2016 Vol. 36, No. 5
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2016, 36(5): 577-582.
doi: 10.11883/1001-1455(2016)05-0577-06
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Abstract:
In this work we carried out experimental and 3D numerical study of cellular structure of detonation propagating in an annular tube. Detonation cellular patterns were recorded using a smoked foil. Based on the 3D reactive Euler equations with the one-step irreversible Arrhenius kinetics model, detonation propagation of hydrogen/air mixture in an annular tube was investigated numerically. Fifth-order weighted essentially non-oscillatory (WENO) scheme and third-order TVD Runge-Kutta were used to discretize the spatial derivatives and the time term, respectively. Moreover, parallel technology was also adopted. The results indicate that the outer wall of the annular tube is the convergent wall, which reduces the cell sizes of the outer wall and makes it more uniform due to its compression. However, the inner wall of the annular tube is the divergent wall, which enlarges the cell sizes of the inner wall and leads to its periodical variation due to its expansion. Simultaneously, slapping waves appear in all the tube walls and its shape is a bent line.
In this work we carried out experimental and 3D numerical study of cellular structure of detonation propagating in an annular tube. Detonation cellular patterns were recorded using a smoked foil. Based on the 3D reactive Euler equations with the one-step irreversible Arrhenius kinetics model, detonation propagation of hydrogen/air mixture in an annular tube was investigated numerically. Fifth-order weighted essentially non-oscillatory (WENO) scheme and third-order TVD Runge-Kutta were used to discretize the spatial derivatives and the time term, respectively. Moreover, parallel technology was also adopted. The results indicate that the outer wall of the annular tube is the convergent wall, which reduces the cell sizes of the outer wall and makes it more uniform due to its compression. However, the inner wall of the annular tube is the divergent wall, which enlarges the cell sizes of the inner wall and leads to its periodical variation due to its expansion. Simultaneously, slapping waves appear in all the tube walls and its shape is a bent line.
2016, 36(5): 583-589.
doi: 10.11883/1001-1455(2016)05-0583-07
Abstract:
In this work, taking into account of the interference of random cracks in the expansion process, we designed a cylindrical sample made with a preset hole. Then, using the Doppler pins system (DPS), we obtained some better curves for the cylinder's radial speed histories. Based on the non-constant strain rate phenomena in the expanding ring and expanding cylinder experiments, we conducted experiments and studied a method for obtaining constitutive equation at constant strain rate. The improved constitutive equation method was used to obtain the modified constitutive equation at constant strain rate for 20 steel.
In this work, taking into account of the interference of random cracks in the expansion process, we designed a cylindrical sample made with a preset hole. Then, using the Doppler pins system (DPS), we obtained some better curves for the cylinder's radial speed histories. Based on the non-constant strain rate phenomena in the expanding ring and expanding cylinder experiments, we conducted experiments and studied a method for obtaining constitutive equation at constant strain rate. The improved constitutive equation method was used to obtain the modified constitutive equation at constant strain rate for 20 steel.
2016, 36(5): 590-595.
doi: 10.11883/1001-1455(2016)05-0590-06
Abstract:
Under an explosive load a jet, composed by the local melted metal, would be generated and ejected from the crack of a metal plate, whose velocity may reach several kilometers per second while whose mass can only reach several milligrams per centimeter in magnitude. In the present work, high-speed photography and pulse soft X-ray radiography were used to diagnose the jet in the crack for its dynamic behavior and qualitative and quantitative measurement. A series of experiments were conducted considering different factors which include the plate material, the pressure and mode of the explosive load, the width of the crack, and the data of the jet properties and the jet mass were obtained. Based on the analysis of the experiment data, an empirical model was proposed which characterizes the jet mass varying with those different factors.
Under an explosive load a jet, composed by the local melted metal, would be generated and ejected from the crack of a metal plate, whose velocity may reach several kilometers per second while whose mass can only reach several milligrams per centimeter in magnitude. In the present work, high-speed photography and pulse soft X-ray radiography were used to diagnose the jet in the crack for its dynamic behavior and qualitative and quantitative measurement. A series of experiments were conducted considering different factors which include the plate material, the pressure and mode of the explosive load, the width of the crack, and the data of the jet properties and the jet mass were obtained. Based on the analysis of the experiment data, an empirical model was proposed which characterizes the jet mass varying with those different factors.
2016, 36(5): 596-602.
doi: 10.11883/1001-1455(2016)05-0596-07
Abstract:
In the present study, with a view to solve the spallation of ductile metal under intense dynamic loading, we develop a new void coalescence criterion accounting for the damage and void geometry based on the geometric relationship between voids. Following the principle of energy conservation, we reveal the physical mechanism explaining the influence of void coalescence on the growth of damage. The comparison between calculated results and experiment data indicates that void coalescence leads to rapid growth of damage, reduction of void numbers, and increase of average void size.
