2015 Vol. 35, No. 4
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2015, 35(4): 449-453.
doi: 10.11883/1001-1455(2015)04-0449-05
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In order to calculate the detonation products and parameters, Lagrange multiplier and Newton iterative method were used to predict detonation products. The state equation of BKW was used to predict detonation parameters. In a range of pressure from 0 to 600 GPa and temperature from 300 to 15 000 K, diamond was intended as the elemental carbon product. Based on the principle of minimum free energy, the equilibrium compositions of detonation products were calculated by using Newton iterative method, which need not calculate the free energy of each composition. The parameters of the state equation of BKW were modified.α=0.5; β=0.298; θ=6 620; κ=9.50. Using self-made program, the detonation properties at CJ point of PETN, whose density is 1.77 g/cm3, were calculated with the theory in this paper and the equation of Hugoniot. The results show satisfactory agreement with the experimental data, with the error less than 1%. The density of detonation products is also predicted easily. When the density of PETN is 1.77 g/cm3, the density of detonation products is 2.43 g/cm3.
In order to calculate the detonation products and parameters, Lagrange multiplier and Newton iterative method were used to predict detonation products. The state equation of BKW was used to predict detonation parameters. In a range of pressure from 0 to 600 GPa and temperature from 300 to 15 000 K, diamond was intended as the elemental carbon product. Based on the principle of minimum free energy, the equilibrium compositions of detonation products were calculated by using Newton iterative method, which need not calculate the free energy of each composition. The parameters of the state equation of BKW were modified.α=0.5; β=0.298; θ=6 620; κ=9.50. Using self-made program, the detonation properties at CJ point of PETN, whose density is 1.77 g/cm3, were calculated with the theory in this paper and the equation of Hugoniot. The results show satisfactory agreement with the experimental data, with the error less than 1%. The density of detonation products is also predicted easily. When the density of PETN is 1.77 g/cm3, the density of detonation products is 2.43 g/cm3.
2015, 35(4): 454-458.
doi: 10.11883/1001-1455(2015)04-0454-05
Abstract:
The surface tension of binder containing different additives and the contact angle with RDX were measured by a contact angle meter. The coating quality is evaluated according to the micro-images acquired by scanning electron microscopy (SEM), the spectrum by X-ray photoelectron spectroscopy (XPS) and the impact sensitivity of the samples. The spreading coefficient (S) and adhesive work (W12) were calculated, and then the dependence of the coverage degree (R) on S and W12 were analyzed. The results show that R increased with the increase of S, and reduced with the increase of W12. It indicates that the better coating quality comes with the bigger S and the smaller W12. And the lower mechanical sensitivity comes with the greater coverge degree. The results of SEM show that a thin layer of film was formed on the surface of RDX. The results of XPS show that the additives can raise the coverage degree from 16.85% to 95.41%. The results of impact sensitivity show that the additives can raise the characteristic fall distance from 11.47 cm to 25.12 cm, and significantly reduce friction sensitivity.
The surface tension of binder containing different additives and the contact angle with RDX were measured by a contact angle meter. The coating quality is evaluated according to the micro-images acquired by scanning electron microscopy (SEM), the spectrum by X-ray photoelectron spectroscopy (XPS) and the impact sensitivity of the samples. The spreading coefficient (S) and adhesive work (W12) were calculated, and then the dependence of the coverage degree (R) on S and W12 were analyzed. The results show that R increased with the increase of S, and reduced with the increase of W12. It indicates that the better coating quality comes with the bigger S and the smaller W12. And the lower mechanical sensitivity comes with the greater coverge degree. The results of SEM show that a thin layer of film was formed on the surface of RDX. The results of XPS show that the additives can raise the coverage degree from 16.85% to 95.41%. The results of impact sensitivity show that the additives can raise the characteristic fall distance from 11.47 cm to 25.12 cm, and significantly reduce friction sensitivity.
2015, 35(4): 459-466.
doi: 10.11883/1001-1455(2015)04-0459-08
Abstract:
The dynamic response of brick wall under blast shock vibration is very complex. it is difficult to establish its constitutive relation accurately. Several common finite-element methods to simulate brick wall were presented and merits and drawbacks of these method were analyzed. A three-dimensional finite-element model is applied in which the bricks and mortar are considered separatedly. LS-DYNA software is used to simulate the failure process of brick wall under horizontal blast shock vibration and the results were agreed well with the experiment. The research indicates that the analytical model considers the complex interaction of brick and mortar integratedly and the mortar layer is modeled separately which ensured the validity and correctness of the numerical simulation, so the accumulative damage of the mortar layer between the bricks in the experiment could be simulated accurately.
