2017 Vol. 37, No. 6
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2017, 37(6): 893-900.
doi: 10.11883/1001-1455(2017)06-0893-08
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Abstract:
In the present study, sampling technique was used to deal with the input parameter uncertainty in the numerical simulation of detonation CFD(computational fluid dynamics). Then the deterministic detonation CFD program was constructed with different input. The sample of the input parameter and system response quantity was obtained through the previous result. The cumulative distribution function and the horsetail of error was utilized to achieve the confidence level, which was then used to assess the influence of the input parameter uncertainty on the simulation result of detonation CFD. The horsetail graph of error in one dimensional Riemann problem and planar detonation problem were presented to analyze the relationship between the confidence level of simulation result and the mesh used in LAD2D. This method provides a reference for developing the software of multi-physics detonation process on high confidence level.
In the present study, sampling technique was used to deal with the input parameter uncertainty in the numerical simulation of detonation CFD(computational fluid dynamics). Then the deterministic detonation CFD program was constructed with different input. The sample of the input parameter and system response quantity was obtained through the previous result. The cumulative distribution function and the horsetail of error was utilized to achieve the confidence level, which was then used to assess the influence of the input parameter uncertainty on the simulation result of detonation CFD. The horsetail graph of error in one dimensional Riemann problem and planar detonation problem were presented to analyze the relationship between the confidence level of simulation result and the mesh used in LAD2D. This method provides a reference for developing the software of multi-physics detonation process on high confidence level.
2017, 37(6): 901-906.
doi: 10.11883/1001-1455(2017)06-0901-06
Abstract:
As the strain growth poses a potential hazard for the safety of an explosion vessel, it is of great importance to figure out its limit. The experiment, which was carried out in a spherical explosion vessel, shows that the maximum strain growth factor is up to 6.1. Numerical simulation was conducted to analyze the limit of the strain growth induced by the superposition of different vibration modes in the spherical vessel with elastic deformation. The following conclusions were reached: First, the strain growth phenomenon obeys the law of geometric similarity. The strain growth factor is related to the perturbation type, the ratio of the perturbation radius to the spherical shell radius, the ratio of the spherical shell thickness to the spherical shell radius, the first strain peak and so on. The perturbation type and the ratio of the perturbation radius to the spherical shell radius are the main influencing factors. Second, the largest strain growth factor is up to 12 when the perturbation is fully constrained and the perturbation radius is equal to the spherical shell radius.
As the strain growth poses a potential hazard for the safety of an explosion vessel, it is of great importance to figure out its limit. The experiment, which was carried out in a spherical explosion vessel, shows that the maximum strain growth factor is up to 6.1. Numerical simulation was conducted to analyze the limit of the strain growth induced by the superposition of different vibration modes in the spherical vessel with elastic deformation. The following conclusions were reached: First, the strain growth phenomenon obeys the law of geometric similarity. The strain growth factor is related to the perturbation type, the ratio of the perturbation radius to the spherical shell radius, the ratio of the spherical shell thickness to the spherical shell radius, the first strain peak and so on. The perturbation type and the ratio of the perturbation radius to the spherical shell radius are the main influencing factors. Second, the largest strain growth factor is up to 12 when the perturbation is fully constrained and the perturbation radius is equal to the spherical shell radius.
2017, 37(6): 907-914.
doi: 10.11883/1001-1455(2017)06-0907-08
Abstract:
In combination with the measured data of the blasting vibration, the total energy, the frequency band energy, and the PPV of each band of the blasting vibration signal with different numbers of free surfaces were obtained using the wavelet analysis. Then the energy distribution characteristics of the blasting vibration signal with different numbers of free surfaces were studied. The results show that the slotted blasting or cut blasting is restricted by a single free surface, thus most of the energy of the explosion will be consumed as seismic energy; the greater the number of free surfaces, the less the total energy of the blasting vibration signal; with the increase of the of free surfaces, the distribution of the vibration components of each frequency band can be affected, which makes the blasting vibration energy more tend to be the high frequency distribution, so that the energy in the middle and low frequency can be reduced, and the vibration velocity is reduced as well; the PPV of the high frequency band is higher than that of the low frequency band, but the duration of the vibration is shorter, and the energy attenuation is faster in the same vibration signal. It is suggested that, in the design of reducing the blasting vibration, it is more effective to optimize the initiation scheme by using as many free surfaces as possible than by merely reducing the single segment of detonating charge.
In combination with the measured data of the blasting vibration, the total energy, the frequency band energy, and the PPV of each band of the blasting vibration signal with different numbers of free surfaces were obtained using the wavelet analysis. Then the energy distribution characteristics of the blasting vibration signal with different numbers of free surfaces were studied. The results show that the slotted blasting or cut blasting is restricted by a single free surface, thus most of the energy of the explosion will be consumed as seismic energy; the greater the number of free surfaces, the less the total energy of the blasting vibration signal; with the increase of the of free surfaces, the distribution of the vibration components of each frequency band can be affected, which makes the blasting vibration energy more tend to be the high frequency distribution, so that the energy in the middle and low frequency can be reduced, and the vibration velocity is reduced as well; the PPV of the high frequency band is higher than that of the low frequency band, but the duration of the vibration is shorter, and the energy attenuation is faster in the same vibration signal. It is suggested that, in the design of reducing the blasting vibration, it is more effective to optimize the initiation scheme by using as many free surfaces as possible than by merely reducing the single segment of detonating charge.
2017, 37(6): 915-923.
doi: 10.11883/1001-1455(2017)06-0915-09
Abstract:
In the present work, shock initiation experiments on CL-20, CL-20/NTO and CL-20/FOX-7 mixed explosives were performed to investigate the shock initiation characteristics of Hexanitro-hexaazaisowurtzitane (CL-20) based explosives. An explosive driven flyer device was utilized to initiate the charges with manganin gauges embedded into the target to measure time resolved local pressure histories. The shock initiation of CL-20 based explosives was simulated using the ignition and growth reactive flow model, and the parameters were obtained by fitting the experimental data. Furthermore, the reaction of two compositions in CL-20/NTO and CL-20/FOX-7 was simulated respectively using the two growth terms in the ignition and growth model. The parameters were then applied in the calculation of the initial shock pressure-distance to detonation relationship (Pop plot) and the shock initiation critical thresholds for the three mixed explosives. The results show that the CL-20/NTO explosive has a higher shock initiation critical threshold, while the CL-20/FOX-7 explosive has a longer distance to detonation under the same loading conditions. Besides, this model for the explosive with the two compositions can be applied to predict the shock initiation characteristics of the explosive with new formulations.