In the present study, with a view to solve the spallation of ductile metal under intense dynamic loading, we develop a new void coalescence criterion accounting for the damage and void geometry based on the geometric relationship between voids. Following the principle of energy conservation, we reveal the physical mechanism explaining the influence of void coalescence on the growth of damage. The comparison between calculated results and experiment data indicates that void coalescence leads to rapid growth of damage, reduction of void numbers, and increase of average void size.
2016, 36(5): 603-610.
doi: 10.11883/1001-1455(2016)05-0603-08
Abstract:
In the present work we studied the detonation of Al-RDX suspended in air using CE/SE. The two-phase detonation process of two dusts with different density were simulated and the effects of different particle density on the detonation wave speed and pressure were investigated. It was found that there is a linear relationship between the density ratio and the wave speed and pressure. The flow field evolution of the two dusts detonation in a complex channel was discussed. Compared with the single dust detonation, the detonation wave speed, pressure, and temperature of the two dusts detonation were obviously higher. It is shown that CE/SE is an ideal method at present to simulate the two dusts detonation and can provide useful reference for multi-dust detonation study.
In the present work we studied the detonation of Al-RDX suspended in air using CE/SE. The two-phase detonation process of two dusts with different density were simulated and the effects of different particle density on the detonation wave speed and pressure were investigated. It was found that there is a linear relationship between the density ratio and the wave speed and pressure. The flow field evolution of the two dusts detonation in a complex channel was discussed. Compared with the single dust detonation, the detonation wave speed, pressure, and temperature of the two dusts detonation were obviously higher. It is shown that CE/SE is an ideal method at present to simulate the two dusts detonation and can provide useful reference for multi-dust detonation study.
2016, 36(5): 611-616.
doi: 10.11883/1001-1455(2016)05-0611-06
Abstract:
In order to study the throw characteristics of rock debris after explosion, with a view of solving complicated problems involved in the two-phase gas-solid flow in a penetration channel, we propose a simulation scheme combining the use of FLUENT and EDEM softwares. Based on this scheme, we analyzed the medium debris's blasting process for different depth-diameter ratios and studied the factors that bear on the debris's transporting characteristics. The results show that debris transporting capability is directly proportional to the peak value of the explosion load, and is inversely proportional to the ratio of the channel depth to the channel diameter and the debris particle size.
In order to study the throw characteristics of rock debris after explosion, with a view of solving complicated problems involved in the two-phase gas-solid flow in a penetration channel, we propose a simulation scheme combining the use of FLUENT and EDEM softwares. Based on this scheme, we analyzed the medium debris's blasting process for different depth-diameter ratios and studied the factors that bear on the debris's transporting characteristics. The results show that debris transporting capability is directly proportional to the peak value of the explosion load, and is inversely proportional to the ratio of the channel depth to the channel diameter and the debris particle size.
2016, 36(5): 617-624.
doi: 10.11883/1001-1455(2016)05-0617-08
Abstract:
In this paper, the dynamic deformation and failure mode of 5A06 aluminum alloy clamped air-backed circular panels with two different thicknesses subjected to underwater shock loading were investigated using the non-explosive underwater shock loading device in combination with high-speed photography. The dynamic response history of the target panels was observed with more information about their failure modes obtained, and three modes of deformation and failure were identified, i. e. Mode Ⅰ (large plastic deformation), Mode Ⅱ (tensile tearing) and Mode Ⅲ (shear-off failure). According to the experimental results, the performance of four kinds of failure criteria (i. e. shock wave pressure, impulsive factor, damage parameter, and response parameter) on predicting the failure modes of the target panels was compared and analyzed. The experimental results showed that the damage and failure of underwater structures can be more comprehensively judged by taking account of the damage parameter and the response parameter of the target.
In this paper, the dynamic deformation and failure mode of 5A06 aluminum alloy clamped air-backed circular panels with two different thicknesses subjected to underwater shock loading were investigated using the non-explosive underwater shock loading device in combination with high-speed photography. The dynamic response history of the target panels was observed with more information about their failure modes obtained, and three modes of deformation and failure were identified, i. e. Mode Ⅰ (large plastic deformation), Mode Ⅱ (tensile tearing) and Mode Ⅲ (shear-off failure). According to the experimental results, the performance of four kinds of failure criteria (i. e. shock wave pressure, impulsive factor, damage parameter, and response parameter) on predicting the failure modes of the target panels was compared and analyzed. The experimental results showed that the damage and failure of underwater structures can be more comprehensively judged by taking account of the damage parameter and the response parameter of the target.