The dynamic response of brick wall under blast shock vibration is very complex. it is difficult to establish its constitutive relation accurately. Several common finite-element methods to simulate brick wall were presented and merits and drawbacks of these method were analyzed. A three-dimensional finite-element model is applied in which the bricks and mortar are considered separatedly. LS-DYNA software is used to simulate the failure process of brick wall under horizontal blast shock vibration and the results were agreed well with the experiment. The research indicates that the analytical model considers the complex interaction of brick and mortar integratedly and the mortar layer is modeled separately which ensured the validity and correctness of the numerical simulation, so the accumulative damage of the mortar layer between the bricks in the experiment could be simulated accurately.
2015, 35(4): 467-472.
doi: 10.11883/1001-1455(2015)04-0467-06
Abstract:
Large scale borehole soundless cracking is significantly different from traditional soundless cracking. Experiments were made to measure the expansive pressure of the soundless cracking agent (SCA) working in the boreholes of ∅40 mm and ∅100 mm. The different phenomenon between two sizes of cracking was compared and analyzed to show that the increase of borehole diameter could increase the expansive pressure and speed up the reaction. Based on the experimental data, finite element analysis was utilized to study the stress concentration and stress distribution around the borehole during the cracking process. Using the experimental data and the results of the finite element method, the elastic model of rock stress distribution was modified, and the stress distribution equations were proposed. The formulas of borehole arrangement parameters deduced by those equations are suitable for the actual engineering.
Large scale borehole soundless cracking is significantly different from traditional soundless cracking. Experiments were made to measure the expansive pressure of the soundless cracking agent (SCA) working in the boreholes of ∅40 mm and ∅100 mm. The different phenomenon between two sizes of cracking was compared and analyzed to show that the increase of borehole diameter could increase the expansive pressure and speed up the reaction. Based on the experimental data, finite element analysis was utilized to study the stress concentration and stress distribution around the borehole during the cracking process. Using the experimental data and the results of the finite element method, the elastic model of rock stress distribution was modified, and the stress distribution equations were proposed. The formulas of borehole arrangement parameters deduced by those equations are suitable for the actual engineering.
2015, 35(4): 473-481.
doi: 10.11883/1001-1455(2015)04-0473-09
Abstract:
A new type of creased square tube specifically designed with some folded lobes added at the wall of ordinary square tube is studied inorder not only to reduce the initial loading, but also to enhance the effective plastic area distortion which leads to a higher energy absorption efficiency. The numerical results based on the FEM package ABAQUS /EXPLICIT verify that the pre-folds could lead the pre-folded origami to the expected large deformation mode under low speed impact, which effectively reduce the peak load and also improve the average load of load-displacement curve compared with ordinary square tubes. The load-displacement curve obtained by FEM is identical to the results of low droped hammer test, which verifies the credibility of the numerical results as well as the high energy absorption characteristics of the tube.
A new type of creased square tube specifically designed with some folded lobes added at the wall of ordinary square tube is studied inorder not only to reduce the initial loading, but also to enhance the effective plastic area distortion which leads to a higher energy absorption efficiency. The numerical results based on the FEM package ABAQUS /EXPLICIT verify that the pre-folds could lead the pre-folded origami to the expected large deformation mode under low speed impact, which effectively reduce the peak load and also improve the average load of load-displacement curve compared with ordinary square tubes. The load-displacement curve obtained by FEM is identical to the results of low droped hammer test, which verifies the credibility of the numerical results as well as the high energy absorption characteristics of the tube.
2015, 35(4): 482-488.
doi: 10.11883/1001-1455(2015)04-0482-07
Abstract:
In order to simulate the scene of secondary explosion caused by the fuel tank of vehicle, equipment bombarded, the shelling experiments of Ø30 mm fragmentation explosive incendiary shell were conducted in the external field. The process of diesel fuel detonated and temperature parameters of fireball were recorded by a high-speed camera, the infrared thermal imager separately. Explosion performance of ordinary diesel fuel, diesel fuel with water content and explosion suppression diesel fuel were compared and evaluated. The results show that the explosion fireball occurs due to the explosive energy acting on aerosols which result from quick mixing of air and diesel fuel dispersed from the fuel tank at the moment when shells shoot the fuel tank. The development all the explosion fireballs have three phases, but there are still notable differences in the sizes, expanding rates and surface temperatures among explosion fireballs of three types of diesel fuel. These three fireball parameters of ordinary diesel fuel and diesel fuel with water content are similar, which are greater than that of explosion suppression diesel fuel. Fuel tank damage volume of diesel fuel with water content is 108.00 dm3, which is far greater than that of ordinary diesel fuel (57.65 dm3) and explosion suppression diesel fuel (38.15 dm3). The results also confirm the difference between three types of diesel fuel in explosion performance.