In the present work, shock initiation experiments on CL-20, CL-20/NTO and CL-20/FOX-7 mixed explosives were performed to investigate the shock initiation characteristics of Hexanitro-hexaazaisowurtzitane (CL-20) based explosives. An explosive driven flyer device was utilized to initiate the charges with manganin gauges embedded into the target to measure time resolved local pressure histories. The shock initiation of CL-20 based explosives was simulated using the ignition and growth reactive flow model, and the parameters were obtained by fitting the experimental data. Furthermore, the reaction of two compositions in CL-20/NTO and CL-20/FOX-7 was simulated respectively using the two growth terms in the ignition and growth model. The parameters were then applied in the calculation of the initial shock pressure-distance to detonation relationship (Pop plot) and the shock initiation critical thresholds for the three mixed explosives. The results show that the CL-20/NTO explosive has a higher shock initiation critical threshold, while the CL-20/FOX-7 explosive has a longer distance to detonation under the same loading conditions. Besides, this model for the explosive with the two compositions can be applied to predict the shock initiation characteristics of the explosive with new formulations.
2017, 37(6): 924-930.
doi: 10.11883/1001-1455(2017)06-0924-07
Abstract:
In this work, lower explosion limits of methane, lycopodium dust and methane-lycopodium dust hybrid mixtures were determined under the same testing conditions based on the 20 L sphere vessel. The measured results were compared with the values calculated by the Le Chatelier's law, the Bartknecht curve and the Jiang method. The results showed that the combination of methane prepared in concentrations below its lower explosion limit and the lycopodium dust in concentrations below its minimum explosion concentration rate was still a mixture with a hazard of explosion. The minimum explosion concentration of lycopodium dust decreased with the increase of methane concentration in the hybrid mixtures. The lower explosion limit of methane-lycopodium dust hybrid mixtures couldn't be accurately calculated by the Le Chatelier's law, the Bartknecht curve or the Jiang method. The lower explosion limit of hybrid mixtures of methane and lycopodium dust calculated by the Le Chatelier's law were smaller than the measured values for the mixtures with the methane concentration φ/φL < 0.5, but bigger for the mixtures with the methane concentration φ/φL>0.5. The Bartknecht curve was suitable for predicting the lower explosion limit of the hybrid mixtures with the methane concentration φ/φL>0.5. But for the hybrid mixtures with a methane concentration φ/φL < 0.5, the calculated values were smaller than the measured ones, whereas the Jiang method was unsuitable for predicting the lower explosion limit of the hybrid mixtures of methane and lycopodium dust.
In this work, lower explosion limits of methane, lycopodium dust and methane-lycopodium dust hybrid mixtures were determined under the same testing conditions based on the 20 L sphere vessel. The measured results were compared with the values calculated by the Le Chatelier's law, the Bartknecht curve and the Jiang method. The results showed that the combination of methane prepared in concentrations below its lower explosion limit and the lycopodium dust in concentrations below its minimum explosion concentration rate was still a mixture with a hazard of explosion. The minimum explosion concentration of lycopodium dust decreased with the increase of methane concentration in the hybrid mixtures. The lower explosion limit of methane-lycopodium dust hybrid mixtures couldn't be accurately calculated by the Le Chatelier's law, the Bartknecht curve or the Jiang method. The lower explosion limit of hybrid mixtures of methane and lycopodium dust calculated by the Le Chatelier's law were smaller than the measured values for the mixtures with the methane concentration φ/φL < 0.5, but bigger for the mixtures with the methane concentration φ/φL>0.5. The Bartknecht curve was suitable for predicting the lower explosion limit of the hybrid mixtures with the methane concentration φ/φL>0.5. But for the hybrid mixtures with a methane concentration φ/φL < 0.5, the calculated values were smaller than the measured ones, whereas the Jiang method was unsuitable for predicting the lower explosion limit of the hybrid mixtures of methane and lycopodium dust.
2017, 37(6): 931-938.
doi: 10.11883/1001-1455(2017)06-0931-08
Abstract:
Abundant underground rock information can be obtained through the analysis of time-frequency of explosive seismic wave signals, which lays a foundation for further research on characteristics of explosive seismic waves. In this study, based on the non-stationary random nature of the explosive seismic signals, we presented an improved matching pursuits (MP) algorithm to extract the time-frequency information of explosive seismic signals, namely using the Hilbert transformation to convert the signal into a plural signal to acquire the instantaneous frequency and phase parameter of the signal and then decomposing the signal to a series of wavelets. Thus the operation rate was significantly improved and the Wigner Ville distributions (WVD) and its time frequency were calculated with the influence of the cross interference term effectively eliminated. This method has been used to take a time-frequency analysis of an actual explosive seismic wave signal and has acquired a time-frequency distribution with a high resolution and operation rate.
Abundant underground rock information can be obtained through the analysis of time-frequency of explosive seismic wave signals, which lays a foundation for further research on characteristics of explosive seismic waves. In this study, based on the non-stationary random nature of the explosive seismic signals, we presented an improved matching pursuits (MP) algorithm to extract the time-frequency information of explosive seismic signals, namely using the Hilbert transformation to convert the signal into a plural signal to acquire the instantaneous frequency and phase parameter of the signal and then decomposing the signal to a series of wavelets. Thus the operation rate was significantly improved and the Wigner Ville distributions (WVD) and its time frequency were calculated with the influence of the cross interference term effectively eliminated. This method has been used to take a time-frequency analysis of an actual explosive seismic wave signal and has acquired a time-frequency distribution with a high resolution and operation rate.
2017, 37(6): 939-945.
doi: 10.11883/1001-1455(2017)06-0939-07
Abstract:
In this work, aiming to the prediction speed and accuracy, we established a random forest model for residential structure damage induced by blast vibration identification on the basis of the random forest (RF) theory. Twelve indexes, i.e. peak particle velocity, dominant frequency, dominant frequency duration, maximum charge per delay, distance, gray joints intensity, rate of brick walls, height of housing, roof structures parameter, beam-column frames parameter, quality parameter of construction and site conditions parameters, were considered as the criterion indices for this kind of damage in the proposed model based on the of analysis of the characteristic parameters of blasting vibration and dynamic characteristics of the housing structure. 108 sets of vibration measured data were investigated to create an RF classifier. RF was a combination of tree predictors, and variable importance was measured by gini importance parameter when the forest grows. A random tree was a combination of decision trees, and each tree is generated depending on the values of random vectors sampled independently, with the same distribution for all trees in the forest. The Gini importance value shows that the peak particle velocity is the most important discrimination indicator, followed by the distance, the dominant frequency duration, the dominant frequency, the beam-column frames parameter, the gray joints intensity, the roof structures parameter, the height of housing, the maximum charge per delay, the quality parameter of construction, the rate of brick walls and the site conditions parameters. Another twelve groups of residential structure damage instances were tested as forecast samples, and the predicted results were identical with the actual situation. Engineering practices indicate that the accuracy of the RF method of learning samples is 87.97%, and the accuracy of the test samples is 91.7%, effectively verifying and supplementing the existing methods for evaluating residential structure damage induced by blast vibration.