2016, 36(5): 625-632.
doi: 10.11883/1001-1455(2016)05-0625-08
Abstract:
In this work, to investigate the penetration performance of a projectile into pre-drilled targets, we proposed and improved a penetration model of an oval-nosed projectile penetrating into the pre-drilled target using the conical pre-drilling assumption and coulomb friction model for analyzing the hole drilling/reaming versus the penetration depth and stabilization of the projectile. The analytic model was verified with tests of the projectile penetrating targets made from brittle and elastic-plastic targets. The results from our improved model are fairly consistent with those from the tests. In the case of a cylindrical hole, the impact velocity, CRH and the cavity/radius ratio are in direct proportion to the projectile's penetrating depth into a pre-drilled target. Withe same volume of the penetration, the angle of the conical hole and the relative has a great influence on the penetration depth, and the greater the angle, the weaker the degree to which CRH affects the penetration performance.
In this work, to investigate the penetration performance of a projectile into pre-drilled targets, we proposed and improved a penetration model of an oval-nosed projectile penetrating into the pre-drilled target using the conical pre-drilling assumption and coulomb friction model for analyzing the hole drilling/reaming versus the penetration depth and stabilization of the projectile. The analytic model was verified with tests of the projectile penetrating targets made from brittle and elastic-plastic targets. The results from our improved model are fairly consistent with those from the tests. In the case of a cylindrical hole, the impact velocity, CRH and the cavity/radius ratio are in direct proportion to the projectile's penetrating depth into a pre-drilled target. Withe same volume of the penetration, the angle of the conical hole and the relative has a great influence on the penetration depth, and the greater the angle, the weaker the degree to which CRH affects the penetration performance.
2016, 36(5): 633-639.
doi: 10.11883/1001-1455(2016)05-0633-07
Abstract:
In the present work, a testing system consisting of three detonation tubes was designed in a regular triangle to investigate the noise characteristics of a three-tube PDE system and their formation mechanism. The distance between each tube and the central axis is 200 mm. The directivity of acoustic emissions is measured using a circular array of four transducers (0°, 30°, 60°, and 90°) at various radial distances. Results show that all the max peak pressures appear in the directivity of 30°. The referential radius of the detonation noise is three times that of the "nominal tube diameter". The duration of A time decreases almost linearly along with the increase of r (the distance to the nominal "central point" of the three detonation tubes), and also decreases with the increase of the angle. The duration of B time is inversely proportional to the noise amplitude, and increases with the increase of the axial distance. At different angles, the greater the peak pressure, the smaller the duration of B time.
In the present work, a testing system consisting of three detonation tubes was designed in a regular triangle to investigate the noise characteristics of a three-tube PDE system and their formation mechanism. The distance between each tube and the central axis is 200 mm. The directivity of acoustic emissions is measured using a circular array of four transducers (0°, 30°, 60°, and 90°) at various radial distances. Results show that all the max peak pressures appear in the directivity of 30°. The referential radius of the detonation noise is three times that of the "nominal tube diameter". The duration of A time decreases almost linearly along with the increase of r (the distance to the nominal "central point" of the three detonation tubes), and also decreases with the increase of the angle. The duration of B time is inversely proportional to the noise amplitude, and increases with the increase of the axial distance. At different angles, the greater the peak pressure, the smaller the duration of B time.
2016, 36(5): 640-647.
doi: 10.11883/1001-1455(2016)05-0640-08
Abstract:
In this work, using a 5083 aluminum alloy plate (4 mm×410 mm×410 mm) and a Q345 steel plate with dovetail grooves (15 mm×400 mm×400 mm) as the flyer and base plates, and based on the lower limit of explosive welding of aluminum alloy with steel calculated from theoretical formulas, we carried out explosive welding experiments with selected parameters which were close to the lower limit. We studied the bonding performances on the interfaces of the 5083/Q345 clad plate by checking its mechanical properties and observing its micro-structure. The results show that the explosive welding of aluminum alloy and steel is achieved through a combined action of the metallurgical bonding and the extraction and meshing of the dovetail grooves; the bonding interface between the aluminum alloy and the upper, lower and inclined surfaces of the dovetail grooves exhibits an even shape; the welding between the aluminum alloy and the upper and lower surfaces of the dovetail grooves is realized by both direct bonding and discontinuous melting while that between the aluminum alloy and the inclined surface of the dovetail grooves is realized by continuous melting. The tensile shear strength of the clad plate is greater than 172 MPa, which satisfies the requirement placed on the bonding strength of a Al/Fe clad plate.