In order to simulate the scene of secondary explosion caused by the fuel tank of vehicle, equipment bombarded, the shelling experiments of Ø30 mm fragmentation explosive incendiary shell were conducted in the external field. The process of diesel fuel detonated and temperature parameters of fireball were recorded by a high-speed camera, the infrared thermal imager separately. Explosion performance of ordinary diesel fuel, diesel fuel with water content and explosion suppression diesel fuel were compared and evaluated. The results show that the explosion fireball occurs due to the explosive energy acting on aerosols which result from quick mixing of air and diesel fuel dispersed from the fuel tank at the moment when shells shoot the fuel tank. The development all the explosion fireballs have three phases, but there are still notable differences in the sizes, expanding rates and surface temperatures among explosion fireballs of three types of diesel fuel. These three fireball parameters of ordinary diesel fuel and diesel fuel with water content are similar, which are greater than that of explosion suppression diesel fuel. Fuel tank damage volume of diesel fuel with water content is 108.00 dm3, which is far greater than that of ordinary diesel fuel (57.65 dm3) and explosion suppression diesel fuel (38.15 dm3). The results also confirm the difference between three types of diesel fuel in explosion performance.
2015, 35(4): 489-495.
doi: 10.11883/1001-1455(2015)04-0489-07
Abstract:
In order to investigate the performances of corundum-rubble overlays subjected to small-diameter bomb penetration, a three-dimensional finite element model is developed. The model is used to study the projectile penetration into the corundum-rubble overlay by taking into account the randomness of corundum-rubble in size, shape and spatial distribution. This paper focuses on the following two aspects. The first is the effects of penetration conditions (such as projectile velocity, impact angle and position) on penetration depth and terminal yawing angle. The second is the influences of the constituted parameters for the corundum-rubble overlay (such as size and volume fraction of corundum-rubble, strength of grouted concrete). The numerical results are compared with the data from rock-rubble overlay, and better performances are found for the corundum-rubble overlay subjected to projectile penetration.
In order to investigate the performances of corundum-rubble overlays subjected to small-diameter bomb penetration, a three-dimensional finite element model is developed. The model is used to study the projectile penetration into the corundum-rubble overlay by taking into account the randomness of corundum-rubble in size, shape and spatial distribution. This paper focuses on the following two aspects. The first is the effects of penetration conditions (such as projectile velocity, impact angle and position) on penetration depth and terminal yawing angle. The second is the influences of the constituted parameters for the corundum-rubble overlay (such as size and volume fraction of corundum-rubble, strength of grouted concrete). The numerical results are compared with the data from rock-rubble overlay, and better performances are found for the corundum-rubble overlay subjected to projectile penetration.
2015, 35(4): 496-500.
doi: 10.11883/1001-1455(2015)04-0496-05
Abstract:
The mass of explosive which the aluminum/copper cylinder shells were blasted shutter was found with finite element methods. And on the basis of this, the blast shutter models were simulated many times by the smoothed particle hydrodynamics method to achieve optimization. Then the experimental models were determined by comparing the simulation results. The experimental results agree with the simulation results. So the simulation results can be helpful for understanding the experimental results, and it saves the time and increases the efficiency.
The mass of explosive which the aluminum/copper cylinder shells were blasted shutter was found with finite element methods. And on the basis of this, the blast shutter models were simulated many times by the smoothed particle hydrodynamics method to achieve optimization. Then the experimental models were determined by comparing the simulation results. The experimental results agree with the simulation results. So the simulation results can be helpful for understanding the experimental results, and it saves the time and increases the efficiency.
2015, 35(4): 501-506.
doi: 10.11883/1001-1455(2015)04-0501-06
Abstract:
The fixed sampling frequency is not reasonable for obtaining the signal parameters with variable changing speed during the measurement process of high-g acceleration. A digital frequency-change sampling method was put forward in this paper to reduce data redundancy and ensure signal without distortion as well based on the method of changing ADC Sampling-frequency. Two pieces of memory were used to fulfill this target. Sufficient data source got by high-speed sampling frequency was written to the first memory at the same frequency, and the address of the second memory was changed with frequency propulsion according to the characteristic of signal variation, then the data stored in the first memory was extracted thus the frequency-change sampling got realized. Frequency measurement system could bear high impact by Hopkinson bar. Simulation and experiment confirmed that the frequency-change sampling method proposed in the paper can effectively solve the contradiction between the sampling frequency and data capacity.
The fixed sampling frequency is not reasonable for obtaining the signal parameters with variable changing speed during the measurement process of high-g acceleration. A digital frequency-change sampling method was put forward in this paper to reduce data redundancy and ensure signal without distortion as well based on the method of changing ADC Sampling-frequency. Two pieces of memory were used to fulfill this target. Sufficient data source got by high-speed sampling frequency was written to the first memory at the same frequency, and the address of the second memory was changed with frequency propulsion according to the characteristic of signal variation, then the data stored in the first memory was extracted thus the frequency-change sampling got realized. Frequency measurement system could bear high impact by Hopkinson bar. Simulation and experiment confirmed that the frequency-change sampling method proposed in the paper can effectively solve the contradiction between the sampling frequency and data capacity.
