2019 Vol. 39, No. 6
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2019, 39(6): 062101.
doi: 10.11883/bzycj-2018-0163
Abstract:
A two-dimensional axisymmetric model about slow cook-off of solid rocket motor was established, where the process of slow cook-off for ammonium perchlorate/hydroxyl-terminated polybutadiene (AP/HTPB) propellant described by a two-step global chemical reaction kinetics, and natural convection of motor cavity was considered. The purpose of this paper is to study the thermal safety problems of solid rocket motor with ammonium perchlorate/hydroxyl-terminated polybutadiene (AP/HTPB) propellant. Numerical predictions of slow cook-off behavior for a motor were conducted at the heating rate s of 3.6, 7.2 and 10.8 K/h, respectively. The results show that the natural convection in the cavity of the solid rocket motor has a certain influence on the ignition temperature, ignition delay of the AP/HTPB propellant, and cannot be ignored in the accurate analysis of thermal safety. At the three heating rates, the initial ignition position of AP/HTPB propellants appeared in the annular region on the shoulder of the propellant. The ignition delay period, the ignition temperature and the temperature of the shell at the three heating rates were 30.71, 20.06, 18.68 h; 526.52, 528.10, 530.64 K; and 479.56, 496.82, 508.77 K; respectively. With the increase of heating rate, the response area of the cook-off is shifted to the junction between the propellant and the insulation, and the two-dimensional section of the ignition position is changed from ellipse to semi-ellipse.
A two-dimensional axisymmetric model about slow cook-off of solid rocket motor was established, where the process of slow cook-off for ammonium perchlorate/hydroxyl-terminated polybutadiene (AP/HTPB) propellant described by a two-step global chemical reaction kinetics, and natural convection of motor cavity was considered. The purpose of this paper is to study the thermal safety problems of solid rocket motor with ammonium perchlorate/hydroxyl-terminated polybutadiene (AP/HTPB) propellant. Numerical predictions of slow cook-off behavior for a motor were conducted at the heating rate s of 3.6, 7.2 and 10.8 K/h, respectively. The results show that the natural convection in the cavity of the solid rocket motor has a certain influence on the ignition temperature, ignition delay of the AP/HTPB propellant, and cannot be ignored in the accurate analysis of thermal safety. At the three heating rates, the initial ignition position of AP/HTPB propellants appeared in the annular region on the shoulder of the propellant. The ignition delay period, the ignition temperature and the temperature of the shell at the three heating rates were 30.71, 20.06, 18.68 h; 526.52, 528.10, 530.64 K; and 479.56, 496.82, 508.77 K; respectively. With the increase of heating rate, the response area of the cook-off is shifted to the junction between the propellant and the insulation, and the two-dimensional section of the ignition position is changed from ellipse to semi-ellipse.
2019, 39(6): 062102.
doi: 10.11883/bzycj-2018-0223
Abstract:
The free-flow simulation range of the detonation driven shock tunnel is closely related to the detonation limit of the driving gas. The wider the detonation limit, the larger the simulation range. The driving gas is generally detonated through the igniter (ignition tube). Increasing the detonation capability of the ignition tube can broaden the detonation limit. In order to improve the ignition capacity of the igniter, the effects of three factors, the diameter of the ignition tube, the detonation sensitivity of the ignition gas, and the single/double igniter tube, were investigated experimentally. The velocity of the driven segment was measured under different initial conditions in the igniters. The conclusions are as follows. Firstly, improving the caliber of the ignition tube can significantly enhance the ability to initiate. Secondly, the ignition gas detonation sensitivity has an impact on the detonation capability: when the igniter is a reduced-diameter internal profile, the low-sensitivity gas has a stronger detonation capability; when the igniter pipe is of the same diameter internal profile, the result is reversed. Finally, if the synchronization of the jets can be ensured, the double igniters can improve the detonation ability. In order to ensure the synchronization, it is necessary to use a sensitive ignition gas like hydrogen oxygen mixtures of equivalent ratio.