In this work, using a 5083 aluminum alloy plate (4 mm×410 mm×410 mm) and a Q345 steel plate with dovetail grooves (15 mm×400 mm×400 mm) as the flyer and base plates, and based on the lower limit of explosive welding of aluminum alloy with steel calculated from theoretical formulas, we carried out explosive welding experiments with selected parameters which were close to the lower limit. We studied the bonding performances on the interfaces of the 5083/Q345 clad plate by checking its mechanical properties and observing its micro-structure. The results show that the explosive welding of aluminum alloy and steel is achieved through a combined action of the metallurgical bonding and the extraction and meshing of the dovetail grooves; the bonding interface between the aluminum alloy and the upper, lower and inclined surfaces of the dovetail grooves exhibits an even shape; the welding between the aluminum alloy and the upper and lower surfaces of the dovetail grooves is realized by both direct bonding and discontinuous melting while that between the aluminum alloy and the inclined surface of the dovetail grooves is realized by continuous melting. The tensile shear strength of the clad plate is greater than 172 MPa, which satisfies the requirement placed on the bonding strength of a Al/Fe clad plate.
2016, 36(5): 648-654.
doi: 10.11883/1001-1455(2016)05-0648-07
Abstract:
The impact fracture process of the magnalium alloy structure was investigated using the XFEM-based cohesive model. First, by the numerical modeling carried out in abaqus software based on XFEM, the fracture mode of magnalium alloy specimens at different bullet impact velocities were obtained from doing a three-point bending experiment. After this, the impact fracture process of experimental model under three different loads at respectively three bullet impact velocities of 12.2, 15.1 and 26.3 m/s was simulated using the XFEM, and the alloy's failure pattern was obtained by performing numerical calculation, the results from which are consistent with those obtained from the experimental. The simulation results show that Mode Ⅰ is the major fracture mode of the specimen, and the crack propagates mostly along the initial crack direction. The crack makes a turn at a point 3~4 mm from the impacted part of the specimen, where the fixed fracture mode is dominant. This agrees with both the experimental results presented in this paper and with the calculated results found in the related literature. Finally, the reason for the fixed fracture mode in the specimen was also analyzed in the paper.
The impact fracture process of the magnalium alloy structure was investigated using the XFEM-based cohesive model. First, by the numerical modeling carried out in abaqus software based on XFEM, the fracture mode of magnalium alloy specimens at different bullet impact velocities were obtained from doing a three-point bending experiment. After this, the impact fracture process of experimental model under three different loads at respectively three bullet impact velocities of 12.2, 15.1 and 26.3 m/s was simulated using the XFEM, and the alloy's failure pattern was obtained by performing numerical calculation, the results from which are consistent with those obtained from the experimental. The simulation results show that Mode Ⅰ is the major fracture mode of the specimen, and the crack propagates mostly along the initial crack direction. The crack makes a turn at a point 3~4 mm from the impacted part of the specimen, where the fixed fracture mode is dominant. This agrees with both the experimental results presented in this paper and with the calculated results found in the related literature. Finally, the reason for the fixed fracture mode in the specimen was also analyzed in the paper.
2016, 36(5): 655-662.
doi: 10.11883/1001-1455(2016)05-0655-08
Abstract:
In this work, by accurately measuring the bullet speed of the Hopkinson bar, we succeeded in the dynamic calibration of the PVDF pressure sensor. The test data obtained have a good linearity and a deviation below 1.9%. The coefficient value K of dynamic sensitivity is 32.83 pC/N. By applying a blast loading of 500 g TNT to the composite structure of "steel-aluminum foam-steel", the propagation of the stress wave between its components was measured. The results show that the voltage signal can accurately represent the loading time and the propagation velocity of the elastic wave and plastic wave and the PVDF dynamic response of elastic stress wave with high-frequency signal is sensitive and accurate, with only a relative deviation of less than 3.5% from the theoretical data. The measured propagation velocity of the plastic wave in the aluminum foam is 590 m/s, the transmission coefficient of the plastic wave in A1-B1 interface is 0.53, which is much higher than that of the elastic wave. Special remarks were made concerning the unusual phenomena observed in the stress curve based upon our understanding of the mechanism, providing a reference for relevant explosion tests.
In this work, by accurately measuring the bullet speed of the Hopkinson bar, we succeeded in the dynamic calibration of the PVDF pressure sensor. The test data obtained have a good linearity and a deviation below 1.9%. The coefficient value K of dynamic sensitivity is 32.83 pC/N. By applying a blast loading of 500 g TNT to the composite structure of "steel-aluminum foam-steel", the propagation of the stress wave between its components was measured. The results show that the voltage signal can accurately represent the loading time and the propagation velocity of the elastic wave and plastic wave and the PVDF dynamic response of elastic stress wave with high-frequency signal is sensitive and accurate, with only a relative deviation of less than 3.5% from the theoretical data. The measured propagation velocity of the plastic wave in the aluminum foam is 590 m/s, the transmission coefficient of the plastic wave in A1-B1 interface is 0.53, which is much higher than that of the elastic wave. Special remarks were made concerning the unusual phenomena observed in the stress curve based upon our understanding of the mechanism, providing a reference for relevant explosion tests.