2015, 35(4): 507-512.
doi: 10.11883/1001-1455(2015)04-0507-06
Abstract:
In order to obtain dynamic tensile mechanical properties of metal materials under intermediate strain rate with servo-hydraulic machine, an indirect measurement method without changing the original structure of the testing maching is proposed to achieve accurate dynamic tensile load. The authentic dynamic behaviors are acquired at the plastic stage due to the oscillations of test data measured by the load cell integrated to the machine. In addition, the measurement of strain is solved in a non-contact mode relating to the digital image correlation method. The testing results indicate that both solutions developed in this paper can successfully test the mechanical properties in the dynamic tensile tests of metal materials.
In order to obtain dynamic tensile mechanical properties of metal materials under intermediate strain rate with servo-hydraulic machine, an indirect measurement method without changing the original structure of the testing maching is proposed to achieve accurate dynamic tensile load. The authentic dynamic behaviors are acquired at the plastic stage due to the oscillations of test data measured by the load cell integrated to the machine. In addition, the measurement of strain is solved in a non-contact mode relating to the digital image correlation method. The testing results indicate that both solutions developed in this paper can successfully test the mechanical properties in the dynamic tensile tests of metal materials.
2015, 35(4): 513-519.
doi: 10.11883/1001-1455(2015)04-0513-07
Abstract:
Aluminum to oxygen Al/O ratio is very important to the performance of aluminized explosives. In order to study the influence of the ratio on the performance of explosives in concrete, three kinds of aluminized explosives are taken into account, and their Al/O ratio are 0, 0.257 and 0.632, respectively. In this paper, the damaging process of concrete medium under explosion of cylindrical charge is numerically simulated using AUTODYN program. Meanwhile, within the range of relative distance from 2.5 to 10, shock wave pressure-time curve are obtained by means of numerical simulation and experiment. The numerical study shows that shock wave attenuation exponents are 2.10, 1.71 and 1.60, the exponents decrease with the increasing of Al/O ratio. In addition, shock wave energy is maximum when the Al/O ratio equals 0.257.
Aluminum to oxygen Al/O ratio is very important to the performance of aluminized explosives. In order to study the influence of the ratio on the performance of explosives in concrete, three kinds of aluminized explosives are taken into account, and their Al/O ratio are 0, 0.257 and 0.632, respectively. In this paper, the damaging process of concrete medium under explosion of cylindrical charge is numerically simulated using AUTODYN program. Meanwhile, within the range of relative distance from 2.5 to 10, shock wave pressure-time curve are obtained by means of numerical simulation and experiment. The numerical study shows that shock wave attenuation exponents are 2.10, 1.71 and 1.60, the exponents decrease with the increasing of Al/O ratio. In addition, shock wave energy is maximum when the Al/O ratio equals 0.257.
2015, 35(4): 520-526.
doi: 10.11883/1001-1455(2015)04-0520-07
Abstract:
To obtain the characteristics of sequential underwater explosion sound signals effectively, the sequential underwater explosion sound signals have been gradually extracted by the Mallat algorithm of wavelet transform. The energy distribution of the sequential underwater explosion sound signal at different frequency ranges was discussed by adopting the discrete wavelet transform. The Welch spectrum method had been used to extract the power spectrum characteristics of sequential underwater explosion sound signals. The time-frequency characteristic was analyzed by using the discrete wavelet transform. The results show that the sequential underwater explosion has characteristics of strong sound power, longer sound duration and wide frequency range, the sound pressure level can be more than 190 dB, the energy is mainly concentrated in area of 48 kHz, with the higher energy band in the low frequency band. These characteristics show that the sequential underwater explosion can be used as a source of sound interference. The results also show that wavelet transform can be used to study the characteristics of the sequential underwater explosion sound signals reasonably so as to analyze them accurately.
To obtain the characteristics of sequential underwater explosion sound signals effectively, the sequential underwater explosion sound signals have been gradually extracted by the Mallat algorithm of wavelet transform. The energy distribution of the sequential underwater explosion sound signal at different frequency ranges was discussed by adopting the discrete wavelet transform. The Welch spectrum method had been used to extract the power spectrum characteristics of sequential underwater explosion sound signals. The time-frequency characteristic was analyzed by using the discrete wavelet transform. The results show that the sequential underwater explosion has characteristics of strong sound power, longer sound duration and wide frequency range, the sound pressure level can be more than 190 dB, the energy is mainly concentrated in area of 48 kHz, with the higher energy band in the low frequency band. These characteristics show that the sequential underwater explosion can be used as a source of sound interference. The results also show that wavelet transform can be used to study the characteristics of the sequential underwater explosion sound signals reasonably so as to analyze them accurately.