In this work, aiming to the prediction speed and accuracy, we established a random forest model for residential structure damage induced by blast vibration identification on the basis of the random forest (RF) theory. Twelve indexes, i.e. peak particle velocity, dominant frequency, dominant frequency duration, maximum charge per delay, distance, gray joints intensity, rate of brick walls, height of housing, roof structures parameter, beam-column frames parameter, quality parameter of construction and site conditions parameters, were considered as the criterion indices for this kind of damage in the proposed model based on the of analysis of the characteristic parameters of blasting vibration and dynamic characteristics of the housing structure. 108 sets of vibration measured data were investigated to create an RF classifier. RF was a combination of tree predictors, and variable importance was measured by gini importance parameter when the forest grows. A random tree was a combination of decision trees, and each tree is generated depending on the values of random vectors sampled independently, with the same distribution for all trees in the forest. The Gini importance value shows that the peak particle velocity is the most important discrimination indicator, followed by the distance, the dominant frequency duration, the dominant frequency, the beam-column frames parameter, the gray joints intensity, the roof structures parameter, the height of housing, the maximum charge per delay, the quality parameter of construction, the rate of brick walls and the site conditions parameters. Another twelve groups of residential structure damage instances were tested as forecast samples, and the predicted results were identical with the actual situation. Engineering practices indicate that the accuracy of the RF method of learning samples is 87.97%, and the accuracy of the test samples is 91.7%, effectively verifying and supplementing the existing methods for evaluating residential structure damage induced by blast vibration.
2017, 37(6): 1001-1009.
doi: 10.11883/1001-1455(2017)06-1001-09
Abstract:
In this work, in view of the design issues concerning the strength of the explosion testing pool, we simulated numerically the shock wave propagation in water and structural dynamic responses of the testing pool subjected to a 10 kg TNT explosion impact loading using the nonlinear dynamics program LS-DYNA. We also quantitatively calculated the capability of the air tank and the bubble curtain to weaken the shock wave in water. The results show that the weakening effect of the air tank on the shock wave peak pressure and the specific impulse is close to 50% and 16.2%, that of the bubble curtain on the shock wave reflection and the specific impulse is as high as 86.2% and 75.6%. Based on this, we further analyzed the mechanism of the impact loading and the structural response and carried out a preliminary investigation of the distribution and transmission of the explosion energy between each substance. Our work can be used as reference for the engineering design of similar explosion testing pools.
In this work, in view of the design issues concerning the strength of the explosion testing pool, we simulated numerically the shock wave propagation in water and structural dynamic responses of the testing pool subjected to a 10 kg TNT explosion impact loading using the nonlinear dynamics program LS-DYNA. We also quantitatively calculated the capability of the air tank and the bubble curtain to weaken the shock wave in water. The results show that the weakening effect of the air tank on the shock wave peak pressure and the specific impulse is close to 50% and 16.2%, that of the bubble curtain on the shock wave reflection and the specific impulse is as high as 86.2% and 75.6%. Based on this, we further analyzed the mechanism of the impact loading and the structural response and carried out a preliminary investigation of the distribution and transmission of the explosion energy between each substance. Our work can be used as reference for the engineering design of similar explosion testing pools.
2017, 37(6): 1010-1016.
doi: 10.11883/1001-1455(2017)06-1010-07
Abstract:
In the present study, we loaded smooth and notched cylindrical specimens of magnesium alloy MB2 under quasi-static and dynamic tension states using the material testing machine and split Hopkinson tension bar (SHTB), to characterize the alloy's tensile fracture behaviors under different stress states and strain rates. The constitution of the alloy for quasi-static and dynamic tension states was fitted and the modified fracture criterion based on the Johnson-Cook model was established and then used to simulate the fracture behavior of different tensile specimens. The microscopic damage mechanisms corresponding to the macroscopic fracture pattern was analyzed by SEM. The results show that with the increase of the stress triaxiality, the equivalent strain to fracture of the alloy increases at first and then decreases, and the fracture pattern changes from shear fracture to vertical tension fracture with micro damage mechanisms changing from the mixed failure to the dimple failure; with the increase of the strain rate, the equivalent strain to fracture decreases, and the fracture pattern remains the same. The Johnson-Cook constitution and the modified Johnson-Cook fracture criterion can be used to fit the experimental results under quasi-static and dynamic tension states and predict the cup-cone fracture characteristics of different specimens.
In the present study, we loaded smooth and notched cylindrical specimens of magnesium alloy MB2 under quasi-static and dynamic tension states using the material testing machine and split Hopkinson tension bar (SHTB), to characterize the alloy's tensile fracture behaviors under different stress states and strain rates. The constitution of the alloy for quasi-static and dynamic tension states was fitted and the modified fracture criterion based on the Johnson-Cook model was established and then used to simulate the fracture behavior of different tensile specimens. The microscopic damage mechanisms corresponding to the macroscopic fracture pattern was analyzed by SEM. The results show that with the increase of the stress triaxiality, the equivalent strain to fracture of the alloy increases at first and then decreases, and the fracture pattern changes from shear fracture to vertical tension fracture with micro damage mechanisms changing from the mixed failure to the dimple failure; with the increase of the strain rate, the equivalent strain to fracture decreases, and the fracture pattern remains the same. The Johnson-Cook constitution and the modified Johnson-Cook fracture criterion can be used to fit the experimental results under quasi-static and dynamic tension states and predict the cup-cone fracture characteristics of different specimens.
2017, 37(6): 1017-1022.
doi: 10.11883/1001-1455(2017)06-1017-06
Abstract:
The present study investigates the growth and variation of the amplification effect in the propagation of the blasting vibration velocity in step topography. The results indicate that the blast vibration elevation amplification effect on a single step occurs at a certain distance and elevation; the peak particle velocity magnification of the top of the slope doesn't increase monotonously with the increase of the elevation; and the magnification decreases when the elevation exceeds a certain critical value. The elevation exerts an effect of both amplification and attenuation on the blasting vibration velocity. According to the data analysis of the numerical simulation and the field experiment, a model of the blasting vibration velocity prediction on step topography was presented, providing reference for the research of blasting seismic wave propagation law in similar slope projects.
The present study investigates the growth and variation of the amplification effect in the propagation of the blasting vibration velocity in step topography. The results indicate that the blast vibration elevation amplification effect on a single step occurs at a certain distance and elevation; the peak particle velocity magnification of the top of the slope doesn't increase monotonously with the increase of the elevation; and the magnification decreases when the elevation exceeds a certain critical value. The elevation exerts an effect of both amplification and attenuation on the blasting vibration velocity. According to the data analysis of the numerical simulation and the field experiment, a model of the blasting vibration velocity prediction on step topography was presented, providing reference for the research of blasting seismic wave propagation law in similar slope projects.