The free-flow simulation range of the detonation driven shock tunnel is closely related to the detonation limit of the driving gas. The wider the detonation limit, the larger the simulation range. The driving gas is generally detonated through the igniter (ignition tube). Increasing the detonation capability of the ignition tube can broaden the detonation limit. In order to improve the ignition capacity of the igniter, the effects of three factors, the diameter of the ignition tube, the detonation sensitivity of the ignition gas, and the single/double igniter tube, were investigated experimentally. The velocity of the driven segment was measured under different initial conditions in the igniters. The conclusions are as follows. Firstly, improving the caliber of the ignition tube can significantly enhance the ability to initiate. Secondly, the ignition gas detonation sensitivity has an impact on the detonation capability: when the igniter is a reduced-diameter internal profile, the low-sensitivity gas has a stronger detonation capability; when the igniter pipe is of the same diameter internal profile, the result is reversed. Finally, if the synchronization of the jets can be ensured, the double igniters can improve the detonation ability. In order to ensure the synchronization, it is necessary to use a sensitive ignition gas like hydrogen oxygen mixtures of equivalent ratio.
2019, 39(6): 062201.
doi: 10.11883/bzycj-2018-0118
Abstract:
Bubble collapse near a wall will generate strong micro-jet in a liquid environment under ultrasonic field. To explore the fluid-solid coupling effect of micro-jet impinging on a wall, hydrodynamics and impact dynamics were employed, and the J-C rate correlation material constitutive model was applied, then a three-dimensional fluid-solid coupling model of micro-jet impact on a wall was established and analyzed numerically based on the Euler-Lagrange coupling method. Finally, an ultrasonic cavitation test and inversion analysis based on the theory of the spherical indentation test were conducted for validation. Pit depth is decided jointly by micro-jet velocity and micro-jet diameter, and increases with their increases, while the ratio of diameter to depth of a pit is negatively correlated with the micro-jet velocity. Wall pressure distribution is mostly symmetric and the maximum pressure appears on the edge of micro-jet impinging. The maximum wall pressure clearly increases with the micro-jet velocity. The increase of the pressure can lead to the increase of the shock wave intensity and velocity in liquid, which can reach 682 MPa and 2 435 m/s, respectively, when the micro-jet velocity is 479 m/s. Micropits appearing on the material surface impacted by micro-jet were demonstrated by ultrasonic cavitation test, and the pits’ ratio of diameter to depth vary from 16 to 68. Inversion analysis results indicate that equivalent stress, equivalent strain of the pit and impact strength, velocity of the micro-jet are closely related with the ratio of diameter to depth of the pit. When it is 16−68, the micro-jet impingement strength is 420−500 MPa, and the corresponding micro-jet velocity is 310−370 m/s. Test and inversion analysis results are consistent with the theoretical analysis, which verifies the rationality and accuracy of a fluid-solid coupling model considering the J-C rate correlation material constitutive model and inversion analysis method. This work provides a theoretical reference for the control of cavitation intensity and micro-jet velocity in the following engineering applications.
Bubble collapse near a wall will generate strong micro-jet in a liquid environment under ultrasonic field. To explore the fluid-solid coupling effect of micro-jet impinging on a wall, hydrodynamics and impact dynamics were employed, and the J-C rate correlation material constitutive model was applied, then a three-dimensional fluid-solid coupling model of micro-jet impact on a wall was established and analyzed numerically based on the Euler-Lagrange coupling method. Finally, an ultrasonic cavitation test and inversion analysis based on the theory of the spherical indentation test were conducted for validation. Pit depth is decided jointly by micro-jet velocity and micro-jet diameter, and increases with their increases, while the ratio of diameter to depth of a pit is negatively correlated with the micro-jet velocity. Wall pressure distribution is mostly symmetric and the maximum pressure appears on the edge of micro-jet impinging. The maximum wall pressure clearly increases with the micro-jet velocity. The increase of the pressure can lead to the increase of the shock wave intensity and velocity in liquid, which can reach 682 MPa and 2 435 m/s, respectively, when the micro-jet velocity is 479 m/s. Micropits appearing on the material surface impacted by micro-jet were demonstrated by ultrasonic cavitation test, and the pits’ ratio of diameter to depth vary from 16 to 68. Inversion analysis results indicate that equivalent stress, equivalent strain of the pit and impact strength, velocity of the micro-jet are closely related with the ratio of diameter to depth of the pit. When it is 16−68, the micro-jet impingement strength is 420−500 MPa, and the corresponding micro-jet velocity is 310−370 m/s. Test and inversion analysis results are consistent with the theoretical analysis, which verifies the rationality and accuracy of a fluid-solid coupling model considering the J-C rate correlation material constitutive model and inversion analysis method. This work provides a theoretical reference for the control of cavitation intensity and micro-jet velocity in the following engineering applications.