2016, 36(5): 663-669.
doi: 10.11883/1001-1455(2016)05-0663-07
Abstract:
In this work, to find out the formation mechanism of rock's initial damaged zone under explosive impact effect and investigate the main factors contributing to the initial damaged zone (including the crushed zone and the initial fractured zone) around the oil well, we analyzed the impact failure mode of rock and its response to loading rates by conducting impact failure experiments at different loading rates on two rock samples. With the help of the computational model of the crushed and initial fractured zone based on Von Mise, it is feasible to determine the the size of the crushed zone and the initial fractured zone according to the stress distribution generated by the peak pressure, when the rock crushes at a given loading rate (less than 190 GPa/s). The crushed zone and and the fractured zone are generated mainly in parts of the rock close to the oil well where explosive fractures occur. The diameter of the crushed zone and that of the initial fractured zone is 1~3 and 5~7 times that of the oil-well, respectively. The initial damaged zone is in direct proportion to the brittleness and the loading rate under loading impact and is more strongly influenced by the index of brittleness. The present work deepens the current understanding of the damage mode and main contributing factors of explosive fracture and provides guidance for the design of impact condition involving explosive fracture.
In this work, to find out the formation mechanism of rock's initial damaged zone under explosive impact effect and investigate the main factors contributing to the initial damaged zone (including the crushed zone and the initial fractured zone) around the oil well, we analyzed the impact failure mode of rock and its response to loading rates by conducting impact failure experiments at different loading rates on two rock samples. With the help of the computational model of the crushed and initial fractured zone based on Von Mise, it is feasible to determine the the size of the crushed zone and the initial fractured zone according to the stress distribution generated by the peak pressure, when the rock crushes at a given loading rate (less than 190 GPa/s). The crushed zone and and the fractured zone are generated mainly in parts of the rock close to the oil well where explosive fractures occur. The diameter of the crushed zone and that of the initial fractured zone is 1~3 and 5~7 times that of the oil-well, respectively. The initial damaged zone is in direct proportion to the brittleness and the loading rate under loading impact and is more strongly influenced by the index of brittleness. The present work deepens the current understanding of the damage mode and main contributing factors of explosive fracture and provides guidance for the design of impact condition involving explosive fracture.
2016, 36(5): 670-679.
doi: 10.11883/1001-1455(2016)05-0670-10
Abstract:
In this paper, to study preventive ways against incidents involving the impact of steel plate concrete (SC) structures, the steel plate concrete (SC) walls composed of surface steel plates, tie-bars, shear studs and concretes were selected as the object of investigation. The impact analysis of the walls was performed using ANSYS/LS-DYNA, the FEM code, based on the force vs. time-history analysis, in which a series of numerical sensitivity studies were conducted to evaluate the effect of several parameters affecting the behavior of the SC wall. These parameters include the thickness of the wall, the thickness of the steel plate, and the diameter and space of tie bars. The results show that they all have an effect on the impact resistance of the SC wall. This is especially true with the thickness of the wall and the steel plate, and the spacing distance between the tie bars. These studies will serve as guidance and reference for the design of SC structures that are to be used in nuclear power plant buildings.
In this paper, to study preventive ways against incidents involving the impact of steel plate concrete (SC) structures, the steel plate concrete (SC) walls composed of surface steel plates, tie-bars, shear studs and concretes were selected as the object of investigation. The impact analysis of the walls was performed using ANSYS/LS-DYNA, the FEM code, based on the force vs. time-history analysis, in which a series of numerical sensitivity studies were conducted to evaluate the effect of several parameters affecting the behavior of the SC wall. These parameters include the thickness of the wall, the thickness of the steel plate, and the diameter and space of tie bars. The results show that they all have an effect on the impact resistance of the SC wall. This is especially true with the thickness of the wall and the steel plate, and the spacing distance between the tie bars. These studies will serve as guidance and reference for the design of SC structures that are to be used in nuclear power plant buildings.