2015, 35(4): 527-535.
doi: 10.11883/1001-1455(2015)04-0527-09
Abstract:
Two types (single-edged and double-edged) of TC4 (Ti-6Al-4V) alloy samples are tested by using the split-Hopkinson bar system under the strain rate of 104 s-1. By using ultra-high speed photography, the initialization and propagation of adiabatic shear band (ASB) are obtained with sufficient resolution. The relationship of the mechanical properties is built. The width of the shear band is observed to be 5-12 μm by using metallurgical microscope and scanning electron microscopy (SEM). Shear dimples and smooth regions are observed in the fracture surfaces as well. However, no obvious phase-transfer are detected. The double-edged samples have shown a better performance because of the relatively negligible bending during experimenting. The critical shear strain at which ASB appears is between 78%-88% and the propagation speed is estimated to be in the range of 460-1 250 m/s. It is also found that when strain rate rises, the shear bands propagate faster. Moreover, the propagation speed increases as the loading process proceeds and the speed is linearly proportional with the nominal strain rate.
Two types (single-edged and double-edged) of TC4 (Ti-6Al-4V) alloy samples are tested by using the split-Hopkinson bar system under the strain rate of 104 s-1. By using ultra-high speed photography, the initialization and propagation of adiabatic shear band (ASB) are obtained with sufficient resolution. The relationship of the mechanical properties is built. The width of the shear band is observed to be 5-12 μm by using metallurgical microscope and scanning electron microscopy (SEM). Shear dimples and smooth regions are observed in the fracture surfaces as well. However, no obvious phase-transfer are detected. The double-edged samples have shown a better performance because of the relatively negligible bending during experimenting. The critical shear strain at which ASB appears is between 78%-88% and the propagation speed is estimated to be in the range of 460-1 250 m/s. It is also found that when strain rate rises, the shear bands propagate faster. Moreover, the propagation speed increases as the loading process proceeds and the speed is linearly proportional with the nominal strain rate.
2015, 35(4): 536-540.
doi: 10.11883/1001-1455(2015)04-0536-05
Abstract:
In order to resolve the current issue about the backward method of charge and low energy efficiency of explosives, a kind of explosive with the structure of honeycomb is used to ensure the quality of the charge and is applied in double sided explosive cladding in which two plates can be combined in one explosion. A double sided explosive caldding experiment of stainless steel plates with the thickness of 3 mm and Q235 steel plates with thickness of 16 mm is carried out by using the explosive with the thickness of 7 mm. The explosive cladding window of the collision velocity is calculated as well as the collision velocity in two groups of the tests. The critical thichness of the explosive is remarkbly reduced with the explosive astricted by the honeycomb structure and the plates. The emulsion explosive with the thickness of 5 mm detonates stably. The result shows that, compared to the existing explosive cladding method, the consumption of explosives by using this method is reduced by 77% in the case of cladding the same number of combination plates. The calculation prefigure explosive cladding of stainless steel/Q235 steel exactly.
In order to resolve the current issue about the backward method of charge and low energy efficiency of explosives, a kind of explosive with the structure of honeycomb is used to ensure the quality of the charge and is applied in double sided explosive cladding in which two plates can be combined in one explosion. A double sided explosive caldding experiment of stainless steel plates with the thickness of 3 mm and Q235 steel plates with thickness of 16 mm is carried out by using the explosive with the thickness of 7 mm. The explosive cladding window of the collision velocity is calculated as well as the collision velocity in two groups of the tests. The critical thichness of the explosive is remarkbly reduced with the explosive astricted by the honeycomb structure and the plates. The emulsion explosive with the thickness of 5 mm detonates stably. The result shows that, compared to the existing explosive cladding method, the consumption of explosives by using this method is reduced by 77% in the case of cladding the same number of combination plates. The calculation prefigure explosive cladding of stainless steel/Q235 steel exactly.
2015, 35(4): 541-546.
doi: 10.11883/1001-1455(2015)04-0541-06
Abstract:
Based on the design of a profiled rod, a dynamics model was proposed for the profiled rod driven by dentonation. The motion process of the profiled rod driven by dentonation was simulated by ANSYS/LS-DYNA. The model for the profiled rod after detonation and the initial velocity were achieved. Considering the aeroelastic deformation caused by the profiled rod flying in air fluid filed, the profiled rod was regarded as a flexible body, the motion process of the profiled rod flying against air resistance was simulated by ADAMS. The computed results show that the proposed simulation method can describe the motion states of the profiled rod accurately after detonation and provide a reference for the design of the profiled rod warhead.
Based on the design of a profiled rod, a dynamics model was proposed for the profiled rod driven by dentonation. The motion process of the profiled rod driven by dentonation was simulated by ANSYS/LS-DYNA. The model for the profiled rod after detonation and the initial velocity were achieved. Considering the aeroelastic deformation caused by the profiled rod flying in air fluid filed, the profiled rod was regarded as a flexible body, the motion process of the profiled rod flying against air resistance was simulated by ADAMS. The computed results show that the proposed simulation method can describe the motion states of the profiled rod accurately after detonation and provide a reference for the design of the profiled rod warhead.