2017, 37(6): 1023-1030.
doi: 10.11883/1001-1455(2017)06-1023-08
Abstract:
In this study the transfer functions of the mechanical quantities (i.e. the particle velocity, the particle displacement, the stress and the strain, etc.) at different propagation distances were analytically presented based on the solutions of the linear viscoelastic spherical stress wave in the Laplace domain, The propagating characteristics of the frequency response function for the particle velocity were examined with the standard linear solid model taken as an example. The results reveal that the high-frequency response of the frequency response function for the particle velocity in viscoelastic medium is less than that of the low-frequency response with the increase of the propagation distance; in an ideal elastic medium, however, it is always greater than that of the low-frequency response. With the cavity explosion with the elastic radius of 0.025 m taken as an example, the evolution of the wave form of the particle velocity was calculated using the numerical method of the inverse Laplace transform. The results reveal that the attenuation curve of the peak value for the particle velocity in viscoelastic medium falls in between the attenuation curve of the the peak value for the particle velocity in an ideal elastic medium and the attenuation curve of the amplitude of the strong discontinuity for the particle velocity in viscoelastic medium.
In this study the transfer functions of the mechanical quantities (i.e. the particle velocity, the particle displacement, the stress and the strain, etc.) at different propagation distances were analytically presented based on the solutions of the linear viscoelastic spherical stress wave in the Laplace domain, The propagating characteristics of the frequency response function for the particle velocity were examined with the standard linear solid model taken as an example. The results reveal that the high-frequency response of the frequency response function for the particle velocity in viscoelastic medium is less than that of the low-frequency response with the increase of the propagation distance; in an ideal elastic medium, however, it is always greater than that of the low-frequency response. With the cavity explosion with the elastic radius of 0.025 m taken as an example, the evolution of the wave form of the particle velocity was calculated using the numerical method of the inverse Laplace transform. The results reveal that the attenuation curve of the peak value for the particle velocity in viscoelastic medium falls in between the attenuation curve of the the peak value for the particle velocity in an ideal elastic medium and the attenuation curve of the amplitude of the strong discontinuity for the particle velocity in viscoelastic medium.
2017, 37(6): 1031-1038.
doi: 10.11883/1001-1455(2017)06-1031-08
Abstract:
In the present work, to address the premature explosion for the detonating network, we designed a new type of irreversible detonation explosive diode and studied the mechanism and limiting factors about the explosive diode in transmitting the positive detonation and stopping the backward detonation, using the calculation and experiments of the symmetrical charge structure. The results show that the new type of explosive diode can achieve this aim and that the maximum amount of the firing charge and the crucial length of the delay elements from the theoretical calculation are fairly consistent with those from the experiments.
In the present work, to address the premature explosion for the detonating network, we designed a new type of irreversible detonation explosive diode and studied the mechanism and limiting factors about the explosive diode in transmitting the positive detonation and stopping the backward detonation, using the calculation and experiments of the symmetrical charge structure. The results show that the new type of explosive diode can achieve this aim and that the maximum amount of the firing charge and the crucial length of the delay elements from the theoretical calculation are fairly consistent with those from the experiments.
2017, 37(6): 1039-1045.
doi: 10.11883/1001-1455(2017)06-1039-07
Abstract:
To address the issue of the increase of the fragment velocity of an eccentric initiation warhead, we put forward the view that this increase was caused by the Mach overpressure formed by the detonation wave collision. We used the AUTODYN software to simulate the whole explosion process of the eccentric initiation warhead, from the radial expansion of the shell to the formation of the surface cracks, and eventually the formation of the fragments. We then compared the simulation result of the fragment velocity with the test data and found that they were in good agreement. Further we combined the simplified Whitham method with the Gurney equation to obtain the calculation method of the directional fragment velocity and directional area of the eccentric initiation warhead. We studied the selection criteria for the number of the initiation spot on the premise of maintaining the fragment velocity. The results show that through the multi-spot eccentric initiation, the velocity of the directional fragment increases by about 34%, and the directional area range is approximately 30°; the selection criteria of the number of initiation spot is associated with the shell length and the charge diameter. Our study can provide a reference for the engineering application of multi-spot initiation eccentric warhead.
To address the issue of the increase of the fragment velocity of an eccentric initiation warhead, we put forward the view that this increase was caused by the Mach overpressure formed by the detonation wave collision. We used the AUTODYN software to simulate the whole explosion process of the eccentric initiation warhead, from the radial expansion of the shell to the formation of the surface cracks, and eventually the formation of the fragments. We then compared the simulation result of the fragment velocity with the test data and found that they were in good agreement. Further we combined the simplified Whitham method with the Gurney equation to obtain the calculation method of the directional fragment velocity and directional area of the eccentric initiation warhead. We studied the selection criteria for the number of the initiation spot on the premise of maintaining the fragment velocity. The results show that through the multi-spot eccentric initiation, the velocity of the directional fragment increases by about 34%, and the directional area range is approximately 30°; the selection criteria of the number of initiation spot is associated with the shell length and the charge diameter. Our study can provide a reference for the engineering application of multi-spot initiation eccentric warhead.
2017, 37(6): 1046-1050.
doi: 10.11883/1001-1455(2017)06-1046-05
Abstract:
The mechanical properties of polyetrafluoroethylene (PTFE), which is being used increasingly in diverse applications owing to its many attractive properties, are important for applications involving either high-velocity impact or blast loading at very high strain rates (of the order of 106 s-1). In this work, for high strain rates of 105~106 s-1, the PTFE dynamic pressure experiment was conducted using the pressure-shear plate-impact (PSPI) facility in which a tungsten-carbide (WC) flyer impacted a target assembly consisting of a thin PTFE plate sandwiched between two hard (elastic) WC plates. The velocity at the free surface of the target assembly was measured using the laser interferometry, an effective method was adopted to analyze the experimental results to obtain the values of the stress and strain at four points, and the stress strain relationship was fitted. The investigation has significance for the analysis of the strength and impact crushing performance of PTFE/metal reactive fragments.
The mechanical properties of polyetrafluoroethylene (PTFE), which is being used increasingly in diverse applications owing to its many attractive properties, are important for applications involving either high-velocity impact or blast loading at very high strain rates (of the order of 106 s-1). In this work, for high strain rates of 105~106 s-1, the PTFE dynamic pressure experiment was conducted using the pressure-shear plate-impact (PSPI) facility in which a tungsten-carbide (WC) flyer impacted a target assembly consisting of a thin PTFE plate sandwiched between two hard (elastic) WC plates. The velocity at the free surface of the target assembly was measured using the laser interferometry, an effective method was adopted to analyze the experimental results to obtain the values of the stress and strain at four points, and the stress strain relationship was fitted. The investigation has significance for the analysis of the strength and impact crushing performance of PTFE/metal reactive fragments.