2016, 36(5): 680-687.
doi: 10.11883/1001-1455(2016)05-0680-08
Abstract:
Gasoline-air, being composed of combustible components, is apt to brings about explosion accidents. In order to study the laws governing its venting explosion in a confined space, we carried out visualization experiments on a single pore and double pores laterally situated along the shell of a cylindrical pipeline with different gasoline-air volume fractions, obtained some flame characteristics of outflow field and regularities of explosion overpressure for the pipeline's internal and external flow, and found out the four stages of the venting explosion including the flam eventing from the pore, the mushroom-cloud forming, the gradual violent burning and extinguishing. Through a comparative analysis of the data of explosion overpressure, we found that the external maximum overpressure of the double pores was several times larger than that of the single pore, and that the farther away from the ignition end, the bigger the maximum overpressure of the internal flow field.
Gasoline-air, being composed of combustible components, is apt to brings about explosion accidents. In order to study the laws governing its venting explosion in a confined space, we carried out visualization experiments on a single pore and double pores laterally situated along the shell of a cylindrical pipeline with different gasoline-air volume fractions, obtained some flame characteristics of outflow field and regularities of explosion overpressure for the pipeline's internal and external flow, and found out the four stages of the venting explosion including the flam eventing from the pore, the mushroom-cloud forming, the gradual violent burning and extinguishing. Through a comparative analysis of the data of explosion overpressure, we found that the external maximum overpressure of the double pores was several times larger than that of the single pore, and that the farther away from the ignition end, the bigger the maximum overpressure of the internal flow field.
2016, 36(5): 688-694.
doi: 10.11883/1001-1455(2016)05-0688-07
Abstract:
In this artical, firstly, estimation method of flame combustion regime of the oil-gas explosion was discussed and three oil-gas explosion experiments under the conditions of low, middle and high initial gas vapor concentration were carried out, and then the Damköhler number and the turbulent Reynolds number for the early, interim and late stage of the oil-gas explosion at low, middle and high initial gas vapor concentration conditions were calculated according to the experimental data. Finally, through the Damköhler number vs. Reynolds number diagram, the combustion regimes for each stage of the oil-gas explosion at low, middle and high initial gas vapor concentration conditions were quantitative estimated. Results show that the combustions at early, interim and late stage of the gas-air explosion under the conditions of low, middle and high initial gas vapor concentration in the tube have the same regime of flameletes-in-eddies. The conclusions of this paper can provide some useful reference for the further study of combustion regime and the numerical analysis model selection of the gas-oil explosion.
In this artical, firstly, estimation method of flame combustion regime of the oil-gas explosion was discussed and three oil-gas explosion experiments under the conditions of low, middle and high initial gas vapor concentration were carried out, and then the Damköhler number and the turbulent Reynolds number for the early, interim and late stage of the oil-gas explosion at low, middle and high initial gas vapor concentration conditions were calculated according to the experimental data. Finally, through the Damköhler number vs. Reynolds number diagram, the combustion regimes for each stage of the oil-gas explosion at low, middle and high initial gas vapor concentration conditions were quantitative estimated. Results show that the combustions at early, interim and late stage of the gas-air explosion under the conditions of low, middle and high initial gas vapor concentration in the tube have the same regime of flameletes-in-eddies. The conclusions of this paper can provide some useful reference for the further study of combustion regime and the numerical analysis model selection of the gas-oil explosion.
2016, 36(5): 695-702.
doi: 10.11883/1001-1455(2016)05-0695-08
Abstract:
During the tunneling construction in hard granite strata utilizing shield machines, pretreatment of boulders by blasting was commonly used to prevent the abrading cutter from serious damages and reduce construction risks, but the explosive consumption was usually determined based on empirical formula, resulting in that the blasting effect was often far from satisfactory. In the present work, aiming to meet the special requirement that rock fragments from the blasting should be less than 30 cm in practice, we investigate the explosive consumption using a model test of blasting. The results show that the explosive consumption of land blasting is 5.4-6.5 times that of conventional blasting when the requirement of rock fragmentation is satisfied; the explosive consumption increases linearly with the depth of overlying stratum; and the explosive consumption of model test was 3.4-4.9 times that of the empirical formula. Thus, the revised empirical formula is derived and proved valid based on the on-the-site practice. The revised formula can serve as calculation basis and reference value for similar projects of tunneling construction.
During the tunneling construction in hard granite strata utilizing shield machines, pretreatment of boulders by blasting was commonly used to prevent the abrading cutter from serious damages and reduce construction risks, but the explosive consumption was usually determined based on empirical formula, resulting in that the blasting effect was often far from satisfactory. In the present work, aiming to meet the special requirement that rock fragments from the blasting should be less than 30 cm in practice, we investigate the explosive consumption using a model test of blasting. The results show that the explosive consumption of land blasting is 5.4-6.5 times that of conventional blasting when the requirement of rock fragmentation is satisfied; the explosive consumption increases linearly with the depth of overlying stratum; and the explosive consumption of model test was 3.4-4.9 times that of the empirical formula. Thus, the revised empirical formula is derived and proved valid based on the on-the-site practice. The revised formula can serve as calculation basis and reference value for similar projects of tunneling construction.
