance of some special phenomena for saturated soil makes clear that the constitutive model is usable.
2007, 27(4): 358-363.
doi: 10.11883/1001-1455(2007)04-0358-06
Abstract:
The experimental technique of split Hopkinson pressure bar is an effective method to carry out an experiment in study of the dynamic behavior of materials. But some problems such as non-uniform dynamic stress in a specimen and non-constant strain rate during the experiment may arise if the technique isnt modified. Polyurethane foams have been widely used in civilian and military areas. It is more important to study their mechanical behavior, especially, dynamic behavior. The dynamic behaviors of a polyurethane foam under the conditions of uniform stress in the specimen and constant strain rate were detained experimentally with modified spilt Hopkinson pressure bar technique.
The experimental technique of split Hopkinson pressure bar is an effective method to carry out an experiment in study of the dynamic behavior of materials. But some problems such as non-uniform dynamic stress in a specimen and non-constant strain rate during the experiment may arise if the technique isnt modified. Polyurethane foams have been widely used in civilian and military areas. It is more important to study their mechanical behavior, especially, dynamic behavior. The dynamic behaviors of a polyurethane foam under the conditions of uniform stress in the specimen and constant strain rate were detained experimentally with modified spilt Hopkinson pressure bar technique.
2007, 27(4): 364-379.
doi: 10.11883/1001-1455(2007)04-0364-06
Abstract:
A tandem follow-through warhead was designed. The experiments of the tandem warhead penetrating concrete target at different impacting velocities and different impacting angles were carried out by using smoothbore gun with a diameter of 100 mm. Experimental results show that the forward shaped-charge warhead penetrates a hole in the target firstly and the follow-through warhead continues to penetrate the target along the hole. Efficiency of the tandem follow-through penetrating targets is improved， especially at small impacting angle.
A tandem follow-through warhead was designed. The experiments of the tandem warhead penetrating concrete target at different impacting velocities and different impacting angles were carried out by using smoothbore gun with a diameter of 100 mm. Experimental results show that the forward shaped-charge warhead penetrates a hole in the target firstly and the follow-through warhead continues to penetrate the target along the hole. Efficiency of the tandem follow-through penetrating targets is improved， especially at small impacting angle.
2007, 27(4): 370-374.
doi: 10.11883/1001-1455(2007)04-0370-05
Abstract:
A shaped charge with steady energy output was developed to study all kinds of the explosives sensitivity to shaped charge jets, and its stability was validated by three methods. The jet sensitivities of such explosives as TNT, Comp B, and JB-B were experimentally evaluated by using the standard shaped charge. The obtained result is consistent with that from literature. The relationship between the velocity of jet head and the cover thickness was determined, and the experimental formula was obtained.
A shaped charge with steady energy output was developed to study all kinds of the explosives sensitivity to shaped charge jets, and its stability was validated by three methods. The jet sensitivities of such explosives as TNT, Comp B, and JB-B were experimentally evaluated by using the standard shaped charge. The obtained result is consistent with that from literature. The relationship between the velocity of jet head and the cover thickness was determined, and the experimental formula was obtained.
2007, 27(4): 375-379.
doi: 10.11883/1001-1455(2007)04-0375-05
Abstract:
It is necessary to give a testing standard for measuring the non-explosion farm AN. A new kind of standard detonator was designed to ensure the coherence of testing results. The obtained results show that the out-put of the standard detonator is larger than that of 8 industry detonator， and the tested results is equable. The standard detonator corresponds with the requirements.
It is necessary to give a testing standard for measuring the non-explosion farm AN. A new kind of standard detonator was designed to ensure the coherence of testing results. The obtained results show that the out-put of the standard detonator is larger than that of 8 industry detonator， and the tested results is equable. The standard detonator corresponds with the requirements.
2007, 27(4): 380-384.
doi: 10.11883/1001-1455(2007)04-0380-05
Abstract:
In order to detect underwater objects such as submarines, an underwater acoustic source is required, with its frequency in the range of 1-4 kHz, and the pressure peak of the acoustic pulse more than 1 MPa. This kind of acoustic pulse can be generated by the means of large current pulse discharge under water. This paper describes the development of this kind of acoustic pulse generator. This type of pulsed power acoustic source has many advantages over the others, it has great potential in millitary application.