Dynamic correction and compensation method about the measuring curve of shockwave reflected pressure
2017, 37(6): 1051-1056.
doi: 10.11883/1001-1455(2017)06-1051-06
Abstract:
In the present work, to obtain the accurate measuring curve of explosive shockwave reflected pressure, we analyzed the three factors that influence the peak value, i.e. the band width of the pressure test system, the pressure test method, and the length of the signal transfer wire, adjusted the dynamic calibration on the shockwave pressure measuring system using the shock tube, and obtained the dynamic characteristics of the system using the ideal method of differential. With the improved version of the levy method, the parameter model about the dynamic characteristics was built. The Butterworth filter was designed as the system after the compensation for the calculation of the dynamic compensation tache. This method can expand the work frequency segment of the pressure test system and reduce the amplitude of the inherent frequency point so that the shock wave reflected pressure curve was rectified. It was found that this rectification and compensation method can correct the peak value of the shockwave reflected pressure and reduce the error from the dynamic characteristics of the shockwave pressure measuring system. This study can significantly raise the peak value accuracy of the shockwave reflected pressure and provide technical support for weapon damage assessment.
In the present work, to obtain the accurate measuring curve of explosive shockwave reflected pressure, we analyzed the three factors that influence the peak value, i.e. the band width of the pressure test system, the pressure test method, and the length of the signal transfer wire, adjusted the dynamic calibration on the shockwave pressure measuring system using the shock tube, and obtained the dynamic characteristics of the system using the ideal method of differential. With the improved version of the levy method, the parameter model about the dynamic characteristics was built. The Butterworth filter was designed as the system after the compensation for the calculation of the dynamic compensation tache. This method can expand the work frequency segment of the pressure test system and reduce the amplitude of the inherent frequency point so that the shock wave reflected pressure curve was rectified. It was found that this rectification and compensation method can correct the peak value of the shockwave reflected pressure and reduce the error from the dynamic characteristics of the shockwave pressure measuring system. This study can significantly raise the peak value accuracy of the shockwave reflected pressure and provide technical support for weapon damage assessment.
2017, 37(6): 1057-1064.
doi: 10.11883/1001-1455(2017)06-1057-08
Abstract:
In order to improve the design and safety assessment of the reliability of blast-resistant structures, we studied the simplified calculation of the shock wave loads caused by HE explosions in straight tunnel based on the theoretical calculation and numerical simulation. Firstly, the differences among existing calculation methods of in-tunnel shock wave loads and their results were evaluated quantitatively in detail and the effects of such differences on structure responses were discussed. Then the design loads on the blast door in a tunnel was studied based on the model test and numerical analysis. The results show that it is important to take into account the coupling effects of the structure response when developing simplified calculation methods for in-tunnel explosion shock wave loads. The existing simplified methods generally disregard such effects and differ from one another significantly, which leads to much more uncertainty in both design and assessment. For close range explosion, the design loads on the door can be taken from pressure at the point on the midline and 1/4 door-width away from the door-side, or from the average pressure on the door, which is reasonably acceptable in a wide range of structure frequencies. The present work can provide a reliable method for protection design of in-tunnel structures.
In order to improve the design and safety assessment of the reliability of blast-resistant structures, we studied the simplified calculation of the shock wave loads caused by HE explosions in straight tunnel based on the theoretical calculation and numerical simulation. Firstly, the differences among existing calculation methods of in-tunnel shock wave loads and their results were evaluated quantitatively in detail and the effects of such differences on structure responses were discussed. Then the design loads on the blast door in a tunnel was studied based on the model test and numerical analysis. The results show that it is important to take into account the coupling effects of the structure response when developing simplified calculation methods for in-tunnel explosion shock wave loads. The existing simplified methods generally disregard such effects and differ from one another significantly, which leads to much more uncertainty in both design and assessment. For close range explosion, the design loads on the door can be taken from pressure at the point on the midline and 1/4 door-width away from the door-side, or from the average pressure on the door, which is reasonably acceptable in a wide range of structure frequencies. The present work can provide a reliable method for protection design of in-tunnel structures.
2017, 37(6): 1065-1071.
doi: 10.11883/1001-1455(2017)06-1065-07
Abstract:
Internal short-circuit arcing explosion in a medium-voltage (MV) switchgear poses a serious hazard to the safety of equipments, buildings and personnel. In the present work, to find out an appropriate method to calculate the pressure effect resulting from the internal arcing explosion, we analyzed the energy balance mechanism of the internal arcing in the switchgear, presented an indirect coupling analysis method based on CFD through the analysis of the thermal-mechanical effect of the arcing process, and verified the method by the actual arcing in a closed container. The results show that the relative error of the average pressure rise between measurement and calculation is about 2%. The arc size has less effect on the pressure rise. In the closed container, the pressure rise approximately increases linearly with the increase of the arc energy. The installation of a negative pressure room can reduce the pressure in the arcing room 60%, thereby effectively restraining the pressure rise in the switchgear caused by the internal short-circuit arcing explosion.
Internal short-circuit arcing explosion in a medium-voltage (MV) switchgear poses a serious hazard to the safety of equipments, buildings and personnel. In the present work, to find out an appropriate method to calculate the pressure effect resulting from the internal arcing explosion, we analyzed the energy balance mechanism of the internal arcing in the switchgear, presented an indirect coupling analysis method based on CFD through the analysis of the thermal-mechanical effect of the arcing process, and verified the method by the actual arcing in a closed container. The results show that the relative error of the average pressure rise between measurement and calculation is about 2%. The arc size has less effect on the pressure rise. In the closed container, the pressure rise approximately increases linearly with the increase of the arc energy. The installation of a negative pressure room can reduce the pressure in the arcing room 60%, thereby effectively restraining the pressure rise in the switchgear caused by the internal short-circuit arcing explosion.
2017, 37(6): 1072-1079.
doi: 10.11883/1001-1455(2017)06-1072-08
Abstract:
In the present study, we designed the electromagnetic and explosive driving expanding ring/cylinder experiments and investigated the expanding fracture characteristics of oxygen-free high-conductivity copper (OFHC) in consideration of the conception of the reduction of area, the local fracture strain and the average fracture strain. We used a high speed camera to record the fracture process and obtain the fracture strain of the copper cylinder and the Doppler pins system (DPS) to obtain the radial velocity of the specimen in order to achieve the strain rate of the loading. We verified the local fracture strain and the fracture mode by analyzing the soft-recovered fragments of the expanding ring and the cylinder. Based on the experimental results, we found that the average fracture strain and the reduction of the area increases as does the strain rate. Moreover, the fracture mode transition may occur at the strain rate of about 1.0×104 s-1, and the reduction of the area may increase by an order of magnitude, i.e. from the order of 100 to that of 103, and the local fracture strain exhibits an obvious subarea.
In the present study, we designed the electromagnetic and explosive driving expanding ring/cylinder experiments and investigated the expanding fracture characteristics of oxygen-free high-conductivity copper (OFHC) in consideration of the conception of the reduction of area, the local fracture strain and the average fracture strain. We used a high speed camera to record the fracture process and obtain the fracture strain of the copper cylinder and the Doppler pins system (DPS) to obtain the radial velocity of the specimen in order to achieve the strain rate of the loading. We verified the local fracture strain and the fracture mode by analyzing the soft-recovered fragments of the expanding ring and the cylinder. Based on the experimental results, we found that the average fracture strain and the reduction of the area increases as does the strain rate. Moreover, the fracture mode transition may occur at the strain rate of about 1.0×104 s-1, and the reduction of the area may increase by an order of magnitude, i.e. from the order of 100 to that of 103, and the local fracture strain exhibits an obvious subarea.