2016, 36(5): 703-709.
doi: 10.11883/1001-1455(2016)05-0703-07
Abstract:
Duration of blasting vibration and delayed time interval of millisecond blasting are respectively an important indicator for assessing and controlling blasting hazards. It is therefore of great necessity to explore the factors that may influence the duration and the ways that can optimize the interval. In the present work, combined with dimensional analysis, we examined the factors influencing the duration arrived at a formula for predicting the blasting vibration duration, whose linear correlation reached 89.7%. Based on the linear superposition theory of seismic wave, the reasonable range of delayed time interval with different distances between the blasting source and the measuring point was obtained using MATLAB7.0. The result shows that there is close correlation between the signal energy and the duration of blasting vibration, the accuracy of prediction can be improved by introducing the signal energy into the predictive formula, the duration is negatively related to the proportional velocity and positively related to the proportional charge weight, and the reasonable range of the delayed time interval between the blasting holes is not always a specific value but may be one or more time intervals, which are determined by different distances between the explosion source and the measuring point. The application of the formula in actual engineering shows that our predictive formula and optimization for millisecond blasting are highly practicable.
Duration of blasting vibration and delayed time interval of millisecond blasting are respectively an important indicator for assessing and controlling blasting hazards. It is therefore of great necessity to explore the factors that may influence the duration and the ways that can optimize the interval. In the present work, combined with dimensional analysis, we examined the factors influencing the duration arrived at a formula for predicting the blasting vibration duration, whose linear correlation reached 89.7%. Based on the linear superposition theory of seismic wave, the reasonable range of delayed time interval with different distances between the blasting source and the measuring point was obtained using MATLAB7.0. The result shows that there is close correlation between the signal energy and the duration of blasting vibration, the accuracy of prediction can be improved by introducing the signal energy into the predictive formula, the duration is negatively related to the proportional velocity and positively related to the proportional charge weight, and the reasonable range of the delayed time interval between the blasting holes is not always a specific value but may be one or more time intervals, which are determined by different distances between the explosion source and the measuring point. The application of the formula in actual engineering shows that our predictive formula and optimization for millisecond blasting are highly practicable.
2016, 36(5): 710-714.
doi: 10.11883/1001-1455(2016)05-0710-05
Abstract:
Impact load is applicable to material science and engineering. With the research development, there is a higher requirement for the impacting velocity and energy, which are however beyond what the drop hammer can achieve. High-power pulse current can therefore be utilized to set up an intense pulsed magnetic field, and then high-power pulsed electromagnetic force (EMF) can be generated with proper equipments and converted to the impact load desired. In the present work we simulated the generation of the impact load driven by high-power electromagnetic force. The simulation results of high-power pulsed magnetic field, EMF and the punch movement process were obtained through numerical modeling. The high speed photography was used to record the movement of the compressing impact device. Through the image processing, the value of the impact velocity and impact energy is obtained that verified the simulation results.
Impact load is applicable to material science and engineering. With the research development, there is a higher requirement for the impacting velocity and energy, which are however beyond what the drop hammer can achieve. High-power pulse current can therefore be utilized to set up an intense pulsed magnetic field, and then high-power pulsed electromagnetic force (EMF) can be generated with proper equipments and converted to the impact load desired. In the present work we simulated the generation of the impact load driven by high-power electromagnetic force. The simulation results of high-power pulsed magnetic field, EMF and the punch movement process were obtained through numerical modeling. The high speed photography was used to record the movement of the compressing impact device. Through the image processing, the value of the impact velocity and impact energy is obtained that verified the simulation results.
2016, 36(5): 715-720.
doi: 10.11883/1001-1455(2016)05-0715-06
Abstract:
Graphite intercalation compounds (GICs) can be obtained when graphite is placed in strong oxidizing acids. Using this characteristic, we prepare liquid explosive by putting natural graphite in strong HNO3 and mixing it with CH3NO2. Then we poured the mixture into a plastic container and placed the container at the center of a detonation reactor to ignite the explosive mixture. After the detonation, we collected and analyzed the soot by XRD, EDX, SEM, TEM, Raman spectroscopy, the specific surface area and porosity analyzer. Results indicate that the prepared grapheme possesses perfect crystal properties and exhibits a structure of thin sheets, with a specific surface area 9.16 times that of natural graphite and an average thickness of about 14.73 nm.