2015, 35(4): 547-554.
doi: 10.11883/1001-1455(2015)04-0547-08
Abstract:
Based on the blasting excavation for the berm at the elevation of 640 m on the high slope of Xiluodu hydropower station, the blasting induced damage zone were obtained through sonic wave test and numerical simulation. The relationship between PPV and damage scalarD was studied. If PPV is bigger than one certain value, the damage scalar D increased quickly to about 0.8, then the increased speed became slow. A method of determining critical damage PPV was put forward based on the damage degree and it was compared with the methods of statistics relationship between the maximum tensile stress and PPV and the PPV criterion based on the maximum tensile stress. Results demonstrate that the accuracy of methods based on the damage degree and statistic relationship between the maximum tensile stress and PPV is better than the result according to the maximum tensile stress.
Based on the blasting excavation for the berm at the elevation of 640 m on the high slope of Xiluodu hydropower station, the blasting induced damage zone were obtained through sonic wave test and numerical simulation. The relationship between PPV and damage scalarD was studied. If PPV is bigger than one certain value, the damage scalar D increased quickly to about 0.8, then the increased speed became slow. A method of determining critical damage PPV was put forward based on the damage degree and it was compared with the methods of statistics relationship between the maximum tensile stress and PPV and the PPV criterion based on the maximum tensile stress. Results demonstrate that the accuracy of methods based on the damage degree and statistic relationship between the maximum tensile stress and PPV is better than the result according to the maximum tensile stress.
2015, 35(4): 555-560.
doi: 10.11883/1001-1455(2015)04-0555-06
Abstract:
With Baihetan columnar joints basalt as the research object, numerical model is generated according to the local distribution statistics. Based on numerical analysis, the cracking process of columnar jointed rock masses with the slope excavated by contour blasting is simulated. The results show that the columnar joints control and lead the generation of cracking in contour blasting. The joints around the hole are firstly opened by the explosion load. Then they extend along the joints near the defiled line of holes. Finally the cracks formed by a large number of columnar joints are connected. The process of the width of pre-splitting crack is that it reduces to stabile opening after increases under the condition of pre-splitting blasting. And the range of cracks in pre-splitting blasting is larger than these in smooth blasting.
With Baihetan columnar joints basalt as the research object, numerical model is generated according to the local distribution statistics. Based on numerical analysis, the cracking process of columnar jointed rock masses with the slope excavated by contour blasting is simulated. The results show that the columnar joints control and lead the generation of cracking in contour blasting. The joints around the hole are firstly opened by the explosion load. Then they extend along the joints near the defiled line of holes. Finally the cracks formed by a large number of columnar joints are connected. The process of the width of pre-splitting crack is that it reduces to stabile opening after increases under the condition of pre-splitting blasting. And the range of cracks in pre-splitting blasting is larger than these in smooth blasting.
2015, 35(4): 561-566.
doi: 10.11883/1001-1455(2015)04-0561-06
Abstract:
Based on two-step reactive Euler equations, two-dimensional simulation of cylindrical detonation (CD) is performed. The objective is to study the influence of ignition conditions and initial pressure on the formation and propagation of CD. It is found that the new-generation of triple shock waves is the sign that CD becomes stable as it is running outwards. As long as CD could be ignited successfully, the ignition radius (curvature) decided the number and location of initial-generated triple shock waves, and the ignition pressure has little influence on them. When the ignition radius is large, the number and running radius of initial-generated triple shock waves is large as well, and long running distance is needed for CD to become stable. When the initial pressure is elevated, CD becomes stable in shorter running distance.
Based on two-step reactive Euler equations, two-dimensional simulation of cylindrical detonation (CD) is performed. The objective is to study the influence of ignition conditions and initial pressure on the formation and propagation of CD. It is found that the new-generation of triple shock waves is the sign that CD becomes stable as it is running outwards. As long as CD could be ignited successfully, the ignition radius (curvature) decided the number and location of initial-generated triple shock waves, and the ignition pressure has little influence on them. When the ignition radius is large, the number and running radius of initial-generated triple shock waves is large as well, and long running distance is needed for CD to become stable. When the initial pressure is elevated, CD becomes stable in shorter running distance.
2015, 35(4): 567-575.
doi: 10.11883/1001-1455(2015)04-0567-09
Abstract:
A split Hopkinson pressure bar apparatus (SHPB) and a modified SHPB apparatus were employed to investigate the dynamic responses of aluminum foam. During the experiments, a high-speed camera was used to record the deformation process of specimens. Three deformation patterns were observed with the increase of the impact speed. All photographs recorded were analyzed by the digital imaging correlation method. The analytical results were used to illustrate the strain field progressing and the stress nonuniformity of these three deformation patterns. And they are helpful in the revealing of the intrinsic mechanisms of these three deformation patterns. This method offers a new and reliable method to study the influence of deformation nonuniformity on dynamic mechanical behaviors of aluminum foam under different impact speeds.