2017, 37(6): 1080-1086.
doi: 10.11883/1001-1455(2017)06-1080-07
Abstract:
In this work, we investigated a study of the mechanism governing the internal blast in a warship cabin and the technique for preventing it. We developed a multi-cabin structure and carried out experiments with/without water were on the cabin to record and compare such data as the blast process, the peak pressure, the specific impulse and the quasi-static pressure. The results showed that (1) water could obviously reduce the peak pressure, the specific impulse and the quasi-static pressure, that (2) within a certain range, the greater amount of TNT, the more obvious the attenuation, and that (3) water could constrain the afterburning phenomena and TNT reaction, thereby affecting the formation of the quasi-static pressure.
In this work, we investigated a study of the mechanism governing the internal blast in a warship cabin and the technique for preventing it. We developed a multi-cabin structure and carried out experiments with/without water were on the cabin to record and compare such data as the blast process, the peak pressure, the specific impulse and the quasi-static pressure. The results showed that (1) water could obviously reduce the peak pressure, the specific impulse and the quasi-static pressure, that (2) within a certain range, the greater amount of TNT, the more obvious the attenuation, and that (3) water could constrain the afterburning phenomena and TNT reaction, thereby affecting the formation of the quasi-static pressure.
2017, 37(6): 1087-1092.
doi: 10.11883/1001-1455(2017)06-1087-06
Abstract:
In this work we combined the powerful computing capabilities of Matlab programs combined with VB friendly interface and developed the forecast system for blasting vibrational velocity peak using ActiveX automation technologies and BP neural network algorithm. The forecast system can select as an input parameter various factors affecting an engineering project's blasting vibration. The actual application of the system in the construction of the underground cut tunnel in the Beijing-Changping Line shows that this system is simple and convenient to use in practical engineering, accepted for its high precision of prediction, good application effect and friendly human-computer interaction interface.
In this work we combined the powerful computing capabilities of Matlab programs combined with VB friendly interface and developed the forecast system for blasting vibrational velocity peak using ActiveX automation technologies and BP neural network algorithm. The forecast system can select as an input parameter various factors affecting an engineering project's blasting vibration. The actual application of the system in the construction of the underground cut tunnel in the Beijing-Changping Line shows that this system is simple and convenient to use in practical engineering, accepted for its high precision of prediction, good application effect and friendly human-computer interaction interface.
2017, 37(6): 1093-1100.
doi: 10.11883/1001-1455(2017)06-1093-08
Abstract:
In this study a theoretical model was established to predict the interface defeat/penetration transition velocity of a ceramic armor impacted by a long-rod projectile. Predications of the transition velocity were obtained by measuring the stress inside the target and then applying it in turn to the conical crack and the wing crack propagation theory. After that, a theoretical model consisting of the conical and the wing crack propagation theory was presented. The results show that the theoretical model can reasonably well describe the interface defeat/penetration transition process. The interface defeat/penetration transition velocity calculated by the theoretical model agrees well with the experimental results from the previously published literature. The conical crack propagation dominates the interface defeat/penetration transition process when the projectile radius is small, while the wing crack dominates the transition when the projectile radius is large.
In this study a theoretical model was established to predict the interface defeat/penetration transition velocity of a ceramic armor impacted by a long-rod projectile. Predications of the transition velocity were obtained by measuring the stress inside the target and then applying it in turn to the conical crack and the wing crack propagation theory. After that, a theoretical model consisting of the conical and the wing crack propagation theory was presented. The results show that the theoretical model can reasonably well describe the interface defeat/penetration transition process. The interface defeat/penetration transition velocity calculated by the theoretical model agrees well with the experimental results from the previously published literature. The conical crack propagation dominates the interface defeat/penetration transition process when the projectile radius is small, while the wing crack dominates the transition when the projectile radius is large.
2017, 37(6): 1101-1106.
doi: 10.11883/1001-1455(2017)06-1101-06
Abstract:
Based on the virtual origin theory, the shock wave reflection theory and the jet interference theory, the theoretical model for the jet penetrating a liquid-filled unit cell structure was improved and perfected in consideration of the liquid's spray and radial convergence. The exact expression of the disturbance velocity range of the jet, the expression of the liquid's spray velocity and the expression of the liquid's flow were derived. The theoretical mode of this paper was confirmed by in the comparison of the theoretical and the experimental results of the disturbance velocity range of the jet. The results showed that the liquid's spray and radial convergence exert influence on the shaped charge jet's stability, leading to the jet's necking and fracture, thereby reducing the jet's residual velocity and residual penetration ability.
Based on the virtual origin theory, the shock wave reflection theory and the jet interference theory, the theoretical model for the jet penetrating a liquid-filled unit cell structure was improved and perfected in consideration of the liquid's spray and radial convergence. The exact expression of the disturbance velocity range of the jet, the expression of the liquid's spray velocity and the expression of the liquid's flow were derived. The theoretical mode of this paper was confirmed by in the comparison of the theoretical and the experimental results of the disturbance velocity range of the jet. The results showed that the liquid's spray and radial convergence exert influence on the shaped charge jet's stability, leading to the jet's necking and fracture, thereby reducing the jet's residual velocity and residual penetration ability.
2017, 37(6): 1107-1112.
doi: 10.11883/1001-1455(2017)06-1107-06
Abstract:
In this study we carried out an static overall tensile experiment at room temperature and a transient blast experiment under ultra high pressure to investigate the structural strength of glass fiber reinforced (GFR) composite cartridge of CTA gun with transient impulse under high temperature and pressure. The fracture surfaces of the specimens were cut from the tensile/transient ultra high pressure failure samples, and the fracture morphology was observed under the scanning electron micro scope. The results show that the main failure modes of GFR composites are matrix failure and fiber pulling-out when the uniaxial overall tensile fracture occurs at room temperature with the intersection between the GFR composites section and the axis close to 45°; the main failure mode of the specimen under transient ultra high pressure is the brittle fracture of the fiber and, due to the a portion of substrate's carbonization resulting from the high temperature heat produced by the ignited gun powder, the fiber matrix interface's binding force is reduced and a few fibers either melt or soften, becoming attached to the fractured surface, thereby attenuating part of the softened fibers due to the transient super high pressure.
In this study we carried out an static overall tensile experiment at room temperature and a transient blast experiment under ultra high pressure to investigate the structural strength of glass fiber reinforced (GFR) composite cartridge of CTA gun with transient impulse under high temperature and pressure. The fracture surfaces of the specimens were cut from the tensile/transient ultra high pressure failure samples, and the fracture morphology was observed under the scanning electron micro scope. The results show that the main failure modes of GFR composites are matrix failure and fiber pulling-out when the uniaxial overall tensile fracture occurs at room temperature with the intersection between the GFR composites section and the axis close to 45°; the main failure mode of the specimen under transient ultra high pressure is the brittle fracture of the fiber and, due to the a portion of substrate's carbonization resulting from the high temperature heat produced by the ignited gun powder, the fiber matrix interface's binding force is reduced and a few fibers either melt or soften, becoming attached to the fractured surface, thereby attenuating part of the softened fibers due to the transient super high pressure.