2019, 39(6): 063101.
doi: 10.11883/bzycj-2018-0114
Abstract:
To study the mechanism of failure behavior and energy release mechanism of Zr-based amorphous alloys, Instron machine, split hopkinson bar, high-speed photography, DSC and SEM are used to achieve the stress-strain curves at low strain rate, stress-strain curves at high strain rate, failure processes, DSC curves and failure morphologies, respectively. The crystallization enthalpy is obtained from DSC curves. The stress-strain curves are fitted by the Johnson-Holmquist II model, and the finite element method using this model is executed to simulate the failure process of material under dynamic compression. The experimental results suggest that the material fractures brittle under compression. Typical vein-like pattern is observed at the fracture surface of the material. The energy releasing occurs simultaneously with the material failure. The simulation results reveal that the internal energy of local crack is higher than crystallization enthalpy of the material. The energy release of Zr-based amorphous alloys results in the elastic potential energy and crystallization energy released by the material with instantaneous crack. The strength of energy release is in direct proportion to strain rates.
To study the mechanism of failure behavior and energy release mechanism of Zr-based amorphous alloys, Instron machine, split hopkinson bar, high-speed photography, DSC and SEM are used to achieve the stress-strain curves at low strain rate, stress-strain curves at high strain rate, failure processes, DSC curves and failure morphologies, respectively. The crystallization enthalpy is obtained from DSC curves. The stress-strain curves are fitted by the Johnson-Holmquist II model, and the finite element method using this model is executed to simulate the failure process of material under dynamic compression. The experimental results suggest that the material fractures brittle under compression. Typical vein-like pattern is observed at the fracture surface of the material. The energy releasing occurs simultaneously with the material failure. The simulation results reveal that the internal energy of local crack is higher than crystallization enthalpy of the material. The energy release of Zr-based amorphous alloys results in the elastic potential energy and crystallization energy released by the material with instantaneous crack. The strength of energy release is in direct proportion to strain rates.
2019, 39(6): 063102.
doi: 10.11883/bzycj-2018-0142
Abstract:
In this paper, we performed SHPB experiments on concrete-like materials with different strengths (C20, C45, C70) and different steel fiber contents (0%, 0.75%, 1.50%, 4.50%) and analyzed the data drawn. The results showed that the constant strain rate corresponding to the experimental data was co-related with the whole-stage average strain rate to a certain degree and therefore the former could be determined by the 1.38 times of the latter. This method was verified as rational by the comparative analysis of the experimental data of non-constant strain rate with the experimental data of constant strain rate. It was also found that, at the constant strain rate in a relatively short loading time, it is unreasonable to characterize the strain rate corresponding to the experimental data using the constant strain rate corresponding to the short platform stage. In this case, the method proposed in this paper offers a good choice.
In this paper, we performed SHPB experiments on concrete-like materials with different strengths (C20, C45, C70) and different steel fiber contents (0%, 0.75%, 1.50%, 4.50%) and analyzed the data drawn. The results showed that the constant strain rate corresponding to the experimental data was co-related with the whole-stage average strain rate to a certain degree and therefore the former could be determined by the 1.38 times of the latter. This method was verified as rational by the comparative analysis of the experimental data of non-constant strain rate with the experimental data of constant strain rate. It was also found that, at the constant strain rate in a relatively short loading time, it is unreasonable to characterize the strain rate corresponding to the experimental data using the constant strain rate corresponding to the short platform stage. In this case, the method proposed in this paper offers a good choice.