A split Hopkinson pressure bar apparatus (SHPB) and a modified SHPB apparatus were employed to investigate the dynamic responses of aluminum foam. During the experiments, a high-speed camera was used to record the deformation process of specimens. Three deformation patterns were observed with the increase of the impact speed. All photographs recorded were analyzed by the digital imaging correlation method. The analytical results were used to illustrate the strain field progressing and the stress nonuniformity of these three deformation patterns. And they are helpful in the revealing of the intrinsic mechanisms of these three deformation patterns. This method offers a new and reliable method to study the influence of deformation nonuniformity on dynamic mechanical behaviors of aluminum foam under different impact speeds.
2015, 35(4): 576-584.
doi: 10.11883/1001-1455(2015)04-0576-09
Abstract:
To improve the driving speed, by taking the tunnel blasting practice in Lushuidong coal mine as research background, the optimization of cut parameters was studied by LS-DYNA3D. Underground field experiments were combined to analyze the dynamic stress, hard rock-crushed range and underground blasting effect for the hard rock cut blasting with different parameters. The average effective stress peak, along the section of the cut center from the bottom of the hole to the top, increases by over 40% when the center holes are blasted as compared with that when the center holes are not blasted. Center hole blasting plays an important role in the formation of the groove bottom. Under the same conditions, when the explosive charge in each blasting hole increases from 1.2 kg to 1.8 kg, the average effective stress peak along that section increases by only 20%, the hard rock-crushed range increase by less, and the advance per attack adds within 10% in blasting practice. Field experiments show that the cut blasting depth increases by 31%-65% with center holes blasted as compared with that without center holes under normal blasting charge condition. When the cut angle is less than 78°, the blasting footage decreases slowly with the increasing of cut angle; when the cut angle increases to 82°, the blasting footage decreases obviously with the increasing of cut angle.
To improve the driving speed, by taking the tunnel blasting practice in Lushuidong coal mine as research background, the optimization of cut parameters was studied by LS-DYNA3D. Underground field experiments were combined to analyze the dynamic stress, hard rock-crushed range and underground blasting effect for the hard rock cut blasting with different parameters. The average effective stress peak, along the section of the cut center from the bottom of the hole to the top, increases by over 40% when the center holes are blasted as compared with that when the center holes are not blasted. Center hole blasting plays an important role in the formation of the groove bottom. Under the same conditions, when the explosive charge in each blasting hole increases from 1.2 kg to 1.8 kg, the average effective stress peak along that section increases by only 20%, the hard rock-crushed range increase by less, and the advance per attack adds within 10% in blasting practice. Field experiments show that the cut blasting depth increases by 31%-65% with center holes blasted as compared with that without center holes under normal blasting charge condition. When the cut angle is less than 78°, the blasting footage decreases slowly with the increasing of cut angle; when the cut angle increases to 82°, the blasting footage decreases obviously with the increasing of cut angle.
2015, 35(4): 585-590.
doi: 10.11883/1001-1455(2015)04-0585-06
Abstract:
Aimed to simulate the propagation of blast wave with high density ratio and high pressure ratio produced by strong explosion in the air, a two dimensional numerical program is written in which the problem is treated as a two-medium compressible flow with sharp material interface in Eulerian grids. In this method, the finite volume method is used to solve the Euler equations, level set method is used to capture the moving interface, and the numerical flux across the interface is calculated by exactly solving the Riemann problem. Mesh adaption technique in triangle meshes is adopted to refine or coarsen the meshes which can both capture the peak overpressure and improve the computational efficiency. One kiloton nuclear charge of strong explosion in free air is simulated. The shock wave parameters, including peak overpressure, shock arrival time and so on, are in consistence with the point explosion theory, which show the accuracy and efficiency of the numerical methods.
Aimed to simulate the propagation of blast wave with high density ratio and high pressure ratio produced by strong explosion in the air, a two dimensional numerical program is written in which the problem is treated as a two-medium compressible flow with sharp material interface in Eulerian grids. In this method, the finite volume method is used to solve the Euler equations, level set method is used to capture the moving interface, and the numerical flux across the interface is calculated by exactly solving the Riemann problem. Mesh adaption technique in triangle meshes is adopted to refine or coarsen the meshes which can both capture the peak overpressure and improve the computational efficiency. One kiloton nuclear charge of strong explosion in free air is simulated. The shock wave parameters, including peak overpressure, shock arrival time and so on, are in consistence with the point explosion theory, which show the accuracy and efficiency of the numerical methods.