2017, 37(6): 946-951.
doi: 10.11883/1001-1455(2017)06-0946-06
Abstract:
In this work we investigated the influence of the constrained layer, composed of metal aluminum and polyurethane foam, on the expanding deformation of a metal cylindrical shell using numerical simulation, obtained the velocity and displacement profiles for 45 steel and aluminum affected by shock wave, and compared its simulated dynamic behaviors under the influence with those from the corresponding experiments performed using a high-speed framing camera and medium-energy X-ray photography and found them in good agreement. The findings obtained here provide a quantitative understanding of the constrained layer in terms of its influence on the expanding deformation of the metal cylindrical shell subjected to the high explosive loading.
In this work we investigated the influence of the constrained layer, composed of metal aluminum and polyurethane foam, on the expanding deformation of a metal cylindrical shell using numerical simulation, obtained the velocity and displacement profiles for 45 steel and aluminum affected by shock wave, and compared its simulated dynamic behaviors under the influence with those from the corresponding experiments performed using a high-speed framing camera and medium-energy X-ray photography and found them in good agreement. The findings obtained here provide a quantitative understanding of the constrained layer in terms of its influence on the expanding deformation of the metal cylindrical shell subjected to the high explosive loading.
2017, 37(6): 952-958.
doi: 10.11883/1001-1455(2017)06-0952-07
Abstract:
This paper studied the interaction mechanism between the dynamic crack and the precast static crack (horizontal angle for 90° and 150°) under the action of explosion stress and the dynamic behavior of crack propagation using the digital laser dynamic caustics test system. The results show that before the dynamic crack and static crack coalescence, the caustics speckles will occur at both ends of the static crack, while after the dynamic crack and static crack coalescence, the static crack extends in the horizontal direction with a speed lower than that of both the dynamic crack and the crack expansion without static crack; that when the static crack exists, the overall length of the dynamic crack expansion is reduced, the crack initiation time is shortened, the expansion speed is not affected by the static crack, and the stress intensity factor of the crack is greater than that of the static crack; and that as the horizontal angle of the static crack increases, the deflection distance of the dynamic crack increases along the horizontal direction when the dynamic crack and the static crack become coalescenced, end point B of the static crack expands towards the opposite direction, ending in "mutual occlusion" with end point C of the dynamic crack as the displacement and velocity of the latter's expansion increases.
This paper studied the interaction mechanism between the dynamic crack and the precast static crack (horizontal angle for 90° and 150°) under the action of explosion stress and the dynamic behavior of crack propagation using the digital laser dynamic caustics test system. The results show that before the dynamic crack and static crack coalescence, the caustics speckles will occur at both ends of the static crack, while after the dynamic crack and static crack coalescence, the static crack extends in the horizontal direction with a speed lower than that of both the dynamic crack and the crack expansion without static crack; that when the static crack exists, the overall length of the dynamic crack expansion is reduced, the crack initiation time is shortened, the expansion speed is not affected by the static crack, and the stress intensity factor of the crack is greater than that of the static crack; and that as the horizontal angle of the static crack increases, the deflection distance of the dynamic crack increases along the horizontal direction when the dynamic crack and the static crack become coalescenced, end point B of the static crack expands towards the opposite direction, ending in "mutual occlusion" with end point C of the dynamic crack as the displacement and velocity of the latter's expansion increases.
2017, 37(6): 959-965.
doi: 10.11883/1001-1455(2017)06-0959-07
Abstract:
In this study we carried out ballistic tests to explore the residual characteristics of moderately thick water-backed steel plates penetrated by high-velocity fragments. Damage modes of projectiles as well as targets were analyzed. We compared the vertical and inclined water-backed steel plates penetrated by fragments in terms of instantaneous fragment velocities, moving trajectories and the pressure characteristics of induced incipient shockwaves. The results show that serious mushrooming deformation occur on the noses of the fragments during high-velocity penetration, and the dynamic supporting effect of water in the back of the steel plate should be considered in its examination. Damage modes of the water backed steel plates are mainly shear plugging, together with adiabatic shear effect available on the distal side of the perforation holes. In the earlier stage after the fragment perforating the water-backed steel plates, cavities and jets are produced. The cavity size and the jet intensity are both related to the initial velocities of the fragments entering the water, whereas both the cavity shape and the jet direction are affected by the inclined angle of the water-backed steel plates. After the perforation of the water-backed steelplates, the moving trajectories of the fragments will deflect, and the deflection direction is related to the initial velocities. Due to the dynamic supporting as well as the kinetic energy dissipation effects of water, the kinetic energy loss of the fragment perforating water-backed steel plates is greater than that perforating air-backed steel plates. The influence of the rarefaction wave on the pressure characteristics of incipient shock waves should be considered. Under the condition of the same initial fragment velocity, penetration of the vertical water-backed steel plates result in incipient shock waves with higher peak pressures than those resulting from the penetration of the inclined water-backed steel plates.
In this study we carried out ballistic tests to explore the residual characteristics of moderately thick water-backed steel plates penetrated by high-velocity fragments. Damage modes of projectiles as well as targets were analyzed. We compared the vertical and inclined water-backed steel plates penetrated by fragments in terms of instantaneous fragment velocities, moving trajectories and the pressure characteristics of induced incipient shockwaves. The results show that serious mushrooming deformation occur on the noses of the fragments during high-velocity penetration, and the dynamic supporting effect of water in the back of the steel plate should be considered in its examination. Damage modes of the water backed steel plates are mainly shear plugging, together with adiabatic shear effect available on the distal side of the perforation holes. In the earlier stage after the fragment perforating the water-backed steel plates, cavities and jets are produced. The cavity size and the jet intensity are both related to the initial velocities of the fragments entering the water, whereas both the cavity shape and the jet direction are affected by the inclined angle of the water-backed steel plates. After the perforation of the water-backed steelplates, the moving trajectories of the fragments will deflect, and the deflection direction is related to the initial velocities. Due to the dynamic supporting as well as the kinetic energy dissipation effects of water, the kinetic energy loss of the fragment perforating water-backed steel plates is greater than that perforating air-backed steel plates. The influence of the rarefaction wave on the pressure characteristics of incipient shock waves should be considered. Under the condition of the same initial fragment velocity, penetration of the vertical water-backed steel plates result in incipient shock waves with higher peak pressures than those resulting from the penetration of the inclined water-backed steel plates.