2019, 39(6): 063103.
doi: 10.11883/bzycj-2018-0198
Abstract:
In this work we investigated the deformation/failure modes and shock resistance performance of sandwich panels with layered-gradient aluminum foam cores under air-blast loading by experiment using a ballistic pendulum device, the deflection-time history curves in the central point of the back face-sheet were measured using a laser displacement sensor, and examined the influences of the charge mass and core-layer arrangement on the failure modes and the shock resistance of the specimens. The results showed that the sandwich panel specimens failed due to the large inelastic deformation of the face-sheets, the core compression, the tensile fracture and the shear failure of the core. The shock resistance performance of the ungraded sandwich panels was found to be superior to all the graded core sandwich configurations. For the sandwich panels with layered-gradient cores, the improvement of the core-layer arrangement on the shock resistance of the specimens was not obvious under small blast impulse, while that of the graded specimens containing the top core-layer with the largest relative density demonstrated a remarkably greater shock resistance. These findings can serve as guidance in the optimal design of metallic foam core sandwich structures.
In this work we investigated the deformation/failure modes and shock resistance performance of sandwich panels with layered-gradient aluminum foam cores under air-blast loading by experiment using a ballistic pendulum device, the deflection-time history curves in the central point of the back face-sheet were measured using a laser displacement sensor, and examined the influences of the charge mass and core-layer arrangement on the failure modes and the shock resistance of the specimens. The results showed that the sandwich panel specimens failed due to the large inelastic deformation of the face-sheets, the core compression, the tensile fracture and the shear failure of the core. The shock resistance performance of the ungraded sandwich panels was found to be superior to all the graded core sandwich configurations. For the sandwich panels with layered-gradient cores, the improvement of the core-layer arrangement on the shock resistance of the specimens was not obvious under small blast impulse, while that of the graded specimens containing the top core-layer with the largest relative density demonstrated a remarkably greater shock resistance. These findings can serve as guidance in the optimal design of metallic foam core sandwich structures.
2019, 39(6): 063301.
doi: 10.11883/bzycj-2018-0094
Abstract:
At the initial stage of water entry, the water surrounding of the rigid sphere will show strong nonlinear characteristics. However, there are no exact three-dimensional effects in impact problem within the Wagner theory. Based on the non-viscous incompressible flow model, this paper considered fluid elasticity, used the micro boundary motion equivalent method to analyze the moving boundary, and based on the theory of energy conservation, which considered the loss of kinetic energy, analyzed the three-dimensional flow of the fluid around the rigid sphere during high-speed water-entry vertically, then established the analytical model which can calculate the water-entry impact of rigid sphere, and the analytical model is verified by an FEM model of multi-material ALE method. Base on the analytical model, this paper also analyzed the influencing factors of impact. The analytical model provides a fast algorithm for calculating the high-speed water-entry impact of structure, and has certain theoretical significance and engineering application value.
At the initial stage of water entry, the water surrounding of the rigid sphere will show strong nonlinear characteristics. However, there are no exact three-dimensional effects in impact problem within the Wagner theory. Based on the non-viscous incompressible flow model, this paper considered fluid elasticity, used the micro boundary motion equivalent method to analyze the moving boundary, and based on the theory of energy conservation, which considered the loss of kinetic energy, analyzed the three-dimensional flow of the fluid around the rigid sphere during high-speed water-entry vertically, then established the analytical model which can calculate the water-entry impact of rigid sphere, and the analytical model is verified by an FEM model of multi-material ALE method. Base on the analytical model, this paper also analyzed the influencing factors of impact. The analytical model provides a fast algorithm for calculating the high-speed water-entry impact of structure, and has certain theoretical significance and engineering application value.