2015, 35(4): 591-598.
doi: 10.11883/1001-1455(2015)04-0591-08
Abstract:
To study the way that the plane SH wave propagating in an elastic bi-material half space from medium Ⅰ to medium Ⅱ, the steady-state scattering of the transmitted wave by a circular cavity is analyzed by using Green function and integral equation methods on complex function description. The bi-material half space is divided into a quarter space medium Ⅰ and a quarter space medium Ⅱ with a circular cavity in it. Their Green functions are constructed as anti-plane point source response problem respectively. The total displacement fields of medium Ⅰ and medium Ⅱ are formulated as two parts' vector sum. The first part is interfacial integral of interactive force multiplied by corresponding Green function. The second part is plane displacement field formed by omitting the circular cavity. Steady state solution is obtained by determining the integral equations along interface with displacement continuity. Numerical results are presented to reveal the effects of locations and material parameters on circular cavity scattering.
To study the way that the plane SH wave propagating in an elastic bi-material half space from medium Ⅰ to medium Ⅱ, the steady-state scattering of the transmitted wave by a circular cavity is analyzed by using Green function and integral equation methods on complex function description. The bi-material half space is divided into a quarter space medium Ⅰ and a quarter space medium Ⅱ with a circular cavity in it. Their Green functions are constructed as anti-plane point source response problem respectively. The total displacement fields of medium Ⅰ and medium Ⅱ are formulated as two parts' vector sum. The first part is interfacial integral of interactive force multiplied by corresponding Green function. The second part is plane displacement field formed by omitting the circular cavity. Steady state solution is obtained by determining the integral equations along interface with displacement continuity. Numerical results are presented to reveal the effects of locations and material parameters on circular cavity scattering.
2015, 35(4): 599-602.
doi: 10.11883/1001-1455(2015)04-0599-04
Abstract:
A method was raised by taking out the underwater explosion test to determin the JWL state equation parameters of detonation products. The PBX-01 explosive was applied and a calculating model of underwater explosion test was established by using ANSYS/LS-DYNA program. The JWL state equation parameters of detonation products for PBX-01 explosive were determined according to the comparison of the experimental and numerical results. Parameters determined by underwater explosion test and cylinder expansion test were used for detonation products driving water test. The results show that the underwater explosion test numerical simulation is accordant better in initial stage. Specially appointed patameters need to be established in the underwater explosions.
A method was raised by taking out the underwater explosion test to determin the JWL state equation parameters of detonation products. The PBX-01 explosive was applied and a calculating model of underwater explosion test was established by using ANSYS/LS-DYNA program. The JWL state equation parameters of detonation products for PBX-01 explosive were determined according to the comparison of the experimental and numerical results. Parameters determined by underwater explosion test and cylinder expansion test were used for detonation products driving water test. The results show that the underwater explosion test numerical simulation is accordant better in initial stage. Specially appointed patameters need to be established in the underwater explosions.
2015, 35(4): 603-608.
doi: 10.11883/1001-1455(2015)04-0603-06
Abstract:
Detonation tube including driver section and test section was built to investigate the failure mechanism of detonation wave near the limits. The mixture of C2H2+2.5O2+70%Ar was investigated experimentally. Fiber optics was used to measure detonation velocity. Smocked foils were used to record the detonation cellular structure. The results show that, with the initial pressure far lager than the critical pressure, detonation wave propagates at a constant value in the tubes. Detonation velocity decreases with the decreasing initial pressure. With a given initial pressure, the detonation velocity decreased as the tube diameter (or channel interval) decreased. Under the critical pressure, the detonation velocity propagated a short distance in the tubes and then decreased gradually until complete failure. For different geometries tubes and channels, by introducing dimensionless parameter d /λ and w/λ (d the dameter of the round tube, w the interval of the annular channel and λ the size of detonation cellular), the results show that the critical thickness is half of the critical diameter. Good agreement is found between the experimental measurements in both geometries which supports this conclusion and theoretical mode. The failure mechanisms based on the detonation front curvature for stable detonation in mixtures that are highly argon diluted are well defined.
Detonation tube including driver section and test section was built to investigate the failure mechanism of detonation wave near the limits. The mixture of C2H2+2.5O2+70%Ar was investigated experimentally. Fiber optics was used to measure detonation velocity. Smocked foils were used to record the detonation cellular structure. The results show that, with the initial pressure far lager than the critical pressure, detonation wave propagates at a constant value in the tubes. Detonation velocity decreases with the decreasing initial pressure. With a given initial pressure, the detonation velocity decreased as the tube diameter (or channel interval) decreased. Under the critical pressure, the detonation velocity propagated a short distance in the tubes and then decreased gradually until complete failure. For different geometries tubes and channels, by introducing dimensionless parameter d /λ and w/λ (d the dameter of the round tube, w the interval of the annular channel and λ the size of detonation cellular), the results show that the critical thickness is half of the critical diameter. Good agreement is found between the experimental measurements in both geometries which supports this conclusion and theoretical mode. The failure mechanisms based on the detonation front curvature for stable detonation in mixtures that are highly argon diluted are well defined.