Graphite intercalation compounds (GICs) can be obtained when graphite is placed in strong oxidizing acids. Using this characteristic, we prepare liquid explosive by putting natural graphite in strong HNO3 and mixing it with CH3NO2. Then we poured the mixture into a plastic container and placed the container at the center of a detonation reactor to ignite the explosive mixture. After the detonation, we collected and analyzed the soot by XRD, EDX, SEM, TEM, Raman spectroscopy, the specific surface area and porosity analyzer. Results indicate that the prepared grapheme possesses perfect crystal properties and exhibits a structure of thin sheets, with a specific surface area 9.16 times that of natural graphite and an average thickness of about 14.73 nm.
2016, 36(5): 721-727.
doi: 10.11883/1001-1455(2016)05-0721-07
Abstract:
To investigate the working conditions of a missile in a high-impact environment, this paper presents a design scheme for low-power consuming and high-overload testing system based on an MEMS apiezoresistive sensor. The system is capable of withstanding tests with a 2×105g overloaded impact and possesses such characteristics as a high sampling rate, a small volume, and a low-power consumption. As validated by our targeting experiments, the system was able not only to withstand a high overloaded impact but also to accurately capture the slight variations of a weak signal, which ensures the accuracy of the data recorded by the missile in flight.
To investigate the working conditions of a missile in a high-impact environment, this paper presents a design scheme for low-power consuming and high-overload testing system based on an MEMS apiezoresistive sensor. The system is capable of withstanding tests with a 2×105g overloaded impact and possesses such characteristics as a high sampling rate, a small volume, and a low-power consumption. As validated by our targeting experiments, the system was able not only to withstand a high overloaded impact but also to accurately capture the slight variations of a weak signal, which ensures the accuracy of the data recorded by the missile in flight.
2016, 36(5): 728-733.
doi: 10.11883/1001-1455(2016)05-0728-06
Abstract:
In this work, we investigated the process of penetration and energy release of the impact initiated projectile was investigated using numerical simulation, verified the superiority of the coupling of smooth particle hydrodynamics (SPH) with finite element method (FEM) in impact initiation, and obtained pressure-time curves for the projectile's hot-point pressure growth in different operating conditions by analyzing its bullet core's different head shapes, diameters and materials. Our simulation results show that, for a given bullet core's diameter, the shorter the bullet head's spike length, the more reduced the initiation time for the explosives' hot-point growth; for a given bullet core's length, a reduced bullet core's diameter will lead to a reduced hot-point growth time; and bullet cores made from steel show greater advantage at delay initiation time over those made from tungsten alloy. The simulated effects of target penetration are fairly consistent with those from experimental results.
In this work, we investigated the process of penetration and energy release of the impact initiated projectile was investigated using numerical simulation, verified the superiority of the coupling of smooth particle hydrodynamics (SPH) with finite element method (FEM) in impact initiation, and obtained pressure-time curves for the projectile's hot-point pressure growth in different operating conditions by analyzing its bullet core's different head shapes, diameters and materials. Our simulation results show that, for a given bullet core's diameter, the shorter the bullet head's spike length, the more reduced the initiation time for the explosives' hot-point growth; for a given bullet core's length, a reduced bullet core's diameter will lead to a reduced hot-point growth time; and bullet cores made from steel show greater advantage at delay initiation time over those made from tungsten alloy. The simulated effects of target penetration are fairly consistent with those from experimental results.
2016, 36(5): 734-738.
doi: 10.11883/1001-1455(2016)05-0734-05
Abstract:
Indentation responses and deformation characteristics of closed-cell aluminum foams under elevated temperatures were experimentally investigated by using a flat-ended punch (FEP) and a hemispherical-ended punch (SEP). Based on the quasi-static experimental results at elevated temperatures, dimensional analysis and finite element simulations are used to examine the empirical relations of the SEP and FEP indentation load responses and the indentation depth and test temperature. The theoretical predictions based on the results of the analysis are compared with the experiments. It was found that the load responses are described well by the empirical formulas for different indenters at different temperatures. This provides the basis for applying a simple indentation test to investigate the mechanical properties of metallic foams.
Indentation responses and deformation characteristics of closed-cell aluminum foams under elevated temperatures were experimentally investigated by using a flat-ended punch (FEP) and a hemispherical-ended punch (SEP). Based on the quasi-static experimental results at elevated temperatures, dimensional analysis and finite element simulations are used to examine the empirical relations of the SEP and FEP indentation load responses and the indentation depth and test temperature. The theoretical predictions based on the results of the analysis are compared with the experiments. It was found that the load responses are described well by the empirical formulas for different indenters at different temperatures. This provides the basis for applying a simple indentation test to investigate the mechanical properties of metallic foams.