2017, 37(6): 966-975.
doi: 10.11883/1001-1455(2017)06-0966-10
Abstract:
In this work, in view of the widely understood idea that topography and geological conditions are usually complicated and have a critical influence on the level of blast induced ground vibrations, we analyzed the effect of topography on the path through which seismic waves travel, introduced two concepts, the equivalent path and the equivalent distance, and established an equation for determining the surface peak particle velocity, taking into account of the effects of the maximum explosive charge quantity of a single initiation period, the explosion heat of the explosive product used, the acoustic impedance of the rock, and the integrity coefficient of the rock mass. A series of field seismic monitoring tests were carried out to determine the reliability of the equation. The result show that this equation can be used to describe the relationship between the peak particle velocity and the equivalent distance, and be applied under actual field topographical and geological conditions with a much higher accuracy than that of the Sardovsky's equation, proving the reliability of the equivalent distance based equation describing the attenuation basic patterns of seismic waves and possibility for use in field practice.
In this work, in view of the widely understood idea that topography and geological conditions are usually complicated and have a critical influence on the level of blast induced ground vibrations, we analyzed the effect of topography on the path through which seismic waves travel, introduced two concepts, the equivalent path and the equivalent distance, and established an equation for determining the surface peak particle velocity, taking into account of the effects of the maximum explosive charge quantity of a single initiation period, the explosion heat of the explosive product used, the acoustic impedance of the rock, and the integrity coefficient of the rock mass. A series of field seismic monitoring tests were carried out to determine the reliability of the equation. The result show that this equation can be used to describe the relationship between the peak particle velocity and the equivalent distance, and be applied under actual field topographical and geological conditions with a much higher accuracy than that of the Sardovsky's equation, proving the reliability of the equivalent distance based equation describing the attenuation basic patterns of seismic waves and possibility for use in field practice.
2017, 37(6): 976-981.
doi: 10.11883/1001-1455(2017)06-0976-06
Abstract:
In the present work we developed a strain wire measurement technique that can be used to measure the dynamic deformation process of cylindrical explosion vessels. The strain wires, compactly fixed along the circumference of the explosion vessels, extended synchronously when the vessels deformed due to the wires' good ductility. Coupled to appropriate circuitry, the resistance profiles of the alloy wires were measured to determine the dynamic deformation process of the explosion vessels. A 120 g TNT spherical high explosive experiment was performed in a cylindrical steel shell. The circumferential deformation curve of the shell was obtained, the peak value of which exceeded by 20%. The result of the strain wires measurement accorded with both the simulation result and the deformation data from the cylindrical steel shell experiment.
In the present work we developed a strain wire measurement technique that can be used to measure the dynamic deformation process of cylindrical explosion vessels. The strain wires, compactly fixed along the circumference of the explosion vessels, extended synchronously when the vessels deformed due to the wires' good ductility. Coupled to appropriate circuitry, the resistance profiles of the alloy wires were measured to determine the dynamic deformation process of the explosion vessels. A 120 g TNT spherical high explosive experiment was performed in a cylindrical steel shell. The circumferential deformation curve of the shell was obtained, the peak value of which exceeded by 20%. The result of the strain wires measurement accorded with both the simulation result and the deformation data from the cylindrical steel shell experiment.
2017, 37(6): 982-989.
doi: 10.11883/1001-1455(2017)06-0982-08
Abstract:
In this study, we investigated the dynamic stress concentration factor of single circular inclusion shallow buried in surface softlayered half space impacted by steady SH-wave using the complex variable function method and the wave function expansion method, and obtained the analytical solution. Based on the attenuation characteristic of SH-Wave scattering and using the large-arc assumption method, we converted the problem of the layer half space linear boundary to that of the circle boundary and, by an example, analyzed the influence of different incident wave numbers and the ratios of the circular inclusion to the half space on the distribution of the dynamic stress concentration factor and on the change of the maximum dynamic stress concentration when the incident SH-wave is vertical. Numerical examples show that the "softer" the circular inclusion, the greater its wave number of circular inclusions, and the larger the dynamic stress concentration factor around the circular inclusion; the maximum dynamic stress concentration factor around circular inclusion reaches its maximum value when the number of the incident SH-wave approaches 0.35.
In this study, we investigated the dynamic stress concentration factor of single circular inclusion shallow buried in surface softlayered half space impacted by steady SH-wave using the complex variable function method and the wave function expansion method, and obtained the analytical solution. Based on the attenuation characteristic of SH-Wave scattering and using the large-arc assumption method, we converted the problem of the layer half space linear boundary to that of the circle boundary and, by an example, analyzed the influence of different incident wave numbers and the ratios of the circular inclusion to the half space on the distribution of the dynamic stress concentration factor and on the change of the maximum dynamic stress concentration when the incident SH-wave is vertical. Numerical examples show that the "softer" the circular inclusion, the greater its wave number of circular inclusions, and the larger the dynamic stress concentration factor around the circular inclusion; the maximum dynamic stress concentration factor around circular inclusion reaches its maximum value when the number of the incident SH-wave approaches 0.35.
2017, 37(6): 990-1000.
doi: 10.11883/1001-1455(2017)06-0990-11
Abstract:
Based on the kinetic theory of granular flow (pseudo-fluid model), a new Smoothed Particle Hydrodynamics (SPH) algorithm suited for hyper velocity collision was presented in this paper. The damaged debris of the hyper velocity impact was equated with the pseudo-fluid and the effects of the debris' interaction and the effects of the gas on the formation process of the debris cloud were investigated. The new SPH algorithm was employed to simulate the 3D hyper velocity impact of an alloy projectile on thin target plates, and the numerical results of crater diameters, the structure and morphology characteristics of the debris cloud and the core debris cloud's shape and distribution were in good agreement with the experimental results. Compared with the simulations of the standard SPH and ASPH, the simulation of the new algorithm is more accurate in the core debris cloud's characteristics. Meanwhile, the hyper velocity impact of the Whipple shield problem was also simulated at different impact velocities. It was found that the crater diameters and the damage characteristics of the rear walls agree well with the experimental results, and that the simulation results are consistent with the typical ballistic limit curve of a Whipple shielding structure.
Based on the kinetic theory of granular flow (pseudo-fluid model), a new Smoothed Particle Hydrodynamics (SPH) algorithm suited for hyper velocity collision was presented in this paper. The damaged debris of the hyper velocity impact was equated with the pseudo-fluid and the effects of the debris' interaction and the effects of the gas on the formation process of the debris cloud were investigated. The new SPH algorithm was employed to simulate the 3D hyper velocity impact of an alloy projectile on thin target plates, and the numerical results of crater diameters, the structure and morphology characteristics of the debris cloud and the core debris cloud's shape and distribution were in good agreement with the experimental results. Compared with the simulations of the standard SPH and ASPH, the simulation of the new algorithm is more accurate in the core debris cloud's characteristics. Meanwhile, the hyper velocity impact of the Whipple shield problem was also simulated at different impact velocities. It was found that the crater diameters and the damage characteristics of the rear walls agree well with the experimental results, and that the simulation results are consistent with the typical ballistic limit curve of a Whipple shielding structure.