2019, 39(6): 063302.
doi: 10.11883/bzycj-2018-0411
Abstract:
In the present study we developed an analytical model to describe the attitude deflection of the rigid projectile obliquely penetrating into concrete targets. To improve on the previous models, we took the effect of the inertia moment of the projectile into account and assumed anew the shape of the plug formed on the rear surface of the concrete target with regard to the experimental perforation characteristics, and introduced a second attitude deflection mechanism into the shear plugging stage. Moreover, we proposed to classify concrete targets into three types, i.e. thin, medium and thick. The calculated results under different perforation situations accorded well with the experimental data, indicating the validity of our analytical model in predicting the projectile attitude during the oblique perforation of concrete targets.
In the present study we developed an analytical model to describe the attitude deflection of the rigid projectile obliquely penetrating into concrete targets. To improve on the previous models, we took the effect of the inertia moment of the projectile into account and assumed anew the shape of the plug formed on the rear surface of the concrete target with regard to the experimental perforation characteristics, and introduced a second attitude deflection mechanism into the shear plugging stage. Moreover, we proposed to classify concrete targets into three types, i.e. thin, medium and thick. The calculated results under different perforation situations accorded well with the experimental data, indicating the validity of our analytical model in predicting the projectile attitude during the oblique perforation of concrete targets.
2019, 39(6): 064101.
doi: 10.11883/bzycj-2018-0091
Abstract:
A novel fiber optic pressure sensing technology is presented to obtain the peak reflected pressure of shock waves. This technology is based on the Newton's second law and the pressure relates directly to the acceleration of a thin diaphragm. The acceleration is detected by an interferometric measurement of the displacement using a Fabry-Perot cavity technology. Both numerical simulation and shock tube experiments prove that the pressure sensing technology is feasible. And this technology has several advantages including no calibration required, ease of manufacture, low cost, high precision and fast response times.
A novel fiber optic pressure sensing technology is presented to obtain the peak reflected pressure of shock waves. This technology is based on the Newton's second law and the pressure relates directly to the acceleration of a thin diaphragm. The acceleration is detected by an interferometric measurement of the displacement using a Fabry-Perot cavity technology. Both numerical simulation and shock tube experiments prove that the pressure sensing technology is feasible. And this technology has several advantages including no calibration required, ease of manufacture, low cost, high precision and fast response times.
2019, 39(6): 064102.
doi: 10.11883/bzycj-2018-0513
Abstract:
To investigate the effect of strain rate on the bond-slip behaviors of smooth steel bars in concrete, we conducted plain steel bar pullout tests from quasi-static to impact loading using a high-speed tensile test machine and obtained the whole bond-slip curves of the plane steel bar at different strain rate with reasonable designed stop devices and testing methods. The test results show that the bond strength increased obviously, and the failure mode transferred from pullout to splitting with the increase of the strain rate, that the dynamic increase factor（DIF） curve can be divided into two parts, those of the low and high strain rates, and that the DIF increased slowly with the increase of the strain rate at low strain rates, but increased sharply at high strain rates.
To investigate the effect of strain rate on the bond-slip behaviors of smooth steel bars in concrete, we conducted plain steel bar pullout tests from quasi-static to impact loading using a high-speed tensile test machine and obtained the whole bond-slip curves of the plane steel bar at different strain rate with reasonable designed stop devices and testing methods. The test results show that the bond strength increased obviously, and the failure mode transferred from pullout to splitting with the increase of the strain rate, that the dynamic increase factor（DIF） curve can be divided into two parts, those of the low and high strain rates, and that the DIF increased slowly with the increase of the strain rate at low strain rates, but increased sharply at high strain rates.
2019, 39(6): 064201.
doi: 10.11883/bzycj-2018-0167
Abstract:
Upon impinging on a rigid surface, the blast wave would go through regular and irregular reflection successively. A theoretical model is developed for the determination of the flow field behind the reflected wave, which is based on the method of image and identifies the field around blast wave reflection with that resulting from the interaction of real and imaginary bursts. Firstly, approximations of both reflected wave and Mach stems to circular arcs, centered on the imaginary burst point and ground zero respectively, are made. Then, given the blast free field, the method based on geometrical similarity is applied to calculate the temporal evolution of shock wave structures and differentiate different flow zones. Lastly, a newly developed addition model LAMBR (LAMB revisied) is employed to obtain the field parameters behind the reflected wave. The field parameter contours and peak values are in good agreement with the numerical results and the data from UFC 3-340-02, so the theoretical model is valid. And, the time needed for the theoretical calculation is much shorter than that for numerical simulation.
Upon impinging on a rigid surface, the blast wave would go through regular and irregular reflection successively. A theoretical model is developed for the determination of the flow field behind the reflected wave, which is based on the method of image and identifies the field around blast wave reflection with that resulting from the interaction of real and imaginary bursts. Firstly, approximations of both reflected wave and Mach stems to circular arcs, centered on the imaginary burst point and ground zero respectively, are made. Then, given the blast free field, the method based on geometrical similarity is applied to calculate the temporal evolution of shock wave structures and differentiate different flow zones. Lastly, a newly developed addition model LAMBR (LAMB revisied) is employed to obtain the field parameters behind the reflected wave. The field parameter contours and peak values are in good agreement with the numerical results and the data from UFC 3-340-02, so the theoretical model is valid. And, the time needed for the theoretical calculation is much shorter than that for numerical simulation.
2019, 39(6): 064202.
doi: 10.11883/bzycj-2018-0171
Abstract:
The peak pressure on the borehole wall is an important parameter for non-fluid solid coupling dynamic analysis of blasting. Aiming at the method for calculating the borehole peak pressure of the contour blasting, the interaction between explosion shock wave and elastic wall is theoretically analyzed, and the theoretical solution of pressure increase multiple after the collision of air shock wave and elastic wall is derived. The fluid solid coupling dynamic finite element numerical analysis method is used to study the blast air shock wave increase factor and borehole peak pressure under three kinds of rock mass media, two kinds of commonly used explosives for contour blasting, five common decoupling coefficients and two kinds of axial charging coefficient conditions. The results show that: the explosion shock wave increase factor of contour blasting is not a constant, and it is related to explosives characteristics, borehole medium conditions, decouple coefficient and other factors, correspondingly, the borehole peak pressure is also related to the above factors. Based on the statistical analysis results of borehole peak pressure simulation, combined with the theoretical deduction results and the commonly used calculation formula for the peak pressure on borehole wall, a new method for calculating borehole peak pressure in the contour blasting is proposed.
The peak pressure on the borehole wall is an important parameter for non-fluid solid coupling dynamic analysis of blasting. Aiming at the method for calculating the borehole peak pressure of the contour blasting, the interaction between explosion shock wave and elastic wall is theoretically analyzed, and the theoretical solution of pressure increase multiple after the collision of air shock wave and elastic wall is derived. The fluid solid coupling dynamic finite element numerical analysis method is used to study the blast air shock wave increase factor and borehole peak pressure under three kinds of rock mass media, two kinds of commonly used explosives for contour blasting, five common decoupling coefficients and two kinds of axial charging coefficient conditions. The results show that: the explosion shock wave increase factor of contour blasting is not a constant, and it is related to explosives characteristics, borehole medium conditions, decouple coefficient and other factors, correspondingly, the borehole peak pressure is also related to the above factors. Based on the statistical analysis results of borehole peak pressure simulation, combined with the theoretical deduction results and the commonly used calculation formula for the peak pressure on borehole wall, a new method for calculating borehole peak pressure in the contour blasting is proposed.
2019, 39(6): 065101.
doi: 10.11883/bzycj-2018-0090
Abstract:
Through the experimental study on the damage effect of underwater explosion on caisson gravity wharf model under different explosion distances, data collection and analysis for underwater loads and model damage are conducted, a study on damage factors, damage modes and damage mechanisms is developed, and the impact of explosion distance is initially discussed. The results show that the complete bubble pulsation process is not formed. Load overpressure mainly occurrs during the propagation stage of shock wave; explosive shock wave, reflected bottom wave and reflected sidewall wave are main damage factors; underwater explosions causes the damage with serious damage effectiveness, multiple modes and complex mechanisms to the caisson gravity wharf, and the major damage parts are exterior wall of explsion faces, proximal pipe trenche, cabin-sealing covers and face plate; the closer the explosion distance, the more serious the structural damage; however, when the explosion distance is too close, the explosion energy is mostly absorbed by the structural distortion of the blasting surface, so the growth on the severity of the explsive-side exterior wall’s damage increases significantly and the growth on the severity of other parts’ damage slows down.
Through the experimental study on the damage effect of underwater explosion on caisson gravity wharf model under different explosion distances, data collection and analysis for underwater loads and model damage are conducted, a study on damage factors, damage modes and damage mechanisms is developed, and the impact of explosion distance is initially discussed. The results show that the complete bubble pulsation process is not formed. Load overpressure mainly occurrs during the propagation stage of shock wave; explosive shock wave, reflected bottom wave and reflected sidewall wave are main damage factors; underwater explosions causes the damage with serious damage effectiveness, multiple modes and complex mechanisms to the caisson gravity wharf, and the major damage parts are exterior wall of explsion faces, proximal pipe trenche, cabin-sealing covers and face plate; the closer the explosion distance, the more serious the structural damage; however, when the explosion distance is too close, the explosion energy is mostly absorbed by the structural distortion of the blasting surface, so the growth on the severity of the explsive-side exterior wall’s damage increases significantly and the growth on the severity of other parts’ damage slows down.
2019, 39(6): 065102.
doi: 10.11883/bzycj-2018-0060
Abstract:
A sandwich defensive structure made up of the star-shaped auxetic cellular material is designed in this paper. FE models are developed to simulate the process of projectile penetration and underwater explosion. Different structure parameters, such as cell thickness and Poisson’s ratio of the star-shaped material, are applied to investigate the affections of the auxetic insert layer in projectile penetration and explosion. According to the numerical simulation results, the star-shaped auxetic sandwich structure does not strong enough to defense missile attacks as it bringing higher residual velocity compared with the traditional monolithic shield. Meanwhile, this auxetic structure tends to show better anti-explosive performance than the traditional shield of equal mass. Structure parameters of the star-shaped material influence the anti-explosion ability of sandwich structure in different complicated ways. As far as simulated cases, the sandwich structure can achieve the best anti-explosion performance by setting the value 1.63 for Poisson’s ratio of auxetic cellular and decreasing the layers of the cellular material.
A sandwich defensive structure made up of the star-shaped auxetic cellular material is designed in this paper. FE models are developed to simulate the process of projectile penetration and underwater explosion. Different structure parameters, such as cell thickness and Poisson’s ratio of the star-shaped material, are applied to investigate the affections of the auxetic insert layer in projectile penetration and explosion. According to the numerical simulation results, the star-shaped auxetic sandwich structure does not strong enough to defense missile attacks as it bringing higher residual velocity compared with the traditional monolithic shield. Meanwhile, this auxetic structure tends to show better anti-explosive performance than the traditional shield of equal mass. Structure parameters of the star-shaped material influence the anti-explosion ability of sandwich structure in different complicated ways. As far as simulated cases, the sandwich structure can achieve the best anti-explosion performance by setting the value 1.63 for Poisson’s ratio of auxetic cellular and decreasing the layers of the cellular material.
2019, 39(6): 065201.
doi: 10.11883/bzycj-2018-0089
Abstract:
In this study we investigated the mechanism of water pressure blasting in the thin-walled bridge pier, taking the water pressure directional blasting demolition project of Jamuna bridge as the research object and using the explicit dynamics analysis software to simulate the crushing process of the water pressure blasting in the bridge pier. The numerical simulation results show that the failure of the bridge pier mainly depends on the explosive shock wave, the detonation gas, the reflected tension wave and the high-speed flow. Based on these findings, we examined the technical problems of the arrangement of the explosive charge and the order of detonation in the directional water pressure blasting in the bridge pier.
In this study we investigated the mechanism of water pressure blasting in the thin-walled bridge pier, taking the water pressure directional blasting demolition project of Jamuna bridge as the research object and using the explicit dynamics analysis software to simulate the crushing process of the water pressure blasting in the bridge pier. The numerical simulation results show that the failure of the bridge pier mainly depends on the explosive shock wave, the detonation gas, the reflected tension wave and the high-speed flow. Based on these findings, we examined the technical problems of the arrangement of the explosive charge and the order of detonation in the directional water pressure blasting in the bridge pier.
2019, 39(6): 065401.
doi: 10.11883/bzycj-2018-0131
Abstract:
In this study we investigated the effect of inert gas addition on the characteristics of the syngas explosion using 20 L spherical explosive device. Effects of different volume fraction of inert gas (CO2/N2) on the explosion parameters including the peak pressure, the delay of the peak pressure time, and the explosion index were obtained from the experiment. The results show that the delay of the peak pressure time of the syngas explosion rose higher, and the explosion peak pressure and the explosion index fell lower with the increase of the volume fraction of the inert gas; that CO2 had a stronger inhibition effect on syngas explosion than N2 because the peak pressure and the explosion index fell down more sharply with the addition of CO2 than of N2.
In this study we investigated the effect of inert gas addition on the characteristics of the syngas explosion using 20 L spherical explosive device. Effects of different volume fraction of inert gas (CO2/N2) on the explosion parameters including the peak pressure, the delay of the peak pressure time, and the explosion index were obtained from the experiment. The results show that the delay of the peak pressure time of the syngas explosion rose higher, and the explosion peak pressure and the explosion index fell lower with the increase of the volume fraction of the inert gas; that CO2 had a stronger inhibition effect on syngas explosion than N2 because the peak pressure and the explosion index fell down more sharply with the addition of CO2 than of N2.
2019, 39(6): 065202.
doi: 10.11883/bzycj-2018-0137
Abstract:
In this study, based on the high stress and frequent blast disturbance in the process of surrounding rock excavation in the deep roadway of Dongguashan Copper Mine, we investigated the dynamic properties of the high-energy rock mass disturbed by frequent dynamic loading during confining pressure unloading, using the modified SHPB coupled static-dynamic loading system. The results show that the peak dynamic stress and elastic modulus of the skarn subjected to confining pressure unloading varied nonlinearly with the number of dynamic disturbances, and the high energy skarn in confining pressure unloading released energy when subjected to dynamic disturbance. The axial pressure promoted the axial development of micro-fissures in the rock specimens, resulting in a lower capacity of rock samples. However, the confining pressure restrained the axial development of micro-fissures in the rock sample, resulting in a higher capacity of rock samples. The dynamic disturbance promoted the micro-fracture expansion, transforming the rock sample in confining pressure from tensile failure to shear failure.
In this study, based on the high stress and frequent blast disturbance in the process of surrounding rock excavation in the deep roadway of Dongguashan Copper Mine, we investigated the dynamic properties of the high-energy rock mass disturbed by frequent dynamic loading during confining pressure unloading, using the modified SHPB coupled static-dynamic loading system. The results show that the peak dynamic stress and elastic modulus of the skarn subjected to confining pressure unloading varied nonlinearly with the number of dynamic disturbances, and the high energy skarn in confining pressure unloading released energy when subjected to dynamic disturbance. The axial pressure promoted the axial development of micro-fissures in the rock specimens, resulting in a lower capacity of rock samples. However, the confining pressure restrained the axial development of micro-fissures in the rock sample, resulting in a higher capacity of rock samples. The dynamic disturbance promoted the micro-fracture expansion, transforming the rock sample in confining pressure from tensile failure to shear failure.
